PROTECTION CIRCUIT AND RELATED METHOD

• US 20150077892A1
• Filed: 09/18/2014
• Published: 03/19/2015
• Est. Priority Date: 09/18/2013
• Status: Active Grant

• Current Assignee: Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hon Hai Precision Industry Co., Ltd.
• Inventors: LIN, CHING-CHUNG, CHEN, PIN-HUNG
• Granted Patent: US 9,478,975 B2
• Time in Patent Office: Days
• US Class Current: 361/86
• CPC Class Codes: H02H 9/001 limiting speed of change of electric quantities, e.g. soft switching on or off progressive control of electronic switches for eliminating interferences H03K17/16
• CPC Class Codes: H02H 9/04 responsive to excess voltage lightning arrestors H01C7/12, H01C8/04, H01G9/18, H01T
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection

Abstract

A protection circuit is connected between a power supply for providing a working voltage and a load. The protection circuit comprises an interface, a detecting module connected to the interface, a control module, and a switch module. The control module generates a plus width modulation (PWM) signal with a predetermined duty cycle when the interface interconnects with the load. The switch module periodically turns on and turns off based on the PWM signal with the predetermined duty cycle.

Claims

1. A protection circuit connected between a power supply for providing a working voltage and a load, the protection circuit comprising:

an interface capable of connecting and disconnecting with a load;

a detecting module connected to the interface and configured to generate a trigger signal when the interface connects with the load;

a control module connected to the detecting module and configured to generate a pulse width modulation (PWM) signal with a predetermined duty cycle in response to the trigger signal; and

a switch module connected to the power supply, the control module, and the interface;

wherein the switch module periodically turns on and turns off based on the PWM signal generated by the control module.

2. The protection circuit of claim 1, further comprising a sampling module connected between the switch module and the interface, wherein the sampling module samples the working voltage provided to the load;

the control module adjusts the duty cycle of the PWM signal based on the sampled voltage.

3. The protection circuit of claim 2, wherein the control module presets a first predetermined time period, a second predetermined time period, a plurality of reference voltage, and a plurality of duty cycles corresponding to the reference voltages in an one-to-one relationship;

the control module accumulates a sampling time when receiving the sampled voltage and compares the sampling time with the first predetermined time period;

when the sampling time is less than the first predetermined time period, the control module determines whether the current sampled voltage is equal to the previous sampled voltage;

when the current sampled voltage is equal to the previous sampled voltage, the control module starts to accumulates a detecting time and compares the detecting time with the second predetermined time period;

when the detecting time is greater than the second predetermined time period, the control module controls the switch module to be turned-off continuously.

4. The protection circuit of claim 3, wherein when the current sampled voltage is not equal to the previous sampled voltage, the control module further selects one of the reference voltages corresponding to the current sampled voltage and generates the PWM signal with a specified duty cycle corresponding to the selected reference voltage which is equal to the current sampled voltage.

5. The protection circuit of claim 4, wherein the control module further presets a standard voltage;

when the sampling time is greater than the first predetermined time period, the control module determines whether the current sampled voltage is equal to the standard voltage;

when the current sampled voltage is equal to the standard voltage, the control module controls the switch module to be turned-on continuously.

6. The protection circuit of claim 5, wherein when the current sampled voltage is not equal to the standard voltage, the control module controls the switch module to be turned-off continuously.

7. The protection circuit of claim 3, wherein the reference voltages increase gradually and the time of the second transistor being turned-off becomes greater.

8. The protection circuit of claim 3, wherein the control module further resets the detecting time when the current sampled voltage is not equal to the previous sampled voltage.

9. The protection circuit of claim 1, wherein the switch module comprises a first transistor, a second transistor, a first resistor, a second resistor, a third resistor, and a fourth resistor;

a first electrode of the first transistor is connected to the control module through the first resistor;

a second electrode of the first transistor is grounded;

a third electrode of the first transistor is connected to a first electrode of the second transistor through the third resistor;

a second electrode of the second transistor is connected to the power supply;

a third electrode of the third transistor is connected to the interface;

a terminal of the fourth resistor is connected to the first electrode of the first transistor, and another terminal of the fourth resistor is grounded;

the fourth resistor is connected between the first electrode and the second electrode of the second transistor.

10. A protecting method provided to a protection circuit connected between a power supply and a load, the protecting method comprising:

obtaining a current sampled voltage and starting to accumulate the sampling time;

comparing the sampling time with a first predetermined time period;

determining whether the current sampled voltage is equal to the previous sampled voltage when the sampling time is less than the first predetermined time period;

starting to accumulate the detecting time when the current sampled voltage is equal to the previous sampled voltage;

comparing the detecting time with a second predetermined time period; and

controlling the switch module to be turned-off continuously when detecting time is greater than the second predetermined time period.

11. The protecting method of claim 10, further comprising:

selecting one of the reference voltages corresponding to the current sampled voltage when the current sampled voltage is not equal to the previous sampled voltage; and

generating the PWM signal with a specified duty cycle corresponding to the selected reference voltage.

12. The protecting method of claim 10, further comprising:

determining whether the current sampled voltage is equal to a standard voltage; and

controlling the switch module to be turned-on continuously the current sampled voltage is equal to the standard voltage.

13. A protection circuit connected between a power supply for providing a working voltage and a load, the protection circuit comprising:

an interface capable of interconnecting with the load or disconnecting with the load;

a control module connected to the detecting module; and

a switch module connected to the power supply, the control module, and the interface; and

a sampling module connected between the switch module and the interface;

wherein the sampling module samples the working voltage provided to the load;

the control module adjusts a time of the switch module being turned-on based on the sampled voltage.

14. The protection circuit of claim 13, further comprising detecting module connected to the interface;

wherein the detecting module generates a plus width modulation (PWM) signal with a predetermined duty cycle when the interface interconnects with the load;

the switch module periodically turns on and turns off based on the PWM signal with the predetermined duty cycle, the control module further adjusts the duty cycle of the PWM signal.

15. The protection circuit of claim 13, wherein the control module presets a first predetermined time period, a second predetermined time period, a plurality of reference voltage, and a plurality of duty cycles corresponding to the reference voltages in an one-to-one relationship;

the control module accumulates a sampling time when receiving the sampled voltage and compares the sampling time with the first predetermined time period;

when the sampling time is less than the first predetermined time period, the control module determines whether the current sampled voltage is equal to the previous sampled voltage;

when the current sampled voltage is equal to the previous sampled voltage, the control module starts to accumulates a detecting time and compares the detecting time with the second predetermined time period;

when the detecting time is greater than the second predetermined time period, the control module controls the switch module to be turned-off continuously.

16. The protection circuit of claim 15, wherein when the current sampled voltage is not equal to the previous sampled voltage, the control module further selects one of the reference voltages corresponding to the current sampled voltage and generates the PWM signal with a specified duty cycle corresponding to the selected reference voltage which is equal to the current sampled voltage.

17. The protection circuit of claim 16, wherein the control module further presets a standard voltage;

when the sampling time is greater than the first predetermined time period, the control module determines whether the current sampled voltage is equal to the standard voltage;

when the current sampled voltage is equal to the standard voltage, the control module controls the switch module to be turned-on continuously.

18. The protection circuit of claim 17, wherein when the current sampled voltage is not equal to the standard voltage, the control module controls the switch module to be turned-off continuously.

19. The protection circuit of claim 15, wherein the reference voltages increase gradually and the time of the second transistor being turned-off becomes greater.

20. The protection circuit of claim 15, wherein the control module further resets the detecting time when the current sampled voltage is not equal to the previous sampled voltage.