Patent ID: 9627984
Date: 2017-04-18
CPC Classifications: H02M

Claim:
1. An isolated power supply circuit with a programmable function, comprising: a first transformer circuit, which includes a primary winding and a secondary winding, wherein the primary winding receives an input voltage and the secondary winding generates a programmable output voltage at an output node; a power switch circuit, which is coupled to the primary winding, the power switch circuit operating according to an operation signal to convert the input voltage to the programmable output voltage; a discharge circuit, which is coupled to the output node, for controlling the output node to generate a discharging current according to an output node discharging control signal; and a control circuit, which is coupled to the power switch circuit and the discharge circuit, for generating the operation signal and the output node discharging control signal at least according to a setting signal for setting a voltage level of the programmable output voltage; wherein the control circuit adjusts the operation signal according to the setting signal, such that the programmable output voltage switches from a first predetermined level to a second predetermined level, and in a transition period when the programmable output voltage switches from the first predetermined level to the second predetermined level, the control circuit determines the output node discharging control signal whereby the discharge circuit adjusts the discharging current, so that the discharging current discharges the programmable output voltage; wherein the discharge circuit includes: an opto-coupler, which is coupled to the control circuit, for generating the discharge current according to the output node discharging control signal; and a voltage difference circuit, which is coupled to the opto-coupler, for providing a voltage difference in a path of the discharging current; wherein the control circuit receives the setting signal from an external circuit, or generates the setting signal internally according to the programmable output voltage or its related signal, an input current or its related signal, or an output current or its related signal.