TWI825399B - Inductive load drive circuit and electromagnetic braking system - Google Patents

Abstract

The first transistor (Tr1) and the second transistor (Tr2) are arranged at opposite corners of the full bridge circuit. The first diode (D1) is disposed between the first output terminal (OUT1) and the negative power line (104). The Darlington circuit (112) is provided between the second output terminal (OUT2) and the positive power line (102). The Zener diode (ZD1) is provided between the control terminal and the second output terminal (OUT2) of the Darlington circuit (112).

Description

Inductive load drive circuit and electromagnetic braking system

The present disclosure relates to a driving circuit for an inductive load.

As a mechanism for stopping the rotation of the motor, electromagnetic brakes are widely used. The electromagnetic brake is one of the mechanical brakes. In a non-excitation actuation type electromagnetic brake, when the excitation coil is not energized, the armature is pressed against the brake hub by the spring coil, and the brake enters the operating state (holding state). When a voltage is applied to the excitation coil, the electromagnet attracts the armature and the brake becomes an open state. Due to such characteristics, non-excitation actuated electromagnetic brakes are often used in applications where safety is prioritized during emergencies or power outages.

Figure 1 is a block diagram of a control system with a motor. Rectifier 10 rectifies AC voltage. The inverter 20 converts the DC voltage V _DC generated by the rectifier 10 into an AC voltage and drives the motor 2 .

The electromagnetic brake 4 and the brake drive circuit 40 form an electromagnetic braking system. The brake drive circuit 40 switches the excitation coil of the electromagnetic brake 4 between excitation (energized) and non-excitation (non-energized) to switch between release and braking.

2(a) and 2(b) are circuit diagrams showing a structural example of the brake drive circuit 40. The brake drive circuit 40 of FIG. 2(a) is a full-bridge circuit including transistors Tr1 to Tr4. During the braking release (non-braking) period, the pair of transistor Tr1 and transistor Tr2 is turned on, and a voltage of the first polarity is applied to the excitation coil of the electromagnetic brake 4 . In this state, the holding current I ₀ flows through the excitation coil.

During braking, the brake drive circuit 40 turns on the pair of transistor Tr3 and transistor Tr4, and applies a voltage with the opposite polarity to the release state to the excitation coil to extinguish the arc of the electromagnetic brake.

The brake driving circuit 40 of FIG. 2(b) includes a diagonal bridge circuit including a transistor Tr1, a transistor Tr2, and a diode D1 and a diode D2. During the braking release (non-braking) period, the pair of transistor Tr1 and transistor Tr2 is turned on, and a voltage of the first polarity is applied to the excitation coil of the electromagnetic brake 4 . In this state, the holding current I ₀ flows through the excitation coil.

When the electromagnetic brake arc extinguishes, the transistors Tr1 and Tr2 are disconnected. The current flowing through the excitation coil is regenerated via diodes D1 and D2, and the electromagnetic brake is extinguished. [Prior technical literature]

[Patent Document 1] Japanese Patent Application Laid-Open No. 9-69435 [Patent Document 2] Japanese Patent Application Publication No. 2018-43624 [Patent Document 3] Japanese Patent Application Publication No. 2017-185596 [Patent Document 4] Japanese Patent Publication No. 2015-533206

[Problem to be solved by the invention]

Question 1. The brake drive circuit in Figure 2(a) has a large number of transistors, and a gate drive circuit must be provided for each transistor, so the circuit scale is large.

In the brake drive circuit of Figure 2(b), the arc extinguishing time τ required to keep the current I ₀ reduced to 0 is given in equation (1) and is limited by the DC voltage V _PN .

In addition, the same problem is not limited to the drive circuit of the excitation coil of the electromagnetic brake, but also applies to drive circuits targeting other inductive loads.

Question 2. In the technology of Patent Document 3, the excitation coil of the electromagnetic brake is driven by a DC voltage source. Therefore, in order to shorten the time from the start of excitation until the brake is released, the DC voltage must be increased. At this time, the current in the holding state causing the brake to operate becomes larger, and the power consumption increases.

On the contrary, if the DC voltage is reduced in order to reduce the current in the brake-released state, the time until the brake is released becomes longer. Therefore, in the past, there was a trade-off between brake opening time and power consumption.

The aspect of the present disclosure was developed under this circumstance, and one of its exemplary purposes is to provide a driving circuit capable of reducing the current of an inductive load in a short time.

