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LT3791: lift pressure 100 w LED driver solution

B2b website company LT3791 is four switch booster – synchronous buck LED drive controller, can make the VIN above, below or equal to the VOUT, efficiency is as high as 98.5%, the input voltage of 4.7 V ~ 60 V, output voltage of 0 V ~ 60 V, the LED current accuracy + / – 6%, true color PWM dimming and simulation, each IC input power is 100 w and 100 w. Mainly used in automobile headlights/running lights and general lighting.

Its continuous constant frequency and force constant current mode architecture, make its can be adjusted, or synchronous frequency of 200 KHZ to 700 KHZ. On the top of the step-down or booster operation without MOSFET switching cycle. This device is 60 v input, 60 v output. Seamless transition between and work area, make LT3791 LED driver in the automotive, industrial, battery power supply system is relatively ideal choice.

LT3791 when restart or atresia with input current monitor, monitor, the LED current and the LED open circuit or short circuit protection.

Figure 1 LT3791 block diagram

LT3791 main features

Single inductor, 4 switch architecture allows VIN above, below or equal to VOUT

• synchronous switch: efficiency is as high as 98.5%

• 4.7 V ~ 60 V wide VIN range:

VOUT, a wide range: 0 v ~ 60 v (52 v LED)

• LED current accuracy of + / – 6% : 0 v or less VLED < 52 v

• True Color PWM dimming and simulation

• LED current monitor output and input current regulation

• no Top MOSFET refresh when buck or booster

During shutdown, VIN and VOUT disconnect

• open circuit or short circuit LED failure protection

• each IC 100 w or higher

• take naked TSSOP 38 pin pad

LT3791 application

• car headlights/traffic lights

• general lighting

Figure 2 LT3791 efficiency is 98% (25 v2a) liters – 50 w step-down LED drive circuit diagram

Figure 3 LT3791 efficiency 98.5% 100 w (33.3 V3A) – buck LED drive circuit diagram

Figure 4 DC1666A demo board circuit diagram

Demo board DC1666A

DC1666A demonstration is a synchronous circuit switch buck – boost type LED drive controller. Its input voltage of 4.7 V ~ 60 V, top drive, 25 V 2 a of the LED. DC1666A has LED series PWM and analog dimming function. When the LED string is moving, its OPENLED logo display; When the output short circuit to GND, SHORTLED logo according to it. In both cases, the IC is keeping control, and has good protection.

DC1666A high efficiency, its switching frequency is 300 KHZ, with continuous conduction mode (CCM). Its synchronous four switch topology, in regulating constant 50 w LED output current (step-up and step-down), when efficiency is as high as 98%. The circuit can change, is used for more than 100 w LED applications. An optional SYNC terminal to an external clock synchronization and CLKOUT terminals, and provides another converter (LT3791) and internal clock synchronization of resources. Three detection resistor provides a constant output current control and monitoring switch, peak current control and DC input current limit and monitor. Its ISMON and IVINMON output can tell the user how much current flows through the output and input of the sensor resistance. Small ceramic input and output capacitors, to save space and cost. LED open-circuit overvoltage protection IC constant voltage regulating loop is adopted, in order to limit the output (about 28.3 V, such as the LED string is open). For low input voltage operation, when the input voltage below 6.5 V, the CTRL pin voltage is reduced, and reduce the LED brightness and limit switch current peak, to limit the size of the inductor and the switch. When VIN dropped to below 4.7 V, the UVLO will LED to shut down. When the input to rise to higher than 57.6 V, overvoltage atresia function will switch off as protection, when VIN down to 56.2 V, reopened.

DC1666A PWM dimming is very simple, PWM dimming MOSFET using the PWM dimming input terminal to conduction and closing the LED string. For PWM dimmer than most, it is recommended to use frequency of 100 hz as PWM dimming. For PWM dimming ratio and performance of the information, you can see the application information section LT3791 data tables. Analog dimming is simple, using a simple CTRL terminal voltage source.

DC1666A can make changes, to transform the power board to a higher or lower, or to an LED driver to a constant voltage regulator and battery charger.

LT3791 data table is given a complete, operation and application of information description. Data table must be used and manual along with reading, in order to understand DC1666A circuit. LT3791 assembly in a 38 pin plastic TSSOP packages, and have heat enhancement mat. Correct PCB layout on the thermal performance is essential.

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Small power LED drive power supply topology technology solutions

As countries around the world is becoming more and more attention to energy conservation and emissions reduction requirements, LED as a new light source with high efficiency and energy saving has become more and more widely used. Here mainly introduce about a small period of 1 to 30 w power LED driver application between the isolation technology is introduced.

A resistor capacitor step-down:

1. Resistance capacitance step-down principle and application:

Capacitance step-down current limiting is actually using the capacitive reactance, actually have a limiting current and capacitor and dynamically allocated capacitors and load voltage on both ends.

2. When using capacitance step-down, should pay attention to the following:

According to the size of load current and the working frequency of alternating current (ac) to select the appropriate capacitor, rather than according to the load voltage and power, current limiting capacitance must adopt non-polar capacitors, electrolytic capacitors will not be used. And condenser pressure shall be above 400 v, the ideal metal for polypropylene film capacitors. Capacitance step-down cannot be used for high power conditions, generally used for low power applications, under five w capacitance buck is not suitable for dynamic loading conditions, capacitance step-down discomfort might sex and inductive load, the power LED drive applications for single voltage application.

3. The basic circuit of resistance capacitance step-down type of easy power supply such as (figure 1)

In figure 1.

For buck capacitor C1, D1, 2, 3, 4 for the bridge rectifier diodes, ZD1 is zener diode, R1 to shut off the power after the charge discharge resistance of C1.

