CN1755743A - Passive electromagnetic isolation signal converter - Google Patents

Abstract

The invention discloses a massive electromagnetic isolation signal converter, which comprises a push-pull drive circuit, a coupling transformer, a rectification filter circuit, a signal transition processing circuit, a power acquisition circuit and starting circuit parallel with input end of push-pull circuit; the positive and negative ends of input current signal accesses respectively positive end of power acquisition end and negative end of starting and push-pull circuits; arranging two coils to output square wave of opposite phase and provide push-pull signal and synchronous rectification signal in inner transformer in power circuit. This invention can achieve high-standard precision of output signal.

Description

Passive electromagnetic isolation signal converter

technical field

The invention relates to a passive electromagnetic isolation signal converter suitable for isolation, transformation and transmission of 4-20mA standard current signals.

Background technique

The existing passive electromagnetic isolation signal converter includes a push-pull drive circuit, a coupling transformer, a rectification filter circuit and a signal processing circuit, and a constant current source signal of 4 to 20mA is input from the current input terminal; the inflowing current signal energy makes the push-pull drive circuit Start the vibration and make the push-pull drive circuit work, and perform chopping modulation on the current signal; the current signal energy is coupled to the secondary of the transformer through the transformer, and then processed by the rectification filter circuit and signal conversion processing circuit connected to the secondary and then output from the current terminal output. This passive electromagnetic isolation signal conversion method has the following defects: (1) Because the rectification filter has no power supply, the active processing of the subsequent stage signal cannot be realized. When the load of the signal changes, the output signal amplitude changes accordingly, and it cannot be truly (2) Because the normal operation of the push-pull drive circuit shunts a part of the current, and the shunted signal cannot be compensated in the subsequent stage, so the nonlinearity is serious, and the accuracy cannot be guaranteed, usually only up to 0.2 level precision.

Contents of the invention

The purpose of the present invention is to provide a passive electromagnetic isolation signal converter, so that the output signal can reach a high standard precision, and the performance of the passive electromagnetic isolation signal converter is greatly improved.

The above object can be achieved through the following technical measures: a passive electromagnetic isolation signal converter includes a push-pull drive circuit, a coupling transformer, a rectification filter circuit and a signal conversion processing circuit, and is characterized in that it also includes an energy acquisition circuit and a start-up circuit, The start-up circuit is connected in parallel to the input end of the push-pull drive circuit, the positive end of the input current signal is connected to the positive input end of the energy harvesting circuit, and the negative end of the input current signal is connected to the negative end of the start-up circuit and the push-pull drive circuit; the energy harvesting circuit The output end of the output terminal is connected to the power supply end of the signal processing circuit. The internal transformer of the energy acquisition circuit is provided with two windings for providing push-pull drive signals and synchronous rectification signals. The two windings output square waves with opposite phases, and are connected to the corresponding Input the signal drive terminal of push-pull drive circuit and synchronous rectification circuit.

The energy harvesting circuit includes triode TS1, TS2, transformer T2, rectifier block D1, resistor R2 and capacitor C2, resistor R2 and capacitor C2 are connected in series between the input terminals of the energy harvesting circuit, and the emitters of triode TS1 and TS2 are connected And connected to the negative input terminal of the circuit, the collectors of the transistors TS1 and TS2 are respectively connected to one end of the primary coupling winding of the transformer T2, the bases of the transistors TS1 and TS2 are respectively connected to one end of the primary feedback winding of the transformer T2, and the primary coupling winding The middle tap is connected to the positive input end of the circuit, the middle tap of the primary feedback winding is connected to the series point of the resistor R2 and the capacitor C2; the terminal of the secondary winding of the transformer T2 is connected to the rectifier block D1.

The energy harvesting circuit includes triodes TS1, TS2, transformer T2, transformer T3, rectifier block D1, resistor R2 and capacitor C2, the resistor R2 and capacitor C2 are connected in series between the input ends of the energy harvesting circuit, the triodes TS1, TS2 The emitters are connected and connected to the negative input terminal of the circuit, the collectors of the transistors TS1 and TS2 are respectively connected to one end of the primary coupling winding of the transformer T2, and the collectors of the transistors TS1 and TS2 are also respectively connected to one of the primary coupling windings on the transformer T3 Inverting terminals, the bases of transistors TS1 and TS2 are respectively connected to one terminal of the primary feedback winding on transformer T3, the middle tap of the primary coupling winding on transformer T2 is connected to the positive input terminal of the circuit, and the middle of the primary feedback winding on transformer T3 The tap is connected to the series point of the resistor R2 and the capacitor C2; the terminal of the secondary winding of the transformer T2 is connected to the rectifier block D1.

The starting circuit is composed of capacitors, resistors or parallel connections of capacitors and resistors.

In order to make the energy harvesting circuit work stably, a voltage stabilizing circuit is connected in parallel between the input ends of the energy harvesting circuit. The voltage stabilizing circuit is a voltage stabilizing diode, a voltage dividing resistor or a voltage dividing capacitor.

The present invention can also be realized through the following technical solutions: a passive electromagnetic isolation signal converter includes a linear optocoupler, a rectification filter circuit and a signal conversion processing circuit, and is characterized in that it also includes an energy acquisition circuit, a voltage stabilization circuit and a signal sampling and amplification circuit , the positive terminal of the input current signal is connected to the positive input terminal of the energy harvesting circuit, and the negative terminal of the input current signal is connected to the signal sampling amplifier circuit; the voltage stabilizing circuit is connected between the positive and negative input terminals of the energy harvesting circuit, and the voltage stabilizing circuit forms The voltage of the signal sampling and amplifying circuit is connected to the power supply end of the linear optocoupler, the output of the signal sampling and amplifying circuit is connected to the input of the linear optocoupler to drive the linear optocoupler, and the output end of the energy acquisition circuit is connected to the power supply end of the signal processing circuit. The output of the linear optocoupler is connected to the signal conversion processing circuit.

Compared with the prior art, the present invention has the following advantages:

(1) By connecting the energy acquisition circuit, the energy can be obtained from the current signal input loop to supply the secondary processing circuits such as the synchronous rectification circuit and the signal conversion processing, which solves the secondary power supply problem of the signal transmission of the traditional passive electromagnetic isolation signal converter ; Make the output signal of the passive signal converter achieve high standard accuracy, linearity and temperature drift; greatly improve the performance of the passive electromagnetic isolation signal converter.

(2) A coil winding is added to the internal transformer of the energy harvesting circuit to provide driving signals for the push-pull drive circuit and the synchronous rectification circuit, so that only a simple coil winding is added to solve the problem of the chopping modulation frequency signal of the current. At the same time, the modulation frequency can be increased to a high standard, which greatly improves the response speed of the system.

(3) A start-up circuit is connected to the input end of the push-pull drive circuit, so that the input end of the energy acquisition circuit forms a loop before the push-pull drive circuit works normally. At the same time, after the push-pull drive circuit works normally, the terminal voltage of the start-up circuit automatically drops to close to zero volts, so that the start-up circuit only causes a very small shunt and will not affect the system accuracy.

Description of drawings

Fig. 1 is a functional block diagram of a specific embodiment 1 of the present invention;

Fig. 2 is the circuit schematic diagram of the specific embodiment shown in Fig. 1;

Fig. 3 is a functional block diagram of a second embodiment of the present invention;

Fig. 4 is the schematic circuit diagram of the specific embodiment shown in Fig. 3;

Fig. 5 is a circuit schematic diagram of another embodiment of the energy harvesting circuit in the present invention.

Detailed ways

As shown in Figure 1 and Figure 2, the first embodiment includes a push-pull drive circuit, a coupling transformer T1, a rectification filter circuit, a signal conversion processing circuit, an energy acquisition circuit and a start-up circuit, and the start-up circuit is formed by the parallel connection of a capacitor C1 and a resistor R1 The starting circuit is connected in parallel to the input terminal of the push-pull drive circuit, and the positive terminal of the input current signal is connected to the positive input terminal of the energy harvesting circuit. Voltage diode V _Z , the anode of Zener diode V _z is connected to the starting circuit, and the cathode is connected to the positive end of the input current signal. The negative terminal of the input current signal is connected to the negative terminal of the startup circuit and the push-pull drive circuit. The output end of the energy harvesting circuit is connected to the power supply end of the signal processing circuit. The internal transformer of the energy harvesting circuit is provided with two windings for providing a push-pull drive signal and a synchronous rectification signal. The two windings output square waves with opposite phases, and Correspondingly connected to the signal drive end of the push-pull drive circuit and the synchronous rectification circuit.

The energy harvesting circuit includes triodes TS1, TS2, transformer T2, rectifier block D1, resistor R2 and capacitor C2. The resistor R2 and capacitor C2 are connected in series and connected between the input ends of the energy harvesting circuit. The emitters of the triodes TS1 and TS2 are connected in parallel. The collectors of the transistors TS1 and TS2 are respectively connected to one end of the primary coupling winding of the transformer T2, the bases of the transistors TS1 and TS2 are respectively connected to one end of the primary feedback winding of the transformer T2, and the middle tap of the primary coupling winding Connect the positive input end of the circuit, the middle tap of the primary feedback winding is connected to the series point of the resistor R2 and the capacitor C2; the terminal of the secondary winding of the transformer T2 is connected to the rectifier block D1. One of the transistors TS1 or TS2 is first turned on at the moment of power-on, causing the magnetic flux of the transformer T2 to change. At this time, the feedback windings 13, 14, 15 strengthen the conduction current of the transistors. The collector current of the turned-on transistor increases. When the current of the conducting triode reaches saturation, the magnetic flux of the transformer T2 no longer increases, causing the feedback winding voltage to change in reverse phase, turning off the conducting triode and turning on the originally non-conducting triode, causing oscillation. The current flows through the primary coupling winding composed of pins 1, 2, and 3 of the transformer T2 at an oscillating frequency, and the energy is coupled to the secondary composed of pins 4, 5, and 6 of the transformer T2, and then filtered by the rectifier block D1 rectifier capacitor C3 After output.

The 4 to 20mA constant current source signal is input from the Iin+ terminal. The current signal flows in from the Iin + terminal at the moment of access, flows through the voltage stabilizing circuit composed of the voltage regulator tube VZ, and flows back to Iin through the starting circuit composed of the resistor R1 and the capacitor C1. - end forms a loop. The VZ terminal of the voltage regulator tube forms a voltage to supply power to the energy harvesting circuit formed by the resistor R2, the capacitor C2, the transistors TS1 and TS2, the transformer T2, the rectifier block D1, and the filter capacitor C3, and the energy harvesting circuit works normally. Then the primary winding 7, 8, and 9 terminals of the transformer T2 output drive signals with opposite phases to make the push-pull drive circuit composed of field effect transistors MT1 and MT2 work. When FETs MT1 and MT2 enter normal push-pull driving, most of the energy of the current signal flows in from terminal 2 of the primary winding of transformer T1, and flows out from terminals 1 and 3 of the primary winding of transformer T1 back to the Iin- terminal. At this time, the voltage across the starting circuit formed by the resistor R1 and the capacitor C1 is close to zero volts, which will not cause a large shunt to Iin and will not affect the accuracy of the energy coupling of the transformer T1. The energy harvesting circuit obtains energy from the current signal, rectifies it through D1, filters it with C3, and outputs it to the signal conversion processing circuit to achieve the purpose of supplying power to the subsequent stage circuit. The signal energy is coupled to the secondary by the transformer T1 and then synchronously rectified by the field effect transistors MT3 and MT4, and then sent to the signal conversion processing circuit for processing to output a current or voltage signal.

The above-mentioned start-up circuit can also use a capacitor or a resistor alone, which can also play a start-up effect; the Zener diode can also be replaced by a resistor or a capacitor, which can also play a voltage-stabilizing effect.

As shown in Figure 3 and Figure 4, the second embodiment includes a linear optocoupler, a rectification filter circuit and a signal conversion processing circuit, and is characterized in that it also includes an energy acquisition circuit, a voltage stabilization circuit and a signal sampling and amplification circuit, and the positive input current signal connected to the positive input terminal of the energy harvesting circuit, and the negative terminal of the input current signal is connected to the signal sampling amplifier circuit; the voltage stabilizing circuit is connected between the positive and negative input terminals of the energy harvesting circuit, and the voltage formed by the voltage stabilizing circuit is connected to the signal sampling And the power supply end of the amplifier circuit and the linear optocoupler, the output of the signal sampling amplifier circuit is connected to the input of the linear optocoupler to drive the linear optocoupler, the output end of the energy acquisition circuit is connected to the power supply end of the signal processing circuit, and the output of the linear optocoupler is connected to into the signal conversion processing circuit.

