CN213461718U - Isolated output circuit - Google Patents
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- CN213461718U CN213461718U CN202021880266.7U CN202021880266U CN213461718U CN 213461718 U CN213461718 U CN 213461718U CN 202021880266 U CN202021880266 U CN 202021880266U CN 213461718 U CN213461718 U CN 213461718U
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Abstract
The utility model discloses an keep apart output circuit, include: the circuit comprises an isolation circuit, a voltage stabilizing circuit and an adjusting circuit; the isolation circuit is connected with the voltage stabilizing circuit and the adjusting circuit, and is used for receiving the pulse width modulation wave, isolating the pulse width modulation wave and then sending the isolated pulse width modulation wave to the adjusting circuit; the voltage stabilizing circuit is connected with the adjusting circuit and used for stabilizing the power supply voltage, outputting reference voltage and sending the reference voltage to the adjusting circuit; and the adjusting circuit is used for controlling the output current according to the isolated pulse width modulation wave. The isolation circuit is used for isolating the pulse width modulation wave, so that the cost is low, the reliability is high, and fewer I/O ports of a main board are occupied; the reference voltage is generated through the voltage stabilizing circuit, the output current is controlled by the adjusting circuit according to the isolated pulse width modulation wave, fewer devices are needed, and less space of a PCB is occupied.
Description
Technical Field
The utility model relates to a circuit field especially relates to an keep apart output circuit.
Background
In industrial application, an instrumentation amplifier is usually used to perform signal conditioning and long-line transmission, but the following problems occur: (A) because the transmitted signal is a voltage signal, the transmission line is easily interfered by noise, so that a large error is generated in signal transmission; (B) the distributed resistance of the transmission line will generate voltage drop; (C) supply voltage supply problems for instrumentation amplifiers. To solve the above problem and to avoid the effect of noise, the transmission of signals is generally performed using current signals (insensitive to noise and free from voltage drop problem), where 4mA represents a zero signal, 20mA represents a full scale value of the signal, and signals below 4mA and above 20mA are used for the alarm of various faults.
At present, the 4-20mA current output scheme mainly comprises the following scheme designs:
the integrated AO (analog output) module can output a corresponding isolated current value only by providing an external power supply voltage for the AO module and inputting a DAC level value to an input pin of the AO module. The main core devices are a DAC chip and an AO integrated module, however, the DAC chip is expensive, needs to occupy more I/O port resources of the main control MCU and occupies larger PCB area;
the conversion from the voltage signal to the circuit signal is realized by using a special conversion chip (XTR110, XTR115, etc.), but the cost of the special conversion chip is very high, the design of the adjusting circuits such as resistors, capacitors, MOS tubes, etc. on the periphery of the chip is complicated, the circuit application occasion is limited, and the design of the scheme also inevitably needs to use a DAC chip and at least three opto-couplers to realize the isolation function, the price is high, the I/O port resource of the master control MCU needs to be occupied, the circuit design is complicated, the reliability is poor, and the output precision is low.
In summary, it is desirable to provide an isolated output circuit with low cost, less occupied I/O ports of a motherboard, less occupied PCB space, and high reliability.
SUMMERY OF THE UTILITY MODEL
In order to reduce cost, improve reliability and output precision, the utility model provides an keep apart output circuit, include: the circuit comprises an isolation circuit, a voltage stabilizing circuit and an adjusting circuit;
the isolation circuit is connected with the voltage stabilizing circuit and the adjusting circuit, and is used for receiving the pulse width modulation wave, isolating the pulse width modulation wave and then sending the isolated pulse width modulation wave to the adjusting circuit;
the voltage stabilizing circuit is connected with the adjusting circuit and used for stabilizing the power supply voltage, outputting reference voltage and sending the reference voltage to the adjusting circuit;
and the adjusting circuit is used for controlling the output current according to the isolated pulse width modulation wave.
