CN109100551B - High-precision power amplifier of relay protection testing device - Google Patents
High-precision power amplifier of relay protection testing device Download PDFInfo
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- CN109100551B CN109100551B CN201710472169.0A CN201710472169A CN109100551B CN 109100551 B CN109100551 B CN 109100551B CN 201710472169 A CN201710472169 A CN 201710472169A CN 109100551 B CN109100551 B CN 109100551B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/327—Testing of circuit interrupters, switches or circuit-breakers
- G01R31/3277—Testing of circuit interrupters, switches or circuit-breakers of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches
- G01R31/3278—Testing of circuit interrupters, switches or circuit-breakers of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches of relays, solenoids or reed switches
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Abstract
The invention relates to a high-precision power amplifier of a relay protection testing device. The high-precision power amplifier comprises an input stage unit, an intermediate driving stage unit, a power output stage unit and a negative feedback link unit. The input stage unit carries out differential processing on the input signal, the intermediate driving stage unit generates driving voltage through the combined action of the signal input by the input stage unit and the feedback signal input by the negative feedback link unit, and the driving power output stage unit amplifies the voltage and the power; the input end of the negative feedback link unit is connected with the output end of the power output stage unit, so that the high-precision power amplifier circuit forms a closed loop. The high-precision power amplifier realizes high-voltage and high-power output and can provide reliable and stable direct-current power supply output. The relay protection testing device provided with the high-precision power amplifier does not need to carry a high-voltage switch tester additionally when in use.
Description
Technical Field
The invention relates to a component of a relay protection testing device with high output direct-current voltage.
Background
The high output refers to short for high power output. The relay protection device is an important device for ensuring the safe and reliable operation of the power system. The power system is a complex system consisting of a generator, a transformer, a bus, a power transmission and distribution line and electric equipment. The most common and at the same time most dangerous faults in electrical power systems are abnormal connections between phases, or phases to ground, i.e. short circuits. The transmission line in the power system is determined to be the loop in the power system that is most prone to faults including short circuits due to the environmental conditions in which it is located. In addition, on the transmission line, a disconnection and a composite fault in which several faults occur simultaneously may also occur. The relay protection device has the function that when a protected element of the power system provided with the relay protection device fails, the relay protection device can automatically, quickly and selectively cut off the failed element from the power system so as to ensure that the non-failed part quickly returns to normal operation and prevent the failed element from being damaged continuously. The core devices of the relay protection device are various corresponding relays. The relay protection testing device is a device for measuring whether various parameters of the relay are normal or not.
The traditional relay protection tester adopts an OCL power amplifier (no output capacitor power amplifier), so that the relay protection tester is large and heavy in size, narrow in dynamic range and low in precision. In the prior art, the relay protection tester adopting the switching power supply and the digital power amplifier has small direct current output power, so that peak clipping and distortion are easy to occur for the display of the tested waveforms with related current or voltage and other parameter changes. The common solution is that a high-voltage switch tester is required to be additionally carried in the field test, the test process is complex, and the operation is inconvenient. The relay protection tester disclosed in the Chinese patent document CN 202720289U (application number 201220384361.7) belongs to the equipment.
Disclosure of Invention
The invention aims to solve the technical problem of providing a high-precision power amplifier of a relay protection testing device with larger direct current output power.
The technical scheme for realizing the invention is as follows: the high-precision power amplifier of the relay protection testing device is provided with a high-voltage switch testing port; the structure is characterized in that:
the high-precision power amplifier is provided with a power supply end, a signal input end and a direct current power supply output end, and comprises an input stage unit, an intermediate driving stage unit, a power output stage unit and a negative feedback link unit; the input end of the input stage unit is the signal input end of the high-precision power amplifier; the input stage unit is a circuit capable of performing differential processing on an input signal; the intermediate drive stage unit is a circuit capable of generating a drive voltage; the power output stage unit is provided with a power supply end, a driving signal input end and an output end; the power supply end of the power output stage unit is also the power supply end of the high-precision power amplifier; the power output stage unit is a circuit capable of being driven by a driving voltage and amplifying the voltage and power; the output end of the input stage unit is connected with the driving signal input end of the power output stage unit through the intermediate driving stage unit; the output end of the power output stage unit is electrically connected with the input end of the high-voltage switch test port, and the output end of the power output stage unit is also electrically connected with the input end of the negative feedback link unit; the output end of the negative feedback link unit and the output end of the input stage unit are simultaneously connected to the input end of the intermediate driving stage unit; the output end of the high-voltage switch test port is the direct-current power supply output end of the high-precision power amplifier.
Further, the high-precision power amplifier of the relay protection testing device is also provided with a waveform distortion control signal input end and a sampling signal output end; the power output stage unit of the high-precision power amplifier is also provided with a waveform distortion control signal input end which is used as the waveform distortion control signal input end of the high-precision power amplifier; the output end of the power output stage unit is also used as the sampling signal output end of the high-precision power amplifier.
The power output stage unit comprises a main circuit, a signal input circuit, a voltage stabilizing circuit, a constant current source circuit and a phototriode.
