Control device for a DC-DC converter
A control device controls a switching circuit of a DC-DC converter. The switching circuit includes a half-bridge with at least first and second switches connected between an input voltage and a reference voltage. The converter comprises a transformer with a primary coupled with the center point of the half-bridge and a secondary coupled with a load. The control device comprises an error detector configured to determine an error signal representing a difference between a first signal representative of the voltage across the load and a first reference signal and a frequency controller configured to increase the switching frequency of the half-bridge when the error signal is kept below a second signal.
1. A control device for controlling a switching circuit of a DC-DC converter, said control device comprising:
an error detector configured to provide an error signal based on a difference between a first signal, representative of a load voltage, and a first reference signal;
a frequency controller configured to increase a switching frequency of the switching circuit in response to detecting that the error signal is below a first threshold; and
a sense comparator configured to deactivate the switching circuit in response to detecting that the error signal decreases below a second threshold.
2. The device according to claim 1 , wherein said sense comparator is configured to keep said switching circuit deactivated for a number of switching cycles substantially equal to a period of time during which the error signal remains below the second threshold.
3. The device according to claim 1 , further comprising a comparator configured to compare said error signal with a signal representative of a current through a primary coil of a transformer of the DC-DC converter and to control opening of one of two switches of a half-bridge of the switching circuit as a function of said comparison.
4. The device according to claim 1 , further comprising an oscillator configured to provide an oscillator signal for controlling the switching frequency of a half-bridge of the switching circuit, wherein the frequency controller includes and a comparator configured to cause the oscillator to increase an oscillation frequency of the oscillator signal as a function of a comparison of the error signal with the first threshold.
5. The device according to claim 1 , wherein said frequency controller includes a capacitor configured to control the switching frequency of a half-bridge, and a transistor configured to supply said capacitor with a current having a value that increases or decreases in response to an increased or decreased difference between the first reference signal and said error signal.
6. A DC-DC switching converter comprising:
a switching circuit that includes a half-bridge with first and second switches coupled between first and second supply terminals;
a transformer with a primary coil coupled with a center point of said half-bridge and a secondary coil configured to be coupled with a load; and
a control device that includes:
an error detector configured to provide an error signal based on a difference between a first signal, representative of a load voltage, and a first reference signal;
a frequency controller configured to increase a switching frequency of the switching circuit in response to detecting that the error signal is below a first threshold; and
a sense comparator configured to deactivate the switching circuit in response to detecting that the error signal decreases below a second threshold.
7. The converter according to claim 6 , wherein said first and second switches are ZVS switches.
8. The converter according to claim 6 , wherein the transformer and half-bridge are coupled to one another in a flyback arrangement and the control device is configured to drive the half-bridge using pulse width modulation.
9. The converter according to claim 6 , wherein said sense comparator is configured to keep said switching circuit deactivated for a number of switching cycles substantially equal to a period of time during which the error signal remains below the second threshold.
10. The converter according to claim 6 , wherein the control device includes a comparator configured to compare said error signal with a signal representative of a current through a primary coil of a transformer of the DC-DC switching converter and to control opening of one of the first and second switches of the half-bridge of the switching circuit as a function of said comparison.
11. The converter according to claim 6 , wherein the control device includes an oscillator configured to provide an oscillator signal for controlling the switching frequency of the half-bridge, wherein the frequency controller includes a comparator configured to cause the oscillator to increase an oscillation frequency of the oscillator signal as a function of a comparison of the error signal with the first threshold.
12. The converter according to claim 6 , wherein said frequency controller includes a capacitor configured to control the switching frequency of the half-bridge, and a transistor configured to supply said capacitor with a current having a value that increases or decreases in response to an increased or decreased difference between the first reference signal and said error signal.
13. A method of controlling DC-DC switching converter, the method comprising:
providing an error signal based on a difference between a first signal, representative of a load voltage, and a first reference signal;
increasing a switching frequency of a switching circuit of the DC-DC switching converter in response to detecting that the error signal is below a first threshold; and
deactivating the switching circuit in response to detecting that the error signal decreases below a second threshold.
