Saturation prevention in an energy transfer element of a power converter

Patent metadata

Field	Value
Publication number	US-9401634-B2
Application number	US-201213644822-A
Country	US
Kind code	B2
Filing date	Oct 4, 2012
Priority date	Oct 4, 2012
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

A controller for use in a power converter includes logic circuits to turn on and off a switch to regulate an output quantity. A first integrating capacitor is charged with a combination of a first current and a second current while the switch is turned on. The first current is proportional to a reset voltage and the second current is proportional to an input voltage. A reference generation circuit including a second integrating capacitor is charged with the first current during a previous switching cycle of the switch. The reference generation circuit generates a reference voltage in response to the second integrating capacitor. A comparator provides a stop signal to the logic circuits to turn off the switch in response to a comparison of a voltage across the first integrating capacitor with the reference voltage.

First claim

What is claimed is:

1. A controller for use in a power converter, comprising:
logic circuits to be coupled to turn on and turn off a switch of the power converter to regulate an output quantity of the power converter;
a first integrating capacitor coupled to be charged with a simultaneous combination of a first current from a first current source and a second current from a second current source while the switch is turned on, wherein the first current is proportional to a reset voltage and wherein the second current is proportional to an input voltage of the power converter;
a reference generation circuit including a second integrating capacitor coupled to be charged with a third current from a third current source for an entire switching period of the switch during a previous switching cycle of the switch, wherein the third current is proportional to the reset voltage, wherein the entire switching period of the switch when the second integrating capacitor is charged with the third current is equal to a sum of an off time of the switch and an on time of the switch after the second integrating capacitor is discharged, such that after the second integrating capacitor is discharged the second integrating capacitor is coupled to be charged during the off time of the switch and during the on time of the switch during the previous cycle of the switch, wherein the reference generation circuit is coupled to generate a reference voltage in response to the second integrating capacitor; and
a comparator coupled to provide a stop signal to the logic circuits to turn off the switch in response to a comparison of a voltage across the first integrating capacitor with the reference voltage.

2. The controller of claim 1 wherein the simultaneous combination of the first current and the second current is a sum of the first current and the second current.

3. The controller of claim 1 wherein the first integrating capacitor is coupled to be discharged while the switch is turned off.

4. The controller of claim 1 wherein the first integrating capacitor is coupled to be discharged at an end of a switching cycle of the switch.

5. The controller of claim 1 wherein the reference generation circuit includes a reference capacitor coupled to the second integrating capacitor to store the reference voltage.

6. The controller of claim 5 wherein the second integrating capacitor is coupled to be discharged after the reference voltage is stored in the reference capacitor from the second integrating capacitor.

7. The controller of claim 1 further comprising a pulse width modulator coupled to receive a feedback signal representative of the output quantity of the power converter, the pulse width modulator coupled to generate a pulse width modulation signal in response to the feedback signal coupled to be received by the logic circuits.

8. The controller of claim 1 further comprising an oscillator coupled to provide timing signals, wherein the switch is coupled to be responsive to the timing signals.

9. The controller of claim 1 wherein the switch is one of two active switches coupled to a primary winding of an energy transfer element of the power converter.

10. A controller for use in a power converter, comprising:
logic circuits to be coupled to turn on and turn off a switch of the power converter to regulate an output quantity of the power converter;
a first integrating capacitor coupled to be charged with a first current from a first current source while the switch is turned on, wherein the first current is proportional to a reset voltage of the power converter;
a reference generation circuit including a second integrating capacitor coupled to be charged with a simultaneous combination of a second current from a second current source and a third current from a third current source for an entire switching period of the switch during a previous switching cycle of the switch, wherein the entire switching period of the switch when the second integrating capacitor is charged with the simultaneous combination of the second current and the third current is equal to a sum of an off time of the switch and an on time of the switch after the second integrating capacitor is discharged, such that after the second integrating capacitor is discharged the second integrating capacitor is coupled to be charged during the off time of the switch and during the on time of the switch during the previous cycle of the switch, wherein the second current is proportional to the reset voltage and wherein the third current is proportional to an input voltage of the power converter, wherein the reference generation circuit is coupled to generate a reference voltage in response to the second integrating capacitor; and
a comparator coupled to provide a stop signal to the logic circuits to turn off the switch in response to a comparison of a voltage across the first integrating capacitor with the reference voltage.

11. The controller of claim 10 wherein the simultaneous combination of the second current and the third current is a difference between the second current and the third current.

12. The controller of claim 10 wherein the switch is an active switch coupled to a primary winding of an energy transfer element of the power converter.

13. A power converter, comprising:
an energy transfer element having a primary winding;
a switch coupled to the energy transfer element to selectively apply an input voltage to the primary winding;
a reset circuit coupled to the primary winding; and
a control circuit coupled to the reset circuit and coupled to the switch, wherein the control circuit includes:
logic circuits to be coupled to turn on and turn off the switch to regulate an output quantity of the power converter;
a first integrating capacitor coupled to be charged with a simultaneous combination of a first current from a first current source and a second current from a second current source while the switch is turned on, wherein the first current is proportional to a reset voltage that is responsive to the reset circuit and wherein the second current is proportional to the input voltage;
a reference generation circuit including a second integrating capacitor coupled to be charged with a third current from a third current source for an entire switching period of the switch during a previous switching cycle of the switch, wherein the third current is proportional to the reset voltage, wherein the entire switching period of the switch when the second integrating capacitor is charged with the third current is equal to a sum of an off time of the switch and an on time of the switch after the second integrating capacitor is discharged, such that after the second integrating capacitor is discharged the second integrating capacitor is coupled to be charged during the off time of the switch and during the on time of the switch during the previous cycle of the switch, wherein the reference generation circuit is coupled to generate a reference voltage in response to the second integrating capacitor; and
a comparator coupled to provide a stop signal to the logic circuits to turn off the switch in response to a comparison of a voltage across the first integrating capacitor with the reference voltage.

14. The power converter of claim 13 wherein the simultaneous combination of the first current and the second current is a sum of the first current and the second current.

15. The power converter of claim 13 wherein the first integrating capacitor is coupled to be discharged while the switch is turned off.

16. The power converter of claim 13 wherein the first integra

Assignees

• Power Integrations Inc

Inventors

• Gaknoki Yury
• Mao Mingming
• Mayell Robert J

Classifications

• H02M3/33538

  of the forward type (H02M3/3353, H02M3/33569 take precedence) · CPC title

• H02M3/22

  with intermediate conversion into AC · CPC title

• H02M3/33546

  with automatic control of the output voltage or current (H02M3/33561 takes precedence) · CPC title

• H02M1/40 Primary

  Means for preventing magnetic saturation · CPC title