| 摘要 |
PROBLEM TO BE SOLVED: To reduce power consumption by extending switching time in accordance with the fall of frequency when the frequency is allowed to fall by power management control to reduce noise and limit temperature rise or the like. SOLUTION: A constant voltage circuit FVC0 uses voltage Vout outputted by converting voltage Vin supplied to a voltage control part PVC1 as constant voltage and outputs a pulse signal of fixed frequency. The circuit FVC0 receives a frequency suppression signal Ctr1-F from a frequency control part PFC as power management control and sets up its frequency to a low value. The circuit FVC0 suppressed to low frequency generates a margin in operation voltage due to the reduction of noise, the limit of temperature rise or the like. Therefore a voltage suppression signal Ctr1-V is sent from the frequency control part PFC to the voltage control part PVC1 so as to allow voltage to fall down to an operatable voltage value. |
