Switching mode power supply incorporating power line filter

• US 6,867,575 B2
• Filed: 12/06/2002
• Issued: 03/15/2005
• Est. Priority Date: 12/06/2002
• Status: Active Grant

• Current Assignee: Delta Electronics Incorporated, Delta Electronics Thailand Public Company Limited (Delta Electronics Incorporated)
• Original Assignee: Delta Electronics Incorporated, Delta Electronics Thailand Public Company Limited (Delta Electronics Incorporated)
• Inventors: Jacob D'Cunha, Allwyn
• Primary Examiner(s): Vu, Bao Q.
• Application Number:
  US10/313,292
• Publication Number:
  US 20040109333A1
• Time in Patent Office: 830 Days
• Field of Search: 323/901, 323/908, 363/49, 363/50, 363/44, 363/45, 363/55
• US Class Current: 360/50
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: Y10S 323/901 Starting circuits

Abstract

There is disclosed a switching mode power supply with a reduced EMI effect, comprising a rectifier for converting an AC power supplied by an AC power source into a rectified DC power, a transformer coupled to the rectifier for inputting the DC power from a primary winding and inducing a rectified power to a secondary winding through the primary winding, a switch unit connected in series with the primary winding for converting the DC power supplied to the primary winding into AC power by on/off operations, an output voltage feedback control circuit for providing pulses to drive the switch unit by controlling a switching duty cycle of the switching unit, and a power line filter including a unidirectional current-limiting device such as a diode for reducing differential mode noise appearing between a live supply line and a neutral line from the alternating current power source.

Claims

1. A power supply device comprising:

a rectifier for converting an alternating current power supplied by an alternating current power source into a rectified direct current power;

a power transformer coupled to the rectifier for inputting the rectified direct current power from a primary winding and inducing a rectified power to a secondary winding through the primary winding;

a switch unit connected in series with the primary winding for converting the direct current power supplied to the primary winding into alternating current power by on/off operations; and

a power line filter including a directional current-conducting device for reducing a differential mode noise appearing between a live supply line and a neutral line from the alternating current power source.

2. The power supply device according to claim 1 further comprising an output circuit coupled to the secondary winding of the transformer for providing an output voltage for a load.

3. The power supply device according to claim 2 further comprising an output voltage feedback control circuit for providing pulses to drive the switch unit.

4. The power supply device according to claim 3 wherein the output voltage feedback control circuit further comprises an oscillation circuit for generating a high frequency oscillation signal to serve as a switch control signal for the switch unit.

5. The power supply device according to claim 1 wherein the directional current-conducting device is a unidirectional electronic device.

6. The power supply device according to claim 5 wherein the unidirectional electronic device is a diode.

7. A power supply device, comprising:

a rectifier for converting an alternating current power supplied by an alternating current power source into a rectified direct current power;

a transformer coupled to the rectifier for inputting the rectified direct current power from a primary winding and inducing a rectified power to a secondary winding through the primary winding;

a switch unit connected in series with the primary winding for converting the direct current power supplied to the primary winding into alternating current power by on/off operations;

an output circuit coupled to the secondary winding for providing an output voltage for a load;

an output voltage feedback control circuit coupled to the power transformer and the switch unit for maintaining the output voltage at a predetermined value by regulating a switching duty cycle of the switch unit; and

a power line filter including a unidirectional current-conducting device for reducing a differential mode noise appearing between a live supply line and a neutral line extending from the alternating current power source.

8. The power supply device according to claim 7 wherein the output voltage feedback control circuit further comprises an oscillation circuit for generating a high frequency oscillation signal to serve as a switch control signal for the switch unit.

9. The power supply device according to claim 7 wherein the unidirectional current-conducting device is a diode.