STEVAL-ILL023V1

STEVAL-ILL023V1 Demonstration board: high-efficiency switching LED driver for high-current LEDs based on the L6726A Data Brief Features ■ Input voltage Vin: 8 V to 18 V ■ Output voltage (with Vin = 18 V): 2.5 V to 14 V ■ Output current ILED: 1 A / 1.5 A / 2.8 A ■ Analog dimming (with ILED= 0 A): 0 V to 2.5 V ■ Low level PWM signal: 0 V ■ High level PWM signal: 2.8 V to 3.8 V (typ: 3.3 V) ■ Duty cycle (at fdim = 200 Hz): 0% to 99 % ■ Efficiency (with Vin = 18 V and Vout = 12.6 V): 94.8 % Description Rapid advances in LED technology has led to increases in their output current capabilities in recent years. 0.350 A LEDs, for example, were soon followed by 0.7 A LEDs, and then 1 A devices appeared shortly thereafter. Currently, LEDs with currents as high as several amps are present on the market. However, these high currents increase the requirements of the driving circuitry of the LEDs, particularly in terms of efficiency. STEVAL-ILL023V1 The STEVAL-ILL023V1 demonstration board is based on the L6726A single phase PWM controller, with two external MOSFETS for synchronous rectification. Designed for 2.8 A LEDs (1-3 in a series string), the main benefit of the solution is its exceptional efficiency. Ease of dimming and scalability to even higher currents are additional advantages of the design. The solution is also much safer with regard to border conditions, since the current limit is based solely on the selection of the MOSFETS. February 2009 Rev 1 For further information contact your local STMicroelectronics sales office. 1/4 www.st.com 4 3 2 1 PWM C1 22uF GND GN PWM Vcc18V 62k R1 3 C5 1 D1 0nF TS821 100n Vref 4k7 R3 OUT GND GN 06AC L78L06 R4 4k7 IN U1 2 8-18V K375A 1 2 3 R5 6k8 FB 7 6 C3 82nF R2 1k1 C6 100n 00nF C2 470 70pF Comp C4 10uF Vcc cc6V COMP FB U2 5 Vcc GND GN 3 Lgate Phase Ugate Boo oot L6726A 4 8 2 1 Boo oot 1N4148 D2 2R2 R8 Phase 2R2 C7 100n 0nF R7 R6 10R Lgate Ugate 4 2 Q1 STS8DNH3LL 8 7 1 2/4 5 6 L1 Inductor 10uH D3 STPS1L30M C8 4.7uF R9 0R56 C9 22uF R10 0R56 OU OUT-K OU OUT-A P1 R14 0R56 R15 0R3 R16 0R3 6 5 4 3 2 1 OU OUT Figure 1. 3 1 1 2 3 CN1 Circuit schematic STEVAL-ILL023V1 Circuit schematic STEVAL-ILL023V1 schematic diagram STEVAL-ILL023V1 2 Revision history Revision history Table 1. Document revision history Date Revision 26-Feb-2009 1 Changes Initial release. 3/4 STEVAL-ILL023V1 Please Read Carefully: Information in this document is provided solely in connection with ST products. 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