Anti-back electromotive force circuit

Abstract

The utility model provides an anti-counter electromotive force circuit, which comprises a power supply input end, a power supply output end, an anti-counter assembly, a counter electromotive force absorption assembly, an anti-counter state switching assembly, a transient impact energy absorption assembly, a counter electromotive force release assembly and a power supply assembly. And the anti-reverse assembly is used for preventing reverse electromotive force generated by the load from impacting the power supply. The back electromotive force absorption assembly is used for absorbing back electromotive force generated by the load. And the back electromotive force release assembly is used for releasing the back electromotive force in the absorption assembly. The anti-reverse state switching assembly is provided with a public movable contact, a normally-closed contact and a normally-open contact. The public movable contact and the normally-closed contact are connected to the two ends of the anti-reverse state switching assembly respectively. The anti-reverse state switching assembly is in a normally-closed state when not powered on. When the reverse electromotive force does not exist, the transient impact energy absorption assembly buffers the energy of the instantaneous large-energy signal of the anti-reverse assembly, and when the reverse electromotive force does not exist, the transient impact energy absorption assembly releases the buffered energy and converges the energy into the power input, so that the sudden change energy interference in the protection process is effectively inhibited, and meanwhile, the energy is prevented from being wasted.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic technical field, especially relate to a kind of anti-reverse electromotive force circuit. BACKGROUND

[0002] In power electronics applications, motor as typical inductive load, is widely used in industrial automation, household appliances, vehicles and many other fields. However, when the motor decelerates from high-speed running state to stop or suddenly power off, the magnetic field in its internal coil will not disappear immediately, but according to Faraday's law of electromagnetic induction, a high-amplitude reverse electromotive force (Back-EMF) opposite to the power supply direction will be generated at both ends of the coil. This momentary high-voltage and high-current energy, if not properly handled, will be directly fed back to the power supply, posing a serious threat to the power supply system.

[0003] Traditional power supply design often lacks effective protection measures against such reverse electromotive force impact, resulting in overvoltage and overcurrent protection action of the power supply when encountering such situations, and even direct damage to internal electronic components such as rectifier bridge and power switch tube. This not only increases the maintenance cost of the equipment, but also seriously affects the stability and efficiency of the system. In order to solve the above problems, some simple protection schemes have appeared in the market, such as adding pressure-sensitive resistors, transient voltage suppression diodes (TVS) and other passive components to absorb part of the reverse energy. For example, Chinese utility model patent CN218124309U discloses a method for protecting the power supply from the impact of reverse electromotive force by using diodes. However, the diodes are also connected to the circuit for a long time when there is no reverse electromotive force, causing unnecessary energy consumption. When the reverse electromotive force comes, the anode of the diode is impacted by a momentary large energy disturbance signal, which causes interference to the circuit. SUMMARY

[0004] To solve the above problems, the purpose of the utility model is to provide an anti-reverse electromotive force circuit, which short-circuits the anti-reverse component when there is no reverse electromotive force in the circuit, thereby avoiding continuous energy consumption of the anti-reverse component, and suppressing and buffering the momentary large energy disturbance signal when the circuit generates it.

[0005] The utility model realizes the following technical solutions:

[0006] An anti-reverse electromotive force circuit, comprising:

[0007] A power input terminal connected to a power supply;

[0008] A power output terminal for outputting power to supply power to a load;

[0009] a reverse prevention component connected in series between the power input and the power output;

[0010] a back electromotive force absorption component, one end of which is connected between the reverse prevention component and the power output, and the other end of which is grounded;

[0011] a reverse prevention state switching component, having a common movable contact, a normally closed contact and a normally open contact, the common movable contact and the normally closed contact being connected to the two ends of the reverse prevention component respectively;

[0012] a transient impact energy absorption component, the input end of which is connected to the normally open contact, and the output end of which is connected between the power input and the reverse prevention component, for absorbing transient pulse energy of the reverse prevention component and releasing to the power input;

[0013] a back electromotive force release component, one end of which is connected to the common end of the absorption component and the reverse prevention component, and the other end of which is grounded or the transient impact energy absorption component;

[0014] a power supply component, which is arranged between the back electromotive force absorption component and the power output, for generating power for the reverse prevention state switching component when there is a reverse electromotive force in the circuit.

[0015] Further, the reverse prevention component comprises a diode or a unidirectional thyristor, the anode of the diode or the unidirectional thyristor being connected to the power input; the control end of the unidirectional thyristor being connected to the power supply component.

