Resonant ignition circuit

1. A method comprising:

receiving, from an engine control unit at an ignition circuit, a command signal;

in response to the command signal, operating a resonant circuit of the ignition circuit at a first frequency to generate a voltage in an ignition coil, the generated voltage in the ignition coil initiating a spark in a spark plug of a cylinder of an engine, the spark plug being coupled with the ignition coil;

after the spark is initiated in the spark plug, operating the resonant circuit at a second frequency to provide energy to the ignition coil and the spark plug for combustion of a fuel mixture in the cylinder of the engine; and

after the combustion of the fuel mixture, disabling the resonant circuit.

2. The method of claim 1 , wherein:

the operating the resonant circuit of the ignition circuit at the first frequency is in response to a first edge of the command signal; and

the disabling the resonant circuit is in response to a second edge of the command signal, the second edge being opposite the first edge.

3. The method of claim 1 , wherein the first frequency is greater than the second frequency.

4. The method of claim 1 , wherein the operating the resonant circuit at the first frequency includes:

providing complementary signals of the first frequency to a half-bridge circuit, the half-bridge circuit being coupled with the resonant circuit, the half-bridge circuit providing an alternating current signal of the first frequency to the resonant circuit.

5. The method of claim 1 , wherein operating the resonant circuit at the second frequency includes:

providing complementary signals of the second frequency to a half-bridge circuit, the half-bridge circuit being coupled with the resonant circuit, the half-bridge circuit providing an alternating current signal of the second frequency to the resonant circuit.

6. The method of claim 1 , wherein:

the operating the resonant circuit at the first frequency includes providing complementary signals of the first frequency to a full-bridge circuit, the full-bridge circuit being coupled with the resonant circuit, the full-bridge circuit, in response to the complementary signals of the first frequency, providing an alternating-current (AC) signal of the first frequency to the resonant circuit; and

the operating the resonant circuit at the second frequency includes providing complementary signals of the second frequency to the full-bridge circuit, the full-bridge circuit, in response to the complementary signals of the second frequency, providing an AC signal of the second frequency to the resonant circuit.

7. The method of claim 6 , wherein the AC signal does not include a direct-current (DC) voltage component.

8. The method of claim 1 , wherein:

the operating the resonant circuit at the first frequency includes providing an alternating-current (AC) signal of the first frequency to an inductive-capacitive (LC) resonant circuit that includes a primary winding of the ignition coil; and

the operating the resonant circuit at the second frequency includes providing an AC signal of the second frequency to the LC resonant circuit.

9. The method of claim 8 , wherein the AC signal of the first frequency and the AC signal of the second frequency each includes a direct current (DC) voltage component.

10. An ignition circuit comprising:

a control circuit that is configured to be coupled with an engine control unit (ECU) to receive a command signal from the ECU; and

a driving circuit coupled with the control circuit, the driving circuit being configured to be coupled with a resonant circuit that includes a primary winding of an ignition coil,

the control circuit and the driving circuit being configured, in response to the command signal, to:

drive the resonant circuit at a first frequency to generate a voltage in the ignition coil to initiate a spark in a spark plug coupled with the ignition coil; and

in response to the spark being initiated in the spark plug, drive the resonant circuit at a second frequency to maintain the spark in the spark plug for combustion of a fuel mixture, and

the control circuit being further configured, after the combustion of the fuel mixture, to disable the driving circuit.

11. The ignition circuit of claim 10 , wherein the resonant circuit further includes at least one resonant capacitor.

12. The ignition circuit of claim 11 , wherein a resonant capacitor of the at least one resonant capacitor is coupled in series with the primary winding of the ignition coil.

13. The ignition circuit of claim 11 , wherein a resonant capacitor of the at least one resonant capacitor is coupled in parallel with the primary winding of the ignition coil.

14. The ignition circuit of claim 11 , wherein a resonant capacitor of the at least one resonant capacitor is coupled in parallel with a secondary winding of the ignition coil.

15. The ignition circuit of claim 11 , wherein the resonant circuit further includes an inductor coupled between the driving circuit and the primary winding of the ignition coil.

16. The ignition circuit of claim 10 , wherein the driving circuit includes one of a half-bridge circuit or a full-bridge circuit.

17. The ignition circuit of claim 16 , wherein:

the control circuit is configured to provide complementary signals of the first frequency or the second frequency to the driving circuit; and

the driving circuit, in response to the complementary signals of the first frequency or the second frequency, is configured to provide a respective alternating-current signal of the first frequency or the second frequency to the resonant circuit.

18. An ignition circuit comprising:

a control circuit that is coupled with an engine control unit (ECU) to receive a command signal from the ECU;

a driving circuit coupled with the control circuit; and

a resonant circuit coupled with the driving circuit, the resonant circuit including a primary winding of an ignition coil,

the control circuit and the driving circuit being configured, in response to a first edge of the command signal, to:

drive the resonant circuit at a first frequency to generate a voltage in the ignition coil to initiate a spark in a spark plug coupled with the ignition coil; and

in response to the spark being initiated in the spark plug, drive the resonant circuit at a second frequency to maintain the spark in the spark plug, and

the control circuit being further configured, in response to a second edge of the command signal that is opposite the first edge, to disable the driving circuit.

19. The ignition circuit of claim 18 , wherein the driving circuit includes one of a half-bridge circuit or a full-bridge circuit.

20. The ignition circuit of claim 18 , wherein the resonant circuit further includes at least one resonant capacitor coupled with the ignition coil.