System and method providing over current protection based on duty cycle information for power converter

• US 10,581,315 B2
• Filed: 12/22/2017
• Issued: 03/03/2020
• Est. Priority Date: 12/08/2010
• Status: Active Grant

• Current Assignee: On-Bright Electronics (Shanghai) Co., Ltd. (Orthosie Investment Holdings Ltd.)
• Original Assignee: On-Bright Electronics (Shanghai) Co., Ltd. (Orthosie Investment Holdings Ltd.)
• Inventors: Yao, Chao, Zhang, Yunchao, Lin, Yuan, Sun, Zhiqiang, Fang, Lieyi
• Primary Examiner(s): Zhang, Jue
• Assistant Examiner(s): Sprenger, Kevin H
• Application Number:
  US15/852,490
• Publication Number:
  US 20180123448A1
• Time in Patent Office: 802 Days
• Field of Search: 363 2112- 2113, 363 2115, 363 2117- 2118, 323273-279, 323281
• CPC Class Codes: H02H 9/025 Current limitation using field effect transistors
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/33515 with digital control

Abstract

System and method for protecting a power converter. An example system controller for protecting a power converter includes a signal generator, a comparator, and a modulation and drive component. The signal generator is configured to generate a threshold signal. The comparator is configured to receive the threshold signal and a current sensing signal and generate a comparison signal based on at least information associated with the threshold signal and the current sensing signal, the current sensing signal indicating a magnitude of a primary current flowing through a primary winding of a power converter. The modulation and drive component is coupled to the signal generator.

Claims

1. A system controller for protecting a power converter, the system controller comprising:

a signal generator configured to generate a threshold signal;

a comparator configured to receive the threshold signal and a current sensing signal and generate a comparison signal based on at least information associated with the threshold signal and the current sensing signal, the current sensing signal indicating a magnitude of a primary current flowing through a primary winding of a power converter; and

a modulation and drive component coupled to the signal generator and configured to receive at least the comparison signal, generate a drive signal based on at least information associated with the comparison signal, and output the drive signal to a switch in order to affect the primary current, the drive signal being associated with one or more first switching periods and a second switching period following the one or more first switching periods, the one or more first switching periods corresponding to one or more first duty cycles;

wherein the signal generator is further configured to, for the second switching period,

determine a first threshold signal value based on at least information associated with the one or more first duty cycles;

generate the threshold signal equal to the determined first threshold signal value, the threshold signal being constant in magnitude as a function of time for the second switching period, the second switching period including an off-time period and an on-time period; and

change, at a beginning of the off-time period, the threshold signal in magnitude;

wherein;

the on-time period begins at a first time and ends at a second time;

the off-time period begins at a third time and ends at a fourth time; and

the second time and the third time are the same.

2. The system controller of claim 1 wherein:

the drive signal is further associated with a third switching period following the one or more first switching periods and the second switching period, the second switching period corresponding to a second duty cycle;

wherein the signal generator is further configured to, for the third switching period,

determine a second threshold signal value based on at least information associated with the second duty cycle; and

generate the threshold signal equal to the determined second threshold signal value, the threshold signal being constant in magnitude as a function of time for the third switching period.

3. The system controller of claim 2 wherein the second threshold signal value is equal to the first threshold signal value.

4. The system controller of claim 2 wherein the second threshold signal value is different from the first threshold signal value.

5. A method for protecting a power converter, the method comprising:

generating a threshold signal;

receiving the threshold signal and a current sensing signal, the current sensing signal indicating a magnitude of a primary current flowing through a primary winding of a power converter;

generating a comparison signal based on at least information associated with the threshold signal and the current sensing signal;

receiving at least the comparison signal;

generating a drive signal based on at least information associated with the comparison signal, the drive signal being associated with one or more first switching periods and a second switching period following the one or more first switching periods, the one or more first switching periods corresponding to one or more duty cycles; and

outputting the drive signal to a switch in order to affect the primary current;

wherein the process for generating a threshold signal includes, for the second switching period,

determining a first threshold signal value based on at least information associated with the one or more duty cycles;

generating the threshold signal equal to the determined first threshold signal value, the threshold signal being constant in magnitude as a function of time for the second switching period, the second switching period including an off-time period and on-time period; and

changing, at a beginning of the off-time period, the threshold signal in magnitude;

wherein;

the on-time period begins at a first time and ends at a second time;

the off-time period begins at a third time and ends at a fourth time; and

the second time and the third time are the same.

6. The method of claim 5 wherein:

the drive signal is further associated with a third switching period following the one or more first switching periods and the second switching period, the second switching period corresponding to a second duty cycle;

wherein the process for generating a threshold signal includes, for the third switching period,

determining a second threshold signal value based on at least information associated with the second duty cycle; and

generating the threshold signal equal to the determined second threshold signal value, the threshold signal being constant in magnitude as a function of time for the third switching period.

7. The method of claim 6 wherein the second threshold signal value is equal to the first threshold signal value.

8. The method of claim 6 wherein the second threshold signal value is different from the first threshold signal value.