RU146932U1 - DIGITAL ANALOG CONVERTER - Google Patents

Abstract

1. A digital-to-analog converter containing an n-bit register, characterized in that it contains an additional n-bit register, the corresponding outputs of the control unit are connected to the inputs of the registers, and n-bit resistor R-2R matrices, one pair of resistor outputs are connected to the outputs of the registers matrices through resistors with a resistance of 2 · R Ohm is connected to ground, and another pair of matrix outputs is connected to the transformer inputs, the input of the control unit is the input of the digital-to-analog converter, and its output is the output transformatora.2. A digital-to-analog converter according to claim 1, characterized in that the transformer is configured to change the transformation coefficient. 3. The digital-to-analog converter according to claim 1, characterized in that the n-bit R-2R matrix contains n parallel resistors with a resistance of 2 · R Ohms, which are interconnected by n-1 resistors with a resistance of R Ohms and through a resistor with a resistance of 2 · R Ohms connected to ground. 4. The digital-to-analog converter according to claim 3, characterized in that the keys are connected to the inputs of the R-2R matrix, one input of which is connected to ground, and the other to a voltage source.

Description

The utility model relates to digital-to-analog converters and can be used in devices for converting a digital code into an analog electric quantity, as well as in volume controls of a digital sound code [H03M 1/66].

Various types of digital-to-analog converters (DACs) are known [1], built both on resistive arrays of various types and on the basis of frequency to voltage conversion.

The disadvantages of the known DACs include the technological complexity and high cost of manufacturing precision resistive arrays, and the second type of DACs is the lack of accuracy and linearity of the conversion characteristics. It is known that precision resistive matrices can only be manufactured using thin-film technology, including functional fitting of resistors, rather than semiconductor, which determines these disadvantages.

The closest in technical essence is the DIGITAL ANALOG CONVERTER (RF patent No. 2275740), containing, a register, the inputs of which are inputs of the DAC, and an operational amplifier, the output of which is the output of the DAC. The outputs of the register are connected to the inputs of the block of pulse amplifiers, the outputs of which are connected to the inputs of the matrix of LEDs, which is optically connected to a photodetector connected to the operational amplifier.

The disadvantages of the described device are: low speed due to the use of pulse amplifiers, as well as significant weight and size indicators due to the use of a matrix of LEDs, which in addition accounts for the main power consumption.

The purpose of the utility model is to improve the performance of a digital-to-analog converter.

The technical result consists in increasing the speed and accuracy of the conversion of the DAC.

The technical result is achieved due to the fact that the prototype containing n bit register is different in that it contains an additional n bit register, the corresponding outputs of the control unit are connected to the inputs of the registers, and n bit resistor R-2R matrices, one pair of resistor outputs are connected to the outputs of the registers matrices through resistors with a resistance of 2 · R Ohm is connected to ground, and another pair of matrix outputs is connected to the transformer inputs, the input of the control unit is the input of a digital-to-analog converter, and its output is the output transformer.

In particular, the transformer is configured to change the transformation ratio.

In particular, the n-bit R-2R matrix contains n parallel resistors with a resistance of 2 · R Ohms, which are interconnected by n-1 resistors with a resistance of R Ohms and are connected to ground through a resistor with a resistance of 2 · R Ohms.

In particular, keys are connected to the inputs of the R-2R matrix, one input of which is connected to ground, and the other to a voltage source.

Brief Description of the Drawings

In FIG. 1 is a block diagram of a digital-to-analog converter.

In FIG. 2 is a schematic representation of a parallel four-bit DAC.

In FIG. 3 presents diagrams explaining the principle of operation of the device.

Utility Model Implementation

The digital-to-analog converter contains a control unit 1, which is connected to n bit register 2 and n bit register 3. The outputs of registers 2 and 3 are respectively connected to the inputs of n bit resistor matrices 4 and 5. One pair of outputs of resistor R-2R matrices 4 and 5 through resistors 6 and 7 are connected to ground 8, another pair of outputs of matrices 4 and 5 is connected to transformer 9.

The four-digit digital-to-analog converter (Fig. 2) contains a resistor matrix 10 with 4 parallel resistors, the resistance of which is 2 · R Ohm, which are interconnected by 3 resistances with a nominal value of R Ohm. Keys 11-14 are connected to parallel resistors. A power source is connected to one input of keys 11-14, and ground 15 is connected to another input. Key 11 corresponds to the least significant digit of the digital code. A resistor 16 is connected to the output of the parallel resistor corresponding to the least significant digit of the digital code, the output of which is connected to ground 15. An output voltage terminal is connected to the output of the parallel resistor corresponding to the highest digit of the digital code.

The resistance of the resistors 6, 7 and 16 is 2 · R Ohms.

The control unit 1 implements the alternate connection of the input digital code to register 2 or 3. Depending on the sign of the converted digital code. If the high-order bit of the digital code is “1”, then control unit 1 supplies a digital code to the corresponding inputs of register 2, and if the high-order bit “0”, then the control unit 1 supplies a digital code to the corresponding inputs of register 3. Thus, the polarity of the analog signal is realized at the output of the transformer 9. Logical “0” of the high bit of the converted digital code corresponds to a positive polarity at the output of the transformer 9, logical “1” of the high bit corresponds to the negative polarity of the signal at the output of the transformer 9.

The output signal is generated in the transformer 9, which implements the function of the adder, and thereby ensures the restoration of the original digital signal, and also provides galvanic isolation between the converter and the consumer.

