Method for detecting power interruption duration (t 0) of an electronic device which is provided with at least one temperature sensor for detecting temperature of the electronic device and at least one temperature sensor for detecting temperature of a printed circuit board, the method comprising the steps of: establishing a curve model of linearly synthesized values of temperature sensor readings versus time; storing the curve model in an internal memory of the microprocessor; conveying, after power-on of the electronic device, each acquired initial temperature value (a 0i) by a respective temperature sensor to a microprocessor through an analog-to-digital conversion module; calculating the linearly synthesized value of the electronic device for this time with the stored curve model established in step 1, and storing the linearly synthesized value within the microprocessor as a basis for calculating the power interruption duration (t 0) thereafter; conveying, when the electronic device is powered on again after power interruption, each initial temperature value (a 0i) reacquired by the temperature sensors to the microprocessor through the analog-to-digital conversion module; calculating the power interruption duration for this time with the curve model established in step 1 and based on the linearly synthesized value stored in the microprocessor calculated in step 4, and storing the power interruption duration (t 0) for this time, while recording the power-on duration (tp) for this time by the microprocessor; calculating the linearly synthesized value for this time, and storing the linearly synthesized value within the microprocessor as a basis for calculating the power interruption duration (t 0) again thereafter characterized in that the curve model of linearly synthesized values of temperature sensor readings versus time is represented as: ST = ∑ i = 1 n k i ⋅ a 0 i + a 1 i 1 − 1 / e t / C i in which: ST is a linearly synthesized value of temperature sensor readings; n is a number of the temperature sensors, n ≥ 2; k i is a synthesized coefficient of the temperature value; and k i is controlled to be − 1 < k i < 1 and k i ≠ 0; a 0 i is an initial temperature value acquired by a temperature sensor; a 1 i is a scaling factor of a temperature sensor output, and a 1 i is controlled to be − 200 < a 1 i < 200 and a 1 i ≠ 0; C i is a time constant, -1 ≤ C ≤ 10000; and t is a power-on duration or power-interruption duration, wherein the power-on duration is represented by t p, and the power-interruption duration is represented by t o. establishing a curve model of linearly synthesized values of temperature sensor readings versus time; storing the curve model in an internal memory of the microprocessor; conveying, after power-on of the electronic device, each acquired initial temperature value (a 0i) by a respective temperature sensor to a microprocessor through an analog-to-digital conversion module; calculating the linearly synthesized value of the electronic device for this time with the stored curve model established in step 1, and storing the linearly synthesized value within the microprocessor as a basis for calculating the power interruption duration (t 0) thereafter; conveying, when the electronic device is powered on again after power interruption, each initial temperature value (a 0i) reacquired by the temperature sensors to the microprocessor through the analog-to-digital conversion module; calculating the power interruption duration for this time with the curve model established in step 1 and based on the linearly synthesized value stored in the microprocessor calculated in step 4, and storing the power interruption duration (t 0) for this time, while recording the power-on duration (tp) for this time by the microprocessor; calculating the linearly synthesized value for this time, and storing the linearly synthesized value within the microprocessor as a basis for calculating the power interruption duration (t 0) again thereafter ST is a linearly synthesized value of temperature sensor readings; n is a number of the temperature sensors, n ≥ 2; k i is a synthesized coefficient of the temperature value; and k i is controlled to be − 1 < k i < 1 and k i ≠ 0; a 0 i is an initial temperature value acquired by a temperature sensor; a 1 i is a scaling factor of a temperature sensor output, and a 1 i is controlled to be − 200 < a 1 i < 200 and a 1 i ≠ 0; C i is a time constant, -1 ≤ C ≤ 10000; and t is a power-on duration or power-interruption duration, wherein the power-on duration is represented by t p, and the power-interruption duration is represented by t o.