CN104617939A - PWM (Pulse Width Modulation) analog quantity based channel switching device - Google Patents
PWM (Pulse Width Modulation) analog quantity based channel switching device Download PDFInfo
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- CN104617939A CN104617939A CN201410850663.2A CN201410850663A CN104617939A CN 104617939 A CN104617939 A CN 104617939A CN 201410850663 A CN201410850663 A CN 201410850663A CN 104617939 A CN104617939 A CN 104617939A
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Abstract
The invention relates to a PWM (Pulse Width Modulation) analog quantity based channel switching device. The PWM analog quantity based channel switching device comprises an input pulse PWM circuit, a filter shaping circuit and a V/I output driving circuit; a periodical pulse is controlled by an upper computer, wherein the adjustable duty ratio is output from the periodical pulse; the pulse is connected with an input end of an isolation optical coupler; one output end of the isolation optical coupler is connected with the power voltage through a resistor; each end of the resistor is connected with a voltage limiting and regulator tube; the other output end of the isolation optical coupler is connected with the ground through a triode; the isolation optical coupler is on or off to enable the power voltage to charge or discharge a charging capacitor through the resistor; a negative end of the charging capacitor is connected with an RC (Resistor-Capacitor) filter circuit; the output voltage of the filter shaping circuit is fed back to an output precision resistor through an operational amplifier; the voltage difference of two ends of the precision resistor is converted into the standard 4 to 20 milliamperes of standard current to the output; a duty ratio controllable pulse signal is converted into a standard signal to be output. The PWM analog quantity based channel switching device is suitable for various control circuit boards, the multi-channel analog quantity output which is isolated independently can be extended freely, the cost is low, the stability is good, the failure rate is low, the calibration is simple, and the accuracy is high.
Description
Technical field
The present invention relates to a kind of analog signal conversion equipment, particularly one is based on PWM analog quantity channel conversion equipment.
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 present invention be directed to that present ADC conversion cost is high, failure rate is high, the problem of poor anti-interference, propose 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.
Technical scheme of the present invention is: a kind of based on PWM analog quantity channel conversion equipment, 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.
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.
Beneficial effect of the present invention is: the present invention is a kind of is adapted to various control circuit board based on PWM analog quantity channel conversion equipment, 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 present invention is a kind of based on PWM analog quantity channel conversion equipment passage schematic diagram;
Fig. 2 is that the present invention is a kind of based on PWM analog quantity channel conversion equipment 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 conversion equipment, 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 conversion equipment, 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 conversion equipment, 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 |
|---|---|---|---|
| CN201410850663.2A CN104617939A (en) | 2014-12-31 | 2014-12-31 | PWM (Pulse Width Modulation) analog quantity based channel switching device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410850663.2A CN104617939A (en) | 2014-12-31 | 2014-12-31 | PWM (Pulse Width Modulation) analog quantity based channel switching device |
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| CN104617939A true CN104617939A (en) | 2015-05-13 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201410850663.2A Pending CN104617939A (en) | 2014-12-31 | 2014-12-31 | PWM (Pulse Width Modulation) analog quantity based channel switching device |
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| CN (1) | CN104617939A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106169912A (en) * | 2016-06-28 | 2016-11-30 | 浙江中医药大学 | Pulse wave generation circuit |
| CN109449509A (en) * | 2018-10-18 | 2019-03-08 | 陈明 | A kind of lead-acid accumulator off-network restorative procedure and instrument for repairing |
| CN113325742A (en) * | 2021-04-14 | 2021-08-31 | 珠海派诺科技股份有限公司 | Analog signal control circuit for motor protector |
-
2014
- 2014-12-31 CN CN201410850663.2A patent/CN104617939A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106169912A (en) * | 2016-06-28 | 2016-11-30 | 浙江中医药大学 | Pulse wave generation circuit |
| CN109449509A (en) * | 2018-10-18 | 2019-03-08 | 陈明 | A kind of lead-acid accumulator off-network restorative procedure and instrument for repairing |
| CN113325742A (en) * | 2021-04-14 | 2021-08-31 | 珠海派诺科技股份有限公司 | Analog signal control circuit for motor protector |
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| Date | Code | Title | Description |
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| C06 | Publication | ||
| PB01 | Publication | ||
| ASS | Succession or assignment of patent right |
Owner name: SHANGHAI AUTOMATION INSTRUMENTATION CO., LTD. Free format text: FORMER OWNER: SHANGHAI AUTOMATIC INDUSTRUMENT AND METER CO LTD Effective date: 20150619 |
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| C41 | Transfer of patent application or patent right or utility model | ||
| TA01 | Transfer of patent application right |
Effective date of registration: 20150619 Address after: Zhabei District Shanghai City, No. 191 West Guangzhong road 200072 No. 7 Applicant after: Shanghai instrument and meter for automation company limited Address before: 200233, No. 41 Rainbow Road, Shanghai, Xuhui District Applicant before: Shanghai Automatic Industrument and Meter Co., Ltd. |
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| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20150513 |
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| WD01 | Invention patent application deemed withdrawn after publication |