JP6757637B2 - Inductive load drive - Google Patents

Description

The present invention relates to an inductive load drive device.

Patent Document 1 below discloses an inductive load driving device capable of preventing destruction of a circuit element in a DC power supply when a counter electromotive force from an inductive load is regenerated. This inductive load drive device includes a switching element inserted between the other end of the inductive load and the ground, and when the output voltage of the DC power supply during regeneration becomes equal to or higher than a preset threshold value. It is provided with a circuit element protection circuit that outputs the counter electromotive force generated by the inductive load to the ground by turning on the switching element. According to the inductive load drive device having such a circuit element protection circuit, it is possible to suppress the application of a high voltage to the DC power supply, and the smoothing capacitor provided in the DC power supply can be miniaturized.

Japanese Unexamined Patent Publication No. 2012-70534

However, in Patent Document 1, the circuit element protection circuit includes a determination circuit having a plurality of resistors and comparators, and a conduction circuit having a switching element and a diode. For this reason, the inductive load driving device has a complicated structure including a large number of elements.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to simplify the structure of an inductive load drive device while making it possible to use a small smoothing capacitor in a DC power supply.

The present invention adopts the following configuration as a means for solving the above problems.

The first invention is a drive circuit that drives an inductive load based on power supplied from a DC power supply provided with a smoothing capacitor at at least one of a pair of output ends, and a control circuit that controls the drive circuit. It is an inductive load drive device including the above, and adopts a configuration including an active clamp circuit that voltage-clamps the drive circuit so that the terminal voltage of the smoothing capacitor becomes a predetermined limit voltage or less.

The second invention is the first switching element in which the drive circuit is provided between the high potential side output end of the DC power supply and one end of the inductive load, and the DC power supply. A second switching element provided between the high potential side output end of the above and the other end of the inductive load, and provided between the low potential side output end of the DC power supply and one end of the inductive load. A configuration is adopted in which a third switching element and a fourth switching element provided between the low potential side output end of the DC power supply and the other end of the inductive load are provided.

In the third invention, in the second invention, the fourth switching element is a transistor, and the active clamp circuit changes the control terminal voltage of the fourth switching element to a voltage at which the fourth switching element is turned on. A configuration is adopted in which the drive circuit is voltage-clamped by clamping.

In the fourth invention, in the third invention, the active clamp circuit is a series circuit of a constant voltage diode and a switch provided between the other end of the inductive load and the control terminal of the transistor, and the above. A resistor provided between the control terminal of the transistor and the output terminal on the low potential side of the DC power supply is provided, and the constant voltage diode is provided with the anode terminal on the control terminal side of the transistor. adopt.

In the fifth invention, in any one of the second to fourth inventions, the anode terminal is connected to the other end of the inductive load, and the cathode terminal is the high potential side output terminal of the DC power supply. It adopts the configuration that it is a diode connected to.

A sixth invention comprises, in any one of the first to fifth inventions, a battery and a booster circuit that boosts the power input from the battery and supplies it to the drive circuit. Is adopted.

According to the present invention, the active clamp circuit for voltage-clamping the drive circuit so that the terminal voltage of the smoothing capacitor included in the DC power supply becomes equal to or lower than a predetermined limit voltage is provided. By providing such an active clamp circuit, it is possible to prevent a voltage higher than a predetermined limiting voltage from being applied to the smoothing capacitor included in the DC power supply without using the circuit element protection circuit as shown in Patent Document 1. can do. Therefore, according to the present invention, it is possible to simplify the structure of the inductive load drive device while making it possible to use a small smoothing capacitor in the DC power supply.

It is a circuit block diagram which includes an inductive load drive device in one Embodiment of this invention. It is a timing chart for demonstrating the operation of the inductive load drive device in one Embodiment of this invention.

Hereinafter, an embodiment of the inductive load driving device according to the present invention will be described with reference to the drawings. In the drawings below, the scale of each member is appropriately changed in order to make each member recognizable.

FIG. 1 is a circuit configuration diagram including the inductive load driving device 1 of the present embodiment. As shown in this figure, the inductive load drive device 1 of the present embodiment is electrically connected to the DC power supply 10 and the inductive load 20, and is guided based on the electric power supplied from the DC power supply 10. Drive sexual load.

