CN103823104B - The automatic range generating positive and negative voltage measuring circuit that a kind of single supply is powered - Google Patents

Abstract

The invention relates to an automatic range positive and negative voltage measurement circuit powered by a single power supply. The circuit includes a voltage conversion network, a buffer and a single-chip microcomputer. The positive and negative voltage signals input from the outside first pass through the voltage conversion network, which divides the input signal and maps the positive and negative voltages to the positive voltage range; after the adjustment of the voltage conversion network, the input signal is adjusted to the post-stage buffer The maximum value allowed by the input range, thus maintaining the signal integrity as much as possible. The voltage signal is buffered by the buffer and then output to the subsequent stage circuit. At the same time, it is detected by the microcontroller and fed back to the voltage conversion network to adjust the output voltage of the voltage conversion network to meet the maximum input voltage of the buffer as much as possible. The detection circuit can realize the detection of positive and negative voltages under the condition of single power supply, and has the characteristics of large measuring range and high precision.

Description

A single power supply automatic range positive and negative voltage measurement circuit

technical field

The invention belongs to the technical field of electronic technology and signal detection, and in particular relates to an automatic range positive and negative voltage measurement circuit powered by a single power supply.

Background technique

As the power supply voltage in the signal processing circuit is getting lower and lower, the voltage range that the circuit can handle is also getting smaller and smaller. However, the voltage signal range in the real world is much larger, and there will be various errors and noises in the signal. The input signal of the circuit may not always be kept within the processing range of the circuit. To satisfy the variation range of the input signal, the performance requirements of the subsequent circuit will increase, the complexity of the circuit and the power consumption will increase, and correspondingly, the complexity and area of the printed circuit board will also increase.

In practical applications, the range of the input signal V _in of the circuit is first limited by the input range of the subsequent circuit. Especially when the subsequent stage circuit is powered by a single power supply, if the input signal V _in is a negative voltage, the circuit must not work normally. And due to the existence of various errors and interferences, there will be a certain deviation between the actual value and the theoretical value of the input signal V _in . When the input signal V _in exceeds the input range of the subsequent stage circuit, the latter stage circuit will not work normally, and may even destruction. Therefore, it is necessary for the post-stage circuit to adapt to and monitor the change of the input signal V _in to avoid damage to the circuit itself. To adapt to the variation range of the input signal V _in , on the one hand, the maximum variation range of the input signal V _in can be estimated, and the input range of the subsequent stage circuit can be expanded to meet the variation requirements of the input signal V _in ; on the other hand, the input signal V _In divides the voltage, thereby reducing the range of the circuit input signal. However, increasing the input range of the post-stage circuit will make the circuit more complicated. Especially when the input signal V _in is a negative voltage, the downstream circuit must also be powered by dual power supplies, which will greatly increase the complexity of the circuit. And the improvement of the input range must be accompanied by the increase of the power supply voltage, and the power consumption of the circuit will increase. If a resistor divider circuit with a fixed divider ratio is used to divide the input signal V _in , then when the input signal V _in is small, the input signal of the subsequent stage circuit will be too small, and a lot of information in the input signal will be submerged. decline.

Contents of the invention

The technical problem to be solved by the present invention is to provide an automatic range positive and negative voltage measurement circuit powered by a single power supply to detect the positive and negative voltages under the condition of single power supply.

The technical solutions adopted by the present invention to solve the above technical problems include:

An automatic range positive and negative voltage measurement circuit powered by a single power supply, comprising: a voltage conversion network, a buffer, and a single-chip microcomputer, wherein the output end of the voltage conversion network is connected to the input end of the buffer, and the output end of the buffer is connected to the single-chip microcomputer At the input end, the single-chip microcomputer outputs the control signal to the control end of the voltage conversion network; the positive and negative voltage signals input externally are adjusted to the positive voltage range through the voltage conversion network; the buffer performs a primary buffer on the signal output by the voltage conversion network and then outputs the voltage measurement The output signal of the circuit is sent to the subsequent circuit and the single-chip microcomputer respectively; the single-chip microcomputer performs logic judgment on the output signal received from the buffer, and then outputs the control signal to the voltage conversion network to adjust the output of the voltage conversion network so that the output of the voltage conversion network Voltage as close as possible to the maximum value the buffer will allow.

