| 摘要 |
PURPOSE:To prevent control secondary voltage (flow rate) from being varied substantially even if control electric current is varied by a method wherein when a proportional valve driving signal becomes a desired value, resistor elements are connected in parallel with a coil of the proportional valve. CONSTITUTION:When a thermal request is made a balanced condition of a bridge circuit composed of a thermal sensing element 1 and the resistors 5, 6 and 7 is collapsed, a transistor 9 is turned ON and a proportional valve driving signal (i) corresponding to a signal of the temperature responsive element 1 is flowed in the coil 3 of the proportional valve 12. When the signal becomes the desired proportional valve driving signal (i), that is, when the potential level provided by the resistor 11 and the reference resistors 23 and 24 becomes 0, an operation amplifier 25 is turned OFF, a base current of the transistor 29 is flowed, the transistor 29 is turned On and the resistor element 30 is connected in parallel with the coil 3. Thereafter, the proportional valve driving signal (i) is divided into an electrical current (i1) flowing through the coil 3 and and a resistance (i2) flowing through the coil 3 in response to the constant of the resistor element 30 is decreased and thereafter it is increased with a little gain. |
