Control Circuit For A Switching Power Supply, Method For Controlling A Switching Power Supply And Computer Program
First Claim
1. A control circuit for a switching power supply comprising a controllable switch for switching a current flowing through a first winding of a transformer and a voltage providing circuit for providing an output voltage based on a voltage generated in the second winding of the transformer, the control circuit comprising:
- a comparing circuit for getting a comparison signal based on a comparison between an input signal derived from a current through the switch or through the first winding and a threshold signal derived from a voltage present in the voltage providing circuit;
a threshold signal modulation circuit adapted to modulate the threshold signal in such a way that the comparison signal is activated as soon as the input signal derived from the current flowing through the switch or through the first winding crosses a first threshold value, if the current flowing through the switch or through the first winding exhibits a first current slope rate, and that the comparison signal is activated as soon as the input signal of the comparing circuit describing the current flowing through the switch or through the first winding crosses a second threshold value, if the current flowing through the switch or through the first winding exhibits a second current slope rate smaller than the first current slope rate, wherein, for a given voltage present in the voltage providing circuit, the first threshold value is smaller than the second threshold value; and
a switch driver for closing the switch periodically, and for opening the switch in response to an activation of the comparison signal provided by the comparing circuit.
1 Assignment
0 Petitions
Accused Products
Abstract
A control circuit for a power supply having a controllable switch for switching a current through a first transformer winding and a voltage providing circuit for providing an output voltage based on a voltage generated in a second transformer winding has a comparing unit for generating a comparison signal. The control circuit has a threshold signal modulation circuit adapted to modulate the threshold signal that the comparison signal is activated as soon as the input signal crosses a first threshold value, if the current flowing through the switch exhibits a first current slope rate, and that the comparison signal is activated as soon as the input signal crosses a second threshold value, if the current flowing through the switch exhibits a second current slope rate smaller than the first rate. For a given voltage, the first threshold is smaller than the second threshold.
-
Citations
18 Claims
-
1. A control circuit for a switching power supply comprising a controllable switch for switching a current flowing through a first winding of a transformer and a voltage providing circuit for providing an output voltage based on a voltage generated in the second winding of the transformer, the control circuit comprising:
-
a comparing circuit for getting a comparison signal based on a comparison between an input signal derived from a current through the switch or through the first winding and a threshold signal derived from a voltage present in the voltage providing circuit;
a threshold signal modulation circuit adapted to modulate the threshold signal in such a way that the comparison signal is activated as soon as the input signal derived from the current flowing through the switch or through the first winding crosses a first threshold value, if the current flowing through the switch or through the first winding exhibits a first current slope rate, and that the comparison signal is activated as soon as the input signal of the comparing circuit describing the current flowing through the switch or through the first winding crosses a second threshold value, if the current flowing through the switch or through the first winding exhibits a second current slope rate smaller than the first current slope rate, wherein, for a given voltage present in the voltage providing circuit, the first threshold value is smaller than the second threshold value; and
a switch driver for closing the switch periodically, and for opening the switch in response to an activation of the comparison signal provided by the comparing circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
-
-
17. A method for controlling a switching power supply comprising a controllable switch for switching a current flowing through a first winding of a transformer, a voltage providing circuit for providing an output voltage based on a voltage generated in a second winding of the transformer and a switch driver for periodically closing the switch and for opening the switch in response to an occurrence of a condition to open the switch, the method comprising:
-
modulating a threshold signal dependent on a voltage present in the voltage providing circuit in such a way that a comparison between the threshold signal and a signal derived from a current flowing through the controllable switch or through the first winding yields a condition to open the switch as soon as the signal derived from the current through the controllable switch reaches a first threshold value, if a current through the switch or through the first winding exhibits a first slope rate, and that the comparison between the threshold signal and the signal derived from the current through the controllable switch or through the first winding yields a condition to open the switch as soon as the signal derived from the current through the controllable switch or through the first winding reaches a second threshold value, if the current through the switch or the first winding exhibits a second slope rate smaller than the first slope rate, wherein, for a given voltage present in the voltage providing circuit, the first threshold value is smaller than the second threshold value.
-
-
18. A computer program product comprising a program code stored on a computer readable medium, wherein the program code when executed on a computer performs a method for controlling a switching power supply comprising a controllable switch for switching a current flowing through a first winding of a transformer, a voltage providing circuit for providing an output voltage based on a voltage generated in a second winding of the transformer and a switch driver for periodically closing the switch and for opening the switch in response to an occurrence of a condition to open the switch, the method comprising:
modulating a threshold signal dependent on a voltage present in the voltage providing circuit in such a way that a comparison between the threshold signal and a signal derived from a current flowing through the controllable switch or through the first winding yields a condition to open the switch as soon as the signal derived from the current through the controllable switch reaches a first threshold value, if a current through the switch or through the first winding exhibits a first slope rate, and that the comparison between the threshold signal and the signal derived from the current through the controllable switch or through the first winding yields a condition to open the switch as soon as the signal derived from the current through the controllable switch or through the first winding reaches a second threshold value, if the current through the switch or the first winding exhibits a second slope rate smaller than the first slope rate, wherein, for a given voltage present in the voltage providing circuit, the first threshold value is smaller than the second threshold value.
Specification