Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
  • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
  • H03M1/06—Continuously compensating for, or preventing, undesired influence of physical parameters
  • H03M1/0614—Continuously compensating for, or preventing, undesired influence of physical parameters of harmonic distortion
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
  • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
  • H03M1/06—Continuously compensating for, or preventing, undesired influence of physical parameters
  • H03M1/08—Continuously compensating for, or preventing, undesired influence of physical parameters of noise
  • H03M1/0863—Continuously compensating for, or preventing, undesired influence of physical parameters of noise of switching transients, e.g. glitches
  • H03M1/0881—Continuously compensating for, or preventing, undesired influence of physical parameters of noise of switching transients, e.g. glitches by forcing a gradual change from one output level to the next, e.g. soft-start
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
  • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
  • H03M1/66—Digital/analogue converters
  • H03M1/661—Improving the reconstruction of the analogue output signal beyond the resolution of the digital input signal, e.g. by interpolation, by curve-fitting, by smoothing
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
  • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
  • H03M1/66—Digital/analogue converters
  • H03M1/74—Simultaneous conversion
  • H03M1/742—Simultaneous conversion using current sources as quantisation value generators
  • H03M1/745—Simultaneous conversion using current sources as quantisation value generators with weighted currents
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
  • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
  • H03M1/66—Digital/analogue converters
  • H03M1/74—Simultaneous conversion
  • H03M1/76—Simultaneous conversion using switching tree
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
  • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
  • H03M1/66—Digital/analogue converters
  • H03M1/74—Simultaneous conversion
  • H03M1/78—Simultaneous conversion using ladder network
  • H03M1/785—Simultaneous conversion using ladder network using resistors, i.e. R-2R ladders

Definitions

• the present invention relates to a device for low-distortion conversion, in particular amplification, of signals.
• Electrical amplifiers are needed to amplify signals in terms of voltage, current or power.
• active components such as transistors or electron tubes are usually used, but also transformers can cause a gain.
• the present invention has for its object to provide a device of the type described, with the distortions can be particularly largely reduced, without the need for this negative feedback.
• this object is achieved in that the device comprises a D / AWandler with adjustable reference voltages.
• This embodiment of the invention relates to a device for the low-voltage distortion amplification of digitized analog signals, wherein the adjustment of the reference voltages of the D / A converter results in the required gain or the required level of the output voltage.
• the device has a D / A converter upstream A / D converter with adjustable reference voltages.
• the setting of the reference voltages of the A / D converter and the D / A converter results in the required gain or the required level of the output voltage.
• a device which amplifies a signal which is either analog or digitally coded, for example in the PCM code, to an arbitrarily high voltage level, ie with an arbitrarily high gain V, with little distortion and without the aid of negative feedback, is according to the above explained embodiment, for example, constructed as follows:
• An analog signal is first digitized by an A / D converter.
• the choice of the resolution (bit length) and the sampling rate (considering the Nyquist criterion) determines the quality, ie the proportion of nonlinear distortions, of the later output signal.
• An already digitally coded signal can be further processed directly.
• the signal digitized in this way or the signal already present in digital form is switched to a D / A converter. This takes over the actual function of the voltage gain.
• Integrated D / A converters are generally designed for relatively low reference voltages ( ⁇ + -20 V). However, it is possible to build discrete transducers that are also high Can generate voltages. For this purpose, only the switches must be designed accordingly. Frequently, the sampling rate and resolution are not freely selectable, but determined by the system, eg CD standard 44.1 kHz sampling frequency and 16 bit resolution. In order to minimize the non-linear distortions arising in the conversion of a digital to an analog signal, a conventional D / A converter is extended by further devices.
• the device is preferably designed so that the D / A converter can directly control a subsequent amplifier stage by appropriate design and selection of the reference voltages.
• the following amplifier stage can in this case represent the power output stage of an audio amplifier, and the D / A converter can provide the necessary control voltage or the control current directly by appropriate design.
• the device can be used for example for analog signal conditioning (amplification) in an audio amplifier. It can convert digital audio signals into analog signals, such that the power output stage can be controlled directly in an audio amplifier.
