CN107390029B - Device for eliminating reverse electromotive force during inductive load DCR measurement - Google Patents
Device for eliminating reverse electromotive force during inductive load DCR measurement Download PDFInfo
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- CN107390029B CN107390029B CN201710710844.9A CN201710710844A CN107390029B CN 107390029 B CN107390029 B CN 107390029B CN 201710710844 A CN201710710844 A CN 201710710844A CN 107390029 B CN107390029 B CN 107390029B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
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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
- G01R1/36—Overload-protection arrangements or circuits for electric measuring instruments
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Abstract
The invention relates to a device for eliminating reverse electromotive force during measurement of an inductive load DCR, which comprises a signal source, a switch, a range resistor and an inductive load of a measured piece, wherein a protection diode and a PNP transistor are connected in parallel at two ends of the inductive load of the measured piece; the anode and the cathode of the protection diode are respectively connected with a voltage follower; the output end of the voltage follower is sequentially connected with a first comparator and a second comparator; the output end of the second comparator is connected with the MCU. The invention eliminates the reverse electromotive force generated in the inductive load DCR test by adding the discharge channel, thereby not only more effectively eliminating voltage spike pulse and protecting elements such as a switch in a circuit; and more importantly, the protection of the inductive load is realized, and the residual electric energy generated by the inductive load due to the DCR test is eliminated.
Description
Technical Field
The invention relates to the field of electronic circuits and instruments and meters, in particular to a device for eliminating reverse electromotive force during measurement of an inductive load DCR, which is applied to a direct current resistance test of the inductive load and a direct current resistance scanning instrument circuit of the inductive load.
Background
In the inductive load DC resistance measurement process, as shown in figure 1, when the switch is opened, the induced voltage is directly proportional to the change rate of the magnetic field, so the induced voltage caused by the dip of the magnetic field is formed by
It is known that this induced electromotive force is often many times greater than the supply voltage, with the result that at the moment the circuit is opened, the switch contact points often generate sparks or arcs. To protect the components in the circuit, a reverse biased diode is typically connected across the inductive load, eliminating the voltage spike induced by the diode conduction before a high voltage is developed across the inductive load.
Although the method can rapidly eliminate voltage spike pulse and can also meet the effect of the protection switch contact, the method only rapidly cuts down the generated back electromotive force to about the junction voltage of the diode, and then residual electromotive force still exists on the inductive load; as can be seen from fig. 2, it has the following disadvantages: the residual electromotive force can only be slowly attenuated by the distribution parameters of the inductor, the current discharge speed is low, and then the reverse electromotive force on the inductive load can be disappeared after a long time; the inductive load being tested is in a live state for a considerable period of time; the existence of the residual electromotive force has negative influence on the performance of inductive load and has certain potential safety hazard.
Disclosure of Invention
The invention aims to solve the technical problems that: an apparatus for canceling a back electromotive force at the time of measurement of an inductive load DCR is proposed,
the technical scheme adopted by the invention is as follows: the device for eliminating the reverse electromotive force during the measurement of the inductive load DCR comprises a signal source, a switch, a measuring range resistor and an inductive load of a detected piece, wherein a protection diode and a PNP transistor are connected in parallel at two ends of the inductive load of the detected piece; the anode and the cathode of the protection diode are respectively connected with a voltage follower; the output end of the voltage follower is sequentially connected with a first comparator and a second comparator; the output end of the second comparator is connected with the MCU.
Further, the MCU is connected with the upper computer, receives a control instruction sent by the upper computer, and controls the on-off state of the switch to be switched; and simultaneously receiving an input signal of the second comparator, and judging whether residual electromotive force on the inductive load is eliminated or not according to the input signal. The MCU judges the working state of the circuit through the output state of the second comparator; when the output of the second comparator is at a high level, the PNP transistor is turned on, the circuit is in a discharging state, and the residual electromotive force is continuously reduced; when the output of the second comparator is at a low level, the PNP transistor is turned off, the discharge of the circuit is ended, and the residual electromotive force is eliminated.
Still further, the cathode of the protection diode is connected with the first voltage follower; the anode of the protection diode is connected with a second voltage follower; the first voltage follower consists of a first resistor, a first operation method device and a third resistor; the voltage of the non-inverting input end of the first comparator is equal to the potential of the cathode of the protection diode; the second voltage follower consists of a second resistor, a second operational amplifier and a fourth resistor; the voltage at the inverting input terminal of the first comparator is equal to the potential of the anode of the protection diode. The reverse input end of the first comparator is also connected with a fifth resistor; the resistance of the fifth resistor is smaller than one thousandth of the resistance of the fourth resistor.
