Power supply apparatus

Patent metadata

Field	Value
Publication number	US-9954447-B2
Application number	US-201615155231-A
Country	US
Kind code	B2
Filing date	May 16, 2016
Priority date	Jan 13, 2016
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A power supply apparatus includes a flyback converter and a controller. The controller generates, in response to an output voltage generated by the flyback converter and stabilized at a selected one of a plurality of voltage values, a control signal associated with the selection of the voltage values. Based at least on the output voltage and the control signal, the controller generates a feedback voltage associated with loading of the power supply apparatus, and controls a switch of the flyback converter in such a manner that the switch operates at a switching frequency associated with the feedback voltage, and that at least one of the feedback voltage or a curve of the switching frequency with respect to the feedback voltage changes due to the control signal.

First claim

What is claimed is:

1. A power supply apparatus comprising:
a flyback converter receiving a bulk voltage, generating an output voltage in response to the bulk voltage, and including a transformer that includes a primary winding and a secondary winding, and a switch coupled to the primary winding, the output voltage being stabilized at one of a plurality of predetermined voltage values alternatively selected therefor; and
a controller coupled to said flyback converter for receiving the output voltage therefrom, and generating, in response to the output voltage, a control signal associated with the selection of the predetermined voltage values;
said controller executing based at least on the output voltage and the control signal, said controller generating a feedback voltage associated with loading of the power supply apparatus, and controlling said switch in such a manner that said switch operates at a switching frequency associated with the feedback voltage, and that at least one of the feedback voltage or a curve of the switching frequency with respect to the feedback voltage changes responsive to the control signal;
said controller including:
a first isolated feedback unit coupled to said flyback converter for receiving the output voltage therefrom, and generating, in response to the output voltage, a first feedback current input associated with the loading;
a second isolated feedback unit coupled to said flyback converter for receiving the output voltage therefrom, and generating, in response to the output voltage, a second feedback current input associated with the selection of the predetermined voltage values; and
a control unit coupled to said switch and said first and second isolated feedback units, receiving the first and second feedback current inputs respectively from said first and second isolated feedback units, and generating the control signal in response to the second feedback current input, based at least on the first feedback current input and the control signal, said control unit generating the feedback voltage and controlling said switch.

2. The power supply apparatus of claim 1 , wherein the feedback voltage changes due to the control signal.

3. The power supply apparatus of claim 1 , wherein the switching frequency has an upper limit that changes due to the control signal.

4. The power supply apparatus of claim 1 , wherein the curve of the switching frequency with respect to the feedback voltage has a turning point that changes due to the control signal.

5. The power supply apparatus of claim 1 , wherein said control unit includes:
an adjustment control circuit coupled to said second isolated feedback unit for receiving the second feedback current input therefrom, and generating the control signal in response to the second feedback current input;
a converting circuit coupled to said first isolated feedback unit and said adjustment control circuit for receiving the first feedback current input and the control signal respectively therefrom, and generating the feedback voltage in response to the first feedback current input and the control signal;
a frequency control circuit coupled to said converting circuit for receiving the feedback voltage therefrom, and generating a control voltage in response to the feedback voltage; and
a driving circuit coupled to said switch and said frequency control circuit, receiving the control voltage from said frequency control circuit, and generating, based at least on the control voltage, a driving signal for controlling said switch.

6. The power supply apparatus of claim 5 , wherein:
said flyback converter further includes a current sensing element that is coupled to said switch and that senses a current flowing through said switch to generate a sensed voltage;
said control unit further includes:
a scaling circuit coupled to said converting circuit for receiving the feedback voltage therefrom, and scaling the feedback voltage by a scaling factor to generate a scaled voltage, and
a first comparator having a first input terminal that is coupled to said current sensing element for receiving the sensed voltage therefrom, a second input terminal that is coupled to said scaling circuit for receiving the scaled voltage therefrom, and an output terminal that provides a result of comparison between the sensed voltage and the scaled voltage; and

said driving circuit is coupled further to said first comparator for receiving the result of the comparison therefrom, and generates the driving signal based further on the result of the comparison from said first comparator.

7. The power supply apparatus of claim 6 , wherein the scaling factor is a constant.

8. The power supply apparatus of claim 6 , wherein said scaling circuit is coupled further to said adjustment control circuit for receiving the control signal therefrom, and the scaling factor changes due to the control signal.

9. The power supply apparatus of claim 6 , wherein said control unit further includes a current compensating circuit that is coupled to said adjustment control circuit and said first input terminal of said first comparator, that receives the control signal from said adjustment control circuit, that generates a compensating current input in response to the control signal, and that outputs the compensating current input to said first input terminal of said first comparator.

10. The power supply apparatus of claim 6 , wherein:
said control unit further includes a second comparator having a first input terminal that is coupled to said converting circuit for receiving the feedback voltage therefrom, a second input terminal that receives a reference voltage, and an output terminal that provides a result of comparison between the feedback voltage and the reference voltage; and
said driving circuit is coupled further to said second comparator for receiving the result of the comparison therefrom, and generates the driving signal based further on the result of the comparison from said second comparator.

11. The power supply apparatus of claim 10 , wherein:
when the result of the comparison from said second comparator indicates that the feedback voltage is lower than the reference voltage, said switch operates in an OFF state; and
when the result of the comparison from said second comparator indicates that the feedback voltage is higher than first reference voltage, said switch alternates between an ON state and the OFF state.

12. The power supply apparatus of claim 11 , wherein said switch transitions from the ON state to the OFF state upon the result of the comparison from said first comparator indicating that the sensed voltage is higher than the scaled voltage.

13. The power supply apparatus of claim 12 , wherein:
said transformer further includes an auxiliary winding that provides an auxiliary voltage; and
said driving circuit is coupled further to said auxiliary winding for receiving the auxiliary voltage therefrom, and generates the driving signal based further on the auxiliary voltage.

14. The power supply apparatus of claim 13 , wherein said switch transitions from the OFF state to the ON when a voltage across said switch is determined, in response to the auxiliary voltage, to reach a valley thereof after a time period has passed, where the time period starts from the latest transition of said switch from the OFF state to the ON state, and equals a reciprocal of a controlled frequency that is a function of the control voltage.

15. The power supply apparatus of claim 5 , wherein said frequency control circuit generates the control voltage increasing with increase of the feedback voltage

Assignees

• Lite On Electronics Guangzhou
• Lite On Tech Corp

Inventors

• Yen Ming-Chuan
• Kung Chih-Hua

Classifications

• H02M1/42

  Circuits or arrangements for compensating for or adjusting power factor in converters or inverters · CPC title

• H02M3/33523

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

• H02M3/33507 Primary

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H03K5/00006

  Changing the frequency (modulating pulses H03K7/00; frequency dividers H03K21/00 - H03K29/00; additive or subtractive mixing of two pulse rates into one G06F7/605; pulse rate dividers G06F7/68) · CPC title

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title