DC converter

• US 20060209571A1
• Filed: 02/21/2006
• Published: 09/21/2006
• Est. Priority Date: 02/25/2005
• Status: Active Grant

• Current Assignee: Sanken Electric Company Limited
• Original Assignee: Sanken Electric Company Limited
• Inventors: Aso, Shinji, Tsuruya, Mamoru, Sato, Makoto
• Granted Patent: US 7,525,822 B2
• Time in Patent Office: Days
• US Class Current: 363/21.10
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• 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 DC converter has a transformer with loosely coupled primary and secondary windings, a main switch connected in series with the primary winding of the transformer, and a series circuit connected to ends of one of the primary winding and main switch. The series circuit includes a clamp capacitor and an auxiliary switch. The main and auxiliary switches are alternately turned on/off so that a voltage of the secondary winding of the transformer is synchronously rectified with synchronous rectifiers and is smoothed with smoothing elements, to provide a DC output. The DC converter also includes a tertiary winding provided for the transformer, tightly coupled with the primary winding, and configured to generate a voltage that drives the synchronous rectifiers.

Claims

1. A DC converter having a transformer including primary and secondary windings that are loosely coupled with each other, a main switch connected in series with the primary winding, and a series circuit connected to ends of one of the primary winding and main switch and including a clamp capacitor and an auxiliary switch, the main and auxiliary switches being alternately turned on/off so that a voltage of the secondary winding of the transformer is synchronously rectified with synchronous rectifiers and is smoothed with smoothing elements to provide a DC output, the DC converter comprising

a tertiary winding provided for the transformer, tightly coupled with the primary winding, and configured to generate a voltage that drives the synchronous rectifiers.

3. The DC converter of claim 1, further comprising

a first capacitor connected in series with the tertiary winding of the transformer and configured to drive the synchronous rectifiers through the first capacitor.

5. The DC converter of claim 3, further comprising

a second capacitor connected in parallel with a drive terminal of each of the synchronous rectifiers.

2. A DC converter having a transformer including a primary winding, a first secondary winding very loosely coupled with the primary winding, and a second secondary winding loosely coupled with the primary winding, a main switch connected in series with the primary winding, and a series circuit being connected to ends of one of the primary winding and main switch and including a clamp capacitor and an auxiliary switch, the main and auxiliary switches being alternately turned on/off so that, energy is accumulated in a leakage inductance between the primary winding and the first secondary winding as the main switch is ON, the accumulated energy being transferred through the second secondary winding to a secondary side of the transformer as the main switch is OFF, and a voltage of the secondary windings being synchronously rectified with synchronous rectifiers and smoothed with smoothing elements to provide a DC output, the DC converter comprising

a tertiary winding provided for the transformer, tightly coupled with the primary winding, and configured to generate a voltage that drives the synchronous rectifiers.

4. The DC converter of claim 2, further comprising

a first capacitor connected in series with the tertiary winding of the transformer and configured to drive the synchronous rectifiers through the first capacitor.

6. The DC converter of claim 4, further comprising

a second capacitor connected in parallel with a drive terminal of each of the synchronous rectifiers.