The DC power supply 10 includes a battery 30 and a booster circuit 40. The battery 30 is a battery including a plurality of battery cells, and has a positive electrode terminal and a negative electrode terminal. In this battery 30, the positive electrode terminal is connected to the booster circuit 40, and the negative electrode terminal is connected to the ground. The negative electrode terminal of the battery 30 functions as a low potential side output terminal of the DC power supply 10.

The booster circuit 40 has a coil 41 having one end connected to the input end of the booster circuit 40 and an anode terminal connected to the other end of the coil 41, and the cathode terminal is the output end of the booster circuit 40 (high voltage side of the DC power supply 10). The diode 42 connected to the output terminal), the voltage dividing circuit 43 inserted between the output end of the booster circuit 40 and the ground, and the voltage dividing circuit 43 inserted between the anode terminal and the ground of the diode 42. The output of the booster circuit control circuit 45 and the booster circuit 40 that PWM control the on / off operation of the switching element 44 so as to keep the output voltage constant while referring to the output values of the switching element 44 and the voltage dividing circuit 43. It is provided with a boosting capacitor 46 (smoothing capacitor) inserted between the end and the ground. Such a booster circuit 40 boosts the electric power supplied from the battery 30 and supplies it to the drive circuit 2 described later of the inductive load drive device 1.

Such a DC power supply 10 includes a pair of output ends including a high potential side output end (output end of the booster circuit) and a low battery side output end (negative electrode terminal of the battery 30), and is provided at the high potential side output end. The step-up capacitor 46 provided is provided. When the counter electromotive force is regenerated from the inductive load 20, the boosting capacitor 46 temporarily stores the counter electromotive force. The configuration of the booster circuit 40 in the DC power supply 10 is not limited to the above configuration. It is also possible that the DC power supply 10 is not provided with the booster circuit 40 but is provided with only a smoothing capacitor.

As shown in FIG. 1, the inductive load drive device 1 of the present embodiment includes a drive circuit 2, an active clamp circuit 3, and a control circuit 4. In addition, in FIG. 1, in order to improve visibility, the inductive load 20 is included in the range shown as the inductive load driving device 1 of the present embodiment, but the inductive load 20 is described above. As such, it does not belong to the inductive load drive device 1.

The drive circuit 2 includes a first switching element 2a, a second switching element 2b, a third switching element 2c, and a fourth switching element 2d. The first switching element 2a is provided between the high potential side output end of the DC power supply 10 and one end of the inductive load 20. In this embodiment, the first switching element 2a is a FET (Field Effect Transistor), a gate terminal (control terminal) is connected to the control circuit 4, and the voltage value is high from the control circuit 4. When the control signal is input to the gate terminal, it is turned on, and when the control signal having a low voltage value is input to the gate terminal, it is turned off. As shown in FIG. 1, the first switching element 2a is provided with a protection diode 2e.

The second switching element 2b is provided between the high potential side output end of the DC power supply 10 and the other end of the inductive load 20. In the present embodiment, the second switching element 2b is a diode, the anode terminal is connected to the other end of the inductive load 20, and the cathode terminal is connected to the high potential side output terminal of the DC power supply 10.

The third switching element 2c is provided between the low potential side output end (ground) of the DC power supply 10 and one end of the inductive load 20. The fourth switching element 2d is provided between the low potential side output end (ground) of the DC power supply 10 and the other end of the inductive load 20. In the present embodiment, these the third switching element 2c and the fourth switching element 2d are FETs like the first switching element 2a, and the gate terminal (control terminal) is connected to the control circuit 4. As shown in FIG. 1, the third switching element 2c is provided with a protection diode 2f. Further, the fourth switching element 2d is provided with a protection diode 2g.

The first switching element 2a, the third switching element 2c, and the fourth switching element 2d may be, for example, a bipolar transistor or an IGBT (Insulated Gate Bipolar Transistor) in addition to the FET. Further, the third switching element 2c can be a diode as well as the second switching element 2b.

Such a drive circuit 2 drives the inductive load 20 under the control of the control circuit 4 based on the electric power supplied from the DC power supply 10. Further, the drive circuit 2 supplies the counter electromotive force to the DC power supply 10 when the counter electromotive force is output from the inductive load 20.

