Method and apparatus for a high voltage power supply circuit

Abstract

A power switch is switched to regulate an output of a power converter. A feedback signal representative of a power converter output during a feedback portion of an off time of the power switch is received. The feedback signal is above a threshold during a fraction of the feedback portion of the off time of the power switch and the feedback signal is below the threshold during another fraction of the feedback portion of the off time of the power switch. The fractions of the feedback portion of the off time of the power switch are regulated in response to the feedback signal by controlling the switching the power switch.

1 . A method, comprising:
 switching a power switch to regulate an output of a power converter;   receiving a feedback signal representative of a power converter output during a feedback portion of an off time of the power switch, wherein the feedback signal is above a threshold during a fraction of the feedback portion of the off time of the power switch and the feedback signal is below the threshold during another fraction of the feedback portion of the off time of the power switch; and   regulating said fractions of the feedback portion of the off time of the power switch in response to the feedback signal by controlling said switching the power switch.   
     
     
         2 . The method of  claim 1  further comprising:
 discharging a capacitor when the feedback signal is above the threshold during the fraction of the feedback portion of the off time of the power switch; and 
 charging the capacitor when the feedback signal is below the threshold during the fraction of the feedback portion of the off time of the power switch; and 
 
     
     
         3 . The method of  claim 1  further comprising:
 comparing the feedback signal with a signal representative of the threshold; 
 coupling a first current source to the capacitor when the feedback signal is greater than the signal representative of the threshold during the fraction of the feedback portion of the off time of the power switch; and 
 coupling a second current source to the capacitor when the feedback signal is less than the signal representative of the threshold during the fraction of the feedback portion of the off time of the power switch. 
 
     
     
         4 . The method of  claim 3  further comprising stabilizing first and second voltages across the first and second current sources. 
     
     
         5 . The method of  claim 1  wherein switching the power switch to regulate the output of the power converter comprises modulating a pulse width of an output signal coupled to switch the switch in response to the feedback signal. 
     
     
         6 . The method of  claim 1  further comprising compensating for a voltage drop in a cable coupled the output of the power converter due to an impedance of the cable by mirroring a cable drop compensation signal generated in response to the feedback signal. 
     
     
         7 . The method of  claim 6  further comprising filtering a current mirror circuit coupled to mirror the cable drop compensation signal. 
     
     
         8 . The method of  claim 1  further comprising compensating for a voltage drop in a diode in the output of power converter due to an impedance of the diode by mirroring a diode drop compensation current signal in response to the feedback signal.