OVER VOLTAGE TRANSIENT CONTROLLER

• US 20100007350A1
• Filed: 09/15/2009
• Published: 01/14/2010
• Est. Priority Date: 03/25/2004
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Denning, Bruce S., Li, Guoxing, Liu, Liusheng
• Granted Patent: US 8,232,773 B2
• Time in Patent Office: Days
• US Class Current: 324/427
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation

Abstract

An over voltage transient controller to protect a rechargeable battery from an over voltage transient condition. The over voltage transient controller may comprise a comparator to compare a first signal with a second signal representative of a reference voltage level and to provide an output signal representative of an over voltage transient condition to a switch if the first signal is greater than or equal to the second signal. The switch is responsive to the output signal to protect the rechargeable battery from the over voltage transient condition. The over voltage transient controller may further comprise a DAC, wherein the second signal is based, at least in part, on an output of the DAC. An apparatus comprising a charge switch and such an over voltage transient controller is also provided.

Claims

1. A circuit comprising:

a comparator operable for comparing a monitoring signal indicating a difference between a raw voltage level of a battery pack and an average voltage level of said battery pack to an adjustable reference signal, and for generating a comparison output indicating a condition of said battery pack; and

a control loop coupled to said comparator and operable for receiving said comparison output and for adjusting said adjustable reference signal according to said average voltage level,

wherein said control loop comprises a digital-to-analog converter operable for generating an output signal according to said average voltage level, and wherein said adjustable reference signal is based on said output signal.

2. The circuit of claim 1, wherein said digital-to-analog converter increases said output signal until said comparison output indicates that said monitoring signal is greater than said adjustable reference signal.

3. The circuit of claim 1, further comprising:

a low pass filter operable for receiving a first signal representative of said raw voltage level and for providing a second signal representative of said average voltage level of said battery pack.

4. The circuit of claim 3, further comprising:

a subtraction circuitry coupled to said low pass filter and operable for providing said monitoring signal based on a difference between said first signal and said second signal.

5. An apparatus comprising:

a first switch coupled to a battery pack in series; and

an over voltage transient controller coupled to said first switch and operable for comparing a monitoring signal indicative of a difference between a raw voltage level of said battery pack and an average voltage level of said battery pack to an adjustable reference signal, and for generating a control signal when said monitoring signal is greater than said adjustable reference signal,

wherein said adjustable reference signal is adjusted based on said average battery level, and wherein said first switch responds to said control signal to protect said battery pack from an over voltage transient condition.

6. The apparatus of claim 5, wherein said over voltage transient controller comprises:

a comparator operable for comparing said monitoring signal with said adjustable reference signal for detecting said over voltage transient condition; and

a digital-to-analog converter coupled to said comparator and operable for generating said adjustable reference signal according to said average battery level.

7. The apparatus of claim 6, wherein said digital-to-analog converter increases said output signal until said control signal indicates that said monitoring signal is greater than said adjustable reference signal.

8. The apparatus of claim 5, wherein said over voltage transient controller further comprises:

a low pass filter operable for receiving a first signal representative of said raw voltage level and for providing a second signal representative of said average voltage level of said battery pack; and

a subtraction circuitry coupled to said low pass filter and operable for providing said monitoring signal based on a difference between said first signal and said second signal.

9. The apparatus of claim 5, further comprising:

a second switch coupled in series with said first switch; and

current limiting circuitry operable for controlling an internal resistance of said second switch,

wherein said over voltage transient controller is capable of simultaneously controlling said first switch to protect said battery pack from said over voltage transient condition.

10. The apparatus of claim 5, wherein said over voltage transient controller protects said battery pack from said over voltage transient condition by driving said first switch to an open state.

11. The apparatus of claim 5, wherein said over voltage transient controller protects said battery pack from said over voltage transient condition by increasing an internal resistance of said first switch.

12. A method for detecting an over voltage transient condition of a battery pack, said method comprising:

receiving a monitoring signal indicative of a difference between a raw voltage level of said battery pack and an average voltage level of said battery pack;

generating an adjustable reference signal according to said average battery level by an analog-to-digital conversion; and

generating a control signal representative of said over voltage transient condition if said monitoring signal is greater than said adjustable reference signal.

13. The method of claim 12, further comprising:

providing said control signal to a switch,

switching off said switch in response to said control signal to protect said battery pack from said over voltage transient condition.

14. The method of claim 12, further comprising:

providing said control signal to a switch,

increasing an internal resistance of said switch in response to said control signal to protect said battery pack from said over voltage transient condition.

15. The method of claim 12, further comprising:

receiving a first signal indicating said raw voltage level of said battery pack;

generating a second signal indicating said average voltage level of said battery pack by filtering said raw voltage level;

generating said monitoring signal according to a difference between said first signal and said second signal.