Method for controlling a converter
View Patent ↗A method for controlling a converter including a resonant circuit, where the converter is controlled such that control switches are switched into a first state at the occurrence of an event that is related to a dependent variable of the converter and are switched into a second state at the occurrence of an event that is not related to a dependent variable of the converter, and the method may be employed in a converter or an inductive power transfer transmitter.
1. A method of controlling an inductive power transfer transmitter, the transmitter including a resonant circuit having an inductor in which the direction of current through the inductor is dependent on the state of associated first and second control switches, the method comprising, for each of the first and second control switch:
switching into a first state in response to a zero-crossing event; and
switching into a second state in response to an end of a predetermined interval;
wherein the predetermined time interval begins after the same or another of the first and second control switches is switched off.
2. The method as claimed in claim 1 , wherein the first state is an on state and the second state is an off state.
3. The method as claimed in claim 1 , wherein the first state is an off state and the second state is an on state.
4. The method as claimed in claim 1 , wherein the predetermined time interval is the same as half a desired period of operation of the converter.
5. The method as claimed in claim 1 , wherein the predetermined time interval is the same as a desired period of operation of the converter.
6. The method as claimed in claim 1 , wherein the zero-crossing event is when the voltage across a control switch goes to zero.
7. The method as claimed in claim 1 , wherein the zero-crossing event is when the current through a control switch goes to zero.
8. The method as claimed in claim 4 or 5 , wherein the desired period of operation of the converter is chosen to be similar to the unloaded natural resonant period of the converter.
9. The method of claim 1 , wherein the predetermined time interval is related to a substantially constant converter frequency.
10. An inductive power transfer transmitter including a resonant circuit with an inductor in which the direction of current through the inductor is dependent on the state of associated first and second control switches, and control circuitry adapted to control the first and second control switches so that:
the control switches are switched into a first state in response to a zero-crossing event; and
the control switches are switched into a second state in response to an end of a predetermined time interval;
wherein the predetermined time interval begins after the same or another of the first and second control switches is switched off.
11. The transmitter of claim 10 , wherein the first state is an on state and the second state is an off state.
12. The transmitter of claim 10 , wherein the first state is an off state and the second state is an on state.
13. The transmitter of claim 10 , wherein the control circuitry is adapted to detect the zero-crossing event and the end of the predetermined time interval.
14. The transmitter of claim 10 , wherein the predetermined time interval is the same as half a desired period of operation of the converter.
15. The transmitter of claim 10 , wherein the predetermined time interval is the same as a desired period of operation of the converter.
16. The transmitter of claim 10 , wherein the zero-crossing event is when the voltage across a control switch goes to zero.
17. The transmitter of claim 10 , wherein the zero-crossing event is when the current through a control switch goes to zero.
18. The transmitter of claim 10 , wherein the predetermined time interval is related to a substantially constant converter frequency.