JP6262835B1 - Inductive load drive circuit - Google Patents

Abstract

The present invention provides an inductive load driving circuit capable of controlling the rate of decrease in load current with higher responsiveness when the inductive load is stopped than before and capable of satisfactorily suppressing loss due to heat generation. An alternating current from a power source is converted into a direct current that is smoothed through a rectifier bridge diode and a primary side smoothing capacitor, and the direct current is generated by a switching element that is switching-controlled according to a pulse signal from a pulse signal generator. In an inductive load drive circuit having a switching power supply circuit that transmits as alternating current to a secondary side by a switching transformer and outputs as smoothed direct current through a secondary side diode and a secondary side capacitor, from the switching power supply circuit to the inductive load It further includes a proportional control element that controls the output current according to the command signal, and the control circuit controls the pulse signal generator to switch the switching pulse of the switching element so that the voltage across the proportional control element becomes constant. The width was adjusted. [Selection] Figure 1

Description

  The present invention relates to a circuit for driving an inductive load such as a solenoid or a motor, and more particularly to an inductive load driving circuit in which a proportional control method is combined with a circuit configuration of a switching power supply based on a PWM control method.

  Inductive loads such as motors and solenoids that have coil components and convert electrical energy into mechanical motion via electromagnetic force are used as actuators in various devices. Inductive load drive control systems are broadly divided into pulse width modulation, so-called PWM (pulse width modulation) control and proportional control. In the former, the duty ratio of the pulse width, that is, the on / off ratio is changed according to the magnitude of the input signal when the load is turned on / off, and the latter is applied to both ends of the control element connected in series with the load. Control is performed by varying the voltage and causing loss.

  As a PWM system, for example, a circuit configuration of a switching power supply as shown in Patent Document 1 is used, and current control is performed by a drive circuit that stably supplies a commercial high AC voltage as a low DC voltage to an inductive load. is there.

  Specifically, as shown in FIG. 7A, the alternating current from the power supply 112 is first rectified by the bridge diode 113, and then the direct current smoothed by the smoothing capacitor 114 is based on the command signal 121. Switching is performed by switching the switching element 115 made of a semiconductor element such as an FET (Field Effect Transistor) into a pulse wave alternating current by switching and then sending it to the switching transformer 116 to step down the alternating voltage to a predetermined alternating voltage. This is an inductive load driving circuit 100 using a power supply circuit.

  When the input side direct current is converted into the alternating current on the primary side of the switching transformer 116, for example, a PWM controller (on-time of switching on / off cycle) is set based on the command signal 121 in the control circuit. A pulse signal is generated from a pulse signal generator 124 such as PWM-IC. Since the pulse wave width can be adjusted and switched by feedback control based on the command signal and the detection result by the current sensor 125 on the output side, the output current can be kept constant even when the power source and the load fluctuate, and the stabilized DC Is obtained.

  In this method, energy is transmitted by causing the switching transformer 116 to switch on / off the switching element 115 and electromagnetically inducting a current that is a high frequency alternating current from the primary side coil Lp to the secondary side coil Ls. By using alternating current, the transformer itself can be small, and heat generation is low, resulting in high efficiency. The alternating current thus transmitted is rectified by the rectifier diode 117 on the secondary side and passed to the inductive load. However, since the induced current rectified by the diode has an intermittent waveform, the inductive load is passed directly to the inductive load. The voltage at both ends of fluctuates greatly. Therefore, in order to smooth this, a smoothing capacitor 118 is disposed on the secondary side, and the smoothed direct current is output to the inductive load 111.

  The smoothing capacitor 118 on the secondary side has a faster circuit response as the capacitance is smaller. On the other hand, since the capacitor cannot be completely smoothed and the ripple voltage increases, the stability of current control is deteriorated. Therefore, it is possible to increase the response by making the PWM cycle faster and absorbing the ripple current even if the capacitor capacity is small, but the response when the inductive load current is off is structural as follows: It will be slow.

