Power-saving circuit for an AC/DC adaptor for a portable computer

• US 6,320,766 B1
• Filed: 12/15/2000
• Issued: 11/20/2001
• Est. Priority Date: 07/31/2000
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Park, Cheol Jin
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US09/736,398
• Time in Patent Office: 340 Days
• Field of Search: 363/20, 363/21.01, 363/21.04, 363/21.09, 363/21.1, 363/97
• US Class Current: 363/21.09
• CPC Class Codes: H02M 1/0019 the disturbance parameters being load current fluctuations
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• 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: 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

A power saving circuit of an AC/DC adaptor for a portable computer including an input until converting an AC voltage into a DC voltage; a power transistor; a transformer inputting the DC voltage and inducing an AC voltage based on the state of the power transistor; an output unit converting the AC voltage into a DC voltage; a feedback unit producing a feedback voltage based on an output voltage of the output unit; a driver outputting a PWM control signal to the power transistor based on the feedback voltage; an output load sensor outputting a sensing signal if a sensed load of the output unit is below a predetermined level; an output voltage dropping unit dropping an output voltage of the output unit based on the sensed signal; and a switching frequency reducer reducing a switching frequency of the PWM control signal based on the sensing signal.

Claims

1. An alternating current/direct current adaptor having a power-saving circuit, comprising:

an input unit for inputting an alternating current voltage from an external alternating current voltage source and for converting the alternating current voltage into a direct current voltage;

a power transistor selectively switched on and off based on a pulse width modulation control signal;

a transformer for inputting the direct current voltage from the input unit to a primary coil of the transformer and for inducing an alternating current voltage at a secondary coil of the transformer based on a switch-on state and a switch-off state of the power transistor;

an output unit for converting the alternating current voltage from the secondary coil of the transformer into a direct current voltage to be output from the output unit;

a feedback unit for producing a feedback voltage based on the direct current voltage output of the output unit;

a driver for outputting to the power transistor the pulse width modulation control signal having a duty ratio controlled based on the feedback voltage from the feedback unit;

an output load sensor for outputting a sensing signal when a sensed load of the output unit is below a predetermined level;

an output voltage dropping unit for receiving the sensing signal when output by the output load sensor and for lowering the direct current voltage output from the output unit based on the sensing signal when the sensing signal is received by the output voltage dropping unit; and

a switching frequency reducer for receiving the sensing signal when output by the output load sensor and for reducing a switching frequency of the pulse width modulation control signal produced from the driver based on the sensing signal when the sensing signal is received by the switching frequency reducer.

2. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 1, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

3. The alternating current/direct current adaptor having a power-saving adaptor as claimed in claim 1, further comprised of the output load sensor being a current sensor.

4. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 3, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

5. The alternating current/direct current adaptor having power-saving circuit as claimed in claim 1, fute comprised of the output voltage dropping unit comprising:

at least one resistor connected between an output line of the output unit and a ground for the alternating current/direct current adaptor; and

a switching device connected in parallel with at the least one resistor and being selectively switched off when the sensing signal is input during the switching device maintaining a switch-on state in a normal operation mode of the alternating current/direct current adaptor.

6. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 5, further comprised of the alternating current direct current adaptor being used for providing a direct current voltage to a portable computer.

7. The alternating current/direct current adaptor having a power saving circuit as claimed in claim 1, further comprised of the switching frequency reducer being connected to an oscillator in the driver, the switching frequency reducer including a resistor and a capacitor for reducing the switching frequency output from the oscillator.

8. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 7, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

9. An alternate current/direct current adaptor having a power-saving circuit, comprising:

an input unit for inputting an alternating current voltage from an external alternating current voltage source and for converting the alternating current voltage into a direct current voltage;

a power transistor selectively switched on and off based on a pulse width modulation control signal;

a transformer for inputting the direct current voltage from the input unit to a primary coil of the transformer and for inducing an alternating current voltage at a secondary coil of the transformer based on a switch-on state and a switch-off state of the power transistor;

a main voltage output unit for converting an alternating current voltage from a first secondary coil of the transformer into a direct current voltage to be output from the main voltage output unit;

a feedback unit for producing a feedback voltage based on one of the direct current voltage output of the main voltage output unit and a direct current voltage output of an auxiliary voltage output unit;

