New scheme to eliminate power loss of start-up resistor for low standby power consumption

Abstract

In the initial start-up period of power converter, there is no voltage supply from auxiliary winding to pulse-width-modulation (PWM) IC. Therefore, a typical method is connected with a start-up resistor (R-start) between bridge rectifier and IC controller for initial voltage supply. However, the Rstart would continue to consume energy even if the auxiliary voltage has been set up. The proposed scheme uses depletion-type NMOS to connect with R-start. The start-up mechanism can be guaranteed without any additional voltage, and naturally cut off the Rstart to minimize power dissipation once the voltage of PWM IC is supplied from auxiliary winding. As a result, the outstanding standby power performance can be implemented and comply the power regulation of 5 star standards of mobile charger. Experimental results demonstrate the standby power consumption only 28.8mW.