  That is, in order to turn off the inductive load current, it is necessary to stop the induction to the transformer secondary side by setting the switching element 115 on the primary side of the switching transformer to be constant OFF and to discharge the smoothing capacitor 118 completely. However, when the capacity of the smoothing capacitor is sufficiently smaller than the counter electromotive force generated by the load, when the smoothing capacitor is discharged, the commutation current 101 of the inductive load reverses the smoothing capacitor 118 as shown in FIG. At the same time as charging in the direction, a commutation current also flows through the rectifier diode in the transformer secondary coil Ls. At this time, the induced current 102 also flows to the primary side coil Lp via the internal diode of the FET, although the time is negligible compared to the commutation time of the inductive load. Further, since the impedance of the transformer secondary side coil is also low, most of the commutation current when the inductive load is off flows through the rectifier diode. As a result, the response is equivalent to a drive circuit having a diode commutation circuit, and a response time is required.

  As described above, the inductive load drive circuit using the circuit configuration of the PWM type switching power supply is excellent in efficiency, but has a problem in responsiveness and cannot control the rate of decrease of the inductive load current. On the other hand, the proportional control method has a problem that heat is generated because it is controlled by variably adjusting the voltage at both ends of the control element to cause loss.

JP 2012-217238 A Japanese Patent Application Laid-Open No. 07-59397

  On the other hand, in the case of a normal solenoid or the like with a small output of power of 100 W or less, the energy stored in the load is consumed due to heat generation, but the energy consumed is only a few watts, so the cost effectiveness of collecting power is low. Because it is not suitable, energy recovery is not performed. The same applies to the motor drive device. In a low output system, regenerative energy is consumed by heat generation. Since there is no need for energy recovery in the current situation where there is no high power solenoid, a drive circuit having a mechanism for this purpose has not been substantially constructed.

  However, in the case of a load that requires a power supply of DC 48V or higher, which is generally used for driving voltage, the load power becomes large, and when the current of the inductive load is reduced, a surge voltage is generated, and the energy is generated by heat generation. There is waste to consume. Further, any driving method requires an AC-DC power supply or a DC-DC (step-up) power supply, which increases the circuit scale.

  For example, as in Patent Document 2, some inductive load driving devices include means for recovering commutation energy so that a good fall of the load current can be secured when the inductive load is stopped. In Patent Document 2, a secondary winding of a transformer is disposed in a return path for returning a load current when an inductive load is not driven, and a switch means for short-circuiting the secondary winding or the primary winding is provided. The switch means is turned off when the load is stopped. As a result, a high voltage is generated in the direction in which the load current converges on the secondary winding, the load current is lowered, a current is generated on the primary side of the transformer, and the energy accumulated in the inductive load is regenerated to the power source. Yes. However, even if a current is passed through the transformer secondary side when the inductive load is turned off, the voltage changes only once, so that the energy cannot be effectively returned to the primary side. Even if the switch means connected in parallel to the secondary winding is turned on / off, the current circuit of the transformer winding is not cut off, so the coil current of the secondary transformer cannot be cut off instantaneously and induction Since the energy consumption of the load is insufficient, the responsiveness of the inductive load is insufficient.

  In view of the above problems, an object of the present invention is to provide an inductive load drive circuit that can control the rate of decrease in load current with higher responsiveness when the inductive load is stopped than before and can suppress the loss due to heat generation well. There is to do.

In order to achieve the above object, an inductive load driving circuit according to claim 1 includes a rectifying bridge diode that rectifies alternating current from a power source, a primary-side smoothing capacitor that smoothes rectified direct current, and the primary The direct current smoothed by the side smoothing capacitor is converted to a pulse wave alternating current by switching the switching element on / off in a cycle based on the pulse signal from the pulse signal generator to a predetermined alternating voltage. And a switching transformer that transmits to the secondary side, a secondary side diode that rectifies the alternating current transmitted to the secondary side, and a secondary side smoothing capacitor that further smoothes and outputs the rectified direct current A pulse generated by the pulse signal generator based on the power supply circuit, the command signal, and the detection result on the output side of the switching power supply circuit; In inductive load drive circuit having a control circuit, a to adjust the degree in pulse width to control the on / off switching of the switching element,
A proportional control element for controlling a current output from the switching power supply circuit to the inductive load according to a command signal;
The control circuit controls the pulse signal generator to adjust the switching pulse width of the switching element so that the voltage across the proportional control element is constant.

An inductive load driving circuit according to a second aspect of the present invention is the inductive load driving circuit according to the first aspect, wherein the inductive load driving circuit recovers the back electromotive force of the inductive load while commutating when the current of the inductive load decreases. A circuit,
The energy recovery circuit includes a recovery transformer having a recovery primary coil connected in parallel to the inductive load and a recovery secondary coil connected to a primary side of the switching transformer, and the control circuit. A second pulse signal generator for generating a pulse signal based on the recovery command signal, and being arranged in series with the primary coil for recovery and operating in response to the pulse signal from the second pulse signal generator A recovery control element that controls a current flowing through the recovery primary coil, and a commutation that is connected to the primary side of the recovery transformer and that the back electromotive force of the inductive load is commutated when the recovery control element is off. A circuit, and
The control circuit adjusts a pulse width of a pulse signal by the second pulse signal generator with respect to the recovery control element when the current of the inductive load is reduced, and controls switching of the recovery control element, thereby controlling the recovery control element. Energy is transmitted to the secondary coil for recovery while the back electromotive force of the inductive load is commutated to the primary coil for recovery of the transformer for recovery.

  An inductive load drive circuit according to a third aspect of the present invention is the inductive load drive circuit according to the second aspect, wherein the commutation circuit of the energy recovery circuit is configured to perform the induction when the recovery control element is turned off. A storage capacitor is provided for accumulating a commutation current of a load and discharging a charge accumulated when the recovery control element is turned on again to supply a current to the primary coil for recovery.

An inductive load drive circuit according to a fourth aspect of the present invention is the inductive load drive circuit according to the second aspect, wherein the energy recovery circuit is the commutation circuit and the recovery control element connected to the recovery control element. A second recovery primary coil having a relatively large resistance value provided on the same iron core of the recovery transformer with a polarity opposite to that of the primary coil;
The control circuit adjusts the pulse width of the pulse signal generated by the second pulse signal generator with respect to the recovery control element when the current of the inductive load is reduced, and controls the recovery control element to be off for a certain time. By passing a current through the second recovery primary coil while commutating the back electromotive force of the inductive load, the core magnetic flux is changed to transmit energy to the recovery secondary coil.

  An inductive load drive circuit according to a fifth aspect of the present invention is the inductive load drive circuit according to the fourth aspect, wherein the energy recovery circuit is disposed in series with the second primary coil for recovery, and The second recovery control element for limiting the current flowing through the second recovery primary coil so that the voltage when the recovery control element of the recovery primary coil having a small resistance value is turned off is constant. Is further provided.

  According to the inductive load driving circuit of the present invention, a proportional control element that controls a direct current output from the switching power supply circuit to the inductive load according to a command signal is provided, and the control circuit has a constant voltage across the proportional control element. Since the control of the pulse signal generator is performed so as to adjust the switching pulse width of the switching element so as to become, it becomes possible to control the rate of decrease of the inductive load current, which has not been possible in the past, together with the control of the rate of increase, By controlling the voltage to be constant at both ends of the proportional control element, there is an effect that a high response is realized and at the same time heat loss is prevented.

1 is a schematic configuration diagram of an inductive load driving circuit according to a first embodiment of the present invention. It is a schematic block diagram of the inductive load drive circuit by the 2nd Example of this invention. 3 is an operation waveform diagram of each part at the time of load current commutation in the energy recovery circuit of FIG. 2, (a) is a voltage of a storage capacitor, (b) is a current of a primary coil for recovery, and (c) is a recovery control element. The on / off interval, (d), shows the variation of the current control deviation. It is a schematic block diagram of the inductive load drive circuit by the 3rd Example of this invention. It is a partial circuit diagram which shows the energy recovery circuit in the inductive load drive circuit of FIG. FIG. 6 is a partial circuit diagram showing an improved version of the energy recovery circuit of FIG. 5. It is a schematic block diagram which shows the example of the conventional inductive load drive circuit which has a switching power supply circuit, (a) is a current control circuit diagram, (b) is a partial circuit diagram which shows the operation | movement at the time of inductive load current OFF.

  An inductive load driving circuit according to the present invention includes a rectifier bridge diode that rectifies an alternating current from a power source, a primary side smoothing capacitor that smoothes the rectified direct current, and a pulse signal that generates a direct current smoothed by the primary side smoothing capacitor. A switching transformer for transforming a pulse wave converted to alternating current by on / off switching of the switching element in a cycle based on a pulse signal from the device into a predetermined alternating voltage and transmitting the same to the secondary side; A switching power supply circuit comprising a secondary side diode for rectifying the alternating current transmitted to the secondary side, and a secondary side smoothing capacitor for further smoothing and outputting the rectified direct current, a command signal, and an output of the switching power supply circuit And adjusting the pulse width of the pulse signal by the pulse signal generator based on the detection result on the side A control circuit that controls on / off switching of the switching element, and further includes a proportional control element that controls a current output from the switching power supply circuit to the inductive load according to a command signal, The pulse signal generator is controlled to adjust the switching pulse width of the switching element so that the voltage across the proportional control element is constant.

  With the above configuration, in the present invention, the DC current rectified and smoothed on the secondary side of the switching power supply circuit and sent to the inductive load is current-controlled by the proportional control element based on the command signal from the control circuit. Therefore, it is possible to control the rate of decrease of the inductive load current, which could not be performed conventionally, together with the control of the ascending rate. In addition, since the voltage is controlled to be constant at both ends of the proportional control element, a high response is realized and heat loss is also prevented.

  When the inductive load is large, it is conceivable that when the inductive load is stopped, the proportional control element generates heat that cannot be ignored due to the consumption of counter electromotive force when the current decreases. Therefore, in the present invention, it is possible to prevent such heat generation by further including an energy recovery circuit that recovers the back electromotive force of the inductive load while commutating it.

  As the energy recovery circuit, a configuration in which a recovery transformer that is PWM controlled is provided in parallel to the inductive load is preferable. That is, a recovery transformer having a recovery primary coil connected in parallel to the inductive load and a recovery secondary coil connected to the primary side of the switching transformer in the same iron core is provided. A recovery control element that operates in accordance with the pulse signal generated from the second pulse signal generator based on the recovery command signal and controls the current flowing through the recovery primary coil is connected in series to the recovery primary coil. And a commutation circuit connected to a primary side of the recovery transformer and configured to commutate a back electromotive force of the inductive load when the recovery control element is turned off.

  In this energy recovery circuit, the control circuit controls the switching of the recovery control element by adjusting the pulse width of the pulse signal by the second pulse signal generator when the current decreases when the inductive load is stopped. Energy is transmitted to the secondary coil for recovery while the back electromotive force of the inductive load is commutated to the primary coil for recovery of the transformer. Accordingly, the back electromotive force is recovered to the primary side of the switching transformer, so that heat generation due to consumption by the proportional control element is avoided.

  As the commutation circuit for commutating the counter electromotive force of the inductive load when the recovery control element is off, it is preferable that a storage capacitor is disposed. This storage capacitor accumulates commutation current while the recovery control element is off, and discharges this accumulated charge and supplies it to the recovery primary coil when the recovery control element is turned on again. Therefore, the storage capacitor serves as a current supply source to the recovery primary coil together with the commutation current from the inductive load, and energy recovery is performed more efficiently.

