Expandable two‐channel LED driver with galvanic isolation and automatic current balance

Abstract

Here, applying the coupled inductor and the capacitor to the isolated light-emitting diode (LED) driving circuit is studied, and hence an isolated two-channel LED driver featuring automatic current balance and zero dc magnetising inductance current is presented. In the proposed LED driver, each winding of the transformer has a capacitor connected in series. Therefore, the dc magnetising inductance current is zero, and hence the entire core B - H curve loop can be utilised, which can lower the core size. Moreover, due to the capacitor on the secondary side, the LED currents can be balanced naturally. The two-channel isolated LED driver can be extended to a multi-channel LED driver without increasing the output voltage. Therefore, the duty cycle of the multi-channel LED driver is determined by the sum of the voltages of two LED strings. Finally, the detailed theoretical analyses and experimental results are provided to verify the feasibility and effectiveness of the proposed LED driver.