JPH0265693A - Motor driver circuit - Google Patents

Abstract

PURPOSE:To reduce in size a circuit and to decrease its cost by supplying a signal to the gates of a plurality of power control functional elements when the excess of a motor current is detected, thereby controlling currents flowing to the elements. CONSTITUTION:A command signal is input to a control logic circuit 6 to, for example, turn ON switches 14, 15 thereby to turn ON, power control Trs 10, 11 to supply a current IM to a motor 2. Further, switches 13, 16 are closed to turn ON Trs 9, 12 to supply a reverse current IM to the motor thereby to reversely rotate the motor 2. The current IM is supplied to the resistor 22 of current detecting means 5, a voltage drop VR is compared with a reference voltage Vref by a comparator 21. In case of VR>Vref, it is judged as being an overcurrent to turn ON a Tr 23. Then, diodes 18, 19 or 17, 20 are turned ON to turn OFF Trs 10, 11 or 9, 12, thereby stopping the motor 2. Thus, the power consumption of the circuit is deleted to reduce it in size and to decrease its cost.

Description

[Detailed description of the invention] A. Industrial application field Summary of B1 invention C6 Prior art [Figure 3 Problems that the D1 invention attempts to solve Means to solve E0 issues F. Example [Figure 1, Figure S2] 81 circuits [Figure 1] a-1, motor drive section a-1-a, control lo gic circuit power control circuit bias circuit a-1-C.

a-1-b.

a-2, Current detection circuit, operation C1 Application example [Figure 2] G1 Effect of the invention 3, Detailed explanation of the invention The motor drive circuit of the present invention will be described according to the following items (A, industrial application field). The invention relates to a novel motor drive circuit. 3 sheep
By limiting the motor current by biasing the motor's current control active element when the motor current exceeds a predetermined value during motor overload, the current can be limited without the need for a special current limiting circuit. can be performed with high precision, making it possible to miniaturize the circuit, save power, and reduce costs.In addition, it has become possible to effectively utilize active elements for power control, which normally only perform switching operations. The present invention aims to provide a new motor drive circuit.

(B. Summary of the Invention) The motor drive circuit of the present invention includes a plurality of power control active elements for motor control, bias means for controlling the power control active elements, and current detection means for detecting motor current. In the motor drive circuit, the bias means controls the current of the power control active element to limit the motor current when the motor current detected by the current detection means is equal to or higher than a predetermined value, thereby reducing the number of parts. It is possible to protect the motor and circuits and limit the torque by precisely limiting the motor current during overload with a PJ vehicle structure without causing a significant increase in power consumption, and also makes effective use of active elements for power control. It was designed to achieve this.

(C, Prior Art) [Figure 3] -M, in motor drive circuits, a method is often used to limit the torque of the motor or to limit the current flowing through the motor in order to protect the motor circuit.

For example, a fuse is inserted between the motor drive circuit and its power supply, or the power supply voltage applied to the motor drive circuit is controlled by detecting the motor current.

However, in the former case, if the -1 fuse blows, it will need to be replaced, resulting in a lack of reliability.In the latter case, if the power supply circuit is shared with other circuits, the power supply voltage will constantly change depending on the value of the motor current. Since the voltage fluctuates, there are disadvantages such as causing malfunctions of other circuits, and to avoid this, a dedicated power source for the motor drive circuit is required.

Therefore, as an example of a current limiting method for a motor drive circuit that improves these, the method shown in FIG. 3 is known.

A is a current limiting circuit inserted between the power supply and the motor drive circuit C. For example, it limits the current flowing from the power supply using transistors, FETs, etc. according to the voltage and current of the motor d used. It is provided for supplying the signal to the drive circuit C.

In addition, the drive circuit C includes four power transistors e,%
It consists of gates e2, e3, e4, and a control logic circuit f that sends a predetermined switching control signal to each gate in response to an external signal.

Therefore, when the motor d is overloaded, the motor current increases, but this is controlled by the current limiting circuit a so that it does not exceed a certain value.

(D. Problem to be Solved by the Invention) However, in the method described above, the power consumption of active elements such as transistors and their drive circuits increases due to the addition of a current limiting circuit, and the circuits also become complicated. There is a problem that it cannot pass through small devices.

Moreover, since the power transistors in the motor drive circuit only perform switching operations in the vehicle, it is difficult to say that these elements are fully utilized when driving around bends.

(E. Means for Solving the Problems) Therefore, in order to solve the above-mentioned problems, the motor drive circuit of the present invention includes a plurality of active elements for power control provided for controlling a motor, and a plurality of active elements for controlling the power. A motor drive circuit comprising a bias means for controlling a functional element and a current detection means for detecting a motor current. No. 13 is sent to the bias means to control the current flowing to the power control active element and limit the motor current.

Therefore, according to the present invention, there is no need for a current limiting circuit having a plurality of active elements, their drive circuits, etc., and current limiting can be performed without causing a significant increase in power consumption or the number of components. Lower power consumption, smaller size,
Cost reduction can be achieved.

Moreover, since these currents can be controlled by changing the on-resistance of the power control active element using the bias means, the active element can be used effectively.

(F. Embodiment) [Figures 1 and 2] The motor drive circuit of the present invention will be described below with reference to the attached drawings.

(a, Circuit) [FIG. 1] 1 shows an example of the circuit of the motor drive circuit of the present invention.

2 is a motor, and in this example, a normal brushed motor is used.

Reference numeral 3 denotes a motor drive unit having a current limiting function, and the terminals of the motor 2 described above are connected to the output terminals of the motor drive unit 3. Further, the motor drive unit 3 is connected to a power source 4 (the power source voltage is vs (V)), and electric power for the motor is supplied from this.

5 is a current detection circuit, which detects the current of the motor 2 (IM (
A). ) is detected and compared with a predetermined value,
The comparison result is sent to the motor drive unit 3 described above. Then, the current of the motor 2 is limited by a signal sent from the current detection circuit 5 to the motor drive section 3.

(a-1, Motor Drive Unit) The motor drive unit 3 includes a control logic circuit 6 that generates a predetermined control signal in response to an external signal, and a plurality of power supplies that operate in response to the control signals from the control logic circuit 6. A power control circuit 7 consisting of a transistor,
The bias circuit 8 is provided between the control logic circuit 6 and the power control circuit 7 and biases the power transistor of the power control circuit 7.

(a-1-a, Control Logic Circuit) The control logic circuit 6 is provided to decode an external signal, for example, a 2-bit signal from a microcomputer (not shown), and the decoded signal is sent to the power control circuit 7. It is used to control the forward rotation, reverse rotation, stop, and brake of the motor 2 via.

(a-1-b, power control circuit) The power control circuit 7 is composed of four power transistors, and the collectors of the power transistor 9 and the power transistor 10 are connected to the positive electrode of the power source 4,
The collectors of power transistor 11 and power transistor 12 are each connected in series to the emitter of power transistor 9.10, and power transistor 11.12
The emitter of is connected to the input terminal of the current detection circuit 5. One terminal of the motor 2 is connected between the power transistors 9.11 and the other terminal is connected between the power transistors 10.12, and each power is supplied from the control logic circuit 6 via the bias circuit 8. The forward/reverse direction, stop, and short brake are controlled by signals sent to the gates of the transistors. For example, power transistor 9.
When the power transistors 10 and 12 are on and the power transistors 10 and 11 are off, the motor 2 rotates in the normal direction.If the relationship is completely reversed, the motor 2 rotates in the reverse direction, and there is no signal from the control logic circuit 6, and all the power is turned off. If the transistor is in an off state, control is performed such that the motor 2 is stopped. Also, the power transistors 9 and 10 are in the on state (
The short brake is applied when the power transistors 11 and 12 are in the off state) or when the power transistors 11 and 12 are in the on state (the power transistors 9 and 10 are in the off state).

(a-1-c, bias circuit) 13.14.15.16 are active switching elements (represented simply by the symbol of a switch in the figure), and power transistors 9.10, II, 12 of the power control circuit 7 is provided between each gate resistor and the positive electrode of the power supply 4,
Each switching operation is performed independently by a control signal from the control logic circuit 6.

17, 18, 19, and 20 are diodes, each having its anode connected to the gate resistor of the power transistor 9, 10, 11, and 12, and its cathode connected to the output terminal of the current detection circuit 5.

The voltage drop (VR( V
). ) is input manually, and the reference voltage (
Let v raf (v). ) has been added.

Incidentally, this reference voltage V raf is determined by an abnormal load being applied while the motor 2 is rotating and the motor current IM increasing.
>Vraf is selected to have a predetermined safety factor to prevent damage to the motor 2.

23 is an NPN transistor with a common emitter, the base of which is connected to the output terminal of the comparator 21 via a resistor 24, and the collector connected to the cathodes of diodes 17, 18, 19, and 20 of the bias circuit 8. .

(a-2, current detection circuit)
(b. Operation) Reference numeral 21 denotes a comparator, and its non-inverting input terminal.The operation of the motor drive circuit 1 described above is based on the power transistor of the motor drive section 3 described above.
It will look like this:

First, when an overload is applied to the motor 2 while it is rotating, the motor current I. is input to the current detection circuit 5, and its comparator 2
1, it is determined that VR>V. Therefore, the transistor 23 is turned on by the signal H4g of the comparator 21, so that the power transistor 9
．． 10.11.12 On-resistance will change 0
For example, suppose now that the switch elements 13 and 16 of the bias circuit 8 are turned on by a signal from the control logic circuit 6, and the motor 2 is rotating in the normal direction while the power transistors 9 and 12 are turned on. .

