LED DRIVE CIRCUITSWord文档格式.docx

1、1） Low driving voltage（the available voltage is lower than the forward voltage）Applications: LED flashlights, emergency lamps, energy-saving lamps.Solutions: Boost Converter （using inductance to store the energy）Requirements: low cost, high efficiency in converting, small volume2） Transitional drivi

2、ng voltageSometimes the available voltage supply is higher than the forward voltage, while sometimes lower.Application: LED miners lamp reverse polarity charge pump converter3） high driving voltage lawn lamp, headlights. series-woundswitches buck converter4） Commercial power supply Voltage reduction

3、, current rectification, high changing efficiency, low cost, small in size.Small and medium power consuming LEDs: single-end fly-back converterHigh Power consuming LEDs: bridge circuit3. Typical driving circuits-driversi. Capacitor-based buck converterii. Using SCRiii. Using filtering unitiv. Most s

4、implifying way of using capacitors to reduce the voltage1. Typical voltage-reducing drive circuit for LEDs4. Typical on-chip ICs for use i. RGB LED driver STP24DP05 LCD monitorsThe STP24DP05 is a monolithic, low voltage, low current power 24-bit shift register designed for LED panEL displays. The de

5、vice contains a 8 x 3-bit serial-in, parallel-out shift register that feeds a 8 x 3-bit D-type storage register. In the output stage, twenty-four regulated current sources were designed to provide 5-80 mA constant current to drive the LEDs.ii. Charge pumps for driving white LEDsiii. Running an LED w

6、ith pulses to get maximum brightnessTo give maximum brightness an LED needs to be driven by a pulse circuit. In this way, it is possible to put 0.5 Amp current pulses through an LED at a frequency of around 100Hz which fools the eye into thinking that it sees a continuous light.If the LED is run at

7、0.5 Amps for very long, it will burn out （usually within a fraction of a second）. By keeping the pulse duration relatively short, we can avoid overheating the LED.This circuit allows adjustment of the pulse width so that the maximum average current is no more than 50mA.To ensure long LED life, it sh

8、ould be adjusted for maximum brightness then reduced slightly to an average current of around 40mA. One or two LEDs can be driven simultaneously. C1 can be around 1000uF and acts as a reservoir because the average battery is unable to supply half Amp pulses of current. The circuit can be run from a

9、battery or dc supply of 9 to 12 volts.We had intended to supply all the parts as a kit but weve had only 2 enquiries in two years. However, you should be able to order all the components from Maplin Electronics in the UK.iv. LED Drive Circuit （SM-CCP-20W）LED Drive Circuit （SM-CCP-20W）Product Descrip

10、tionSM-CCP - 20W is a constant current LED drive circuit using IC manufacturers, the circuit is simple and efficient. No capacitors, resistors buck. Small heat, Circuit reliable, easy to EMI testing. For supporting the use of high-power LED. Maximum 22-1W LED. Widely used LED lights, spotlights, lig

11、hts cups, lamps, etc. SM-CCP - 22W - using single-sided PCB design. Coat with a moisture role. Technical parameters Automatically adapting input voltage range: 90 - 265V AC Output current 50-54 - 350mA + -15% （200336） Rated: 20W LED voltage: 10-60V Efficiency: 80% Automatic adaptation of color LED a

12、void a lot of resistance adjustment. Compact: Long-* * width = 76 * 43 * 32mm Model: SM-CCP - 20WCompany:Xiangshan Solarmax Photo-Electric Co., LtdA. ballast resistor Other considerations: stability of current and electrical efficiency“Voltage-coefficient” way of calculating the properties of the circuitVoltage-coefficient： （3） Stability of current: （） （4） （假定）；Electrical efficiency = （） （5）;Ballast resistor: R= （） （6）；Source voltage: U= （V） （7）