Switching power supply apparatus with active clamp circuit

• US 20010036091A1
• Filed: 04/26/2001
• Published: 11/01/2001
• Est. Priority Date: 04/28/2000
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yasumura, Masayuki
• Granted Patent: US 6,356,465 B2
• Time in Patent Office: Days
• US Class Current: 363/21.02
• CPC Class Codes: H02M 3/3385 with automatic control of output voltage or current H02M3/33561 takes 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

An active clamp circuit is provided on the primary side of a complex resonance type switching converter having a parallel resonant circuit on the primary side and a parallel resonant circuit or a series resonant circuit on the secondary side. The active clamp circuit clamps a parallel resonance voltage pulse generated across a primary-side parallel resonant capacitor to thereby lower the level of the parallel resonance voltage pulse. Thus, withstand voltage of components such as switching devices and the primary-side parallel resonant capacitor can be lowered.

Claims

1. A switching power supply circuit comprising:

switching means including a main switching device for interrupting an inputted direct-current input voltage for output;

a primary-side parallel resonant capacitor for forming a primary-side parallel resonant circuit that converts operation of said switching means into voltage resonance type operation;

an isolating converter transformer for transmitting an output of said switching means obtained in a primary winding of the isolating converter transformer to a secondary winding thereof, the isolating converter transformer being formed so as to have loose coupling at a required coupling coefficient between the primary winding and the secondary winding;

a secondary-side resonant circuit formed by connecting a secondary-side resonant capacitor to the secondary winding of said isolating converter transformer;

a direct-current output voltage generating means for rectifying an alternating voltage inputted from the secondary winding of said isolating converter transformer and thereby providing a secondary-side direct-current output voltage;

switching driving means for effecting control for constant voltage by driving said switching means for switching operation such that switching frequency of said switching means is variably controlled according to level of said secondary-side direct-current output voltage, and at the same time an on period of said switching means within one switching cycle is variably controlled while an off period thereof is fixed; and

active clamp means for clamping a primary-side parallel resonance voltage generated across said primary-side parallel resonant capacitor, the active clamp means including an auxiliary switching device that is driven for switching operation such that the auxiliary switching device and said switching means perform on/off operation substantially alternately.

2. The switching power supply circuit as claimed in

claim 1

,

wherein the secondary-side resonant capacitor is connected in parallel or in series with the secondary winding of said isolating converter transformer.

3. The switching power supply circuit as claimed in

claim 1

, wherein said switching driving means comprises:

an orthogonal transformer having a detecting winding for detecting a resonance current;

a driving winding for driving said switching means; and

a control winding wound in a direction orthogonal to said detecting winding and said driving winding;

wherein inductance of said driving winding is changed by changing a current flowing in said control winding according to a level of said secondary-side direct current output voltage, whereby the switching frequency of said switching means is variably controlled.