Preferably, the voltage conversion network includes a voltage divider circuit, a multiplexer, and a high-precision resistor, wherein the voltage divider circuit divides the external input voltage, and it includes a plurality of high-precision matching resistors connected in series with each other. One end of the series circuit composed of high-precision matching resistors receives the positive and negative voltage signals input from the outside, and the other end is grounded; and an output end is drawn between two adjacent series resistors as the output end of the voltage divider circuit; the multiplexer Each input terminal is correspondingly connected to the output terminal of the voltage divider circuit, and its control terminal receives the control signal from the single-chip microcomputer, and the output terminal of the multiplexer is connected to the input terminal of the buffer; the multiplexer selects the appropriate Voltage division ratio, which determines which output terminal of the voltage division circuit is connected; the resistance is connected between the output terminal of the multiplexer and the power supply of the automatic range positive and negative voltage measurement circuit powered by a single power supply, and the voltage division circuit and the multi-channel The selector together adjusts the externally input positive and negative voltage signals to a suitable positive voltage range.

Preferably, the buffer includes a matching transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, a current source, and an operational amplifier, wherein the first resistor and The first capacitor is connected in parallel to form the first parallel RC circuit, one end of the first parallel RC circuit is connected to a base of the matching transistor, and the other end of the first parallel RC circuit is used as the input end of the buffer; the second resistor and the second capacitor are connected in parallel Connect to form a second parallel RC circuit, one end of the second parallel RC circuit is connected to the other base of the matching transistor; the two collectors of the matching transistor are respectively connected to the two input terminals of the operational amplifier, and the two emitters of the matching transistor are common The current source is connected, and the other end of the current source is grounded; one end of the fourth resistor and the fifth resistor are respectively connected to the two collectors of the matching transistor, and the other end of the fourth resistor and the fifth resistor are jointly connected to one end of the third resistor, The other end of the third resistor is connected to the power supply of the automatic range positive and negative voltage measurement circuit powered by a single power supply; the output end of the operational amplifier is used as the output end of the buffer; and the other end of the second parallel RC circuit is connected to the output end of the operational amplifier , as the negative feedback of the buffer.

Preferably, the single-chip microcomputer adopts an integrated circuit chip, which has its own ADC module, and the input port of the ADC module of the single-chip microcomputer receives the output signal from the buffer, carries out AD conversion and logical analysis on the output signal, and then outputs the control signal to the voltage The conversion network adjusts the output of the voltage conversion network so that the output voltage of the voltage conversion network is as close as possible to the maximum value allowed by the buffer.

The automatic range positive and negative voltage measurement circuit powered by a single power supply according to the present invention has the following beneficial technical effects:

1. According to the voltage conversion network of the present invention, the range of the input voltage can be expanded, and is no longer limited to the positive voltage range, and is no longer limited to the input range of the post-stage buffer, and fully utilizes the logic function inside the single-chip microcomputer 3 to realize the range. Automatic control and conversion. In addition, since the matching transistor U2 is added at the input end of the operational amplifier U3, the input resistance of the buffer is increased, and the precision of the circuit is improved. If the subsequent stage circuit needs to further process the output signal of the circuit, the single chip microcomputer can also be combined with the signal processing circuit of the latter stage. In this way, the complexity of the circuit basically does not change, and at the same time, the accuracy of the circuit can be maintained when the input signal varies in a large range.

2. Because the resistance network at the front end of the voltage measurement circuit is all scattered components, it is more flexible to install when used on an irregularly shaped printed circuit board, and can make full use of the limited space. The integrated circuit modules used in the circuit are very small and do not take up too much area. In addition, the voltage measurement circuit uses commonly used components, which are easy to obtain and low in cost.

Description of drawings

Fig. 1 is the block diagram of the automatic range positive and negative voltage measurement circuit of single power supply according to the present invention;

Fig. 2 is the circuit schematic diagram of the automatic range positive and negative voltage measuring circuit of single power supply according to the present invention;

Fig. 3 is an equivalent circuit diagram of the voltage conversion network in the automatic range positive and negative voltage measurement circuit powered by a single power supply according to the present invention.

detailed description

The automatic range positive and negative voltage measurement circuit powered by a single power supply according to the present invention will be described in detail below with reference to the drawings and specific embodiments.