Another aspect of the present disclosure was developed under this circumstance, and one of its illustrative purposes is to provide a drive circuit that can shorten the opening time of the brake and reduce power consumption. [Technical means to solve problems]

1. A driving circuit according to the present disclosure includes: a first output terminal and a second output terminal connected to an inductive load; a first transistor provided between the first output terminal and the positive power line; and a first transistor provided between the first output terminal and the positive power line; a first diode between the terminal and the negative power supply line; a second transistor disposed between the second output terminal and the negative power supply line; a Darlington circuit disposed between the second output terminal and the positive power supply line ( Darlington Circuit); and a Zener diode disposed between the control terminal and the second output terminal of the Darlington circuit.

According to this aspect, a voltage higher than the voltage of the positive power supply line can be generated at the second output terminal, the boosted voltage can be applied to the inductive load, and the current of the inductive load can be reduced in a short time.

Another aspect of this disclosure is also a driving circuit. The drive circuit includes: a first output terminal and a second output terminal connected to an inductive load; a first transistor disposed between the first output terminal and the positive power supply line; and a first transistor disposed between the first output terminal and the negative power supply line. The Darlington circuit; the Zener diode disposed between the control terminal of the Darlington circuit and the first output terminal; the second transistor disposed between the second output terminal and the negative power line; and A second diode between the second output terminal and the positive power line.

According to this aspect, a voltage lower than the voltage of the negative power supply line can be generated at the first output terminal, and the current of the inductive load can be reduced in a short time by applying the boosted voltage to the inductive load.

The Darlington circuit may also include: a third transistor with a base connected to the anode of the Zener diode; a fourth transistor with a base connected to the emitter of the third transistor; and a collector connected to the third transistor. pole connected resistor.

The inductive load can also be the coil of a non-excitation electromagnetic brake. This enables high-speed braking.

2. A brake drive circuit according to the present disclosure includes: a full-bridge circuit connected to an excitation coil of the electromagnetic brake; a current detection circuit that detects coil current flowing through the excitation coil; and a controller that responds to an excitation command. , starts driving the transistor pairs of the diagonal arms of the full-bridge circuit, and when detecting a change in the coil current caused by the start of movement of the armature, reduces the duty cycle of the transistor pair.

The moment the armature starts moving, a back electromotive force is generated, so the coil current is temporarily reduced. By detecting changes in coil current, the actual moment when the brake is released can be known.

Let the power supply voltage of the full-bridge circuit be V _PN , let the duty cycle of the transistor pair before detection of the change in the coil current be d1, and let the duty cycle of the transistor pair after the detection of the change in the coil current be d2. Just after the excitation command is generated, the driving voltage V _L applied to the excitation coil is equal to d1 × V _PN , and the driving voltage V _L after the armature movement starts is d2 × V _PN . Taking V _PN and d1 and d2 as the three Action parameters can specify driving conditions. Therefore, by designing a larger V _PN and duty cycle d1, while shortening the time required for brake release, and reducing the duty cycle d2, the current after the brake is released can be reduced, and power consumption can be reduced.

The full-bridge circuit may also include: a first output terminal and a second output terminal connected to the excitation coil; a first transistor disposed between the first output terminal and the positive power supply line; and a first transistor disposed between the first output terminal and the negative power supply line. a diode between the lines; a second transistor disposed between the second output terminal and the negative power line; a Darlington circuit disposed between the second output terminal and the positive power line; and a Darlington circuit disposed between Zener diode between the control terminal and the second output terminal of the circuit.

According to this aspect, a voltage higher than the voltage of the positive power supply line can be generated at the second output terminal, and by applying the boosted voltage to the excitation coil, the time until the electromagnetic brake takes effect can be shortened.

The full-bridge circuit may also include: a first output terminal and a second output terminal connected to the excitation coil; a first transistor disposed between the first output terminal and the positive power supply line; and a first transistor disposed between the first output terminal and the negative power supply line. a Darlington circuit between lines; a Zener diode disposed between the control terminal of the Darlington circuit and the first output terminal; a second transistor disposed between the second output terminal and the negative power supply line; and a diode disposed between the second output terminal and the positive power line.

According to this aspect, a voltage lower than the voltage of the negative power supply line can be generated at the first output terminal, and by applying the boosted voltage to the excitation coil, the time until the electromagnetic brake takes effect can be shortened.

The Darlington circuit may also include: a third transistor with a base connected to the anode of the Zener diode; a fourth transistor with a base connected to the emitter of the third transistor; and a collector connected to the third transistor. pole connected resistor.

In addition, any combination of the above constituent elements or the mutual replacement of constituent elements or expressions of the present invention between methods, devices, systems, etc. are also valid as aspects of the present invention.

