WO2001011770A1

WO2001011770A1 - Dynamic compressor used as part of a signal processing circuit in audio technique, for adjustment and/or telephone system

Info

Publication number: WO2001011770A1
Application number: PCT/DE2000/002369
Authority: WO
Inventors: Klaus Wiedorn; Heinz Lange
Original assignee: Siemens Aktiengesellschaft
Priority date: 1999-08-06
Filing date: 2000-07-20
Publication date: 2001-02-15
Also published as: DE10082334D2; AU6818600A

Abstract

The invention concerns a circuit comprising a dynamic compressor wherein the alternative control signal injected in input, with low source impedance, reaches the output by following a first signal path formed by a series resistance, as long as an adjustable voltage threshold is not exceeded. The signal is routed, from input, to a second switch, via a second signal path. When the turn-on voltage required is exceeded, the switch operates such that the alternative control signals present in input are split by a splitter formed by the series resistance and another resistance and are present in output.

Description

Dynamic compressor as part of a signal processing circuit arrangement in the audio, control and / or

phone technology

The invention relates to a dynamic compressor as part of a signal processing circuitry in the audio. Control and / or telephone technology, in which there is a nonlinear or, in some cases, linear behavior between input and output voltage amplitude, which can be specified in a compressor characteristic curve, using an operational amplifier, resistance divider circuits, coupling capacitors and a controlled electronic actuator.

The state of the art includes dynamic compressor circuits that limit the output level from a defined input level threshold in order, for example, not to overdrive subsequent circuit parts. A dynamic compressor is used in connection with a digital answering machine, whereby the digital recording stream is greatly reduced by means of a data reduction algorithm. This achieves a reasonable relationship between the duration of the voice recording and the memory requirement. Since such data reduction algorithms ensure good speech intelligibility only with a relatively high input level, the dynamic compressor always keeps the modulation in the maximum possible range. Disadvantages of the known dynamic compressors are their circuitry-related space requirements and the relatively high number of electronic components.

The invention is therefore based on the object of creating a dynamic compressor circuit which, compared to the known dynamic compressor circuit, is designed to be simpler and more cost-effective, ie with fewer and less expensive components. elements and requires a smaller circuit board area and a smaller current consumption.

According to the invention, this object is achieved by the features of claim 1. Preferred embodiments are the subject of the dependent claims.

The circuit arrangement according to the invention effectively prevents overmodulation, since the capacitor connected to ground is charged very quickly and without significant delay via an amplifier which has a low output source impedance. The charging time is approx. 1 ms. Furthermore, the frequency response of the input signal is not changed when the switch is closed, the circuit according to the invention advantageously making do with a single switch. In addition, the circuit according to the invention requires only small and inexpensive ceramic SMD chip capacitors due to the high-resistance design. Furthermore, the circuit according to the invention manages with significantly fewer components and only half of the circuit board area is used in comparison with known solutions. Furthermore, the current consumption of the compressor according to the invention is smaller than that of known solutions.

Furthermore, the circuit arrangement according to the invention contains no negative feedback, which evaluates the output signal and dampens the input signal when a control threshold is exceeded. Rather, the modulation limits are known, so that the input signal is used to actuate the switch.

In addition, the switch-off time constant is set by means of two resistors, one resistor pulling the control input of the switch against the reference potential. Instead of a bipolar transistor, an N-channel field effect transistor can also be used. Any electronic actuator for the switch can also be used, which only has to meet the requirement that switching occurs when a pre-determined voltage is exceeded.

A preferred embodiment of the invention is explained in more detail below with reference to the figures.

Fig. 1 shows a known dynamic compressor; and

2 shows the dynamic compressor according to the invention.

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be going. Bipolar transistors or field effect transistors are preferably used as switches S1.

Claims

claims

1. Dynamic compressor with an input (IN) and an output (OUT), characterized in that the alternating control signal fed in at the input (IN) from a low source impedance reaches the output (OUT) via a first signal path formed by series resistance (R5), as long as one adjustable voltage threshold is not exceeded; and the signal is led from the input (IN) to a switch (Sl) via a second signal path, the switch (Sl) switching when the required switching voltage is exceeded, so that the changeover signal present at the input (IN) is transmitted via a series resistor ( R5) and another resistor (R6) formed resistor divider and are present at the output (OUT).

2. Dynamic compressor according to claim 1, characterized in that an operational amplifier (U1) is arranged in the second signal path, which amplifies the input signal (IN).

3. Dynamic compressor according to claim 2, characterized in that an inverting operational amplifier is used.

4. Dynamic compressor according to one of claims 2 or 3, characterized in that the amplification factor of the operational amplifier (U1) is freely selectable.

5. Dynamic compressor according to one of the preceding claims, characterized in that the output voltage of the amplifier (U1) via a coupling capacitor (Cl) and one Diode (D2) charges a second capacitor (C2); and a further resistance divider (R3, R4) controls the switch (Sl) as a function of the voltage of the second capacitor (C2).

6. Dynamic compressor according to claim 5, characterized in that a further diode (Dl) ensures the DC voltage discharge of the coupling capacitor (Cl).

7. Dynamic compressor according to one of the preceding claims, characterized in that small ceramic SMD chip capacitors are used.