Control circuit of isolated converter and switching power supply, and control method for the same

Patent metadata

Field	Value
Publication number	US-9762128-B2
Application number	US-201615130740-A
Country	US
Kind code	B2
Filing date	Apr 15, 2016
Priority date	May 8, 2015
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

Controlling an isolated converter can include: controlling a first voltage signal across the secondary winding according to a wake-up signal to reflect change of an output voltage of the isolated converter; obtaining a second voltage signal representing the first voltage signal at the primary side; controlling the main power switch according to a detection result of the second voltage signal; generating the wake-up signal according to the output voltage and a first threshold voltage when the isolated converter is in a dynamic loading state of a normal operating mode; generating the wake-up signal according to the output voltage and a second threshold voltage when the isolated converter is in a load steady state of a standby operating mode; and generating the wake-up signal according to the output voltage and a third threshold voltage when the isolated converter is in a dynamic loading state of the standby operating mode.

First claim

What is claimed is:

1. A method of controlling an isolated converter comprising a transformer having a primary winding and a secondary winding, a main power switch coupled with said primary winding, and a freewheeling diode coupled with said secondary winding, the method comprising:
a) controlling a first voltage signal across said secondary winding according to a wake-up signal to reflect change of an output voltage of said isolated converter;
b) obtaining a second voltage signal that represents said first voltage signal at said primary side of said isolated converter;
c) detecting said second voltage signal and controlling said main power switch according to a detection result in order to maintain said output voltage at a predetermined value;
d) generating said wake-up signal according to said output voltage and a first threshold voltage when said isolated converter is in a dynamic loading state of a normal operating mode;
e) generating said wake-up signal according to said output voltage and a second threshold voltage when said isolated converter is in a load steady state of a standby operating mode; and
f) generating said wake-up signal according to said output voltage and a third threshold voltage when said isolated converter is in a dynamic loading state of said standby operating mode.

2. The method of claim 1 , further comprising detecting a primary-side feedback signal of said output voltage at said primary side for controlling said main power switch.

3. The method of claim 2 , wherein at least one of a primary-side controller and a secondary-side controller enter a sleep mode when said isolated converter is in said standby operating mode.

4. The method of claim 2 , wherein a pulse width and frequency of said driving signal of said main power switch are increased when said isolated converter is in said dynamic loading state.

5. A control circuit of an isolated converter comprising a transformer having a primary winding and a secondary winding, a main power switch coupled with said primary winding, and a freewheeling diode coupled with said secondary winding, the control circuit comprising:
a) a secondary-side controller configured to generate a wake-up signal according to an output voltage of said isolated converter to control a first voltage signal across said secondary winding to represent change of said output voltage of said isolated converter;
b) said secondary-side controller being configured to generate said wake-up signal according to said output voltage and a first threshold voltage when said isolated converter is in a dynamic loading state of a normal operating mode;
c) said secondary-side controller being configured to generate said wake-up signal according to said output voltage and a second threshold voltage when said isolated converter is in a load steady state of a standby operating mode;
d) said secondary-side controller being configured to generate said wake-up signal according to said output voltage and a third threshold voltage when said isolated converter is in a dynamic loading state of said standby operating mode;
e) a primary-side feedback circuit configured to obtain a second voltage that represents said first voltage signal; and
f) a primary-side controller configured to detect said second voltage signal and to control said main power switch according to a detection result in order to maintain said output voltage of said isolated converter at a predetermined value.

6. The control circuit of claim 5 , wherein said secondary-side controller comprises:
a) a first secondary-side detection circuit configured to detect if said output voltage is smaller than a first threshold voltage, and to generate a first secondary-side detection signal;
b) a second secondary-side detection circuit configured to detect if said output voltage is smaller than a second threshold voltage, and to generate a second secondary-side detection signal;
c) a third secondary-side detection circuit configured to detect if said output voltage is smaller than a third threshold voltage, and to generate said third secondary-side detection signal;
d) a secondary-side mode detection circuit configured to detect a present operating mode of said isolated converter, and to generate a secondary-side mode detection signal; and
e) a wake-up signal generator configured to receive said first secondary-side detection signal, said second secondary-side detection signal, said third secondary-side detection signal, and said secondary-side mode detection signal, and to generate said wake-up signal.

7. The control circuit of claim 6 , wherein said secondary-side controller further comprises a switching circuit coupled with said diode in parallel, and said wake-up signal is configured to control said first voltage signal by controlling the switching state of said switching circuit.

8. The control circuit of claim 6 , wherein said secondary-side mode detection circuit is configured to control said secondary-side controller to enter a sleep mode when said isolated converter is in said standby operating mode.

9. The control circuit of claim 5 , wherein said primary-side controller comprises a pulse signal detection and decoder circuit configured to detect said second voltage signal, and to generate a first primary-side detection signal to control said main power switch.

10. The control circuit of claim 9 , wherein said primary-side controller comprises:
a) a primary-side feedback control circuit configured to detect a primary-side feedback signal of said output voltage, and to generate a second primary-side detection signal to control said main power switch;
b) a pulse width frequency circuit configured to generate a pulse width frequency control signal according to said first primary-side detection signal and said second primary-side detection signal, in order to increase a pulse width and frequency of said driving signal of said main power switch when said isolated converter is in said dynamic loading state; and
c) a driving circuit configured to receive said first primary-side detection signal, said second primary-side detection signal, and said pulse width frequency signal, and to generate said driving signal.

11. The control circuit of claim 10 , wherein said primary-side controller further comprises a primary-side detection circuit configured to detect a present operating mode of said isolated converter, wherein said primary-side controller is configured to enter said sleep mode when said isolated converter is in said standby operating mode.

12. A switching power supply, comprising said transformer and said control circuit of claim 5 .

Assignees

• Silergy Semiconductor Technology Hangzhou Ltd

Inventors

• Zhang Shaobin
• Bai Yongjiang
• Hu Zhiliang
• Li Le
• Dong Jinping

Classifications

• H02M2001/0048

  Electricity · mapped topic

• H02M1/08

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

• Y02B70/1491

  Cross-Sectional Technologies · mapped topic

• Y02B70/16

  Cross-Sectional Technologies · mapped topic

• H02M2001/0032

  Electricity · mapped topic