Control circuit applied to a power converter and operation method thereof

Patent metadata

Field	Value
Publication number	US-9755421-B2
Application number	US-201514599554-A
Country	US
Kind code	B2
Filing date	Jan 19, 2015
Priority date	Jan 23, 2014
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

A control circuit applied to a power converter includes a multi-functional pin, a zero-crossing signal generator, and an over-voltage detector. The multi-functional pin is used for receiving an auxiliary current generated by an auxiliary winding of the power converter, and an input current. The zero-crossing signal generator is used for generating a zero-crossing signal according to the auxiliary current. The over-voltage detector is used for generating an over-voltage signal according to the auxiliary current. The control circuit generates a switch control signal to the power switch according to the zero-crossing signal, or generates an over-voltage protection signal to the power switch according to the over-voltage signal.

First claim

What is claimed is:

1. A control circuit applied to a power converter, the control circuit having a brown-out protection, an over-temperature protection, and an over-voltage protection, the control circuit comprising:
a multi-functional pin for receiving an auxiliary current generated by an auxiliary winding of the power converter, and an input current;
a zero-crossing signal generator for generating a zero-crossing signal according to the auxiliary current;
an over-voltage detector for generating an over-voltage signal according to the auxiliary current;
a sample and hold unit coupled to the multi-functional pin for generating a sampling current corresponding to a positive half cycle of an alternating current voltage according to the input current received by the multi-functional pin when the alternating current voltage is at the positive half cycle and the power switch is turned on;
and a subtractor coupled to the multi-functional pin and the sample and hold unit for subtracting the input current received by the multi-functional pin according to the sampling current to filter the auxiliary current when the power switch is turned off, wherein the sampling current is substantially equal to the input current;
wherein the control circuit generates a switch control signal to a power switch of the power converter according to the zero-crossing signal, or generates an over-voltage protection signal to the power switch according to the over-voltage signal.

2. The control circuit of claim 1 , wherein the over-voltage detector generating the over-voltage signal according to the auxiliary current is the over-voltage detector generating the over-voltage signal according to the auxiliary current and a first reference current, or according to an auxiliary voltage corresponding to the auxiliary current and a first reference voltage; the zero-crossing signal generator generating the zero-crossing signal according to the auxiliary current is the zero-crossing signal generator generating the zero-crossing signal according to the auxiliary current and a second reference current, or according to the auxiliary voltage and a second reference voltage.

3. The control circuit of claim 1 , further comprising:
a current to voltage converter coupled to the subtractor for generating the auxiliary voltage according to the auxiliary current.

4. The control circuit of claim 1 , wherein the multi-functional pin is coupled to a rectifier of the power converter through a diode.

5. The control circuit of claim 1 , further comprising:
a switching circuit coupled to the multi-functional pin;
a brown-out detection circuit coupled to the switching circuit for generating a brown-out signal according to a detection voltage corresponding to a peak value of a positive half cycle of an alternating current voltage and a third reference voltage when the alternating current voltage is at the positive half cycle and the power switch is turned on; and
an over-temperature detection circuit coupled to the switching circuit for generating an over-temperature signal according to a voltage signal corresponding to an ambient temperature and a fourth reference voltage when the alternating current voltage is at a negative half cycle and the power switch is turned on;
wherein the control circuit generates a brown-out protection signal to the power switch according to the brown-out signal, or generates an over-temperature protection signal to the power switch according to the over-temperature signal.

6. The control circuit of claim 5 , wherein when the alternating current voltage is at the positive half cycle, the switching circuit makes the brown-out detection circuit be coupled to the multi-functional pin, and the switching circuit generates the detection voltage according to a peak current corresponding to the peak value of the positive half cycle of the alternating current voltage.

7. The control circuit of claim 5 , wherein when the alternating current voltage is at the negative half cycle, the switching circuit makes the over-temperature detection circuit be coupled to the multi-functional pin to let a thermistor coupled to the multi-functional pin generate the voltage signal according to a third reference current.

8. The control circuit of claim 7 , wherein the thermistor is coupled to the multi-functional pin through a diode.

9. The control circuit of claim 1 , wherein the input current corresponds to an alternating current voltage.

10. An operation method applied to a brown-out protection, an over-temperature protection, and an over-voltage protection of a control circuit of a power converter, the control circuit comprising a multi-functional pin, a zero-crossing signal generator, an over-voltage detector, a sample and hold unit, a subtractor, a current to voltage converter, a switching circuit, a brown-out detection circuit, a counter, and an over-temperature detection circuit, wherein the multi-functional pin is coupled to a rectifier of the power converter and a thermistor, the operation method comprising:
the sample and hold unit generating a sampling current according to an input current received by the multi-functional pin, and the brown-out detection circuit or the over-temperature detection circuit executing a first corresponding operation according to an alternating current voltage when a power switch of the power converter is turned on;
the multi-functional pin receiving an auxiliary current generated by an auxiliary winding of the power converter and the input current when the power switch is turned off;
the subtractor subtracting the input current received by the multi-functional pin according to the sampling current to filter the auxiliary current, wherein the sampling current is substantially equal to the input current when the power switch is turned off; and
the over-voltage detector or the zero-crossing signal generator executing a second corresponding operation according to the auxiliary current when the power switch is turned off.

11. The operation method of claim 10 , wherein the over-voltage detector or the zero-crossing signal generator executing the second corresponding operation according to the auxiliary current when the power switch is turned off comprises:
the over-voltage detector generating an over-voltage signal when the auxiliary current is greater than a first reference current.

12. The operation method of claim 11 , further comprising:
the control circuit generating an over-voltage protection signal to the power switch according to the over-voltage signal.

13. The operation method of claim 10 , wherein the over-voltage detector or the zero-crossing signal generator executing the second corresponding operation according to the auxiliary current when the power switch is turned off comprises:
the current to voltage converter generating an auxiliary voltage according to the auxiliary current; and
the over-voltage detector generating an over-voltage signal when the auxiliary voltage is greater than a first reference voltage.

14. The operation method of claim 13 , further comprising:
the control circuit generating an over-voltage protection signal to the power switch according to the over-voltage signal.

15. The operation method of claim 10 , wherein the over-voltage detector or the zero-crossing signal generator executing the second corresponding operation according to the auxiliary current when the power switch is turned off comprises:
the zero-crossing signal generator generating a zero-crossing signal according to the auxiliary current and a second reference current when the auxiliary current is less than a first refe

Assignees

• Leadtrend Tech Corp

Inventors

• Chang Chih-Chi
• Wei Da-Chun
• Tsou Ming-Chang
• Tsai Meng-Jen

Classifications

• H02H3/20

  responsive to excess voltage · CPC title

• H02H7/1213

  for DC-DC converters · CPC title

• H02H5/042 Primary

  using temperature dependent resistors · CPC title