Patent ID: 9025348
Filing Date: 2015-05-05
Classification: H02M

Abstract:
1. A drive circuit for driving a normally-on high-side switch and a normally-off low-side switch, the high-side and low-side switches connected in a series manner and connected in parallel with a DC power source through a primary winding of a transformer, the drive circuit comprising: a controller configured to turn on/off the high-side and low-side switches by outputting a pulse signal; a rectifier having a first end connected to a connection point of the high-side and low-side switches; a capacitor connected to a second end of the rectifier and a first end of the DC power source and serving as a power source of the controller; and a driver turning on/off the high-side and low-side switches according to the pulse signal of the controller and a voltage of the capacitor, wherein the driver includes: a high-side switch control part configured to turn on/off the high-side switch according to the pulse signal of the controller; a comparator comparing the voltage of the capacitor with a threshold voltage; and a low-side switch control part configured to turn on/off the low-side switch according to an output from the comparator and the pulse signal of the controller, and wherein the comparator is a hysteresis comparator, turns on the low-side switch when the voltage of the capacitor increases to an upper threshold voltage, and turns off the low-side switch according to the pulse signal of the controller.