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: This invention relates to the mechanical protection using digital processing and a predictive estimation of instantaneous displacement of the voice coil in a loudspeaker transducer. The invention solves the problem of limiting the coil displacement of the transducer by applying a look-a-head based linear or non-linear predictor and a controller operating directly on the displacement signal in order to finally convert back into the incoming signal domain.

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: Electro dynamic transducers can fail due to either excessive voice coil excursion, causing mechanical clipping, or by overheating of the voice coil causing degradation of the materials. The disclosed invention relates to protection against excess voice coil temperature in such transducers. The current through the transducer voice coil and the voltage across its terminals, are measured. The resistive part of the impedance of the transducer is then estimated based on the measurements of current and voltage. When the resistive impedance for the given type of transducer is well known at one temperature it is then possible to calculate the temperature when the resistive impedance changes. The estimated voice coil temperature is then fed to a signal attenuator or controller, which attenuates the output signal to the transducer.

Abstract: The invention relates to a pop reduction system for a switching power conversion system (0, 1), which system comprises an analogue control system (0) and a switching power stage (1), where the pop reduction system comprises an extra power stage (2), controllable means (3) for establishing or eliminating an extra signal path from the output of said control system (0) via said extra power stage (2) to the output terminal of said switching power conversion system (0, 1} and control means (34) for controlling said controllable means (3), whereby establishing or elimination of said extra signal path is attained. The invention furthermore relates to a corresponding method for pop reduction and generally to amplifier systems comprising the pop reduction system according to the invention.

Abstract: In one embodiment of the present invention, an electro-dynamic transducer is disclosed including a diaphragm, a first suspension suspending the diaphragm, a coil former attached to the diaphragm, the coil former having a first, inner portion, and a second, outer portion, arranged coaxially in relation to each other, a coil arranged around the outer coil former portion, a magnetic system, operable to magnetically cooperate with the coil, and a second suspension mounted between the inner coil former portion and the magnetic system. The new and improved way of placing the second suspension allows for a slim form factor, while stabilizing the system more than prior art designs. The transducer according to one embodiment of the present invention is less sensitive to rocking modes, and the gap in the magnet system can thus be made smaller.

Abstract: An audio power conversion system includes a power supply having a positive supply rail and a negative supply rail for supplying power to a single ended class D amplifier. The system further includes a supply pump reduction circuit connected to the supply rails and adapted to redistribute a pumping charge from said power supply by forcing a current-flow from a rail with a higher voltage to a rail with a lower voltage. According to the at least one embodiment of the invention, the redistribution circuit is arranges to always distribute charge from the rail with the higher voltage. Thus, for practical circuits, the pump canceling occurs continuously and is not confined to every other cycle.

Abstract: A Hybrid feedback Controlled Oscillation Modulator (HCOM) is disclosed, having a 1st feedback path from the output voltage of the switching stage and a second feedback path from the filter output, the two feedback paths being superposed to provide a weighted state feedback signal. The state feedback path signal is subtracted from the input signal to form an error signal, the error signal filtered by a forward path compensation block B(s), closing the loop by feeding the pulse modulator, the loop having a transfer function such that self-oscillation can be established in the closed loop system. In an example embodiment, the first feedback path has a low pass characteristic and the second feedback path lead characteristic, the first feedback path being weighted by a weighting factor ?. Further embodiments include a pure passive realization without a forward path device and the application of 3rd feedback loops to enhance global amplifier performance.

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: The present invention relates to a method for correcting for a source of non-linearity and noise introduced in a switching power amplification stage during power amplification of a pulse-modulated reference signal from a pulse modulator, where the method comprises the following steps: —providing an output stage embedded in an analogue self-oscillating control loop able to receive a pulse-referenced input signal; —generating a feedback signal from the switching power amplification stage or after a demodulation filter; —deriving an error signal by comparing the feedback signal with the reference signal; —filtering the error signal by a low pass filter for reducing the higher harmonics of the carrier; —adding a compensator for generating high loop gain in the audio band; —feeding the compensator output to a zero cross detector or comparator, thus providing a carrier for re-modulation or re-timing by feeding the filtered signal to a zero cross detector or comparator, which controls the output stage.

Abstract: A pulse width modulator (10) for converting a digital signal into a PWM signal, comprising a plurality of integrators (11) with integrator gains (12) arranged in series, a comparator (17) for comparing the output of the last integrator (11?) with a reference, and thereby creating the PWM signal. The modulator further has means (13) for realizing self-oscillation at a desired switching frequency, and a feedback path (14) connected to a point down stream said comparator and leading to a plurality of summing points, each preceding one of said integrators, wherein the PWM signal is quantized in time by the clock frequency of the modulator, and wherein the integrator gains (12) are adapted to reduce any quantization noise.

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: A power conversion system comprising at least one Pulse Modulated Amplifier (1), including a pulse modulator for generating a pulse modulated signal based on a reference input (vi), a switching power stage arranged to amplify the pulse modulated signal, and a control system arranged to compensate for power supply voltage variations, and a voltage supply (2) providing drive voltage (Vs) to each amplifier, wherein said voltage supply (2) is provided with said input reference (vi), and arranged to provide a first drive voltage component (Vs) tracking an amplified absolute value of the input reference (vi). Pulse area modulation according to the invention will result in improved efficiency and at the same time ensure lower levels of EMI, as the mean amplitude of the PAM signal is lowered.

Abstract: A pulse modulation power converter comprising a forward path including a forward block (15), a switching stage (11) for amplifying an output from the forward block, and an output filter (12) for low pass filtering an output signal from the switching stage, a global feedback path (13), connected to the low pass filtered output signal, comprising a global feedback block (18, 19) for generating a feedback signal, and means (14) for subtracting said feedback signal from an input signal, and feeding the result to said forward path. The global feedback block and/or forward block includes means for compensating at least a portion of a phase lag of said output filter, and means for obtaining a 180 degrees phase lag at a switching frequency, thereby achieving conditions for a controlled oscillation at said switching frequency. The control system combines the advantages of the self-oscillation technology with a high gain, wide-band control loop for suppressing non-linearities.

Abstract: A synchronized controlled oscillation modulator (SCOM), comprising at least one, Controlled Oscillation Modulator (5), and synchronizing means (1, 6) connected to said COM modulator. The modulator can comprise several COM modulators, and the synchronizing means can be arranged between the COM systems, so that the oscillation modulator signal is used as synchronization signal. The invention provides significant advantages in performance, topological simplification, improved robustness, stability and efficiency compared to prior art.

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.