Switching power supplies, and switch controllers for switching power supplies

Patent metadata

Field	Value
Publication number	US-9660539-B2
Application number	US-201615005673-A
Country	US
Kind code	B2
Filing date	Jan 25, 2016
Priority date	Jan 30, 2015
Publication date	May 23, 2017
Grant date	May 23, 2017

Abstract

A switching power supply includes a power converter which includes a transformer and a switch, a current sensor, a switch controller and a compensation resistor. The current sensor is operable for generating a current monitoring signal indicating a current through a primary winding of the transformer. The switch controller is operable for receiving a feedback signal indicating an output voltage of the power converter, generating a driving signal based on the feedback signal to control an input power and an output power of the transformer, receiving a line voltage signal indicating an input voltage of the power converter, and generating a compensation current corresponding to a peak value of the line voltage signal. The compensation resistor is coupled between the current sensor and the switch controller. A voltage of the current monitoring signal is inversely proportional to the input voltage under control of the compensation current and the compensation resistor.

First claim

What is claimed is:

1. A switching power supply comprising:
a power converter comprising a transformer and a switch controlled by a driving signal, said transformer comprising a primary winding operable for receiving an input power from an AC/DC (alternating current/direct current) converter and a secondary winding operable for providing an output power for a load;
a current sensor, coupled between said switch and ground, operable for generating a current monitoring signal indicating a current through said primary winding;
a switch controller, coupled between an optical-coupler and said primary winding, operable for receiving a feedback signal from said optical-coupler, generating said driving signal based on said feedback signal to control said input power and said output power, receiving a line voltage signal indicating an input voltage of said power converter, and generating a compensation current corresponding to a peak value of said line voltage signal, wherein said feedback signal indicates an output voltage of said power converter, and wherein said AC/DC converter is operable for converting an AC voltage to said input voltage and providing said input voltage to said power converter; and
a compensation resistor coupled between said current sensor and said switch controller, wherein a voltage of said current monitoring signal is inversely proportional to said input voltage under control of said compensation current and said compensation resistor, wherein said voltage of said current monitoring signal increases if said input voltage decreases, and wherein said voltage of said current monitoring signal decreases if said input voltage increases,
wherein said switch controller comprises a line voltage compensation unit operable for generating said compensation current based on said line voltage signal, wherein said line voltage compensation unit comprises:
a first counter, operable for generating a first counter value indicating a peak voltage of said line voltage signal during a first cycle;
a second counter, operable for generating a second counter value indicating a peak voltage of said line voltage signal during a second cycle;
a first D/A converter, coupled to said first counter, operable for converting said first counter value to a first analog signal indicating said peak voltage of said line voltage signal during said first cycle;
a second D/A converter, coupled to said second counter, operable for converting said second counter value to a second analog signal indicating said peak voltage of said line voltage signal during said second cycle;
a data selection unit, coupled to said first D/A converter and said second D/A converter, operable for providing a selected analog signal, wherein during said second cycle said data selection unit is operable for selecting said first analog signal as said selected analog signal; and
a voltage/current converter, coupled to said peak voltage detection unit, operable for converting said selected analog signal to said compensation current.

2. The switching power supply of claim 1 , wherein said transformer further comprises an auxiliary winding operable for providing power to said switch controller.

3. The switching power supply of claim 1 , wherein said cycle is 30 milliseconds in length.

4. The switching power supply of claim 1 , wherein said line voltage compensation unit further comprises a comparator and a voltage shifting unit, wherein said comparator has a non-inverting input operable for receiving said line voltage signal and an inverting input coupled to said voltage shifting unit, wherein said voltage shifting unit is operable for providing a threshold, wherein said line voltage compensation unit stops generating said compensation current if said line voltage signal is less than said threshold.

5. The switching power supply of claim 4 , wherein said first counter and said second counter are enabled and disabled based on an output of said comparator, wherein said first counter and said second counter are alternately enabled to count in response to a clock signal if said line voltage signal is greater than said threshold.

6. A switching power supply comprising:
a power converter comprising a transformer and a switch controlled by a driving signal, said transformer comprising a primary winding operable for receiving an input power from an AC/DC (alternating current/direct current) converter and a secondary winding operable for providing an output power for a load;
a current sensor, coupled between said switch and ground, operable for generating a current monitoring signal indicating a current through said primary winding;
a switch controller, coupled between an optical-coupler and said primary winding, operable for receiving a feedback signal from said optical-coupler, generating said driving signal based on said feedback signal to control said input power and said output power, receiving a line voltage signal indicating an input voltage of said power converter, and generating a compensation current corresponding to a peak value of said line voltage signal, wherein said feedback signal indicates an output voltage of said power converter, and wherein said AC/DC converter is operable for converting an AC voltage to said input voltage and providing said input voltage to said power converter;
a compensation resistor coupled between said current sensor and said switch controller, wherein a voltage of said current monitoring signal is inversely proportional to said input voltage under control of said compensation current and said compensation resistor, wherein said voltage of said current monitoring signal increases if said input voltage decreases, and wherein said voltage of said current monitoring signal decreases if said input voltage increases;
a safety capacitor;
at least one diode; and
a discharging switch coupled to said safety capacitor,
wherein said discharging switch is turned on to discharge said safety capacitor through said at least one diode if an AC power source which provides said AC voltage is disconnected from said switching power supply.

7. The switching power supply of claim 6 , further comprising:
a comparator operable for comparing an instant value of said line voltage signal in a first cycle with a voltage value proportional to said peak voltage of said line voltage signal in a second cycle preceding said first cycle;
a counter, controlled by an output from said comparator, operable for generating a counter value and for determining whether said AC power source is disconnected from said switching power supply; and
a latch, coupled to said counter, operable for generating a discharging signal to control said discharging switch based on a status of said counter.

8. The switching power supply of claim 7 , wherein said voltage value is 0.5 times said peak voltage of said line voltage signal.

9. The switching power supply of claim 7 , wherein said counter value remains unchanged if said instant value of said line voltage signal in said first cycle is less than said voltage value proportional to said peak voltage of said line voltage signal in said second cycle, and wherein said latch is operable for generating said discharging signal to turn on said discharging switch if said counter value remains unchanged for a preset time period.

10. A switch controller operable for controlling a power converter comprising a transformer and a switch controlled by a driving signal, said transformer comprising a primary winding operable for receiving an input power from an AC/DC converter (alternating current/direct current) and a secondary winding operable for providing an output power for a load, said switch controller comprising:
a feedback terminal operab

Assignees

• O2Micro Inc
• 02Micro Inc

Inventors

• Ren Zhimou
• Su Ying-Chieh
• Ren Jun
• Kuo Ching-Chuan
• Xie Yunning
• Lin Feng

Classifications

• H02M2001/0009

  Electricity · mapped topic

• H02M2001/0025

  Electricity · mapped topic

• H02M3/33507 Primary

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

• H02M1/0009

  Devices or circuits for detecting current in a converter · CPC title

• H02M1/0025

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