Circuit and method for coupling electrical energy to a resonated inductive load

A method of operating a coupling circuit to couple a supply of electrical energy to an inductive load device, wherein:

• the coupling circuit comprises a switching circuit, an energy transfer capacitance and a resonating capacitance;
• the resonating capacitance and the inductive load device together form a resonated load circuit having a natural resonant frequency;
• and
• the method comprises the steps of:
• 1. configuring the switching circuit in a charging configuration in which the energy transfer capacitance is connected to the supply of electrical energy;
• 2. charging the energy transfer capacitance from the supply of electrical energy;
• 3. configuring the switching circuit in an injecting configuration in which the energy transfer capacitance is connected to the resonated load circuit;
• 4. at least partly discharging the energy transfer capacitance into the resonated load circuit, thereby injecting a discrete pulse of energy into the resonated load circuit;
• and
• 5. repetitively performing Steps 1, 2, 3 and 4, to transfer energy from the supply of electrical energy to the inductive load device;
• and wherein
• the energy transferred to the inductive load device circulates in the resonated load circuit at an oscillation frequency which is near or equal to the natural resonant frequency;
• and
• there is no injection of energy from the energy transfer capacitance into the resonated load circuit while energy for charging the energy transfer capacitance is being delivered from the supply to the switching circuit.

A method of operating a coupling circuit to couple a supply of electrical energy to an inductive load device, wherein:

• the coupling circuit comprises a switching circuit, a first energy transfer capacitance, a second energy transfer capacitance, and a resonating capacitance;
• the resonating capacitance and the inductive load device together form a resonated load circuit having a natural resonant frequency;
• and
• the method comprises the steps of:
• A. configuring the switching circuit in a first injecting configuration in which the first energy transfer capacitance is connected to the resonated load circuit;
• B. at least partly discharging the first energy transfer capacitance into the resonated load circuit, thereby injecting a discrete pulse of energy into the resonated load circuit;
• C. configuring the switching circuit in a first charging configuration in which the first energy transfer capacitance is connected to the supply of electrical energy;
• D. charging the first transfer capacitance from the supply of electrical energy;
• E. configuring the switching circuit in a second injecting configuration in which the second energy transfer capacitance is connected to the resonated load circuit;
• F. at least partly discharging the second energy transfer capacitance into the resonated load circuit, thereby injecting a discrete pulse of energy into the resonated load circuit;
• G. configuring the switching circuit in a second charging configuration in which the second energy transfer capacitance is connected to the supply of electrical energy;
• H. charging the second energy transfer capacitance from the supply of electrical energy;
• I. repetitively performing Steps A to H inclusive, to transfer energy from the supply of electrical energy to the inductive load device;
• and wherein:
• the energy transferred to the inductive load device circulates in the resonated load circuit at an oscillation frequency which is near or equal to the natural resonant frequency;
• and
• there is no injection of energy from the first energy transfer capacitance into the resonated load circuit while energy for charging the first energy transfer capacitance is being delivered from the supply to the switching circuit, and no injection of energy from the second energy transfer capacitance into the resonated load circuit while energy for charging the second energy transfer capacitance is being delivered from the supply to the switching circuit.