Isolated Switch-Mode Current Regulator With Integrated Two Boost LED Drivers

A new isolated switch-mode current regulator is proposed for an LED driving system. The two boost LED drivers are integrated with the dc/dc converter, which results in a simple structure and low component count. The primary side provides an ac voltage source to the secondary side in which one boost inductor, two switches, and diodes comprise two boost drivers. Each secondary switch controls each LED current to be balanced. The voltage stresses of the primary switches are clamped to the input voltage, and those of secondary switches and diodes are clamped to the output voltages. Furthermore, all switches can easily achieve zero-voltage switching by using the transformer magnetizing current without additional auxiliary circuits. The validity of this proposed circuit is confirmed by the experimental results from a 400-V-input and 150-W-output prototype with two 75-W LED strings.