a driver for outputting to the power transistor the pulse width modulation control signal having a duty ratio controlled based on the feedback voltage from the feedback unit;

an output load sensing unit for sensing a load of one of the main voltage output unit and the auxiliary voltage output unit and outputting a sensing signal when the sensed load is below a predetermined level;

an output voltage dropping unit for receiving the sensing signal output by the output load sensing unit and for dropping one of the direct current voltage output from the main voltage output unit and the direct current voltage output from the auxiliary voltage output unit based on the sensing signal when the sensing signal is received by the output voltage dropping unit;

a switching frequency reducer for receiving the sensing signal when output by the output load sensing unit and for reducing a switching frequency of the pulse width modulation control signal produced from the driver based on the sensing signal when the sensing signal is received by the switching frequency reducer;

the auxiliary voltage output unit for converting an alternating current voltage input from a second secondary coil of the transformer into a direct current voltage and outputting the direct current voltage from the auxiliary voltage output unit; and

a main switching unit selectively switched on and off based on the sensing signal when the sensing signal is received by the main switching unit to selectively cut off the direct current voltage output from the main voltage output unit and to supply the direct current voltage output from the auxiliary voltage output unit.

10. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 9, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

11. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 9, further comprised of the output load sensing unit being a current sensor.

12. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 11, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

13. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 9, further comprised of the output voltage dropping unit comprising:

at least one resistor connected between an output line of one of the main voltage output unit and the auxiliary voltage output unit and a ground for the alternating current/direct current adaptor; and

a first switching unit connected in parallel with the at least one resistor and being selectively switched off when the sensing signal is input to the output voltage dropping unit during the first switching unit maintaining a switch-on state in a normal operation mode of the alternating current/direct current adaptor.

17. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 9, further comprised of the main switching unit comprising:

a first switching unit selectively switched off to cut off the direct current voltage output from the main voltage output unit when the sensing signal is input to the main switching unit during the first switching unit maintaining a switch-on state in a normal operation mode of the alternating current/direct current adaptor; and

a second switching unit selectively switched on to supply the direct current voltage output from the auxiliary voltage output unit when the sensing signal is input to the main switching unit during the second switching unit maintaining a switch-off state in the normal operation mode of the alternating current/direct current adaptor.

18. The alternating current/direct current adaptor having a power saving-circuit as claimed in claim 17, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

19. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 9, further comprised of the direct current voltage output from the auxiliary voltage output unit being ten times smaller than the direct current voltage output from the main voltage output unit.

20. The alternating current/direct current adaptor having a power saving circuit is claimed in claim 19, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

14. The alternating current/direct current adaptor having a power-saving circuit as claimed in 13, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

15. The alternating current/direct current adaptor having a power-saving circuit as claimed in 13, further comprised of the main switching unit comprising:

a second switching unit selectively switched off to cut off the direct current voltage output from the main voltage output unit when the sensing signal is input to the main switching unit during the second switching unit maintaining a switch-on state in a normal operation mode of the alternating current/direct current adaptor; and

a third switching unit selectively switched on to supply the direct current voltage output from the auxiliary voltage output unit when the sensing signal is input to the main switching unit during the third switching unit maintaining a switch-off state in the normal operation mode of the alternating current/direct current adaptor.

16. The alternating current/direct current adaptor having a power-saving circuit as claimed in claim 15, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

21. A power saving method in an alternating current/direct current adaptor, comprising the steps of:

outputting a sensing signal by an output load sensor when a sensed load of an output unit of the alternating current/direct current adaptor for converting an alternating current voltage into a direct current voltage is below a predetermined level;

dropping by an output voltage dropping unit a direct current voltage output from the output unit when the sensing signal is output by the output load sensor; and

reducing a switching frequency of a pulse width modulation control signal produced by a driver for driving a power transistor to control inducing an alternating current voltage provided to the output unit when the sensing signal is output by the output load sensor.

22. The method of claim 21, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.

23. The method of claim 21, further comprising the step of selectively switching by a switching unit to cut off a direct current voltage output from a main voltage output unit as the output unit to supply a direct current voltage output from an auxiliary voltage output unit as the output unit when the sensing signal is output from the output load sensor.

24. The method of claim 23, further comprised of the alternating current/direct current adaptor being used for providing a direct current voltage to a portable computer.