SYSTEM AND METHOD PROVIDING RELIABLE OVER CURRENT PROTECTION FOR POWER CONVERTER

• US 20170163026A1
• Filed: 12/15/2016
• Published: 06/08/2017
• Est. Priority Date: 02/02/2015
• 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: Fang, Lieyi, Huang, Xiaomin, Kang, Xiaozhi, Lin, Yuan, Lyu, Huawei, Yang, Dongze
• Granted Patent: US 10,211,626 B2
• Time in Patent Office: Days
• CPC Class Codes: H02H 7/12 for static converters or rectifiers for discharge lamp power supplies using static converters H05B41/2851, H05B41/2921, H05B41/2981
• CPC Class Codes: H02H 7/125 for rectifiers
• 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 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• 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 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop

Abstract

System controller and method for protecting a power converter. The system controller includes a first controller terminal configured to output a drive signal to a switch to affect a first current flowing through a primary winding of a power converter. The power converter further includes a secondary winding coupled to the primary winding, and the drive signal is associated with one or more switching periods. Additionally, the system controller includes a second controller terminal configured to receive a sensing voltage from a sensing resistor. The sensing voltage represents a magnitude of the first current flowing through the primary winding of the power converter. The system controller is configured to process information associated with the sensing voltage and a reference voltage, and determine whether an average output current of the power converter is larger than a current threshold.

Claims

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

a first controller terminal configured to output a drive signal to a switch to affect a first current flowing through a primary winding of a power converter, the power converter further including a secondary winding coupled to the primary winding, the drive signal being associated with one or more switching periods; and

a second controller terminal configured to receive a sensing voltage from a sensing resistor, the sensing voltage representing a magnitude of the first current flowing through the primary winding of the power converter;

wherein the system controller is configured to;

process information associated with the sensing voltage and a reference voltage;

determine whether an average output current of the power converter is larger than a current threshold, the average output current of the power converter being related to a second current flowing through the secondary winding; and

in response to the average output current being larger than the threshold current, generate the drive signal to cause the switch open and remain open to protect the power converter;

wherein the current threshold is equal to a first ratio multiplied by a second ratio, the first ratio being equal to a first number of turns of the primary winding divided by a second number of turns of the secondary winding, the second ratio being equal to the reference voltage divided by a resistance of the sensing resistor.

2. The system controller of claim 1 is further configured to, in response to the average output current being larger than the threshold current, generate the drive signal to cause the switch to be opened without any modulation.

3. The system controller of claim 1 is further configured to, in response to the average output current being larger than the threshold current, generate the drive signal to cause the switch to remain open for a period of time larger in duration than one of the one or more switching periods.

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

a modulation and drive component configured to generate a drive signal and output the drive signal to a switch to affect a first current flowing through a primary winding of a power converter, the power converter further including a secondary winding coupled to the primary winding, the drive signal being associated with one or more switching periods;

an over-current-protection component configured to receive the drive signal from the modulation and drive component, receive a sensing voltage from a sensing resistor, receive a demagnetization signal, and generate a protection signal based at least in part on the drive signal, the sensing voltage, and the demagnetization signal, the sensing voltage representing a magnitude of the first current flowing through the primary winding of the power converter, the demagnetization signal being associated with one or more demagnetization periods;

wherein;

the over-current-protection component is further configured to determine whether an average output current of the power converter is larger than a current threshold based at least in part on the drive signal, the sensing voltage, and the demagnetization signal, and in response to the average output current of the power converter being determined to be larger than the current threshold, change the protection signal from a first logic level to a second logic level; and

the modulation and drive component is further configured to receive the protection signal, and in response to the protection signal being at the second logic level, generate the drive signal to cause the switch open and remain open to protect the power converter;

wherein the average output current of the power converter is related to a second current flowing through the secondary winding.

5. The system controller of claim 4 wherein the current threshold is equal to a first ratio multiplied by a second ratio, the first ratio being equal to a first number of turns of the primary winding divided by a second number of turns of the secondary winding, the second ratio being equal to a reference voltage divided by a resistance of the sensing resistor.

6. The system controller of claim 4 wherein the modulation and drive component is further configured to, in response to the protection signal being at the second logic level, generate the drive signal to cause the switch to be opened without any modulation.

7. The system controller of claim 4 wherein the modulation and drive component is further configured to, in response to the protection signal being at the second logic level, generate the drive signal to cause the switch to remain open for a period of time larger in duration than one of the one or more switching periods.

8. The system controller of claim 4 wherein the over-current-protection component includes:

a sample-and-hold component configured to receive the drive signal and the sensing signal and generate a first signal based at least in part on the drive signal and the sensing signal;

an integration component configured to receive the first signal and the demagnetization signal and generate a second signal based at least in part on the first signal, the demagnetization signal, and a reference voltage;

a comparator configured to receive the second signal and a threshold signal and generate a comparison signal based at least in part on the second signal and the threshold signal; and

a timer component configured to receive the comparison signal and generate the protection signal based at least in part on the comparison signal.

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

a first controller terminal configured to provide a drive signal to a switch to affect a first current flowing through a primary winding of a power converter, the drive signal being associated with one or more switching periods; and

a second controller terminal configured to receive one or more input signals during the one or more switching periods;

wherein the system controller is configured to;

process information associated with the one or more input signals;

determine whether a temperature associated with the power converter is larger than a predetermined temperature threshold based at least in part on the one or more input signals;

in response to the temperature associated with the power converter being larger than the predetermined temperature threshold, generate the drive signal to cause the switch open and remain open to protect the power converter;

wherein the system controller is further configured to;

process information associated with the one or more input signals;

determine whether an output voltage associated with a secondary winding of the power converter is larger than a predetermined voltage threshold based at least in part on the one or more input signals; and

in response to the output voltage associated with the secondary winding of the power converter being larger than the predetermined voltage threshold, generate the drive signal to cause the switch to open and remain open to protect the power converter;

wherein the system controller is further configured to;

process information associated with the one or more input signals;

generate a demagnetization signal based at least in part on the one or more input signals;

wherein, for each of the one or more switching periods,

the demagnetization signal represents a demagnetization period related to a demagnetization process; and

the demagnetization signal is at a first logic level during the demagnetization period and at a second logic level outside the demagnetization period.

10. The system controller of claim 9 is further configured to:

process information associated with the one or more input signals and the drive signal; and

generate the demagnetization signal based at least in part on the one or more input signals and the drive signal.

11. The system controller of claim 9 wherein:

the first logic level is a logic high level; and

the second logic level is a logic low level.

12. The system controller of claim 9 is further configured to, in response to the temperature associated with the power converter being larger than the predetermined temperature threshold, generate the drive signal to cause the switch to be opened without any modulation.

13. The system controller of claim 9 is further configured to, in response to the temperature associated with the power converter being larger than the predetermined temperature threshold, generate the drive signal to cause the switch to remain open for a first period of time larger in duration than one of the one or more switching periods.

14. The system controller of claim 9 is further configured to, in response to the output voltage associated with the secondary winding of the power converter being larger than the predetermined voltage threshold, generate the drive signal to cause the switch to be opened without any modulation.

15. The system controller of claim 9 is further configured to, in response to the output voltage associated with the secondary winding of the power converter being larger than the predetermined voltage threshold, generate the drive signal to cause the switch to remain open for a first period of time larger in duration than one of the one or more switching periods.

16. The system controller of claim 9, and further comprising a demagnetization detection component configured to:

process information associated with the one or more input signals;

generate the demagnetization signal based at least in part on the one or more input signals.

17. The system controller of claim 16 wherein the demagnetization detection component includes:

a signal differential component configured to receive the one or more input signals and generate a first output signal;

a comparator component configured to receive the first output signal and a reference signal and generate a comparison signal based at least in part on the first output signal and the reference signal; and

a signal processing component configured to receive the comparison signal and generate the demagnetization signal based at least in part on the comparison signal.

18. The system controller of claim 17 wherein the signal processing component is further configured to receive the drive signal and generate the demagnetization signal based at least in part on the comparison signal and the drive signal.

19. The system controller of claim 16 wherein the demagnetization detection component includes:

a comparator configured to receive a first processed signal and a second processed signal and generate a first output signal based at least in part on the first processed signal and the second processed signal, both the first processed signal and the second processed signal being related to the one or more input signals; and

a signal processing component configured to receive the comparison signal and generate the demagnetization signal based at least in part on the comparison signal.

20. The system controller of claim 19 wherein the signal processing component is further configured to receive the drive signal and generate the demagnetization signal based at least in part on the comparison signal and the drive signal.

21-38. -38. (canceled)