| 摘要 |
PURPOSE:To prevent the occurrence of non-combustion even when an air pressure is exerted during MIN combustion by a method wherein a lower limit limiter is disposed for an peration amount of proportional control for a combustion fan, and an operation amount of proportional control is prevented from reduction to a value lower than a value set at a limiter. CONSTITUTION:Running of a combustion 2 is controlled by a number of revolutions control circuit 6 during ordinary combustion but during MIN combustion, control through which regulation to a value lower than a value set at a limiter circuit 5 is effected is rendered ineffective. Namely, during ordinary combustion, a voltage of an input voltage waveform between a - b responding to a waveform between c - d decided by the number of revolutions control circuit 6 is applied on the combustion fan 2 to drive the combustion fan 2 to drive combustion fan 2. However, a phase angle cut width is set to, for example, B at the limiter circuit 5 and even when a signal by means of which a cut width is increased to a value higher than the set cut width is outputted from the number of revolutions control circuit 6 during MIN combustion, the cut width is incapable of being increased to a value higher than B. |
