A power supply device includes a pulse frequency modulation controller circuitry and a cycle controller circuitry. The pulse frequency modulation controller circuitry is configured to adjust a transiting speed of a first signal according to at least one control bit, and to compare the first signal with a first reference voltage to generate a second signal, and to generate a driving signal to a power converter circuit according to an output voltage, a second reference voltage, and the second signal, in which the power converter circuit is configured to generate the output voltage according to the driving signal. The cycle controller circuitry is configured to detect a frequency of the driving signal according to a clock signal having a predetermined frequency, in which the predetermined frequency is set based on a frequency range capable of being heard by humans.

A power supply device includes a pulse frequency modulation controller circuitry and a cycle controller circuitry. The pulse frequency modulation controller circuitry is configured to adjust a transiting speed of a first signal according to at least one control bit, and to compare the first signal with a first reference voltage to generate a second signal, and to generate a driving signal to a power converter circuit according to an output voltage, a second reference voltage, and the second signal, in which the power converter circuit is configured to generate the output voltage according to the driving signal. The cycle controller circuitry is configured to detect a frequency of the driving signal according to a clock signal having a predetermined frequency, in which the predetermined frequency is set based on a frequency range capable of being heard by humans.

A detection circuit for detecting a clock signal includes a multiplexer, a digital-to-analog converter, a comparator, and a counter. The multiplexer outputs either a first signal or a second signal as a selection signal. The digital-to-analog converter outputs a reference voltage according to the selection signal. The comparator compares the clock signal to the reference voltage to generate a comparison signal. The counter counts a reference clock signal to generate an overflow signal, and resets the overflow signal according to the comparison signal. The overflow signal indicates the amplitude of the clock signal.

A detection circuit for detecting a clock signal includes a multiplexer, a digital-to-analog converter, a comparator, and a counter. The multiplexer outputs either a first signal or a second signal as a selection signal. The digital-to-analog converter outputs a reference voltage according to the selection signal. The comparator compares the clock signal to the reference voltage to generate a comparison signal. The counter counts a reference clock signal to generate an overflow signal, and resets the overflow signal according to the comparison signal. The overflow signal indicates the amplitude of the clock signal.

In one implementation, a circuit includes: a comparator; a shift register chain coupled to the comparator; and one or more converters coupled to respective shift registers of the shift register chain, wherein the one or more converters are configured to convert a source of current from a first voltage to a second voltage, and wherein the circuit is configured to selectively transmit an output signal to the one or more converters. In one implementation, the circuit is configured to selectively control modulation for the one or more converters.

In one implementation, a circuit includes: a comparator; a shift register chain coupled to the comparator; and one or more converters coupled to respective shift registers of the shift register chain, wherein the one or more converters are configured to convert a source of current from a first voltage to a second voltage, and wherein the circuit is configured to selectively transmit an output signal to the one or more converters. In one implementation, the circuit is configured to selectively control modulation for the one or more converters.

A proximity sensor comprises a reference inductor, a first set of sensor inductors, a first set of comparators, each comparator of the first set of comparators corresponding to one of the sensor inductors of the first set of sensor inductors, and an alternating current voltage source to output a sinusoidal voltage to the reference inductor and each of the sensor inductors. Each comparator of the first set of comparators receives a voltage across the reference inductor as a reference voltage and each comparator of the first set of comparators receives a voltage across a corresponding sensor inductor as an input voltage.

A proximity sensor comprises a reference inductor, a first set of sensor inductors, a first set of comparators, each comparator of the first set of comparators corresponding to one of the sensor inductors of the first set of sensor inductors, and an alternating current voltage source to output a sinusoidal voltage to the reference inductor and each of the sensor inductors. Each comparator of the first set of comparators receives a voltage across the reference inductor as a reference voltage and each comparator of the first set of comparators receives a voltage across a corresponding sensor inductor as an input voltage.

An ON/OFF detection device is configured to detect ON/OFF of an input unit using a load sensor, and includes a threshold setting unit, a comparison unit, and an ON/OFF determination unit. The threshold setting unit is configured to set a threshold value with respect to a previous detection value of the load sensor. The comparison unit is configured to compare the threshold value and a current detection value. The ON/OFF determination unit is configured to determine ON/OFF of the input unit based on a comparison result. When a previous determination result of the ON/OFF determination unit is ON, the threshold setting unit is configured to set the threshold value to be lower than the previous detection value. When the previous determination result of the ON/OFF determination unit is OFF, the threshold setting unit is configured to set the threshold value to be higher than the previous detection value.

An ON/OFF detection device is configured to detect ON/OFF of an input unit using a load sensor, and includes a threshold setting unit, a comparison unit, and an ON/OFF determination unit. The threshold setting unit is configured to set a threshold value with respect to a previous detection value of the load sensor. The comparison unit is configured to compare the threshold value and a current detection value. The ON/OFF determination unit is configured to determine ON/OFF of the input unit based on a comparison result. When a previous determination result of the ON/OFF determination unit is ON, the threshold setting unit is configured to set the threshold value to be lower than the previous detection value. When the previous determination result of the ON/OFF determination unit is OFF, the threshold setting unit is configured to set the threshold value to be higher than the previous detection value.