Patent ID: 9660535
Date: 2017-05-23
CPC Classifications: H02M,H05B,Y02B

Claim:
1. A power supply circuit, comprising: a pulse width modulation controller coupled with a flyback circuit, wherein the flyback circuit comprises a primary circuit comprising a primary winding of a flyback transformer connected in series with a first field effect transistor controlled by the pulse width modulation controller and a secondary circuit comprising a second field effect transistor connected in series with an output capacitor wherein the series connected second field effect transistor and output capacitor are connected in parallel with a secondary winding of the flyback transformer, wherein the pulse width modulation controller controls the first field effect transistor and the second field effect transistor synchronously to said first field effect transistor to generate a desired output voltage through the flyback transformer, wherein the pulse width modulation controller further comprises an input receiving a dimming control signal and wherein a load is coupled with the output capacitor and a load current is regulated using an error amplifier, comparator and a latch, wherein another input of the latch is used to terminate a pulse width modulated current pulse through said load asynchronously to generate a square wave pulse current, and a shunt resistor coupled between ground and a node of the series connected second field effect transistor and the output capacitor, wherein a voltage across the shunt resistor is measured by the pulse width modulation controller.