4. The device choice

Circuit design, it shall first determine a precise value for the load current, then the reference sample to choose step-down condenser capacity. Because through the buck capacitor C1 for load current Io, is actually of charging and discharging current C1 Ic. The C1 capacity, the greater the capacitive reactance Xc is smaller, the charge and discharge current is flowing through C1 is larger. When the load current Io less than the charge and discharge current of C1, excess current will flow through the voltage regulator tube, if the maximum permissible current regulator tube Idmax less than Ic – Io voltage regulator tube burned easily. In order to ensure the C1 and reliable work, the choice of pressure should be greater than twice the power supply voltage. The choice of the bleeder resistor R1 must guarantee within the prescribed time discharge C1 on the charge.

5. The actual parameter calculation method:

C1 is 0.33 u F, known is 220 v / 50 hz ac input, to calculate the maximum current circuit can supply the load.

C1 in the circuit of the capacitive reactance Xc for:

Xc = 1 / (2 PI f C) = 1 / (2 * 10-6) * 50 * 0.33 * 3.14 = 9.65 K

Through the charging current of capacitor C1 (Ic) is:

Ic = U/Xc = 220/9.65 = 22 ma.

Two linear drive circuit:

1. Typical of the circuit such as (figure 2)

In figure 2

2. The principle of work:

R3 as constant flow resistance, pressure drop using the R3 to control the switch of TL432, in using the switch to control the conduction of Q1 432 to achieve the purpose of constant current output, choose the purpose of the 432 432 benchmark for 1.21 V is used to reduce the wastage of the in R3. Current constant current value was 1.21 / R3, R1 choice selection according to the magnification of Q1.

3. The applications to note:

This circuit used in a single input voltage, output current is small current LED power driver, such as the ball bubble lamp, T tube, such as general advice under the output current 100 ma. Approximates to input and output voltage will be good, so avoid Q1 caused by the excessive pressure drop loss is too big, the efficiency is low, so the application of the LED is best used in series.

Three constant current diode drive circuit

1. Typical of the circuit such as (figure 3, figure 4)

In figure 3

Figure 4.

2. The working principle of the

Ideal of constant current source is a kind of internal resistance of infinity device, regardless of why on both ends of the voltage value, the current flows through the forever. Of course, this kind of device is impossible. Real constant current diode is equivalent to a working voltage only within a certain range, such as 25-100 – v constant for a particular value such as the current 20 ma. The equivalent circuit as shown in figure 5

Figure 5

Its internal resistance is Z, shunt capacitance is about 4-10. Pf the typical volt-ampere characteristics as shown in figure 6.

Figure 6

It at a certain voltage range with a Duan Heng flow range, in this interval, flows through the electric current is almost constant, VL for voltage value reaches the IL, IL is about 0.8 Ip.

3. The application note

Due to the constant current diode needs certain voltage vitamin k can enter the constant current, so the low power supply voltage is unable to work. Usually this vitamin k around 5-10 v, so most of the LED power is supplied by batteries is unable to work, maximum current due to the constant current diodes, power consumption is restricted, so too much current is also not appropriate. 1 w leds usually require 350 ma, for example, it is difficult to provide constant current diode, is currently more appropriate the use of occasions is the ac mains power LED lamps and lanterns USES a lot of small power LED series, that is, high voltage low current situation is the most appropriate; But due to the constant current diode pressure have a certain limit so that it can absorb the power supply voltage change is limited. Take 100 v voltage of the CRD for use in the 220 v mains supply voltage change is only limited. 220 v after the bridge rectifier its output dc voltage is about 264 v. If the utility change + 10% ~ 15% is equivalent to rectifier for 290 ~ 187 v, 103 v voltage change is now more than the withstand voltage. Because the LED nonlinear volt-ampere characteristics. So it is difficult to use formula to said Anyhow when mains voltage to reduce the LED current can follow mains voltage of the lower and lower. Its brightness will follow to change. Typical application circuit center 3 for the typical application circuit, figure 4 for the added resistance capacitance step-down applications circuits in order to cope with the low voltage output.

Four USES unipolar the Buck PFC circuit

With current regulations and requirements of energy efficiency, the application and for the LED high PF, and adapt to the request of the full voltage range can be reliable work, and the development toward miniaturization, so before the valley type PFC circuit is also need to add two high-voltage capacitance due to the size limit is not suitable for application. Is any guide, many manufacturers at home and abroad are introduced to adapt to the ball bubble lamp and T tube not drive solution isolation power supply applications, such as the following with tong jia LD7832 as a typical introduction of science and technology.

1. Introduce LD7832

LD7832 is an application in the Buck circuit USES the TM mode control in high PF value LED driver control chip, the application of peripheral components less maximum limit to reduce the PCB size, complete protection function, meet the requirements of the function test and reliability test, design and debugging is quite simple, the maximum to meet customer demand rapid design online production and meet the requirements of laws and regulations, for the ball bubble lamp below 30 w, T tube products such as application, in order to meet the needs of different, LD7832 with external MOS and MOS (2 a) different versions to choose from.

2. Features a built-in 600 v high voltage start-up circuit

High PFC controller function

Efficient transition mode control

Low cost design application peripheral parts at least

Current adjustment precision is high

Wide range UVLO (17 v drive, 8 v closed)

The Vcc overvoltage protection function

The ZCD under-voltage protection function

Cs short circuit protection function

The loop open circuit protection function

Internal OTP IC protection function (for integrated MOS IC)

Ma / 250-500 ma, driving ability

3. The working principle of the

LD7832 is USES the voltage mode control work under boundary conditions of the fixed opening time PFC controller, using Comp voltage of the IC and IC internal Ramp signal comparison to determine the MOS the opening of the time. The working principle of the waveform in figure 7 below.

