Apparatus and method for controlling temperature

A temperature control apparatus comprising:

• an analog to digital (AD) converter digitally-converting a measurement value transmitted from a plurality of temperature sensors;
• a controller comparing the measurement value transmitted from the AD converter with a preset desired value to perform a proportional integral derivative (PID) calculation;
• and
• an output unit transmitting, to outside of the temperature control apparatus, a pulse width modulation (PWM) control signal that has been transmitted from the controller,
• wherein an input-side isolator for isolation for each of the plurality of temperature sensors is provided between the AD converter and the temperature sensor,
• the input-side isolator is connected to each of the plurality of temperature sensors, and
• the controller transmits a control signal to the input-side isolator sequentially according to a determined order,
• wherein the input-side isolator comprises a first solid state relay (SSR) and a second solid state relay (SSR) connected to a corresponding temperature sensor,
• wherein each of the first SSR and the second SSR comprises a light emitting diode, and a phototransistor starting operations by light emitted from the light emitting diode,
• wherein the controller transmits a low signal to the first SSR of a first input-side isolator according to the determined order,
• wherein an anode of the light emitting diode of the first SSR is electrically connected to a cathode of the light emitting diode of the second SSR based on the low signal, which allows a voltage source (VCC) to be supplied to the light emitting diode of the first SSR and the light emitting diode of the second SSR, and an anode of the light emitting diode of the second SSR is connected to the VCC, and
• wherein one terminal of the phototransistor of the first SSR is connected to a plus terminal of the corresponding temperature sensor, and one terminal of the phototransistor of the second SSR is connected to a minus terminal of the corresponding temperature sensor.