Preferably, the voltage stabilizing circuit includes: the filter circuit comprises a voltage stabilizing sub-circuit, a first filter circuit, a second filter circuit and a load;
the voltage stabilizing sub-circuit is connected with the first filter circuit and the second filter circuit in parallel, one end of the voltage stabilizing sub-circuit inputs power supply voltage, the voltage stabilizing circuit processes the power supply voltage and outputs reference voltage to the isolation circuit and the adjusting circuit through the other end of the voltage stabilizing sub-circuit;
and the load is connected with one end of the voltage stabilizing sub-circuit, which outputs the reference voltage. Preferably, the isolation circuit includes: an optical coupling circuit and a third filter circuit;
the third filter circuit is connected with the output end of the optical coupling circuit;
the input end of the optical coupling circuit is connected with the main control circuit, receives the pulse width modulation wave, generates an isolated pulse width modulation wave, and outputs the pulse width modulation wave to the adjusting circuit through the output end.
The isolation output of the 4-20mA signal is realized by using a single optical coupler, the isolation output of the isolation circuit is realized on the basis of controlling the cost, and the safety and reliability of the circuit are improved. Preferably, the adjustment circuit includes: a level selection circuit and a negative feedback circuit;
the input end of the level selection circuit is connected with the isolation circuit and the voltage stabilizing circuit, and the output end of the level selection circuit is connected with the negative feedback circuit;
the negative feedback circuit controls the output current according to the output level of the level selection circuit.
Preferably, the level selection circuit includes: the first switch circuit, the fourth filter circuit and the fifth filter circuit;
the input end of the first switch circuit is respectively used for receiving the power supply voltage, the reference voltage and the isolated pulse width modulation wave, and the output end of the first switch circuit is connected with the negative feedback circuit through the fourth filter circuit and the fifth filter circuit in sequence.
Preferably, the negative feedback circuit includes: the circuit comprises an operational amplifier, a triode Q1, a first TVS (transient voltage suppressor) tube, a second TVS tube, a first current limiting resistor, a second current limiting resistor, a third current limiting resistor, a first filter capacitor, a second filter capacitor, a control circuit and a precision resistor;
the positive phase input end of the operational amplifier is connected with the level selection circuit, the negative phase input end of the operational amplifier is connected with the triode Q1 through the first current-limiting resistor, and the output end of the operational amplifier is connected with the second current-limiting resistor;
the second current limiting resistor is connected with the first TVS tube and the control circuit;
the first TVS tube and the control circuit are connected with one end of a third current limiting resistor;
the other end of the third current-limiting resistor is connected with a triode Q1;
the triode Q1 is connected with the control circuit, the first filter capacitor and the second TVS tube;
and one end of the precision resistor is connected with the second filter capacitor, and the other end of the precision resistor is connected with the triode Q1.
The first TVS tube enables the negative feedback circuit to have an open circuit fault tolerance function, and when the industrial application site is open circuit, the first TVS tube ensures that an MOS tube in the control circuit is not broken down, and the negative feedback circuit and the output of the negative feedback circuit are not affected. The second TVS tube enables the negative feedback circuit to have a short-circuit fault tolerance function, and when a short circuit occurs in an industrial application field, the negative feedback circuit and the output of the negative feedback circuit are not affected. The precision resistor can output the full-range current of 0-25mA, and the application scene is wider. An operational amplifier and a precision resistor, so that the design cost of the isolation output circuit is greatly saved on the premise of ensuring good precision.
Preferably, the first filter circuit and the second filter circuit each include a capacitor;
the voltage regulation sub-circuit includes an analog switch.
Preferably, the third filter circuit comprises a capacitor;
the optocoupler circuit includes an optocoupler.
Preferably, the first switching circuit comprises an analog switch;
and the fourth filter circuit and the fifth filter circuit both comprise a capacitor and a resistor.
Preferably, the control circuit comprises a PMOS transistor or a triode.
The utility model has the advantages that: the isolation circuit is used for isolating the pulse width modulation wave, so that the cost is low, the reliability is high, and fewer I/O ports of a main board are occupied; the reference voltage is output through the voltage stabilizing circuit, the output current is controlled by the adjusting circuit according to the isolated pulse width modulation wave, fewer devices are needed, and less space of a PCB is occupied.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to denote like parts throughout the drawings.
