Device for detection of power-off

• US 20050135130A1
• Filed: 11/24/2004
• Published: 06/23/2005
• Est. Priority Date: 12/17/2003
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Gil, Myeong-Ho
• Granted Patent: US 7,285,989 B2
• Time in Patent Office: Days
• US Class Current: 363/125
• CPC Class Codes: G01R 19/145 Indicating the presence of current or voltage
• CPC Class Codes: G06F 1/28 Supervision thereof, e.g. detecting power-supply failure by out of limits supervision
• CPC Class Codes: G06F 1/30 Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations for resetting only G06F1/24

Abstract

A power-off detection device is formed without use of a photo coupler, which is expensive and occupies a relatively large area. The power-off detection device rectifies AC power, provided as external input power from a power supply device, into DC power, detects the power-off of the external input power from the power supply device as provided to an electronic appliance, provides a power-off detection signal to central control means of the electronic appliance, and enables the central control means to prepare for the power-off, thereby reducing manufacturing cost of the power supply device, and achieving miniaturization thereof.

Claims

1. A device for detecting a power-off of external input power from a power supply device, comprising:

a detection unit for generating an induced current in response to an AC current provided by the power supply device;

a voltage supply unit for converting the induced current generated by the detection unit into a detection voltage; and

a voltage comparison unit for comparing the detection voltage provided by the voltage supply unit and a reference voltage, and for providing a power-off detection signal when there is a difference between the detection voltage and the reference voltage.

2. The device according to claim 1, wherein the detection unit comprises a transformer.

3. The device according to claim 2, wherein the transformer includes a first coil which forms a magnetic flux in response to the AC current provided by the power supply device, and a second coil which generates the induced current in response to the magnetic flux formed in the first coil.

4. The device according to claims 3, wherein the second coil is wound in a direction opposite to a direction in which a third coil is wound, said third coil providing a DC voltage to an electronic appliance.

5. The device according to claims 3, wherein the voltage supply unit includes a diode having an anode terminal connected to one end of the second coil, and a capacitor having one end connected to a cathode terminal of the diode and another end connected to another end of the second coil.

6. The device according to claims 5, further comprising a voltage divider connecting the voltage supply unit to a non-inverting input of the voltage comparison unit.

7. The device according to claim 1, wherein the reference voltage is a divided voltage derived from a DC voltage supplied to an electronic appliance by the power supply device.

8. The device according to claim 7, further comprising a voltage divider connected to an inverting input of the voltage comparison unit for providing the divided voltage thereto as the reference voltage.

9. The device according to claim 1, wherein the voltage comparison unit comprises an operational amplifier.

10. The device according to claim 1, further comprising a voltage divider connecting the voltage supply unit to a non-inverting input of the voltage comparison unit.

11. A device for detecting a power-off of an external input power from a power supply device, comprising:

a transformer for generating an induced current in response to AC power provided by the power supply device;

a voltage supply unit for smoothing and rectifying the induced current generated by the transformer to provide a detection voltage; and

a voltage comparison unit for comparing the detection voltage provided by the voltage supply unit and a reference voltage, and for providing a power-off detection signal when there is a difference between the detection voltage and the reference voltage.