  Further, as another energy recovery circuit, instead of the commutation circuit having the above storage capacitor, a recovery transformer having two recovery primary coils is provided by arranging a second recovery primary coil. The provided structure is also suitable. Specifically, a second recovery primary coil having a polarity opposite to that of the first recovery primary coil connected to the recovery control element and having a relatively large resistance value is provided on the same iron core of the recovery transformer. It is provided.

  In this energy recovery circuit, the control circuit adjusts the pulse width of the pulse signal by the second pulse signal generator when the current of the inductive load is decreased, and controls the recovery control element to be off for a certain period of time. By passing a current through the second recovery primary coil having a large resistance value of the recovery transformer while commutating back electromotive force, the core magnetic flux is changed and energy is transmitted to the recovery secondary coil. is there.

  In such an energy recovery circuit, when increasing the decrease rate of the inductive load current, all current flows to the second primary coil for recovery having a large resistance value by turning off the recovery control element for a certain time. Therefore, a high voltage is generated at both ends of the second recovery primary coil, and the excitation of the transformer / core is changed, so that an induced current flows through the corresponding recovery secondary coil to recover energy. . At this time, the reduction rate of the inductive load current can be controlled at a high speed by varying the duty ratio of the recovery control element that is PWM-controlled by the control circuit.

  The energy recovery circuit further includes a second recovery control element arranged in series with the second recovery primary coil of the recovery transformer, whereby the first recovery value having a low resistance value is provided. The current flowing through the second recovery primary coil can be limited so that the voltage when the recovery control element of the primary coil is turned off is constant. As a result, even if the current decreases and the voltage across the second recovery primary coil decreases, the decrease in the amount of transmission to the recovery secondary coil is suppressed, and the loss of the second recovery control element The reduction rate of the inductive load current can be increased.

  FIG. 1 shows a schematic configuration diagram of an inductive load driving circuit according to a first embodiment of the present invention. The inductive load driving circuit 1 of the present embodiment includes a switching power supply circuit 10 as a basic configuration. That is, the bridge diode 13 that rectifies the alternating current from the power supply 12, the primary side smoothing capacitor 14 that smoothes the rectified direct current, and the direct current smoothed by the primary side smoothing capacitor 14 is converted into a pulse signal by the control circuit 20. A switching element (FET) 15 that performs on / off switching in a cycle based on the pulse signal generated by the generator 24 to convert the pulse wave to alternating current, and the pulse wave alternating current from the primary coil LP to the secondary coil LS. A switching transformer 16 that transforms and transmits the voltage to a predetermined voltage, a secondary rectifier diode 17 that rectifies the alternating current transmitted to the secondary side, and an inductive load (solenoid) that further smoothes the rectified direct current 11 is provided with a secondary side smoothing capacitor 18 to be sent to 11.

  In this embodiment, a proportional control element (FET) 19 for controlling the direct current obtained by the switching power supply circuit 10 having the above configuration based on the command signal 21 is further provided.

  In the control circuit 20, feedback control is performed on the proportional control element 19 via the insulation amplifier 22 based on the command signal 21 and the detection result on the output side by the current sensor 25. Furthermore, in this embodiment, the switching transformer 16 is configured to perform PWM control so that the voltage across the proportional control element 19 is constant. Specifically, the output of the differential amplifier 23 as a result is fed back (subtracted) to the offset which is a command for the voltage across the proportional control element 19, so that the switching transformer 16 Control is performed to cause the pulse signal generator 24 to generate a pulse signal for adjusting the switching period so that the pulse wave alternating current sent to the primary coil LP can make the voltage difference across the proportional control element 19 constant.

  As described above, in this embodiment, since the direct current sent to the solenoid 11 is controlled by the proportional control element 19 based on the command signal 21, the rate of increase and decrease in current is more directly controlled. Both can be controlled, and a high response of current reduction when the solenoid 11 is stopped, which has been difficult in the past, can be realized. Further, since the voltage at both ends of the proportional control element 19 is controlled to be constant, heat generation as in the case of performing control by variable loss of the voltage at both ends is prevented.