The main circuit of the power output stage unit is provided with a positive power supply end, a negative power supply end, an input end, a half-cycle signal output end, a control end and an output end; the signal input circuit is provided with a half-cycle signal input end and a half-cycle signal output end.
The positive and negative power supply ends of the main circuit are the power supply ends of the power output stage unit; the input end of the main circuit is the driving signal input end of the power output stage unit; the half-cycle signal output end of the main circuit is connected with the half-cycle signal input end of the signal input circuit; the half-cycle signal output end of the signal input circuit is connected with the control end of the main circuit; the output end of the main circuit is the output end of the power output stage unit; the cathode direction connecting end of the voltage stabilizing circuit is connected with the control end of the main circuit; the anode direction connecting end of the voltage stabilizing circuit is connected with the output end of the main circuit; the constant current source circuit is arranged between the positive power end and the control end of the main circuit; the collector electrode of the phototriode is connected with the control end of the main circuit; the emitter of the phototriode is connected with the output end of the main circuit; the base electrode of the phototriode is the waveform distortion control signal input end driven by the power output stage unit; the first control signal output end of the waveform distortion judging circuit is connected with the base electrode of the phototriode, and the connection of the corresponding light emitting diode of the waveform distortion judging circuit to the light signal emitted by the base electrode of the phototriode is realized.
Further, the main circuit of the power output stage unit of the high-precision power amplifier of the relay protection testing device consists of a push-pull power output stage circuit and a multipath expansion circuit; the push-pull power output stage circuit comprises an output stage first circuit and an output stage second circuit; each path of expansion circuit is connected with the second circuit of the output stage in parallel in a direct coupling way; the first circuit of the output stage and the second circuit of the output stage are symmetrically arranged.
The output stage second circuit is provided with a positive power supply end, a control end and a common output end; the output stage first circuit is provided with an input end, a common output end, a half-cycle signal output end and a negative power supply end; each path of expansion circuit is provided with a positive power end, a control end and an output end.
The input end of the first circuit of the output stage is the input end of the main circuit; the common output end of the first circuit of the output stage is connected with the common output end of the second circuit of the output stage; the half-cycle signal output end of the first circuit of the output stage is the half-cycle signal output end of the main circuit; the negative power supply end of the first circuit of the output stage, namely the negative power supply end of the main circuit.
The positive power end of the output stage second circuit is the positive power end of the main circuit; the control end of the output stage second circuit is the control end of the main circuit.
The positive power supply ends of the expansion circuits are collinear, and the positive power supply ends of the expansion circuits are collinear with the positive power supply ends of the second circuit of the output stage; the control ends of the expansion circuits are collinear and are collinear with the control end of the second circuit of the output stage; the output ends of the expansion circuits are collinear and are collinear with the common output end of the output stage second circuit, so that the output ends of the expansion circuits, the common output end of the output stage second circuit and the common output end of the output stage first circuit form the output end of the main circuit together.
The invention has the positive effects that: (1) The relay protection testing device of the high-precision power amplifier can realize high-voltage and high-power output in use, and when the output direct-current power supply is transmitted to the relay of the equipment to be tested, the relay to be tested receives signals with larger power and higher voltage, so that a real waveform can be obtained when relevant parameters of the relay are tested. (2) The testing device of the high-precision power amplifier can provide reliable and stable direct-current power supply output and has the function of accurately measuring the action voltage of the circuit breaker. The electric power system is tested on site without carrying a high-voltage switch tester, and the testing process is simple and the operation is convenient. (3) The main circuit of the power output stage unit of the high-precision power amplifier adopts the push-pull power output stage circuit and the expansion circuit of the NMOS tube, the push-pull power output stage consists of a push-pull power output stage first circuit and a push-pull power output stage second circuit which are symmetrically arranged, and the push-pull power output stage first circuit and the push-pull power output stage second circuit are connected by the buck diode of the output stage first circuit, so that the power output stage unit works stably when amplifying voltage and power, and the highest output direct current can reach 250V. The expansion circuits are provided with multiple paths, and each path of expansion circuit is connected with the second circuit of the output stage in parallel in a direct coupling mode, so that the output power of the power output stage unit can be increased, and the output power of the power output stage unit can reach 700VA in a single path. (4) The high-precision power amplifier is provided with the constant current source circuit between the power supply end of the power output pole unit and the main circuit, so as to increase the driving capability of the main circuit. And a voltage stabilizing circuit is arranged at the second circuit of the output stage of the power output pole unit, so that static bias voltage can be obtained, and the NMOS power tube is ensured to be in a critical conduction state. The constant current source circuit and the static bias voltage are arranged to cooperate to control the distortion degree.
Drawings
Fig. 1 is a schematic structural diagram of a relay protection testing device provided with a high-precision power amplifier according to the present invention.
Fig. 2 is a circuit block diagram of the relay protection testing apparatus shown in fig. 1.
Fig. 3 is a circuit block diagram of the high precision power amplifier of fig. 2, i.e. the present invention.
Fig. 4 is an electrical schematic diagram of a power output unit of the high-precision power amplifier shown in fig. 3.