• the D / A converter further comprises:
• Each bit has a group of four switches Sl to S4, an inversely operated R-2R-R ladder network, a generator for generating clock-synchronous rising and falling voltages, and one control logic per bit, which switches S1 to S4, the control logic via the switches Sl to S4 either Uref +, Uref, URampUp or URampDown at point 207 of the resistor 2R 211 sets in such a way that the value of one bit of two consecutive clocks is evaluated
• An analog signal which is generated by a D / A converter from digital values, basically has steps with the width of the clock of the D / A converter. Such a signal additionally contains strong portions of the clock frequency and other higher frequencies. Therefore, one strives to smooth these steps as best as possible
• filters are generally used which range from simple low-pass filters to higher-order filters. Some of these are also implemented as digital filters by digital signal processors. However, filters often have undesirable properties (phase shifts, overshoots, settling times, etc.).
• an automatic analogously generated signal is produced in the D / A converter
• D / A converters are usually realized with the aid of a resistor network.
• the R-2R-R may be mentioned here.
• the branches with the 2R resistors are respectively connected to U + or U- via switches S1 and S2, corresponding to the value of the relevant bit.
• the switches are preferably realized with semiconductor switches.
• two ramp signals are generated by a generator in synchronism with the system clock (sampling clock), one rising from U to U + and one decreasing from U + to U-. Furthermore, two further switches S3 and S4 are inserted per 2R branch. Thus, one can apply to the respective 2R resistor either U + (Sl), U- (S2), a rising ramp U- to U + (S3) or a ramp from U + to U- (S4).
• the switches Sl to S4 are controlled by a control logic as follows:
• control logic activates the switches S1 to S4 of all stages of the D / A converter.
• the result is an output voltage of the D / A converter, as shown in the following Figure 5. Due to different ramp shapes, the type of "sanding" can be varied.
• a further improvement of the smoothing can be achieved as follows:
• N are the original digital values.
• D / A converters of the type described above are ideal for implementation as integrated circuits. They are also characterized by low noise of the output signal, since the current flow in the resistors 2R in the switching operations does not change abruptly and thus disturbances are avoided by current jumps.
• the device described above thus relates to one in which the ramp voltage increases or decreases linearly.
• the ramp voltage has a shape deviating from the linear shape.
• there is another means for changing the digital input values prior to output to the D / A converter such that the value for the clock T + 1 is the average between the value for the clock T + 1 and that of the clock T results.
• the invention further proposes a device in which more than two ramps for further smoothing optimization are generated in the D / A converter, which can be connected to the points (207) of the 2R resistors via corresponding additional switches.
• the digital data can be digitized music data.
• the device can be used as an D / A converter in an integrated circuit (IC).
• This solution relates to a device for reducing distortions in electrical amplifiers caused by non-linearities in the active devices, comprising:
• a unit which predistorted a digitized signal or a digital signal according to the transfer characteristic of an amplifier
• a D / A converter which generates an analog signal from the digital predistorted signal and drives the amplifier with this signal, wherein the distortion of the amplifier is compensated by the predistortion of the input signal, so that overall a low-distortion gain despite the non-linearity of the amplifier results.
• the inventively designed device can process both analog and digitized signals.
• An analog signal is digitized by an A / D converter before further processing.
• the digitized values are fed to a unit which, knowing the non-linearity of the transfer characteristic of the amplifier system to be linearized, alters these values so as to give a low-distortion output signal after later passing through the non-linear system.
• the input values must be multiplied by the inverse transfer function. This causes a digital predistortion of the signal.
• the thus pre-distorted digital signal is output to a D / A converter whose output signal in turn directly controls the amplifier stage to be linearized.
• the D / A converter With a suitable design of the D / A converter, it can fulfill any possible requirement for controlling the amplifier stage, for example by correspondingly high reference voltages + Uref and -Uref and high output voltages for the direct control of the grid of an electron tube.
• This signal is amplified by the active device, producing nonlinear distortions. Due to the fact that the signal was already predistorted by the D / A converter with the inverse transfer function, both distortions compensate each other, so that overall an undistorted signal is set at the output of the amplifier system.
• This device requires the knowledge of the non-linearity of the amplifier, which is stored as an inverse function. If the non-linear behavior changes with time and / or temperature, this device no longer works optimally.
• the device additionally has a unit for the metrological evaluation of the output signal of the amplifier, a unit for processing the data and a unit which is suitable for permanently storing the transfer characteristic or its inversion, on the other hand, to allow for changes in the individual values during operation, with each
• the device described above offers the advantage of automatically adapting changes in the transfer characteristic (adaptive behavior).
• a measuring device measures the output signal every time a new value is output by the D / A converter. Another device compares this digitized actual value with the digitized target value, i. the undistorted digital input signal.
