Resistance-measuring circuit and electronic device using the same

An electronic device comprising:

• a sensor;
• and
• a resistance-measuring circuit for measuring the resistance of the sensor, the resistance-measuring circuit comprising:
• a controller for outputting a PWM signal and further adjusting the duty cycle of the PWM signal;
• and
• a sampling circuit electrically connecting the controller to the sensor, and used for processing the PWM signal and transmitting the processed PWM signal to the sensor;
• wherein the sampling circuit samples the signal outputted from the sensor to generate a sampled signal with the voltage thereof changing according to the change of the duty cycle of the PWM signal, and further transmits the sampled signal to the controller;
• the controller obtains the real-time duty cycle of the PWM signal when the voltage of the sampled signal reaches a threshold voltage, and further calculates the resistance of the sensor according to the obtained real-time duty cycle of the PWM signal and the threshold voltage;
• wherein the sampling circuit comprises a voltage-converting unit and a sampling unit, the voltage-converting unit is used to convert the PWM signal to a direct-voltage signal which changes according to the change of the duty cycle of the PWM signal and further transmit the direct-voltage signal to the sensor to be processed, the sampling unit is used to sample the direct-voltage signal processed by the sensor to generate the sampled signal;
• wherein the controller comprises an output port for outputting the PWM signal, and an input port for receiving the sampled signal generated by the sampling circuit;
• and wherein the sampling unit comprises a first resistor, the voltage-converting unit comprises a capacitor and a second resistor, a terminal of the sensor is electrically connected to the output port of the controller via the second resistor, the other terminal of the sensor is grounded via the first resistor;
• a terminal of the capacitor is electrically connected between the sensor and the second resistor, and the other terminal of the capacitor is grounded;
• the input port of the controller is electrically connected between the sensor and the second resistor.