Figure 7

In half of the input voltage cycle, control the TON is fixed, the peak inductor current to follow the input voltage peak, and the same phase, to achieve high power factor PF, has the following equation:

LT) (V t) t (IONIN), peak (L = (1)

4. The typical application circuit:

In figure 8

5. Parameter design of key parts

5.1 Buck inductor design

To determine the maximum duty cycle, the output LED voltage, electric current to calculate Buck inductors:

D = VLED/VINDC (2)

L = * VLED 】【 (1 – D)/(2 * FSW * ILED) (3)

5.2 Iled current Settings:

LD7832 built-in rated current voltage is 0.2 V, thus:

ILED = 0.2 / Rs (4)

5.3 Zcd parameter design.

Figure 9

LD7832 ZCD internal voltage clamping at 0.3-5 v, IC by detecting ZCD pin to control the Gate voltage on/off and work to ensure that the IC in TM mode, this pin, also has the OVP protection function at the same time, if IZCD > 200 ua, ZCD OVP function start, plus Rz2 goal is to reduce the high voltage when the input to the ZCD pin, false trigger ZCD OVP. Suggestions of Rzcd (RZ1) resistance value is as follows, Rzcd resistance suggests greater than 100 k at least:

1.3 * uA2005V) (VR) (ZCDOUTZCD (Rz1 _OVP?) > (5) – if there is no Rz2

1.3 *} uA200 {5 / Rz25V) (VR) (ZCDOUTZCD _OVP + (Rz1)? > (6) — – — – — add Rz2 if

5.4 design of Vcc

Reference figure 8, Zenor values according to the VOUT voltage design, and generally set at around 16 v Vcc value, Zenor = VOUT – Vcc, Vcc capacitor set in 10 to 22 u F.

5.5 Comp parameter selection

The Comp capacitance value range of advice at about 0.22 1 u F.

5.6 application example 24 v300ma (output) :

5.6.1 practical application circuit diagram

Figure 10

5.6.2 the actual test output current efficiency and precision

Test condition:

Input: AC90/110/220/264 (60 hz)

Output: the CV mode: 20.4-27.6 V

Current accuracy (%) :

5.6.3 PF and THD

Five summarizes

This paper simply expounds the non isolated lines in LED driver power supply in some applications, compared with the other, using Buck PFC method can work under full voltage, constant current LED precision basically is not affected by input voltage, the LED can work with large current, and the full voltage range can achieve higher efficiency, more stable and reliable work, because work is high frequency switch mode, of course, also can bring some EMC problems, this is inevitable.

Posted by admin in led and tagged with Small power LED drive power supply topology technology solutions

LED fluorescent lamp built-in fault and the seriousness of the problem

LED fluorescent lamp is to use CREE and AOD ultra bright white light LED as light source, shell for acrylic/aluminum alloy (client). Housing available PC controls, resistance to high temperature of 135 degrees. LED fluorescent lamp with the traditional fluorescent lamp in installation dimensions are the same caliber, length 60 cm, 120 cm and 150 cm three, its power respectively 16 w and 10 w, 20 w, 20 w and traditional fluorescent lamp (ballast) the actual power consumption of about 53 w, 40 w fluorescent lamp traditional (ballast) the actual power consumption of about 68 w.
At present, almost all the led fluorescent lamp Source market built-in power supply is adopted. The so-called embedded is refers to the power supply can be placed in tubes. This built-in the biggest advantage is that you can make it directly replace the existing fluorescent tube, without having to make any changes on the original circuit. So the shape of the built-in power supply is usually elongated, to plug into a semicircular tubes. Built-in power supply has two kinds, one kind is the isolation type (figure 1), is a kind of isolation type (figure 2).

Unfenced refers to the led load and 220 v input have direct connection, so touch load there is a risk of electric shock. Only aluminum base board between 220 v and aluminum shell very thin insulating layer of isolation, usually don’t easy to pass the CE and UL certification.

Isolation type refers to the input and output isolation transformer isolation, this transformer may be power frequency or high frequency. But can be a barrier between the input and output. Can avoid the risk of electric shock. Also easily passed CE or UL certification.

A, built-in power supply the LED fluorescent lamp of electricity

USES the built-in power supply is the biggest advantage is can directly replace the current fluorescent lamp without the need to make any changes to the original wiring. The built-in this advantage is also a cost? Indeed, and the cost is not small. This should speak of from the common fluorescent lamp ballast structure:

We know that the ordinary fluorescent lights up hui is to use a iron core inductor connected in series and a parallel electric fluorescent starter (FIG. 3 a). For this kind of circuit when replace with LED fluorescent lamp directly, just unplug electric fluorescent starter. Still because of the iron core inductors in series in the circuit, so it is still nearly 6.4 W W (Philip) to 10 (domestic) loss, due to this part of the results of the additional loss is significantly reduced in LED energy saving effect. Originally a 20 w LED fluorescent lamp, for instance, can replace a 36 w fluorescent lamp, with built-in unfenced type 20 w LED fluorescent lamp, for example, the measured results are as follows.

That is, direct replacement as a result of the efficiency is greatly reduced, for domestic inductance ballasts, the efficiency is only 56.2%. Only than ordinary fluorescent lamp energy saving 6.8 W.
That makes LED fluorescent lamp, energy-saving effectiveness, so that energy management contract (EMC) difficult to enforce.

Second, the heat dissipation and lifespan

Built-in power supply another biggest drawback is the low life. Because power must be put in aluminum tube, aluminum tube is unlikely to make the fins, and can only be ordinary half cylindrical, at most, plus some strip shallow grooves on the surface (figure 4).

This half cylindrical surface area is: the 2 h / 2 = PI PI R * R * h. For T8 tubes, its diameter is 26 mm, so the 13 mm radius. 1.2 meters of T8 tubes, its surface area is: PI * 1.3 + 120 = 120 cm2, we know that the LED radiator surface area usually require 60 W/cm2. , so this kind of aluminum tube heat only scattered around 8 w. Type and T8 LED fluorescent lamp input power of 20 w, usually assume that LED the luminous efficiency of only 20%, so there are 16 w input electric power into heat. 8 w heat now only went away, and there are 8 w heat can’t dispersed, the result is that make the LED junction temperature is high, shorten service life.