• the invention proposes a device comprising:
• An A / D converter that converts the analog output of the amplifier into a digital signal
• the analog signal to be amplified is amplified by a non-linear amplifier.
• the output signal contains additional distortions due to the non-linearity of the amplifier system.
• This signal is digitized by the A / D converter and multiplied by an equalizer unit with the inverse transfer characteristic. At the output you get the low-distortion signal in digital form for possibly digital further processing.
• the device described above must be supplemented by further devices.
• a measuring device measures the input signal.
• Another device compares the digitized actual value that results after passing through the input signal through the amplifier system, the A / D converter and the Equalizer is set at the output of the unit, with the digital setpoint, the undistorted digital input signal.
• the device additionally has a unit for metrological evaluation of the input signal of the amplifier, a unit for processing the data and a unit which is suitable for permanently storing the transfer characteristic or its inversion, on the one hand, and changes, on the other hand the individual values during operation by the unit, wherein the input signal of the amplifier is metrologically detected by the unit and passed to the unit for processing the data, which then between the values of a target / actual
• the non-linear amplifier is a general amplifier for voltage, current or power amplification.
• the non-linear amplifier is the power output stage of an audio amplifier.
• it may also be a preamplifier stage of an audio amplifier.
• the D / A converter When using the device in an audio amplifier, the D / A converter preferably generates a signal in such a way that the analog output stage of the audio amplifier can be controlled directly.
• a device for low-distortion conversion, in particular amplification of signals according to the invention in that a D / A converter, which operates on the basis of the summation of weighted currents, the summed individual streams directly to a load gives off, which is delivered to the load a corresponding performance.
• the device preferably serves to amplify the power of digital signals.
• the provision of the individual component streams can take place via individual current sources or also through conductor networks.
• Such a device can be designed as a low-distortion power amplifier, in particular for audio application.
• Power amplifiers are usually realized with the aid of active components, such as transistors or electron tubes.
• the resulting non-linear distortions can be reduced according to the prior art by countercoupling measures.
• the inventively embodied device is capable of power amplifying digital signals, with the least possible distortion, without the use of negative feedback measures.
• a D / A converter is used, which operates on the basis of weighted currents. These can be generated either via ladder networks or through switchable weighted constant current sources.
• the ratio of the partial currents is always 1: 2: 4: 8: ....
• the desired amplifier power can be over the absolute height of Partial streams are set.
• FIG. 1 shows a block diagram of a first embodiment of a device for the low-distortion amplification of signals
• FIG. 2 shows the structure of a conventional D / A converter with an inversely operated R2R ladder network
• Figure 3 shows the structure of a D / A converter according to the invention with integrated analog smoothing
• FIG. 4 shows the mode of operation of the D / A converter of FIG. 3 for one bit
• Figure 5 shows the effect of smoothing on an input signal
• FIG. 6 shows a block diagram of a further embodiment of a device for low-distortion amplification of signals
• FIG. 7 shows a block diagram of yet another embodiment of a device for the low-distortion amplification of signals
• FIG. 8 shows a block diagram of a further embodiment of a device for the low-distortion amplification of signals
• FIG. 9 shows a block diagram of a further embodiment of a device for the low-distortion amplification of signals.
• FIG. 10 shows a circuit diagram of a device for the amplification of a digital signal.
• FIG. 1 shows the structure of a device for low-distortion voltage amplification of analog 100 or digitized 108 signals, without the need for negative feedback.
• the analog signal 100 is converted by means of the A / D converter 101 into a digital signal 109 and then converted back into an analog signal 107 of arbitrary height by means of the D / A converter 102, the gain being determined by selecting the suitable reference voltages 102 and 103 becomes.
• An optionally digitized signal is also converted by the D / A converter 102 into an analog signal of any height.
• Figure 2 shows the structure of a conventional D / A converter with an inverse R2R ladder network. According to the respective bit value, the switches Sl and S2 switch the upper resistors 2R to either Uref + or Uref-.
• FIG. 3 shows the construction of a D / A converter with integrated analog smoothing designed according to the invention.
• a ramp generator 200 generates in each case sampling synchronously an ascending 201 and a falling 202 ramp.
• two additional switches S3 203 and S4 204 are present, by means of which, depending on the bit sequence, controlled by a control logic 206, either one of the reference voltages or one of the ramps to the relevant 2R resistor 211 are placed can.
• Figure 4 shows the operation of this D / A converter for a bit.
• Figure 5 shows the effect of smoothing on an input signal.
