Flyback power supply circuit with programmable function and control method thereof

Patent metadata

Field	Value
Publication number	US-9362834-B2
Application number	US-201514739894-A
Country	US
Kind code	B2
Filing date	Jun 15, 2015
Priority date	Jun 19, 2014
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

Abstract

The present invention discloses a flyback power supply circuit with a programmable function and a control method thereof. The flyback power supply circuit includes: a transformer circuit, a power switch circuit, a primary side control circuit, an opto-coupler circuit, and a secondary side control circuit. The primary side control circuit determines whether an over voltage condition occurs, and further determines whether to generate an over voltage protection signal to turn OFF a power switch of the power switch circuit according to a rate of increase of a feedback signal and a control level, or according to the rate of increase of the feedback signal and a rate of change of a target control signal.

First claim

What is claimed is:

1. A flyback power supply circuit with a programmable function, comprising:
a transformer circuit, which includes:
a primary winding, for receiving an input voltage;
a secondary winding, for generating a programmable output voltage at an output node; and
a tertiary winding, for generating a feedback signal related to the programmable output voltage according to the programmable output voltage;

a power switch circuit, which is coupled to the primary winding, for operating a power switch therein according to an operation signal, so as to convert the input voltage to the programmable output voltage;
a primary side control circuit, which is coupled to the power switch circuit, for generating the operation signal according to a target control signal;
an opto-coupler circuit, which is coupled to the secondary winding, for generating the target control signal according to the programmable output voltage and a programming signal; and
a secondary side control circuit, which is coupled to the opto-coupler circuit and the secondary winding, for generating the programming signal according to the programmable output voltage and a setting signal;
wherein the primary side control circuit determines whether an over voltage condition occurs according to a rate of increase of the feedback signal and a control level of the target control signal, or according to the rate of increase of the feedback signal and a rate of change of the target control signal, and the primary side control circuit generates an over voltage protection signal when the over voltage condition occurs.

2. The flyback power supply circuit of claim 1 , wherein the determination that the primary side control circuit determines whether an over voltage condition occurs according to the rate of increase of the feedback signal and the control level of the target control signal, includes: determining whether the rate of increase of the feedback signal exceeds a predetermined rate of increase, and whether the control level of the target control signal exceeds a predetermined control level.

3. The flyback power supply circuit of claim 1 , wherein the determination that the primary side control circuit determines whether an over voltage condition occurs according to the rate of increase of the feedback signal and the rate of change of the target control signal, includes: determining whether the rate of increase of the feedback signal exceeds a predetermined rate of increase, and whether the rate of change of the target control signal is not negative.

4. The flyback power supply circuit of claim 1 , wherein the determination that the primary side control circuit determines whether an over voltage condition occurs according to the rate of increase of the feedback signal and the control level of the target control signal, includes: determining whether a time period wherein the feedback signal increases from a first level by a predetermined level difference is shorter than a predetermine time period, wherein the first level is related to a level of the feedback signal as the target control signal exceeds a predetermined control level.

5. The flyback power supply circuit of claim 1 , wherein the determination that the primary side control circuit determines whether an over voltage condition occurs according to the rate of increase of the feedback signal and the control level of the target control signal, includes: determining whether a level difference of the feedback signal is higher than a predetermined level difference within a predetermined time period starting from when the control level of the target control signal exceeds a predetermined control level, to determine whether the rate of increase of the feedback signal exceeds a predetermined rate of increase.

6. The flyback power supply circuit of claim 1 , wherein the determination that the primary side control circuit determines whether an over voltage condition occurs according to the rate of increase of the feedback signal and the control level of the target control signal, includes: determining whether the feedback signal exceeds a second level within a predetermined time period starting from when the control level of the target control signal exceeds a predetermined control level.

7. The flyback power supply circuit of claim 1 , wherein the secondary side control circuit includes:
a comparison circuit, for generating a comparison signal according to the programmable output voltage and the setting signal; and
an adjustment circuit, which is coupled to the comparison circuit, for generating the programming signal according to the comparison signal.

8. The flyback power supply circuit of claim 7 , wherein the secondary side control circuit further includes a digital-to-analog converter (DAC) circuit, which is coupled to the comparison circuit, for converting the setting signal in a digital form to a reference voltage in an analog form, wherein the reference voltage is inputted to the comparison circuit.

9. The flyback power supply circuit of claim 1 , wherein the determination that the primary side control circuit determines whether an over voltage condition occurs according to the rate of increase of the feedback signal and the control level of the target control signal, includes: determining whether the rate of increase of the feedback signal exceeds a predetermined rate of increase, wherein the predetermined rate of increase is higher than a starting rate of increase, wherein the starting rate of increase is related to a rate of increase of the feedback signal in a start-up period of the flyback power supply circuit.

10. A control method of a flyback power supply circuit with a programmable function, comprising:
receiving an input voltage;
operating a power switch according to an operation signal, to converting an input voltage to a programmable output voltage;
generating a feedback signal according to the programmable output voltage;
generating the operation signal according to a target control signal;
generating the target control signal according to the programmable output voltage and a programming signal;
generating the programming signal according to the programmable output voltage and a setting signal; and
determining whether an over voltage condition occurs according to a rate of increase of the feedback signal and a control level of the target control signal, or according to the rate of increase of the feedback signal and a rate of change of the target control signal, and generating an over voltage protection signal when the over voltage condition occurs.

11. The control method of claim 10 , wherein the step of determining whether an over voltage condition occurs according to the rate of increase of the feedback signal and the control level of the target control signal, includes:
determining whether the rate of increase of the feedback signal exceeds a predetermined rate of increase; and
determining whether the control level of the target control signal exceeds a predetermined control level.

12. The control method of claim 10 , wherein the step of determining whether an over voltage condition occurs according to the rate of increase of the feedback signal and the rate of change of the target control signal, includes:
determining whether the rate of increase of the feedback signal exceeds a predetermined rate of increase; and
determining whether the rate of change of the target control signal is not negative.

13. The control method of claim 10 , wherein the step of determining whether an over voltage condition occurs according to the rate of increase of the feedback signal and the control level of the target control

Assignees

• Tang Chien-Fu
• Chen Isaac Y
• Chang Kuang-Fu
• Wu Hsin-Yi
• Chen An-Tung
• Richtek Technology Corp

Inventors

• Tang Chien-Fu
• Chen Isaac Y
• Chang Kuang-Fu
• Wu Hsin-Yi
• Chen An-Tung

Classifications

• H02M2001/0025

  Electricity · mapped topic

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H02M3/33523 Primary

  with galvanic isolation between input and output of both the power stage and the feedback loop · CPC title

• H02M3/33515

  with digital control · CPC title

• H02M1/0025

  Arrangements for modifying reference values, feedback values or error values in the control loop of a converter · CPC title