[0016] Further, the reverse prevention state switching component comprises a relay, the relay being a normally closed relay, the common movable contact pin and the normally closed contact pin of the relay being connected to the two ends of the reverse prevention component respectively, the normally open contact pin of the relay being connected to the transient impact energy absorption component; the coil pin of the relay being connected to the power supply component.

[0017] Further, the transient impact energy absorption component comprises an energy storage capacitor and a reverse prevention diode, the anode of the reverse prevention diode and the energy storage capacitor being connected to the normally open contact of the reverse prevention state switching component, the cathode of the reverse prevention diode being connected between the power input and the reverse prevention component.

[0018] Further, the absorption component comprises a first electrolytic capacitor, the positive pole of the first electrolytic capacitor being connected to the reverse prevention component, and the negative pole being grounded.

[0019] Further, the back electromotive force release component comprises a switch element and a fourth resistor, one electrode end of the switch element is connected with two ends of the anti-reverse component respectively, the other electrode end of the switch element is connected with the fourth resistor in series, the other end of the fourth resistor is grounded, and the control end of the switch element is connected with the power input end.

[0020] Further, the back electromotive force release component comprises a switch element, one electrode end and the control end of the switch element are connected with the far end from the ground of the back electromotive force absorption component, and the other electrode end of the switch element is connected with the transient impact energy absorption component.

[0021] Further, the back electromotive force release component comprises a unidirectional thyristor and a fourth resistor, the anode of the unidirectional thyristor is connected with the far end from the ground of the back electromotive force absorption component, and the cathode of the unidirectional thyristor is grounded through the fourth resistor; the back electromotive force release component further comprises a ninth resistor, a voltage stabilizing diode and a sixth electrolytic capacitor connected in series and then connected in parallel between two ends of the back electromotive force absorption component, the common end of the anode of the voltage stabilizing diode and the positive electrode of the sixth electrolytic capacitor is connected with the control end of the unidirectional thyristor, and the negative electrode of the sixth electrolytic capacitor is grounded.

[0022] Further, the power supply component comprises a transformer, the primary coil of the transformer is connected in series between the back electromotive force absorption component and the power output end; one end of the secondary coil of the transformer is connected in series with a fifth diode, the cathode of the fifth diode is the positive output end of the power supply component, the other end of the secondary coil of the transformer is connected in series with a voltage stabilizing diode, the cathode of the voltage stabilizing diode is the negative output end of the power supply component; the anode of the voltage stabilizing diode is grounded; and the positive output end and the negative output end of the power supply component are further connected with an electrolytic capacitor.

[0023] Further, the circuit further comprises a working indication component, the working indication component comprises a current limiting resistor and a light emitting diode connected in series, the cathode of the light emitting diode is grounded, and the other end of the current limiting resistor is connected between the back electromotive force absorption component and the power supply component.

[0024] Compared with the prior art, the technical scheme and beneficial effects of the utility model are as follows:

[0025] (1) The utility model discloses a prevent reverse component for preventing the impact of reverse electromotive force generated by load on power supply, and the reverse electromotive force generated by load is absorbed by the absorption component, and the release component releases the reverse electromotive force in the absorption component, thereby playing a good protection role on the power supply. At the same time, when no reverse electromotive force or the reverse electromotive force is less than the power supply output voltage appears in the circuit, the prevent reverse component is short-circuited to reduce the energy consumption of the prevent reverse component. At the same time, the transient impact energy absorption component stores energy for the transient large energy signal of the prevent reverse component, and when no reverse electromotive force is restored, the transient impact energy absorption component releases the stored energy into the power supply input, so that the sudden energy interference of the protection process is effectively inhibited, and the part of energy is avoided to be wasted.

[0026] (2) The release component of the utility model realizes the release of reverse electromotive force through the voltage difference between the base and the emitter of the triode, and simultaneously directly indicates the release process through the light emitting diode.

[0027] (3) The power supply component of the utility model generates the power supply of the prevent reverse state switching component through the induction of reverse electromotive force, and the design is ingenious, and the working state of the prevent reverse state switching component is accurately controlled. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a kind of principle diagram of prevent reverse electromotive force circuit provided by the utility model embodiment one;

[0029] Figure 2 It is a kind of principle diagram of prevent reverse electromotive force circuit provided by the utility model embodiment two;

[0030] Figure 3 It is a kind of principle diagram of prevent reverse electromotive force circuit provided by the utility model embodiment three.

