Switched-mode power supply with low switching losses
AssigneeInfineon Technologies AG
InventorPeter Preller
Life of this patent
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Abstract
A method for driving a switch in a switched-mode power supply, in which the switch is connected in series with a primary coil of a transformer and in which a control signal dependent on an output voltage is available. In this case, reference instants at which a voltage present across the switch corresponds to a first reference voltage value or at which a voltage present across the primary coil corresponds to a second reference voltage value are detected and counted, the switch being closed again only after the number of detected reference instants has reached a comparison numerical value. The invention furthermore relates to a switched-mode power supply for realizing the method according to the invention.
Claims12
A method for driving a switched-mode power supply having a power switch connected in series with a primary coil of a transformer, the switched-mode power supply generating a control signal dependent on an output voltage of the switched-mode power supply, which comprises the step of:
- detecting reference instants, the reference instants being one of first reference instants at which a power switch voltage present across the power switch corresponds to a first reference voltage value and second reference instants at which a coil voltage present across the primary coil corresponds to a second reference voltage value;
- closing the power switch after a number of the reference instants detected has reached a comparison numerical value;
- and
- performing one of increasing and reducing the comparison numerical value in dependence on whether the control signal exceeds an upper limit value or falls below a lower limit value.
A switched-mode power supply, comprising:
- a transformer having a primary coil;
- a switch connected in series with said primary coil of said transformer and turns on and off according to drive pulses received by said switch;
- a drive circuit for generating the drive pulses in a manner dependent on an enable signal received by said drive circuit;
- a controller configuration outputting a control signal dependent on an output voltage and connected to said drive circuit;
- and
- a circuit configuration receiving the control signal and generating the enable signal, said circuit configuration, including:
- a detection circuit for detecting reference instants at which a voltage present across said switch corresponds to a predetermined first reference voltage value;
- a first counter connected to said detection circuit and having an output outputting a first counter signal;
- a second counter having a first input receiving a first signal dependent on a comparison of the control signal with a first reference signal, and a second input, receiving a second signal dependent on a comparison of the control signal with a second reference signal, said second counter having an output outputting a comparison counter signal;
- and
- a comparator configuration receiving the first counter signal and the comparison counter signal and outputs the enable signal, said comparator configuration connected to said drive circuit, to said first counter, and to said second counter.
Dependencies are inferred from the claim text.