| Patent application number | Description | Published |
|---|
| 20090041266 | Electrostatic loudspeaker driver - 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. | 02-12-2009 |
| 20090080676 | Driver circuit and driving method for electrostatic loudspeaker - 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. | 03-26-2009 |
| 20090174472 | Apparatus and method for improving the feedback linearity of a 1.5-bit sigma-delta class-D amplifier - A conversion circuit is provided for a 1.5-bit Σ-Δ 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. | 07-09-2009 |
| 20100079208 | Minimum pulse generation in a class-D amplifier - For minimum pulse generation in a class-D amplifier, a trapezoid switching waveform shape is used to replace the tradition triangle type to generate PWM pulses. Two voltages are compared with a sawtooth wave signal to generate the trapezoid waveform signal and a constant pulse width signal. An audio input signal is compared with the trapezoid waveform signal to generate a pulse width modulation signal, and either the pulse width modulation signal or the constant pulse width signal is used for driving a load at an output of the class-D amplifier. Flexible minimum pulse width could be obtained by offsetting one of the two voltages in generation of the constant pulse width signal. | 04-01-2010 |
| 20110043283 | VARIABLE FREQUENCY CLASS-D AMPLIFIER, CONTROL METHOD THEREOF, AND RAMP GENERATOR THEREFOR - A class-D amplifier includes a ramp generator to provide a ramp signal having a frequency varying with an audio input signal, and a modulator to convert the audio input signal to a pulse width modulation signal according to the ramp signal for a driver to drive a load device. The varying frequency of the ramp signal will cause the frequency of the pulse width modulation signal unfixed and consequently improves EMI issue. | 02-24-2011 |
| Patent application number | Description | Published |
|---|
| 20080211471 | Adaptive leading-edge blanking circuit and method for switching mode power converter - 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. | 09-04-2008 |
| 20090072897 | Sigma-delta class-D amplifier and control method for a sigma-delta class-D amplifier - 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. | 03-19-2009 |
| 20090174478 | Circuit and method for generating a PWM control signal for a class-D amplifier - 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. | 07-09-2009 |
| 20090243722 | Reduction of power consumption and EMI of a switching amplifier - 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. | 10-01-2009 |
| 20100117731 | Thermal regulation of a class-D audio amplifier - A class-D audio amplifier is protected by thermal regulation which decreases the gain of the class-D audio amplifier by asserting an over-temperature signal when the temperature of the class-D audio amplifier is detected to be higher than a threshold. The output of the class-D audio amplifier is therefore reduced by the smaller gain, and the chance for the class-D audio amplifier to stop working due to overheating is greatly reduced. | 05-13-2010 |