The active clamp circuit 3 includes a series circuit 3a and a resistor 3b. One end of the series circuit 3a is connected between the other end of the inductive load 20 and the fourth switching element 2d, and the other end is connected to the gate terminal of the fourth switching element 2d. That is, the series circuit 3a is provided between the other end of the inductive load 20 and the fourth switching element 2d made of a transistor. This series circuit 3a has a constant voltage diode 3a1 arranged in series and a switch 3a2. The constant voltage diode 3a1 is applied to the step-up capacitor 46 when the anode terminal is provided on the gate terminal side of the fourth switching element 2d and the switch 3a2 is on (that is, when the series circuit 3a is conductive). Specify the voltage. Here, the constant voltage diode 3a1 is a series circuit in which the switch 3a2 is turned on when the voltage of the boosting capacitor 46 exceeds the reference voltage set below the rated voltage (predetermined limiting voltage) of the boosting capacitor 46. The breakdown voltage is set so that a current flows through 3a. When a current can pass through the series circuit 3a, the constant voltage diode 3a1 clamps the voltage at the gate terminal of the fourth switching element 2d to a high state, and always keeps the fourth switching element 2d on. The switch 3a2 switches the conduction state of the series circuit 3a, and is controlled by the control circuit 4.

One end of the resistor 3b is connected to the gate terminal of the fourth switching element 2d, and the other end is connected between the fourth switching element 2d and the ground. That is, the resistor 3b is provided between the gate terminal of the fourth switching element 2d, which is a transistor, and the low potential side output end of the DC power supply 10. The resistor 3b has a lower resistance value than the output terminal side of the control circuit 4 and a higher resistance than the gate terminal. Such a resistor 3b causes the current flowing through the series circuit 3a to flow toward the ground.

Such an active clamp circuit 3 is provided separately from the drive circuit 2 and the control circuit 4, and when the voltage of the boosting capacitor 46 becomes equal to or higher than the reference voltage, the fourth switching element 2d is always on. Therefore, the voltage at the gate terminal of the fourth switching element 2d is clamped to a high state. That is, the active clamping circuit 3 voltage-clamps the drive circuit 2 so that the terminal voltage of the boosting capacitor 46 of the DC power supply 10 becomes a reference voltage set to be equal to or lower than the rated voltage of the boosting capacitor 46. The reference voltage has been obtained in advance by experiments and simulations, and is stored in the control circuit 4 in advance.

The control circuit 4 is a microcontroller that controls the first switching element 2a, the third switching element 2c, and the fourth switching element 2d, and the first switching element 2a, the third switching element 2c, based on a program stored inside. And the control signal is input to the gate terminal of the fourth switching element 2d. That is, the control circuit 4 controls the drive circuit 2. Further, the control circuit 4 controls the switch 3a2 of the active clamp circuit 3. Specifically, the control circuit 4 turns on the switch 3a2 during a period in which the boosting capacitor 46 may exceed the reference voltage when the supply of the counter electromotive force to the boosting capacitor 46 is not restricted. For example, the control circuit 4 turns on the switch 3a2 at least during the period when the counter electromotive force is output from the inductive load 20.

Next, the operation of the inductive load driving device 1 of the present embodiment configured in this way will be described with reference to the timing chart of FIG.

In the timing chart shown in FIG. 2, the active clamp circuit 3 is always operated (switch 3a2 is not turned on) and the active clamp circuit 3 is operated at least during the period when the voltage of the boosting capacitor 46 rises (switch 3a2). (Turn on) and the case are shown side by side in chronological order. More specifically, the case where the active clamp circuit 3 is not always operated is shown first in the time series, and after the time series, the active clamp circuit 3 is operated at least during the period when the voltage of the boosting capacitor 46 rises. It shows the case of operating. Of these two operations, the pattern in which the active clamp circuit 3 is operated corresponds to the operation of the inductive load drive device 1 of the present embodiment of the present embodiment.

Further, in the timing chart shown in FIG. 2, the load current indicates the current flowing through the inductive load 20. Further, in the timing chart shown in FIG. 2, the switch shows the on / off state of the switch 3a2 of the active clamp circuit 3. Further, in the timing chart shown in FIG. 2, the gate voltage (1) indicates the voltage of the gate electrode of the first switching element 2a (that is, the control signal input to the first switching element 2a), and the gate voltage (3) is the first. The voltage of the gate electrode of the 3 switching element 2c (that is, the control signal input to the 3rd switching element 2c) is shown, and the gate voltage (4) is the voltage of the gate electrode of the 4th switching element 2d (that is, the 4th switching element 2d). The input control signal) is shown. Further, in the timing chart shown in FIG. 2, the rated voltage indicates the rated voltage of the step-up capacitor 46.