Not only that, due to the power supply, built-in power supply heat is added to the tube, assuming the power efficiency of 88%, so there will be 2.4 W heat will disperse, equivalent to again to add 30% of the quantity of heat, that is to say, a total of 10.4 W power can’t send out. LED heat dissipation and increase a difficulty, or that the service life of the LED is more shorter. Also, the length of the power supply is about one 5 of the length of the tubes, power supply, by the heat is concentrated in this period, make close to power the leds are more hot baking, so life is even shorter than in other parts of the LED, fluorescent tubes, when damaged, a black first off near the power supply. Can be thought of, built-in power LED fluorescent lamp life will not higher than 10000 hours.

Inside and put the power in the pipe, the power supply itself produced by the LED under high temperature, this greatly reduces the power of the electrolytic capacitors in the life, also reduces the whole life of lamps and lanterns.

Three, use cost

Because of built-in power supply LED fluorescent lamp life only 10000 hours, compared with 50000 hours of external power supply, its use cost is obviously high five times. Not only that, in use process, whether the LED was damaged, or the power supply damaged, usually both cast together. Extra power LED fluorescent lamp, which can then be broken which.

In addition, the built-in power supply type also adds to the cost of e-waste recycling. Because the electricity supply must part off again processing respectively.

Fourth, other functions

External power supply, not only high efficiency, long life, but also can increase the manual dimming or special functions such as automatic dimmer, these are built-in incomparable!

By the introduction of more than we can concluded the built-in shortcomings and problems are very serious, unfortunately, some people only covet it may be cheaper when buy 10%, regardless of its high use cost more than 5 times. Really is big for small, not worth!

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LED the drive to achieve high power and high brightness

LED is a forward biased when incoherent narrow-spectrum light and produce a kind of electroluminescent semiconductor devices. Solid phosphor, in other words, under the effect of electric field, to convert electrical energy directly into light. Emitting light colors depends on the chemical composition of the semiconducting material used, may be close to the ultraviolet, visible or infrared light.
In the past few years, LED technology has made great progress. In cooling, packaging and process improvements obtained higher brightness, higher efficiency, longer life and lower cost. Unlike incandescent lamps, the LED will not burn out of filament, and tended to be low temperature work. Incandescent light bulbs, in addition, 95% of the energy is wasted in the form of heat.

High power and high brightness (HB) leds light output has exceeded 100 lm/W (lumens/watt) of a landmark key values. In fact, some manufacturers have already announced in the laboratory has realized 200 lm/W. So, in terms of luminous efficiency, LED is clearly more than the incandescent light bulb (a typical 60 W incandescent light output is 15 lm/W). Or to put it another way, luminous efficacy refers to the light source of the light output () for the unit with the lumen and produces it consumed power (in watts). Even so, people expected in the coming year will be easily to get in the market with 150 lm/W LED light output. Another benefit is the LED life. Having regard to the different calculation methods are different, white LED lamp has at least 50000 hours of life, some even claim that can take up to 100000 hours, and the life of the bulb is only around 1200 hours to 1500 hours.

The cost of high brightness LED lighting is in rapid decline. A few years ago, a single white light diode (several such diode of a LED lamp, most) of the cost of the LED lights price is about $4, has now dropped to less than $1. LED industry, many analysts predict that in the coming year, replace the incandescent lamp LED lights price will reach the level of consumer acceptance. Some LED maker announced, has been designed to let the LED lamp light output and most of the families are very common incandescent lamp of 75 w was comparable to the light emitting chip. This kind of LED chips usually require about 9 w power, can make the LED lamp produces is equal to 75 w incandescent lamp light output.

Today, LED driver IC must be one of the key performance characteristics can be fully adjustable light on LED lights. Because LED constant current drive, and the DC current value is proportional to the LED brightness, so change the brightness of the leds will have two kinds of dimming method through control the LED current. The first method is to simulate the light, in this way, by reducing the LED constant current value, can reduce LED the DC current is proportional to the ground. Reduce the LED current may cause the LED color change, or lead to inaccurate control of the LED current. The second method is digital or pulse width modulation (PWM) dimming. PWM dimming is equal to or higher than 100 hz frequency (human eyes perceive) conduction and shut off the LED. The duty ratio of PWM dimming is proportional to the brightness of the leds, the turn-on of the LED current to keep the same value (as set by the LED driver IC), which in high light than when the LED color. In some applications, this method of PWM dimming can be dimmer than 30000:1 under the condition of use.

Especially in the case of driving high brightness LED, LED drive IC must be able to meet the input voltage range, as well as a way to meet the output voltage and current conversion topology, for many different types of leds provide enough current and voltage. As a result, high brightness LED driver IC should ideally have the following characteristics: wide input voltage range, up to 100 v; Wide output voltage range, up to 100 v; High efficiency transformation, as high as 98%; To strictly regulate LED current match, in the change of the temperature range is less than 2%; Low noise, a constant frequency work, up to 2.5 MHz; Independent current and the dimming control; Dimmer than wide, 30000:1; A variety of switching topology, including buck, boost and buck – boost and SEPIC; Many protective functions, such as the LED string of open circuit, the LED pin VOUT to short circuit protection, undervoltage lockout threshold and accurate; Small compact solution with minimal external components.

High brightness LED, for example

There is no doubt that most of the car headlights are still incandescent lamp. But that dominance will suffer from high intensity discharge (HID) lamp and the pressure of the high brightness LED headlights. HID lamp includes all use in general illumination, high intensity discharge lamp, such as high-pressure mercury vapor lamp, high-pressure sodium lamp, low pressure sodium lamp and metal halide lamp. For indoor, building, or working or living environment, such as outer space lighting, general lighting light is bright enough. This kind of lighting applications include residential lighting, commercial and industrial lighting, lamps and car headlights. HID xenon lamp, first introduced in the 1990 s in car headlights. However, this kind of lamp manufacturing cost is very high, and therefore only used in high-end cars. Due to the recently launched high brightness LED, HID xenon lamp used in this category will reduce rapidly. Therefore, high brightness LED headlights in the next 10 years will have the largest growth.

