JPH01292913A - Automatic control circuit for da converter - Google Patents

Abstract

PURPOSE:To prevent a meaningless large output voltage from being sent by adding an inverting voltage, for which the output voltage is inverted, to this output voltage when the gain of a DA converter is controlled and cancelling the output voltage. CONSTITUTION:An inverting amplifier 3 is provided to generate the inverting voltage, for which the polarity of the output voltage of a DA converter 1 is inverted. When the gain is controlled, this inverting voltage is added and an almost zero voltage is sent. Next, whole off-set adjustment to include the DA converter 1 and a buffer amplifier 2 is executed. Thus, when the gain is controlled and off-set of the DA converter 1 is adjusted, the meaningless over voltage is prevented from being sent to an external part.

Description

[Detailed Description of the Invention] [Summary] Regarding an automatic adjustment circuit that adjusts the output voltage of a DA converter, when adjusting the gain of the DA converter, an inverted voltage obtained by inverting the output voltage is added to this output voltage to cancel the A buffer amplifier that amplifies the power of the voltage output from the DA converter and outputs it with the purpose of not sending out the output voltage, an inverting amplifier that generates an inverted voltage by inverting the polarity of the output voltage of the DA converter, and this inverting amplifier. and a switch that supplies the output in such a manner as to add it to the input of the buffer amplifier, and closes the switch when adjusting the gain of the DA converter, and inputs predetermined data for the gain adjustment to the input of the DA converter of this factory. , adjust the gain of our DA converter so that the analog output voltage of this DA converter becomes a predetermined value, then open the switch and input predetermined data for offset adjustment to the input of the DA converter, The IDA converter is configured to perform offset adjustment so that the output voltage from the buffer amplifier becomes a predetermined value.

[Industrial application field]

The present invention relates to an automatic adjustment circuit that mvrts the output voltage of a DA converter.

[Prior Art and Problems to be Solved by the Invention] An automatic correction circuit for an analog output circuit is normally constructed as shown in FIG. This gain adjustment and offset adjustment of the analog output circuit is repeated several times. For gain adjustment, input data corresponding to the full-scale voltage is input to the DA converter (DAC) 1), and at this time, the buffer amplifier 12
The measurement circuit 15 measures the output voltage that is output from the output voltage to determine the error, and the adjustment circuit 16 supplies data corresponding to this error to the DAC (0) 17=O, and the DA converter 1 generates the gain adjustment voltage. This is done by inputting it to the DA converter 1). On the other hand, the offset g adjustment similarly converts the input data corresponding to zero voltage to the DA converter (DAC1)
At this time, the output voltage output from the buffer amplifier 12 is measured by the measurement circuit 15 to find an error, and the data corresponding to this error is sent from the adjustment circuit 16 to the D A C (1
)1? -1.

Therefore, as shown in Figure 4, when supplying the output voltage from the analog output circuit to an external device such as an exciter, D
There is a problem in that an unexpectedly excessive voltage generated during gain adjustment and offset adjustment of the A converter is supplied to an external device, such as an exciter, and gives excessive vibration to the device under test. Providing a circuit for removing this unexpected excessive voltage on the external device side has problems such as a complicated circuit configuration and an increase in the number of signal lines for this purpose.

An object of the present invention is to cancel the output voltage by adding an inverted voltage obtained by inverting the output voltage to the output voltage when adjusting the gain of the DA converter, thereby preventing sending out an unexpectedly large output voltage.

[Means to solve problems]

Means for solving the problem will be explained with reference to FIG.

In FIG. 1, a DA converter (DAC) 1 converts input data into an analog signal.

The buffer amplifier 2 amplifies the power of the output voltage output from the DA converter 1 and sends it out.

The inverting amplifier 3 generates an inverted voltage obtained by inverting the output voltage of the DA converter 1.

The switch 4 inputs the inverted voltage generated by the inverting amplifier 3 by adding it to the input of the buffer amplifier 2, or switches it to a non-input state.

[Effect]

As shown in FIG. 1, in the present invention, when adjusting the gain of the DA converter 1, even if the switch 4 is closed and predetermined data for gain adjustment is input to the input of the DA converter 1, there is no unexpected signal from the buffer amplifier 2. Adjust the gain of the DA converter 1 so that the analog output voltage of the DA converter 1 becomes a predetermined value while preventing excessive voltage from occurring. Next, open the switch 4 and connect the input of the DA converter 1 to the By inputting predetermined data of the layer, offset adjustment of the DA converter 1 is performed so that the output voltage from the buffer amplifier 2 becomes a predetermined value.

Therefore, it is possible to prevent unexpected excessive voltage from being sent out from the output of the buffer amplifier 2 when adjusting the gain of the DA converter 1.

〔Example〕

Next 1. The configuration and operation of one embodiment of the present invention will be explained in detail using FIG. 1 and FIG. 2.

In FIG. 1, a DA converter (DAC) 1 converts digital input data into an analog voltage. This DA converter 1 has terminals for gain adjustment and off-cellar) 1! It has a terminal for maintenance.

The buffer amplifier 2 is composed of an AMP (operational amplifier) 2 and high precision resistors R, R1. By using resistors R+ and Rg with highly accurate values, the gain of the buffer amplifier 2 is set in advance with high accuracy.

The inverting amplifier 3 generates an inverted voltage obtained by inverting the output voltage of the I)A converter 1. DA converter 1
When adjusting the gain of the AM, switch 4 is closed, and this inverted voltage is applied to the AM that constitutes the buffer amplifier 2 via the resistor R1.
The inflow current I applied to the negative terminal of P2 and the current 13 flowing from the DA converter 1 to the negative terminal of AMP2 cancel and become almost zero current,
No output voltage is generated at the output terminal of P2, and it is maintained at approximately zero voltage. This prevents unexpected excessive voltage from being supplied to external equipment connected to the external output when adjusting the gain of the DA converter l.

