Frequency tracking piezoelectric transformer power converter with simultaneous two-parameter control

A piezoelectric transformer power converter circuit comprising

• a regulation control stage that generates a regulation control signal responsive to an electrical parameter measurement of the converter load,
• a frequency control stage that generates a frequency control signal responsive to an operating state measurement of a piezoelectric transformer, said frequency control circuit including:
• a first voltage measurement circuit that performs a phase measurement of input voltage of the piezoelectric transformer and generates a first phase signal,
• a second voltage measurement circuit that performs a phase measurement of the output voltage of piezoelectric transformer and generates a second phase signal,
• a delay line coupled to said second voltage measurement circuit that receives the second phase signal and creates a phase delay on the second phase signal, and
• a phase difference detector coupled to said first voltage measurement circuit and said delay line that outputs a signal corresponding to a difference in phase between the first phase signal and the delayed second phase signal;
• and
• a simultaneous control circuit that provides simultaneous control of the frequency and power output of a switch-mode power circuit responsive to the regulation and frequency control signal, said simultaneous control circuit including:
• a voltage controlled oscillator that generates a periodic output signal having a frequency dictated by the frequency control signal, and
• a phase shift bridge control circuit that generates a set of signals that control a frequency and power output of a switch-mode power circuit responsive to the regulation and frequency control signals.

A method of operation of a piezoelectric transformer power converter having a power stage, a regulation control stage, and a frequency control stage, the method comprising:

• measuring a parameter of an output of the power stage;
• generating a regulation control signal that is representative of the error between a desired electrical regulation set-point and a measured electrical parameter of the output of the power stage;
• measuring a first operating parameter and a second operating parameter of a power stage;
• generating a frequency control error signal that is representative of the error between the first and second measured operating parameters of the power stage;
• and
• generating a frequency control signal having a periodic wave with a frequency responsive to the frequency control error signal;
• generating a drive signal for a piezoelectric transformer that simultaneously controls (i) input power from a coupled input power source responsive to the regulation control signal, and (ii) operational frequency of the piezoelectric transformer responsive to the frequency control signal;
• wherein one of the first and second operating parameter measurements is subjected to a phase delay thereby controlling an operating point lock location of the piezoelectric transformer.