CN204465501U - A kind of based on PWM analog quantity channel change-over circuit - Google Patents
A kind of based on PWM analog quantity channel change-over circuit Download PDFInfo
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- CN204465501U CN204465501U CN201420865931.3U CN201420865931U CN204465501U CN 204465501 U CN204465501 U CN 204465501U CN 201420865931 U CN201420865931 U CN 201420865931U CN 204465501 U CN204465501 U CN 204465501U
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Abstract
The utility model relates to a kind of based on PWM analog quantity channel change-over circuit, comprise input pulse pwm circuit, filtering shaping circuit, V/I output driving circuit, PC control exports the recurrent pulse of adjustable duty cycle, pulse connects isolation optocoupler input, isolation optocoupler exports one end and connects supply voltage by resistance, resistance two termination pressure limiting voltage-stabiliser tube, and isolation optocoupler exports the other end by triode ground connection, by isolation optocoupler break-make, supply voltage by resistance to charging capacitor discharge and recharge; Charging capacitor negative terminal connects RC filter circuit; Filtering shaping circuit output voltage is through operational amplifier feedback to output precision resistance, and the pressure reduction at precision resistance two ends is converted to the normalized current output of 4 ~ 20mA of standard, the pulse signal of controllable duty ratio is converted to standard signal and exports.Be adapted to various control circuit board, and the multi-analog can expanding arbitrarily independent isolating exports, cost is extremely low, good stability, and failure rate is low, and demarcate simple, precision is high.
Description
Technical field
The utility model relates to a kind of analog signal conversion, and particularly one is based on PWM analog quantity channel change-over circuit.
Background technology
The signal processed in field control system comprises Digital and analog amount signal, carry out on-the-spot instrument and control, just inevitably use signal conversion, and wherein majority is that numeral turns analog signals application.
In D/A converting circuit device, the main flow in market adopts ADC integrated chip, for scene complicated and changeable, ADC lost efficacy high, and inconvenience is applied to the occasion of multichannel isolation, and well solved these problems based on the digital-to-analogue conversion mode that PWM controls, simple and practical, and with low cost.
Summary of the invention
The utility model be high for present ADC conversion cost, failure rate is high, the problem of poor anti-interference, proposes a kind of based on PWM analog quantity channel conversion equipment, realize one overcast, efficiently, digital revolving die analog quantity high accuracy isolation and amplifier easily.
The technical solution of the utility model is: one, based on PWM analog quantity channel change-over circuit, comprises input pulse pwm circuit, filtering shaping circuit, V/I output driving circuit,
Input pulse pwm circuit: PC control exports the recurrent pulse of adjustable duty cycle, pulse connects isolation optocoupler input, isolation optocoupler exports one end and connects supply voltage by resistance, resistance two termination pressure limiting voltage-stabiliser tube, isolation optocoupler exports the other end by triode ground connection, by isolation optocoupler break-make, supply voltage by resistance to charging capacitor discharge and recharge;
Filtering shaping circuit: charging capacitor negative terminal connects RC filter circuit;
V/I output driving circuit: filtering shaping circuit output voltage is through operational amplifier feedback to output precision resistance, and the pressure reduction at precision resistance two ends is converted to the normalized current output of 4 ~ 20mA of standard.
Described filtering shaping circuit output voltage connects operational amplifier anode, and the lower end of precision resistance adopts double-triode valve to increase and exports driving, and base stage and amplifier export and connect together, and the negative terminal of operational amplifier linked by collector electrode, forms a set of negative-feedback circuit.
In described V/I output driving circuit, operational amplifier exports to connect after RC filter circuit carries out secondary filtering and connects voltage-stabiliser tube voltage stabilizing, then feeds back on precision resistance.
The beneficial effects of the utility model are: the utility model is a kind of is adapted to various control circuit board based on PWM analog quantity channel change-over circuit, and the multi-analog can expanding arbitrarily independent isolating exports, efficiently simple; Moreover its cost is extremely low, it is convenient to realize, good stability, and failure rate is low, and demarcate simple, precision is high, can reach 0.1%, not only reduce design difficulty, reduce production cost, and facilitates maintenance and signal controlling.
Accompanying drawing explanation
Fig. 1 is that the utility model is a kind of based on PWM analog quantity channel change-over circuit passage schematic diagram;
Fig. 2 is that the utility model is a kind of based on PWM analog quantity channel change-over circuit PWM working waveform figure.
Embodiment
As shown in Figure 1 based on PWM analog quantity channel conversion equipment passage schematic diagram, comprise input pulse pwm circuit, filtering shaping circuit, V/I output driving circuit.
Input pulse pwm circuit 1: as shown in Figure 2, when inputting the oscillogram of cycle 10ms, amplitude is 5V, duty ratio is PC control, for 75%, after light-coupled isolation, at the saturated on-off model of the same waveform of the secondary generation of optocoupler, amplitude is drawn high as 24V by channel power source, when pulse is low level, optocoupler is secondary to be opened, 24V power supply forms fixed access by secondary switch through R2 and T2, because the pressure limiting voltage-stabiliser tube Z1 of a 2.5V in parallel at the two ends of R2, so the voltage of voltage-stabiliser tube negative terminal is 21.5V, when impulse waveform is at high level, isolation optocoupler secondary switch disconnects, power supply 24V is directly charged to electric capacity EC by R2, periodically like this carry out discharge and recharge continuously according to certain duty ratio, the magnitude of voltage of periodically fluctuation will be obtained on electric capacity, duty ratio is larger, the area of charging is larger, thus final voltage effective value is larger and proportional with input pulse sequence.
