Abstract: A speaker driver circuit driven by positive and negative voltages, comprising: at least one operational amplifier providing an output to a headphone speaker, and a voltage converter receiving a supplied voltage (VDD), generating r-fold positive and negative voltages (r·VDD and ?r·VDD, wherein r is any positive real number except 1) according to the supplied voltage, and supplying the positive and negative voltages to the operational amplifier for its high and low operation voltage levels respectively.

Abstract: The present invention discloses a multi-voltage headphone driver circuit comprising: at least one operational amplifier having an output supplied to a headphone speaker, the operational amplifier receiving a first power supply as its high operation voltage; a charge pump receiving a second power supply to generate a negative voltage corresponding to the second power supply in magnitude; and an m-fold circuit multiplying the negative voltage by m and providing the result to the operational amplifier as a low operation voltage thereof, wherein m is a real number.

Abstract: A switching amplifier has a network including current sources and resistors connected to the two output terminals of the H-bridge of the switching amplifier, to provide a small current to the load connected between the two output terminals at zero input, whereby the common mode voltage bouncing is reduced and the switching amplifier has less power consumption and reduced electro-magnetic interference.

Abstract: In a class-D amplifier, the input signal is compared with a carrier signal to generate a basic PWM signal, the PWM signal is then sent to a pulse processing unit, and by comparing with a basic periodic signal, half-width of the output PWM signal is extracted. Then, in the pulse processing unit, the half-width PWM pulse signal is used to generate a complete pulse whose width equals to the output PWM signal. The output power of the class-D amplifier can be kept as large as that by using differential input signals although the input signal is single-end and the entire signal processing path is kept single-ended.

Abstract: A conversion circuit is provided for a 1.5-bit ?-? class-D amplifier to improve the feedback linearity of the class-D amplifier, by periodically inverting and mixing a first positive feedback signal and a first negative feedback signal from the power stage of the class-D amplifier to generate a second positive feedback signal and a second negative feedback signal with better linearity for feedback control in the class-D amplifier.

Abstract: The present invention discloses a driver circuit for an electrostatic loudspeaker, comprising: a digital modulation encoder for receiving a digital audio signal and a fixed frequency pulse signal, and mixing them by modulation; a digital to analog converter for converting the output of the digital modulation encoder to an analog signal; a transformer for adjusting the voltage amplitude of the analog signal; and a demodulator for demodulating the adjusted analog signal to driver a speaker.

Abstract: A sigma-delta class-D amplifier includes a quantizer to quantize an input to produce a digital signal, and an output stage to produce an output according to the digital signal. The quantizer has a smaller step size so that the digital signal has at least five logical levels, and the sigma-delta class-D amplifier is thus improved to have wider stable modulation range and less switching loss.

Abstract: An electrostatic loudspeaker driver includes a class-D amplifier and a demodulator circuit. The class-D amplifier is operated with a PWM signal, creating an amplified digital signal according to an input signal. A low-pass filter in the demodulator circuit filters out the PWM carrier frequency in the digital signal and retrieves an audio signal therefrom. The efficiency is improved significantly and heat sink is no longer needed.

Abstract: In an adaptive leading-edge blanking circuit and method for a switching mode power converter, an inductor current of the converter is sensed and compared with a threshold to decide an end point of a leading-edge blanking time. Circuit and method are further provided for preventing the converter from entering pulse skipping mode, which employs a current trimming circuit in an oscillator for a PWM controller in the converter to reduce a charging current in the oscillator if the output voltage of the converter is excessively high, to thereby reduce the oscillator frequency and in turn lower the switching frequency of a high-side power switch of the converter.