Active startup timing control at fault mode

Patent metadata

Field	Value
Publication number	US-10084370-B2
Application number	US-201715683326-A
Country	US
Kind code	B2
Filing date	Aug 22, 2017
Priority date	Jan 13, 2017
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

A power switch transistor for a switching power converter is maintained on during a re-startup period by a zener breakdown voltage following a fault condition for the switching power converter. A source voltage from the power switch transistor is used to charge a VCC capacitor that stores a power supply voltage for a controller for the switching power converter.

First claim

We claim:

1. A switching power converter, comprising:
a power switch transistor;
a current limiting resistor;
a power supply voltage switch transistor coupled between a source of the power switch transistor and a first terminal for the current limiting resistor;
a VCC capacitor for storing a power supply voltage, wherein the VCC capacitor is coupled between a second terminal for the current limiting resistor and ground;
a zener diode having a cathode coupled to a gate for the power switch transistor and having an anode coupled to ground;
a resistor coupled between an input voltage node for the switching power converter and the cathode of the zener diode; and
a controller configured to control a cycling of the power switch transistor during normal operation to regulate an output voltage for the switching power converter, the controller being further configured to respond to a fault condition by ceasing normal operation and by cycling the power supply voltage switch transistor over a re-startup period, wherein the controller is configured to cycle the power supply voltage switch transistor through a plurality of recycling periods over the re-startup period.

2. The switching power converter of claim 1 , wherein the controller includes a timer, and wherein the controller is configured to begin each recycling period with the power supply voltage switch transistor off during a slow discharge period for the power supply voltage during which the controller receives a first current from the VCC capacitor, and wherein the timer is configured to time the slow discharge period.

3. The switching power converter of claim 2 , wherein the controller is further configured to enter a fast discharge period for the power supply voltage in each recycling period upon completion of the slow discharge period, wherein the controller is further configured to receive a second current from the VCC capacitor during the fast discharge period, and wherein the second current is greater than the first current.

4. The switching power converter of claim 3 , wherein the controller is further configured to enter a fast charge period for the power supply voltage in each recycling period in response to the power supply voltage being less than a low threshold voltage at an end of the fast discharge period, and wherein the controller is configured to switch on the power supply voltage switch transistor during the fast charge period and to end the fast charge period by switching off the power supply voltage switch transistor in response to the power supply voltage being greater than a high threshold voltage.

5. The switching power converter of claim 4 , wherein the controller is further configured to draw substantially no current from the VCC capacitor during each fast charge period.

6. The switching power converter of claim 4 , wherein the controller further includes a voltage control module for controlling the cycling of the power supply voltage switch transistor during the recycling periods.

7. The switching power converter of claim 1 , wherein the power switch transistor and the power supply voltage switch transistor are both NMOS transistors.

8. The switching power converter of claim 1 , wherein a zener breakdown voltage for the zener diode is approximately 15 to 25 volts.

9. A method of controlling a duration of a re-startup period for a switching power converter, comprising:
responding to a fault condition by stopping normal operation of a power switch transistor and beginning the re-startup period, wherein the re-startup period extends over a plurality of recycling periods;
during the re-startup period, driving a gate of the power switch transistor with a zener breakdown voltage from a zener diode to maintain the power switch transistor on;
in each recycling period:
timing a slow discharge period for a power supply voltage stored across a VCC capacitor, wherein a controller powered by the power supply voltage draws a first current from the VCC capacitor;
upon a conclusion of the slow discharge period, drawing a second current from the VCC capacitor to power the controller during a fast discharge period for the power supply voltage, wherein the second current is greater than the first current;
terminating the fast discharge period responsive to the power supply voltage dropping below a low threshold voltage and beginning a fast charge period by charging the VCC capacitor using a source voltage for the power switch transistor; and
completing the fast discharge period responsive to the power supply voltage exceeding a high threshold voltage, wherein the high threshold voltage is greater than the low threshold voltage.

10. The method of claim 9 , wherein the switching power converter is a flyback converter.

11. The method of claim 9 , wherein charging the VCC capacitor using the source voltage comprising switching on a power supply voltage switch transistor to couple the VCC capacitor to a source of the power switch transistor.

12. The method of claim 11 , wherein coupling the VCC capacitor to the source of the power switch transistor comprises coupling the VCC capacitor through a current limiting resistor to the source of the power switch transistor.

13. The method of claim 9 , wherein driving the gate of the power switch transistor with the zener breakdown voltage from the zener diode comprises coupling a cathode of the zener diode to an input voltage node for the switching power converter.

14. The method of claim 13 , wherein coupling the cathode of the zener diode comprises coupling the cathode of the zener diode to the input voltage node through a resistor.

15. A method of controlling a duration of a re-startup period for a switching power converter, comprising:
responding to a fault condition by stopping normal operation of a power switch transistor and beginning the re-startup period, wherein the re-startup period extends over a plurality of recycling periods;
in each recycling period:
charging a gate of a power switch transistor with a zener breakdown voltage to produce a source voltage at a source terminal for the power switch transistor;
during a discharge period, discharging a power supply voltage stored across a VCC capacitor, wherein each discharge period comprises a slow discharge period in which a first current is drawn from the VCC capacitor and a fast discharge period in which a second current is drawn from the VCC capacitor, wherein the second current is greater than the first current; and
charging the VCC capacitor using the source voltage responsive to the power supply voltage dropping below a minimum threshold voltage at an end of the discharge period.

16. The method of claim 15 , wherein the second current equals an operating current for a controller for the switching power converter during normal operation.

17. The method of claim 15 , further comprising: resuming the normal operation upon a completion of the re-startup period.

18. The method of claim 15 , wherein substantially no current is drawn from the VCC capacitor during each fast charge period.

Assignees

• Dialog Semiconductor Inc

Inventors

• Feng Guang
• Kong Pengju
• Chin Kai-Wen
• Peng Mingsheng

Classifications

• H02M1/36 Primary

  Means for starting or stopping converters · CPC title

• H02M1/32 Primary

  Means for protecting converters other than automatic disconnection · CPC title

• H02M3/33507

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

• H02M2001/322

  Electricity · mapped topic

• H02M1/322

  Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock · CPC title