Switching power supply circuit

• US 20030155901A1
• Filed: 01/30/2003
• Published: 08/21/2003
• Est. Priority Date: 02/15/2002
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yasumura, Masayuki
• Granted Patent: US 6,747,883 B2
• Time in Patent Office: Days
• US Class Current: 323/323
• 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

In a complex resonance type switching power supply circuit including: a series resonant circuit formed by a leakage inductance component having a primary-side winding of an isolation converter transformer driven by switching devices formed by half-bridge coupling and a primary-side series resonant capacitor connected in series with the primary-side winding; and a partial voltage resonance circuit connected in parallel with one of the switching devices mentioned above, for effecting partial voltage resonance in timing of turning off of the switching devices, an auxiliary switching device of a series circuit connected in parallel with the primary-side series resonant capacitor and formed by the auxiliary switching device and a capacitor is operated only during a period when the switching device connected in parallel with a primary-side partial resonance capacitor is on, and during this period, the capacitor of the series circuit is connected in parallel with the primary-side series resonant capacitor. Thus, even when the gap of the isolation converter transformer is zero, the switching devices are operated stably by ZVS and ZCS. Also, AC-to-DC power conversion efficiency is improved and leakage magnetic flux is reduced.

Claims

1. A switching power supply circuit comprising:

switching means formed by half-bridge coupling of two switching devices, for performing switching operation on a direct-current input voltage;

a converter transformer having a primary winding and a secondary winding formed around a magnetic core having no gap formed therein, for transmitting an output of said switching means obtained in the primary winding to the secondary winding;

a primary-side series resonant circuit formed at least by a leakage inductance component including the primary winding of said converter transformer and capacitance of a primary-side series resonant capacitor connected in series with said primary winding, for converting the switching operation of said switching devices into current resonance type operation;

a primary-side partial resonance capacitor connected in parallel with one of said two switching devices, for effecting partial resonance in timing corresponding to a turn-off time of said one of said two switching devices;

switching driving means for applying a switching driving signal to said two switching devices for switching operation;

a series circuit connected in parallel with said primary-side series resonant capacitor, and formed at least by a series connection of an auxiliary switching device for performing switching operation so as to have an on period in correspondence with timing of turning off of the switching device with which said primary-side partial resonance capacitor is connected and a capacitor for which more than a predetermined capacitance value is selected; and

direct-current output voltage generating means for receiving an alternating voltage obtained at the secondary winding of said isolation converter transformer as an input and generating a predetermined secondary-side direct-current output voltage.

2. A switching power supply circuit as claimed in claim 1, further including constant-voltage control means for effecting constant-voltage control on said secondary-side direct-current output voltage.

3. A switching power supply circuit as claimed in claim 2,

wherein said constant-voltage control means effects constant-voltage control on said secondary-side direct-current output voltage by variably controlling switching frequency of said switching driving means according to level of said secondary-side direct-current output voltage.

4. A switching power supply circuit as claimed in claim 2,

wherein said constant-voltage control means effects constant-voltage control on said secondary-side direct-current output voltage by varying a conduction angle of said auxiliary switching device and variably controlling switching frequency of said switching driving means according to level of said secondary-side direct-current output voltage.

5. A switching power supply circuit as claimed in claim 1, further including a secondary-side partial resonance circuit formed by the secondary winding of said isolation converter transformer and a secondary-side partial resonance capacitor connected in parallel with the secondary winding, for effecting partial resonance in correspondence with timing of turning off of a rectifier diode device forming said direct-current output voltage generating means,

wherein the capacitance value of said capacitor and said primary-side series resonant capacitor is selected such that primary-side resonance frequency is lower than a predetermined frequency in relation to switching frequency.

6. A switching power supply circuit as claimed in claim 1,

wherein said switching driving means is formed by a self-oscillation driving circuit for self-excited switching driving of said two switching devices.

7. A switching power supply circuit as claimed in claim 1,

wherein said switching driving means is formed by an external oscillation driving circuit for externally excited switching driving of said two switching devices.

8. A switching power supply circuit as claimed in claim 1,

wherein said converter transformer is formed by winding said primary winding and said secondary winding around a central magnetic leg of an E-E-shaped core formed by combining a pair of E-shaped cores with each other.

9. A switching power supply circuit as claimed in claim 1,

wherein said converter transformer is formed by winding said primary winding and said secondary winding around one magnetic leg of a U-U-shaped core formed by combining a pair of U-shaped cores with each other.