In the drawings:
fig. 1 is a schematic diagram of an isolated output circuit provided by the present invention;
FIG. 2 is a schematic diagram of a voltage regulator circuit for isolating an output circuit according to the present application;
FIG. 3 is a schematic diagram of an isolation circuit for isolating an output circuit provided herein;
FIG. 4 is a schematic diagram of an adjustment circuit for an isolated output circuit provided herein;
fig. 5 is a circuit schematic of another isolated output circuit provided herein.
Description of the reference numerals
Iout output current 101 isolation circuit
102 voltage stabilizing circuit 103 regulating circuit
111 photo-coupling circuit 112 third filter circuit
121 voltage regulation subcircuit 122 first filter circuit
123 second filter circuit 124 load
131 level selection circuit 132 negative feedback circuit
311 first switching circuit 312 fourth filter circuit
313 fifth filter circuit U3 operational amplifier
Q1 triode D1 first TVS tube
D2 second TVS tube R4 first current limiting resistor
R7 second current limiting resistor R5 third current limiting resistor
C11 first filter capacitor C1 second filter capacitor
330 control circuit R2 precision resistor
DGND digital ground GND ground
PWM pulse width modulation wave SW isolated pulse width modulation wave
VDA supply voltage VCC supply voltage
DAREF reference voltage
Detailed Description
Exemplary embodiments of the present invention will be further described with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The utility model provides an keep apart output circuit, as shown in fig. 1, include: an isolation circuit 101, a voltage stabilizing circuit 102, and an adjustment circuit 103.
The isolation circuit is connected with the voltage stabilizing circuit and the adjusting circuit, and the isolation circuit is used for receiving the pulse width modulation wave, isolating the pulse width modulation wave and then sending the isolated pulse width modulation wave to the adjusting circuit.
The voltage stabilizing circuit is connected with the adjusting circuit and used for stabilizing the power supply voltage, outputting the reference voltage and sending the reference voltage to the adjusting circuit.
And the adjusting circuit is used for controlling the output current according to the isolated pulse width modulation wave.
A voltage regulator circuit, comprising: a voltage regulation sub-circuit 121, a first filter circuit 122, a second filter circuit 123 and a load 124. The voltage stabilizing sub-circuit is connected with the first filter circuit and the second filter circuit in parallel, one end of the voltage stabilizing sub-circuit inputs power supply voltage, the voltage stabilizing circuit outputs reference voltage after processing the power supply voltage, and the reference voltage is output to the isolation circuit and the adjusting circuit through the other end of the voltage stabilizing sub-circuit. The load is connected with one end of the voltage stabilizing sub-circuit, which outputs the reference voltage. The first filter circuit and the second filter circuit both comprise capacitors, and the voltage-stabilizing sub-circuit comprises analog switches.
As shown in fig. 2, the zener sub-circuit includes a zener diode U2, the first filter circuit includes a capacitor C2, the second filter circuit includes a capacitor C6, and the load 124 includes a resistor R6. Pin 1 of the zener diode U2 is connected to one end of the capacitor C6 and the supply voltage VDA, and pin 2 of the zener diode U2 is connected to one end of the resistor R6, the other end of the capacitor C6, and one end of the capacitor C2. Pin 3 of the zener diode U2 and the other end of the capacitor C2 are both connected to the supply voltage VDA. The other end of the resistor R6 is connected to ground. Wherein the capacitor C2 and the capacitor C6 serve as a filter capacitor for the supply voltage VDA, the zener diode U2 outputs a reference voltage (regulated value) DAREF at pin 2 when the voltage VDA is applied to pin 3. Resistor R6 is connected between pin 2 of zener diode U2 and GND as a load resistor for reference voltage DAREF.
An isolation circuit, comprising: a photo coupling circuit 111 and a third filter circuit 112. The third filter circuit is connected with the output end of the optical coupling circuit. The input end of the optical coupling circuit is connected with the main control circuit, receives the pulse width modulation wave, generates an isolated pulse width modulation wave, and outputs the isolated pulse width modulation wave to the adjusting circuit through the output end. The third filter circuit includes a capacitor and the optocoupler circuit includes an optocoupler.