Auto lighting system designer faces is one of the biggest obstacles, how to optimize the all functions and advantages provided by the latest generation of LED. Because leds typically need an accurate and efficient current source and a dimming method, so the LED driver IC must be designed to meet these requirements in a variety of working conditions. In addition, the power supply solutions must be efficient, solid and reliable, but also very compact and cost-effective.

Can say for driving LED, one of the most demanding applications will be auto headlight system (by the high beam, low beam lights, daytime running lights, fog lights and turn signals), because they are already experiencing severe auto electric environment test, and must adapt to a variety of temperature change at the same time. And they must also have always been able to put in very limited space, and has attractive cost structure.

Suitable for a new type of LED driver IC car headlights

LingLiEr recently launched the company LT3791 four switches is a synchronous buck – boost type LED drive and voltage regulator controller, it is very applicable to drive for car headlight application of high brightness leds. This controller in above, below or equal to the output voltage of the input voltage is within the scope of work. The device has a 4.5 V and 60 V input range and output range, 0 V and 60 V can be seamlessly switch between working mode. In addition, its unique synchronous buck – boost topology make work efficiency is as high as 98%, this greatly reduces the power loss generated by the in the form of heat required for the size and weight of the radiator.

Based on the voltage feedback pin (FB) used for leds protection function of input, and the converter can work as a constant voltage source, as shown in figure 1. The device also provide failure protection function, in order to make the LED in the case of open circuit or short circuit will not damaged, and the failure condition report, at the same time, when the fault occurs, the timer LT3791 can continue to run, atresia (latch off), or restart. It also USES a proprietary current mode topology and control architecture, and step-down and step-up modes using a current resistor.

This article summary

Although the performance characteristics of high brightness LED driver must have had a lot, but driven by this kind of LED driver with the lowest power of leds must be able to provide the necessary light output, so as not to cause considerably limits to the design of heat. In terms of high-power high-brightness LED product design personnel, fortunately, now there are high efficiency LED, and drive the high efficiency LED high-performance LED driver.

Figure 1: LT3791 at up to 100 w power drive a 3 a LED array.

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Based on the small MCU of the realization of the color of the LED lighting control

Under the big trend, LED for general lighting. In general illumination LED many advantages, such as longer life and higher efficiency. LED technology, however, is also facing some challenges. One challenge is to produce high quality white light. White LED the composition contains blue leds and the light output can be moved to the spectrum of a phosphor powder of other bands. Many white LED can produce high Color Rendering Index, Color Rendering Index, CRI), this parameter is used to measure real ability to reproduce Color light source.

By mixing two or more colors of LED light, white light system can obtain higher quality. In these multicolor system, each color of source light output will vary with time and temperature drift. Light sensor, and a small microcontroller (MCU) can be used to maintain specific colors and CorrELated Color Temperature (CorrELated Color Temperature, CCTS). In this article, we will further understand sensor, MCU resources required, and software.

On the market at present, there are many economical small light sensors, they can provide to MCU used in processing the information. Typically, the sensor has some optional color filter, used to measure the red, green, blue or white light (no filter). Light sensor output interface can be connected to the MCU through a series of methods. Turn optical voltage sensor output voltage is connected to a digital converter (ADC). Turn light sensors to provide inverter output frequency, output frequency is proportional to the amount of light. Pulse output of the sensor can be cumulative in MCU timer, to determine the level of illumination. Turn light digital sensors usually have the serial digital interface, such as I2C. Every kinds type sensor interface has unique advantages, and require different resources of MCU. System block diagram of figure 1 gives a variety of MCU peripherals, them in color adjustable LED lighting design is very useful.

In full color closed-loop control system, the MCU must be read from the color of the light sensor components, calibration light sensor outputs, and by adjusting the output of the LED driver you want to color. Need to use the LED constant current drive to maintain the consistency of output light. It can use a variety of drive technology implementation, these techniques include linear and switching mode solution. The final choice depends on the requirements, such as efficiency factors such as input voltage range and number of leds used.

Can use different methods to control the drive output. First of all, the MCU can be through a digital to analog converter (DAC) or digital potentiometer to generate the analog reference voltage. Can make the driver output reference voltage between zero to the maximum current changes. MCU can also provide for modulation output PWM signal of the driver. PWM signal can be used for enabling/ban drive itself, or is used to control the LED and driver output disconnect switch. If you are using a PWM control, the choice of PWM frequency is high enough, so that the human eye can perceive any flicker.

Designers must be sure color control system requirements of the control resolution is to what extent, so choose have MCU peripherals. The optical voltage sensor, MCU on the measuring resolution of the ADC is very important. Light switch frequency sensor needs a time base by external clock realize incremental MCU. Turning light digital sensor to the corresponding serial communication interface peripherals.

With multiple PWM peripherals MCU can be used to control all the LED driver. In high resolution color control systems, preferred with 16 or higher control resolution of PWM peripherals. Serial communication peripherals (such as UART, SPI, I2C, LIN and USB, etc.) to support the input/output control and display functions.

For color control system, PIC24FJ16GA002 MCU devices (see figure 2) are good choice. PIC24 device with small size of 28 pin encapsulation, program memory range of 16 to 64 KB, and provides in a single device serial communication interface, 10 bit ADC and five PWM channels. 16 bit MCU kernel can easily process associated with the sensor calibration and color control arithmetic.

Sensor data must be calibrated according to the reference voltage output, to provide consistent results. Calibration process using a colorimeter to different color, the sensitivity of the output of the leds and the spectral response and light sensor in the standard chromaticity coordinate system associated by mathematical method. Calibration process generates a coefficient matrix, it must be with the lighting system is stored in the nonvolatile memory, and in time control of the control system is used to determine the relevance and difference between the required output.