Still further, the first comparator of the present invention controls on or off of the PNP transistor; when the PNP type transistor is turned on, a power resistor connected with the PNP type transistor is connected to two ends of the residual electromotive force to provide a discharge channel for the residual electromotive force on the inductive load of the detected object.
Still further, the second comparator of the present invention monitors the output state of the first comparator; when the first comparator output is high, the second comparator output is low; when the first comparator output is low, the second comparator output is high.
The beneficial effects of the invention are as follows: the reverse electromotive force generated in the inductive load DCR test is eliminated through adding the discharge channel, so that voltage spike pulse can be eliminated more effectively, and elements such as a switch in a circuit are protected; and more importantly, the protection of the inductive load is realized, and the residual electric energy generated by the inductive load due to the DCR test is eliminated.
Drawings
The invention will be further described with reference to the drawings and examples.
FIG. 1 is a schematic diagram of a prior art inductive load DCR measurement;
FIG. 2 is a diagram of an actual inductance equivalent circuit model;
FIG. 3 is a schematic circuit diagram of the apparatus of the present invention;
FIG. 4 is a schematic diagram of the output voltage of U3 of the present invention;
FIG. 5 is a schematic diagram of the output voltage of U4 according to the present invention.
Detailed Description
The invention will now be described in further detail with reference to the drawings and a preferred embodiment. The drawings are simplified schematic representations which merely illustrate the basic structure of the invention and therefore show only the structures which are relevant to the invention.
As shown in fig. 3, a device for eliminating a back electromotive force during measurement of an inductive load DCR includes a signal source U0, a switch S1, a range resistor Rs, an inductive load L1 of a measured object, a protection diode D1, a voltage follower U2, a high-speed comparator U3, a high-speed comparator U4, a PNP transistor Q1, a power resistor R, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, +15V power supply, -15V power supply, +3.3v power supply, and a micro control unit MCU.
One end of a signal source U0 is connected with one end of a switch S1, the other end of the switch S1 is connected with one end of a measuring range resistor Rs, the other end of the measuring range resistor Rs is connected with one end of an inductive load L1, a cathode of a protection diode D1, one end of a resistor R1 and a collector of a PNP type transistor Q1Q1, the other end of the resistor R1 is connected with an in-phase input end of an operational amplifier U1, an anti-phase input end of the operational amplifier U1 is connected with an output end of the operational amplifier U1 and one end of a resistor R3, the other end of the resistor R3 is connected with an in-phase input end of a comparator U3, a high-speed comparator U3 adopts a dual-power type comparator, a +15V power supply is connected with a positive power supply input end of the high-speed comparator U3, a 15V power supply is connected with a negative power supply input end of the high-speed comparator U3, an anti-phase input end of the high-speed comparator U3 is connected with one end of a resistor R4 and one end of the resistor R5, the other end of the resistor R5 is connected with a-15V power supply, the other end of the resistor R4 is connected to the output end of the operational amplifier U2 and the inverting input end of the operational amplifier U2, the non-inverting input end of the operational amplifier U2 is connected with one end of the resistor R2, the other end of the resistor R2 is connected with the other end of the inductive load L1, the anode of the protection diode, the other end of the signal source U0 and the emitter of the PNP type transistor Q1, the base of the PNP type transistor Q1 is connected with one end of the resistor R7, the other end of the resistor R7 is connected with the output end of the high-speed comparator U3, one end of the resistor R5 and the inverting input end of the high-speed comparator U4, the other end of the resistor R5 is connected with a +15V power supply, the inverting input end of the high-speed comparator U4 is connected with an interrupt pin of the micro control unit MCU, and the other end of the high-speed comparator U4 is connected with a +3.3V power supply.
The MCU is connected with the upper computer, receives a control instruction sent by the upper computer and is responsible for switching on and off states of the switch S1; an input signal from the high speed comparator U4 is received, and it is determined whether the residual electromotive force on the inductive load is eliminated based on the input signal.
The resistor R1, the operational amplifier U1 and the resistor R3 form a voltage follower, so that the voltage of the non-inverting input end of the comparator U3 is equal to the negative electrode potential of the protection diode, namely the negative electrode potential of the reverse electromotive force; the resistor R2 and the operational amplifier U2 form a voltage follower, so that the voltage of the non-inverting input end of the comparator U3 is almost equal to the cathode of the protection diode, namely the positive potential of the reverse electromotive force, and the resistance value of the resistor R5 is far smaller than that of the resistor R4 by at least 1000 times.
The turn-on and turn-off of the PNP type transistor Q1 is controlled by the dual-power comparator U3, when the PNP type transistor Q1 is turned on, the power resistor is connected to two ends of the residual electromotive force to provide a discharging channel for the residual electromotive force on the inductive load L1, and the residual electromotive force on the inductive load L1 is finally eliminated under the action of the comparator U3.
Monitoring the output state of the comparator U3 by the comparator U4; when the comparator U3 output is high level, the comparator U4 output is low level; when the comparator U3 output is low, the comparator U4 output is high. The micro control unit MCU judges the working state of the circuit according to the output state of the comparator U4; when the output of the comparator U4 is high level, the PNP transistor Q1 is conducted, the circuit is in a discharging state, and the residual electromotive force is continuously reduced; when the output of the comparator U4 is at a low level, the PNP transistor Q1 is turned off, the circuit discharge ends, and the residual electromotive force is eliminated.
In situations where the speed requirements are not very high, an operational amplifier may be used instead of a high speed comparator to achieve cost savings. The signal source U0 can be a voltage source or a current source; the inductive load L1 may be grounded or floated during DCR test.
The working principle is as follows: when the switch S1 is opened, an induced electromotive force generated in the inductive load L1, as shown in fig. 3, has the same direction as the current in the circuit when the switch S1 is closed. At this time, the output level of the comparator U4 rises from low level to high level, a rising edge pulse is generated, and the MCU receives the rising edge pulse to indicate that the discharging process starts; next, the output level of the comparator U4 is changed from high level to low level, a falling edge pulse is generated, and the MCU receives the falling edge pulse, which indicates that the discharging process is finished, and the induced electromotive force on the inductive load returns to zero. Thus, residual electric energy and potential safety hazards existing in the inductive load caused by DCR test are eliminated.
The working process is as follows:
when the switch S1 is opened, an induced electromotive force generated in the inductive load L1, as shown in fig. 3, has the same direction as the current in the circuit when the switch S1 is closed.
Let the cathode potential of the protection diode D1 be V1, the anode potential of the protection diode D2 be V2, and the forward turn-on voltage of the protection diode D1 be V PN V is then PN ＝V2-V1.......(1)
Let the residual electromotive force on the inductive load L1 be E after the switch S1 is turned off R ，
Then E R ＝V PN ＝V2-V1......(2)
Let the voltage at the non-inverting input terminal of the comparator U3 be U 3p The voltage at the inverting input of the comparator U3 is U 3n The output voltage of the comparator U3 is U 3O Then there is
U 3p ＝V1......(3)
After the switch S1 is opened, there is V1 < V2, then for comparator U3
Because of U 3p ＜U 3n ，U 3O Output is low level, U 3O The pnp transistor Q1 is turned on, current flows from the emitter to the collector of the transistor Q1, and then returns to the negative side of the residual electromotive force via the power resistor R, discharging the residual electromotive force through the current channel. As long as the residual electromotive force exists, V1 is smaller than V2, the discharge channel exists all the time until the residual electromotive force is completely eliminated, the inductive load does not carry residual electric energy any more, the protection of the inductive load is realized, and potential safety hazards possibly existing are eliminated.
For comparator U3, switch S1 is closed, when V1> V2,
thus U 3p >U 3n Comparator U3 outputs high level, U 3O The pnp transistor Q1 is turned off.
Let the voltage at the non-inverting input terminal of the comparator U4 be U 4p The voltage at the inverting input of the comparator U4 is U 4n The output voltage of the comparator U4 is U 4O Because of U 4n ＝U 3O The non-inverting input of the comparator U4 is grounded, i.e., U 4p =0, then, U 4p ＜U 4n Comparator U4 outputs low level, U 4O =0, indicating that the protection circuit does not affect the DCR measurement process.
The foregoing description is merely illustrative of specific embodiments of the invention, and the invention is not limited to the details shown, since modifications and variations of the foregoing embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (5)
1. The utility model provides a device for eliminating reverse electromotive force when inductive load DCR measures, includes signal source, switch, range resistance and measured piece inductive load, its characterized in that: the two ends of the inductive load of the detected piece are connected with a protection diode and a PNP transistor in parallel; the anode and the cathode of the protection diode are respectively connected with a voltage follower; the output end of the voltage follower is sequentially connected with a first comparator and a second comparator; the output end of the second comparator is connected with the MCU; the first comparator controls the on or off of the PNP transistor; when the PNP type transistor is turned on, a power resistor connected with the PNP type transistor is connected to two ends of residual electromotive force to provide a discharge channel for the residual electromotive force on the inductive load of the detected piece; the second comparator monitors the output state of the first comparator; when the first comparator output is high, the second comparator output is low; when the first comparator output is low, the second comparator output is high.