As shown in fig. 3, the optocoupler circuit includes an optocoupler U1 and the third filter circuit includes a capacitor C4. The isolation circuit further comprises a resistor R1, a resistor R3 and a capacitor C3. The cathode of the optocoupler U1 is connected to the pulse width modulation wave control circuit, receives the pulse width modulation wave PWM, the anode is connected to one end of a resistor R3, the emitter is connected to one end of a capacitor C4 and the reference voltage DAREF, and the collector is connected to the other end of the capacitor C4, one end of a resistor R1, and the adjustment circuit. The other end of the resistor R3 is connected to one end of the capacitor C3 and the power supply voltage VCC, the other end of the capacitor C3 is grounded, and the other end of the resistor R1 is connected to the power supply voltage. When the pulse width modulation wave is at a high level, the level of a collector output end signal SW (isolated pulse width modulation wave) is VDA; when the pulse width modulation wave is at a low level, the output end signal (the isolated pulse width modulation wave) is DAREF. The optical coupling circuit can realize the isolation and conversion of the PWM signal at the main control chip side into the SW signal at the isolation end (the isolated PWM wave). C3 and C4 are filter capacitors of power supplies VCC and VDA respectively; resistor R1 is a pull-up resistor for supply voltage VCC, and resistor R3 is a pull-up resistor for supply voltage VDA. The SW signal does not represent a switching signal here, but represents only a pulse width modulated wave after being isolated by the photo coupling circuit. When the duty ratio of the pulse width modulation wave PWM is 40%, the duty ratio of the pulse width modulation wave (SW signal) after isolation is also 40%.
An adjustment circuit, comprising: a level selection circuit 131 and a negative feedback circuit 132. The input end of the level selection circuit is connected with the isolation circuit and the voltage stabilizing circuit, and the output end of the level selection circuit is connected with the negative feedback circuit. The negative feedback circuit controls the output current according to the output level of the level selection circuit.
A level selection circuit, comprising: a first switch circuit 311, a fourth filter circuit 312, and a fifth filter circuit 313. The input end of the first switch circuit is respectively used for receiving the power supply voltage, the reference voltage and the isolated pulse width modulation wave, and the output end of the first switch circuit is connected with the negative feedback circuit through the fourth filter circuit and the fifth filter circuit in sequence. The first switch circuit comprises an analog switch, and the fourth filter circuit and the fifth filter circuit respectively comprise a capacitor and a resistor.
As shown in fig. 4, the first switch circuit includes an analog switch U4, the fourth filter circuit is an RC filter circuit including a resistor R8 and a capacitor C7, and the fifth filter circuit is an RC filter circuit including a resistor R9 and a capacitor C8. The level selection circuit further includes a capacitor C5 and a capacitor C9. Pin 1 of the analog switch U4 is connected to the voltage regulator circuit output reference voltage DAREF and one end of the capacitor C9. Pin 2 is connected to the voltage regulator circuit output voltage DAREF and to one terminal of a capacitor C5. Pin 3 is connected to supply voltage VDA and to the other terminal of capacitor C9. The pin 4 is connected to a negative feedback circuit via a resistor R8 and a resistor R9 connected in series. Pin 5 is connected to the other end of capacitor C5. Pin 6 is connected to the collector of optocoupler U1 and receives the isolated pulse width modulated wave (SW signal). One end of the capacitor C7 is connected to the supply voltage VDA and one end of the capacitor C8, and the other end is connected to one ends of the resistor R8 and the resistor R9. The other end of the capacitor C8 is connected to the other end of the resistor R9. The level selection circuit is used for realizing the selection function of the level of the output end of the analog switch U4. When the collector output terminal signal SW is at level VDA, the output pin (pin 4) of the analog switch U4 outputs a level value DAREF; pin 4 of analog switch U4 outputs a level value VDA when the collector output signal SW is at level DAREF. Two sections of RC filter circuits (a fourth filter circuit and a fifth filter circuit) are formed by C7, R8, C8 and R9, and the stability of voltage output by the analog switch U4 can be guaranteed.
