Power supply circuit
First Claim
1. A power supply circuit comprising:
- a first rectifying circuit for producing a first DC voltage when AC power is supplied thereto;
a transformer having primary, secondary, tertiary and fourth windings, said primary winding being connected to said first rectifying circuit;
a second rectifying circuit connected to said secondary winding so as to produce a DC output voltage in response to an output voltage generated on said secondary winding;
a detecting circuit for detecting said DC output voltage;
modulating means for generating a modulated signal in response to an output signal of said detecting circuit;
an active switching element connected in series with said primary winding of said transformer and controlled by said modulated signal so as to chop said first DC voltage applied to said transformer;
an oscillation circuit connected to said fourth winding of said transformer and to said active switching element for generating an oscillation signal in said transformer, said oscillation circuit further including means for feeding back a signal produced in said fourth winding to said active switching element to cause self oscillation of the latter; and
a third rectifying circuit connected to said tertiary winding of said transformer for receiving said oscillation signal and converting the same to a DC voltage which is supplied to said modulating means as an operating voltage thereof.
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Accused Products
Abstract
In a power supply circuit of the type including a first rectifier to be connected to an AC power source through a power switch, a transformer with primary and secondary windings, a second rectifier connected to the secondary winding of the transformer to provide a desired DC output voltage, a pulse width modulated signal producing circuit, and a transistor connected to the primary winding of the transformer to be supplied with the pulse width modulated signal so as to chop the direct current flowing through the transformer; there is further provided an oscillation circuit connected to the primary winding of the transformer for generating an oscillation signal for a predetermined period following closing of the power switch, and a third rectifier for producing a DC voltage in response to such oscillation signal, with the DC voltage from the third rectifier being supplied to the pulse width modulated signal producing circuit as an operating voltage therefor.
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Citations
7 Claims
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1. A power supply circuit comprising:
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a first rectifying circuit for producing a first DC voltage when AC power is supplied thereto; a transformer having primary, secondary, tertiary and fourth windings, said primary winding being connected to said first rectifying circuit; a second rectifying circuit connected to said secondary winding so as to produce a DC output voltage in response to an output voltage generated on said secondary winding; a detecting circuit for detecting said DC output voltage; modulating means for generating a modulated signal in response to an output signal of said detecting circuit; an active switching element connected in series with said primary winding of said transformer and controlled by said modulated signal so as to chop said first DC voltage applied to said transformer; an oscillation circuit connected to said fourth winding of said transformer and to said active switching element for generating an oscillation signal in said transformer, said oscillation circuit further including means for feeding back a signal produced in said fourth winding to said active switching element to cause self oscillation of the latter; and a third rectifying circuit connected to said tertiary winding of said transformer for receiving said oscillation signal and converting the same to a DC voltage which is supplied to said modulating means as an operating voltage thereof. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification