JPH05161377A - Digital driver circuit - Google Patents

Abstract

PURPOSE:To reduce the motor speed by controlling an overcurrent with an overcurrent control means provided in a digital driver circuit, in which an overcurrent detected signal is generated, and a digital control signal is changed on the basis of the magnitude of the overcurrent when the revolution rate is sharply diminished. CONSTITUTION:A digital driver circuit comprises a comparator 3 for generating a PWM signal by comparing via an overcurrent control means 5 an output provided from a counter 2, which works on the basis of a clock signal 1, with a digital control signal 6 generated from a microcomputer, and a driving means 7 for driving a motor in response to the PWM signal. In this case, an overcurrent detected signal is not sent to the microcomputer, but the overcurrent control means 5 changes the digital control signal 6, and the comparator 3 generates the PWM signal so as to reduce the revolutions of the motor. Then, the overcurrent can be prevented. Consequently, the overcurrent control can be performed surely and instantaneously regardless of the state of the microcomputer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital driver circuit having an overcurrent protection function.

[0002]

2. Description of the Related Art FIG. 6 shows the configuration of a driver circuit used for conventional rotation control of a motor. Upon receiving a digital control signal from the microcomputer, the driver circuit receives a PWM (Pulse Width Module) for controlling the rotation of the motor.
rotation signal is output and transmitted to the driving means, thereby realizing rotation control of the motor.

Here, when the number of revolutions decreases from a predetermined number of revolutions in response to the control signal by the PWM signal, the counter electromotive force from the motor decreases and an overcurrent is generated in the driving means. In order to recover from this overcurrent state, in the conventional control, a signal indicating the overcurrent state is input to the microcomputer, and the PWM control signal from the microcomputer is changed so as to reduce the power supplied from the driving means to the motor. To do. By changing the signal from this microcomputer, P
Modify the WM signal to reduce overcurrent.

By the way, in the case of performing the overcurrent control, it is necessary to take an urgent countermeasure such as when the rotation speed of the motor is remarkably decreased, and it is necessary to control the current particularly quickly. However, when the performance of the microcomputer is low bit (6 bits, 8 bits, etc.), other processing requires time, and the microcomputer is not always in a state of being capable of coping with the overcurrent control. If the overcurrent control is not performed promptly in this way, the overcurrent will continue to flow to the motor forever, and the safety will be impaired. Further, as a general request, in order to reduce the load on the microcomputer, it has been required to provide the peripheral device with a control that can replace the microcomputer.

[0005]

As described above,
In the driver circuit that controls the rotation of the motor, when the number of rotations is significantly reduced by deviating from the normal operating state and an overcurrent state occurs, it may not be possible to quickly control the current depending on the state of the microcomputer. Control could not be performed quickly. An object of the present invention is to provide a digital driver circuit having a function of controlling overcurrent generated in a motor.

[0006]

According to the present invention, a counter for counting clock signals, a comparator for comparing the output of this counter with a control signal for controlling the number of rotations of a motor, and an output signal of this comparator. There is provided a digital driver circuit comprising drive means for driving a motor according to the above, and overcurrent control means for changing the control signal when an overcurrent occurs in the motor.

[0007]

The digital driver circuit of the present invention is characterized by including an overcurrent control means for changing the control signal for controlling the rotation of the motor when an overcurrent occurs in the motor. That is, when the motor rotation speed is significantly reduced and an overcurrent is generated from the driving means, the overcurrent control means changes the digital control signal according to the magnitude of the overcurrent to change the motor rotation speed. It has a function of controlling overcurrent so as to suppress it.

By providing such an overcurrent control means, even when an overcurrent is detected, the overcurrent control means can perform the overcurrent control independently of the microcomputer. There is no need for the microcomputer to process. Therefore, the burden on the motor control of the microcomputer can be reduced, and regardless of the state of the microcomputer, even if an overcurrent occurs, it can be quickly processed.

[0009]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a diagram showing a basic configuration of a digital driver circuit of the present invention. A counter 2 which operates with the clock signal 1 as a reference, a comparator 3 which compares the output of this counter with a digital control signal 6 provided via the overcurrent control means 5, and outputs a PWM signal, and a PWM
The drive means 7 drives the motor in response to the signal, and the overcurrent control means 5 changes the digital control signal when the motor generates an overcurrent.

The overcurrent generated by the driving means is detected by the overcurrent detecting means. The digital control signal is changed by the overcurrent detection signal detected here. Since the digital control signal is a signal for controlling the rotation of the motor,
By changing the control signal in the direction of decreasing the rotation speed,
A PWM signal is generated from the comparator based on the changed control signal to reduce the rotation speed of the motor. This avoids overcurrent conditions.

With this configuration, since the driver circuit can control the overcurrent of the motor without sending the overcurrent control signal to the microcomputer, the overcurrent control can be surely and quickly performed regardless of the state of the microcomputer. be able to. FIG. 2 shows an embodiment in which the digital driver circuit of the present invention and a motor driving means are combined.

First, with the clock signal 1 as a reference, an n-bit output is generated so that the output value is increased by counting with the counter 2. On the other hand, an n-bit digital control signal from the microcomputer is input to the comparator 3 via the input means 25. The comparator compares the n-bit output signal from the counter with the n-bit output signal from the input means 5 to generate a PWM signal according to the digital control signal from the microcomputer. By the PWM signal output from the comparator 3,
The drive means 7 controls the rotation of the motor.

Here, by the overcurrent detection means 4, the motor 8
Monitors the current flowing in to detect if an excessive current has flowed. That is, when the predetermined number of rotations cannot be obtained with respect to the control signal, the drive means 7 generates an overcurrent detection signal. When the overcurrent detection signal is larger than a predetermined value, the overcurrent detection means 4 generates an overcurrent control signal and feeds it back to the input means 5.

The digital control signal from the microcomputer is changed by this overcurrent control signal so that an appropriate control signal can be given to the driving means. In this way, the digital control signal can be changed without directly returning the overcurrent control signal to the microcomputer. FIG. 3 is a diagram showing the configuration of another embodiment of the present invention. In this embodiment, a specific example of the control when the overcurrent is detected by the overcurrent detection means will be described.

First, when the motor is rotating normally,
The digital control signal 6 (VS) is input to the input means 5 as n-bit serial data, and the input means 5 performs S / P conversion (serial / parallel conversion) 5 on the serial data.
After b, it is input to the comparator 3 via the n-bit shift register 5a. And PWM of comparator
The signal drives the motor through the driving means 7.

When an overcurrent occurs here, the overcurrent flows into the overcurrent control means, and the overcurrent detection signal of the overcurrent detection means 4 is input to the input means 5. Therefore, after the digital control signal 6 is converted into parallel data, the data of the n-bit shift register 5a is bit-shifted to the lower side by the above-mentioned overcurrent detection signal, and the digital value of the digital control signal is halved. As a result, the digital control signal is halved, and the PWM signal is output in the direction in which the rotation speed decreases, that is, the current flowing through the motor 8 decreases, and the overcurrent flowing through the motor is protected.

FIG. 4 is a diagram showing the configuration of another embodiment of the present invention. The operation of the digital driver circuit is basically the same as that of the circuit of FIG. Particularly, in this embodiment, a case where a plurality of digital control signals are provided will be described.

In this configuration, a plurality of digital control signals 6 '(VS1 to VSn) are provided in advance, and one predetermined digital control signal is input to the input means 5 in accordance with the rotation speed of the motor. A PWM signal corresponding to the selected digital control signal is output from the comparator, and the driving unit drives the motor.

When an overcurrent occurs here, the input means 5 receives the detection signal of the overcurrent detection means 4 and inputs at this time from the plurality of digital control signals 6 '(VS1 to VSn). A control signal having a digital value smaller than the control signal is selected from the selection means 5 '. The PW is adjusted so that the rotation speed of the motor 8 is reduced by the newly selected control signal.
An M signal is generated, which provides overcurrent protection. FIG. 5 shows an embodiment in which the digital driver circuit of the present invention is applied to control of a three-phase motor.

The digital control signal from the microcomputer is sent to the comparator through the input means, and the PWM signal from the comparator is input to the timing logic 19 of the driving means 7 and the gate circuits 17 and 18 are synchronized with the three-phase signals. Is applied to the drive elements 11 to 16 via the drive elements to control the supply of current to the motor 8.

When an overcurrent occurs, the overcurrent will flow to the motor and the drive elements 11 to 16. Therefore, the current detection resistance 10 converts the current into a voltage, and the overcurrent detection means 4 outputs a detection voltage. Detected as overcurrent.
When this overcurrent detection signal is given to the input means, the digital control signal for controlling the rotation speed of the motor is changed.

Also in this case, since the PWM signal can be generated so as to change the rotation speed of the motor by changing the digital control signal, it is possible to quickly control the overcurrent without the intervention of the microcomputer. Becomes

[0024]

According to the present invention, in the driver circuit for controlling the rotation of the motor, the digital driver circuit is provided with the overcurrent control function so that when the overcurrent state of the motor occurs, the intervention of the microcomputer is performed. Without this, overcurrent control can be performed quickly.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a digital driver circuit of the present invention.

FIG. 2 shows a digital driver circuit of one embodiment showing the principle of the present invention.

FIG. 3 shows a digital driver circuit according to another embodiment of the present invention.

FIG. 4 shows a digital driver circuit according to another embodiment of the present invention.

FIG. 5 shows a specific example using the present invention.

FIG. 6 is a diagram showing a conventional driver circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Clock signal 2 ... Counter 3 ... Comparator 4 ... Overcurrent detection means 5 ... Overcurrent control means 5a ... Shift register 5b ... Serial / parallel conversion 5c ... Selection means 6 ... Digital control signal 7 ... Driving means 8 ... Motor 10 ... Current detection resistance 11-16 ... Driving element 17-18 ... Gate circuit 19 ... Timing logic 25 ... Input means

Claims (2)

[Claims] 1. A counter for counting clock signals,
A comparator for comparing the output of this counter with a control signal for controlling the number of rotations of the motor, a drive means for driving the motor according to the output signal of the comparator, and the above-mentioned control when an overcurrent occurs in the motor. A digital driver circuit comprising an overcurrent control means for changing a signal to control an overcurrent. 2. The digital driver circuit according to claim 1, wherein the overcurrent control means is means for holding the control signal and changing the control signal when an overcurrent occurs in the motor. ..