The inductive load 20 is driven by inputting a pulsed control signal from the control circuit 4 to the first switching element 2a, the third switching element 2c, and the fourth switching element 2d. When supplying electric power to the inductive load 20, the control circuit 4 switches between the on state and the off state of the first switching element 2a and the third switching element 2c while keeping the fourth switching element 2d on. Here, as shown in FIG. 2, when the first switching element 2a is in the on state, the third switching element 2c is turned off, and when the first switching element 2a is in the off state, the third switching element 2c is turned off. Is turned on.

When the fourth switching element 2d is in the on state, the first switching element 2a is in the on state, and the third switching element 2c is in the off state, the load current sharply increases as shown in FIG. That is, when the first switching element 2a is on and the third switching element 2c is off, power is supplied from the booster circuit 40 or the DC power supply 10 to the inductive load 20. Further, when the fourth switching element 2d is in the on state, the first switching element 2a is in the off state, and the third switching element 2c is in the on state, the load current changes constantly as shown in FIG. Here, the counter electromotive force generated by the inductive load 20 returns to the inductive load 20 via the third switching element 2c again.

On the other hand, when the power supply to the inductive load 20 is stopped, the control circuit 4 of the fourth switching element 2d keeps the first switching element 2a in the off state and the third switching element 2c in the on state. Switch between on and off states. When the first switching element 2a is in the off state, the third switching element 2c is in the on state, and the fourth switching element 2d is in the off state, the counter electromotive force generated by the inductive load 20 is the second switching. Power is supplied to the boost capacitor 46 of the booster circuit 40 via the element 2b, and electricity is stored. At this time, as shown in FIG. 2, the load current drops sharply. The electric power stored in the step-up capacitor 46 is discharged the next time the electric power is supplied to the inductive load 20. Further, when the first switching element 2a is left off, the third switching element 2c is left on, and the fourth switching element 2d is on, the counter electromotive force generated by the inductive load 20 is regenerated. The load current returns to the inductive load 20 via the third switching element 2c, and the load current changes constantly.

Here, when the active clamp circuit 3 is not operated (the switch 3a2 is not turned on), the counter electromotive force always regenerates to the step-up capacitor 46 during the period when the load current tends to decrease, and the step-up capacitor 46 sets the rated voltage. Boost beyond. On the other hand, when the active clamp circuit 3 is operated (switch 3a2 is turned on), when the voltage of the boosting capacitor 46 approaches the rated voltage and exceeds the reference voltage, a current flows through the constant voltage diode 3a1 to the series circuit 3a. , The voltage of the drive circuit 2 (that is, the boosting capacitor 46) is clamped to the reference voltage. At this time, since a high voltage is always applied to the gate terminal of the 4th switching element 2d, the 4th switching element 2d is always in the ON state, and the counter electromotive current generated by the inductive load 20 causes the 4th switching element 2d. It flows to the ground through.

According to the inductive load drive device 1 of the present embodiment as described above, the active circuit 2 is voltage-clamped so that the terminal voltage of the booster capacitor 46 included in the booster circuit 40 of the DC power supply 10 is equal to or lower than the rated voltage. A clamp circuit 3 is provided. By providing such an active clamp circuit 3, it is possible to prevent a voltage higher than the rated voltage from being applied to the boosting capacitor 46 without using a circuit element protection circuit as shown in Patent Document 1. Therefore, according to the inductive load drive device 1 of the present embodiment, it is possible to simplify the structure of the inductive load drive device 1 while enabling the use of a small step-up capacitor 46.

Further, in the inductive load drive device 1 of the present embodiment, the fourth switching element 2d is a transistor, and in the active clamp circuit 3, the control terminal voltage of the fourth switching element 2d is set to the on state of the fourth switching element 2d. The drive circuit 2 is voltage-clamped by clamping the voltage to Therefore, according to the inductive load drive device 1 of the present embodiment, when the voltage of the drive circuit 2 is clamped, it reverses to the ground (low potential side output terminal of the DC power supply 10) via the fourth switching element 2d. Electromotive force can flow. Therefore, according to the inductive load drive device 1 of the present embodiment, it is not necessary to separately provide a path for releasing the counter electromotive force to the ground, and a simple configuration can be obtained.

