| US 7,542,308 B2 | ||
| DC-DC converter | ||
| Tomoyasu Yamada, Niiza (Japan) | ||
| Assigned to Sanken Electric Co., Ltd., Saitama (Japan) | ||
| Filed on Mar. 27, 2006, as Appl. No. 11/391,606. | ||
| Claims priority of application No. 2005-097897 (JP), filed on Mar. 30, 2005. | ||
| Prior Publication US 2006/0221650 A1, Oct. 05, 2006 | ||
| Int. Cl. H02M 3/335 (2006.01); H02M 5/42 (2006.01); H02M 7/537 (2006.01); H02M 5/257 (2006.01); G05F 5/00 (2006.01) | ||
| U.S. Cl. 363—21.01 [363/21.12; 363/21.14; 363/21.15; 363/21.17; 363/21.18; 363/16; 363/20; 363/97; 363/131; 363/163; 363/165; 363/21.13; 323/301; 323/303] | 4 Claims |
| 1. A DC-DC converter comprising a primary winding of a transformer and at least one switching element connected in series
to a DC power source; a secondary winding of the transformer; a rectifying smoother connected to the primary or secondary
winding of the transformer for supplying DC power to an electric load; an output voltage detector for sensing an output voltage
to the load to produce a detection signal; and a control circuit for receiving the detection signal from the output voltage
detector to produce on-off signals to a control terminal of the switching element;
the control circuit comprising an oscillator for generating pulse signals of a given frequency; a drive signal generator for
producing on-off signals to the control terminal of the switching element in synchronization with pulse signals from the oscillator;
an intermittent controller for producing a control signal to the drive signal generator in response to the level of detection
signal from the output voltage detector to switch the switching element to the intermittent operation during the light load
period; and a power control circuit for ceasing power supply to the oscillator during the light load period in response to
the control signal from the intermittent controller;
wherein said drive signal generator comprises a gate circuit for producing a drive signal to a control terminal of said switching
element; and a first comparator for producing a control signal to cease generation of drive signal from said gate circuit
when decreasing comparative voltage with rising output voltage is lower than voltage the level corresponding to the amount
of winding current through said switching element;
said intermittent controller comprises a second comparator for producing a control signal to said gate circuit of said drive
signal generator to stop drive signal from said gate circuit when said comparative voltage is lower than a reference voltage;
said second comparator switches the reference voltage from a first reference voltage to a second reference voltage higher
than the first reference voltage to extend the rising term of the comparative voltage lower than the reference voltage; and
said power control circuit prevents generation of pulse signal from the oscillator for the cessation period of the switching
element during the whole intermittent operation of switching element inclusive of the extended rising term of the comparative
voltage.
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