Isolated Power Converter Circuit and Control Method Thereof

• US 20130215651A1
• Filed: 02/12/2013
• Published: 08/22/2013
• Est. Priority Date: 02/18/2012
• Status: Active Grant

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Liao, Chia-Wei, Liu, Jing-Meng
• Granted Patent: US 9,287,796 B2
• Time in Patent Office: Days
• US Class Current: 363/34
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H02M 5/40 with intermediate conversion into dc
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The present invention discloses an isolated power converter circuit and a control method thereof. The isolated power converter circuit includes: a transformer circuit, a power switch circuit, an opto-coupler circuit, and a control circuit. The transformer circuit includes a first winding and a second winding. The power switch circuit is coupled to the transformer circuit to control it according to a driving signal. The opto-coupler circuit generates a feedback signal. The control circuit is coupled to the power switch circuit and the opto-coupler circuit, for generating the driving signal according to the feedback signal. The control circuit includes a distinguishing circuit for distinguishing a status of the feedback signal.

Claims

1. An isolated power converter circuit, comprising:

a transformer circuit, which includes a first winding and a second winding, for converting an input voltage to an output voltage;

a power switch circuit, which is coupled to the first winding, for controlling the transformer to convert the input voltage to the output voltage according to a driving signal;

an opto-coupler circuit, which has a first opto-coupler coupled to the second winding, for generating a feedback signal according to the output voltage; and

a control circuit, which are coupled to the power switch circuit and the opto-coupler circuit, for generating the driving signal according to the feedback signal, wherein the control circuit includes;

a distinguishing circuit for generating a distinguishing signal by directly or indirectly determining a status of the feedback signal; and

a driving signal generation circuit for determining, by the distinguishing signal, whether or not generating the driving signal according to the feedback signal;

wherein the isolated power converter circuit has a normal operation mode and a stand-by mode, wherein when the isolated power converter circuit operates in the stand-by mode, an opto-coupler current flowing through the opto-coupler circuit is less than a maximum level of the opto-coupler current flowing through the opto-coupler circuit when the isolated power converter circuit operates in the normal operation mode.

2. The isolated power converter circuit of claim 1, wherein the driving signal generation circuit generates the driving signal according to the feedback signal when the output voltage is not larger than a first predetermined voltage, and the driving signal generation circuit stops operating or stop generating the driving signal according to the feedback signal when the output voltage is larger than a second predetermined voltage, wherein the second predetermined voltage is not smaller than the first predetermined voltage.

3. The isolated power converter circuit of claim 1, wherein when the output voltage is not larger than a first predetermined voltage, the feedback signal is an increasing function which increases as the output voltage increases, and when the output voltage is larger than a second predetermined voltage, the feedback signal is a decreasing function which decreases as the output voltage decreases.

4. The isolated power converter circuit of claim 3, wherein the transformer circuit further includes a third winding coupled to a same reference level as the first winding, for detecting the output voltage to generate a third winding signal;

and wherein the distinguishing circuit includes a first level determination circuit, which is coupled to the third winding, for generating the distinguishing signal according to the third winding signal when the output voltage is larger than the second predetermined voltage.

5. The isolated power converter circuit of claim 3, wherein the first level determination circuit or the driving signal generation circuit is further coupled to the opto-coupler circuit, for generating a disable signal to turn OFF the first opto-coupler when the output voltage is larger than the second predetermined voltage.

6. The isolated power converter circuit of claim 1, wherein the opto-coupler circuit further comprises a second opto-coupler, which is coupled to the second winding, for generating a stand-by signal according to the output voltage.

7. The isolated power converter circuit of claim 6, wherein the distinguishing circuit includes an enable circuit, which is coupled to the second opto-coupler, for generating an enable signal functioning as the distinguishing signal according to the stand-by signal or a signal related to the stand-by signal.

8. The isolated power converter circuit of claim 6, wherein the first opto-coupler is turned OFF when the output voltage is larger than the second predetermined voltage.

9. The isolated power converter circuit of claim 8, wherein the opto-coupler circuit further includes a second level determination circuit, for turning OFF the first opto-coupler when the output voltage is larger than the second predetermined voltage.

10. The isolated power converter circuit of claim 8, wherein the opto-coupler circuit further includes a current determination circuit, for turning OFF the first opto-coupler for a period of time when a first opto-coupler current flowing through the first opto-coupler is larger than a predetermined current.

11. The isolated power converter circuit of claim 6, wherein a maximum level of a second opto-coupler current flowing through the second opto-coupler is less than a maximum level of the first opto-coupler current.

12. The isolated power converter circuit of claim 6, wherein:

a first opto-coupler current flowing through the first opto-coupler circuit is an increasing function which increases as the output voltage increases in the normal operation mode; and

a second opto-coupler current flowing through the second opto-coupler circuit is an increasing function which increases as the output voltage increases, or the second opto-coupler current is an increasing function which increases as the output voltage increases when the output voltage is relatively low, and the second opto-coupler current is a decreasing function which decreases as the output voltage increases when the output voltage is relatively high.