14. The method according to claim 13 , comprising keeping said switching circuit deactivated for a number of switching cycles substantially equal to a period of time during which the error signal remains below the second threshold.
15. The method according to claim 13 , comprising comparing said error signal with a signal representative of a current through a primary coil of a transformer of the DC-DC switching converter and controlling opening of one of two switches of a half-bridge of the switching circuit as a function of said comparing.
16. The method according to claim 13 , comprising:
providing an oscillator signal for controlling a switching frequency of a half-bridge of the switching circuit; and
causing the oscillator to increase an oscillation frequency of the oscillator signal as a function of a comparison of the error signal with the first threshold.
17. A control device for controlling a switching circuit of a DC-DC converter, said control device comprising:
an error detector configured to provide an error signal based on a difference between a first signal, representative of a load voltage, and a first reference signal;
a frequency controller configured to increase a switching frequency of the switching circuit in response to detecting that the error signal is below a first threshold, wherein the frequency controller includes a capacitor configured to control the switching frequency of a half-bridge, and a transistor configured to supply the capacitor with a current having a value that increases or decreases in response to an increased or decreased difference between the first reference signal and said error signal.
18. The device according to claim 17 , further comprising a comparator configured to compare said error signal with a signal representative of a current through a primary coil of a transformer of the DC-DC converter and to control opening of one of two switches of the half-bridge of the switching circuit as a function of said comparison.
19. A device according to claim 17 , further comprising an oscillator configured to provide an oscillator signal for controlling the switching frequency of the half-bridge of the switching circuit, wherein the frequency controller includes and a comparator configured to cause the oscillator to increase an oscillation frequency of the oscillator signal as a function of a comparison of the error signal with the first threshold.
20. A DC-DC switching converter comprising:
a switching circuit that includes a half-bridge with first and second switches coupled between first and second supply terminals;
a transformer with a primary coil coupled with a center point of said half-bridge and a secondary coil configured to be coupled with a load; and
a control device that includes:
an error detector configured to provide an error signal based on a difference between a first signal, representative of a load voltage, and a first reference signal; and
a frequency controller configured to increase a switching frequency of the switching circuit in response to detecting that the error signal is below a first threshold, wherein the frequency controller includes a capacitor configured to control the switching frequency of the half-bridge, and a transistor configured to supply said capacitor with a current having a value that increases or decreases in response to an increased or decreased difference between the first reference signal and said error signal.
21. The converter according to claim 20 , wherein said first and second switches are ZVS switches.
22. The converter according to claim 20 , wherein the transformer and half-bridge are coupled to one another in a flyback arrangement and the control device is configured to drive the half-bridge using pulse width modulation.
23. The converter according to claim 20 , wherein the control device includes an oscillator configured to provide an oscillator signal for controlling the switching frequency of the half-bridge, wherein the frequency controller includes a comparator configured to cause the oscillator to increase an oscillation frequency of the oscillator signal as a function of a comparison of the error signal with the first threshold.
24. A method of controlling DC-DC switching converter, the method comprising:
providing an error signal based on a difference between a first signal, representative of a load voltage, and a first reference signal;
increasing, by a frequency controller, a switching frequency of a switching circuit of the DC-DC switching converter in response to detecting that the error signal is below a first threshold;
controlling, by a capacitor of the frequency controller, the switching frequency of a half-bridge; and
supplying, by a transistor of the frequency controller, the capacitor with a current having a value that increases or decreases in response to an increased or decreased difference between the first reference signal and the error signal.
25. The method according to claim 24 , comprising comparing said error signal with a signal representative of a current through a primary coil of a transformer of the DC-DC converter and controlling opening of one of two switches of a half-bridge of the switching circuit as a function of said comparing.
26. A method according to claim 24 , comprising:
providing an oscillator signal for controlling a switching frequency of a half-bridge of the switching circuit; and
causing the oscillator to increase an oscillation frequency of the oscillator signal as a function of a comparison of the error signal with the first threshold.