As shown in FIG. 1 , the automatic range positive and negative voltage measurement circuit powered by a single power supply according to the present invention includes a voltage conversion network 1 , a buffer 2 , and a single-chip microcomputer 3 . Wherein, the output end of the voltage conversion network 1 is connected to the input end of the buffer 2 , the output end of the buffer 2 is connected to the input end of the single-chip microcomputer 3 , and the single-chip microcomputer 3 outputs a control signal to the control end of the voltage conversion network 1 .

The externally input positive and negative voltage signal V _in is adjusted to a positive voltage range through the voltage conversion network 1 . The buffer 2 performs primary buffering on the signal output by the voltage conversion network 1 and then outputs the output signal V _out to the subsequent circuit and the single chip microcomputer 3 respectively. The single-chip microcomputer makes a logical judgment on the output signal V _out from the buffer 2, and then outputs a control signal to the voltage conversion network 1 to adjust the output of the voltage conversion network 1 so that the output voltage of the voltage conversion network 1 is as close as possible to the buffer 2. The maximum value allowed. Wherein, the maximum value allowed by the buffer 2 is determined by its power supply voltage VCC.

Fig. 2 shows the circuit working principle of the automatic range positive and negative voltage measurement circuit powered by a single power supply of the present invention. As shown in Fig. 2, the voltage conversion network includes a voltage divider circuit, a multiplexer U1, and a high-precision resistor R0. Wherein, the voltage divider circuit divides the external input voltage, which includes a plurality of high-precision matching resistors connected in series with each other, and one end of the series circuit composed of these high-precision matching resistors receives externally input positive and negative voltage signals V _in , The other end is grounded; and an output end is drawn between two adjacent series resistors as the output end of the voltage divider circuit. Each input end of the multiplexer is correspondingly connected to the output end of the voltage divider circuit, and its control end receives the control signal from the single-chip microcomputer 3 , and the output end of the multiplexer is connected to the input end of the buffer 2 . The multiplexer selects an appropriate voltage division ratio according to the control signal of the single-chip microcomputer 3, thereby determining which output terminal of the voltage division circuit is connected. Resistor R0 is connected between the output terminal of the multiplexer and the power supply VCC of the automatic range positive and negative voltage measurement circuit powered by a single power supply, and adjusts the externally input positive and negative voltage signal V _in together with the voltage divider circuit and the multiplexer to the positive voltage range. It should be noted here that the number of high-precision matching resistors included in the voltage divider circuit is determined according to the actual precision requirements of the circuit. And the number of input terminals of the multiplexer U1 must be at least equal to the number of output terminals of the voltage divider circuit.

The buffer 2 includes a matching transistor U2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, a current source I _SS , and an operation Amplifier U3.

Wherein, the first resistor R1 and the first capacitor C1 are connected in parallel to form a first parallel RC circuit, one end of the first parallel RC circuit is connected to a base of the matching transistor U2, and the other end of the first parallel RC circuit is used as the input end of the buffer ; The second resistor R2 and the second capacitor C2 are connected in parallel to form a second parallel RC circuit, and one end of the second parallel RC circuit is connected to the other base of the matching transistor U2.

The two collectors of the matching transistor U2 are respectively connected to the two input terminals of the operational amplifier U3, the two emitters of the matching transistor U2 are connected to the current source I _SS , and the other end of the current source I _SS is grounded.

One end of the fourth resistor R4 and the fifth resistor R5 are respectively connected to the two collectors of the matching transistor U2, the other end of the fourth resistor R4 and the fifth resistor R5 are jointly connected to one end of the third resistor R3, and the other end of the third resistor R3 Connect to the power supply VCC of the auto-ranging positive and negative voltage measurement circuit powered by a single power supply.

The output terminal of the operational amplifier U3 serves as the output terminal of the buffer 2 . Moreover, the other end of the second parallel RC circuit is connected to the output end of the operational amplifier U3 as the negative feedback of the buffer 2 .

Among them, the matching transistor U2, the operational amplifier U3, and the current source can be easily selected from the prior art by those skilled in the art according to the description of this specification and the actual needs of the circuit, and will not be described in detail here.

The single-chip microcomputer 3 adopts an integrated circuit chip, and it has its own ADC module. The input port of the ADC module of the single-chip microcomputer 3 receives the output signal V _out of the buffer 2, carries out AD conversion and logical analysis on the output signal V _out , and outputs the control signal For the voltage conversion network 1 , the output of the voltage conversion network 1 is adjusted so that the output voltage of the voltage conversion network 1 is as close as possible to the maximum value allowed by the buffer 2 .

When the measurement circuit is applied, the program must be programmed in the microcontroller first, including setting the initial value of the voltage division ratio of the voltage division circuit, the algorithm for logically judging the output signal of the circuit, and the conditions that the appropriate voltage division ratio should meet. After the external input signal V _in passes through the voltage conversion network, the output signal V _out of the voltage measurement circuit is output after being buffered by the buffer 2 at the first level. Wherein, the first parallel RC circuit is used to filter the output signal of the voltage conversion network, and the matching transistor U2 is used to increase the input resistance of the buffer 2 . While the output voltage V _out is output to the subsequent stage circuit, on the one hand, after being filtered by the second parallel RC circuit, it returns to the other base of the matching transistor U2 as the negative feedback of the buffer; on the other hand, it is output to the single chip microcomputer 3 for local voltage detection Negative feedback of the circuit. The output signal V _out is judged logically by the single chip microcomputer. Determine whether the current voltage division ratio is appropriate, whether it is too large or too small, through the program burned into the microcontroller in advance, and then output an appropriate control signal to the multiplexer to adjust the voltage division ratio. If after adjustment, the new output signal is still not the best voltage division ratio after the judgment of the single-chip microcomputer, then the single-chip microcomputer outputs a new control signal to the multiplexer again, and adjusts the voltage division ratio again. This loops until the output signal meets the pre-set conditions in the program. This condition ensures that the voltage conversion circuit 1 always has an optimal voltage division ratio that matches the input signal and satisfies the input range of the buffer.

The voltage conversion network in Figure 2 can be equivalent to the circuit shown in Figure 3 . Among them, R _0a and R _0b are the equivalent voltage dividing circuits of the voltage dividing circuit R01-R0N in Figure 2 after the voltage dividing ratio is determined, and R _m is the equivalent on-resistance of the multiplexer U1, according to the superposition theorem , the voltage transfer relationship of the voltage conversion network is as follows:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; CC</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, V ₀ represents the output of the voltage conversion network, V _in represents the input of the voltage conversion network, and V _CC represents the power supply of the automatic range positive and negative voltage measurement circuit powered by a single power supply.

According to the above relationship, the input positive and negative voltages can be converted into positive voltages, so that the subsequent single-power supply circuits are capable of processing signals whose variation range reaches negative voltages.

In the measuring circuit according to the present invention, the resistance and capacitance values of the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the first capacitor C1 and the second capacitor C2 should be Meet the following requirements:

C1=C2, R1=R2, R3=R4=R5.

Wherein, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 are preferably matched resistors.

The resistance values of the first resistor R1 and the second resistor R2 and the capacitance values of the first capacitor C1 and the second capacitor C2 are determined according to actual filtering requirements.

The resistance values of resistor R0 and resistor R01-R0N should be determined according to the approximate range of the input signal and the requirements of formula (1). On the other hand, the size of N should be determined according to the accuracy requirements of the circuit. In addition, high-precision matching resistors should be used to improve accuracy.

Circuit making points:

It is required that the performance of the selected electronic components is intact, and the first capacitor C1 and the second capacitor C2, the first resistor R1, the second resistor R2, the fourth resistor R4, and the fifth resistor R5 are installed as close as possible to the matching transistor U2. According to the connection relationship of the components in Figure 2, the reliable connection is made, and the circuit can output normally.

Those skilled in the art can understand that the content that is not specified in this specification can be easily realized by those skilled in the art according to the description of this specification and in combination with the existing technology, and thus will not be described in detail.

The above descriptions are only preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention are all Should be covered within the protection scope of the present invention.