  Next, as the inductive load driving circuit according to the second embodiment of the present invention, the inductive load driving circuit according to the first embodiment further includes an energy recovery circuit 30 for recovering the back electromotive force when the solenoid current decreases. The case is shown in FIGS. FIG. 2 is a schematic overall configuration diagram showing the inductive load driving circuit of the present embodiment, and FIG. 3 is an operation waveform diagram of each part during load current commutation in the energy recovery circuit 30 of FIG. Is a voltage of the storage capacitor, (b) is a current of the primary coil for recovery, (c) is an ON / OFF interval of the recovery control element, and (d) is a variation of the current control deviation. In the present embodiment, the basic configuration includes the switching power supply circuit 10 and the control circuit 20 which are common to the inductive load driving circuit shown in FIG. 1, and the same reference numerals are used for the common parts in FIG.

  The energy recovery circuit 30 provided in this embodiment includes a recovery transformer 31 arranged in parallel with the solenoid 11, and the recovery control element 32 that controls the current of the recovery primary coil RLP has a current control deviation. When negative, the PWM is controlled in proportion to the deviation amount, whereby energy is transmitted to the recovery secondary coil RLS.

  Specifically, the recovery primary coil RLP of the recovery transformer 31 is connected in parallel to the solenoid 11, the recovery secondary coil RLS is connected to the primary side of the switching transformer 16, and further from the control circuit 20. A recovery control element 32 that operates in accordance with the pulse signal generated from the second pulse signal generator 33 based on the recovery command signal is arranged in series with the recovery primary coil RLP, and the recovery primary coil RLP. By performing PWM control on the current flowing through the current, energy is transmitted to the recovery secondary coil RLS while the commutation current from the solenoid 11 flows through the recovery primary coil RLP. As a result, the back electromotive force when the current of the solenoid 11 decreases can be recovered well, and the proportional control element 19 can be prevented from generating heat when the solenoid 11 is large.

  In this embodiment, a commutation circuit 36 is provided which is connected to the primary side of the recovery transformer 31 and commutates the back electromotive force of the solenoid 11 when the recovery control element 32 is turned off. A storage capacitor 37 is disposed in the circuit 36. Therefore, as shown in FIG. 3, when the current control deviation (FIG. 3 (d)) becomes negative, the control circuit 20 causes the recovery control element 32 to perform PWM control in proportion to the deviation amount (FIG. 3). (C)) However, as shown in the waveform of FIG. 3A, the commutation current from the solenoid 11 when the recovery control element 32 is OFF commutates the commutation circuit 36 and accumulates in the storage capacitor 37. Is done.

  Then, as shown in the current waveform of the primary coil for recovery in FIG. 3B, when the recovery control element 32 is turned on again, the charge accumulated in the storage capacitor 37 is released and the solenoid 11 Together with the commutation current, it is supplied to the recovery primary coil RLP, energy is transmitted to the recovery secondary coil RLS, and efficient energy recovery is achieved. By providing such an energy recovery circuit 30 in parallel with the solenoid 11, it is possible to prevent the back electromotive force from being consumed by the proportional control element 19 and generating heat when the solenoid current is reduced even when the solenoid 11 is large.

  Next, FIG. 4 and FIG. 5 show a case where an energy recovery circuit 40 different from the energy recovery circuit 30 in the second embodiment is provided as an inductive load driving circuit according to the third embodiment of the present invention. FIG. 4 is a schematic overall configuration diagram showing the inductive load driving circuit of this embodiment, and FIG. 5 is a partial circuit diagram showing the energy recovery circuit 40. FIG. 6 is a partial circuit diagram showing a further improvement of the energy recovery circuit 40 of FIG. In this embodiment, the basic configuration includes the switching power supply circuit 10 and the control circuit 20 which are common to the inductive load driving circuit shown in FIGS. 1 and 2, and in FIG. The same reference numerals are used respectively.

  The energy recovery circuit 40 provided in the present embodiment replaces the commutation circuit 36 in the energy recovery circuit 30 shown in the second embodiment with another second recovery circuit on the primary side of the recovery transformer 41. The primary side coil LP2 is provided.

  Specifically, the recovery transformer 41 is connected to the solenoid 11 in parallel and opposite in polarity to the first recovery primary coil LP1 having a relatively small resistance value and a relatively large resistance value. The two primary coils for the two recovery primary coils LP2 and one recovery secondary coil RLS connected to the primary side of the switching transformer 16 are provided in the same iron core. Then, a pulse signal generated by the second pulse signal generator 43 based on the recovery command signal from the control circuit 20 is arranged in series with the first primary coil for recovery LP1 having a small resistance of the two primary coils. A recovery control element 42 that operates in response to control the current flowing through the first recovery primary coil LP1 is provided.

  In the present embodiment, the control circuit 20 changes the pulse width of the pulse signal from the second pulse signal generator 43 for the recovery control element 42 when the current of the solenoid 11 decreases, and controls the recovery control element 42 to be off for a certain period of time. As a result, while the back electromotive force of the solenoid 11 is commutated, a current is passed through the second primary coil for recovery LP2 having a large resistance to transmit energy to the secondary coil for recovery RLS.

  That is, when the proportional control element 19 is turned off and the solenoid current flows through the commutation diode 44, the recovery control by the second pulse signal generator 43 is performed based on the recovery command signal when increasing the decrease rate of the solenoid current. By adjusting the pulse signal for the element 42, the recovery control element 42 is turned off for a predetermined time.

  Along with this, since all the current tends to flow to the second recovery primary coil LP2 having a large resistance, a high voltage is generated at both ends of the second recovery primary coil LP2, thereby exciting the transformer and the core. Therefore, an induced current flows through the recovery secondary coil RLS, and energy is recovered. At this time, the decrease rate of the solenoid current can be controlled at high speed by changing the duty ratio of the recovery control element 42 that is PWM-driven. By providing such an energy recovery circuit 40 in parallel with the solenoid 11, the increase / decrease of the solenoid current can be varied. By connecting the solenoid 11 in parallel (in the commutation circuit), the circuit of FIG. In this case, it is possible to prevent the back electromotive force from being consumed by the proportional control element 19 when the solenoid current is reduced and to generate heat, which contributes to further efficiency improvement of the inductive load driving circuit.

  In the energy recovery circuit 40 of FIGS. 4 and 5, when the back electromotive force recovery progresses and the commutation current becomes small, the voltage across the large recovery second recovery primary coil LP2 decreases, Recovery is also reduced. Therefore, based on the configuration of the energy recovery circuit 40 shown in FIG. 5, as shown in FIG. 6, the second recovery control element (FET) arranged in series with the high-resistance second recovery primary coil LP2 is used. ) 51 can be solved by using the energy recovery circuit 50 further including 51.

  That is, in the energy recovery circuit 50, the second recovery primary coil LP2 is made constant so that the voltage when the recovery control element 42 of the low recovery first recovery primary coil LP1 is turned off is constant. Can be limited by the second recovery control element 51, so that even if the voltage across the second recovery primary coil LP2 decreases, the amount of transmission to the recovery secondary coil RLS is thereby reduced. The decrease of the solenoid current can be suppressed, and the decrease rate of the solenoid current can be increased by the loss of the second recovery control element 51.