Fig. 5 is an electrical schematic diagram of a portion of the circuit of the power output unit of the high-precision power amplifier shown in fig. 4.
Fig. 6 is an electrical schematic diagram of an expansion circuit of the power output unit of the high-precision power amplifier shown in fig. 4.
Fig. 7 is an electrical schematic diagram of the waveform shown in fig. 5.
The labels in the above figures are as follows: the power supply circuit 10, the power supply output control circuit 11, the measurement signal input port 2, the microprocessor 3, the digital-to-analog converter 4, the signal low-pass filter module 5, the high-precision power amplifier 6, the input stage unit 61, the intermediate driving stage unit 62, the power output stage unit 63, the negative feedback link unit 64, the high-voltage switch test port 65, the waveform distortion judging circuit 71, the current signal input end 71-1, the first control signal output end 71-2, the second control signal output end 71-3, the third control signal output end 71-4, the waveform distortion alarm circuit 72, the abnormal signal processing circuit 8, the housing 9, the upper board 91 and the upper computer 100.
Detailed Description
Example 1
Referring to fig. 3, the high-precision power amplifier 6 is provided with a power supply terminal, a signal input terminal, a waveform distortion control signal input terminal, a sampling signal output terminal, and a dc power supply output terminal, and the high-precision power amplifier 6 includes an input stage unit 61, an intermediate driving stage unit 62, a power output stage unit 63, a negative feedback link unit 64, and a high-voltage switch test port 65.
The dc power output end of the high-precision power amplifier 6 is a port which can output a high-power dc power when in use and is connected with the test power input end of the device to be tested.
The input stage unit 61 of the high precision power amplifier 6 is provided with an input and an output. The intermediate drive stage unit 62 is provided with an input and an output. The power output stage unit 63 is provided with a power source terminal, a driving signal input terminal, a waveform distortion control signal input terminal, a sampling signal output terminal, and an output terminal, and the power output stage unit 63 includes a main circuit, a signal input circuit, a voltage stabilizing circuit, a constant current source circuit, and a phototransistor. The high voltage switch test port 65 is provided with an input and an output.
The input terminal of the input stage unit 61 is the signal input terminal of the high-precision power amplifier 6. An output of the input stage unit 61 is electrically connected to an input of the intermediate drive stage unit 62. The output of the intermediate drive stage unit 62 is electrically connected to the drive signal input of the power output stage unit 63. The output of the power output stage unit 63 is also the sampled signal output of the high precision power amplifier 6, and the output of the power output stage unit 63 is electrically connected to the input of the high voltage switch test port 65. The output end of the high-voltage switch test port 65 is the output end of the direct-current power supply of the high-precision power amplifier 6. The output of the power output stage unit 63 is also electrically connected to the input of the negative feedback loop unit 64. The output of the negative feedback loop unit 64 is collinear with the output of the input stage unit 61 and thus also connected to the input of the intermediate drive stage unit 62.
When the high-precision power amplifier 6 works, the input stage unit 61 performs differential processing on the input signal from the signal low-pass filtering module 5, then the signal output by the input stage unit 61 and the feedback signal output by the negative feedback link unit 64 are jointly output to the input end of the intermediate driving stage unit 62, and when the two signals are output under the action of the intermediate driving stage unit 62, a driving voltage is generated for driving the power output stage unit 63. The driving power output stage unit 63 amplifies the voltage and the power under the driving of the driving voltage. The negative feedback loop unit 64 is arranged such that the circuit of the high precision power amplifier 6 forms a closed loop. The high voltage switch test port 65 is capable of outputting relatively stable dc high voltage and high power current, and providing dc voltage and dc current to the device under test.
The input stage unit 61 of the high-precision power amplifier 6 has high input impedance, high stability and strong anti-interference capability. Since the input stage unit 61 employs a differential circuit, the input stage unit 61 can perform differential processing on an input signal when in use.
The intermediate driving stage unit 62 is a composite amplifying circuit composed of operational amplifiers. In operation, the composite amplifying circuit generates a driving voltage matched with the power output stage unit 63 by comparing the signal input by the input stage unit 61 with the feedback signal output by the negative feedback link unit 64.
Referring to fig. 4 to 6, the main circuit of the power output stage unit 63 is provided with a positive power supply terminal, a negative power supply terminal, an input terminal, a half-cycle signal output terminal, a control terminal and an output terminal; the signal input circuit is provided with a half-cycle signal input end and a half-cycle signal output end.
The positive and negative power supply terminals of the main circuit are the power supply terminals of the power output stage unit 63; the input end of the main circuit is the driving signal input end of the power output stage unit 63; the half-cycle signal output end of the main circuit is connected with the half-cycle signal input end of the signal input circuit; the half-cycle signal output end of the signal input circuit is connected with the control end of the main circuit; the output end of the main circuit is the output end of the power output stage unit 63; the cathode direction connecting end of the voltage stabilizing circuit is connected with the control end of the main circuit; the anode direction connecting end of the voltage stabilizing circuit is connected with the output end of the main circuit; the constant current source circuit is arranged between the positive power end and the control end of the main circuit; the collector electrode of the phototriode is connected with the control end of the main circuit; the emitter of the phototriode is connected with the output end of the main circuit; the base electrode of the phototriode is the waveform distortion control signal input end of the power output stage unit drive 63; the connection between the first control signal output terminal 71-2 of the waveform distortion judging circuit 71 and the base of the phototransistor is the connection between the corresponding light emitting diode of the waveform distortion judging circuit 71 and the optical signal emitted from the base of the phototransistor.