Further, in the inductive load drive device 1 of the present embodiment, the active clamp circuit 3 is a constant voltage diode 3a1 and a switch 3a2 provided between the other end of the inductive load 20 and the gate terminal of the fourth switching element 2d. The series circuit 3a with the above and the resistor 3b provided between the gate terminal of the fourth switching element 2d and the output end on the low potential side of the DC power supply 10 are provided. Further, the constant voltage diode 3a1 is provided with an anode terminal on the gate terminal side of the fourth switching element 2d. Therefore, according to the inductive load driving device 1 of the present embodiment, it is possible to apply a voltage equal to or higher than the rated voltage to the boosting capacitor 46 with a simple circuit configuration without constantly monitoring the voltage of the boosting capacitor 46. Can be prevented.

Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to the above embodiment. The various shapes and combinations of the constituent members shown in the above-described embodiment are examples, and can be variously changed based on design requirements and the like without departing from the spirit of the present invention.

For example, in the above embodiment, the configuration in which the second switching element 2b is a diode has been described. However, the present invention is not limited to this, and it is also possible to adopt a configuration in which the second switching element is a transistor.

Further, in the above embodiment, a configuration in which one end of the series circuit 3a is connected between the other end of the inductive load 20 and the fourth switching element 2d has been described. However, the present invention is not limited to this. For example, it is also possible to adopt a configuration in which the other end of the inductive load 20 and the second switching element 2b are connected.

Further, in the above embodiment, the configuration including one drive circuit 2 has been described. However, the present invention is not limited to this, and it is also possible to adopt a configuration in which a plurality of drive circuits 2 are provided and a plurality of inductive loads 20 can be driven. In this case, in principle, the active clamp circuit 3 is installed in all the drive circuits 2, but it is also possible to install the active clamp circuit 3 in only one of the drive circuits 2 to raise an exception. ..

Further, in the above embodiment, the configuration in which the DC power supply 10 for supplying electric power to the inductive load drive device 1 of the present invention includes a booster circuit and the smoothing capacitor of the present invention is a booster capacitor 46 has been described. However, the present invention is not limited to this, and can be applied to all inductive load drive devices to which power is supplied from a DC power source including a smoothing capacitor connected to an output terminal.

1 ... Inductive load drive device, 2 ... Drive circuit, 2a ... 1st switching element, 2b ... 2nd switching element, 2c ... 3rd switching element, 2d ... 4th switching element, 3 ... Active clamp circuit, 3a ... series circuit, 3a1 ... constant voltage diode, 3a2 ... switch, 3b ... resistor, 4 ... control circuit, 10 ... DC power supply, 20 ... inductive load, 30 ... Battery, 40 ... Boost circuit, 46 ... Boost capacitor (smoothing capacitor)

Claims (3)

An inductive load including a drive circuit that drives an inductive load based on electric power supplied from a DC power source provided with a smoothing capacitor at at least one of a pair of output ends, and a control circuit that controls the drive circuit. It ’s a drive device,
An active clamp circuit for voltage-clamping the drive circuit so that the terminal voltage of the smoothing capacitor becomes equal to or lower than a predetermined limit voltage is provided.
The drive circuit
A first switching element provided between the high potential side output end of the DC power supply and one end of the inductive load, and
A second switching element provided between the high potential side output end of the DC power supply and the other end of the inductive load, and
A third switching element provided between the low potential side output end of the DC power supply and one end of the inductive load, and
A fourth switching element provided between the low potential side output end of the DC power supply and the other end of the inductive load.
With
The fourth switching element is a transistor and
The active clamp circuit voltage-clamps the drive circuit by clamping the control terminal voltage of the fourth switching element to a voltage at which the fourth switching element is turned on.
The active clamp circuit is
A series circuit of a constant voltage diode and a switch provided between the other end of the inductive load and the control terminal of the transistor,
A resistor provided between the control terminal of the transistor and the output end on the low potential side of the DC power supply is provided.
The constant voltage diode has an anode terminal provided on the control terminal side of the transistor.
The switch is an inductive load drive device, characterized in that the switch is controlled separately from the drive circuit by the control circuit . The second switching element is the diode according to claim 1, wherein the anode terminal is connected to the other end of the inductive load, and the cathode terminal is connected to the high potential side output end of the DC power supply. Inductive load drive. The DC power supply
Batteries and
The inductive load drive device according to claim 1 or 2, further comprising a booster circuit that boosts power input from the battery and supplies the power to the drive circuit.

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