Power-supply IC drives multiple LEDs


Posted on Sep 2, 2012

The circuit in Figure 1 uses IC1, the integrated offline Viper22A switching regulator in a constant-current configuration to drive two to eight 1W LEDs. The circuit operates by monitoring the voltage drop across the sense resistor, R6, and uses this voltage as feedback to regulate the current through R6 and the LEDs. An operational amplifier in the TSM103, IC2, monitors the voltage drop across RSENSE and compares it with the 0.175V reference, which resistor divider R5-R7 sets, and closes the loop to maintain a 0.175V drop across the sense resistor. The output of the TSM103 drives the optocoupler, IC3, which transfers the feedback to the Viper22A on the primary side. Figures 2a , 2b, and 2c show the completed board and the top and bottom layouts.






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