Flyback power converter having overly high voltage protection and primary side controller circuit thereof

Patent metadata

Field	Value
Publication number	US-10686366-B2
Application number	US-201916395341-A
Country	US
Kind code	B2
Filing date	Apr 26, 2019
Priority date	Jul 6, 2018
Publication date	Jun 16, 2020
Grant date	Jun 16, 2020

Abstract

A flyback power converter includes: a transformer, a primary side switch and a primary side controller circuit. The primary side controller circuit includes: a pulse modulation circuit and a protection control circuit. The pulse modulation circuit generates a pulse modulation signal. The protection control circuit is coupled to the pulse modulation circuit and compares an AC voltage related signal with an over voltage threshold. When the AC voltage related signal exceeds the over voltage threshold, the comparison circuit generates an over voltage protection trigger signal. When the pulse number of the over voltage protection trigger signal exceeds the over voltage counting threshold, the over voltage counter circuit triggers an over voltage protection signal, to indicate that an over voltage condition occurs, and a protection operation is performed.

First claim

What is claimed is:

1. A flyback power converter, comprising:
a transformer having a primary winding which is configured to operably receive an input voltage, and a secondary winding which is configured to generate an output voltage;
a primary side switch coupled to the primary winding; and
a primary side controller circuit at a primary side of the transformer, the primary side controller circuit being configured to operably generate a switch control signal to control the primary side switch, so as to control a conduction status of the primary winding, wherein the primary side controller circuit includes:
a pulse modulation circuit, which is configured to operably generate a pulse modulation signal; and
a protection control circuit coupled to the pulse modulation circuit;
wherein the protection control circuit includes:
a comparison circuit, which is configured to operably compare an AC voltage related signal with an over voltage threshold, wherein when the AC voltage related signal exceeds the over voltage threshold, the comparison circuit is configured to operably generate an over voltage protection trigger signal; wherein the AC voltage related signal and the input voltage are both related to an AC voltage;
an over voltage counter circuit, which is configured to operably count the over voltage protection trigger signal, wherein when the count of the over voltage protection trigger signal exceeds an over voltage counting threshold, the over voltage counter circuit triggers an over voltage protection signal, to indicate that an over voltage condition occurs;
a protection logic circuit, which is configured to operably generate the switch control signal according to the over voltage protection signal and the pulse modulation signal, whereby a protection operation is performed when the over voltage condition occurs; and
a debounce circuit, coupled between the comparison circuit and the over voltage counter circuit, the debounce circuit being configured to operably debounce a comparison result generated according to the comparison between the AC voltage related signal and the over voltage threshold, to generate the over voltage protection trigger signal; wherein when the AC voltage related signal exceeds the over voltage threshold for a time period longer than an over voltage protection delay period, the debounce circuit generates the over voltage protection trigger signal.

2. A flyback power converter, comprising:
a transformer having a primary winding which is configured to operably receive an input voltage, and a secondary winding which is configured to generate an output voltage;
a primary side switch coupled to the primary winding; and
a primary side controller circuit at a primary side of the transformer, the primary side controller circuit being configured to operably generate a switch control signal to control the primary side switch, so as to control a conduction status of the primary winding, wherein the primary side controller circuit includes:
a pulse modulation circuit, which is configured to operably generate a pulse modulation signal; and
a protection control circuit coupled to the pulse modulation circuit;
wherein the protection control circuit includes:
a comparison circuit, which is configured to operably compare an AC voltage related signal with an over voltage threshold, wherein when the AC voltage related signal exceeds the over voltage threshold, the comparison circuit is configured to operably generate an over voltage protection trigger signal; wherein the AC voltage related signal and the input voltage are both related to an AC voltage;
an over voltage counter circuit, which is configured to operably count the over voltage protection trigger signal, wherein when the count of the over voltage protection trigger signal exceeds an over voltage counting threshold, the over voltage counter circuit triggers an over voltage protection signal, to indicate that an over voltage condition occurs;
a protection logic circuit, which is configured to operably generate the switch control signal according to the over voltage protection signal and the pulse modulation signal, whereby a protection operation is performed when the over voltage condition occurs; and
an overtime circuit, being configured to, after the over voltage protection trigger signal has been triggered, but the over voltage protection trigger signal is not triggered again during a reset delay period, operably trigger an over voltage counting reset signal to reset the over voltage counter circuit.

3. The flyback power converter of claim 1 , wherein the protection operation includes: disabling the pulse modulation signal when the over voltage protection signal indicates that an over voltage condition occurs, so that the switch control signal ceases switching the primary side switch.

4. The flyback power converter of claim 1 , wherein when the over voltage counter circuit triggers the over voltage protection signal, the over voltage counter circuit further latches the over voltage protection signal, to indicate that an over voltage condition occurs.

5. The flyback power converter of claim 2 , wherein the overtime circuit includes an overtime counter, which is configured to operably count a clock pulse signal, so as to count the reset delay period.

6. The flyback power converter of claim 5 , wherein when the overtime circuit triggers the over voltage counting reset signal, the overtime circuit further latches the over voltage counting reset signal, to reset the count of the over voltage counter circuit.

7. The flyback power converter of claim 5 , wherein the overtime circuit adopts the pulse modulation signal as the clock pulse signal, to count the reset delay period.

8. The flyback power converter of claim 1 , wherein the over voltage protection delay period is smaller than a cycle period of the AC voltage related signal.

9. The flyback power converter of claim 1 , further comprising: a rectifier circuit, which is configured to operably rectify the AC voltage to generate the AC voltage related signal.

10. A primary side controller circuit configured to operably control a flyback power converter, the flyback power converter comprising: a transformer having a primary winding which is configured to operably receive an input voltage, and a secondary winding which is configured to generate an output voltage; and a primary side switch coupled to the primary winding; the primary side controller circuit being at a primary side of the transformer, wherein the primary side controller circuit is configured to operably generate a switch control signal to control the primary side switch, so as to control a conduction status of the primary winding, the primary side controller circuit comprising:
a pulse modulation circuit, which is configured to operably generate a pulse modulation signal; and
a protection control circuit coupled to the pulse modulation circuit;
wherein the protection control circuit includes:
a comparison circuit, which is configured to operably compare an AC voltage related signal with an over voltage threshold, wherein when the AC voltage related signal exceeds the over voltage threshold, the comparison circuit is configured to operably generate an over voltage protection trigger signal; wherein the AC voltage related signal and the input voltage are both related to an AC voltage;
an over voltage counter circuit, which is configured to operably count the over voltage protection trigger signal, wherein when the count of the over voltage protection trigger signal exceeds an over voltage counting threshold, the over voltage counter circuit triggers an over voltage protection signal, to indicate that an over voltage condition oc

Assignees

• Richtek Technology Corp

Inventors

• Chang Kuang-Fu

Classifications

• H02M1/0003

  Details of control, feedback or regulation circuits · CPC title

• H02M1/007

  Plural converter units in cascade (push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826) · CPC title

• H02M3/33523 Primary

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

• H02M3/335

  using semiconductor devices only · CPC title

• H02M1/32 Primary

  Means for protecting converters other than automatic disconnection · CPC title