The main circuit of the power output stage unit 63 adopts a push-pull power output stage circuit and an expansion circuit of an NMOS tube, the push-pull power output stage consists of a push-pull power output stage first circuit (hereinafter referred to as an output stage first circuit) and a push-pull power output stage second circuit (hereinafter referred to as an output stage second circuit) which are symmetrically arranged, and the push-pull power output stage first circuit and the push-pull power output stage second circuit are connected by a buck diode DA2 of the output stage first circuit, so that the power output stage unit works stably when amplifying voltage and power, and the highest output direct current can reach 250V.
The output stage second circuit is provided with a positive power supply end, a control end and a common output end; the output stage first circuit is provided with an input end, a common output end, a half-cycle signal output end and a negative power supply end; each path of expansion circuit is provided with a positive power end, a control end and an output end. The input end of the first circuit of the output stage is the input end of the main circuit. The common output end of the first circuit of the output stage is connected with the common output end of the second circuit of the output stage. The half-cycle signal output end of the first circuit of the output stage is the half-cycle signal output end of the main circuit. The negative power supply end of the first circuit of the output stage, namely the negative power supply end of the main circuit. The positive power supply end of the output stage second circuit is the positive power supply end of the main circuit. The control end of the output stage second circuit is the control end of the main circuit.
The extension circuits are provided with multiple paths, and each path of extension circuit is connected with the second circuit of the output stage in parallel in a direct coupling way, so that the output power of the power output stage unit 63 can be increased, the output power of the extension circuit can reach 700VA in a single path, and the operation is stable.
A constant current source circuit is provided between the power source terminal of the power output stage unit 63 and the main circuit for increasing the driving capability of the main circuit. A voltage stabilizing circuit is disposed at the output stage second circuit of the power output stage unit 63, so as to obtain a static bias voltage, so as to ensure that the NMOS power tube is in a critical conduction state. The constant current source circuit and the static bias voltage are arranged to cooperate to control the distortion degree.
The power output stage 63 also controls the power through the single power tube strictly by the current sharing technique, and adopts an NMOS parallel current sharing control circuit to control the current in an opposite phase by monitoring the heat of the power tube.
In the case where the output stage second circuit of the power output stage unit 63 and the sets of extension circuits are operated in parallel, whether static or dynamic, if a NMOS transistor shares relatively much current, it will heat up more, which can easily cause damage or cause long-term reliability hazards. The quiescent current distribution imbalance is caused by the unequal on-resistances Rds of the parallel devices, with devices with lower on-resistances Rds sharing more current than the average value. Since the on-resistance Rds of the NMOS transistor has a positive temperature coefficient, the NMOS transistor does not undergo a second breakdown. If a small area inside the NMOS tube absorbs more current, the local heating will be more severe and the internal resistance will increase, transferring part of the current to the adjacent area to balance the current density.
This characteristic is also applicable to parallel NMOS transistors within a certain range, but merely by its own balancing mechanism is not sufficient to reduce the operating temperature of the hotter device. This is because the temperature coefficient of the on-resistance Rds is not very large, requiring a large device temperature difference to divert large unbalanced currents. If the temperature difference is too large, the temperature of the hotter device is high and may have exceeded the normal operating range or even the maximum allowable junction temperature, which is a situation that must be avoided.
This feature works well inside NMOS tubes because all regions inside NMOS tubes have strong thermal coupling, whereas for parallel cases, the individual device housings share a heat sink, even the heat sinks are independent, with very weak thermal coupling. Thus, this characteristic is limited in the contribution that can be made to the balanced operating current.
Referring to fig. 5 and 7, the main circuit of the power output stage unit 63 is composed of a push-pull power output stage circuit and a 7-way expansion circuit. The push-pull power output stage circuit includes an output stage first circuit and an output stage second circuit. The 7-way expansion circuit is arranged in parallel with the output stage second circuit in a direct coupling manner. Each of the expansion circuits shown in fig. 6 sequentially uses NMOS power transistors VB2, VC2, VD2, VE2, VF2, VG2 and VH2 as cores, and the collinear junction between the 7 sets of expansion circuits and the second circuit of the output stage has 3 points, the first point is the drain electrode of each NMOS power transistor, that is, point a in fig. 6 and 7, the second point is the gate electrode of each NMOS power transistor, that is, point B in fig. 6 and 7, and the third point is the output end of the power output stage unit 63, that is, point C at the common junction between each output resistor and the anode of the buck diode DA 2.
