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 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 amplifier includes an input amplifier, a comparator, a switching circuit, an output filter and a feedback filter. The input amplifier receives an input signal of the power amplifier at a positive input of the input amplifier and an output signal of the feedback filter at a negative input of the input amplifier. The input amplifier has a capacitive feedback from an output of the input amplifier to the negative input of the input amplifier. The comparator receives the output signal of the input amplifier at a positive input of the comparator and the output signal of the feedback filter at a negative input of the comparator. The comparator provides a control signal based on a comparison between signal levels of the signals at the positive and the negative inputs of the comparator.

Abstract: A power amplifier includes an input amplifier, a comparator, a switching circuit, an output filter and a feedback filter. The input amplifier receives an input signal of the power amplifier at a positive input of the input amplifier and an output signal of the feedback filter at a negative input of the input amplifier. The input amplifier has a capacitive feedback from an output of the input amplifier to the negative input of the input amplifier. The comparator receives the output signal of the input amplifier at a positive input of the comparator and the output signal of the feedback filter at a negative input of the comparator. The comparator provides a control signal based on a comparison between signal levels of the signals at the positive and the negative inputs of the comparator.

Abstract: A power amplifier for amplifying an electric input signal in an operational frequency range and providing an output signal, comprising switching means (22), filter means (14, 15) for generating a power output signal by low pass filtering a block wave signal, input means for receiving the electric signal and feeding it to a first input of the switching means, the power amplifier further comprising a feedback circuit (24) connecting the output signal to the first input of the switching means. The power amplifier comprises a servo amplifier (32) connected to receive an error signal appearing at the first input of the switching means and to feed a correction output signal to a second input of the switching means (22) for neutralizing an impact of the error signal on the output signal. The invention relates to a method of amplifying an electric input signal in an operational frequency range.

Abstract: A method and apparatus for automatic gain control of an amplifier in which the method and apparatus detects excessive increase in the sound volume or temperature rise in the audio system and reduces the gain of the amplifier by various means. Each gain control circuit has a comparator to compare a signal with threshold values and an integrator to integrate output signals of the comparator with respect to a predetermined time length to reduce a gain of the amplifier. The method and apparatus conducts dynamic suppressing of excess signals and thereby controlling output level of the amplifier at multiple stages without immediately shutting down the audio system. In the case where the sound volume increases to a degree that may damage the amplifier or speaker, a shutdown signal is generated to shutdown the operation of the whole system.

Abstract: A method and apparatus for automatic gain control of an amplifier in which the method and apparatus detects excessive increase in the sound volume or temperature rise in the audio system and reduces the gain of the amplifier by various means. Each gain control circuit has a comparator to compare a signal with threshold values and an integrator to integrate output signals of the comparator with respect to a predetermined time length to reduce a gain of the amplifier. The method and apparatus conducts dynamic suppressing of excess signals and thereby controlling output level of the amplifier at multiple stages without immediately shutting down the audio system. In the case where the sound volume increases to a degree that may damage the amplifier or speaker, a shutdown signal is generated to shutdown the operation of the whole system.

Abstract: Power amplifier for amplifying an electric input signal in an operational frequency range and providing an output signal, comprising switching means (12) for generating a block wave signal by alternately switching the block wave signal to a first supply voltage or a second supply voltage, input means for receiving the electric signal and driving the switching means, wherein the input means comprises an integrator circuit (10) integrating an error signal formed by a difference between the output signal and the electric input signal and providing an integrator gain in the operational frequency range, the power amplifier further comprising a local feedback circuit (18), and a global feedback circuit (20), an output of the integrator circuit being connected the input of the switching mean A limiter circuit (22) is connected to receive the electric input signal and an output signal of the integrator circuit and connected to the integrator circuit for limiting the gain of the integrator circuit when detecting a dif

Abstract: A power amplifier for amplifying an electric input signal in an operational frequency range and providing an output signal, comprising switching means (22), filter means (14, 15) for generating a power output signal by low pass filtering a block wave signal, input means for receiving the electric signal and feeding it to a first input of the switching means, the power amplifier further comprising a feedback circuit (24) connecting the output signal to the first input of the switching means. The power amplifier comprises a servo amplifier (32) connected to receive an error signal appearing at the first input of the switching means and to feed a correction output signal to a second input of the switching means (22) for neutralizing an impact of the error signal on the output signal. The invention relates to a method of amplifying an electric input signal in an operational frequency range.

Abstract: A control circuitry for controlling operation of switches of a non-regulated DC-to-DC converter is disclosed. The converter comprises a transformer having a primary winding, which is arranged to be excited by means of electricity provided through the switches, and an output connected to at least one secondary winding of the transformer via a rectifier circuitry and suitable to provide an output voltage to a load circuitry. The control circuitry comprises measuring means arranged to determine a load caused by any load circuitry; and adjustment means arranged to adjust a switching frequency for operating the switches in response to the determined load such that the switching frequency is decreased for an increased load and vice versa. A non-regulated DC-to-DC converter, a method for controlling operation of switches, and a computer program are also disclosed.

Abstract: A method and apparatus for supporting a purchase of content over a public communication network from a content provider (404) to a customer (400) using an access operator for communication. The content provider receives a purchase request for content from the customer over the public network (102). The requested purchase is validated by a transaction router (406) which identifies the access operator and checks whether the operator approves the requested purchase. The content provider then delivers content to the customer if the purchase has been validated. Finally, the customer can be charged for the purchase by the access operator. The transaction router acts as a common payment mediator between plural operators and content providers, such that only one trusted relationship needs to be established with the transaction router for each operator and each content provider, respectively.

Abstract: To eliminate overshoots of an output voltage from a DC/DC voltage converter (1) during start-up of the converter as well as during recovery after a short-circuit of a first and a second output terminal (5,5′) of the converter, a circuit (R2, R3, R4, C1, D2) is provided for generating, during a predetermined interval, a signal that is proportional to the rate of increase of the output voltage of the converter (1) to be supplied to the input of an error amplifier (4) to be superimposed on an error signal corresponding to a difference between an actual value and a set desired value of the output voltage of the converter (1), supplied to a control circuit (3) controlling the converter (1).