MCU sensor data can be after completion of calibration and the ideal of the CIE (international commission on illumination) coordinates a chromaticity diagram, and the adjusted output channel, until get ideal CCTS. Each output channel of the PID control algorithm will use the calibration value to adjust the sensor data, obtained with the target set point of difference, and then adjusting the output channel. In order to reduce error, PID will continue running until the output CCTS and set point CCTS matches so far. The PID coefficients can be fine-tuning, to maximize the response optimization system, the PID algorithm is convergent to the target speed of CCTS also MCU processing arithmetic efficiency function. May need some color control system than other system faster processing speed and response speed. General lighting system requirements than, for example, HDTV panel lower local dimming system.

Adjustable light or high CRI system has a series of user control requirements. Medical equipment with the graphical LCD display may have adjustable LED backlight with LCD (it requires the MCU through the SPI communication), and is used to adjust the CCTS and brightness of the touch screen interface. General lighting commercial display devices as may be required by the central control panel or computer, in according to automatically adjust the brightness of day each time, CCT and on/off. Communications between the equipment can use the hardwired serial bus protocol (such as DALI or DMX512) implementation, and other equipment may need to use custom interfaces by USB or Ethernet. In a completed building, install the hardwired infrastructure may not, need through the wireless communication and protocol (such as ZigBee) control. Flexible for this kind of lighting applications, with peripherals in the MCU is to realize the ideal communication and users interface.

Candles, kerosene lamp and incandescent lamp light source technology replaced the technology before them, and improve the quality of people’s lives. Expected to LED light source is better than all the other light source technology to enrich our life. LED has high efficiency, small size, portable, durable, and long service life, etc. Using small MCU to control the multicolor leds can adjust light output, to meet the requirements of the lighting space comfortable lighting. MCU can intelligently control drive circuit (to maximize energy efficiency), monitoring, and the maximum energy efficiency and life expectancy. MCU control color LED lighting system will allow people to see the world with different eyes “light”.
– — – — – — – — – — – — Home Appliances Manufacturers

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Adjustment methods of centrifugal pump and the energy consumption analysis

B2b website abstract: through the analysis of the characteristic curve of centrifugal pump and pipeline system of centrifugal pump flow control method of several main: export valve adjustment, pump variable speed adjustment and pump series, in parallel. Outlet valve adjustment was analyzed by using the characteristic curve and pump speed regulating energy loss in two ways, and has carried on the contrast, points out that the centrifugal pump with a variable speed regulating flow outlet valve can adjust flow better than using the save energy consumption, and energy saving efficiency and the size of the flow changes. In the practical application should pay attention to the scope of the variable speed regulation in order to better use centrifugal pump variable speed control.

Centrifugal pump is widely used in chemical industry system of a general fluid machinery. It has the performance to adapt to the wide range (including flow, pressure head and the nature of the medium in adaptability), small volume, simple structure, easy operation, low operation cost, a lot of advantage. Usually, selected centrifugal pump flow rate and pressure head may be inconsistent and piping requirements, or because of the production tasks, process requirement changes, at this time require to flow control of pump, essence is the change of centrifugal pump working point. Centrifugal pump working point are made from characteristic curve of pump and piping system joint decision characteristic curve, therefore, alter the characteristic curve of any one can reach the purpose of flow control. At present, the centrifugal pump flow control way are regulating valve, variable speed control and pump control and, series adjustment, etc. Because of various adjustment methods principle is different, in addition to have their own advantages and disadvantages, the energy loss is different also, in order to seek the best, the minimum energy consumption, the most energy-efficient flow regulating means, must fully understand the flow of centrifugal pump adjustment methods and the relationship between the energy consumption.

1 pump flow control mainly

1.1 change the pipeline characteristic curve

Change the simplest method is to use centrifugal pump pump discharge valve to control the open degree, its essence is to change the position of the pipeline characteristic curve to change the pump working point

1.2 change the centrifugal pump characteristic curve

According to the proportion of law and law of cutting, change the pump rotation speed, the pump structure (such as the method of cutting impeller diameter, etc.) both methods could change characteristic curve of centrifugal pump, so as to regulate traffic (change the pressure head at the same time). But for working pump, has changed the pump structure method is not very convenient, and because change the structure of the pump, reduces the commonality of pump, although it at some time convenient flow adjusting economy [1], is rarely used in production. Here only analysis of the change of centrifugal pump rotating speed adjust flow method. From figure 1, when change the pump speed adjusting flow rate decreased from Q1 to Q2, the pump speed (or motor speed) decreased from n1 to n2, rotation speed of pump under n2 Q – H curve and line characteristics curve He = H0 + G1Qe2 (line curve does not change) to point the A3 (Q2, H3), points A3 as the new speed regulating flow after working point. The adjustment method of adjustment effect, quick, safe and reliable, can prolong the service life of pump, save electricity, reduce speed running also can effectively reduce the centrifugal pump NPSH NPSHr, pump away from cavitation area, reducing the possibility of centrifugal pump cavitation occurred [2]. Drawback is that change the pump speed by variable frequency technology are needed to change prime mover speed (usually a motor), principle of complex, investment is bigger, and the flow adjustment range is small.

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Shallow theory of centrifugal pump in good standard

Pumps are widely used in tap water production line, various specifications. To its classification method also each are not identical, according to its working principle can be divided into three categories: vane pumps, positive displacement pumps, other types of pumps. In our factory are most used in the production of single stage double suction centrifugal pump, vane pump is a kind of, because of this work is to rely on high-speed rotating impeller of pump blade toggle rotation liquid, liquid to obtain centrifugal force and complete water pump water conveyance process so this pump known as the centrifugal pump.
Centrifugal pump is widely used in many departments of the national economy to use it. Nearly in the water supply system is indispensable to a device, if the tap water pipe network as a person’s cardiovascular system, so the centrifugal pump is the heart of pressure to send blood. Due to the centrifugal pump is a kind of important equipment, and its operating consumes lots of power!!!! The selection and use of the pump in order to reasonable, economy, to ensure water supply, must be in a centrifugal pump, the working principle and fundamental performance, etc.