The negative feedback circuit includes: the circuit comprises a U3 operational amplifier U3, a triode Q1Q1, a first TVS tube D1, a second TVS tube D2, a first current limiting resistor R4, a second current limiting resistor R7, a third current limiting resistor R5, a first filter capacitor C11, a second filter capacitor C1, a control circuit 330 and a precision resistor R2. The positive phase input end of the operational amplifier is connected with the level selection circuit, the negative phase input end of the operational amplifier is connected with the triode Q1 through the first current limiting resistor, and the output end of the operational amplifier is connected with the second current limiting resistor. The second current limiting resistor is connected with the first TVS tube and the control circuit. The first TVS tube and the control circuit are connected with one end of the third current limiting resistor. The other end of the third current limiting resistor is connected with a triode Q1. The triode Q1 is connected with the control circuit, the first filter capacitor and the second TVS tube. And one end of the precision resistor is connected with the second filter capacitor, and the other end of the precision resistor is connected with the triode Q1. The operational amplifier comprises an operational amplifier, the control circuit comprises a PMOS (P-channel metal oxide semiconductor) tube or a triode, the first TVS tube comprises a diode, the second TVS tube comprises a TVS tube, the first current-limiting resistor, the second current-limiting resistor and the third current-limiting resistor comprise resistors, the first filter capacitor and the second filter capacitor comprise capacitors, and the precision resistor comprises a precision resistor.
As shown in fig. 4, the control circuit includes a PMOS transistor Q2, and the PMOS transistor Q2 may be replaced by a triode. The negative feedback circuit also includes a capacitor C10. The operational amplifier U3 has a forward input (pin 3) connected to the resistor R9 and the capacitor C8, a reverse input (pin 2) connected to one end of the resistor R4, and an output (pin 1) connected to one end of the capacitor R7. The ground terminal of the operational amplifier U3 is grounded, and the power supply voltage terminal is connected to the power supply voltage and one terminal of the capacitor C10. The other terminal of the capacitor C10 is connected to ground. The other end of the resistor R7 is connected to one end of the TVS transistor D1 and the gate of the PMOS transistor Q2. The source of the PMOS transistor Q2 is connected to the other end of the TVS transistor D1 and one end of the resistor R5, and the drain is connected to the collector of the transistor Q1, one end of the capacitor C11 and one end of the TVS transistor D2. The other end of the resistor R5 is connected with the base of the triode Q1. An emitter of the transistor Q1 is connected to one end of the resistor R2 and the other end of the resistor R4. The other end of the resistor R2 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is grounded. The other end of the capacitor C11 and the other end of the TVS tube D2 are both grounded.
The embodiment of the present application further includes a pulse width modulation wave control circuit. The pulse width modulation wave control circuit is connected with the isolation circuit and used for generating pulse width modulation waves and sending the pulse width modulation waves to the isolation circuit.
The pulse width modulation wave control circuit includes a main control chip that can generate a pulse width modulation wave. The main control chip on the main control board generates a pulse width modulation wave through I/O control, and the duty ratio of the pulse width modulation wave is adjustable.
When the power supply voltage VDA is just powered on, the inverting input terminal of the operational amplifier U3 is pulled up to the VDA level by the resistor R2, and the non-inverting input terminal of the operational amplifier U3 is smaller than the VDA value, so the operational amplifier U3 outputs a low level, the PMOS transistor Q2 is turned on, the resistor R2 has current flowing through it, and the voltage at the inverting input terminal of the operational amplifier U3 is lowered to form negative feedback. The TVS transistor D1 is used to prevent the PMOS transistor Q2 from breakdown, and the TVS transistor D2 is used to suppress the transient current at the output current (Iout) port and protect the output port circuit. R2 is a precision resistor, and the resistance value of the precision resistor changes little with the temperature; the transistor Q1 acts as a switching device so that the circuit forms a complete loop.
