SWITCHING POWER SUPPLY DEVICE
1 Assignment
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Accused Products
Abstract
In a switching power supply device, a voltage of a counter electromotive force induced in a drive winding as a high side switching element is turned off is output to a ZT terminal of a switching control IC, and thus an OUT terminal of the switching control IC is brought to a high level, and thus a low side switching element is turned on. A constant current circuit charges a capacitor with a constant current through a voltage at the OUT terminal. A comparator in the switching control IC inverts the voltage at the OUT terminal to a low level upon a voltage at an IS terminal exceeding a voltage at an FB terminal. Thus, an on time of the low side switching element is controlled in accordance with a voltage output to the FB terminal, and an output voltage Vo is turned into a constant voltage.
7 Citations
20 Claims
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1. (canceled)
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2. A switching power supply device, comprising:
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a power supply voltage output unit configured to accept output of an output power supply voltage; a direct current voltage output unit configured to receive output of a direct current voltage; a transformer including a primary winding and a secondary winding; a low side switching element connected in series to the primary winding and configured to apply a voltage at the power supply voltage output unit to the primary winding upon being turned on; a switching control circuit configured to control the low side switching element; a rectifying smoothing circuit configured to rectify and smooth a voltage output from the secondary winding and output an output voltage to the direct current voltage output unit; and a feedback voltage signal generating circuit configured to generate a feedback voltage signal based on the output voltage;
whereinthe switching control circuit includes; a drive voltage signal output unit configured to output, upon detecting an inversion of a voltage polarity in the transformer, a drive voltage signal that causes the low side switching element to turn on; a reference voltage generating circuit configured to generate a reference voltage of which a voltage changes along with a time that has elapsed since the drive voltage signal has been output; and a turn off control unit configured to switch the drive voltage signal to a voltage at which the low side switching element is turned off, in response to the reference voltage reaching a voltage of the feedback voltage signal. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification