TWI711263B - Inductive load drive circuit - Google Patents

Abstract

[Question] To provide an inductive load drive circuit that does not generate heat, can reduce the current when the inductive load stops, realizes high responsiveness, and can perform current control with higher response and efficiency than before. [Solution] In an inductive load drive circuit with a switching power supply circuit, when the current of the inductive load decreases, the energy recovery circuit that generates the back electromotive force of the inductive load while recovering is formed to include: A recovery transformer having two primary coils connected in series and opposite polarity to the inductive load with different resistance values, and a secondary coil connected to the primary side of the switching transformer; and among the two primary coils The relatively small resistance primary side coil is arranged in series and operates according to the pulse signal obtained by the second pulse signal generator according to the recovery command signal from the control circuit to control the current flowing to the small resistance primary side coil For the recovery control element, the control circuit adjusts the pulse width of the pulse signal obtained by the second pulse signal generating device relative to the recovery control element when the current of the inductive load decreases, and the recovery control element is turned off for a certain period of time, thereby While generating the back electromotive force of the inductive load, a current flows through the large-resistance primary coil of the recovery transformer with a large relative resistance value, thereby changing the magnetic flux of the iron core to transfer energy to the corresponding secondary coil.

Description

Inductive load drive circuit

[0001] The present invention relates to a circuit used to drive an inductive load such as a solenoid (solenoid) or a motor, and more specifically, it relates to a combined energy recovery circuit that forms a switching power supply circuit obtained by a PWM control method to conduct current Controlled inductive load drive circuit.

[0002] Inductive loads such as motors and electromagnetic coils that have coil components and convert electrical energy into mechanical motion through electromagnetic force are used as actuators in various devices. The driving control methods of inductive loads are roughly divided into: pulse width modulation, so-called PWM (pulse width modulation) control and proportional control. The former is when the duty ratio of the pulse width (duty ratio), that is, the ON/OFF ratio is changed according to the magnitude of the input signal when the load is ON/OFF control, the latter is controlled by connecting the load in series The voltage at both ends of the element is variable and its loss is controlled. [0003] In the PWM method, for example, there is a circuit configuration using a switching power supply as seen in Patent Document 1. By forming a commercial high AC voltage into a low DC voltage and stably supplying the drive circuit to an inductive load, current control is performed By. [0004] Specifically, as shown in FIG. 5(a), the basic structure is shown as an inductive load driving circuit 100 using a switching power supply circuit. The AC from the power supply 112 is first performed by a bridge diode 113. The rectified and smoothed direct current with a smoothing capacitor 114 is converted into a pulsed alternating current by switching the switching element 115 made of a semiconductor element such as FET (Field Effect Transistor) according to the command signal 121 , Is sent to the switching transformer 116, and the AC voltage is stepped down and converted into a predetermined AC voltage. [0005] If current control is performed in the inductive load drive circuit 100, when the input side DC is converted to AC on the primary side of the switching transformer 116, the control circuit will use the command signal 121 to achieve a predetermined pulse width (switching For example, a pulse signal generating device 124 such as a PWM controller (PWM-IC) generates a pulse signal. Then, the pulse width can be adjusted to switch by feedback control based on the detection result obtained by the command signal and the current sensor 125 on the output side. Therefore, even if the power supply and load fluctuate, the output current remains constant. Stabilized DC. [0006] In this method, a switching transformer 116 is used, and the energy on the primary side is formed into a high-frequency alternating current by turning the switching element 115 ON/OFF, electromagnetically induced from the primary side coil Lp to the secondary side coil. Ls transfers energy, but because it is formed as a high-frequency alternating current, the transformer itself is small, and because it generates less heat, it becomes highly efficient. The AC current transmitted as shown above is rectified by the rectifier diode 117 on the secondary side and flows into the inductive load 111, but the induced current rectified by the diode becomes an intermittent waveform, so if it flows directly to the inductive load Load, the voltage across the inductive load will vary greatly. Therefore, in order to smooth it, a smoothing capacitor 118 is arranged on the secondary side, and the smoothed direct current is output to the inductive load 111.　　[0007] The smaller the capacity of the smoothing capacitor 118 on the secondary side, the faster the circuit response. Conversely, since the capacitor cannot be smoothed completely and the ripple voltage becomes larger, the stability of the current control will deteriorate. Therefore, the PWM cycle is made faster, and even if the capacitor capacity is small, the ripple current can be absorbed, thereby achieving high response. However, the response when the inductive load current is OFF is structurally slow as shown below.　　[0008] That is, when the inductive load current is turned off, the switching element 115 on the primary side of the switching transformer must be turned off constant, stop the induction on the secondary side of the transformer, and discharge the smoothing capacitor 118 completely. However, if the capacity of the smoothing capacitor is sufficiently small relative to the back electromotive force generated by the load, if the smoothing capacitor is discharged, as shown in Figure 5(b), the shunt current 101 of the inductive load is at the same time that the smoothing capacitor 118 is reversely charged. The shunt current also flows through the rectifier diode to the secondary winding Ls of the transformer. At this time, in the primary coil Lp, compared with the commutation time of the inductive load, it is a negligible time, but the induced current 102 flows through the built-in diode of the FET. In addition, the impedance of the secondary winding of the transformer is also low, so the commutation current when the inductive load is OFF almost flows through the rectifier diode. As a result, the responsiveness is equivalent to a driving circuit with a diode commutation circuit, which consumes response time.　　[0009] As described above, in the inductive load drive circuit configured with a circuit for switching the power supply of the PWM method, although the efficiency is excellent, there is a problem with the responsiveness, and it is impossible to control the reduction speed of the inductive load current. On the other hand, the proportional control method is to control the voltage by variably adjusting the voltage at both ends of the control element to lose it, and therefore there is a problem of heat generation. [Prior Art Document] [Patent Document] 　　[0010] 　　[Patent Document 1] Japanese Patent Laid-Open No. 2012-217238 　　[Patent Document 2] Japanese Patent Laid-Open No. 07-59397

(Problem to be solved by the invention) 　　[0011] On the other hand, if it is a general electromagnetic coil with a power of 100W or less and a small output, the energy stored in the load is consumed by heat, but the energy consumed is as little as a few watts Therefore, it is not appropriate as the cost-effectiveness of power recovery, so energy recovery is not performed. This is the same in motor drive devices. In low-output systems, the regenerative energy is consumed due to heat. In the current situation where there is no electromagnetic coil with large power, energy recovery is not necessary. Therefore, a drive circuit with a mechanism for it has not been constructed substantially. [0012] However, if a load of a generally used power supply of DC48V or higher is necessary for the driving voltage, the load power increases and when the current of the inductive load is reduced, a surge voltage occurs, and the energy is consumed by heat. There is a waste of money. In addition, any driving method must have an AC-DC power supply or a DC-DC (boost) power supply, and the circuit scale becomes larger.　　[0013] Among them, for example, as shown in Patent Document 2, in the inductive load driving device, there are also those equipped with a means for recovering the commutation energy so as to ensure a good reduction in the load current when the inductive load stops. In Patent Document 2, when the inductive load is not driven, the secondary winding of the transformer is placed in the return path that returns the load current, and switching means is provided to short-circuit the secondary winding or the primary winding. When stopping, turn off the switch means. As a result, a high voltage is generated in the secondary winding in a direction in which the load current is converged, the load current is reduced, and the energy generated in the primary side of the transformer and stored in the inductive load is regenerated in the power supply.　　[0014] However, even if the current flows to the secondary side of the transformer when the inductive load is turned off, the voltage change is only once, so energy cannot be effectively restored to the primary side. Even if the switching means connected in parallel to the secondary winding is turned on/off, the current circuit of the transformer winding is not interrupted. Therefore, the coil current of the secondary transformer cannot be interrupted instantaneously, and the energy consumption of the inductive load is insufficient , So the responsiveness of the inductive load is insufficient. [0015] In view of the above-mentioned problems, the purpose of the present invention is to provide a method that does not generate heat even when the inductive load is large, and can reduce the current when the inductive load is stopped to achieve high responsiveness. An inductive load drive circuit with higher response and more efficient current control than before. (Means for Solving the Problem) 　　[0016] In order to achieve the above object, the inductive load drive circuit of the invention described in claim 1 has: a switching power supply circuit and a control circuit, 　　 the switching power supply circuit is provided with: A rectifier bridge diode for rectification; a primary-side smoothing capacitor that smoothes the rectified DC; and the DC that is smoothed by the aforementioned primary-side smoothing capacitor is based on the pulse signal from the pulse signal generating means The periodic ON/OFF switching of the switching element is converted into a pulse wave of the AC, which is transformed into a preset AC voltage and transmitted to the switching transformer on the secondary side; the AC that is transmitted to the secondary side is rectified. Secondary side diode; and a secondary side smoothing capacitor that smoothes the rectified DC and outputs it. 　　 The control circuit is based on the command signal and the detection result on the output side of the switching power supply circuit, and adjusts the pulse signal The pulse width of the pulse signal obtained by the generator is used to control the ON/OFF switching of the aforementioned switching element. 　　The inductive load drive circuit is: 　　In addition, it has: an energy recovery circuit, which makes the inductive load current when the current decreases. The back electromotive force of the inductive load is recovered while it is generated, and the aforementioned energy recovery circuit includes: 　　 in the same iron core, there are two primary side coils connected in series and opposite polarity to the inductive load with different resistance values, and a primary coil connected to the switching transformer A transformer for recovery of a secondary coil on the secondary side; and a primary side coil with a relatively small resistance value among the two primary coils, arranged in series with the secondary coil based on the recovery command signal from the control circuit. The pulse signal generated by the pulse signal generator operates to control the recovery control element of the current flowing to the primary side coil of the aforementioned low resistance. 　　 The aforementioned control circuit makes the recovery control element relative to the aforementioned recovery control element when the current of the inductive load decreases. By adjusting the pulse width of the pulse signal obtained by the second pulse signal generating device, the recovery control element is turned off for a certain period of time, thereby generating the back electromotive force of the inductive load while increasing the relative resistance of the recovery transformer. Current flows through the primary coil of the resistor, thereby changing the magnetic flux of the iron core and transferring energy to the corresponding secondary coil. [0017] The inductive load drive circuit of the invention described in claim 2 is in the inductive load drive circuit described in claim 1, 　　 is additionally provided with a second recovery control element, which is the same as the aforementioned large resistance of the recovery transformer The side coils are arranged in series to limit the current flowing to the high-resistance primary-side coil so that the voltage when the recovery control element of the small-resistance primary-side coil is turned off becomes constant. (Effects of the Invention) 　　[0018] The inductive load drive circuit of the present invention is configured to switch the power supply circuit and additionally includes an energy recovery circuit obtained by a recovery transformer connected in series with the primary coil and the inductive load, thereby enabling When the current of the inductive load insulated from the power supply side decreases, the back electromotive force of the inductive load is generated and recovered well. Therefore, there is no heat loss and high response when the inductive load current stops is efficiently realized. In particular, the primary side of the recovery transformer is formed to form an energy recovery circuit with two coils of opposite polarities, a large resistance and a small resistance. In a steady state, it is non-inductive and prevents current rise when the load current increases. At the same time, the speed is slow, and the current of the small-resistance primary coil is controlled by the recovery control element controlled by the PWM drive. This allows high-speed control of the load current reduction rate when the inductive load stops, so it has a more efficient It also has the effect of high-response current control of inductive loads.

[0020] The inductive load driving circuit in the present invention has: a switching power supply circuit and a control circuit. The switching power supply circuit is provided with: a rectifier bridge diode that rectifies the AC from the power source; and the rectified DC A smoothed primary side smoothing capacitor; the direct current smoothed by the aforementioned primary side smoothing capacitor is converted into a pulse wave by ON/OFF switching of the switching element according to the period of the pulse signal from the pulse signal generating means The AC, which transforms into a preset AC voltage and transmits it to the secondary side switching transformer; the secondary side diode that rectifies the AC transmitted to the secondary side; and smoothes the rectified DC As for the secondary side smoothing capacitor for output, the control circuit adjusts the pulse width of the pulse signal obtained by the pulse signal generator according to the command signal and the detection result of the output side of the switching power circuit to control the switching element The ON/OFF switching of the inductive load is additionally equipped with: an energy recovery circuit, which recovers the back electromotive force of the inductive load when the current of the inductive load decreases. [0021] With the above constitution, the present invention uses an energy recovery circuit, when the current of the inductive load is reduced, the back electromotive force of the inductive load can be recovered well without the heat caused by consumption. , To achieve high responsiveness when the inductive load stops. [0022] That is, the energy recovery circuit of the present invention includes two primary side coils connected in series with opposite polarities to the aforementioned inductive load in the same iron core, and the primary side of the switching transformer connected to the primary side. A transformer for the recovery of a secondary side coil; and the primary side coil with a relatively small resistance value among the two primary side coils is arranged in series with the second pulse according to the recovery command signal from the control circuit The pulse signal obtained by the signal generating device operates to control the recovery control element of the current flowing to the primary side coil of the small resistance. The control circuit makes the recovery control element relative to the recovery control element when the current of the inductive load decreases. 2. Adjust the pulse width of the pulse signal obtained by the pulse signal generator, and turn off the aforementioned recovery control element for a certain period of time, thereby generating the back electromotive force of the aforementioned inductive load and resisting the large resistance of the aforementioned recovery transformer. The primary side coil flows current, thereby changing the magnetic flux of the iron core to transfer energy to the corresponding secondary side coil.　　[0023] In the above energy recovery circuit, the small-resistance primary side coil can be reduced to a negligible resistance loss. When the current to the inductive load is constant, based on the balance of the coil resistance, the current almost flows to the low-resistance primary coil to excite the transformer/iron core, but if compared to the inductance of the low-resistance primary coil, the current increases When the speed is high, the current flows to the reverse-wound high-resistance primary coil without induction, preventing the current response from being slow. [0024] Next, if the reduction speed of the inductive load current is increased, the recovery control element is turned OFF for a certain period of time, whereby all the current is going to flow to the high resistance primary coil, so high resistance occurs at both ends of the high resistance primary coil. The voltage changes the excitation of the transformer/iron core, so the induced current flows through the secondary coil of the recovery transformer to recover energy. At this time, the reduction speed of the inductive load current can be controlled at high speed by changing the duty ratio of the recovery control element that is PWM-driven by the control circuit. [0025] In addition, in the present invention, a second recovery control element arranged in series with the large resistance primary coil of the recovery transformer is additionally provided, and the recovery control element of the low resistance primary coil can be turned off. The voltage becomes a constant way to limit the current flowing to the aforementioned high-resistance primary coil. As a result, the current is reduced, and even if the voltage across the primary coil with large resistance decreases, the reduction in the amount of transmission to the secondary coil is suppressed, and the inductive load current can be reduced due to the loss of the second recovery control element. Increased speed. [Embodiment] 　　[0026] A schematic configuration diagram of an inductive load driving circuit according to an embodiment of the present invention is shown in FIG. 1. The inductive load driving circuit 1 of this embodiment includes a switching power supply circuit 10 as a basic structure. That is, it is provided with: a bridge diode 13 that rectifies the alternating current from the power supply 12; a primary side smoothing capacitor 14 that smoothes the rectified direct current; and a direct current that is smoothed by the primary side smoothing capacitor 14 , With an AC switching element (FET) 15 that converts the pulse wave by ON/OFF switching according to the cycle of the pulse signal generated by the pulse signal generator 24 in the control circuit 20; the pulse wave is exchanged by the primary coil LP transforms the secondary side coil LS into a preset voltage for transmission; the secondary side rectifier diode 17 rectifies the alternating current transmitted to the secondary side; and further changes the rectified direct current The smoothing is sent to the secondary side smoothing capacitor 18 of the inductive load (electromagnetic coil) 11. [0027] In addition, a current sensor 25 is arranged on the output side of the switching power supply circuit 10. In the control circuit 20, current feedback is performed based on the detection result obtained by the command signal 21 and the current sensor 25 control.　　