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EP0583038A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Power supply circuit and control circuit for use in a power supply circuit

Assignee: Koninklijke Philips NV
•
Filing: 1993-08-09
•
Granted: —
•
Expires: 2013-08-09
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Abstract

Abstract A power supply circuit for generating a stabilized power supply generally comprises a series arrangement of a primary winding (7) of a transformer (T) and a switch (9). The switch is controlled by means of a control circuit (21), an input of which receives a signal (Vf b ) related to the output voltage of the power supply circuit. The control circuit (21) determines the duty cycle of the switch (9). Dependent on the power consumption of the load (R b ) connected to the output of the power supply circuit, the duty cycle is either increased or decreased. The duty cycle has a given minimum value which is caused by the inertia of the switch (9) upon switching on and switching off. The minimum duty cycle may be reached, inter alia, when the power supply circuit works in an apparatus using a standby mode. With reference to the power to be supplied to the load and/or with reference to the duty cycle, the power supply circuit according to the invention determines the moment when the frequency of the control signal to be generated by the control circuit is switched to another fixed frequency.

Inventors

  • 👤 Antonius Adrianus Maria Marinus

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-10-31 03:19
CPC Classifications
H; H02; H02M; H02M3/00; H02M3/22; H02M3/24; H02M3/28; H02M3/325; H02M3/335; H02M3/33507; H02M1/00; H02M1/0003; H02M1/0032; Y; Y02; Y02B; Y02B70/00; Y02B70/10

Claims Analysis

Total Claims: 6
Claim 1
Independent Claim 210 words
A power supply circuit (V) having input terminals (1, 2) for receiving an input voltage (Vin) and output terminals (17, 18) for supplying an output voltage (Vout), which circuit comprises, coupled parallel to the input terminals of the power supply circuit, a series arrangement of a primary winding (7) of a transformer (T) and a switch (9, 9'), a secondary winding (11) of the transformer coupled to the output terminals of the power supply circuit and a control circuit (21) having an input which is coupled to the output terminals of the power supply circuit and an output for supplying a control signal to the switch, said control circuit comprising an oscillator circuit (29) for generating a pulse width-modulated control signal having a predetermined frequency, characterized in that the control circuit is adapted to receive a feedback signal (Vfb) at the input of the power to be supplied at the output terminals of the power supply circuit and is adapted to receive at a further input a signal (Pset) to be externally set, said control circuit also comprising switching means (35) for switching an oscillator of the oscillator circuit from the predetermined frequency to another fixed frequency in dependence upon the signal to be externally set and the feedback signal.
Claim 2
Dependent Claim 39 words
A power supply circuit as claimed in Claim 1, characterized in that the control circuit comprises means for detecting the moment of switching to the other fixed frequency with reference to a current flowing through the switch during operation.
Claim 3
Dependent Claim 42 words
A power supply circuit as claimed in Claim 1, characterized in that the means comprise a differential amplifier for amplifying the difference between the feedback signal and a reference signal, an output of the differential amplifier being coupled to the switching means.
Claim 4
Dependent Claim 35 words
A power supply circuit as claimed in Claim 1, characterized in that the control circuit comprises means for detecting the moment of switching to the other fixed frequency with reference to the given duty cycle.
Claim 5
Dependent Claim 42 words
A power supply circuit as claimed in Claim 4, characterized in that the means comprise an extra winding on the transformer, and a duty cycle detection circuit for detecting the duty cycle and for supplying a switching signal to the oscillator circuit.
Claim 6
Dependent Claim 19 words
A control circuit for use in a power supply circuit as claimed in any one of the preceding Claims.

References Cited (Backward Citations)

WO1987004885A1 Cited
EP0244623A2 Cited
US4772995A Cited

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