A Soft‐Switching Dual‐Channel LED Driver With Automatic Current Balance

ABSTRACT This study proposes a soft‐switching dual‐channel LED driver with automatic current balance. To release the energy stored in the leakage inductor at the primary side of the transformer, a resonance effect is created through the clamp capacitor, resonant inductor, and the parasitic capacitors of the switches to achieve zero voltage switching (ZVS) turn‐on. This mechanism provides soft‐switching behavior similar to that of an active‐clamp flyback converter, thereby minimizing switching losses and reducing voltage spikes across the switches. On the second side of the transformer, a balancing capacitor is adopted to ensure that identical average currents pass through the two LED strings. The average current passing through the two LED strings can be regulated. Moreover, the complexity of the control loop is reduced and the power density of the circuit can be enhanced by using the capacitive balancing method. The experimental results, based on the laboratory prototypes, are presented to verify the circuit performance. According to these results, regardless of whether the two LED strings have the same or different numbers of LEDs, the current error rate between the strings remains below 1%. When the LED current reaches 350 mA, the peak efficiency of the overall circuit is up to 92.1%.