The implementation mode of the application also comprises a peripheral connection device, and the output current Iout of the current output port (Iout) is sent to the peripheral device.
The isolation output of the 4-20mA signal is realized by using a single optical coupler, the isolation output of the adjusting circuit is realized on the basis of controlling the cost, and the safety and reliability of the circuit scheme are improved. The TVS tube D2 is used for restraining transient current of an output current port, can protect an output port circuit, has no influence on an adjusting circuit when short circuit occurs in an industrial application field, and can tolerate short circuit fault. Because the MOS pipe of regulating circuit has increased TVS pipe D1, so when industrial application scene appears breaking, the TVS pipe can guarantee that the MOS pipe is not punctured, does not have the influence to the regulating circuit, can tolerate the fault of opening a circuit. The embodiment of the application can output the full-range current of 0-25mA, and the application scene is wider. The conversion process from analog quantity to digital quantity is controlled by using a pulse width modulation wave control circuit, so that a DAC chip with high price can be saved, and the design cost of the circuit is further reduced. The implementation mode of the application has fewer core devices, mainly comprises an operational amplifier and a precision resistor, and greatly saves the design cost on the premise of ensuring good precision. The implementation mode of the application only needs to occupy one I/O port with a pulse width modulation function of the main board MCU to realize the reliable output of the 4-20mA current signal. The implementation mode of the application is built by discrete basic components and parts completely, and the 4-20mA output function is realized under the condition that the PCB layout space is extremely small, so that the cost is greatly reduced, the flexibility of product design is enriched, and the precision resistor enables the 4-20mA signal output precision to be higher.
The following examples are provided to further illustrate the present application.
As shown in fig. 5, the power supply supplies an operating voltage (e.g., a power supply voltage) and an operating current required by the circuit to the whole circuit system, and generally uses the existing power supply circuit of the main control board to supply power. The power supply also provides a supply voltage VDA. The pulse width modulation wave control circuit generates a pulse width modulation wave by using the I/O of a main control chip on a main control board, thereby realizing the function of adjusting output current. And the voltage stabilizing circuit is used for mainly providing a reference voltage (voltage reference value) DAREF for the rear-end regulating circuit. And the isolation circuit converts the pulse width modulation wave at the main control chip side into the pulse width modulation wave waveform at the isolation side, so as to realize the isolation of the safety area and the dangerous area. The adjusting circuit controls the output current according to the duty ratio of the pulse width modulation wave after the isolation. The field device comprises dangerous side equipment such as a transmitter, a flowmeter and the like, mainly receives a 4-20mA output signal and belongs to peripheral connecting equipment.
The power supply is powered on to generate a power supply voltage VDA, and a reliable reference voltage DAREF with high precision can be provided for the isolation circuit and the adjusting circuit due to the voltage stabilizing function of the voltage stabilizing circuit. After the electrification is finished, the I/O port of a main control chip in the pulse width modulation wave control circuit controls and outputs a pulse width modulation wave with adjustable duty ratio, and the pulse width modulation wave passes through the isolation circuit to generate an isolated pulse width modulation wave (SW). The reference voltage DAREF and the isolated pulse width modulation wave act on the adjusting circuit at the same time, when the level of the isolated pulse width modulation wave is VDA, the pin 4 of the analog switch U4 outputs DAREF, according to the negative feedback principle, the level value of the pin 2 of the operational amplifier U3 is DAREF, the emitter level of the triode Q1 is DAREF, and therefore the current output of the adjusting circuit can be calculated to be Iout(VDA-DAREF)/R2. Similarly, when the level of the isolated pulse width modulation wave is low, the output current of the adjusting circuit is zero, so that the current output is adjusted by the filtered voltage (the voltage at the resistor R2) by controlling the duty ratio of the pulse width modulation wave.