2. The apparatus for canceling back electromotive force at the time of measurement of an inductive load DCR according to claim 1, wherein: the MCU is connected with the upper computer, receives a control instruction sent by the upper computer, and controls the on-off state of the switch to be switched; and simultaneously receiving an input signal of the second comparator, and judging whether residual electromotive force on the inductive load is eliminated or not according to the input signal.
3. The apparatus for canceling back electromotive force at the time of measurement of an inductive load DCR according to claim 1, wherein: the cathode of the protection diode is connected with a first voltage follower; the anode of the protection diode is connected with a second voltage follower; the first voltage follower consists of a first resistor, a first operation method device and a third resistor; the voltage of the non-inverting input end of the first comparator is equal to the potential of the cathode of the protection diode; the second voltage follower consists of a second resistor, a second operational amplifier and a fourth resistor; the voltage at the inverting input terminal of the first comparator is equal to the potential of the anode of the protection diode.
4. A device for canceling back electromotive force at the time of measurement of an inductive load DCR as claimed in claim 3, wherein: the reverse input end of the first comparator is also connected with a fifth resistor; the resistance of the fifth resistor is smaller than one thousandth of the resistance of the fourth resistor.
5. The apparatus for canceling back electromotive force at the time of measurement of an inductive load DCR according to claim 2, wherein: the MCU judges the working state of the circuit through the output state of the second comparator; when the output of the second comparator is at a high level, the PNP transistor is turned on, the circuit is in a discharging state, and the residual electromotive force is continuously reduced; when the output of the second comparator is at a low level, the PNP transistor is turned off, the discharge of the circuit is ended, and the residual electromotive force is eliminated.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710710844.9A CN107390029B (en) | 2017-08-18 | 2017-08-18 | Device for eliminating reverse electromotive force during inductive load DCR measurement |
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| CN201710710844.9A CN107390029B (en) | 2017-08-18 | 2017-08-18 | Device for eliminating reverse electromotive force during inductive load DCR measurement |
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| CN107390029B true CN107390029B (en) | 2023-06-02 |
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| CN113285436B (en) * | 2021-06-16 | 2025-04-01 | 浙江南晶电气有限公司 | A reverse electromotive force active discharge protection circuit and active arc extinguishing method |
| CN113884203B (en) * | 2021-08-30 | 2023-11-14 | 南通职业大学 | Semiconductor Vacuum Diode Temperature Sensor |
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| JPS6029816A (en) * | 1983-07-28 | 1985-02-15 | Toshiba Corp | Inductive load constant-current driving circuit |
| CN2138795Y (en) * | 1992-08-05 | 1993-07-21 | 杨意逢 | Inductance inner resistance fast measurer |
| JP2009268008A (en) * | 2008-04-30 | 2009-11-12 | Keihin Corp | Drive unit for inductive load |
| CN201974480U (en) * | 2010-12-28 | 2011-09-14 | 武汉国试电气设备有限公司 | Intelligent measuring system for transformer resistance |
| CN103149443A (en) * | 2013-02-26 | 2013-06-12 | 江苏省电力公司徐州供电公司 | Double-range resistance megohm meter |
| CN105939007A (en) * | 2016-06-23 | 2016-09-14 | 国网江苏省电力公司泰州供电公司 | Rapid discharge circuit for measuring DC resistance of transformer |
| CN207148222U (en) * | 2017-08-18 | 2018-03-27 | 常州市计量测试技术研究所 | A kind of device for being used to eliminate inverse electromotive force when inductive load DCR is measured |
-
2017
- 2017-08-18 CN CN201710710844.9A patent/CN107390029B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6029816A (en) * | 1983-07-28 | 1985-02-15 | Toshiba Corp | Inductive load constant-current driving circuit |
| CN2138795Y (en) * | 1992-08-05 | 1993-07-21 | 杨意逢 | Inductance inner resistance fast measurer |
| JP2009268008A (en) * | 2008-04-30 | 2009-11-12 | Keihin Corp | Drive unit for inductive load |
| CN201974480U (en) * | 2010-12-28 | 2011-09-14 | 武汉国试电气设备有限公司 | Intelligent measuring system for transformer resistance |
| CN103149443A (en) * | 2013-02-26 | 2013-06-12 | 江苏省电力公司徐州供电公司 | Double-range resistance megohm meter |
| CN105939007A (en) * | 2016-06-23 | 2016-09-14 | 国网江苏省电力公司泰州供电公司 | Rapid discharge circuit for measuring DC resistance of transformer |
| CN207148222U (en) * | 2017-08-18 | 2018-03-27 | 常州市计量测试技术研究所 | A kind of device for being used to eliminate inverse electromotive force when inductive load DCR is measured |
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