SWITCHING POWER SUPPLY APPARATUS AND SEMICONDUCTOR DEVICE USED IN THE SWITCHING POWER SUPPLY APPARATUS
First Claim
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1. A switching power supply apparatus, comprising:
- a switching transformer having a primary winding, a secondary winding and an auxiliary winding;
a switching element connected to the primary winding;
an output voltage generating circuit, connected to the secondary winding, for generating an output DC voltage by rectifying and smoothing an AC voltage induced in the secondary winding by a switching operation of the switching element;
a regulating circuit, connected to the auxiliary winding, for generating an AC voltage proportional to a voltage component in which a ringing component of an AC voltage induced in the auxiliary winding by the switching operation of the switching element has been removed; and
a control circuit for controlling the switching operation of the switching element,wherein the control circuit comprises an overvoltage detection circuit for controlling the switching operation of the switching element so as to reduce the output DC voltage when a peak value of the AC voltage generated by the regulating circuit becomes equal to or greater than a prescribed value.
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Abstract
A switching power supply apparatus having a highly accurate overvoltage protection function which is free of erroneous operation is provided. A regulating circuit connected to an auxiliary winding generates an AC voltage proportional to a voltage component in which the ringing component has been removed from the AC voltage induced in the auxiliary winding by the switching operation of a switching element. If the peak value of the AC voltage generated by the regulating circuit is equal to or greater than a prescribed value, an overvoltage detection circuit controls the switching operation of the switching element so as to reduce the output DC voltage.
37 Citations
7 Claims
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1. A switching power supply apparatus, comprising:
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a switching transformer having a primary winding, a secondary winding and an auxiliary winding; a switching element connected to the primary winding; an output voltage generating circuit, connected to the secondary winding, for generating an output DC voltage by rectifying and smoothing an AC voltage induced in the secondary winding by a switching operation of the switching element; a regulating circuit, connected to the auxiliary winding, for generating an AC voltage proportional to a voltage component in which a ringing component of an AC voltage induced in the auxiliary winding by the switching operation of the switching element has been removed; and a control circuit for controlling the switching operation of the switching element, wherein the control circuit comprises an overvoltage detection circuit for controlling the switching operation of the switching element so as to reduce the output DC voltage when a peak value of the AC voltage generated by the regulating circuit becomes equal to or greater than a prescribed value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification