JP7445485B2 - Inductive load drive circuit and electromagnetic brake system - Google Patents

Description

The present invention relates to an inductive load drive circuit.

Electromagnetic brakes are widely used as a means for stopping rotation of a motor. Electromagnetic brakes are one type of mechanical brake. In a non-excitation operated electromagnetic brake, when the excitation coil is not energized, the armature is pressed against the brake hub by the spring coil, and the brake is in an activated state (holding state). When voltage is applied to the excitation coil, the electromagnet attracts the armature, opening the brake. Because of these characteristics, non-excitation-operated electromagnetic brakes are often used in applications where safety during emergencies and power outages is a priority.

FIG. 1 is a block diagram of a control system including a motor. Rectifier 10 rectifies the alternating current voltage. The inverter 20 converts the _DC voltage VDC generated by the rectifier 10 into an AC voltage, and drives the motor 2.

Electromagnetic brake 4 and brake drive circuit 40 form an electromagnetic brake system. The brake drive circuit 40 switches between opening and braking by switching the excitation coil of the electromagnetic brake 4 between excitation (energized) and de-energized (de-energized).

FIGS. 2A and 2B are circuit diagrams showing a configuration example of the brake drive circuit 40. FIG. The brake drive circuit 40 in FIG. 2(a) is a full bridge circuit including transistors Tr1 to Tr4. During the brake release (non-braking) period, the pair of transistors Tr1 and 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, a holding current _I0 is flowing through the exciting coil.

During braking, the brake drive circuit 40 turns on the pair of transistors Tr3 and Tr4, applies a voltage of opposite polarity to the excitation coil to the excitation coil, and extinguishes the electromagnetic brake.

The brake drive circuit 40 in FIG. 2(b) includes a diagonal bridge circuit including transistors Tr1 and Tr2 and diodes D1 and D2. During the brake release (non-braking) period, the pair of transistors Tr1 and 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, a holding current _I0 is flowing through the exciting coil.

When the electromagnetic brake is turned off, the transistors Tr1 and Tr2 are turned off. The current flowing through the exciting coil is regenerated via the diodes D1 and D2, and the electromagnetic brake is turned off.

Japanese Patent Application Publication No. 9-69435 Japanese Patent Application Publication No. 2018-43624

The brake drive circuit of FIG. 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 FIG. 2(b), the extinguishing time τ required for the holding current _I0 to decrease to 0 is given by equation (1) and is limited by the DC voltage _VPN .
τ=L/V _PN・I ₀ …(1)

Note that similar problems are not limited to drive circuits for excitation coils of electromagnetic brakes, but also apply to drive circuits for other inductive loads.

The present invention was made in such a situation, and one exemplary object of one aspect of the present invention is to provide a drive circuit that can reduce the current of an inductive load in a short time.

A drive circuit according to an aspect of the present invention includes a first output terminal and a second output terminal to which an inductive load is connected, a first transistor provided between the first output terminal and a positive power supply line, and a first output terminal. a first diode provided between the second output terminal and the negative power supply line, a second transistor provided between the second output terminal and the negative power supply line, a Darlington circuit provided between the second output terminal and the positive power supply line, and a Darlington circuit provided between the second output terminal and the positive power supply line; A Zener diode is provided between the control terminal of the circuit and the second output terminal.

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. can be done.

Another aspect of the invention is also a drive circuit. This drive circuit includes a first output terminal and a second output terminal to which an inductive load is connected, a first transistor provided between the first output terminal and a positive power supply line, and a first transistor provided between the first output terminal and a negative power supply line. a darlington circuit provided between the darlington circuit, a zener diode provided between the control terminal of the darlington circuit and the first output terminal, a second transistor provided between the second output terminal and the negative power supply line, and a second output terminal. A second diode provided between the positive power supply lines.

According to this aspect, a voltage lower than the voltage of the negative power supply line can be generated at the first 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. be able to.

The Darlington circuit may include a third transistor whose base is connected to the anode of the Zener diode, a fourth transistor whose base is connected to the emitter of the third transistor, and a resistor connected to the collector of the third transistor. good.

The inductive load may be a non-excited electromagnetic brake coil. This enables high-speed braking.

Note that arbitrary combinations of the above-mentioned constituent elements and mutual substitution of constituent elements and expressions of the present invention among methods, devices, systems, etc. are also effective as aspects of the present invention.

Furthermore, the description in this section (Means for Solving the Problems) does not describe all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. .

