Switching power circuit with secondary side parallel and series resonance

• US 6,262,897 B1
• Filed: 10/27/2000
• Issued: 07/17/2001
• Est. Priority Date: 10/29/1999
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yasumura, Masayuki
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US09/698,398
• Time in Patent Office: 263 Days
• Field of Search: 363/21.02, 363/21.03
• 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

As a secondary side resonant circuit, a secondary side parallel resonant circuit and a secondary side series resonant circuit are combined to a secondary winding of an insulating converter transformer to form a secondary side resonant circuit. By this, the constant voltage control of a secondary side DC output voltage is made the combined control of controlling a switching frequency and a conduction angle of a switching current flowing through a switching element, so that enlargement of a period in which the switching element is turned off is suppressed.

Claims

1. A switching power supply circuit comprising:

switching means including a switching element operable at a switching frequency for intermittently outputting an inputted DC input voltage;

an insulating converter transformer for transmitting the output of the switching means to a secondary side;

a primary side voltage resonant circuit coupled to the switching means to operate the switching means as a voltage resonant type;

a secondary side resonant circuit constituted by a combination of a secondary side parallel resonant circuit formed of a secondary side parallel resonant capacitor connected in parallel with a secondary winding of the insulating converter transformer, and a secondary side series resonant circuit formed of a secondary side series resonant capacitor connected in series with the secondary winding of the insulating converter transformer;

DC output voltage generation means for rectifying an AC voltage obtained from the secondary winding of the insulating converter transformer to produce a secondary side DC output voltage; and

constant voltage control means for changing the switching frequency of the switching element in accordance with the secondary side DC output voltage.

2. A switching power supply circuit according to claim 1, wherein the DC output voltage generation means includes a bridge rectifier circuit formed of four rectifier diode elements and a smoothing capacitor, and wherein the secondary side series resonant capacitor is connected in a rectified current path, the DC output voltage generation means operating as a full-wave rectifier circuit for generating the secondary side DC output voltage that is almost equal to the AC voltage.

3. A switching power supply circuit according to claim 1, wherein the DC output voltage generation means includes two diode elements, a smoothing capacitor, and an inductor connected in a current path of the current flowing in the smoothing capacitor, and wherein the secondary side series resonant capacitor is charged by the rectified output of one of the diode elements, so that the DC output voltage generation means operates as a half-wave rectifier circuit for generating the secondary side DC output voltage that is almost equal to the AC voltage.

4. A switching power supply circuit according to claim 1, wherein the DC output voltage generation means includes two pairs of rectifier diodes and a pair of smoothing capacitors, and performes voltage doubling half-wave rectification to generate the secondary side DC output voltage of a level twice the AC voltage.

5. A switching power supply circuit according to claim 1, wherein the DC output voltage generation means includes a pair of rectifier diodes and a pair of smoothing capacitors, and performs voltage doubling full-wave rectification to generate the secondary side DC output voltage of a level twice the AC voltage.

6. A switching power supply circuit according to claim 1, wherein the DC output voltage generation means includes two pairs of rectifier diodes and a pair of smoothing capacitors, and wherein the secondary side resonant circuit includes a pair of secondary side series resonant capacitors inserted to a rectified current path, whereby the DC output voltage generation means performs a quadruple voltage full-wave rectification operation to generate the secondary side DC output voltage of a level four times the AC voltage.