Power Converter and Power Conversion Method

Patent metadata

Field	Value
Publication number	US-2017288553-A1
Application number	US-201615087158-A
Country	US
Kind code	A1
Filing date	Mar 31, 2016
Priority date	Mar 31, 2016
Publication date	Oct 5, 2017
Grant date	—

Abstract

In accordance with an embodiment, a method includes disabling a first electronic switch connected in series with a primary winding of a transformer in a power converter circuit if an auxiliary voltage across an auxiliary winding of the transformer is outside a predefined voltage range. The power converter circuit further includes a secondary winding of the transformer, and a rectifier circuit connected between the secondary winding and an output, where the rectifier circuit comprises a second electronic switch.

First claim

1 . A power converter circuit comprising:
a transformer comprising a primary winding, a secondary winding, and an auxiliary winding; a first electronic switch connected in series with the primary winding; a rectifier circuit connected between the secondary winding and an output, wherein the rectifier circuit comprises a second electronic switch; and a first control circuit, wherein the first control circuit is configured to
evaluate an auxiliary voltage across the auxiliary winding during a waiting time after the transformer has been demagnetized in one drive cycle and before the first electronic switch switches on in a next drive cycle, and
disable the first electronic switch if the auxiliary voltage, during the waiting time, is outside a predefined voltage range.

2 . The power converter circuit of claim 1 , wherein the first control circuit is configured to define a plurality of targeted drive cycles,
operate the first electronic switch in a plurality of actual drive cycles by a drive signal, wherein each of the plurality of actual drive cycles comprises an on-period and an off-period of the first electronic switch, and generate the drive signal based on the plurality of targeted drive cycles and the auxiliary voltage.

3 . The power converter circuit of claim 2 ,
wherein the power converter circuit further comprises a feedback circuit coupled to the output and configured to generate a feedback signal based on an output signal available at the output, and wherein the first control circuit is further configured to operate the power converter circuit in one of a first operation mode and a second operation mode based on the feedback signal.

4 . The power converter circuit of claim 3 , wherein the first operation mode is a fixed frequency mode and the second operation mode is a variable frequency mode.

5 . The power converter circuit of claim 4 , wherein the first control circuit is configured,
in the fixed frequency mode, to define a frequency at which the targeted drive cycles occur based on an oscillation signal provided by an oscillator, in the variable frequency mode, to define a frequency at which the targeted drive cycles occur based on the feedback signal and the auxiliary voltage.

6 . The power converter circuit of claim 5 , wherein in the variable frequency mode the first control circuit is configured in the off-period of the first electronic switch to detect threshold crossings when the auxiliary voltage crosses a predefined threshold, select one of these times based on the feedback signal, and start an on-period of a targeted drive cycle based on the selected time.

7 . The power converter circuit of claim 6 , wherein the first control circuit is configured to start the on-period of the targeted drive cycle based on the selected time and based on a time period between two successive threshold crossings.

8 . The power converter circuit of claim 6 , wherein the first control circuit is configured to
detect local minima of a voltage across the first electronic switch, select one of the local minima based on the feedback signal, and start an on-period of a targeted drive cycle at a time of the selected local minimum, wherein detecting local minima of the voltage across the first electronic switch comprises detecting local extrema of the auxiliary voltage.

9 . The power converter circuit of claim 2 , wherein the first control circuit is further configured to
generate a disable signal based on the auxiliary voltage across the auxiliary winding, generate a targeted drive signal that represents the plurality of targeted drive cycles, and generate the drive signal based on the disable signal and the targeted drive signal.

10 . The power converter circuit of claim 1 , wherein the rectifier circuit further comprises a second control circuit configured to control the second electronic switch based on a voltage across the second electronic switch.

11 . The power converter circuit of claim 10 , wherein the second control circuit is configured to
switch on the second electronic switch when the voltage across the second electronic switch has a first polarity and the absolute value of the voltage rises above a first threshold, and switch off the second electronic switch when the voltage across the second electronic switch has a first polarity and the absolute value of the voltage falls below a second threshold lower than the first threshold.

12 . The power converter circuit of claim 10 , wherein the rectifier circuit further comprises an auxiliary power supply configured to supply power to the second control circuit,
wherein the auxiliary power supply comprises an auxiliary winding of the transformer.

13 . The power converter circuit of claim 1 , wherein the primary winding and the secondary winding have opposite winding senses.

14 . The power converter circuit of claim 13 , wherein the primary winding and the auxiliary winding have opposite winding senses.

15 . A method comprising:
disabling a first electronic switch connected in series with a primary winding of a transformer in a power converter circuit if, during a waiting time after the transformer has been demagnetized in one drive cycle and before the first electronic switch switches on in an next drive cycle, an auxiliary voltage across an auxiliary winding of the transformer is outside a predefined voltage range, wherein the power converter circuit further comprises: a secondary winding of the transformer, and a rectifier circuit connected between the secondary winding and an output, wherein the rectifier circuit comprises a second electronic switch.

16 . The method of claim 15 , further comprising:
defining a plurality of targeted drive cycles, operating the first electronic switch in a plurality of actual drive cycles by a drive signal, wherein each of the plurality of actual drive cycles comprises an on-period and an off-period of the first electronic switch, and generating the drive signal based on the plurality of targeted drive cycles and the auxiliary voltage.

17 . The method of claim 16 , further comprising:
generating a feedback signal based on an output signal available at the output, and operating the power converter circuit in one of a first operation mode and a second operation mode based on the feedback signal.

18 . The method of claim 17 , wherein the first operation mode is a fixed frequency mode and the second operation mode is a variable frequency mode.

19 . The method of claim 18 ,
wherein operating the power converter circuit in the fixed frequency mode comprises defining a frequency at which the targeted drive cycles occur based on an oscillation signal provided by an oscillator, and wherein operating the power converter circuit in the variable frequency mode comprises defining a frequency at which the targeted drive cycles occur based on the feedback signal and the auxiliary voltage.

20 . The method of claim 19 , wherein operating the power converter circuit in the variable frequency mode comprises, detecting threshold crossings when the auxiliary voltage crosses a predefined threshold in the off-period of the first electronic switch, selecting one of these times based on the feedback signal, and starting an on-period of a targeted drive cycle based on the selected time.

21 . The method of claim 20 , further comprising:
starting the on-period of the targeted drive cycle based on the selected time and based on a time period between two successive thresho

Assignees

• Infineon Technologies Austria Ag

Inventors

• Fahlenkamp Marc
• Krueger Martin

Classifications

• H02M1/08

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

• H02M3/33515 Primary

  with digital control · CPC title

• H02M2001/0009

  Electricity · mapped topic

• H02M1/0009

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

• H02M1/0058

  by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero (using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826) · CPC title