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

FIG. 2 is a block diagram of a control system including a motor. FIGS. 2A and 2B are circuit diagrams showing a configuration example of a brake drive circuit. 3 is a circuit diagram of a drive circuit according to Embodiment 1. FIG. 4 is an operation waveform diagram of the drive circuit of FIG. 3. FIG. 3 is a circuit diagram of a drive circuit according to a second embodiment. FIG. 6 is an operation waveform diagram of the drive circuit of FIG. 5. FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on preferred embodiments with reference to the drawings. Identical or equivalent components, members, and processes shown in each drawing are designated by the same reference numerals, and redundant explanations will be omitted as appropriate. Further, the embodiments are illustrative rather than limiting the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

FIG. 3 is a circuit diagram of the drive circuit 100A according to the first embodiment. The drive circuit 100A drives the coil L1, which is an inductive load. The type of inductive load is not limited, but may be, for example, an excitation coil for 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 110.

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 provided between the first output terminal OUT1 and the negative power supply 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 110 is provided between the second output terminal OUT2 and the positive power supply line 102. Zener diode ZD1 is provided between the gate (ie, base) of Darlington circuit 110 and second output terminal OUT2.

The Darlington circuit 110 includes a third transistor Tr3 and a fourth transistor 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, its collector is connected to the second output terminal OUT2, and its 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 configuration of the drive circuit 100A. Next, the operation of the electromagnetic brake system including the drive circuit 100A and the electromagnetic brake will be described assuming that the coil L1 is an excitation coil of a non-excited electromagnetic brake.

FIG. 4 is an operational waveform diagram of the drive circuit 100A of FIG. 3. Before time _t0 , there is a brake release period, the first transistor Tr1 and the second transistor Tr2 are turned on, the voltage _VPN of the positive power supply line 102 is generated at the first output terminal OUT1, and the second output The voltage (0V) of the negative power supply line 104 is generated at the terminal OUT2. At this time, a coil current I _L having a current amount I ₀ is flowing through the coil L1 in the right direction in the circuit diagram of FIG.

When a braking command is generated at time _t0 , the first transistor Tr1 and the second transistor Tr2 of the drive circuit 100A are turned off. Then, the coil current _IL begins to flow through the path of the first diode D1, the coil L1, and the Darlington circuit 110. At this time, the voltage at the first output terminal OUT1 becomes 0V, and the voltage at 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 approximated as V _PN +Vz. At this time, V _L ≈V _PN +Vz is applied between both ends of the coil L1.

The coil current I _L after time t ₀ is expressed by equation (2) and decreases with time.
I _L =I ₀ -∫(V _PN +Vz)/Ldt
=I ₀ - {(V _PN +Vz)/L}×t...(2)
The arc extinguishing time τ until the coil current I _L becomes 0 is expressed by equation (3).
τ=L・I ₀ /(V _PN +Vz) …(3)

In FIG. 4, the operation when the diagonal bridge circuit of FIG. 2(b) is used is shown by a dashed-dotted line. The arc extinction time τ' at this time is given by equation (1), and the arc extinction time τ' is (V _PN +Vz)/V _PN times the arc extinction 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 time at which braking starts is defined by the arc extinguishing time τ. Therefore, by shortening the arc extinction time τ, high-speed braking becomes possible.

Further, since the drive circuit 100A does not require a gate drive circuit for driving the transistors Tr3 and Tr4, it has the advantage that it can be configured more simply than the full bridge circuit of FIG. 2(a).

FIG. 5 is a circuit diagram of drive circuit 100B according to the second embodiment. In the drive circuit 100B, the position of the Darlington circuit 110 is changed between the first output terminal OUT1 and the negative power supply line 104.

FIG. 6 is an operational waveform diagram of the drive circuit 100B of FIG. 5. Before time _t0 , there is a brake release period, the first transistor Tr1 and the second transistor Tr2 are turned on, the voltage _VPN of the positive power supply line 102 is generated at the first output terminal OUT1, and the second output The voltage (0V) of the negative power supply line 104 is generated at the terminal OUT2. At this time, a coil current I _L having an amount of current I ₀ flows through the coil L1 in the right direction in the circuit diagram of FIG.

When a braking command is generated at time _t0 , the first transistor Tr1 and the second transistor Tr2 of the drive circuit 100B are turned off. Then, the coil current _IL begins to flow through the path of the Darlington circuit 110, the coil L1, and the second diode D2. At this time, the voltage at the first output terminal OUT1 becomes -(Vz+2×Vbe), and the voltage at the second output terminal OUT2 becomes _VPN . At this time, V _L ≈V _PN +Vz is applied between both ends of the coil L1.