[0031] ILLUSTRATIVE DESCRIPTION

[0032] Power supply input end-10;Power supply output end-20;Prevent reverse component-30;Reverse electromotive force absorption component-40;Reverse electromotive force release component-50;Prevent reverse state switching component-60;Power supply component-70;Working indication component-80;Transient impact energy absorption component-90. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. It should be understood that the specific embodiments described herein are only used to explain the utility model, and are not used to limit the utility model. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the utility model.

[0034] Embodiment one

[0035] Referring to Figure 1 A reverse electromotive force circuit, comprising a power input end 10, a power output end 20, a reverse prevention component 30, a reverse electromotive force absorption component 40, a reverse electromotive force release component 50, a reverse prevention state switching component 60, a power supply component 70 and a transient impact energy absorption component 90. The power input end 10 is connected with a power supply, and the power output end 20 is the final output end of the power supply and supplies power to a load (not shown). The reverse prevention component 30 is connected in series between the power input end 10 and the power output end 20, and is used to prevent the reverse electromotive force generated by the load from impacting the power supply. One end of the absorption component 40 is connected between the reverse prevention component 30 and the power output end 20, and the other end is grounded, and is used to absorb the reverse electromotive force generated by the load.

[0036] The reverse prevention state switching component 60 has a common movable contact, a normally closed contact and a normally open contact. The common movable contact and the normally closed contact of the reverse prevention state switching component 60 are connected to the two ends of the reverse prevention component 30, and the normally open contact of the reverse prevention state switching component 60 is connected with the transient impact energy absorption component 90. When the reverse prevention state switching component 60 is not powered, it is in a normally closed state. The power supply component 70 is connected in series between the reverse electromotive force absorption component 40 and the power output end 20, and is used to supply power to the reverse prevention state switching component 60 when there is a reverse electromotive force in the circuit. That is, when the load does not generate a reverse electromotive force, the power supply component 70 does not supply power to the reverse prevention state switching component 60, and the reverse prevention state switching component 60 works in a normally closed state, thereby forming a short circuit between the two ends of the reverse prevention component 30, and avoiding the waste of energy consumption caused by the reverse prevention component 30 being connected to the circuit when the power supply is working normally for a long time (without being impacted by a reverse electromotive force). When the load generates a large reverse electromotive force, the power supply component 70 supplies power to the reverse prevention state switching component 60, and the reverse prevention state switching component 60 switches to the normally open contact, so that the end of the reverse prevention component close to the power input end 10 is connected to the transient impact energy absorption component 90, and is used to absorb transient impact energy.

[0037] With reference to the foregoing Figure 1 , in this embodiment, the reverse prevention component 30 comprises a diode D1, the anode of which is connected to the power input terminal 10. The reverse electromotive force absorption component 40 comprises an electrolytic capacitor C1, the positive pole of which is connected to the cathode of the diode D1, and the negative pole of which is grounded. The reverse electromotive force release component 50 comprises a switching element Q1 and a resistor R4, the switching element Q1 being a PNP triode, the emitter of which is connected to both ends of the diode D1, the collector of which is connected to the ground through the resistor R4, and the base of which is connected to the power input terminal 10. In this embodiment, the reverse electromotive force release component 50 further comprises a current-limiting resistor R5 and a light-emitting diode D3 connected in series with the collector of the switching element Q1, and the cathode of the light-emitting diode D3 is grounded. The working indication component comprises a resistor R2 and a light-emitting diode D2 connected in series and in parallel across the electrolytic capacitor C1, and the cathode of the light-emitting diode D2 is grounded.

[0038] When no reverse electromotive force is generated, or the reverse electromotive force is less than the output voltage of the power supply, the voltage at the anode of the diode D1 is always greater than that at the cathode, the diode D1 is forward conducting, the electrolytic capacitor C1 functions as an energy storage filter, and the light-emitting diode D2 connected in parallel across the electrolytic capacitor C1 is lit, indicating that the power supply is working normally. At this time, since the potential at point A is greater than that at point C, the EB electrode of the switching element Q1 is not conducting, i.e. the triode Q1 is cut off, so the light-emitting diode D3 is not lit.