Referring to fig. 5 and 7, the output stage second circuit is composed of an NMOS power transistor VA2, a current limiting circuit, and a thermistor TA 20. The current limiting circuit of the second circuit of the output stage is composed of resistors RA28, RA10, RA9, RA20 and a transistor VQA3, and the resistors RA28, RA10, RA9 and RA20 are sequentially connected in series. The base of the transistor VQA is connected to a connection point between the resistor RA28 and the resistor RA20, one end of the resistor RA9 is connected to the emitter of the transistor VQA, the connection point is the output end of the power output stage unit 63, the other end of the resistor RA9 is connected to the source S end of the NMOS power transistor VA2, and the gate G end of the NMOS power transistor VA2 is connected to the collector of the transistor VQA.
Referring to fig. 5 to 7, if the NMOS VA2 of the second circuit of the output stage is more sensitive to temperature changes than the NMOS of the other 7 sets of expansion circuits, the conduction degree of the NMOS further increases with the rise of temperature, and the current passing through the NMOS VA2 in the second circuit of the push-pull power output stage gradually increases more. At the same time, the voltage across RA9 increases. Since the driving voltage VG is constant for the output voltage, the voltage of the source S terminal of the NMOS transistor VA2 is reduced by the power transistor driving voltage VG2 as the voltage across the RA9 increases. The reduced driving voltage of the NMOS transistor VA2 results in a reduced conduction of the power transistor VA2, thereby reducing the current through the NMOS transistor VA 2. The other 7-way expansion circuits are arranged according to the same principle of negative feedback regulation as described above.
For the current limiting circuit of the output stage second circuit, when the current output exceeds the negative feedback regulation range, the current passing through the two ends of the resistor RA9 is too large, and the voltage at the two ends of the resistor RA9 is fed back to the base electrode and the emitter electrode of the triode VQA3, so that the triode VQA3 is conducted, and the voltage of the driving voltage VG to the output is approximately zero. Therefore, the NMOS power tube VA2 is turned off in a short time, and the total current is shared by the rest parallel circuits until the temperature of the NMOS power tube VA2 is reduced to a reasonable position, so that an overcurrent protection effect is achieved.
Referring to fig. 5 and 7, a resistor TA20 of the second circuit of the output stage is a positive temperature coefficient thermistor, and the resistor TA20 is parallel connected with a resistor RA 20. As the circuit temperature increases, the resistance increases, which results in the transistor VQA being turned on, and the NMOS power transistor VA2 is turned off in a short time, thereby providing overheat protection.
Referring to fig. 5 and 7, the constant current source circuit of the power output stage 63 is composed of a MOS transistor VA3, a triode VQA, resistors RA11 and RA12, and is configured to provide bias current, so that the driving capability of the NMOS power transistor VA2 of the main circuit is increased. The drain of the NMOS power transistor VA2 is collinear with one end of the resistor RA11, and is connected to the drain of the power transistor VA2, and is used as the positive power supply end of the power output stage unit 63. The other end of the resistor RA11, the collector of the transistor VQA and the gate of the MOS transistor VA3 are collinear, and the one end of the resistor RA12, the base of the transistor VQA and the source of the MOS transistor VA3 are collinear. The emitter of transistor VQA is collinear with the other end of resistor RA12 and is connected to the gate of power transistor VA 2.
The voltage stabilizing circuit of the power output stage unit 63 is formed by connecting one end of a resistor RA23 with the cathode of a voltage stabilizing diode DWA5, and the anode of the voltage stabilizing diode DWA5 is connected with the output end of the power output stage unit 63, and the other end of the resistor RA23 is connected with the gate of a power tube VA 2. The voltage stabilizing circuit is beneficial to the stable operation of the NMOS power tube VA 2.
The signal input circuit of the power output stage unit 63 is constituted by a unidirectional silicon controlled rectifier DWA2, resistors RA14, RA15, and a positive temperature coefficient thermistor TA 14. One end of the resistor RA14, one end of the thermistor TA14 and the cathode of the unidirectional silicon controlled rectifier are collinear, and are connected with the grid electrode of the power tube VA 2. The other end of the resistor RA14, the other end of the thermistor TA14, and one end of the resistor RA15 are in line with the control electrode of the unidirectional thyristor. The other end of the resistor RA15 and the anode of the unidirectional silicon controlled rectifier are collinear, and are connected with the drain electrode of the NMOS power tube VA1 of the first circuit of the output stage.
The collector of the phototransistor (also called phototriode) U2B of the power output stage unit 63 is connected to the gate of the NMOS power transistor VA2, the emitter of the phototriode U2B is connected to the output end of the power output stage unit 63, and the base of the phototriode U2B is the waveform distortion control signal input end of the power output stage unit 63.
The output stage first circuit consists of an NMOS power tube VA1, a current limiting circuit, a thermistor TA21, a voltage stabilizing circuit and a voltage stabilizing auxiliary circuit. The current limiting circuit of the first circuit of the output stage is composed of resistors RA31, RA8, RA7, RA21 and a transistor VQA, and the resistors RA31, RA8, RA7 and RA21 are sequentially connected in series. The base of the transistor VQA is connected to the junction of the resistors RA31 and RA21, the other end of the resistor RA7 is connected to the emitter of the transistor VQA1, and the junction is the negative supply terminal of the power output stage unit 63. The other end of the resistor RA7 is connected with the source electrode S end of the NMOS power tube VA1, and the gate electrode G end of the NMOS power tube VA1 is connected with the collector electrode of the transistor VQA.
