Method for operating a switch in a free-running switch mode power supply, and a drive circuit for a switch in a free-running switch mode power supply
AssigneeInfineon Technologies AG
InventorMartin Feldtkeller
Life of this patent
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Abstract
A method for operating a switch, which is connected in series with a primary coil of a transformer in a free-running switch mode power supply, includes the provision of a modulation signal and the provision of a drive signal for the switch. The drive signal includes a recurrent pulse sequence which has at least one first switching-on pulse with a first pulse duration and at least one second switching-on pulse with a second pulse duration, and with the pulse duration of at least one of the switching-on pulses being modulated by the modulation signal within a range of valves which is predetermined by the control signal.
Claims16
A method for operating a switch connected in series with a primary coil of a transformer in a free-running switch mode power supply, a secondary coil of the transformer being coupled to output terminals carrying an output voltage, the switch being switched on when the primary coil reaches a predetermined magnetization state, which comprises the steps of:
- applying an input voltage to a series circuit formed by the primary coil and the switch;
- providing a control signal for controlling power consumption;
- providing a modulation signal;
- and
- providing a drive signal for driving the switch, the drive signal containing a recurrent pulse sequence having at least one first switching-on pulse with a first pulse duration and at least one second switching-on pulse with a second pulse duration, a pulse duration of at least one of the first and second switching-on pulses being modulated by the modulation signal within a range predetermined by the control signal.
A drive circuit for a switch connected in series with a primary coil of a transformer of a free-running switch mode power supply, the drive circuit comprising:
- a first input terminal for receiving a control signal governing power consumption;
- a second input terminal for receiving a magnetization signal being dependent on a magnetization state of the primary coil;
- an output terminal providing a drive signal;
- a signal generating circuit connected to said output terminal and said second input terminal, said signal generating circuit receiving the magnetization signal and a reference signal being dependent on the control signal, said signal generating circuit generating the drive signal containing a sequence of switching-on pulses, a start of a switching-on pulse in each case being predetermined by the magnetization signal, and a duration of the switching-on pulse being predetermined by the reference signal;
- a reference signal generating circuit connected to said first input terminal and said signal generating circuit, said reference signal generating circuit receiving the control signal and generating the reference signal, said reference signal generating circuit containing:
- a signal generator providing a modulation signal;
- a weighting circuit connected to said signal generator and said first input terminal, said weighting circuit receiving the control signal and the modulation signal and providing a weighted control signal weighted on a basis of the modulation signal;
- and
- a changeover switch having switching positions, and on a basis of said switching positions, the control signal or the weighted control signal being provided as the reference signal.
Dependencies are inferred from the claim text.