The energy harvesting circuit described above is the same as that in Embodiment 1. The difference is that there is no start-up circuit, and there is no need to add coil windings to the transformer inside the energy harvesting circuit. The signal coupling transformer is replaced by a linear optocoupler. The sampling resistance should not be too large, and it should be less than 100 ohms. The voltage formed by the voltage stabilizing circuit directly supplies power to the signal sampling and amplifying circuit and the linear optocoupler IC. The current signal Iin flows through the signal sampling and amplification circuit to obtain a voltage or current signal that is linearly proportional to Iin, and then sends it to the linear optocoupler IC to drive the linear optocoupler to work. Through the coupling of light, a signal linearly proportional to the input voltage Iin is obtained at the receiving end of the linear optocoupler, which is output from the linear optocoupler and then sent to the signal conversion processor, and then the signal conversion processor outputs an isolated and transformed current or voltage signal.

As shown in Figure 4, the current flows through the voltage regulator tube and the sampling resistor R1 to form a loop, and a voltage is formed at both ends of the voltage regulator tube VZ to supply power to the energy harvesting circuit and the operational amplifier U1. The current signal flows through the sampling resistor R1 to obtain an electrical signal proportional to the signal Iin, which is sent to the operational amplifier U1 for amplification and then drives the internal light-emitting diode of the linear optocoupler U2, and the luminous intensity of the light-emitting diode is proportional to the input signal. At the same time, in order to stabilize the driving signal as soon as possible, pins 3 and 4 of the linear optocoupler U2 are connected to the inverting terminal of the operational amplifier U1 to form negative feedback. Resistor R3 is a negative feedback resistor, and capacitor C4 is a negative feedback capacitor to increase signal stability. The internal receiving tube of the linear optocoupler is irradiated by the internal light-emitting diode, and the optical signal is converted into an electrical signal, which is sent from pins 5 and 6 of the linear optocoupler U2 to the signal conversion processing circuit for processing, and then sends out a current or voltage signal proportional to Iin.

As shown in Figure 5, the energy harvesting circuit in the above embodiment can adopt another method, including triode TS1, TS2, transformer T2, transformer T3, rectifier block D1, resistor R2 and capacitor C2, after resistor R2 and capacitor C2 are connected in series Connected between the input terminals of the energy harvesting circuit, the emitters of the triodes TS1 and TS2 are connected and connected to the negative input terminal of the circuit, the collectors of the triodes TS1 and TS2 are respectively connected to one end of the primary coupling winding of the transformer T2, and at the same time the triodes TS1 and TS2 The collectors of the transistors are also respectively connected to an inverting terminal of the primary coupling winding on the transformer T3, the bases of the transistors TS1 and TS2 are respectively connected to one terminal of the primary feedback winding on the transformer T3, and the middle tap of the primary coupling winding on the transformer T2 Connect the positive input terminal of the circuit, the middle tap of the primary feedback winding on the transformer T3 is connected to the series point of the resistor R2 and the capacitor C2; the terminal of the secondary winding of the transformer T2 is connected to the rectifier block D1.

At the moment of power-on, one of the transistors TS1 or TS2 is turned on first, causing the magnetic flux of the transformer T3 to change. The two ends of another winding formed by the 16 and 17 feet of the transformer T3 are connected to the 1 and 3 feet of the T2. At this time, the function of the feedback winding composed of the 13, 14, and 15 feet of the transformer T3 is to strengthen the conduction current of the triode. The collector current of the turned-on transistor increases. When the current of the conduction triode reaches saturation, the magnetic flux of the transformer T3 no longer increases, causing the feedback winding voltage to change in reverse phase, turning off the conduction triode and turning on the non-conduction triode, causing oscillation. The current flows through the winding composed of pins 1, 2, and 3 of the transformer T2 at an oscillating frequency, and the energy is coupled to the secondary composed of pins 4, 5, and 6 of the transformer T2, and then output after being filtered by the rectifying block D1 and the rectifying capacitor C3. The energy harvesting circuit uses the transformer T3 as a saturated transformer for the feedback signals of the triode TS1 and TS2, so that the signal is separated from the main energy transformer T2. That is to say, the main energy transformer T2 can realize energy coupling without reaching magnetic core saturation, which greatly reduces the heat loss of the transformer. In addition, by adjusting the turns ratio of the transformer T3, it is easy to adjust the oscillation frequency, which can greatly increase the oscillation frequency while ensuring that the transformer does not generate heat. There are two advantages to a significant increase in the oscillation frequency; first, the transformer T2 core needs only a small number of coil turns to achieve greater power transmission; second, it can greatly improve the chopping of the transformer T1 signal coupling transformer. Wave frequency, greatly improving the signal response speed.

Claims (6)

1, a kind of passive electromagnetic isolated signal converter, comprise push-pull driver circuit, coupling transformer, current rectifying and wave filtering circuit and signal transformation treatment circuit, it is characterized in that also comprising energy harvesting circuit and start-up circuit, start-up circuit is parallel to the input end of push-pull driver circuit, the anode of input current signal inserts the positive input terminal of energy harvesting circuit, and the negative terminal of input current signal inserts the negative terminal of start-up circuit and push-pull driver circuit; The output terminal of energy harvesting circuit inserts the power supply side of signal processing circuit, be provided with at the internal transformer of energy harvesting circuit and be used to provide two windings of recommending drive signal and synchronous rectification signal, the opposite square wave of two winding output phases, and insert the signal drive end of push-pull driver circuit and circuit of synchronous rectification accordingly.

2, passive electromagnetic isolated signal converter according to claim 1, it is characterized in that described energy harvesting circuit comprises triode TS1, TS2, transformer T2, rectifying block D1, resistance R 2 and capacitor C 2, after being in series, resistance R 2 and capacitor C 2 be connected between the energy harvesting circuit input end, triode TS1, the emitter of TS2 links to each other and the place in circuit negative input end, triode TS1, the collector of TS2 connects a transformer T2 termination of grade coupled winding just separately, triode TS1, the base stage of TS2 connects a termination of the elementary feedback winding of transformer T2 separately, the positive input terminal of the centre tap connecting circuit of first grade coupled winding, the centre tap of elementary feedback winding connects the series connection point of resistance R 2 and capacitor C 2; The secondary winding termination of transformer T2 connects rectifying block D1.

3, passive electromagnetic isolated signal converter according to claim 1, it is characterized in that described energy harvesting circuit comprises triode TS1, TS2, transformer T2, transformer T3, rectifying block D1, resistance R 2 and capacitor C 2, after being in series, resistance R 2 and capacitor C 2 be connected between the energy harvesting circuit input end, triode TS1, the emitter of TS2 links to each other and the place in circuit negative input end, triode TS1, the collector of TS2 connects a transformer T2 termination of grade coupled winding just separately, while triode TS1, the collector of TS2 also connects an anti-phase termination of the first grade coupled winding on the transformer T3 separately, triode TS1, the base stage of TS2 connects a termination of the elementary feedback winding on the transformer T3 separately, transformer T2 goes up the positive input terminal of the centre tap connecting circuit of grade coupled winding just, and transformer T3 goes up the centre tap connection resistance R 2 of elementary feedback winding and the series connection point of capacitor C 2; The secondary winding termination of transformer T2 connects rectifying block D1.

4, passive electromagnetic isolated signal converter according to claim 1 is characterized in that described start-up circuit is electric capacity, resistance or being formed in parallel by electric capacity, resistance.

5, according to claim 1,2 or 3 described passive electromagnetic isolated signal converters, it is characterized in that shunt regulating circuit between the input end of described energy harvesting circuit, this mu balanced circuit is voltage stabilizing diode, divider resistance or dividing potential drop electric capacity.

6, a kind of passive electromagnetic isolated signal converter, comprise linear optical coupling, current rectifying and wave filtering circuit and signal transformation treatment circuit, it is characterized in that also comprising energy harvesting circuit, mu balanced circuit and signal sampling amplifying circuit, the anode of input current signal inserts the positive input terminal of energy harvesting circuit, and the negative terminal of input current signal inserts the signal sampling amplifying circuit; Mu balanced circuit is connected between the positive-negative input end of energy harvesting circuit, the voltage that mu balanced circuit forms inserts the power end of signal sampling and amplifying circuit and linear optical coupling, the input that the output of signal sampling amplifying circuit connects linear optical coupling drives linear optical coupling, the output terminal of energy harvesting circuit inserts the power supply side of signal processing circuit, and the output of linear optical coupling inserts the signal transformation treatment circuit.

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