System and method for a switched-mode power supply

Patent metadata

Field	Value
Publication number	US-9543844-B2
Application number	US-201414242357-A
Country	US
Kind code	B2
Filing date	Apr 1, 2014
Priority date	Apr 1, 2014
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

In accordance with an embodiment, a method of operating a switched-mode power supply includes synchronously rectifying a current in a secondary side of the switched-mode power supply by detecting a voltage drop of a secondary winding of a transformer and activating a semiconductor switch coupled to the secondary winding when the voltage drop is detected. The method also includes determining a digital signal transmitting the digital signal to a controller coupled to a primary winding of the transformer by switching the semiconductor switch in accordance with the digital signal.

First claim

What is claimed is:

1. A method of operating a switched-mode power supply, the method comprising:
synchronously rectifying a current in a secondary side of the switched-mode power supply, wherein synchronously rectifying the current comprises detecting a voltage drop of a secondary winding of a transformer, and activating a semiconductor switch coupled to the secondary winding when the voltage drop is detected;
determining a digital signal, wherein determining the digital signal comprises receiving a signal at an input interface and producing the digital signal based on the received signal; and
transmitting the digital signal to a controller coupled to a primary winding of the transformer, wherein transmitting the digital signal comprises switching the semiconductor switch in accordance with the digital signal, wherein the received signal and the transmitted digital signal represent a request for a changed output voltage of the switched-mode power supply that is different from a present output voltage.

2. The method of claim 1 , wherein producing the digital signal further comprises decoding the received signal.

3. The method of claim 1 , wherein the step of switching the semiconductor switch in accordance with the digital signal causes a voltage spike on an auxiliary winding of the transformer.

4. The method of claim 1 , further comprising monitoring an output voltage of the switched-mode power supply, wherein the digital signal is determined based on the monitoring the output voltage.

5. The method of claim 4 , wherein:
monitoring the output voltage comprises comparing the output voltage with a threshold; and
transmitting the digital signal comprises transmitting a wakeup request to the controller.

6. A method of operating a switched-mode power supply, the method comprising:
synchronously rectifying a current in a secondary side of the switched-mode power supply, wherein synchronously rectifying the current comprises detecting a voltage drop of a secondary winding of a transformer, and activating a semiconductor switch coupled to the secondary winding when the voltage drop is detected;
determining a digital signal, wherein determining the digital signal comprises receiving a signal at an input interface and producing the digital signal based on the received signal; and
transmitting the digital signal to a controller coupled to a primary winding of the transformer, wherein transmitting the digital signal comprises switching the semiconductor switch in accordance with the digital signal, wherein
the input interface comprises a Universal Serial Bus (USB) interface comprising a first signal line and a second signal line, and
receiving the signal comprises comparing at least one of the first signal line and the second signal line to a threshold.

7. A method of operating a switched-mode power supply, the method comprising:
synchronously rectifying a current in a secondary side of the switched-mode power supply, wherein synchronously rectifying the current comprises detecting a voltage drop of a secondary winding of a transformer, and activating a semiconductor switch coupled to the secondary winding when the voltage drop is detected;
determining a digital signal;
transmitting the digital signal to a controller coupled to a primary winding of the transformer, wherein transmitting the digital signal comprises switching the semiconductor switch in accordance with the digital signal, wherein the digital signal comprises a first digital signal and a second digital signal;
receiving a signal at an input interface;
producing the first digital signal based on the received signal;
monitoring an output voltage of the switched-mode power supply; and
producing the second digital signal based on monitoring the output voltage.

8. An integrated circuit comprising:
a synchronous rectifier controller configured to be coupled to a secondary winding of a transformer, and configured to be coupled to a control node of a semiconductor switch conductively coupled to the secondary winding of a transformer, wherein the synchronous rectifier controller is configured to detect a voltage drop of the secondary winding of the transformer, and is configured to activate the semiconductor switch when the voltage drop is detected;
a digital interface circuit configured to be coupled to the control node of the semiconductor switch conductively coupled to the secondary winding of the transformer, the digital interface circuit configured to determine a digital signal and to pulse the control node of the semiconductor switch in accordance with the digital signal; and
a plurality of input terminals coupled to the digital interface circuit, wherein the digital interface circuit is configured to receive a digital command from the plurality of input terminals and determine the digital signal based on the digital command.

9. The integrated circuit of claim 8 , further comprising the semiconductor switch.

10. The integrated circuit of claim 8 , further comprising the transformer.

11. The integrated circuit of claim 8 , wherein the synchronous rectifier controller and the digital interface circuit are disposed on a same semiconductor substrate.

12. The integrated circuit of claim 8 , wherein the digital interface circuit comprises a comparator coupled to at least one of the plurality of input terminals.

13. The integrated circuit of claim 12 , further comprising a decoder coupled to an output of the comparator.

14. The integrated circuit of claim 8 , wherein the plurality of input terminals are configured to be coupled to a Universal Serial Bus (USB) interface.

15. The integrated circuit of claim 8 , wherein the digital signal comprises an output voltage request for transmission to a controller coupled to a primary winding of the transformer.

16. The integrated circuit of claim 8 , further comprising an output voltage monitoring circuit coupled to the digital interface circuit and configured to be coupled to an output voltage node of a switched mode power supply at a monitoring input terminal.

17. An integrated circuit comprising:
a synchronous rectifier controller configured to be coupled to a secondary winding of a transformer, and configured to be coupled to a control node of a semiconductor switch conductively coupled to a secondary winding of a transformer, the synchronous rectifier controller configured to detect a voltage drop of the secondary winding of the transformer, and activate the semiconductor switch when the voltage drop is detected;
a digital interface circuit configured to be coupled to the control node of the semiconductor switch conductively coupled to the secondary winding of the transformer, the digital interface circuit configured to determine a digital signal and to pulse the control node of the semiconductor switch in accordance with the digital signal; and
an output voltage monitoring circuit coupled to the digital interface circuit and configured to be coupled to an output voltage node of a switched mode power supply at a monitoring input terminal, wherein
the output voltage monitoring circuit comprises a comparator coupled to the monitoring input terminal, and
a pulse generator having a pulse generator output coupled to the control node of the semiconductor switch, wherein the pulse generator is configured to provide a wakeup request signal at the pulse generator output based on an output of the comparator.

18. The integrated circuit of claim 17 , wherein the wakeup request signal is configured to signal a termination of a burst-off mode and trigger a

Assignees

• Infineon Technologies Austria Ag

Inventors

• Gong Xiao Wu
• Lim Kok Kee

Classifications

• H02M3/33592

  having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer · CPC title

• Y02B70/1475

  Cross-Sectional Technologies · mapped topic

• H02M3/33507 Primary

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

• H02M3/33523

  with galvanic isolation between input and output of both the power stage and the feedback loop · CPC title

• Y02B70/10

  Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes · CPC title