| 摘要 |
PROBLEM TO BE SOLVED: To maintain the highly efficient high-output performance of a PWM device without sacrificing the accuracy of PWM waveforms at a low output level, by adjusting the power supply voltage and the pulse width of PWM output signals in accordance with the level of input signals. SOLUTION: A PWM device 300 adjusts the amplitude and pulse width of PWM signals, by using an external select signal connected to a switch 350 and a selection circuit 325 connected to a pulse width modulator 320 through a SELECT line. The select signal connects either one of power supply terminals LV and HV to an amplifier 340 and, when the power supply terminal LV or HV is connected to the amplifier 340, the selection circuit 325 adjusts the pulse width of a PWM signal generated from the pulse width modulator 320 based on a high clock speed divided by a fixed integer decided from the voltage level of the select signal. Therefore, a relatively low switching voltage can improve the accuracy and output converting efficiency of the PWM device 300 when the device 300 is operated under a low-output state and, even when the switching voltage becomes higher, the output performance of the device 300 can be maintained at a high level. |