[0028] Next, in the present embodiment, the switching power supply circuit 10 having the above configuration is additionally provided with an energy recovery circuit 30 that recovers the back electromotive force when the solenoid current decreases. The energy recovery circuit 30 is provided with a recovery transformer 31 connected in series to the electromagnetic coil 11 on the primary side, and the primary side coil is PWM controlled so that energy is transmitted to the secondary side. [0029] Specifically, the recovery transformer 31 is connected to the electromagnetic coil 11 in series with opposite polarities on the same iron core, and has a large-resistance primary coil LP1 with a large relative resistance value and a small-resistance primary coil with a small relative resistance value. Two primary side coils of LP2; and a secondary side coil RLS for recovery connected to the primary side of the switching transformer 16. Next, it is equipped with: arranging in series with the small-resistance primary coil LP2 among the two primary coils and operating in accordance with the pulse signal obtained by the second pulse signal generating device 33 according to the recovery command signal from the control circuit 20, The recovery control element 32 to control the current flowing to the low-resistance primary side coil LP2. [0030] In the energy recovery circuit 30, since the large-resistance primary coil LP1 and the low-resistance primary coil LP2 have opposite polarities, when the current increases, the large-resistance primary coil LP1 and the low-resistance primary coil LP2 Excited without induction, to prevent the slow rise of the solenoid current. [0031] In addition, in this embodiment, when the current of the electromagnetic coil 11 decreases, the control circuit 20 uses the second pulse signal generating device 33 opposite to the recovery control element 32 to change the pulse width of the pulse signal to control the recovery The element 32 performs OFF control for a certain period of time, thereby generating a counter electromotive force of the electromagnetic coil 11 while flowing a current through the high-resistance primary coil LP1, thereby changing the core magnetic flux and transferring energy to the recovery secondary coil RLS. [0032] Accompanying this, since all the current is going to flow to the high-resistance primary coil LP1, a high voltage is generated across the high-resistance primary coil LP1, and the transformer/iron core excitation is changed, so on the secondary side for recovery The induction current flows through the coil RLS, and the energy is recovered. At this time, the reduction speed of the solenoid current can be controlled at a high speed by changing the duty ratio of the recovery control element 32 that is PWM drive-controlled.　　[0033] The results of the comparison test with the inductive load drive circuit without the energy recovery circuit 30 to confirm the effect obtained by the energy recovery circuit 30 are shown here. In this comparative test, the inductive load drive circuit 100 constructed by the conventional switching power supply circuit shown in FIG. 5(a) is used as a control. The structure of the inductive load drive circuit 100 is combined with the structure of the energy recovery circuit 30. In the inductive load drive circuit 1 shown in Fig. 1, the reduction of the solenoid current when the solenoid is stopped is measured, and the reduction characteristics are compared. The results are shown in the graph in Figure 2. [0034] FIG. 2 is on the horizontal axis as the time axis, the current from the electromagnetic coil is set to 0 (msec) when the electromagnetic coil is in a constant state (when the current supply is stopped), and the current value (A) with the passage of time Those shown on the vertical axis. [0035] It can be clearly seen from FIG. 2 that the change curve X of the current value in the case of the inductive load drive circuit without the energy recovery circuit 30 and the electromotive force recovery of the electromagnetic coil as a control, in the case of the energy recovery circuit 30 In the change curve Y of the current value in the inductive load drive circuit 1 of FIG. 1 that recovers the electromotive force of the electromagnetic coil, the reduction (decrease) speed of the electromagnetic coil current is large, and its responsiveness is very high. [0036] In addition, the recovered power when the solenoid current is reduced in the recovery of the back electromotive force measured in FIG. 2 is measured over time, with respect to time: the horizontal axis (msec), and the recovered power (W) is taken on the vertical axis. , The change curve Z is shown in the graph of Figure 3. It can be seen from FIG. 3 that the recovered power system increases rapidly immediately after the electromagnetic coil current decreases, and the recovery of the electromotive force by the energy recovery circuit 30 contributes to a high response when the electromagnetic coil current decreases.　　[0037] Wherein, in the energy recovery circuit 30 of FIG. 1, if the recovery of the back electromotive force progresses and the current becomes smaller, the voltage across both ends of the large-resistance primary coil LP1 decreases, and the recovery also decreases. Therefore, based on the configuration of the energy recovery circuit 30 shown in FIG. 1, as shown in FIG. 4, it is formed to additionally include a second recovery control element (FET) 41 arranged in series with the large resistance primary coil LP1. The structure of the energy recovery circuit 40 can solve this problem. [0038] That is, in the energy recovery circuit 40, the voltage when the recovery control element 32 of the low-resistance primary side coil LP2 is turned off can be constant, and the second recovery control element 41 can restrict the flow to the high-resistance primary The current of the side coil LP1, therefore, even if the voltage across the both ends of the high-resistance primary side coil LP1 decreases, the reduction in the amount of transmission to the secondary side coil RLS for recovery can be suppressed, and the loss due to the second recovery control element 41 , Can achieve the speed of reduction of electromagnetic coil current.

[0039]1, 100‧‧‧Inductive load drive circuit 10‧‧‧Switching power supply circuit 11,111‧‧‧Electromagnetic coil (inductive load) 12,112‧‧‧Power supply 13,113‧‧‧Bridge diode Body 14, 114‧‧‧Smoothing capacitor (primary side) 15, 115‧‧‧Switching element 16,116‧‧‧Switching transformer LP, Lp‧‧‧ Primary side coil LS, Ls‧‧‧Secondary side coil 17, 35、117‧‧‧Rectifier diode 18,118‧‧‧Smoothing capacitor (secondary side) 20‧‧‧Control circuit 21,121‧‧‧Command signal 24,124‧‧‧Pulse signal generating device 25,125 ‧‧‧Current sensor 30, 40‧‧‧Energy recovery circuit 31‧‧‧Recovery transformer LP1‧‧‧High resistance primary coil LP2‧‧‧Small resistance primary coil RLS‧‧‧Recovery secondary side Coil 32‧‧‧Recovery control element 33‧‧‧Second pulse signal generator 41‧‧‧Second recovery control element

[0019] "Figure 1" is a schematic configuration diagram of an inductive load drive circuit according to an embodiment of the present invention.　　 Figure 2 is a graph showing the reduction characteristics of the electromagnetic coil in the presence or absence of an energy recovery circuit (horizontal axis: time [msec], vertical axis: current [A]).　　 Figure 3 is a graph showing the power recovery characteristics during energy recovery in Figure 2 (horizontal axis: time [msec], vertical axis: recovered power [W] and solenoid current [A]).　　 Figure 4 is a partial circuit diagram showing the improvement of the energy recovery circuit of Figure 1.　　 Figure 5 is a schematic configuration diagram showing an example of a conventional inductive load driving circuit with a switching power supply circuit, (a) is a current control circuit diagram, (b) is a partial circuit diagram showing the operation when the inductive load current is OFF.

1.‧‧Inductive load drive circuit

10‧‧‧Switching power circuit

11‧‧‧Electromagnetic coil (inductive load)

12‧‧‧Power supply

13‧‧‧Bridge Diode

14‧‧‧Smoothing capacitor (primary side)

15‧‧‧Switching element

16‧‧‧Switching transformer

17, 35‧‧‧rectifier diode

18‧‧‧Smoothing capacitor (secondary side)

20‧‧‧Control circuit

21‧‧‧Command signal

24‧‧‧Pulse signal generator

25‧‧‧Current Sensor

30‧‧‧Energy recovery circuit

31‧‧‧Recycling transformer

32‧‧‧Recycling control components

33‧‧‧The second pulse signal generator

LP‧‧‧ Primary side coil

LS‧‧‧Secondary coil

LP1‧‧‧Large resistance primary coil

LP2‧‧‧Small resistance primary coil

RLS‧‧‧Secondary coil for recycling

Claims (2)

An inductive load drive circuit, which has: a switching power supply circuit and a control circuit. The switching power supply circuit is provided with: a rectifier bridge diode that rectifies AC from the power source; a primary circuit that smoothes the rectified DC Side smoothing capacitor: The direct current smoothed by the aforementioned primary side smoothing capacitor is converted into a pulse wave AC by switching on/off the switching element according to the period of the pulse signal from the pulse signal generator, A switching transformer that transforms the voltage into a preset AC voltage and transmits it to the secondary side; a secondary side diode that rectifies the AC that is transmitted to the secondary side; and smoothes the rectified DC to output Secondary side smoothing capacitor. The control circuit adjusts the pulse width of the pulse signal obtained by the pulse signal generator according to the command signal and the detection result of the output side of the switching power supply circuit to control the ON/OFF of the switching element Switch, the inductive load driving circuit is characterized by: in addition, it has: an energy recovery circuit, which recovers the back electromotive force of the inductive load when the current of the inductive load decreases, and the aforementioned energy recovery circuit includes: The iron core has a recovery transformer with two primary side coils connected in series and opposite polarity to the aforementioned inductive load with different resistance values, and a secondary side coil connected to the primary side of the aforementioned switching transformer; and It is arranged in series with the primary side coil with a relatively small resistance value among the two primary side coils and operates according to the pulse signal obtained by the second pulse signal generating device according to the recovery command signal from the above-mentioned control circuit to control The recovery control element of the current flowing to the primary side coil of the small resistance, the control circuit makes the pulse width of the pulse signal obtained by the second pulse signal generating device of the recovery control element when the current of the inductive load decreases Adjust to turn off the recovery control element for a certain period of time, so as to generate the back electromotive force of the inductive load while flowing current through the large resistance primary coil of the recovery transformer with a large relative resistance value, thereby making the core magnetic flux Change so that the energy is transmitted to the corresponding secondary side coil. For example, the inductive load driving circuit of the first item of the patent application, wherein the energy recovery circuit is additionally equipped with: a second recovery control element, which is arranged in series with the large resistance primary coil of the recovery transformer; and a constant voltage A diode is inserted on the gate side of the second recovery control element. If the recovery control element of the low resistance primary side coil is turned off, the current flowing to the primary side coil decreases and the high resistance primary side coil When the generated voltage is lower than the sum of the gate threshold voltage of the second recovery control element and the voltage of the constant voltage diode, the drain-source voltage of the second recovery control element is increased to reduce The aforementioned second recovery control element The voltage of the sum of the drain-source voltage and the voltage of the high-resistance primary side coil is constant, and the drain-source voltage of the second recovery control element and the voltage of the high-resistance primary coil The sum is controlled so as not to become the voltage below the sum of the gate threshold voltage of the second recovery control element and the voltage of the constant voltage diode.

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