Claims (3)

1. an automatic range positive and negative voltage measuring circuit of a single power supply, is characterized in that, comprises: voltage conversion network (1), buffer (2) and single-chip microcomputer (3), wherein, The output end of the voltage conversion network (1) is connected to the input end of the buffer (2), the output end of the buffer (2) is connected to the input end of the single-chip microcomputer (3), and the single-chip microcomputer (3) ) outputting a control signal to the control terminal of the voltage conversion network (1); The externally input positive and negative voltage signals (V _in ) are adjusted to a positive voltage range through the voltage conversion network (1); the buffer (2) performs primary buffering on the signal output by the voltage conversion network (1) and then outputs The signal (V _out ) is given to the rear stage circuit and the single-chip microcomputer (3) respectively; the single-chip microcomputer (3) carries out logical judgment on the output signal (V _out ) received from the buffer (2), and then outputs the control signal For the voltage conversion network (1), adjust the output of the voltage conversion network (1), so that the output voltage of the voltage conversion network (1) is as close as possible to the maximum allowable by the buffer (2) value; The voltage conversion network (1) includes a voltage divider circuit, a multiplexer (U1), and a high-precision resistor (R0), wherein, The voltage divider circuit divides the external input voltage, which includes a plurality of high-precision matching resistors connected in series with each other, and one end of the series circuit composed of these high-precision matching resistors receives externally input positive and negative voltage signals (V _in ), the other end is grounded; and an output terminal is drawn between two adjacent series resistors as the output terminal of the voltage divider circuit; Each input end of the multiplexer (U1) is connected to the output end of the voltage divider circuit accordingly, and its control end receives the control signal from the single-chip microcomputer (3), and the output end of the multiplexer Connect the input end of the buffer (2); the multiplexer (U1) selects an appropriate voltage division ratio according to the control signal of the single-chip microcomputer (3), thereby determining which output of the voltage division circuit is connected end; The high-precision resistance (R0) is connected between the output terminal of the multiplexer and the power supply (VCC) of the automatic range positive and negative voltage measurement circuit powered by a single power supply, and the voltage divider circuit and the multiplexer Adjust the externally input positive and negative voltage signals (V _in ) to an appropriate positive voltage range together. 2. The automatic range positive and negative voltage measuring circuit of single power supply according to claim 1, is characterized in that, described buffer (2) comprises matching transistor (U2), first resistance (R1), second resistance ( R2), third resistor (R3), fourth resistor (R4), fifth resistor (R5), first capacitor (C1), second capacitor (C2), current source (I _SS ), and operational amplifier (U3 ),in, The first resistor (R1) and the first capacitor (C1) are connected in parallel to form a first parallel RC circuit, one end of the first parallel RC circuit is connected to a base of the matching transistor (U2), and the first parallel RC circuit The other end is used as the input end of the buffer (2); the second resistor (R2) and the second capacitor (C2) are connected in parallel to form a second parallel RC circuit, and one end of the second parallel RC circuit is connected to the matching transistor Another base of (U2); The two collectors of the matching transistor (U2) are respectively connected to the two input terminals of the operational amplifier (U3), and the two emitters of the matching transistor (U2) are commonly connected to the current source (I _SS ) , while the other end of the current source (I _SS ) is grounded; One end of the fourth resistor (R4) and the fifth resistor (R5) are respectively connected to the two collectors of the matching transistor (U2), and the other end of the fourth resistor (R4) and the fifth resistor (R5) One end is commonly connected to one end of the third resistor (R3), and the other end of the third resistor (R3) is connected to the power supply (VCC) of the automatic range positive and negative voltage measurement circuit powered by a single power supply; The output terminal of the operational amplifier (U3) is used as the output terminal of the buffer (2); and the other end of the second parallel RC circuit is connected to the output terminal of the operational amplifier (U3) as the output terminal of the buffer Negative feedback. 3. the automatic range positive and negative voltage measurement circuit of single power supply according to claim 1, it is characterized in that: described single-chip microcomputer (3) adopts integrated circuit chip, and it has ADC module of carrying, described single-chip microcomputer (3) The input port of the ADC module receives the output signal (V _out ) from the buffer (2), performs AD conversion and logic analysis on the output signal (V _out ), and then outputs a control signal to the voltage conversion network ( 1) Adjusting the output of the voltage conversion network (1), so that the output voltage of the voltage conversion network (1) is as close as possible to the maximum value allowed by the buffer (2).