Furthermore, the description of this item (means for solving the problem) does not describe all the features that are indispensable to the present invention. Therefore, a sub-combination of the described features may also constitute the present invention. In addition, any combination of the above constituent elements or the mutual replacement of constituent elements or expressions of the present invention between methods, devices, systems, etc. are also valid as aspects of the present invention.

Furthermore, the description of this item (means for solving the problem) does not describe all the features that are indispensable to the present invention. Therefore, a sub-combination of the described features may also constitute the present invention. [Effects of the invention]

According to one aspect of the present invention, the current of the inductive load can be reduced in a short time.

Hereinafter, the present invention will be described based on suitable embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same symbols, and repeated descriptions are appropriately omitted. In addition, the embodiments are examples and do not limit the inventors, and all the features described in the embodiments or their combinations do not necessarily limit the essence of the invention.

(Embodiment 1) FIG. 3 is a circuit diagram of the drive circuit 100A according to the first embodiment. The drive circuit 100A drives the coil L1 as an inductive load. The type of inductive load is not limited. For example, it can be an excitation coil of an electromagnetic brake. The drive circuit 100A includes a first output terminal OUT1, a second output terminal OUT2, a first transistor Tr1, a second transistor Tr2, a first diode D1, and a Darlington circuit 112.

The first output terminal OUT1 is connected to one end of the coil L1, and the second output terminal OUT2 is connected to the other end of the coil L1. The first transistor Tr1 is provided between the first output terminal OUT1 and the positive power supply line 102 . The first diode D1 is disposed between the first output terminal OUT1 and the negative power line 104 . The second transistor Tr2 is provided between the second output terminal OUT2 and the negative power supply line 104 . The first transistor Tr1 and the second transistor Tr2 are IGBTs (Insulated Gate Bipolar Transistors).

The Darlington circuit 112 is provided between the second output terminal OUT2 and the positive power line 102 . The Zener diode ZD1 is disposed between the gate (ie, the base) of the Darlington circuit 112 and the second output terminal OUT2.

The Darlington circuit 112 includes third and fourth transistors Tr3 and Tr4 which are NPN bipolar transistors and a resistor R1. The base of the third transistor Tr3 is connected to the anode of the Zener diode ZD1. The emitter of the fourth transistor Tr4 is connected to the positive power supply line 102, the collector is connected to the second output terminal OUT2, and the base is connected to the emitter of the third transistor Tr3. The resistor R1 is provided between the collector of the third transistor Tr3 and the second output terminal OUT2.

The above is the structure of the drive circuit 100A. Next, assuming that the coil L1 is an excitation coil of a non-excitation type electromagnetic brake, the operation of the electromagnetic brake system including the drive circuit 100A and the electromagnetic brake will be described.

FIG. 4 is an operation waveform diagram of the drive circuit 100A of FIG. 3 . Before time t ₀ , during the braking release period, the first transistor Tr1 and the second transistor Tr2 are turned on, generating the positive voltage V _PN of the positive power supply line 102 at the first output terminal OUT1 and generating the negative voltage at the second output terminal OUT2 The voltage of power line 104 (0V). At this time, the coil current _IL of the current amount I ₀ flows in the coil L1 in the right direction in the circuit diagram of FIG. 3 .

When a braking command is generated at time t ₀ , the first transistor Tr1 and the second transistor Tr2 of the drive circuit 100A are turned off. As a result, the coil current _IL starts to flow in the path of the first diode D1, the coil L1, and the Darlington circuit 112. At this time, the voltage of the first output terminal OUT1 becomes 0V, and the voltage of the second output terminal OUT2 becomes V _PN +Vz+2×Vbe. Vz is the Zener voltage of the Zener diode ZD1, and Vbe is the base-emitter voltage of the third transistor Tr3 and the fourth transistor Tr4. When it can be considered that Vbe≈0, the voltage of the second output terminal OUT2 is approximately V _PN +Vz. At this time, V _L ≈ V _PN +Vz is applied between both ends of the coil L1.

The coil current _IL after time t ₀ is expressed by equation (2) and decreases with time. The arc extinguishing time τ until the coil current _IL becomes 0 is expressed by equation (3).

In Figure 4, the operation when using the diagonal bridge circuit of Figure 2(b) is represented by a one-dot chain line. The arc extinguishing time τ' at this time is given in (1), and the arc extinguishing time τ' is (V _PN +Vz)/V _PN times the arc extinguishing time τ in the first embodiment. In other words, according to this embodiment, the arc extinguishing time can be shortened to V _PN /(V _PN +Vz).

In a non-excitation type electromagnetic brake, the arc extinguishing time τ determines the time when braking starts. Therefore, by shortening the arc extinguishing time τ, high-speed braking can be achieved.