The resistor TA21 of the first circuit of the output stage is a positive temperature coefficient thermistor, and the resistor TA21 is arranged in parallel with the resistor RA 21. As the circuit temperature increases, the resistance increases, which results in the transistor VQA being turned on, and the NMOS power transistor VA1 is turned off in a short time, thereby providing overheat protection.
The voltage stabilizing circuit of the output stage first circuit is formed by one end of a resistor RA22 and the cathode of a voltage stabilizing diode DWA1, the anode of the voltage stabilizing diode DWA1 is connected with the negative power supply end of the power output stage unit 63, the other end of the resistor RA22 is connected with the grid electrode of the power tube VA1, and the arrangement of the circuit is favorable for the stable operation of the NMOS power tube VA 1.
The voltage stabilizing auxiliary circuit of the first circuit of the output stage is a resistor RA6, the resistor RA6 and the voltage stabilizing circuit of the first circuit of the output stage are arranged in parallel, and the arrangement of the circuit is favorable for the stable work of the NMOS power tube VA 1.
In addition to the above-mentioned negative feedback adjustment in the power output stage unit 63, the negative feedback link unit 64 of the high-precision power amplifier 6 forms a closed loop system with the circuit of the high-precision power amplifier 6, and at this time, the gain of the amplifying circuit is only determined by the feedback network, and is almost independent of the basic amplifying circuit, so that the stability of the output is ensured.
Application example 1
Referring to fig. 1 and 2, the relay protection testing device for high output dc voltage of the present application (hereinafter referred to as the present testing device for short) includes a testing box that can be connected to the host computer 100 when in use. The shell 9 of the test box is provided with a liquid crystal display, an alarming light emitting diode and an alarming buzzer, and a main board and a power circuit board are arranged inside the test box.
Referring to fig. 2, the power circuit board is provided with a power circuit 10 and a power output control circuit 11. The power circuit 10 is a circuit for providing main power for the testing device, and the power circuit 10 is provided with a first output end and a second output end for outputting direct current power. The first output terminal of the power supply circuit 10 is electrically connected to one end of a corresponding relay contact J1 of the relay group of the power supply output control circuit 11, and each corresponding other end of the relay contact J1 is the first power supply terminal of the power supply circuit board. The corresponding coil of the power output control circuit 11 belonging to the relay group is powered by a dry battery or a lithium battery, and the power output control circuit 11 is provided with a control terminal for controlling the on-off of the current in the coil.
Still referring to fig. 2, the second output terminal J2 of the power circuit 10 is an output terminal for outputting a positive and negative 600V dc power. The output end is connected with the power end of the high-precision power amplifier 6, and the power circuit 10 provides power for the rest circuits requiring direct current power supply of the relay protection testing device through the first output end. The power supply terminal of the high-precision power amplifier 6 is electrically connected to a second output terminal of the power supply circuit 10.
Referring to fig. 1, the main board is mounted closely to the housing 9 of the test box, and a heat dissipation window is provided on the housing 9 of the test box at a position corresponding to the main board. The bottom plate of the test box housing 9 and the upper plate 91 are provided with honeycomb-shaped heat dissipation holes at the upper and lower parts of the power circuit board, thereby forming heat dissipation channels.
The main board is provided with a measuring signal input port 2, a microprocessor 3 (adopting an ARM9 processor), a digital-to-analog converter 4, a signal low-pass filtering module 5, a waveform distortion judging circuit 71, a waveform distortion alarming circuit 72 and an abnormal signal processing circuit 8, and is also provided with the high-precision power amplifier 6 which is obtained in the embodiment 1 and can output a high-power direct-current power supply.
The input/output port of the microprocessor 3 is provided with a display signal output port, a shutdown control end, a test power supply signal output end, an abnormal signal input end and a plurality of test signal input ends. The high-precision power amplifier 6 is two paths in parallel. The abnormal signal processing circuit 8 is mainly composed of a photoelectric isolation circuit, and is provided with a signal input end and a signal output end.
The measurement signal input port 2 comprises a number of switching value signal inputs and a number of analog signal inputs. The switching value signal input ends are ports which can be connected with the switching value signal output ends of related equipment including the switching value signal output ends of the equipment to be tested in use. The output corresponding to the switching value signal input is thus directly electrically connected to a corresponding one of the test signal inputs of the microprocessor 3.
Each analog signal input terminal of the measurement signal input port 2 is a port that can be connected to an analog signal output terminal of a relevant device including an analog signal output terminal of a device to be measured in use. Therefore, a corresponding signal processing circuit is also provided between the output terminal corresponding to the analog signal input terminal and the test signal input terminal of the microprocessor 3. The signal processing circuit comprises a functional module capable of sampling, filtering and analog-to-digital conversion processing of the analog signal. The analog signal is processed by the signal processing circuit, and then is output to a corresponding connection end of the test signal input end of the microprocessor 3 by the output end of the signal processing circuit.
