The forced frequency may cause problems if the resonant
frequency of the coil drifts due to heating or some external force. The
feedback approach will correct for it, but propagation delays through the
semiconductors must be minimized to ensure minimum phase shift. The role
of this subsystem is yet to be determined. Due to the bandwidth limit of
the FET device we have chosen, the frequency of operation will be <10MHz,
which misses the 13MHz FCC free band mentioned below.
Implementation
The flame control circuit controls the base size of the flame (i.e. the
size when the input volume is zero; needed to keep the flame "alive") and
provides a way of quickly changing this base size by a small amount via
the audio signal.
- The block diagram shown utilizes pulse width modulation (PWM) to
create a signal suitable for use in the high voltage oscillator
subsystem.
- The high frequency oscillator will be implemented using CMOS gate
technology because CMOS gates have a large operation bandwidth. This
will provide a square wave of approximately 13.56 MHz. 13.56 MHz is a
free frequency band as regulated by the FCC chosen to reduce interference
to other electronic devices[1].
- The PWM signal will control current in the circuit and create
inductive voltage spikes by way of a solid-state device such as a
Field-Effect Transistor (FET). The voltage spikes will constantly change
the corona discharge output size, producing sound waves.
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