Nonisolated Single-Switch Two-Channel LED Driver with Simple Lossless Snubber and Low-Voltage Stress

In two-channel light-emitting diode (LED) driver, capacitive-current-balancing method is the simplest and the most effective way to equally balance the current in each channel due to its simplicity. As a result, the capacitive balancing method was used with flyback or tapped-boost converters in low-power LED applications. Since flyback and tapped-boost converters suffer from a snubber loss and a high-voltage stress on the switching devices, conventional approaches use additional passive components, resulting in the limitations on the cost and power density. In this paper, a new converter topology for low-power two-channel LED application has been proposed. The proposed converter uses the blocking capacitor and the output capacitor as a snubber capacitor so that it has a low-voltage stress without using the additional components. Although the blocking capacitor plays a role as a snubber capacitor, the current balancing characteristic is still preserved. Furthermore, the proposed converter has a high efficiency since it minimizes the number of semiconductor components in the current paths. The effectiveness of the proposed converter has been verified with an offline 3.3 Vdc input and 11.55 W rated output prototype.