The display signal output port of the microprocessor 3 is electrically connected with the corresponding port of the liquid crystal display. The shutdown control end of the microprocessor 3 is electrically connected with the control signal input end of the power output control circuit 11. The communication port of the microprocessor 3 is a port which can be connected with the communication port of the host computer 100 by a bidirectional signal in use. In operation, the microprocessor 3 compares the received measurement signals with the data stored in its memory to determine whether the measured signals fall within a normal range. When the test signal checking device works, the microprocessor 3 can also measure the signals from the same test signal input end for a plurality of times, and the deviation between the numerical values of the measurement signals of each time is not more than 20 percent as a standard, so that the measurement signal with larger deviation is eliminated, and the checking function is realized.
The test power supply signal output end of the microprocessor 3 is electrically connected with the digital signal input end of the digital-to-analog converter 4. The analog signal output of the digital-to-analog converter 4 is electrically connected to the input of the signal low-pass filter module 5. The output end of the low-pass filter module 5 is electrically connected with the signal input end of the high-precision power amplifier 6.
Referring to fig. 2, the waveform distortion judging circuit 71 is provided with a current signal input terminal 71-1, a first control signal output terminal 71-2, a second control signal output terminal 71-3, and a third control signal output terminal 71-4. The waveform distortion alarm circuit 72 is provided with a power supply terminal and a control terminal. The waveform distortion alarm circuit 72 includes the aforementioned alarm light emitting diode and alarm buzzer mounted on the housing 9.
The power supply terminal of the power output stage unit 63 is the power supply terminal of the high-precision power amplifier 6. The input stage unit 61 of the high-precision power amplifier 6 receives the small signal from the signal low-pass filtering module 5. The output terminal of the power output stage unit 63 is also a sampling signal output terminal of the high-precision power amplifier 6, which is electrically connected to the current signal input terminal 71-1 of the waveform distortion judging circuit 71. The first control signal output terminal 71-2 of the waveform distortion judging circuit 71 is electrically connected to the waveform distortion control signal input terminal of the power output stage unit 63. The second control signal output terminal 71-3 of the waveform distortion judging circuit 71 is electrically connected to the control terminal of the waveform distortion alarm circuit 72. The third control signal output terminal 71-4 of the waveform distortion judging circuit 71 is electrically connected to the signal input terminal of the abnormal signal processing circuit 8. The signal output terminal of the abnormality signal processing circuit 8 is electrically connected to the abnormality signal input terminal of the microprocessor 3.
After the waveform distortion judging circuit 71 processes the input current signal, if the deviation value of the voltage is greater than 20% of the set value for 1 second, such as oscillation, the waveform distortion of the detected output current is judged, and at this time, the first control signal output terminal 71-2 of the waveform distortion judging circuit 71 sends a light control signal to the waveform distortion control signal input terminal of the power output stage unit 63, so that the NMOS tube VA2 of the power output stage unit 63 is cut off and outputs zero. Meanwhile, the second control signal output end 71-3 of the waveform distortion judging circuit 71 sends a high level control signal to the control end of the waveform distortion alarming circuit 72 to control the alarming light emitting diode and the alarming buzzer to send out audible and visual alarming signals. If the waveform distortion judging circuit 71 detects that the deviation value of the voltage of the inputted signal is greater than 50% of the set value for 1 second, in addition to the light control signal being sent to the waveform distortion control signal input terminal of the power output stage unit 63 at the first control signal output terminal 71-2 thereof, and the high level control signal being sent to the control terminal of the waveform distortion alarm circuit 72 at the second control signal output terminal 71-3 thereof, the third control signal output terminal 71-4 thereof outputs a high level, thereby causing the abnormal signal processing circuit 8 to send a high level signal indicating that the system is running abnormally to the microprocessor 3. After receiving the signal, the microprocessor 3 firstly shuts down the communication with the upper computer 100, and secondly delays for about 1 second to output a high-level control signal to the control end of the power output control circuit 11 at the shutdown control end thereof, so that the relay contact J1 of the relay group is disconnected, and the power supply circuit 10 stops supplying power to related circuits in the whole machine.
The relay protection testing device for the high-output direct-current voltage realizes reliable and stable direct-current high-voltage and high-power output, has the functions of measurement and verification, and has the function of accurately measuring the action voltage of the circuit breaker. Through testing, the invention achieves the highest output DC +250V), the precision is less than two thousandths (national standard 0.5%), the rise time is less than 100uS (national standard 200 uS), the distortion degree is less than two thousandths (national standard 0.5%), and the output power is the high-voltage and high-power output of 700VA (national standard 90 VA).
The relay protection testing device of the application example can provide reliable and stable direct current power supply output and has the function of accurately measuring the action voltage of the circuit breaker. The electric power system is tested on site without carrying a high-voltage switch tester, and the testing process is simple and the operation is convenient.
Claims (2)
1. A high-precision power amplifier (6) of a relay protection testing device, which is provided with a high-voltage switch testing port (65); the method is characterized in that: the high-precision power amplifier (6) is provided with a power supply end, a signal input end and a direct current power supply output end, and further comprises an input stage unit (61), an intermediate driving stage unit (62), a power output stage unit (63) and a negative feedback link unit (64); the input of the input stage unit (61), i.e. the signal input of the high-precision power amplifier (6); an input stage unit (61) is a circuit capable of performing differential processing on an input signal; the intermediate drive stage unit (62) is a circuit capable of generating a drive voltage; the power output stage unit (63) is provided with a power supply end, a driving signal input end and an output end; the power supply end of the power output stage unit (63) is also the power supply end of the high-precision power amplifier (6); the power output stage unit (63) is a circuit that can be driven by a drive voltage and amplifies the voltage and power; the output end of the input stage unit (61) is connected with the driving signal input end of the power output stage unit (63) through the intermediate driving stage unit (62); the output end of the power output stage unit (63) is electrically connected with the input end of the high-voltage switch test port (65), and the output end is also electrically connected with the input end of the negative feedback link unit (64); the output end of the negative feedback link unit (64) and the output end of the input stage unit (61) are simultaneously connected to the input end of the intermediate driving stage unit (62); the output end of the high-voltage switch test port (65) is the direct-current power supply output end of the high-precision power amplifier (6);
the high-precision power amplifier (6) is also provided with a waveform distortion control signal input end and a sampling signal output end; the power output stage unit (63) of the high-precision power amplifier (6) is also provided with a waveform distortion control signal input end which is used as the waveform distortion control signal input end of the high-precision power amplifier (6); the output end of the power output stage unit (63) is also used as a sampling signal output end of the high-precision power amplifier (6);
the power output stage unit (63) comprises a main circuit, a signal input circuit, a voltage stabilizing circuit, a constant current source circuit and a phototriode;
the main circuit of the power output stage unit (63) is provided with a positive power supply end, a negative power supply end, an input end, a half-cycle signal output end, a control end and an output end; the signal input circuit is provided with a half-cycle signal input end and a half-cycle signal output end;
the positive and negative power supply ends of the main circuit are the power supply ends of the power output stage unit (63); the input end of the main circuit is the driving signal input end of the power output stage unit (63); the half-cycle signal output end of the main circuit is connected with the half-cycle signal input end of the signal input circuit; the half-cycle signal output end of the signal input circuit is connected with the control end of the main circuit; the output end of the main circuit is the output end of the power output stage unit (63); the cathode direction connecting end of the voltage stabilizing circuit is connected with the control end of the main circuit; the anode direction connecting end of the voltage stabilizing circuit is connected with the output end of the main circuit; the constant current source circuit is arranged between the positive power end and the control end of the main circuit; the collector electrode of the phototriode is connected with the control end of the main circuit; the emitter of the phototriode is connected with the output end of the main circuit; the base electrode of the phototriode is the waveform distortion control signal input end of the power output stage unit drive (63);
the DC power supply output end of the high-precision power amplifier (6) is a port which can output a high-power DC power supply when in use and is connected with the test power supply input end of the device to be tested.
2. The high precision power amplifier of the relay protection testing device of claim 1, wherein: the main circuit of the power output stage unit (63) consists of a push-pull power output stage circuit and a multipath expansion circuit; the push-pull power output stage circuit comprises an output stage first circuit and an output stage second circuit; each path of expansion circuit is connected with the second circuit of the output stage in parallel in a direct coupling way; the first circuit of the output stage and the second circuit of the output stage are symmetrically arranged;
the output stage second circuit is provided with a positive power supply end, a control end and a common output end; the output stage first circuit is provided with an input end, a common output end, a half-cycle signal output end and a negative power supply end; each path of expansion circuit is provided with a positive power end, a control end and an output end;
the input end of the first circuit of the output stage is the input end of the main circuit; the common output end of the first circuit of the output stage is connected with the common output end of the second circuit of the output stage; the half-cycle signal output end of the first circuit of the output stage is the half-cycle signal output end of the main circuit; the negative power supply end of the first circuit of the output stage is namely the negative power supply end of the main circuit;
the positive power end of the output stage second circuit is the positive power end of the main circuit; the control end of the output stage second circuit is the control end of the main circuit;
the positive power supply ends of all the expansion circuits are collinear and are collinear with the positive power supply end of the second circuit of the output stage; the control ends of the expansion circuits are collinear and are collinear with the control end of the second circuit of the output stage; the output ends of the expansion circuits are collinear and are collinear with the common output end of the output stage second circuit, so that the output ends of the expansion circuits, the common output end of the output stage second circuit and the common output end of the output stage first circuit form the output end of the main circuit together.
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| CN201710472169.0A CN109100551B (en) | 2017-06-21 | 2017-06-21 | High-precision power amplifier of relay protection testing device |
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| CN109100551B true CN109100551B (en) | 2023-08-11 |
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| GB1149239A (en) * | 1965-06-23 | 1969-04-16 | Plessey Co Ltd | Improvements in or relating to multivibrator circuits |
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| CN109100551A (en) | 2018-12-28 |
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