A simple circuit to remove X-cap bleeder resistor for reducing standby power consumption

Abstract

A simple circuit is introduced in this paper for eliminating power dissipation of bleeder resistor when the power converter is plugged to the power outlet. The depletion-type NMOS device can be naturally turned-on to establish discharge path of X capacitor without driving voltage for safety consideration. And the depletion-type NMOS device is virtually turned off to disconnect bleeder resistor for improving the efficiency of power converter while AC power is on. As a result, the waste power can be removed in normal operation, light load, especially in standby load conditions for comply the newest energy star specification, EuP lot 6 and 5 star standards of mobile charger standby power regulations. Experimental results demonstrate that the proposed scheme can implement ultra low standby power of converter with a simple and low cost solution.