[0039] When the reverse electromotive force exceeds the output voltage but does not exceed the reverse withstand voltage of the diode D1, the voltage at the anode B of the diode D1 is less than that at the cathode C at this time. At this time, due to the presence of the diode D1, the reverse voltage will not reach the Vin+ of the power supply input terminal to cause a reverse impact on the power supply product. Since in the normal case, the voltage across the electrolytic capacitor C1 is almost the voltage at the power supply input terminal, when the reverse electromotive force arrives, the energy electromotive force stored in the electrolytic capacitor C1 is less than the reverse electromotive force, so the reverse electromotive force charges the electrolytic capacitor C1 and is partially absorbed by the electrolytic capacitor C1. When the voltage difference between the voltage at the electrolytic capacitor C1 and the voltage at point A is greater than the V BE on voltage of the switching element Q1, the energy of the electrolytic capacitor C1 greater than the voltage at the power supply input terminal will be released to the ground through the I EC on voltage of the switching element Q1, the energy of the electrolytic capacitor C1 greater than the voltage at the power supply input terminal will be released to the ground through the I BE on voltage of the switching element Q1, the energy of the electrolytic capacitor C1 greater than the voltage at the power supply input terminal will be released to the ground through the I

[0040] With reference to the foregoing Figure 1 , the anti-reverse state switching component 60 includes a relay KA, which is a normally closed relay. The common moving contact pin and the normally closed contact pin of the relay KA are connected to the two ends of the diode D1. The coil pin of the relay KA is connected to the power supply component. When there is no reverse electromotive force in the power supply circuit, the power supply component does not generate power, and the relay KA remains in the normally closed state, thereby short-circuiting the diode D1 and avoiding energy consumption of the diode D1 during long-term normal operation of the power supply.

[0041] The transient impact energy absorption component 90 includes an energy storage capacitor C4 and an anti-reverse diode D4. The anode of the anti-reverse diode D4 and the energy storage capacitor C4 are connected to the normally open contact. The cathode of the anti-reverse diode D4 is connected between the power input end and the diode D1. When there is a reverse electromotive force in the power supply circuit, the power supply component 70 generates power, and the relay KA switches to the normally open contact conduction. When there is a reverse electromotive force in the power supply circuit, i.e., when the diode D1 is in the protection state, the anode B point of the diode D1 will also be momentarily impacted due to the cathode voltage being greater than the anode, causing the energy to be momentarily transferred to the cathode. This impact is a transient large energy interference signal, which will be absorbed and temporarily stored by the energy storage capacitor C4 (at this time, the relay has been actuated, and the relay switch has been switched to the normally open contact). When there is no reverse electromotive force, the relay KA returns to the normally closed contact conduction. At this time, the energy temporarily stored on the energy storage capacitor C4 is again conducted to the Vin+ output branch through the anti-reverse diode D4, effectively suppressing the sudden energy interference of the protection process, while avoiding the waste of this part of the energy.

[0042] The power supply component 70 includes a transformer T2. The primary coil T2-1 of the transformer is connected in series between the current-limiting resistor R2 and the power output end 20. One end of the secondary coil T2-2 of the transformer is connected in series with the diode D5. The cathode of the diode D5 is the positive output end Vstart+ of the power supply component 70. The other end of the secondary coil T2-2 of the transformer is connected in series with the voltage stabilizing diode TVS. The cathode of the voltage stabilizing diode TVS is the negative output end Vstart- of the power supply component 70. The anode of the voltage stabilizing diode TVS is grounded. The positive output end Vstart+ and the negative output end Vstart- of the power supply component are also connected with the electrolytic capacitor C3.

[0043] When the direction electromotive force is greater than the power output voltage, the secondary coil T2-2 of the transformer will induce a reverse voltage on the primary coil T2-1 of the transformer to generate a power supply voltage, which drives the relay KA to actuate. When the reverse electromotive force reaches the protection threshold, the secondary coil T2-2 induces an electromotive force voltage on the primary coil T2-1 that reaches the voltage required for the relay KA to switch and actuate. By selecting the transient voltage suppression diode TVS, the protection threshold of the circuit is set.

[0044] The circuit is also provided with an energy storage component, which includes an electrolytic capacitor C5, the positive pole of the electrolytic capacitor C5 is arranged between the current-limiting resistor R2 and the transformer T2, and the negative pole of the electrolytic capacitor C5 is grounded. The electrolytic capacitor C5 can enhance the delay of the reverse charging voltage to reach the moving contact of the relay KA to switch from the normally closed contact to the normally open contact, so that the diode D1 is normally connected to the circuit.