13. A control circuit of an isolated power converter circuit, wherein the isolated power converter circuit includes:

a transformer circuit, which includes a first winding and a second winding, for converting an input voltage to an output voltage;

a power switch circuit, which is coupled to the first winding;

an opto-coupler circuit, having an opto-coupler coupled to the second winding, for generating a feedback signal according to the output voltage, the control circuit comprising;

a distinguishing circuit for generating a distinguishing signal by directly or indirectly determining a status of the feedback signal; and

a driving signal generation circuit for determining, by the distinguishing signal, whether or not generating the driving signal according to the feedback signal.

14. The control circuit of claim 13, wherein when the output voltage is not larger than a first predetermined voltage, the driving signal generation circuit generates the driving signal according to the feedback signal;

and when the output voltage is larger than a second predetermined voltage, the driving signal generation circuit stops operating or stops generating the driving signal according to the feedback signal, wherein the second predetermined voltage is not smaller than the first predetermined voltage.

15. The control circuit of claim 13, wherein when the output voltage is not larger than a first predetermined voltage, the feedback signal is an increasing function which increases as the output voltage increases, and when the output voltage is larger than a second predetermined voltage, the feedback is a decreasing function which decreases as the output voltage increases.

16. The control circuit of claim 15, wherein the transformer circuit further includes a third winding coupled to a same reference level as the first winding, for detecting the output voltage to generate a third winding signal;

and wherein the distinguishing circuit includes a first level determination circuit, which is coupled to the third winding, for generating the distinguishing signal according to the third winding signal when the output voltage is larger than the second predetermined voltage.

17. The control circuit of claim 15, wherein the first level determination circuit or the driving signal generation circuit is further coupled to the opto-coupler circuit, for generating a disable signal to turn OFF the first opto-coupler when the output voltage is larger than the second predetermined voltage.

18. The control circuit of claim 13, wherein the opto-coupler circuit further comprises a second opto-coupler, which is coupled to the second winding, for generating a stand-by signal according to the output voltage, and the distinguishing circuit includes an enable circuit, which is coupled to the second opto-coupler, for generating an enable signal functioning as the distinguishing signal according to the stand-by signal or a signal related to the stand-by signal.

19. A control method of an isolated power converter circuit, comprising:

driving the isolated power converter circuit by a driving signal to convert an input voltage to an output voltage;

generating a first opto-coupler current by opto-coupling according to the output voltage, for generating a feedback signal corresponding to the first opto-coupler current;

generating a distinguishing signal by directly or indirectly determining a status of the feedback signal; and

determining by the distinguishing signal whether or not generating the driving signal according to the feedback signal;

wherein the isolated power converter circuit has a normal operation mode and a stand-by mode, wherein when the isolated power converter circuit operates in the stand-by mode, the first opto-coupler current is less than a maximum level of the first opto-coupler current when the isolated power converter circuit operates in the normal operation mode.

20. The control method of claim 19, wherein the driving signal is generated according to the feedback signal when the output voltage is not larger than a first predetermined voltage, and the driving signal is not generated according to the feedback signal when the output voltage is larger than a second predetermined voltage, wherein the second predetermined voltage is not smaller than the first predetermined voltage.

21. The control method of claim 19, wherein when the output voltage is not larger than a first predetermined voltage, the first opto-coupler current is an increasing function which increases as the output voltage increases, when the output voltage is larger than a second predetermined voltage, the first opto-coupler current is a decreasing function which decreases as the output voltage decreases.

22. The control method of claim 21 further comprising:

generating the distinguishing signal by determining a level of the output voltage.

23. The control method of claim 21 further comprising:

stopping generating the first opto-coupler current by opto-coupling when the output voltage is larger than the second predetermined voltage.

24. The control method of claim 19 further comprising:

generating a second opto-coupler current by opto-coupling according to the output voltage, for generating a stand-by signal.

25. The control method of claim 24, wherein the distinguishing signal is generated according to the stand-by signal.

26. The control method of claim 24 further comprising:

stopping generating the first opto-coupler current by opto-coupling when the output voltage is larger than the second predetermined voltage.

27. The control method of claim 24 further comprising:

stopping generating the first opto-coupler current by opto-coupling for a period of time when the first opto-coupler current is larger than a predetermined current.

28. The control method of claim 24, wherein the second opto-coupler current is less than a maximum level of the first opto-coupler current.

29. The control method of claim 24, wherein:

the first opto-coupler current is an increasing function which increases as the output voltage increases in the normal operation mode, and

the second opto-coupler current is an increasing function which increases as the output voltage increases, or the second opto-coupler current is an increasing function which increases as the output voltage increases when the output voltage is relatively low, and the second opto-coupler current is a decreasing function which decreases as the output voltage increases when the output voltage is relatively high.