The positive alternative scheme of this application implementation side includes:
the isolation function of the isolation circuit can adopt other isolation modes for signal isolation, such as: magnetic isolation and special chip isolation are used for realizing the same function. Magnetic isolation is a magnetically coupled isolator based on magnetic isolation technology that encodes input logic transitions using pulses transmitted to the primary side of a given transformer. These pulses are coupled from the transformer primary to the secondary and are detected by the secondary circuit, which then recovers the digital signal at the output, thereby achieving isolated transmission of the signal. The special chip isolation can adopt a special signal isolation chip on the market to realize the isolated transmission design of signals, and a corresponding signal processing circuit needs to be matched at the periphery of the chip.
The reference voltage of the voltage stabilizing circuit can be designed by other schemes, such as: the power supply chip is directly adopted for design, and the output voltage of the power supply chip is used as the reference value of the voltage of the back-end circuit. For example, the power supply chip of TI company outputs 2.5V, 3V, 3.3V and 5V; the power supply chip with a small core force outputs 2.5V, 3V, 3.3V, 5V and the like. The analog switch U4 may be constructed by devices such as a switching device triode, a MOS transistor, a resistor, and a capacitor. Chip power pin decoupling capacitors (e.g., C3, C10, etc.) may be eliminated. Two sections of the RC filter circuits (the fourth filter circuit and the fifth filter circuit) may be eliminated in one set or all. The TVS tubes D1, D2 may be eliminated. The PMOS transistor Q2 can be replaced by a triode.
However, with magnetic isolation and dedicated chips, although signal isolation can also be achieved, the circuit design for magnetic isolation is complex and requires custom cores. The isolation effect can also be achieved by adopting special chip isolation, but the price of the special chip is higher, and the product development cost can be increased.
The reference voltage can be obtained by using an integrated power supply chip, but the cost is increased correspondingly, and peripheral devices are also increased correspondingly in circuit design. The level switching circuit is built by adopting the discrete switch devices, the level switching function can be realized, but the circuit design becomes complicated, an additional switch control signal is needed, the main control chip resource is occupied, and the reliability can be correspondingly reduced. The decoupling capacitor of the chip power supply pin is removed, the circuit function can be realized, but the stability is reduced, and the circuit system is easily interfered by noise. The removal of one or both of the RC filter circuits results in an unstable output signal from the analog switch U4, which may cause the back-end degeneration circuit to function abnormally. The TVS tubes D1 and D2 are removed, and the output function of the adjusting circuit can be realized, but the circuit is easy to damage and is broken down by static electricity, surge and the like. The PMOS pipe changes to the triode, and the function can be realized, but has voltage control nature device to change for current control type device, can make the circuit consumption increase, in the embodiment of this application, changes to take place to puncture moreover and damages.
The method has the advantages that the pulse width modulation wave is isolated by the isolation circuit, the cost is low, the reliability is high, and fewer I/O ports of a main board are occupied; the reference voltage is output through the voltage stabilizing circuit, the output current is controlled by the adjusting circuit according to the isolated pulse width modulation wave, fewer devices are needed, and less space of a PCB is occupied.
The above description in this specification is merely illustrative of the present invention. Those skilled in the art can make various modifications or additions to the described embodiments or substitute them in a similar manner without departing from the scope of the present invention as defined in the following claims.
Claims (10)
1. An isolated output circuit, comprising: the circuit comprises an isolation circuit, a voltage stabilizing circuit and an adjusting circuit;
the isolation circuit is connected with the voltage stabilizing circuit and the adjusting circuit, and is used for receiving the pulse width modulation wave, isolating the pulse width modulation wave and then sending the isolated pulse width modulation wave to the adjusting circuit;
the voltage stabilizing circuit is connected with the adjusting circuit and used for stabilizing the power supply voltage, outputting reference voltage and sending the reference voltage to the adjusting circuit;
and the adjusting circuit is used for controlling the output current according to the isolated pulse width modulation wave.
2. The isolated output circuit of claim 1, wherein the voltage regulator circuit comprises: the filter circuit comprises a voltage stabilizing sub-circuit, a first filter circuit, a second filter circuit and a load;
the voltage stabilizing sub-circuit is connected with the first filter circuit and the second filter circuit in parallel, one end of the voltage stabilizing sub-circuit inputs power supply voltage, the voltage stabilizing circuit processes the power supply voltage and outputs reference voltage to the isolation circuit and the adjusting circuit through the other end of the voltage stabilizing sub-circuit;
and the load is connected with one end of the voltage stabilizing sub-circuit, which outputs the reference voltage.