[0045] Embodiment Two

[0046] Referring to Figure 2 The embodiment has the same principle as Embodiment One, and the difference lies in the structure of the anti-reverse component 30 and the reverse electromotive force release component 50.

[0047] In the embodiment, the anti-reverse component 30 is a unidirectional thyristor Q1, the anode of the unidirectional thyristor Q1 is connected to the power input end 10, the cathode of the unidirectional thyristor Q1 is connected to the positive pole of the capacitor C1, and the control end of the unidirectional thyristor Q1 is connected to the power supply component 70. The power supply component 70 also includes a resistor R7 connected to the cathode of the diode D5, i.e., the positive pole output end Vstart+ of the power supply component 70, the other end of the resistor R7 is connected to the control end of the unidirectional thyristor Q1, and the end of the resistor R7 away from the unidirectional thyristor Q1 is also connected to a voltage stabilizing diode ZD1. The voltage stabilizing diode ZD1 can stabilize the positive pole output end Vstart+ of the power supply component 70 and the voltage of the control end of the unidirectional thyristor Q1.

[0048] In the embodiment, the reverse electromotive force release component 50 includes a switching element Q2, which is an NPN type triode. The collector of the switching element Q2 is connected to the end of the electrolytic capacitor C1 away from the ground after being connected in series with a resistor R8 and a resistor R9 connected in series with the base of the switching element Q2. The emitter of the switching element Q2 is connected to the anode of the anti-reverse diode D4. When the reverse electromotive force arrives, the stored electromotive force on the electrolytic capacitor C1 is smaller than the reverse electromotive force, so the reverse electromotive force charges the electrolytic capacitor C1 and is partially absorbed by the electrolytic capacitor C1. The switching tube Q2 is turned on to start releasing the electrical energy on the electrolytic capacitor C1 until the voltage Vsave+ and the voltage Vin released by the reverse electromotive force release component 50 tend to be the same, at which time the reverse electromotive force energy is released into the capacitor C4 and completed.

[0049] The reverse electromotive force release component 50 also includes a light-emitting diode D3 connected in parallel between the base and the emitter of the switching tube Q2. When the switching tube Q2 is turned on to release the reverse electromotive force, the light-emitting diode D3 will also change from bright to dark to complete extinction due to the potential difference between the voltage Vsave+ and the voltage Vin, thereby playing a release indication role.

[0050] Embodiment Three

[0051] Referring to Figure 3The embodiment is same as the principle of the embodiment two, and the difference is that the structure of the back electromotive force release component 50 is different.

[0052] In the embodiment, the back electromotive force release component 50 comprises a unidirectional thyristor Q2 and a fourth resistor R4, the anode of the unidirectional thyristor Q2 is connected with the far-from-ground end of the electrolytic capacitor C1, and the cathode of the unidirectional thyristor Q2 is grounded through the fourth resistor R4. The back electromotive force release component 50 further comprises a resistor R9, a voltage stabilizing diode ZD2 and an electrolytic capacitor C6 which are connected in series and then connected in parallel between the two ends of the electrolytic capacitor C1, the anode of the voltage stabilizing diode ZD2 and the positive electrode of the electrolytic capacitor C6 are connected with the control end of the unidirectional thyristor Q2, and the cathode of the electrolytic capacitor C6 is grounded.

[0053] When the back electromotive force in the electrolytic capacitor C1 is greater than the voltage parameter of the voltage stabilizing diode ZD2, the voltage stabilizing diode ZD2 is turned on to charge the electrolytic capacitor C6, the electrolytic capacitor C6 gives a starting current signal to the control end of the unidirectional thyristor Q2, so that the AK end of the unidirectional thyristor Q2 can be turned on, and then the electromotive force energy stored in C1 is released to GND through the unidirectional thyristor Q2 and the resistor R4. The resistor R4 is connected in parallel with a light emitting diode D3, and the light emitting diode D3 performs brightness indication from bright to dark due to the change of the shunt current from large to small during the release starting to ending process. The voltage parameter of the voltage stabilizing diode ZD2 is same as the input voltage.

[0054] The above description shows and describes the preferred embodiments of the utility model, and it should be understood that the utility model is not limited to the forms disclosed in the text, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed by the above teaching or related technical or knowledge within the scope of the utility model concept in the text. The changes and variations made by the person skilled in the art do not deviate from the spirit and scope of the utility model, and should be within the protection scope of the claims attached to the utility model.

