| 摘要 |
PURPOSE: To enlarge a control range in the generation of PWM signals for controlling the input side of a chopper so as to fixedly maintain a high voltage by setting sawtooth-shaped waves to a specified waveform. CONSTITUTION: A power source Eb2 charges a capacitor C2 through a resistor between the source and drain of a transistor Q3 and the transistor Q2 discharges the capacitor C2 in synchronism with the frequency of horizontal driving signals and generates the sawtooth-shaped waves SAW. The amplitude voltage of the sawtooth-shaped waves SAW is stored in the capacitor C3, the result of comparing it with a reference voltage Eb3 in a comparator G1 is fed back to the base of the transistor Q3 and it is maintained to be equal to the reference voltage Eb3 regardless of the frequency of the horizontal driving signals. In this case, such as appropriately setting the capacitance of the capacitor C2 or the like, the waveform of the sawtooth-shaped waves SAW is set to the waveform for which a rising rate is successively reduced such as an exponential function or the like. The change of a feedback loop gain when the frequency of the horizontal driving signals is changed in a wide range is suppressed. |