In addition, since the drive circuit 100A does not require a gate drive circuit for driving the transistor Tr3 or the transistor Tr4, it has the advantage that it can be configured to be simpler than the full-bridge circuit of FIG. 2(a).

(Embodiment 2) FIG. 5 is a circuit diagram of the drive circuit 100B according to the second embodiment. In the drive circuit 100B, the position of the Darlington circuit 112 is changed to be between the first output terminal OUT1 and the negative power supply line 104 .

FIG. 6 is an operation waveform diagram of the driving circuit 100B of FIG. 5 . Before time t ₀ , during the braking release period, the first transistor Tr1 and the second transistor Tr2 are turned on, generating the positive voltage V _PN of the positive power supply line 102 at the first output terminal OUT1 and generating the negative voltage at the second output terminal OUT2 The voltage of power line 104 (0V). At this time, the coil current _IL of the current amount I ₀ flows in the coil L1 in the right direction in the circuit diagram of FIG. 5 .

When a braking command is generated at time t ₀ , the first transistor Tr1 and the second transistor Tr2 of the drive circuit 100B are turned off. As a result, the coil current _IL starts to flow in the path of the Darlington circuit 112, the coil L1, and the second diode D2. At this time, the voltage of the first output terminal OUT1 becomes -(Vz+2×Vbe), and the voltage of the second output terminal OUT2 becomes V _PN . At this time, V _L ≈ V _PN +Vz is applied between both ends of the coil L1.

As in Embodiment 1, the coil current _IL after time t ₀ is expressed by equation (2) and decreases with time. Furthermore, the arc extinguishing time τ until the coil current _IL becomes 0 is expressed by equation (3).

In this way, according to Embodiment 2, the arc extinguishing time τ can also be shortened.

Modifications related to Embodiment 1 and Embodiment 2 will be described.

(Modification 1.1) As the first transistor Tr1 or the second transistor Tr2, a bipolar transistor, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), or a GaN-HEMT (High Electron Mobility Transistor) can be used. rate transistor) and other power transistors to replace IGBT.

(Modification 1.2) The structure of the Darlington circuit 112 is not limited to the circuit shown in the figure. In the embodiment, a two-stage Darlington circuit is shown, but it may be composed of three or more stages. In addition, the transistor Tr3 or the transistor Tr4 may be composed of FET. In this case, in the structure of FIG. 3 , a current path including a resistor or the like may be added between the gate as the control terminal of the Darlington circuit 112 and the positive power supply line 102 . Alternatively, in the structure of FIG. 5 , a current path including a resistor or the like may be added between the gate as the control terminal of the Darlington circuit 112 and the first output terminal OUT1 of the negative power supply line 104 .

(Modification 1.3) In FIG. 3 , a resistor or diode may be added in series with the Zener diode ZD1 between the second output terminal OUT2 and the control terminal of the Darlington circuit 112 . Similarly in FIG. 5 , a resistor or diode may be added in series with the Zener diode ZD1 between the negative power supply line 104 and the control terminal of the Darlington circuit 112 . Thereby, the amount of supercharging can be further increased.

(Modification 1.4) In Embodiment 1 and Embodiment 2, it is assumed that the coil L1 is an excitation coil of a non-excitation type electromagnetic brake, but the present invention can also be applied to an excitation type. In this case, the braking release time can be shortened by shortening the arc extinguishing time.

(Modification 1.5) The driving object of the drive circuit 100 is not limited to the excitation object of the electromagnetic brake. It can also be used to drive an electromagnetic clutch. Furthermore, it can be widely used to drive a load that only needs to flow a current in one direction. For example, the driving object of the driving circuit 100 may be a DC motor with a brush that rotates only in one direction. In this case, the DC motor can be rotated while the transistors Tr1 and Tr2 are on, and the DC motor can be stopped when they are turned off.

(Embodiment 3) FIG. 7 is a block diagram of a control system including a motor. Rectifier 10 rectifies AC voltage. The inverter 20 converts the DC voltage V _DC generated by the rectifier 10 into an AC voltage to drive the motor 2 .

The brake drive circuit 100 switches the excitation coil of the electromagnetic brake 4 between excitation (energization) and non-excitation (non-energization) to switch between release and braking.

FIG. 8 is a circuit diagram of the electromagnetic brake system 6 including the brake drive circuit 100 according to the third embodiment. The brake drive circuit 100 includes a positive power supply line 102 , a negative power supply line 104 , a full bridge circuit 110 , a current detection circuit 120 , a controller 130 , and a gate driver circuit 140 .

The power supply voltage V _PN is supplied between the positive power supply line 102 and the negative power supply line 104 . For example, the potential of the negative power supply line 104 is set to 0V. The full bridge circuit 110 is connected to the excitation coil L1 of the electromagnetic brake 4 . In this embodiment, the full bridge circuit 110 includes four arms A1 to A4. The upper arm A1 and the lower arm A3 form the leg on the first output terminal OUT1 side, and the upper arm A4 and the lower arm A2 form the leg on the second output terminal OUT2 side. In this embodiment, each arm A1 to A4 includes a power transistor and a flywheel diode (return diode).

The current detection circuit 120 detects the coil current _IL flowing through the excitation coil L1 and generates a current detection signal S2. The controller 130 generates a control signal S3 that instructs the power transistor of each arm A1 to A4 to be turned on (ON) or turned off (OFF) based on the excitation command S1 indicating the state of the electromagnetic brake 4 and the current detection signal S2. The gate driver circuit 140 drives the power transistors of each arm A1 to A4 based on the control signal S3.

In response to the excitation command S1 indicating brake release, the controller 130 starts driving the transistor pair of the diagonal arms A1 and A2 of the full bridge circuit 110 . Then, the controller 130 monitors the current detection signal S2, and when detecting a change in the coil current _IL caused by the start of movement of the armature, reduces the duty cycle of the transistor pair of the diagonal arms A1 and A2.

The method of detecting the fluctuation of the coil current _IL in the controller 130 is not particularly limited. For example, the controller 130 may include an analog comparator and compare the current detection signal S2 with a threshold value. Alternatively, the current detection signal can be input to a high-pass filter to extract spike-like changes.

The controller 130 can convert the current detection signal S2 into a digital value and perform equivalent processing through digital signal processing. Alternatively, the fluctuation of the coil current _IL can be detected through waveform matching.

The above is the structure of the brake drive circuit 100. Next, its operation will be described. FIG. 9(a) is an operation waveform diagram of the brake drive circuit 100 of FIG. 8 . FIG. 9(b) shows an operation waveform diagram of the brake drive circuit of the comparative technology.

Referring to FIG. 9(a) , the operation of the brake drive circuit 100 will be described. Before time _t0 , the excitation command S1 is inactive (low), the coil current _IL is zero, and the electromagnetic brake 4 is in the braking state. When the excitation command S1 is enabled (high) at time t ₀ , the controller 130 starts driving the transistor pair of the angular arms A1 and A2 . In this example, the duty ratio d1 immediately after the start of driving is 100% and is permanently turned on. Thereby, a driving voltage V _L that is almost equal to the power supply voltage V _PN is applied between both ends of the excitation coil L1. Then, when the coil current _IL increases, the force of the electromagnetic brake 4 gradually weakens. Then, when the armature starts moving at time t ₁ , a counter electromotive force is generated in the electromagnetic brake 4 and the coil current _IL temporarily decreases. This change is represented by a spike-shaped signal waveform in Figure 9(a). When the controller 130 detects the change in the coil current _IL , it reduces the duty cycle of the transistor pair of the diagonal arms A1 and A2 to a value d2 that is less than d1 (=100%). The effective value (average value) of the drive voltage V _L applied to the electromagnetic brake 4 after time t ₁ is V _L =V _PN ×d2. Thereby, the rise of the coil current _IL is suppressed, and the power consumption is reduced.

Next, refer to Figure 9(b). The advantages of the brake drive circuit 100 become clear through comparison with comparative technologies. In the comparison technique, when the excitation command S1 is enabled, the transistor pairs of the diagonal arms A1 and A2 are fixedly turned on.

In the comparative technique, in order to set the holding current after the brake is released to the same level as in the embodiment, the power supply voltage V _PN ' in the comparative technique must be designed to be lower than the power supply voltage V _PN in the embodiment. As a result, immediately after the excitation command S1 is made effective, the increase rate of the coil current _IL becomes slower, and the time _t2 until the brake is released becomes longer. On the other hand, in the embodiment, the brake release time can be shortened compared to the comparative technique.

Alternatively, when the brake release time in the comparative technique is set to be approximately the same as in the embodiment, the power supply voltage V _PN in the comparative technique may be set to the same voltage level as the power supply voltage V _PN in the embodiment. However, in the comparative technology, after the brake is released, the drive voltage V _L becomes equal to the power supply voltage V _PN , thus causing the coil current (holding current) after the brake is released to become large. On the other hand, in the embodiment, compared with the comparative technology, the holding current can be reduced and the power consumption can be reduced.

