Abstract: A new and improved self-oscillating amplifier system is presented, suitable for use in high fidelity audio applications. The self-oscillating amplifier system comprises a feedback path and a forward path including a pulse modulator, a switching power amplification stage and a demodulation filter. The forward path further includes a pair of parallel forward filters preceding the pulse modulators, a differentiating forward filter and an integrating forward filter. The differentiating forward filter is utilized for controlling a switching frequency of the system while the integrating forward filter is utilized for controlling the behavior of the amplifier system within an operating frequency band (e.g. audio band). The self-oscillating amplifier system exhibits improved performance in terms of open loop gain, reduced phase turn and improved robustness as compared to other previously known self-oscillating amplifier systems.

Abstract: A power conversion system comprising an amplifier input for receiving an analog input signal and an amplifier output for providing a switching output signal is disclosed. The system is applicable for use in high definition switching audio amplification. The power conversion system further comprises a clipper for clipping the analog input signal having a predefined range limited by a clipping level, a pulse modulator and a switching power stage. The system further has a feedback path to the clipper including a duty cycle measuring unit and a clip level filter which generates a clip level signal and where the clipping level of the clipper is controlled by the clip level signal. Hereby it is e.g. possible to clip an analog input signal with good precision and reliability in a switching power conversion system.

Abstract: A self-oscillating amplifier system is disclosed. The system comprises a pulse modulator, a switching power amplification stage and a demodulation filter. Moreover, the system comprises a compensator including a forward filter which is a high order filter including a second order pole pair and a second order zero pair. Hereby it is possible to decrease the phase turn at low frequencies for better stability and increasing the gain of the control loop within the desired bandwidth.

Abstract: The invention relates to a compensator device for compensating signal dependent delay variations, including dead time and reverse recovery time, causing un-linearity in a Class-D amplifier where the compensator device comprises: a first input terminal for receiving an input pulse width modulated input PWM signal comprising pulses with falling flanks corresponding to a falling level transition and rising flanks corresponding to a rising level transition; and a second input terminal configured to receive the signal provided at an output switching node of a Class-D amplifier; an output terminal for providing a compensated output signal; and controllable delay means configured to receive and delay the pulse modulated input signal, thereby providing a delayed version of the input signal to said output terminal of the compensator device.

Abstract: A switching power conversion system and a method for start-up pop minimization in an audio amplifier assembly are disclosed. The switching power conversion system comprises a forward path including a compensator, a switching power stage and a demodulation filter. The system further comprises a DC-servo and a pre-charging circuit and a sequence control unit configured for providing a start-up sequence where the compensator and DC-servo are correctly biased and a bootstrap capacitor within the switching power stage is charged before the switching power stage is started. Hereby, it is e.g. possible to minimize the audible start-up pop in audio amplifier assemblies.

Abstract: A close-down pop reduction system and a method for close-down pop reduction in an audio amplifier assembly are disclosed. The switching power conversion system comprises a forward path having a compensator and a switching power stage and a signal path from an output of a comparator in the switching power stage to a sequence control unit. The signal path includes a close-down timing circuit configured to provide a timing signal. The sequence control unit is configured to eliminate the input signal, increase the switch frequency of the close-down pop reduction system and disable the switching power stage at a moment in time within a PWM pulse of the switching power stage. Hereby, it is e.g. possible to minimize the audible pop during close-down of audio amplifier assemblies.

Abstract: A power conversion system comprising an amplifier input for receiving an analogue input signal and an amplifier output for providing a switching output signal is disclosed. The system is applicable for use in high definition switching audio amplification. The power conversion system further comprises a clipper for clipping the analogue input signal having a predefined range limited by a clipping level, a pulse modulator and a switching power stage. The system further has a feedback path to the clipper including a duty cycle measuring unit and a clip level filter which generates a clip level signal and where the clipping level of the clipper is controlled by the clip level signal. Hereby it is e.g. possible to clip an analogue input signal with good precision and reliability in a switching power conversion system.

Abstract: A power supply arrangement for a single ended class D amplifier, including a first primary winding connected in series with a first switch between the positive supply rail and ground, a second primary winding in phase with said first primary winding and connected in series with a second switch between the negative supply rail and ground, and a controller adapted to apply a control signal to said first and second switches, said control signal (Q) having ON-pulses of a predefined pulse time separated by a dead time. In use, the primary winding connected to the supply rail with the highest numerical voltage will transform the rail voltage difference to the supply rail with the lowest numerical voltage through the opposite primary winding thus reducing any voltage unbalance between the windings.

Abstract: A power converter with positive and negative supply rail outputs for feeding a single ended class D amplifier, the converter comprising a transformer arrangement, a supply pump reduction arrangement connected between the secondary windings and the positive and negative supply rail outputs, and a boost drive mode switching arrangement. A controller is adapted to control the power converter in a negate drive mode and a boost drive mode, wherein the output voltage in the boost mode is increased by means of the transformer and the boost drive mode switching arrangement. The output voltages on the positive and negative rails can be generated at two different output voltage levels without changing the duty cycle or dead time of the control signals.

Abstract: The invention relates to a current limiting method, e. g. for Class D amplifiers comprising a unique detection- and control method. The current detection circuit can be implemented as a voltage measurement where the measured voltage corresponds to the current flowing through the power-switching device. The device can be switched OFF when a set limit is reached. By forcing certain OFF time, the associated control system behaves as a self-oscillating current limiting circuit. This can be implemented locally close to the switching device and be independent of other local or global control systems.

Abstract: A half-bridge driver includes first and second power switches, connected with their respective current paths in series, a pulse generator for generating a voltage pulse waveform, arranged to drive the first power switch, a first current generator for generating a current pulse for each negative flank of the voltage pulse waveform, a second current generator for generating a current pulse for each positive flank of said voltage pulse waveform, and a differential current receiver circuit. The differential current receiver circuit is connected to the first and second current generators, and is arranged to generate an output signal equal to the difference of the currents flowing through the current generators. The output signal is arranged to drive the second power switch.

Abstract: This invention relates to an attenuation control system (9) in a switching power conversion system comprising a digital modulator (4), for generating a modulated control signal from a (digital) source signal and a switching power state (6), said attenuation control system comprising: means for digitally attenuating the modulated signal, first gain shifting means (7) for shifting a supply voltage of said power stage between a plurality of predefined voltage levels, said first gain shifting means being arranged to decrease the power stage gain when the attenuation of the modulated signal exceeds a predefined level. This invention also relates to an attenuating method in a switching power conversion system comprising a digital modulator, for generating a modulated control signal from a (digital) source signal, and a switching power stage.