3. The isolated output circuit of claim 1, wherein the isolation circuit comprises: an optical coupling circuit and a third filter circuit;
the third filter circuit is connected with the output end of the optical coupling circuit;
the input end of the optical coupling circuit is connected with the main control circuit, receives the pulse width modulation wave, generates an isolated pulse width modulation wave, and outputs the pulse width modulation wave to the adjusting circuit through the output end.
4. The isolated output circuit of claim 1, wherein the adjustment circuit comprises: a level selection circuit and a negative feedback circuit;
the input end of the level selection circuit is connected with the isolation circuit and the voltage stabilizing circuit, and the output end of the level selection circuit is connected with the negative feedback circuit;
the negative feedback circuit controls the output current according to the output level of the level selection circuit.
5. The isolated output circuit of claim 4, wherein the level selection circuit comprises: the first switch circuit, the fourth filter circuit and the fifth filter circuit;
the input end of the first switch circuit is respectively used for receiving the power supply voltage, the reference voltage and the isolated pulse width modulation wave, and the output end of the first switch circuit is connected with the negative feedback circuit through the fourth filter circuit and the fifth filter circuit in sequence.
6. The isolated output circuit of claim 4, wherein the negative feedback circuit comprises: the circuit comprises an operational amplifier, a triode Q1, a first TVS (transient voltage suppressor) tube, a second TVS tube, a first current limiting resistor, a second current limiting resistor, a third current limiting resistor, a first filter capacitor, a second filter capacitor, a control circuit and a precision resistor;
the positive phase input end of the operational amplifier is connected with the level selection circuit, the negative phase input end of the operational amplifier is connected with the triode Q1 through the first current-limiting resistor, and the output end of the operational amplifier is connected with the second current-limiting resistor;
the second current limiting resistor is connected with the first TVS tube and the control circuit;
the first TVS tube and the control circuit are connected with one end of a third current limiting resistor;
the other end of the third current-limiting resistor is connected with a triode Q1;
the triode Q1 is connected with the control circuit, the first filter capacitor and the second TVS tube;
and one end of the precision resistor is connected with the second filter capacitor, and the other end of the precision resistor is connected with the triode Q1.
7. The isolated output circuit of claim 2,
the first filter circuit and the second filter circuit both comprise capacitors;
the voltage regulation sub-circuit includes an analog switch.
8. The isolated output circuit of claim 3,
the third filter circuit comprises a capacitor;
the optocoupler circuit includes an optocoupler.
9. The isolated output circuit of claim 5,
the first switching circuit comprises an analog switch;
and the fourth filter circuit and the fifth filter circuit both comprise a capacitor and a resistor.
10. The isolated output circuit of claim 6,
the control circuit comprises a PMOS tube or a triode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021880266.7U CN213461718U (en) | 2020-09-01 | 2020-09-01 | Isolated output circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021880266.7U CN213461718U (en) | 2020-09-01 | 2020-09-01 | Isolated output circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN213461718U true CN213461718U (en) | 2021-06-15 |
Family
ID=76319680
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202021880266.7U Active CN213461718U (en) | 2020-09-01 | 2020-09-01 | Isolated output circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN213461718U (en) |
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2020
- 2020-09-01 CN CN202021880266.7U patent/CN213461718U/en active Active
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| TR01 | Transfer of patent right |
Effective date of registration: 20231027 Address after: 325600 291 weft seventeen Road, Yueqing Economic Development Zone, Wenzhou, Zhejiang Patentee after: Goldcard Smart Group Co.,Ltd. Patentee after: Tancy Instrument Group Co.,Ltd. Address before: 325600 291 weft seventeen Road, Yueqing Economic Development Zone, Wenzhou, Zhejiang Patentee before: Goldcard Smart Group Co.,Ltd. |
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