Source switching circuit with low-gate-driving loss in high-voltage buck light emitting diode driver

Source switching circuit with low-gate-driving loss in high-voltage buck light emitting diode (LED) driver is proposed in this study. Source switching circuit comprises of a high-voltage power metal-oxide semiconductor field-effect transistor (MOSFET) (HVMOS) and a low-voltage power MOSFET (LVMOS) in series, a capacitor and a Zener diode. By switching the HVMOS by different source voltage and constant gate voltage, it recycles gate charges of HVMOS to reduce gate-driving loss. Gate charges are recycled in the capacitor when LVMOS is turning off, and can be reused when LVMOS is turning on. This circuit also provides a new power feeding route for control chip, and power consumption is relatively low on the proposed route. The power feeding route also improves power efficiency. With a 12 W LED load, the experiment shows that the efficiency of the proposed driving circuit is improved by 3.7% with 156 V input voltage and 4.8% with 326 V input voltage compared with the converter using single HVMOS.