| 摘要 |
PURPOSE:To prevent image or generation of booming sounds and provide a wide dimming range by furnishing a pulsed wave generation circuit and a cathode-ray tube drive circuit, and setting the frequency of the drive voltage, which is to light a cathode-ray tube, to at least over the audible band. CONSTITUTION:A pulse wave generation circuit 1 emits pulse with variable frequency, while a driver circuit 2 receives the pulse, makes resonance and oscillation accordingly, and supplies current with sufficient voltage for driving a cathode-ray tube 3. The Off time between pulses is varied by changing the frequency of the pulses, and accordingly the intervals of drive voltage generation for the cathode-ray tube 3 is changed. That is, the brightness can be increased if the Off time if shortened by narrowing the pulse intervals for the specified cyclic periods so that the waveforms are continued, while the brightness can be lowered if the Off time is prolonged by lengthening the cyclic periods. Thus generation of booming sounds and image flow can be prevented by setting the pulse repeating frequency to at least over the audible band. |
