| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem when a quasi-sinusoidal wave is generated by utilizing the resonance caused by the capacity component of a piezoelectric transformer and an inductance component of the preceding stage, that the deviation of a resonance frequency becomes larger due to the temperature characteristic and tolerance of an LC. SOLUTION: A variable voltage device 1 outputs a set voltage V1 to an integrator 2, so that the secondary-side current Is of the piezoelectric transformer 6 becomes a set value. The integrator 2 outputs a difference voltage V1 which is obtained by integrating the voltage Vd-V1 obtained, by subtracting the set voltage V1 from the voltage Vd corresponding to the current Is to a V/F converter 3. The converter 3 outputs the converted driving frequency f of the transformer 6 to a class-D amplifier 4. The amplifier 4 outputs a PWM rectangular wave, obtained by A/D-converting the frequency f and the rectangular wave, is impressed on the primary side of the transformer 6 directly via an LPF or via a wound transformer T. In this case, only the fundamental wave of the PWM rectangular wave is impressed on the primary side of the transformer 6, because the higher harmonic component of the rectangular wave is deleted by means of the LPF. |