1, 100: Inductive load drive circuit 10: Switching power supply circuit 11, 111: Solenoid (inductive load)
12, 112: Supply power supply 13, 113: Bridge diode 14, 114: Smoothing capacitor (primary side)
15, 115: switching element 16, 116: switching transformer LP, Lp: primary coil LS, Ls: secondary coil 17, 35, 45, 117: rectifier diode 18, 118: smoothing capacitor (secondary side)
19: proportional control element 20: control circuit 21, 121: command signal 22: insulation amplifier 23: differential amplifier 24, 124: pulse signal generator 25, 125: current sensors 30, 40, 50: energy recovery circuits 31, 41 : Recovery transformer RLP: Recovery primary coil LP1: First recovery primary coil LP2: Second recovery primary coil RLS: Recovery secondary coils 32, 42: Recovery control elements 33, 43: Second pulse signal generators 34, 44: commutation diode 36: commutation circuit 37: storage capacitor 51: second recovery control element

Claims (5)

A rectifier bridge diode for rectifying an alternating current from the power source, the period and the primary-side smoothing capacitor for smoothing the rectified DC, a DC smoothed by the primary-side smoothing capacitor based on the pulse signal from the pulse signal generator A switching transformer that transforms the pulse wave converted to alternating current by on / off switching of the switching element into a predetermined alternating voltage and transmits it to the secondary side, and rectifies the alternating current transmitted to the secondary side A switching power supply circuit comprising a secondary side diode that performs smoothing and outputs a secondary side smoothing capacitor that further smoothes the rectified direct current, and the pulse based on the command signal and the detection result on the output side of the switching power supply circuit The on / off switching of the switching element is controlled by adjusting the pulse width of the pulse signal by the signal generator. A control circuit for, in inductive load driving circuit having,
A proportional control element for controlling a current output from the switching power supply circuit to the inductive load according to a command signal;
The inductive load driving circuit characterized in that the control circuit controls the pulse signal generator to adjust the switching pulse width of the switching element so that the voltage across the proportional control element is constant. . An energy recovery circuit for recovering the inductive load while reducing the back electromotive force when the current of the inductive load is reduced;
The energy recovery circuit includes a recovery transformer having a recovery primary coil connected in parallel to the inductive load and a recovery secondary coil connected to a primary side of the switching transformer, and the control circuit. A second pulse signal generator for generating a pulse signal based on the recovery command signal, and being arranged in series with the primary coil for recovery and operating in response to the pulse signal from the second pulse signal generator A recovery control element that controls a current flowing through the recovery primary coil, and a commutation that is connected to the primary side of the recovery transformer and that the back electromotive force of the inductive load is commutated when the recovery control element is off. A circuit, and
The control circuit adjusts a pulse width of a pulse signal by the second pulse signal generator with respect to the recovery control element when the current of the inductive load is reduced, and controls switching of the recovery control element, thereby controlling the recovery control element. The inductive load according to claim 1, wherein energy is transmitted to the secondary coil for recovery while the back electromotive force of the inductive load is commutated to the primary coil for recovery of the transformer for recovery. Driving circuit.   The commutation circuit of the energy recovery circuit accumulates the commutation current of the inductive load when the recovery control element is turned off and releases the accumulated charge when the recovery control element is turned on again. The inductive load drive circuit according to claim 2, further comprising a storage capacitor that supplies current to the primary coil for recovery. The energy recovery circuit, as the commutation circuit, has a relatively large resistance value provided on the same iron core of the recovery transformer with a polarity opposite to that of the recovery primary coil to which the recovery control element is connected. A primary coil for recovery of
The control circuit adjusts the pulse width of the pulse signal by the second pulse signal generator with respect to the recovery control element when the current of the inductive load is reduced, and controls the recovery control element to be off for a certain period of time. A current is passed through the second recovery primary coil of the recovery transformer while the back electromotive force of the inductive load is commutated to change the core magnetic flux and transmit energy to the recovery secondary coil. The inductive load driving circuit according to claim 2, wherein the inductive load driving circuit is provided.   The energy recovery circuit is arranged in series with the second recovery primary coil, and makes the voltage constant when the recovery control element of the recovery primary coil having a relatively small resistance value is turned off. The induction load drive circuit according to claim 4, further comprising a second recovery control element that limits a current flowing through the second recovery primary coil.

Images