As described above, in this embodiment, the trade-off relationship between the brake release time and the holding current can be eliminated, and both a short release time and a small holding current can be achieved.

Next, modifications related to Embodiment 3 will be described.

(Modification 3.1) FIG. 10 is a circuit diagram of the brake drive circuit 100A of Modification 3.1. In this modification 3.1, the full bridge circuit 110A is a diagonal full bridge circuit, and the diagonal arms A3 and A4 are composed of diodes. Others are the same as Figure 8. Also in this modification, the same effect as that of the embodiment can be obtained.

(Modification 3.2) FIG. 11 is a circuit diagram of the full-bridge circuit 110B of modification 3.2. The full bridge circuit 110B includes a first transistor Tr1, a second transistor Tr2, a first diode D1, a Darlington circuit 112, and a Zener diode ZD1. The first transistor Tr1 and the second transistor Tr2 are the above-mentioned transistor pair of the diagonal arms A1 and A2. In addition, the first diode D1 corresponds to the arm A3, and the Darlington circuit 112 and the Zener diode ZD1 correspond to the arm A4.

The first transistor Tr1 is provided between the first output terminal OUT1 and the positive power supply line 102 . The first diode D1 is disposed between the first output terminal OUT1 and the negative power line 104 . The second transistor Tr2 is provided between the second output terminal OUT2 and the negative power supply line 104 . The first transistor Tr1 and the second transistor Tr2 are IGBTs (Insulated Gate Bipolar Transistors).

The Darlington circuit 112 is provided between the second output terminal OUT2 and the positive power line 102 . The Zener diode ZD1 is disposed between the gate (ie, the base) of the Darlington circuit 112 and the second output terminal OUT2.

The Darlington circuit 112 includes third and fourth transistors Tr3 and Tr4 which are NPN bipolar transistors and a resistor R1. The base of the third transistor Tr3 is connected to the anode of the Zener diode ZD1. The emitter of the fourth transistor Tr4 is connected to the positive power supply line 102, the collector is connected to the second output terminal OUT2, and the base is connected to the emitter of the third transistor Tr3. The resistor R1 is provided between the collector of the third transistor Tr3 and the second output terminal OUT2.

The above is the structure of the full-bridge circuit 110B of Modification 3.2. Even when this full bridge circuit 110B is used, the same effect as that of the embodiment can be obtained. Next, the operation of the brake drive circuit including the full bridge circuit 110B when applying braking will be described.

FIG. 12 is an operation waveform diagram of the full-bridge circuit 110B of FIG. 11 . Before time _t0 , during the brake release period, the first transistor Tr1 and the second transistor Tr2 are switching with the duty ratio d. The coil current _IL flows through the current amount I ₀ . In addition, although the voltages of the first output terminal OUT1 and the second output terminal OUT2 actually switch before time t ₀ , this is simplified in FIG. 12 .

At time t ₀ , when the excitation command S1 is deactivated (low) and a braking command is generated, the first transistor Tr1 and the second transistor Tr2 of the full bridge circuit 110B are turned off. As a result, the coil current _IL starts to flow in the path of the diode D1, the coil L1, and the Darlington circuit 112. At this time, the voltage of the first output terminal OUT1 becomes 0V, and the voltage of the second output terminal OUT2 becomes V _PN +Vz+2×Vbe. Vz is the Zener voltage of the Zener diode ZD1, and Vbe is the base-emitter voltage of the third transistor Tr3 and the fourth transistor Tr4. When Vbe≈0 is considered, the voltage of the second output terminal OUT2 is approximately V _PN +Vz. At this time, V _L ≈ V _PN +Vz is applied between both ends of the coil L1.

The coil current _IL after time t ₀ is expressed by equation (1) and decreases with time. The arc extinguishing time τ until the coil current _IL becomes 0 is expressed by equation (2).

In FIG. 12 , the operation when the diagonal bridge circuit 110A of FIG. 10 is used is represented by a one-dot chain line. The arc-extinguishing time τ' at this time is given by equation (3), and the arc-extinguishing time τ' is (V _PN +Vz)/V _PN times the arc-extinguishing time τ in Modification 3.2. In other words, according to Modification 3.2, the arc extinguishing time can be shortened to V _PN /(V _PN +Vz).

In a non-excitation type electromagnetic brake, the arc extinguishing time τ determines the time when braking starts. Therefore, by shortening the arc extinguishing time τ, high-speed braking can be achieved.

In addition, since the drive circuit 100B does not require a gate drive circuit for driving the transistor Tr3 or the transistor Tr4, it has the advantage that it can be configured to be simpler than the full-bridge circuit of FIG. 8 .

