AC/DC CONVERTER, AND AC POWER ADAPTER AND ELECTRONIC APPARATUS USING THE SAME

• US 20130027983A1
• Filed: 07/23/2012
• Published: 01/31/2013
• Est. Priority Date: 07/26/2011
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: NATE, Satoru, HAYASHI, Hiroshi
• Granted Patent: US 9,252,669 B2
• Time in Patent Office: Days
• US Class Current: 363/21.01
• CPC Class Codes: H02M 1/322 Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock
• CPC Class Codes: H02M 3/335 using semiconductor devices only

Abstract

The present invention provides an Alternating Current/Direct Current (AC/DC) converter employing measures not only against residual voltage but also to reduce power consumption. The AC/DC converter receives an Alternating Current (AC) voltage through a concentric plug and converts the AC voltage into a Direct Current (DC) voltage. A discharge path is disposed on a path from a discharge terminal to a ground terminal. A detection circuit compares a wave detection voltage with a predetermined threshold voltage, and enables the discharge path to be turned on when the wave detection voltage is continuously lower than the threshold voltage for a predetermined detection time.

Claims

1. An Alternating Current/Direct Current (AC/DC) converter, receiving an Alternating Current (AC) voltage through a concentric plug and converting the AC voltage into a Direct Current (DC) voltage, comprising:

a Live (L) line and a Neutral (N) line, to which the AC voltage is applied;

a filter circuit, comprising at least one capacitor disposed between the L line and the N line, and filtering the AC voltage;

a rectifier and smoothing circuit, rectifying and smoothing an output of the filter circuit; and

a Direct Current/Direct Current (DC/DC) converter, receiving an output voltage of the rectifier and smoothing circuit to generate a DC voltage;

wherein the DC/DC converter comprises;

an output capacitor;

a diode, having a cathode connected to the output capacitor;

a transformer, comprising a primary coil connected to an output terminal of the rectifier and smoothing circuit, and a secondary coil connected to an anode of the diode;

a switching transistor, connected to the primary coil;

a control circuit, controlling the switching transistor; and

a wave detection circuit, generating a wave detection voltage corresponding to an input voltage of the rectifier and smoothing circuit;

wherein the control circuit comprises;

a ground terminal, grounded when in a use state;

a discharge terminal, connected to any of the L line, the N line, and the output terminal of the rectifier and smoothing circuit;

a discharge path, disposed on a path from the discharge terminal to the ground terminal;

a detection terminal, receiving the wave detection voltage generated by the wave detection circuit; and

a detection circuit, comparing the wave detection voltage with a predetermined threshold voltage, and enabling the discharge path to be turned on when the wave detection voltage is continuously lower than the threshold voltage for a predetermined detection time.

2. The AC/DC converter according to claim 1, wherein the detection circuit comprises:

a comparator, comparing the wave detection voltage with the threshold voltage, and generating a valid first comparison signal when the wave detection voltage is lower;

a timer circuit, generating a valid second comparison signal when a valid time of the first comparison signal exceeds the detection time; and

a logic gate, enabling the discharge path to be turned on when the first comparison signal and the second comparison signal are both valid.

3. The AC/DC converter according to claim 1, wherein the control circuit further comprises a power supply terminal receiving a power supply voltage, and the discharge path comprises:

a first discharge switch, disposed between the power supply terminal and the ground terminal, and controlled according to a control signal from the detection circuit; and

a second discharge switch, disposed between the discharge terminal and the power supply terminal, and turned on when an electric potential of the power supply terminal is lower than a predetermined second threshold voltage.

5. An Alternating Current (AC) power adapter, comprising the Alternating Current/Direct Current (AC/DC) converter according to claim 1.

6. An Alternating Current (AC) power adapter, comprising the Alternating Current/Direct Current (AC/DC) converter according to claim 2

7. An Alternating Current (AC) power adapter, comprising the Alternating Current/Direct Current (AC/DC) converter according to claim 3.

9. An electronic apparatus, comprising the Alternating Current/Direct Current (AC/DC) converter according to claim 1.

10. An electronic apparatus, comprising the Alternating Current/Direct Current (AC/DC) converter according to claim 2.

11. An electronic apparatus, comprising the Alternating Current/Direct Current (AC/DC) converter according to claim 3

4. An Alternating Current/Direct Current (AC/DC) converter, receiving an Alternating Current (AC) voltage and converting the AC voltage into a Direct Current (DC) voltage, comprising:

a Live (L) line and a Neutral (N) line, to which the AC voltage is applied;

a filter circuit, comprising at least one capacitor disposed between the L line and the N line, and filtering the AC voltage;

a rectifier and smoothing circuit, rectifying and smoothing an output of the filter circuit; and

a Direct Current/Direct Current (DC/DC) converter, receiving an output voltage of the rectifier and smoothing circuit to generate a DC voltage;

wherein the DC/DC converter comprises;

an output capacitor;

a diode, having a cathode connected to the output capacitor;

a transformer, comprising a primary coil connected to an output terminal of the rectifier and smoothing circuit, and a secondary coil connected to an anode of the diode;

a switching transistor, connected to the primary coil;

a control circuit, controlling the switching transistor; and

a wave detection circuit, generating a wave detection voltage corresponding to an input voltage of the rectifier and smoothing circuit;

wherein the control circuit comprises;

a detection terminal, to which the wave detection voltage generated by the wave detection circuit is applied; and

a detection circuit, comparing the wave detection voltage with a predetermined threshold voltage, and enabling the switching transistor to be turned on when the wave detection voltage is continuously lower than the threshold voltage for a predetermined detection time.

8. An Alternating Current (AC) power adapter, comprising the Alternating Current/Direct Current (AC/DC) converter according to claim 4.

12. An electronic apparatus, comprising the Alternating Current/Direct Current (AC/DC) converter according to claim 4.