A PWM signal generation circuit and a PWM control circuit are provided in which the duty ratio is easily changed and which can also avoid adverse impact from ambient temperature changes and the like. At the beginning of charging a capacitor with a current flow, a voltage level at a connection point between the negative input terminal of a comparator and the capacitor is still below a charging threshold. When the charging threshold is exceeded, the comparator is inverted to a low state and a current flows into an output point of the comparator to start discharging the capacitor. At the beginning of discharging from the capacitor, the voltage level at the connection point is still above the discharging threshold. However, when the voltage level falls below the discharging threshold, the comparator returns to a high state, and the charging operation again takes over.