Abstract: A driving circuit for LED includes: at least one LED; a light emission driving circuit having a first PWM unit and a power converting unit generating a driving current according to a signal generated by the first PWM unit and sending the driving current to the LED; a shunt parallel-connected with the LED; and a signal generating unit for generating a signal to switch on or off an electrical connection between the shunt and the light emission driving circuit. When the signal from the signal generating unit is at a high level, the electrical connection is switched on so that a majority of the residual driving current flows to the shunt.

Abstract: An ultrasonic sensing method and an ultrasonic sensing device are provided. The ultrasonic sensing device includes a microprocessor, a signal-driving module and a transducer module. The microprocessor generates a first driving signal with a first frequency to the signal-driving module. The signal-driving module drives the transducer module to emit a first sensing signal to a target object in response to the first driving signal. Then, a first echo signal received by the transducer is transmitted to the microprocessor to calculate a first time of flight. In a similar manner, a second time of flight is obtained based on a second driving signal with a second frequency. The microprocessor determines a final time of flight according to the first time of flight or the second time of flight.

Abstract: A signal decay time adjusting method is used in an ultrasonic transducer. Firstly, a first driving signal is generated by a pre-processing module. When the first driving signal is received, an ultrasonic transmitting/receiving module generates vibration and transmits a sensing wave according to the first driving signal. Then, the pre-processing module stops generating the first driving signal so that the vibration generated within the ultrasonic transmitting/receiving module is decayed as a decay signal. Then, a second driving signal is generated by the pre-processing module according to the first driving signal, and the second driving signal is transmitted to the ultrasonic transmitting/receiving module. When the second driving signal is received, the decay signal is offset according to the second driving signal, so that a decay time of the decay signal is shortened. When the sensing wave is reflected by an object, a reflective wave is received by the ultrasonic transmitting/receiving module.

Abstract: A driving circuit for LED includes: at least one LED; a light emission driving circuit having a first PWM unit and a power converting unit generating a driving current according to a signal generated by the first PWM unit and sending the driving current to the LED; a shunt parallel-connected with the LED; and a signal generating unit for generating a signal to switch on or off an electrical connection between the shunt and the light emission driving circuit. When the signal from the signal generating unit is at a high level, the electrical connection is switched on so that a majority of the residual driving current flows to the shunt.

Abstract: A driving circuit for instant LED shutdown includes: a light emission driving circuit having a first PWM unit and a power converting unit, the power converting unit generating a driving current signal according to a signal generated by the first PWM unit, so as to drive the LED; a shunt parallel-connected with the LED for shunting a residual driving current after the power converting unit is turned off; and a second PWM unit for generating a signal which level is opposite to that of the signal from the first PWM unit so as to switch on or off an electrical connection between the shunt and the light emission driving circuit. When the signal from the second PWM unit is at a high level, the electrical connection is switched on so that a majority of the residual driving current flows to the shunt, thereby achieving instant LED shutdown.