LLC resonant frequency auto detection

Patent metadata

Field	Value
Publication number	US-10177673-B2
Application number	US-201715803188-A
Country	US
Kind code	B2
Filing date	Nov 3, 2017
Priority date	Jan 11, 2017
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

Generally speaking, a timing circuit helps determine diode conduction time of an LLC converter. In some examples, the circuit includes an LLC converter having a secondary side and a timing circuit, the timing circuit coupled to the LLC converter on the secondary side. The timing circuit includes a first branch, second branch, gate, and microprocessor. The gate is configured to receive an output of the first branch's comparator and a blanking signal from the second branch. The microprocessor is configured to receive, from the gate, a signal and determine, based at least in part on the signal, a diode conduction time for the LLC converter.

First claim

What is claimed is:

1. A circuit comprising:
an LLC converter having a primary side and a secondary side; and
a timing circuit, the timing circuit coupled to the LLC converter on the secondary side and comprising:
a first branch, wherein the first branch includes a comparator having a first input and a second input;
a second branch, wherein the second branch is configured to output a blanking signal;
a gate, wherein the gate is configured to receive an output of the comparator and the blanking signal; and
a microprocessor, wherein the microprocessor is configured to:
receive, from the gate, a signal;
determine, based, at least in part, on the signal, a diode conduction time for the LLC converter; and
update, based on the diode conduction time, one or more registers for switches on the secondary side of the LLC converter.

2. The system of claim 1 , wherein the first input is configured to receive a voltage at a switch.

3. The system of claim 2 , wherein the switch is a transistor on the secondary side of the LLC converter, and wherein the voltage is a potential difference across a drain and a source of the transistor.

4. The system of claim 1 , wherein the signal indicates that diode conduction is occurring in the LLC converter.

5. The system of claim 1 , wherein the second input is configured to receive a reference voltage.

6. The system of claim 1 , wherein the one or more registers clip an on-time of the switches on the secondary side of the LLC converter to a maximum on-time.

7. The system of claim 6 , wherein the microprocessor is configured to update the registers to increase the maximum on-time.

8. The system of claim 1 , wherein the microprocessor is further configured to:
transmit, to a power factor correction circuit on the primary side of the LLC converter, an indication of the diode conduction time.

9. A method for determining diode conduction time of an LLC converter, the method comprising:
receiving, at a comparator of a timing circuit on a secondary side of the LLC converter, a first input and a second input;
receiving, at a gate, an output from the comparator and a blanking signal;
receiving a signal at a microprocessor from the gate;
determining, based at least in part on the signal, a diode conduction time for the LLC converter; and
updating, by the microprocessor, one or more registers for switches on the secondary side of the LLC converter.

10. The method of claim 9 , wherein the receiving the first input comprises receiving a voltage at a switch.

11. The method of claim 10 , wherein the receiving the voltage at the switch comprises receiving the voltage at a transistor on the secondary side of the LLC converter, and wherein the voltage is a potential difference across a drain and a source of the transistor.

12. The method of claim 9 , wherein the receiving the signal comprises receiving indication that diode conduction is occurring in the LLC converter.

13. The method of claim 9 , wherein the receiving the second input comprises receiving a reference voltage.

14. The method of claim 9 , further comprising:
updating, based on the diode conduction time, one or more registers for switches on the secondary side of the LLC converter.

15. The method of claim 14 , further comprising using the one or more registers to clip an on-time of the switches on the secondary side of the LLC converter to a maximum on-time.

16. The method of claim 15 , wherein updating the registers comprises increasing the maximum on-time.

17. The method of claim 9 , further comprising:
transmitting, to a power factor correcting circuit on a primary side of the LLC converter, an indication of the diode conduction time.

18. A circuit comprising:
an LLC converter having a primary side and a secondary side; and
a timing circuit, the timing circuit coupled to the LLC converter on the secondary side and comprising:
a first branch, wherein the first branch includes a comparator having:
a first input configured to receive a voltage at a transistor on the secondary side of the LLC converter, and wherein the voltage is a potential difference across a drain and a source of the transistor, and
a second input configured to receive a reference voltage;

a second branch, wherein the second branch is configured to output a blanking signal;
a gate, wherein the gate is configured to receive an output of the comparator and the blanking signal; and
a microprocessor, wherein the microprocessor is configured to:
receive, from the gate, a signal that indicates diode conduction is occurring in the LLC converter;
determine, based, at least in part, on the signal, a diode conduction time for the LLC converter;
update, based on the diode conduction time, one or more registers for switches on the secondary side of the LLC converter, the one or more registers configured to effect clipping an on-time of the switches on the secondary side of the LLC converter to a maximum on-time.

Assignees

• Texas Instruments Inc

Inventors

• Xu Shanguang
• Bolurian Yitzhak
• Desai Vaibhav Ramakant

Classifications

• H02M3/3376

  with automatic control of output voltage or current · CPC title

• H02M3/33515

  with digital control · CPC title

• H02M2001/0058

  Electricity · mapped topic

• H02M2007/53878

  Electricity · mapped topic

• H02M3/33507

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