Voltage filter shaping circuit 1: the discharge and recharge fluctuation voltage of electric capacity negative terminal is carried out RC filtering (R5C2 in figure), device parameters is after theory calculate, must through test of many times, draw optimum parameter value, can ensure strong interference immunity like this, last error can be demarcated, and the voltage that ripple is large arranges the smoother stable of process back after filtering, voltage in Fig. 2 after filter circuit, i.e. A point voltage in Fig. 1.
V/I output driving circuit 1: filtered voltage feeds back to the precision resistance R10 of output through amplifier U1, this amplifier adopts rail-to-rail output, single amplifier is convenient to multichannel isolation, good stability, temperature drift is low, can ensure that the pressure reduction at precision resistance two ends accurately reflects the PWM waveform of input, the lower end of precision resistance adopts double-triode valve T3, T4 increases output and drives, base stage and amplifier export and connect together, the negative terminal of amplifier linked by collector electrode, the a set of negative-feedback circuit of such formation, See-saw effect, stablize the pressure reduction of precision resistance, accurate and stable during output current eventually through precision resistance, 2.5 pressure reduction (2.5V provided by accurate Voltage stabilizing module Z1) after filtering, amplify and double-triode valve driving, the normalized current being produced 4 ~ 20mA by 120 Ω precision resistance R10 is exported.
The voltage that above-mentioned filtering is put in order, by operational amplifier output feedack to the precision resistance two ends exported, now voltage through twice filtering voltage regulation (refer to amplifier input EC R3 filtering and R5 C2 filtering, remove frequency glitches), highly stable, the pressure reduction at precision resistance two ends is accurately 0 ~ 2.5V, finally 0 ~ 20.8mA can be exported by 120 Ω precision resistances, i.e. 0 ~ 100% duty ratio digital quantity pulse, be converted to 0 ~ 20.8mA electric current according to a certain percentage, the cycle of pulse and device parameters are through hundreds of test experiences and draw, the precision of final output 4 ~ 20mA electric current can reach within 0.1%.
Claims (3)
1. based on a PWM analog quantity channel change-over circuit, it is characterized in that, comprise input pulse pwm circuit, filtering shaping circuit, V/I output driving circuit;
Input pulse pwm circuit: PC control exports the recurrent pulse of adjustable duty cycle, pulse connects isolation optocoupler input, isolation optocoupler exports one end and connects supply voltage by resistance, resistance two termination pressure limiting voltage-stabiliser tube, isolation optocoupler exports the other end by triode ground connection, by isolation optocoupler break-make, supply voltage by resistance to charging capacitor discharge and recharge;
Filtering shaping circuit: charging capacitor negative terminal connects RC filter circuit;
V/I output driving circuit: filtering shaping circuit output voltage is through operational amplifier feedback to output precision resistance, and the pressure reduction at precision resistance two ends is converted to the normalized current output of 4 ~ 20mA of standard.
2. according to claim 1 based on PWM analog quantity channel change-over circuit, it is characterized in that, described filtering shaping circuit output voltage connects operational amplifier anode, the lower end of precision resistance adopts double-triode valve to increase and exports driving, base stage and amplifier export and connect together, the negative terminal of operational amplifier linked by collector electrode, forms a set of negative-feedback circuit.
3. according to claim 1 based on PWM analog quantity channel change-over circuit, it is characterized in that, in described V/I output driving circuit, operational amplifier exports to connect after RC filter circuit carries out secondary filtering and connects voltage-stabiliser tube voltage stabilizing, then feeds back on precision resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420865931.3U CN204465501U (en) | 2014-12-31 | 2014-12-31 | A kind of based on PWM analog quantity channel change-over circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420865931.3U CN204465501U (en) | 2014-12-31 | 2014-12-31 | A kind of based on PWM analog quantity channel change-over circuit |
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| CN204465501U true CN204465501U (en) | 2015-07-08 |
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| CN201420865931.3U Active CN204465501U (en) | 2014-12-31 | 2014-12-31 | A kind of based on PWM analog quantity channel change-over circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106094954A (en) * | 2016-06-21 | 2016-11-09 | 浙江中控自动化仪表有限公司 | A kind of current output circuit and the electric current way of output thereof |
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2014
- 2014-12-31 CN CN201420865931.3U patent/CN204465501U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106094954A (en) * | 2016-06-21 | 2016-11-09 | 浙江中控自动化仪表有限公司 | A kind of current output circuit and the electric current way of output thereof |
| CN106094954B (en) * | 2016-06-21 | 2018-04-17 | 浙江中控自动化仪表有限公司 | A kind of current output circuit and its electric current way of output |
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