Note that at this time, the transistor 23 is in an off state. In this state, a load is applied to motor 2 and the motor current is
2 increases and VR>V. , comparator 21
The output becomes an H signal and turns on the transistor 23, which acts to lower the bias voltage of the power transistors 9 and 12, so that the gate voltages of these drop and the on-resistance increases. In other words, the on-resistance of each power transistor 9.12 is R11, R+2,
If the coil resistance of the motor 2 is RM, it can be considered that series resistors R1, R, . ) is the degree.

In this way, in the motor drive circuit 1, the power transistors 9 and 10 are controlled by the bias circuit 8 when the motor is overloaded.
．． The motor current can be controlled by increasing the on-resistance of 11.12.

(c. Application example) [FIG. 2] Next, FIG. 2 shows an example of a video camera in which the motor drive circuit of the present invention is applied to its cassette loading mechanism.

In the figure, 25 is a video camera, 26 is its outer casing, and 27
is a photographic lens provided so as to protrude from the front surface of the outer casing 26.

A cover 28 is provided on the left side of the outer casing 26 so as to be openable and closable, and a portion 28a of the cover is made of a transparent material.

A cassette carrier 29 is provided to be movable up and down relative to the outer casing 26 by a motor 2 (not shown), and its upper end plate 3o forms a part of the top plate of the outer casing 26. The cassette carrier 29 also includes a reel stand 31.
a, 31b and other necessary members are provided.

32 is a small video tape cassette.

As shown in FIG. 2(A), the cassette carrier 29 is moved upward to protrude from the top plate of the outside [26], and the tape cassette 32 is placed on the cassette carrier 29 with the cover 28 open. Installing.

Therefore, as shown in FIG. 2(B), when the cover 28 is closed, a sensor (not shown) detects this, and the mode shifts to the cassette loading mode, and the motor 2 rotates forward to load the cassette carrier 29. It will be drawn into the outer casing 26.

During the operation in which the cassette carrier 29 is being drawn into the outer casing 26, if, for example, the operator's fingers or the like are caught between the upper end plate 30 of the cassette carrier 29 and the top plate of the outer casing 26, the cassette carrier 29 may no longer be pulled into the outer casing 26. Since the carrier 29 can no longer be drawn in, the load on the motor 2 increases, and therefore the motor current ■. increases, and the motor 2 and circuits are protected because the current is limited by the above-described operation.

(G. Effects of the Invention) As is clear from the above description, the motor drive circuit of the present invention has multiple power control functions provided for controlling the motor! ! 1 element, bias means for controlling the active element for power control, and current detection means for detecting the motor current, the current detection means detects the motor current, and the current detection means detects the motor current, and the current detection means detects the motor current, and the current detection means detects the motor current, and the current detection means detects the motor current, and the current detection means detects the motor current, and the current detection means detects the motor current, and the current detection means detects the motor current, and the current detection means detects the motor current. When the above condition occurs, a signal is sent to the bias means to control the current flowing through the power control active element, thereby limiting the motor current.

Therefore, according to the present invention, there is no need for a current limiting circuit having a plurality of active elements, their driving circuits, etc., and current limiting can be performed without causing a significant increase in power consumption or the number of parts. , reduction in circuit power consumption, miniaturization,
Cost reduction can be achieved.

Moreover, since these currents can be controlled by changing the on-resistance of the power control active element using the bias means, the active element can be used effectively.

It should be noted that the motor drive circuit of the present invention is not limited to the specific circuit form described above, and the scope of application is of course not limited to video cameras, but can be widely used.

Fig. 3 shows an example of the application to a camera cassette loading mechanism; (A) is a perspective view of the video camera before cassette loading, (B) is a perspective view of the video camera during cassette loading, and Fig. 3 is a conventional motor. FIG. 2 is a circuit diagram showing an example of a drive circuit.

Explanation of symbols 1...Motor drive circuit, 2...Motor, 5...
・Current detection means, 8...Bias means, 9.10.11.12...Active element for power control Applicant: Sony Corporation

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of the motor drive circuit of the present invention, and FIG. 2 is a circuit diagram showing an example of the motor drive circuit of the present invention.
---------1----------J circuit diagram Figure 1 Figure 2 (B)

Claims (1)

[Claims] A power control device comprising: a plurality of power control active elements provided to control a motor; bias means for controlling the power control active elements; and current detection means for detecting a current of the motor. A motor drive circuit in which a current detection means detects a motor current, and when this exceeds a predetermined value, sends a signal to a bias means to control the current flowing to an active element for power control, thereby limiting the motor current. A motor drive circuit characterized by: