Enabling circuit for avoiding negative voltage transients

• US 6,906,497 B2
• Filed: 12/17/2003
• Issued: 06/14/2005
• Est. Priority Date: 06/20/2002
• Status: Expired due to Fees

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Bucur, Constantin, Niculae, Marian
• Primary Examiner(s): Vu, Bao Q.
• Application Number:
  US10/738,058
• Publication Number:
  US 20040130309A1
• Time in Patent Office: 545 Days
• Field of Search: 320/134, 320/132, 320/166, 323/282
• US Class Current: 320/134
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An enabling circuit includes a comparison circuit configured to compare a feedback signal representative of a charge of an energy storage element of a regulating circuit with a reference charge and provide an output in response to the comparison to enable the regulating circuit to switch from a first state to a second state if the charge of the energy storage element is less than the reference charge. The enabling circuit may also be used to enable a synchronous rectifier converter to provide a charging current to a battery in a battery charging system of an electronic device thereby avoiding negative voltage transients that may otherwise occur at the output of the synchronous rectifier converter. Various methods are also provided.

Claims

1. An enabling circuit for enabling a synchronous rectifier converter having a capacitor coupled to an output terminal of said synchronous rectifier converter, said enabling circuit comprising:

a comparison means for comparing a feedback signal representative of a charge on said capacitor with a signal representative of a reference charge and providing an output to enable said synchronous rectifier converter to switch from a first state to a second state if said charge on said capacitor is less than said reference charge; and

a discharging means, responsive to said comparison means, for discharging said charge on said capacitor if said charge is greater than said reference charge.

2. The enabling circuit of claim 1, wherein said synchronous rectifier converter does not provide a charging current to an associated battery when said synchronous rectifier converter is in said first state and does provide a charging current to said associated battery when said synchronous rectifier converter is in said second state.

3. An enabling circuit for enabling a synchronous rectifier converter having a capacitor coupled to an output terminal of said synchronous rectifier converter, said enabling circuit comprising:

a comparison means for comparing a feedback signal representative of a charge on said capacitor with a signal representative of a reference charge and providing an output signal in response to said comparison;

an output means for receiving at least said output signal from said comparison means and providing an enabling signal to enable said synchronous rectifier converter to switch from a first state to a second state if said charge on said capacitor is less than said reference charge; and

a discharging means, responsive to said comparison means, for discharging said charge on said capacitor if said charge is greater than said reference charge.

4. The enabling circuit of claim 3, wherein said output means is further configured to receive a condition signal and to provide said enabling signal if said charge on said capacitor is less than said reference charge and said condition signal is in a first state.

5. The enabling circuit of claim 3, wherein said discharge means comprises a switching means for providing a path to ground to discharge said capacitor if said charge is greater than said reference charge.

6. A battery charging system comprising:

a synchronous rectifier converter configured to accept an input power level from a power source and provide a regulated output power level to a rechargeable battery, said synchronous rectifier converter having a capacitor coupled to an output terminal of said synchronous rectifier converter; and

an enabling circuit for enabling said synchronous rectifier converter, said enabling circuit comprising;

a comparison means for comparing a feedback signal representative of a charge on said capacitor with a signal representative of a reference charge and providing an output to enable said synchronous rectifier converter to switch from a first state to a second state if said charge on said capacitor is less than said reference charge; and

a discharging means, responsive to said comparison means, for discharging said charge on said capacitor if said charge is greater than said reference charge.

7. The system claim 6, wherein said synchronous rectifier converter does not provide a charging current to said rechargeable battery when said synchronous rectifier converter is in said first state and does provide a charging current to said rechargeable battery when said synchronous rectifier converter is in said second state.

8. An enabling circuit for enabling a synchronous rectifier converter having a capacitor coupled to an output terminal of said synchronous rectifier converter to be controlled by a control signal, said enabling circuit comprising:

a comparison circuit configured to compare a first signal representative of a charge of said capacitor with a second signal representative of a reference charge and provide an output in response to said comparison to enable said synchronous rectifier converter to be controlled by said control signal if said charge on said capacitor is less than said reference charge.

9. The enabling circuit of claim 8, wherein said comparison circuit comprises a comparator.

10. The enabling circuit of claim 8, further comprising:

a discharge path coupled to said capacitor and said comparison circuit, wherein said discharge path is configured to discharge said charge on said capacitor if said charge is greater than said reference charge.

11. The enabling circuit of claim 10, wherein said discharge path comprises at least one switch, said at least one switch configured to close to create a path from said capacitor to ground if said charge on said capacitor is greater than said reference charge.

12. The enabling circuit of claim 8, wherein said control signal comprises a pulse width modulated (PWM) signal.

13. A battery charging system comprising:

a synchronous rectifier converter configured to accept an input power level from a power source and provide a regulated output power level to a rechargeable battery, said synchronous rectifier converter having a capacitor coupled to an output terminal of said synchronous rectifier converter; and

an enabling circuit for enabling said synchronous rectifier converter to be controlled by a control signal, said enabling circuit comprising a comparison circuit configured to compare a first signal representative of a charge of said capacitor with a second signal representative of a reference charge and provide an output in response to said comparison to enable said synchronous rectifier converter to be controlled by said control signal if said charge on said capacitor is less than said reference charge.

14. The system of claim 13, wherein said comparison circuit comprises a comparator.

15. The system of claim 13, wherein said enabling circuit further comprises a discharge path coupled to said capacitor and said comparison circuit, wherein said discharge path is configured to discharge said charge on said capacitor if said charge is greater than said reference charge.

16. The system of claim 15, wherein said discharge path comprises at least one switch, said at least one switch configured to close to create a path from said capacitor to ground if said charge on said capacitor is greater than said reference charge.

17. The system of claim 13, wherein said control signal comprises a pulse width modulated (PWM) signal.

18. A method comprising:

monitoring a charge on a capacitor of a synchronous rectifier converter having a pair of switches;

maintaining said pair of switches in an off state if said charge is greater than a reference charge; and

enabling said pair of switches to be controlled by a control signal if said charge on said capacitor is less than a reference charge.

19. The method of claim 18, further comprising:

discharging said capacitor if said charge is greater than said reference charge.

20. The method of claim 18, wherein said control signal comprises a pulse width modulated (PWM) signal.