US Patent 8183940 Temperature control device

A thermostatic-chamber temperature control device includes: a heating element for heating a thermostatic chamber; a bridge circuit having a temperature sensitive element whose resistance value varies in accordance with the temperature of the heating element; a detection circuit for detecting an unbalanced voltage of the bridge circuit; a PWM signal generating circuit for generating a PWM signal corresponding to the unbalanced voltage detected by the detection circuit; and a switching element that has a current output terminal connected to the heating element and a current input terminal connected to a power supply circuit and is driven on the basis of the PWM signal generated by the PWM signal generating circuit.