US 4,937,728 A · Switch-mode power supply with burst mode standby operation

Abstract

In a switch mode power supply, a first switching transistor is coupled to a primary winding of a transformer for generating pulses of a switching current. A secondary winding of the transformer is coupled via a switching diode to a capacitor of a control circuit for developing a control signal in the capacitor. The control signal is applied to a mains coupled chopper second transistor for generating and regulating supply voltages in accordance with pulse width modulation of the control signal. During standby operation, the first and second transistors operate in a burst mode that is repetitive at a frequency of the AC mains supply voltage such as 50 Hz. In the burst mode operation, during intervals in which pulses of the switching current occur, the pulse width and peak amplitude of the switching current pulses progressively increase in accordance with the waveform of the mains supply voltage to provide a soft start operation in the standby mode of operation within each burst group.

Claims24

Dependent claims

A switch mode power supply of a television for generating an output supply voltage during both a standby-mode of operation and during a run-mode of operation, comprising:

a source of AC mains input supply voltage;
means for generating a periodic first control signal;
switching means energized by said input supply voltage and responsive to said first control signal for producing a switching current during both said standby-mode of operation and said run-mode of operation;
means responsive to said switching current for generating therefrom said output supply voltage;
a source of a standby-mode/run-mode control signal;
and
fourth means coupled to said switching means and responsive to said standby-mode/run-mode control signal and to a signal at a frequency that is determined by a frequency of said AC mains input supply voltage for controlling said switching means in a burst mode manner during said standby mode of operation, such that during a burst interval a plurality of switching cycles are performed and during an alternating dead time interval no switching cycles are performed, the two intervals alternating at a frequency that is determined by said frequency of said AC mains input supply voltage.

4 more elements

A switch mode power supply, comprising:

a source of AC mains input supply voltage at a first frequency;
a transformer having a first winding coupled to said input supply voltage;
first switching means coupled to said first winding for generating a switching current therein, said first switching means and said transformer forming a regenerative positive feedback signal path that forms an oscillator that oscillates continuously during a run-mode of operation;
means coupled to said input supply voltage and responsive to an output signal of said oscillator for generating from said input supply voltage said output supply voltage by a switching operation controlled in accordance with said oscillator output signal;
means responsive to said output supply voltage and coupled to said oscillator for modulating said oscillator output signal during said run mode of operation in a negative feedback manner thereby regulating said output supply voltage;
means responsive to a standby-mode/run-mode control signal and coupled to said oscillator for disabling the continuous oscillations in said oscillator, in a standby mode of operation;
and
means responsive to a signal at a frequency that is determined by said first frequency for initiating a burst mode switching operation in said first switching means that is repetitive at a frequency determined by said first frequency when the continuous oscillations are disabled.

5 more elements

A switch mode power supply, comprising:

a source of AC mains input supply voltage;
a source of a signal at a first frequency;
a transformer having a first winding coupled to said input supply voltage;
first switching means coupled to said first winding for generating a switching signal in said transformer that is coupled back in a positive feedback manner to said first switching means to form an oscillator that oscillates continuously, during a run-mode of operation;
means coupled to said input supply voltage and responsive to an output signal of said oscillator for generating from said input supply voltage said output supply voltage by a switching operation controlled in accordance with said oscillator output signal;
means responsive to said output supply voltage and coupled to said oscillator for modulating said oscillator output signal during a run mode of operation in a negative feedback manner thereby regulating said output supply voltage;
means responsive to a standby-mode/run-mode control signal and coupled to said oscillator for disabling in a standby mode of operation the continuous oscillations in said oscillator;
means responsive to said signal at said first frequency for initiating a burst mode switching operation in said first switching means that is repetitive at a frequency determined by said first frequency when the continuous oscillations are disabled;
a capacitor;
and
second switching means responsive to said standby-mode/run-mode control signal for coupling said capacitor to said positive feedback signal path to maintain a switching frequency of said first switching means above an audible range during said burst mode of operation and for decoupling said capacitor from said positive feedback signal path to prevent said capacitor from affecting the oscillation frequency of said oscillator during said run-mode of operation.

8 more elements

Dependencies are inferred from the claim text.

Switch-mode power supply with burst mode standby operation

Life of this patent

Switch-mode power supply with burst mode standby operation

Life of this patent

Abstract

Claims24