One, the basic construction of centrifugal pump is composed of six parts
The basic construction of centrifugal pump is composed of six parts, respectively, impeller, pump body, pump shaft, bearing, seal ring, stuffing box.
1. The impeller is the core part of the centrifugal pump, its speed is higher than strength, the impeller blades and play a major role, the impeller before assembly to pass the static balance test. Impeller on the inside and outside surface smoothness requirements to reduce the flow friction loss.
2, the pump body also calls the pump shell, it is the body of the pump. Support fixation, and connected to install bearing bracket.
3, the role of pump shaft is connected by coupling and motor, the torque of the motor to the impeller, so it is a major part of the mechanical energy transfer.
4, bearing is set on the pump shaft support, pump shaft components, there are two kinds of rolling bearing and sliding bearing. Rolling bearing use butter as a lubricant oil is generally appropriate for two-thirds to three-quarters of the size too much will be fever, too little and there was a noise and fever! Sliding bearing is using a transparent oil as lubricant, go to the oil level line. Too much oil to the pump shaft seepage and floating base, too little bearing overheating and burning caused by accident! Bearing in the process of pump working in 85 degrees commonly the highest temperature is running at around 60 degrees, if the high will find reason (if there are impurities, oil is black, if water) and processed in a timely manner!
5, sealing ring, also known as minus leakage ring. Import and pump impeller shell gap between the will cause the pump to flow of water through the gap in high to low pressure area, the influence of pump water yield, low efficiency! Clearance starts to cause the impeller and pump casing friction wear. In order to increase the flow resistance reducing internal leakage and delay the use of the impeller and pump casing life, in and around the impeller pump housing aid junction with sealing ring, sealing the gap between 0.25 ~ 1.10 mm advisable.
6, mainly by the packing, stuffing box water seal ring, filler tube, packing gland, water tubes. Gland function is mainly in order to close the gap between pump casing and pump shaft, don’t let flow within the pump does not flow outside to not let outside air into the pump. Always keeping the vacuum inside the pump! When the pump shaft and packing friction heat generation relies on water seal to hold water in the water seal ring filler cooling! Keep the pump running. So the water pump in the process of the operation of the circuit check to check the stuffing box is paying special attention to! Running about 600 hours will be packing for replacement.

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Sewage pump overview

Abstract: this paper mainly introduces the structure of the sewage pump, and the characteristics of the various structural type
A, an overview of the pump
Along with the progress of the society, people life level unceasing enhancement, and increased awareness of environmental protection, sewage pump has been familiar, scope of application is also become more and more broad.
Sewage pump is a kind non-clog pump, has a variety of forms: such as diving type and dry type two kinds, the most often for WQ submersible type submersible sewage pump, the most common form of dry type sewage pump, such as w-type horizontal sewage pump and WL vertical sewage pump type two kinds. Is mainly used for conveying the urban sewage, manure or liquid containing fiber. Confetti solid particles such as medium, is often the temperature of the medium is not greater than 80 ℃. Because the transmission medium contains easy winding or bunching of the fiber content. Therefore, this kind of pump flow is easy to jam, pump once blocked can make the pump does not work, and even burning motor, resulting in poor sewage. Brings to the urban life and environmental protection seriously affected. Therefore, blocking resistance and reliability are important factors of sewage pump.

Second, the structure of sewage pump
And other pumps, the impeller, the pressurized water chamber, are two core components of sewage pump. The pros and cons of its performance, also on behalf of the advantages and disadvantages of pump performance, the anti-clogging sewage pump performance, efficiency, and cavitation performance, anti-abrasion performance mainly by vane pump and the pressurized water chamber to ensure that the two parts. Respectively introduce the below:
1, the structure of the impeller type:
Impeller structure is divided into four categories: type (open and closed), the vortex flow, the flow type, (including the single port and shuangliu) spiral centrifugal four.
Open and half open impeller manufacture is convenient, when caused by blocked in the impeller, can easy cleaning and maintenance, but in the long run, under the abrasive particles can make the blade and the interior wall of pressure water gap increased, thus reduce efficiency. And clearance increases damage of differential pressure distribution on blade. Produce large amounts of vortex loss not only, and axial force of pump will increase, at the same time, due to the gap increases, the stability of the liquid flow pattern of flow is damaged, make the pump produces vibration, this type of impeller is not easy to transport with large particles medium and long fibers, from the performance, the type of impeller efficiency is low, the highest efficiency about ordinary closed about 92% of the impeller, relatively flat head curve.
2, swirl impeller:
By using this type of impeller pump, due to the impeller part or the whole shrinkage from the pressurized water chamber flow. So no blocking performance is good, particles ability and long fiber capacity is stronger. Particles in the pressurized water chamber of eddy current generated by the impeller rotating movement, under the impetus of the suspended particles of itself does not produce energy, and only in the flow passage of fluid exchange of energy. In the process of flow, suspended particles or long fibers do not contact with the blade, blade wear more lighter, there is no gap for abrasion and increase efficiency in the long run will not result in serious decline, by using this type of impeller pump suitable for pumping with large particles medium and long fibers.
Tell from the performance, efficiency is low, the impeller is only equivalent to about 70% of the normal closed impeller, relatively flat head curve.
3, closed impeller:
The type of impeller normal efficiency is higher. And the situation is stable in the long run, by using this type of impeller pump axial force is small, and can be set on the plate before and after the blade. Front cover on a pair of blade can reduce the impeller inlet vortex losses and particle wear of sealing ring. HouGaiBan vice blade on the balance of axial force effect not only, but also can prevent suspended particles into the effect of mechanical seal mechanical seal cavity. But the type of impeller poor without plugging, easy to wound, not in pumping with large particles (long fiber), etc. At the end of the treated sewage medium.
This article from the International supplier

Posted by admin in Environmental protection equipment and tagged with Sewage pump overview

Working principle of various kinds of vacuum pump

Glass level 3 high vacuum oil diffusion pump
GG – 17 glass low expansion coefficient, better able to tolerate high temperature difference change, so this pump than the same type pump can afford the high temperature and longer service life. The pump is suitable for electronic industry, such as the vacuum tube. Picture tube. X-ray tubes, and semiconductor monocrystal silicon smelting purification, purification of high boiling oil distillation separation, fluorescent lamp, high vacuum flask vacuum exhaust equipment.

Working principle of the
First by turn the vacuum pump system to 10-2 pa diffusion pump oil is heated boiling, with high speed from spewing oil steam to gas molecule inside the system constantly to pump the side arms of tube ball bubble is assembled, the treated gas density to achieve the mechanical vacuum pump was out scope of work, and thus gradually obtain high vacuum.

Water ring type vacuum pump/liquid ring vacuum pump works
Water ring vacuum pumps (hereinafter referred to as water ring pump) is a kind of thick vacuum pump, it can obtain the ultimate vacuum of 2000 ~ 4000 pa, pa series air ejector is 270 ~ 270. Water ring pump can be used as a compressor, also known as water ring compressor, belongs to the low pressure compressor, the pressure range of 1 ~ 2 x 105 pa gauge pressure.
Water ring pump initially used as a self-priming pump, then gradually used in petroleum, chemical, machinery, mining, light industry, medicine and food and many other industrial sectors. In many industrial production process, such as vacuum filter, vacuum water diversion, vacuum feeding, vacuum evaporation, vacuum concentration, vacuum resurgence and vacuum degassing, such as water ring pump is widely used. Due to the vacuum technology leap development, water ring pump in crude vacuum has been paid great attention by people. Because water ring pump in the gas compression is isothermal, and it can take in addition to flammable, explosive gas, also can smoke in addition to the dust, water, gas, as a result, the water ring pump application is increasing.
In the pump body is equipped with the right amount of water as working fluid. When impeller rotate clockwise according to the figure, the water into the impeller around, due to the role of centrifugal force, water creates a decision in the pump cavity shape similar to, such as the thickness of the sealing ring. Water ring surface of the lower part just the wheel tangent with the impeller, water ring coincided with leaf area on the surface of the top contact (actually leaves in the water ring with a certain insertion depth). Formed between the impeller wheel, water ring a crescent-shaped space, this space is divided into impeller and blade number is equal to the number of small cavity. If the bottom of the impeller 0 ° as starting point, so the impeller before the rotate 180 ° when small cavity volume changes from small to big, and on the end face of suction mouth, the gas is inhaled, when a little at the end of the suction chamber is isolated from the rest of inspiratory mouth; When the impeller to rotate, the small cavity from large to small, make the gas is compressed; When the chamber and exhaust outlet are interlinked, the gas was discharge pump.
To sum up, the water ring pump by the pump cavity volume changes to achieve suction, compression and exhaust, so it belongs to the variable capacitance type vacuum pump.

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Pump technology development trend analysis

Pump technology development as the development of other industries, is driven by market demand. Today, history has entered the 21st century, people in areas such as environmental protection, electronic high-tech development and the sustainable development of the world to give priority to the huge demand of the backdrop, for many industries or areas, including pump industry has brought about rapid changes and development of the technology.

Pump technology development trend, personally, I think basically has the following points:
The diversity of products
Vitality is the demand of the market products. Today’s market demand is the demand has its own characteristic features, it is different; It is this, contributed to the diversity of pump products. It mainly reflected in the diversity of pump transmission medium of diversity, diversity of product structure and operation requirements of not gay.
From the perspective of the diversity of the medium, the earliest pump transportation and other objects into a single water flow of the liquid, gas or paste to the present can transport solid-liquid mixture, the mixture of gas and liquid, solid and liquid gas mixture, until delivery to live objects such as potatoes, fish, etc. The internal structure of different transport objects for pump requirements are different.
In addition to transport objects have different requirement about the structure of pump, the pump installation form, pipeline layout and maintenance of the pump’s inner or outer structure of the new requirements are put forward. At the same time, the various manufacturers, on the design of the structure and joined the respective enterprise concept, more to improve the pump structure diversification.
Based on the general background of the sustainable development and environmental protection, the pump’s running environment on the pump design and put forward many requirements, such as increased leakage to reduce vibration and noise reduction, reliability, longevity and so on are the pump design puts forward the different emphasis or focus of several parallel all needs to consider, also inevitably form diversified form of pump.

Pump design level and optimize the combination of manufacturing technology
Entering the information age today, the pump designers have already use computer technology to product development and design (e.g., the use of CAD), greatly improves the speed of the design itself, shortened product design cycle. And in the manufacture of production, manufacturing technology represented by numerical control technology is a CAM have deep into the production of pump. But, looked from the current domestic situation, CAM numerical control technology is mainly used in mass production. For single piece or small batch production, CAM technology at present has not yet been implemented throughout the pump industry, sheet small batch production is still mainly traditional production equipment.
Due to market demand manufacturer of the goods time to shorten as much as possible, especially for special products (product) for user’s request to shorten delivery cycle, the inevitable requirement of pump manufacturing enterprises accelerate the use of CAM technology, even the computer integrated manufacturing system (CIMS), the flexible manufacturing (FMC and FMS) from design to mold manufacturing, parts processing and so on each link coordinated processing, guarantee a but design, product parts processing and tend to be completed in the same period, to ensure that shorten the production cycle.
At the same time, in addition to the use of computer graphics, will also be on the computer this carrier to achieve the strength of the product reliability forecast and analysis, 3 d design, the original need to find and solve process problems in production and local structure and assembling problems mentioned before production to protect against, shorten the product manufacture phase.
– — – — – — – — – — Global Trade

Posted by admin in Environmental protection equipment and tagged with Pump technology development trend analysis