Monitoring and control circuit for adjusting current

• US 8,598,855 B2
• Filed: 12/15/2008
• Issued: 12/03/2013
• Est. Priority Date: 03/12/2008
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Bucur, Constantin, Goh, Jiun Heng, Lupy, Flavius
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Quddus, Nusrat
• Application Number:
  US12/316,690
• Publication Number:
  US 20100327829A1
• Time in Patent Office: 1,814 Days
• Field of Search: 363/20, 363/21.01, 363/21.1, 363/21.11, 363/53, 363/56.03, 363/56.04, 363/56.05, 363/56.09, 363/56.1, 363/56.11, 363/80, 363/127, 323273-284
• US Class Current: 323/282
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter

Abstract

A monitoring and control circuit comprises a sense block, a first and a second comparators, and a control module. The current sense block is coupled to a switch for generating a monitoring signal indicative of a current flowing through the switch. The first comparator coupled to the sense block is operable for comparing the monitoring signal to a first threshold and for providing a first signal according to a first comparison result between the monitoring signal and the first threshold. The second comparator coupled to the sense block is operable for comparing the monitoring signal to a second threshold and for providing a second signal according to a second comparison result between the monitoring signal and the second threshold. The control module coupled to the first comparator and the second comparator provides a control signal for controlling the switch according to the first signal and the second signal so as to adjust the current.

Claims

1. A monitoring and control circuit, comprising:

a terminal operable for providing a monitoring signal indicative of a current flowing through a switch;

comparator circuitry coupled to said terminal and operable for comparing said monitoring signal to a first threshold to provide a first signal according to the comparison between said monitoring signal and said first threshold, and operable for comparing said monitoring signal to a second threshold to provide a second signal according to the comparison between said monitoring signal and said second threshold; and

a control module coupled to said switch and said comparator circuitry and operable for providing a control signal to control said switch to operate in a normal mode or a protection mode according to said first signal and said second signal so as to adjust said current, wherein in said protection mode, said control signal turns on and off said switch alternately to reduce said monitoring signal from said first threshold to said second threshold.

2. The monitoring and control circuit of claim 1, wherein said comparator circuitry comprises a comparator that provides said first signal if said monitoring signal is greater than said first threshold.

3. The monitoring and control circuit of claim 1, wherein said comparator circuitry comprises a comparator that provides said second signal if said monitoring signal is less than said second threshold.

4. The monitoring and control circuit of claim 1, wherein said monitoring signal comprises a voltage signal indicative of an average level of said current.

5. The monitoring and control circuit of claim 4, further comprising:

a sense resistor coupled to said switch and operable for converting said current to a sensed voltage;

a low pass filter coupled to said sense resistor and operable for providing an average voltage according to said sensed voltage; and

an operational amplifier coupled to said low pass filter and operable for amplifying said average voltage to said voltage signal.

6. The monitoring and control circuit of claim 1, wherein said switch comprises a parasitic resistor operable for converting said current to a sensed voltage.

7. The monitoring and control circuit of claim 1, wherein said control signal comprises a pulse width modulation (PWM) signal to turn on and off said switch alternately.

14. The monitoring and control circuit of claim 1, wherein said control module alternately enables and disables said switch to reduce said current if a level of said current is greater than a first current threshold.

15. The monitoring and control circuit of claim 1, wherein said control module enables said switch if a level of said current decreases to a second current threshold.

18. The monitoring and control circuit of claim 1, wherein in said normal mode, said control signal maintains said switch on.

19. The monitoring and control circuit of claim 7, wherein said second threshold divided by a duty cycle of said PWM signal is less than said first threshold.

8. A protection circuit comprising:

a terminal operable for providing a monitoring signal indicative of a current flowing through a switch;

a mode selector coupled to said terminal and operable for selecting a mode from at least a normal mode and a protection mode by comparing said monitoring signal with a first threshold and a second threshold, and operable for generating a mode signal; and

a control module coupled to said mode selector and operable for providing a control signal to control said switch according to said mode signal, wherein in said protection mode, said control signal turns on and off said switch alternately to reduce said monitoring signal from said first threshold to said second threshold.

9. The protection circuit of claim 8, wherein said mode selector comprises:

a first comparator operable for comparing said monitoring signal to said first threshold and operable for providing a first signal according to a first comparison result between said monitoring signal and said first threshold; and

a second comparator operable for comparing said monitoring signal to said second threshold and operable for providing a second signal according to a second comparison result between said monitoring signal and said second threshold.

10. The protection circuit of claim 9, wherein said mode signal comprises at least one of said first and said second signal.

11. The protection circuit of claim 8, wherein said control signal comprises a PWM signal to turn on and off said switch alternately.

16. The protection circuit of claim 8, wherein said mode selector selects said protection mode if said monitoring signal is greater than said first threshold.

17. The protection circuit of claim 8, wherein said mode selector selects said normal mode if said monitoring signal is less than said second threshold.

20. The protection circuit of claim 8, wherein in said normal mode, said control signal maintains said switch on.

21. The protection circuit of claim 11, wherein said second threshold divided by a duty cycle of said PWM signal is less than said first threshold.

12. A method for adjusting a current, comprising:

controlling said current to flow through a switch;

generating a monitoring signal indicative of said current;

generating a control signal according to comparison between said monitoring signal and a first threshold and according to comparison between said monitoring signal and a second threshold;

controlling said switch to operate in a normal mode or a protection mode, using said control signal, so as to adjust said current; and

in said protection mode, alternately turning on and off said switch to reduce said monitoring signal from said first threshold to said second threshold.

13. The method of claim 12, wherein said control signal comprises a pulse width modulation (PWM) signal to turn on and off said switch alternately.

22. The method of claim 12, further comprising:

maintaining said switch on in said normal mode.

23. The method of claim 13, wherein said second threshold divided by a duty cycle of said PWM signal is less than said first threshold.