Changing the transformation coefficient of the transformer 9 allows you to change the level of the output signal.

Digital-to-analog Converter operates as follows.

The converted digital code is fed to the input of the control unit 1.

In the period from T1 to T2 (Fig. 3), the control unit 1 sends a digital code to the corresponding bits of register 3. The voltage at point “a” is illustrated in diagram 2 in FIG. 3. At the outputs of register 3 at this moment, the voltage is zero. Current flows through the output transformer 9 from point “a” to point “b”, forming a positive half-wave of the output voltage on the secondary winding of transformer 9.

In the period from T2 to T3, the control unit 1 sends a digital code to the corresponding inputs of register 2. The voltage at point “b” corresponds to diagram 3 on the graph. The voltage at the outputs of register 2 at a given time is zero. The current through the output transformer flows in the direction from point "b" to point "a", forming a negative half-wave of the output voltage on the secondary winding of the output transformer 9.

As a result of the alternate operation of the register 2 and 3 and two matrices 4 and 5, a full-fledged alternating output voltage of the converter is formed on the secondary winding of the output transformer 9 - diagram 1 in FIG. 3.

We will demonstrate the calculation of the output voltage values by the example of the operation of a similar four-digit DAC (Fig. 2).

If the keys 11-14 are in the "0" position, then the output voltage will be zero.

If the key 11 of the least significant digit of the digital code is set to position "1", and all the others to position "0", then

U _o = V * 1/16.

If the key 12 of the first category is set to position "1", and all the others to position "0", then

U _o = V * 1/8.

If the keys 11 and 12 are set to position "1", and all the rest to position "0", then

U _out = V * (1/16 + 1/8).

In the general case, we get:

U _o = V * (A ₀ * 1/16 + A ₁ * 1/8 + A ₂ * 1/4 + A ₃ * 1/2),

where A _i = 1 if the corresponding key (K _i ) is in position "1" and A _i = 0 if the corresponding key is in position "0".

That is, by closing the keys K ₀ ... K _{3 in} various ways, that is, by applying a four-bit code A ₃ A ₂ A ₁ A ₀ to the input, you can get 2 ⁴ = 16 different values of the output voltage (from U _o = 0 to U _o = V * (1-1 / 16) with a step Δ = V * 1/16).

Thus, this circuit is the simplest parallel four-bit digital-to-analog converter.

Similarly, you can build eight, ten, twelve and n-bit DACs.

In the general case, for an n-bit DAC, we will have:

U _o = V * ∑ (A _i * 1/2 ⁿⁱ ),

where i is the discharge number (i = 0, 1, 2 ... n-1), A _i = 1, if the corresponding key is closed on the power bus and A _i = 0, if the corresponding key is closed on the common wire.

The step is determined by the formula: Δ = V / 2 ⁿ , where n is the total number of bits.

The considered digital-to-analog converter (Fig. 1) can be implemented on a microcontroller with a sufficient number of unused legs.

In the classical R-2R matrix, when converting an alternating sound signal, it is necessary to form a virtual "0", that is, put the matrix in the average value of the output voltage equal to half the supply voltage, which corresponds to "0" in the sound signal.

This drawback requires the use of an isolation capacitor at the output of the resistor matrix to suppress the DC component. Also, in the classic embodiment of the implementation of the resistor matrix, the logic is different when forming a positive and negative half-cycle, for the maximum level of a positive half-period, all digits must be set to "1", and for the maximum level of a negative half-cycle - to "0".

In the proposed DAC, in the absence of an audio signal, both matrices are in the full zero position and, accordingly, the logic of half-cycle formation by the resistor matrices 4 and 5 is the same.

The positive effects of using CAM include the following:

- increase conversion speed, limited by the switching speed of the control unit 1; it is implemented by reducing the number of components of the electrical circuit;

- improving the accuracy of the conversion due to the linearization of the characteristics of the Converter, which is achieved due to the fact that the used resistor matrix does not form a virtual zero and thereby rectifies the characteristic in the region of the zero position.

As positive effects, we can distinguish a reduction in the cost of the converter due to the fact that it is possible to use resistors with less accuracy.

Information sources:

1. Fedorkov B.G., Taurus V.A. DAC and ADC chips: operation, parameters, application. - M .: Energoatomizdat, 1990 .-- 320 p.

Claims (4)

1. A digital-to-analog converter containing an n-bit register, characterized in that it contains an additional n-bit register, the corresponding outputs of the control unit are connected to the inputs of the registers, and n-bit resistor R-2R matrices, one pair of resistor outputs are connected to the outputs of the registers matrices through resistors with a resistance of 2 · R Ohm is connected to ground, and another pair of matrix outputs is connected to the transformer inputs, the input of the control unit is the input of the digital-to-analog converter, and its output is the output transformer. 2. The digital-to-analog converter according to claim 1, characterized in that the transformer is configured to change the transformation ratio. 3. The digital-to-analog converter according to claim 1, characterized in that the n-bit R-2R matrix contains n parallel resistors with a resistance of 2 · R Ohms, which are interconnected by n-1 resistors with a resistance of R Ohms and through a resistor with a resistance of 2 · R ohm connected to ground. 4. The digital-analog converter according to claim 3, characterized in that the keys are connected to the inputs of the R-2R matrix, one input of which is connected to ground, and the other to a voltage source.

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