• the dashed line shows the output voltage of a D / A converter without smoothing, the bold solid line 209, the output voltage of the inventive D / AW with smoothing and the dotted line 210, the output voltage of the inventive D / A converter with improved smoothing.
• FIG. 6 shows the structure and operation of a distortion mitigation device that results in a nonlinear amplifier system 305.
• the analog input signal 301 is digitized by means of the A / D converter 302 (303).
• An alternative digital input signal 300, as well as the digitized analog signal 303, is pre-distorted in unit 304 in consideration of the inverse transfer characteristic 306 of the non-linear amplifier system 305. Predistorted, it is converted back to an analog signal by a D / A converter 308 (309), which serves as an input to the amplifier 305.
• the amplifier amplifies the signal 309 non-linearly, resulting overall in a linear course for the output signal 310, since pre-emphasis and non-linear distortion compensate each other.
• FIG. 7 shows the construction of another device for reducing distortions arising in a nonlinear amplifier system 305.
• the construction is similar to that of FIG. 6. While in the apparatus of FIG. 6 the inverse transfer characteristic is firmly anchored in 306, it can be corrected and / or determined by the apparatus of FIG. 7, thus providing optimal low distortion under all operating conditions Operation is guaranteed.
• the output signal 310 of the amplifier system 305 is measured via the unit 311. This measured value 312, which represents the actual value, is compared with the desired value 303 by the unit 313. Based on the deviations, the relevant point of the inverse transfer characteristic 314 is corrected.
• FIG. 8 shows the structure and mode of operation of another device for reducing distortions arising in a non-linear amplifier system 321.
• the analog input signal 320 is first amplified by the non-linear amplifier 321.
• the amplified distorted signal 322 is digitized (303) by means of the A / D converter 323 and equalized in the unit 324 due to the inverse transfer characteristic 325 of the non-linear amplifier system 321.
• This undistorted digital signal 326 is converted by the D / A converter 327 into an undistorted analog signal of arbitrary voltage level, adjustable by selecting the appropriate reference voltages of the D / A converter 327.
• FIG. 9 shows the structure of a further device for reducing distortions which are in a non-linear manner Amplifier system 321 arise.
• the construction is similar to that of FIG. 8. While in the device according to FIG. 8 the inverse transfer characteristic is firmly anchored in 325, it can be corrected and / or determined in the device according to FIG. 9, whereby under all operating conditions optimal distortion-free operation is guaranteed.
• the input 330 of the amplifier system 321 is measured via the unit 330.
• This measured value 331 which represents the desired value, is compared with the actual value 326 by the unit 329. Based on the deviations, the relevant point of the inverse transfer characteristic 328 is corrected.
• FIG. 10 shows a device for the power amplification of a digital signal, carried out here by a D / A converter with weighted current sources.
• the power output stage mentioned above may also be the output stage of a video amplifier.
• Device can therefore also be used for analog signal conditioning (preamplification) in a video amplifier. This also applies to an amplifier of measurement and control technology.
• the device can generally be used for general signal amplification.
• the device can also convert digital image data (video signals) into analog signals in such a way that the power output stage in a video amplifier can be directly controlled. This also applies to digitized signals an amplifier of measurement and control technology.
• the digital signals may be digitized image data (video signals).
• the digitized data may be general digitized physical data (measurement data).
• the amplifier can be a video amplifier or an amplifier of the measurement, control and regulation technology.
• the D / A converter can also generate a signal in such a way that the analogue end or pre-stage of a video amplifier or the analogue end or pre-stage of an amplifier of the measuring and control technology can be directly controlled.
• the low distortion conversion apparatus having a D / A converter operating based on the summation of weighted currents can be used for video applications or for measurement and control technology applications, for example.

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• Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Amplifiers (AREA)
• Analogue/Digital Conversion (AREA)

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• 2007
  • 2007-12-20 CN CN200780051588A patent/CN101636912A/zh active Pending
  • 2007-12-20 US US12/519,905 patent/US7982649B2/en not_active Expired - Fee Related
  • 2007-12-20 EP EP07856144A patent/EP2111689A2/de not_active Withdrawn
  • 2007-12-20 CA CA002673537A patent/CA2673537A1/en not_active Abandoned
  • 2007-12-20 JP JP2009541761A patent/JP2010514285A/ja active Pending
  • 2007-12-20 WO PCT/DE2007/002301 patent/WO2008077387A2/de active Application Filing
  • 2007-12-20 RU RU2009128211/09A patent/RU2009128211A/ru not_active Application Discontinuation

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