Class e coil driver with switched capacitor ask modulation
AssigneeAlfred E. Mann Foundation for Scientific Research
InventorEdward K. F. Lee
Life of this patent
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Abstract
A feedback controlled coil driver with ASK modulation is disclosed. A class E coil driver drives an LC circuit to generate a magnetic signal via the inductor. A modulation capacitor is coupled to the LC circuit to modulate the coil driver signal. The voltage across the coil driver switch is sampled. The difference between the sampled voltage and a reference voltage is integrated and compared to a ramp voltage to obtain an optimal on time for the coil driver switch such that coil current is maximized.
Claims31
A feedback controlled coil driver capable of amplitude modulation comprising:
- an LC tank circuit;
- a direct current power source coupled to the LC tank circuit;
- a first switch interconnected between the LC tank circuit and ground to switchably couple the LC tank circuit between the power source and ground when the first switch is turned on, wherein the point of interconnection between the LC tank circuit and the first switch provides a coil driver output voltage VL;
- a control voltage generator configured to sample VL at the instant when the first switch is turned on and generate a voltage VIO equal to the integral over time of the difference between the sampled VL and a prescribed reference voltage;
- a voltage ramp generator arranged to provide a ramp voltage at such time when the first switch couples the LC tank circuit to ground;
- a first comparator arranged to compare VIO to the ramp voltage;
- a first switch driver coupled to the first comparator, the first switch driver being arranged to turn the first switch on at an operating frequency and arranged to turn the first switch off when the ramp voltage exceeds VIO;
- a modulation capacitor;
- a second switch coupled to the modulation capacitor and configured to couple the modulation capacitor into and out of the LC tank circuit;
- and
- a second switch driver coupled to a data signal and arranged to turn the second switch on and off based on the data signal.
A method of driving a coil in an LC circuit to generate an amplitude modulated signal comprising the steps of:
- coupling an LC tank circuit to ground at controlled times, the LC tank circuit being configured to generate a coil drive voltage (VL) and having a resonant frequency;
- monitoring the VL to generate an on time control voltage (VIO);
- decoupling the LC tank circuit from ground after an on time, wherein the on time is based on the on time control voltage;
- and
- changing the resonant frequency of the LC tank circuit to modulate data onto the coil drive voltage.
A feedback controlled coil driver circuit comprising:
- an LC tank circuit having a coil drive voltage;
- a first switch configured to switchably couple the LC tank circuit between a power source and ground;
- a controller coupled to the first switch, a pulse signal generated by the controller, having a controllable on time, wherein during such on time, the first switch couples the LC tank circuit between the power source and ground;
- a feedback controller configured to provide a feedback control signal to control the on time of the pulse signal;
- a modulation capacitor coupled to the LC tank circuit;
- a second switch interconnected between the modulation capacitor and ground, wherein the second switch couples the modulation capacitor to the LC tank circuit based on a data signal.
A method of generating a modulated signal comprising:
- driving an LC circuit at an operating frequency, the LC circuit having a coil drive voltage;
- and
- coupling a modulation capacitor to the LC circuit to modulate the amplitude of the coil drive voltage.
A method of modulating a signal in a power transfer system, the power transfer system comprising an LC circuit and having an operating frequency, and the LC circuit having a coil drive voltage and a resonant frequency, the method comprising:
- changing the resonant frequency of the LC circuit;
- and
- controlling the driving of the LC circuit to keep the circuit oscillating at the operating frequency.
Dependencies are inferred from the claim text.