Switched reactance modulated E-class oscillator design
A modulated Class E transmitter is disclosed. In one embodiment of the invention, the modulated Class E oscillator achieves high coil currents (˜1 A) and voltages (˜500V) with low power components by precisely timed injection of current when the oscillating current in the inductor passes through zero. A detector circuit is used to trigger the current injection at the appropriate instant regardless of changes in the resonant frequency of the system. Its phase can be adjusted to compensate for propagation delays in the drive circuitry, while amplitude modulation is accomplished by switching in additional reactive conductance to increase the current injected into the tank circuit. Frequency modulation is accomplished in an alternate embodiment.
1. A switched reactance modulated E-class oscillator comprising:
a tank circuit including an inductance and a capacitance for helping to generate an oscillating signal;
a zero crossing detector in communication with said tank circuit for detecting zero crossings of the oscillating signal;
a drive pulse generator in communication with said tank circuit and said zero crossing detector for injecting injection signals into said tank circuit in response to zero crossings detected by said zero crossing detector;
a reactance;
an electronic switch; and
a modulator in communication with said electronic switch for receiving a modulating signal and for causing said tank circuit to be loaded with said reactance in synchronism with the modulating signal using said electronic switch;
whereby the oscillator operates substantially in the E-class mode.
2. The oscillator of claim 1 wherein:
said tank circuit is a series resonant tank circuit;
said reactance includes substantial capacitive reactance; and
said inductance and said capacitance are connected in series.
3. The oscillator of claim 2 wherein:
said capacitance includes two capacitors connected in series;
said switch causes said capacitive reactance to be added in parallel with one of said capacitors; and
said modulator causes substantial amplitude modulation.
4. The oscillator of claim 2 wherein:
said switch causes said capacitive reactance to be added in parallel with said inductor; and
said modulator causes substantial frequency modulation.
5. A source of power and control signals for an implanted BION comprising:
a tank circuit including an inductance and a capacitance for helping to generate an oscillating signal, said inductance forming a coil that acts as an antenna for radiating the power and control signals;
a zero crossing detector in communication with said tank circuit for detecting zero crossings of the oscillating signal;
a drive pulse generator in communication with said tank circuit and said zero crossing detector for injecting injection signals into said tank circuit in response to zero crossings detected by said zero crossing detector;
a reactance;
an electronic switch; and
a modulator in communication with said electronic switch for receiving a modulating signal and for causing said tank circuit to be loaded with said reactance in synchronism with the modulating signal using said electronic switch;
whereby the oscillator operates substantially in the E-class mode.
6. The oscillator of claim 5 wherein:
said tank circuit is a series resonant tank circuit;
said reactance includes substantial capacitive reactance; and
said inductance and said capacitance are connected in series.
7. The oscillator of claim 6 wherein:
said capacitance includes two capacitors connected in series;
said switch causes said capacitive reactance to be added in parallel with one of said capacitors; and
said modulator causes substantial amplitude modulation.
8. The oscillator of claim 6 wherein:
said switch causes said capacitive reactance to be added in parallel with said inductor; and
said modulator causes substantial frequency modulation.