As in the first embodiment, the coil current I _L after time t ₀ is expressed by equation (2) and decreases with time. The extinction time τ until the coil current I _L becomes 0 is expressed by equation (3).

In this way, the second embodiment can also shorten the arc extinguishing time τ.

The present invention has been described above based on the embodiments. Those skilled in the art will understand that this embodiment is merely an example, and that various modifications can be made to the combinations of these components and processing processes, and that such modifications are also within the scope of the present invention. be. Hereinafter, such modified examples will be explained.

(First modification)
As the first transistor Tr1 and the second transistor Tr2, a power transistor such as a bipolar transistor, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), or a GaN-HEMT (High Electron Mobility Transistor) can be used instead of the IGBT.

(Second modification)
The configuration of Darlington circuit 110 is not limited to the illustrated circuit. In the embodiment, a two-stage Darlington circuit is shown, but it may be configured with three or more stages. Furthermore, the transistors Tr3 and Tr4 may be configured with FETs. In this case, in the configuration of FIG. 3, a current path including a resistor or the like may be added between the gate, which is the control terminal of the Darlington circuit 110, and the positive power supply line 102. Alternatively, in the configuration of FIG. 5, a current path including a resistor or the like may be added between the gate, which is the control terminal of the Darlington circuit 110, and the first output terminal OUT1 of the negative power supply line 104.

(Third modification)
In FIG. 3, a resistor or a diode may be added between the second output terminal OUT2 and the control terminal of the Darlington circuit 110 in series with the Zener diode ZD1. The same applies to FIG. 5, and a resistor or diode may be added between the negative power supply line 104 and the control terminal of the Darlington circuit 110 in series with the Zener diode ZD1. This allows the amount of boost to be further increased.

(Fourth modification)
In the first and second embodiments, the coil L1 is an excitation coil of a non-excitation type electromagnetic brake, but the present invention is also applicable to an excitation type. In this case, by shortening the arc extinguishing time, the brake release time can be shortened.

(Fifth modification)
The driving target of the drive circuit 100 is not limited to the exciting target of an electromagnetic brake, but can also be used to drive an electromagnetic clutch, and can be widely applied to driving loads that only require current to flow in one direction. . For example, the object driven by the drive circuit 100 may be a brushed DC motor that rotates in only one direction. In this case, the DC motor can be rotated while the transistors Tr1 and Tr2 are on, and when they are turned off, the DC motor can be stopped.

Although the present invention has been described using specific words based on the embodiments, the embodiments merely illustrate one aspect of the principles and applications of the present invention, and the embodiments do not include the claims. Many modifications and changes in arrangement are possible without departing from the spirit of the invention as defined in scope.

100 Drive circuit OUT1 First output terminal OUT2 Second output terminal Tr1 First transistor Tr2 Second transistor Tr3 Third transistor Tr4 Fourth transistor D1 First diode D2 Second diode 102 Positive power supply line 104 Negative power supply line 110 Darlington circuit ZD1 Zener Diode R1 Resistor

Claims (4)

a first output terminal and a second output terminal to which an inductive load is connected;
a first transistor provided between the first output terminal and a positive power supply line;
a first diode provided between the first output terminal and a negative power supply line;
a second transistor provided between the second output terminal and the negative power supply line;
a Darlington circuit provided between the second output terminal and the positive power supply line;
a Zener diode provided between the control terminal of the Darlington circuit and the second output terminal;
Equipped with
The Darlington circuit is
a third transistor whose base is connected to the anode of the Zener diode;
a fourth transistor whose base is connected to the emitter of the third transistor;
a resistor connected to the collector of the third transistor;
A drive circuit comprising : a first output terminal and a second output terminal to which an inductive load is connected;
a first transistor provided between the first output terminal and a positive power supply line;
a Darlington circuit provided between the first output terminal and the negative power supply line;
a Zener diode provided between the control terminal of the Darlington circuit and the first output terminal;
a second transistor provided between the second output terminal and the negative power supply line;
a second diode provided between the second output terminal and the positive power supply line;
Equipped with
The Darlington circuit is
a third transistor whose base is connected to the anode of the Zener diode;
a fourth transistor whose base is connected to the emitter of the third transistor;
a resistor connected to the collector of the third transistor;
A drive circuit comprising : 3. The drive circuit according to claim 1, wherein the inductive load is a coil of an electromagnetic brake. electromagnetic brake,
The drive circuit according to any one of claims 1 to 3 , which drives a coil of the electromagnetic brake;
An electromagnetic brake system comprising:

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