The switch 4 inputs the current flowing due to the inverted voltage generated by the inverting amplifier 3 to the input of the buffer amplifier 2 in such a manner that it is added to the input, or switches to a non-input state. This switch 4 is constituted by an analog switch.

The measuring circuit 5 precisely measures the output voltage output from the DA converter 1 or the buffer amplifier 2, and is a comparator.

In response to the notification from the measurement circuit 5, the adjustment circuit 6 adjusts the DA
C (digital to analog converter) (0)? -0
Alternatively, digital data is notified to the DAC (1) 7-1, and a predetermined analog voltage for gain adjustment or voltage for offset adjustment is input to the DA converter 1. Thereby, the gain adjustment and offset adjustment of the DA converter 1 and the inverter 1 are automatically performed. This adjustment circuit 6 is constituted by a microprocessor or the like.

Next, the operation of the configuration shown in FIG. 1 will be explained in detail using the flowchart shown in FIG.

In FIG. 2, ■ closes the switch 4.

This means that when the switch 4 in Fig. F is closed and the inverted voltage output from the inverting amplifier 3 is input to the input terminal of the buffer amplifier 2, even if input data corresponding to full scale is input to the DA converter 1, This means that the voltage output from the buffer amplifier 2 is set so that it is always maintained at approximately zero voltage.

(2) Performs offset adjustment. This means that in response to inputting the input data corresponding to zero voltage to the DA converter 1, the output voltage output from the DA converter 1 is input to the measuring circuit 5. , the adjustment circuit 6 that has received the notification of the error signal adjusts the DAC (
1) Input an analog voltage for offset adjustment to the DA converter 1 via 7-1. This allows you to give feedback a! I! Offset adjustment is automatically performed with I.

■ performs gain adjustment. Similar to offset adjustment, this means that in response to input data corresponding to a full-scale voltage being input to the DA converter 1, the output voltage ■ output from this DA converter 1 is adjusted. The analog voltage for gain adjustment is input to the measurement circuit 5, and the adjustment circuit 6, which has received notification of the error signal, inputs the analog voltage for gain adjustment to the DA converter 1 via the DAC(0) 7-0 in a so-called feedback mode.

Thereby, gain adjustment is automatically performed in a feedback manner.

(2) Repeats the offset adjustment (2) and the gain adjustment (2) multiple times, and determines whether the error has become less than a predetermined value. If OK, execute ■. NO
In this case, repeat ■ and ■.

(2) Open switch 4. This is because by repeating steps ① and ②, the offset adjustment and gain adjustment of the DA converter 1 itself have been performed with sufficient precision. In this case, switch 4 is opened. In addition, the gain of buffer amplifier 1 is
Since high-precision ones are used as + and Rz, they are precisely set in advance.

■ performs offset adjustment. This is done by inputting the output voltage ■ output from the buffer amplifier 2 to the measuring circuit 5 in response to inputting the manual data corresponding to zero voltage to the DA converter 1, and The adjustment circuit 6 that has received the error signal adjusts the DAC (1) 7 in a so-called feedback mode.
An analog voltage for offset adjustment is input to the DA converter 1 via -1. As a result, the entire offset m including the DA converter 1 and the buffer amplifier 2 is automatically adjusted in a feedbank manner.

As described above, with switch 4 closed, buffer amplifier 2
Adjust the gain of the DA converter 1 under the condition that almost zero potential is always output from the DA converter 1, and then open the switch 4 to adjust the overall offset including the DA converter 1 and the buffer 2. This makes it possible to avoid outputting an unexpectedly excessive voltage to the outside during gain adjustment.

〔Effect of the invention〕

As explained above, according to the present invention, the inverting amplifier 3 that generates an inverted voltage by inverting the polarity of the output voltage of the DA converter 1 is provided, and when adjusting the gain, this inverted voltage is added to send out almost zero voltage. Then, since a configuration is adopted in which the entire offset including the DA converter 1 and buffer amplifier 2 is adjusted, the DA converter 1
It is possible to prevent unnecessary excessive voltage from being sent to the outside during gain adjustment and offset adjustment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a flowchart explaining the operation of the present invention, FIG. 3 is a diagram explaining a conventional circuit, and FIG. 4 is a diagram explaining problems in the conventional circuit. In the figure, 1 is a DA converter, 2 is a buffer amplifier, 3 is an inverting amplifier, 4 is a switch, 5 is a measurement circuit, 6 is an adjustment circuit, ? -0,7-1 are DACs (digital/analog/
converter).

Claims (1)

[Claims] In an automatic adjustment circuit that adjusts the output voltage of a DA converter, the buffer amplifier (2) power-amplifies and outputs the voltage output from the DA converter (1), and the output of the DA converter (1). An inverting amplifier (3) generates an inverted voltage with the polarity of the voltage reversed, and the output of this inverting amplifier (3) is connected to the buffer amplifier (
2), and a switch (4) that supplies the signal in a manner that it is added to the input of the DA converter (1).
Close the DA converter (1) and input the predetermined data for gain adjustment to the input of the DA converter (1).
1) so that the analog output voltage becomes a predetermined value.
Adjust the gain of the converter (1), then turn the switch (
4), and input predetermined data for offset adjustment into the input of the DA converter (1), so that the output voltage from the buffer amplifier (2) becomes the predetermined value.
An automatic adjustment circuit for a DA converter, characterized in that it is configured to perform offset adjustment of a converter (1).