Claims

1. A back EMF prevention circuit, characterized by, The application relates to a power supply device, which comprises the following components: a power input end connected with a power supply; a power output end for outputting power supply to a load; an anti-reverse component connected in series between the power input end and the power output end; a back electromotive force absorption component, one end of which is connected between the anti-reverse component and the power output end, and the other end of which is grounded; an anti-reverse state switching component, which has a common movable contact, a normally closed contact and a normally open contact, the common movable contact and the normally closed contact being connected to the two ends of the anti-reverse component respectively; the anti-reverse state switching component is in a normally closed state when not powered; a transient impact energy absorption component, the input end of which is connected with the normally open contact, and the output end of which is connected between the power input end and the anti-reverse component, for absorbing transient pulse energy of the anti-reverse component and releasing the transient pulse energy to the power input end; a back electromotive force release component, one end of which is connected to the common end of the absorption component and the anti-reverse component, and the other end of which is grounded or connected with the transient impact energy absorption component; a power supply component, which is arranged between the back electromotive force absorption component and the power output end, for generating power supply to the anti-reverse state switching component when there is a back electromotive force in the circuit.

2. A back EMF prevention circuit according to claim 1, wherein, The anti-reverse component comprises a diode or a unidirectional thyristor, the anode of the diode or the unidirectional thyristor being connected with the power input end; the control end of the unidirectional thyristor being connected with the power supply component.

3. A back EMF prevention circuit as defined in claim 1, wherein The anti-reverse state switching component comprises a relay, the relay being a normally closed relay, the common movable contact pin and the normally closed contact pin of the relay being connected to the two ends of the anti-reverse component respectively, the normally open contact pin of the relay being connected with the transient impact energy absorption component; the coil pin of the relay being connected with the power supply component.

4. A back EMF prevention circuit as defined in claim 1, wherein The transient impact energy absorption component comprises an energy storage capacitor and an anti-reverse diode, the anode of the anti-reverse diode and the energy storage capacitor being connected with the normally open contact of the anti-reverse state switching component, and the cathode of the anti-reverse diode being connected between the power input end and the anti-reverse component.

5. A back EMF prevention circuit as defined in claim 1, wherein, The back electromotive force absorption component comprises a first electrolytic capacitor, the positive pole of the first electrolytic capacitor being connected with the anti-reverse component, and the negative pole of the first electrolytic capacitor being grounded.

6. A back EMF prevention circuit as defined in claim 1, wherein, The back electromotive force release component comprises a switch and a fourth resistor, one electrode end of the switch being connected with the two ends of the anti-reverse component respectively, the other electrode end of the switch being connected with the fourth resistor in series, the other end of the fourth resistor being grounded, and the control end of the switch being connected with the power input end.

7. A back EMF prevention circuit as defined in claim 1, wherein, The back electromotive force release component comprises a switch, one electrode end and the control end of the switch being connected with the end of the back electromotive force absorption component far from the ground, and the other electrode end of the switch being connected with the transient impact energy absorption component.

8. A back EMF prevention circuit as defined in claim 1, wherein, The back electromotive force release component comprises a unidirectional thyristor and a fourth resistor, the anode of the unidirectional thyristor being connected with the end of the back electromotive force absorption component far from the ground, and the cathode of the unidirectional thyristor being grounded through the fourth resistor. The back electromotive force release component further comprises a ninth resistor, a voltage stabilizing diode and a sixth electrolytic capacitor connected in series across the back electromotive force absorption component; the anode of the voltage stabilizing diode and the positive pole of the sixth electrolytic capacitor are connected to the control end of the unidirectional thyristor; and the negative pole of the sixth electrolytic capacitor is grounded.

9. A back EMF prevention circuit as defined in claim 1, wherein, The power supply component comprises a transformer, a primary coil of the transformer being connected in series between the back electromotive force absorption component and the power output end; one end of a secondary coil of the transformer is connected in series with a fifth diode, the cathode of the fifth diode being the positive output end of the power supply component; the other end of the secondary coil of the transformer is connected in series with a voltage stabilizing diode, the cathode of the voltage stabilizing diode being the negative output end of the power supply component; the anode of the voltage stabilizing diode is grounded; and an electrolytic capacitor is further connected between the positive output end and the negative output end of the power supply component.

10. A back EMF prevention circuit as defined in claim 1, wherein, The working indication component comprises a current-limiting resistor and a light-emitting diode connected in series, the cathode of the light-emitting diode being grounded, and the other end of the current-limiting resistor being connected between the back electromotive force absorption component and the power supply component.

Images