(Modification 3.3) FIG. 13 is a circuit diagram of the full-bridge circuit 110C of Modification 3.3. The full bridge circuit 110C includes a first transistor Tr1, a second transistor Tr2, a diode D2, a Darlington circuit 112, and a Zener diode ZD1. The first transistor Tr1 and the second transistor Tr2 are the above-mentioned transistor pair of the diagonal arms A1 and A2. In addition, the Darlington circuit 112 and the Zener diode ZD1 correspond to the arm A3, and the diode D2 corresponds to the arm A4.

The difference between Modification 3.3 and Modification 3.2 is that the position of the Darlington circuit 112 is changed to be between the first output terminal OUT1 and the negative power supply line 104 .

FIG. 14 is an operation waveform diagram of the full-bridge circuit 110C of FIG. 13 . Before time t ₀ , during the brake release period, the first transistor Tr1 and the second transistor Tr2 switch with the duty ratio d, and a current flows in the excitation coil L1 in the right direction in the circuit diagram of FIG. 13 Coil current _IL of quantity I ₀ . In addition, although the voltages of the first output terminal OUT1 and the second output terminal OUT2 actually switch before time t ₀ , this is simplified in FIG. 12 .

At time t ₀ , when the excitation command S1 is deactivated and a braking command is generated, the first transistor Tr1 and the second transistor Tr2 of the drive circuit 100B are turned off. As a result, the coil current _IL starts to flow in the path of the Darlington circuit 112, the coil L1, and the diode D2. At this time, the voltage of the first output terminal OUT1 becomes -(Vz+2×Vbe), and the voltage of the second output terminal OUT2 becomes V _PN . At this time, V _L ≈ V _PN +Vz is applied between both ends of the coil L1.

Like Modification 3.2, the coil current _IL after time t ₀ is expressed by equation (1) and decreases with time. Then, the arc extinguishing time τ until the coil current _IL becomes 0 is expressed by equation (2). As described above, in Modification 3.3, similarly to Modification 3.2, the arc extinguishing time τ can be shortened.

As the first transistor Tr1 or the second transistor Tr2, a bipolar transistor, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), or a GaN-HEMT (High Electron Mobility Transistor) can be used. rate transistor) and other power transistors to replace IGBT.

The structure of the Darlington circuit 112 is not limited to the circuit shown in the figure. In FIG. 11 or FIG. 13 , a two-stage Darlington circuit is shown, but it may be composed of three or more stages. In addition, the transistor Tr3 or the transistor Tr4 may be composed of FET. In this case, in the structure of FIG. 11 , a current path including a resistor or the like may be added between the gate as the control terminal of the Darlington circuit 112 and the positive power supply line 102 . Alternatively, in the structure of FIG. 13 , a current path including a resistor or the like may be added between the gate as the control terminal of the Darlington circuit 112 and the first output terminal OUT1 of the negative power supply line 104 .

In FIG. 11 , a resistor or diode may be added in series with the Zener diode ZD1 between the second output terminal OUT2 and the control terminal of the Darlington circuit 112 . Similarly in FIG. 13 , a resistor or diode may be added in series with the Zener diode ZD1 between the negative power supply line 104 and the control terminal of the Darlington circuit 112 . Thereby, the amount of supercharging can be further increased.

The disclosure or the present invention has been described based on the embodiments using specific words, but the embodiments only show one aspect of the principles and applications of the disclosure or the invention. The embodiments should not depart from the scope of the patent application. Many modifications and configuration changes are allowed within the scope of the stipulated idea of the present invention. [Industrial availability]

The invention relates to a driving circuit for an inductive load.

100:Drive circuit OUT1: The first output terminal OUT2: The second output terminal Tr1: first transistor Tr2: second transistor Tr3: The third transistor Tr4: The fourth transistor D1: first diode D2: Second diode 102: Positive power cord 104: Negative power cord 110: Darlington Circuit ZD1: Zener diode R1: Resistor

[Fig. 1] is a block diagram of a control system including a motor. [Fig. 2(a)] and [Fig. 2(b)] are circuit diagrams showing structural examples of the brake drive circuit. [Fig. 3] is a circuit diagram of the drive circuit according to Embodiment 1. [Fig. 4] is an operation waveform diagram of the drive circuit of Fig. 3. [Fig. 5] is a circuit diagram of a drive circuit according to Embodiment 2. [Fig. 6] is an operation waveform diagram of the drive circuit of Fig. 5. [Fig. 7] is a block diagram of a control system including a motor. [Fig. 8] is a circuit diagram of a brake drive circuit according to Embodiment 3. In [Fig. 9], Fig. 9(a) is an operation waveform diagram of the brake drive circuit of Fig. 8, and Fig. 9(b) is an operation waveform diagram of the brake drive circuit of the comparative art. [Fig. 10] is a circuit diagram of the brake drive circuit of Modification 3.1. [Figure 11] is a circuit diagram of the full-bridge circuit of Modification 3.2. [Fig. 12] is an operation waveform diagram of the full-bridge circuit of Fig. 11. [Figure 13] is a circuit diagram of the full-bridge circuit of Modification 3.3. [Fig. 14] is an operation waveform diagram of the full-bridge circuit of Fig. 13.

