Switched mode power converter controller with ramp time modulation

Patent metadata

Field	Value
Publication number	US-9246392-B2
Application number	US-201313800769-A
Country	US
Kind code	B2
Filing date	Mar 13, 2013
Priority date	Mar 13, 2013
Publication date	Jan 26, 2016
Grant date	Jan 26, 2016

Abstract

A controller for use in a power converter includes a drive circuit coupled to generate a drive signal to control switching of a power switch to control a transfer of energy from a power converter input to a power converter output. The controller also includes an input for receiving an enable signal including enable events responsive to the power converter output. The drive circuit is coupled to turn ON the power switch in response to the enable events and turn OFF the power switch in response to a power switch current reaching a current limit threshold. A current limit threshold generator is coupled to receive the drive signal from the enable events of the enable signal. The current limit threshold may be a ramp signal and the ramp signal along with the time between enable events may be used to modulate the drive signal.

First claim

What is claimed is:

1. A controller for use in a power converter, comprising:
a drive circuit coupled to generate a drive signal to control switching of a power switch to control a transfer of energy from a power converter input to a power converter output;
an input for receiving an enable signal including enable events responsive to the power converter output, wherein the drive circuit is coupled to turn ON the power switch in response to the enable events and turn OFF the power switch in response to a power switch current reaching a current limit threshold; and
a current limit threshold generator coupled to receive the drive signal from the drive circuit and to vary the current limit threshold in response to the enable events of the enable signal, wherein the current limit threshold generator is coupled to increase, within a current limit threshold range, the current limit threshold by a fixed increase amount during a fixed time period in response to an end of each ON time of the power switch, and wherein the current limit threshold generator is coupled to begin decreasing, within the current limit threshold range, the current limit threshold at a decrease rate after the fixed time period after the end of each ON time of the power switch.

2. The controller of claim 1 , wherein a time between successive enable events of the enable signal is responsive to the power converter output.

3. The controller of claim 1 , wherein the enable events include transitions from one logic state to another logic state in the enable signal.

4. The controller of claim 1 , wherein the current limit threshold generator is coupled to vary the current limit threshold in response to a time between successive enable events of the enable signal over a range of output loads coupled to the power converter output.

5. The controller of claim 1 , wherein the fixed increase amount is less than the current limit threshold range such that a plurality of switching cycles of the power switch is required to cause the current limit threshold generator to vary the current limit threshold from a minimum current limit threshold to a maximum current limit threshold of the current limit threshold range.

6. The controller of claim 1 , wherein the current limit threshold generator is coupled to increase the current limit threshold up to a maximum current limit threshold in response to the end of each ON time of the power switch.

7. The controller of claim 1 , wherein the current limit threshold generator is coupled to decrease the current limit threshold, within the current limit threshold range, as a time between successive enable events increases.

8. The controller of claim 1 , wherein the fixed time period is substantially zero.

9. The controller of claim 1 , wherein the decrease rate is adjusted in response to an input voltage coupled to the power converter input.

10. The controller of claim 9 , wherein the decrease rate is selected from one of a first constant decrease rate and a second constant decrease rate in response to the input voltage.

11. The controller of claim 1 , wherein the drive circuit includes a latch coupled to generate the drive signal and coupled to be set in response to the enable events, wherein the drive circuit further includes a comparator coupled to reset the latch in response to a comparison of a current sense signal representative of the power switch current and the current limit threshold.

12. The controller of claim 1 , wherein the current limit threshold generator includes a monostable multivibrator coupled to generate a one shot pulse to determine the fixed time period, wherein the monostable multivibrator is coupled to receive the drive signal to generate the one shot pulse in response to the end of each ON time of the power switch.

13. A controller for use in a power converter, comprising:
a drive circuit coupled to generate a drive signal to control switching of a power switch to control a transfer of energy from a power converter input to a power converter output;
an input for receiving an enable signal including enable events responsive to the power converter output, wherein the drive circuit is coupled to turn ON the power switch in response to the enable events and wherein the drive circuit is coupled to turn OFF the power switch in response to a power switch current reaching a current limit threshold; and
a current limit threshold generator coupled to receive the drive signal from the drive circuit to generate the current limit threshold, wherein the current limit threshold generator is coupled to increase, within a current limit threshold range, the current limit threshold at an increase rate during a fixed time period after an end of each ON time of the power switch, and wherein the current limit threshold generator is coupled to decrease the current limit threshold, within the current limit threshold range, after the fixed time period at a decrease rate until the power switch current reaches the current limit threshold.

14. The controller of claim 13 , wherein the drive circuit includes a latch coupled to generate the drive signal and coupled to be set in response to the enable events, wherein the drive circuit further includes a comparator coupled to reset the latch in response to a comparison of a current sense signal representative of the power switch current and the current limit threshold.

15. The controller of claim 13 , wherein the current limit threshold generator includes a monostable multivibrator coupled to generate a one shot pulse to determine the fixed time period, wherein the monostable multivibrator is coupled to receive the drive signal to generate the one shot pulse in response to the end of each ON time of the power switch.

16. The controller of claim 13 , wherein the current limit threshold generator includes a capacitor coupled to generate the current limit threshold, wherein the capacitor is coupled to be charged by a first current source during the fixed time period if the current limit threshold is within the current limit threshold range, and wherein the capacitor is coupled to be discharged by a second current source after the fixed time period if the current limit threshold is within the current limit threshold range.

17. The controller of claim 16 , wherein the second current source is coupled to be responsive to an input voltage coupled to the power converter input.

18. The controller of claim 16 , wherein the second current source is coupled to discharge the capacitor at a first rate in response to a first value of the input voltage, and wherein the second current source is coupled to discharge the capacitor at a second rate in response to a second value of the input voltage.

19. The controller of claim 16 , wherein the first current source includes a first current minor coupled between the capacitor and a maximum current limit threshold reference voltage, and wherein the second current source includes a second current minor coupled between the capacitor and a minimum current limit threshold reference voltage.

20. The controller of claim 19 , wherein the first current mirror includes a p-type metal oxide semiconductor field effect transistor (MOSFET) coupled between the capacitor and the maximum current limit threshold reference voltage, and wherein the second current mirror includes an n-type MOSFET coupled between the capacitor and the minimum current limit threshold reference voltage.

21. The controller of claim 13 , wherein a product of the fixed increase rate and the fixed t

Assignees

• Power Integrations Inc

Inventors

• Balakrishnan Balu
• Saint-Pierre Roland Sylvere
• Pham Giao Minh
• Wong Lance M

Classifications

• H02M3/156

  with automatic control of output voltage or current, e.g. switching regulators · CPC title

• H02M3/157

  with digital control · 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

• H02M3/33515

  with digital control · CPC title

• H02M1/08

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