Claims (8)

A drive circuit, characterized in that it includes: a first output terminal and a second output terminal connected to an inductive load; a first transistor provided between the first output terminal and the positive power line; and a first transistor provided between the first output terminal and the positive power line; a first diode between the output terminal and the negative power supply line; a second transistor disposed between the second output terminal and the negative power supply line; a second transistor disposed between the second output terminal and the positive power supply line. Darlington circuit; and a Zener diode disposed between the control terminal of the Darlington circuit and the second output terminal; the Darlington circuit includes: a base and an anode of the Zener diode a connected third transistor; and a resistor connected to the collector of the aforementioned third transistor. A drive circuit, characterized in that it includes: a first output terminal and a second output terminal connected to an inductive load; a first transistor provided between the first output terminal and the positive power line; and a first transistor provided between the first output terminal and the positive power line; A Darlington circuit between the output terminal and the negative power line; a Zener diode disposed between the control terminal of the Darlington circuit and the first output terminal; a second transistor disposed between the second output terminal and the negative power supply line; and a second diode disposed between the second output terminal and the positive power supply line; the Darlington circuit includes: a third transistor with a base connected to the anode of the aforementioned Zener diode; and a resistor connected to the collector of the aforementioned third transistor. The drive circuit according to claim 1 or claim 2, wherein the Darlington circuit includes: a fourth transistor whose base is connected to the emitter of the third transistor. The drive circuit according to claim 1 or claim 2, wherein the inductive load is a coil of an electromagnetic brake. A brake drive circuit, characterized by comprising: a full-bridge circuit connected to an excitation coil of an electromagnetic brake; a current detection circuit that detects coil current flowing through the excitation coil; and a controller that responds to an excitation command , start driving the transistor pairs of the diagonal arms of the full-bridge circuit, and when detecting a change in the coil current caused by the start of movement of the armature, reduce the duty cycle of the transistor pairs of the diagonal arms. ;The aforementioned full-bridge circuit system includes: A first output terminal and a second output terminal connected to the excitation coil; a first transistor disposed between the first output terminal and the positive power supply line; a first transistor disposed between the first output terminal and the negative power supply line. a first diode; a second transistor disposed between the second output terminal and the negative power line; a Darlington circuit disposed between the second output terminal and the positive power line; and a Darlington circuit disposed between the Darlington A Zener diode between the control terminal and the second output terminal of the Darlington circuit; the aforementioned Darlington circuit includes: a third transistor whose base is connected to the anode of the aforementioned Zener diode; and the aforementioned third transistor. The resistor connected to the collector of the three transistors. A brake drive circuit, characterized by comprising: a full-bridge circuit connected to an excitation coil of an electromagnetic brake; a current detection circuit that detects coil current flowing through the excitation coil; and a controller that responds to an excitation command , start driving the transistor pairs of the diagonal arms of the full-bridge circuit, and when detecting a change in the coil current caused by the start of movement of the armature, reduce the duty cycle of the transistor pairs of the diagonal arms. ; The aforementioned full-bridge circuit includes: a first output terminal and a second output terminal connected to the aforementioned excitation coil; a first transistor provided between the aforementioned first output terminal and the positive power supply line; and a first transistor provided between the aforementioned first output terminal a Darlington circuit between the Darlington circuit and the negative power line; a Zener diode arranged between the control terminal of the Darlington circuit and the first output terminal; a Zener diode arranged between the second output terminal and the negative power line a second transistor between; and a diode disposed between the second output terminal and the positive power line; the Darlington circuit includes: a third circuit whose base is connected to the anode of the Zener diode. crystal; and a resistor connected to the collector of the third transistor. The brake driving circuit of claim 5 or claim 6, wherein the Darlington circuit includes a fourth transistor whose base is connected to the emitter of the third transistor. An electromagnetic braking system is characterized by comprising: an electromagnetic brake; and a driving circuit according to any one of claims 1 to 7 for driving the coil of the electromagnetic brake.

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