JP2001136769A - Control device for dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a power source for a plurality of sets of DC motors using a single set of controller, even without using a sample and hold circuit in each power source. SOLUTION: Each output of a multiplexer circuit 8, provided between a switching power source 3 for driving a plurality of DC motors and one set of microcomputer 1 and a control input of each switching power source 3, are connected via an integrating capacitor C. A control signal for setting output voltage is output from the microcomputer 1 to each power unit 3, by switching the multiplexer circuit 8. Here, by setting amplitude of a pulse train of the output control signal and duty ratio so as to generate a prescribed control voltage by each switching power unit 3, the power unit 3 for a plurality of sets of the DC motors can e controlled using a single set of the microcomputer 1, even without having to use a sample and hold circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor control device.

[0002]

2. Description of the Related Art Speed control of a DC motor can be easily performed only by changing an applied voltage. Therefore, it is used in various fields as a drive source for microcomputer control.

[0003] In particular, DC brushless motors are used as fan motors for microcomputer-controlled freezers and refrigerators, for example, because they have a wide shift range, do not have commutator corrosion or brush wear, and do not require much maintenance. I have.

FIG. 9 shows the circuit. In this circuit, the microcomputer 1 detects the number of rotations of the DC brushless motor 2, controls the voltage of the switching power supply 3, and adjusts the speed to a constant value.

[0005]

However, when control is performed by the microcomputer as described above, there are the following problems. (1) Since the rise time of the microcomputer and the switching power supply at the time of turning on the power are different, an uncontrollable blank period is generated.

That is, the switching power supply starts oscillating immediately after the power is turned on and outputs a voltage. However, the microcomputer needs to read hardware and programs after the power is turned on. Can be done.

As one method for solving this problem, for example, it is conceivable to provide a reset circuit for generating an idle time sufficient for the microcomputer to start up, and to start up the switching power supply. It is difficult to complete the operation at the same time, and conversely, a state occurs in which the switching power supply cannot be activated even though the microcomputer is activated. (2) To control a plurality of power supplies by one microcomputer, a sample and hold circuit for storing a control signal for each power supply is required.

That is, some control microcomputers have a D / A conversion output capable of outputting a control signal as is well known. Conventionally, by connecting the output to a voltage control input of a power supply, the control microcomputer shown in FIG. As shown in the figure, the voltage is directly controlled, but when controlling the power supply more than the number of D / A conversion outputs, a multiplexer circuit for distributing the output in a time-sharing manner, and a sample and hold for holding the output. There is a problem that a circuit is required for each output. This sample &
The hold circuit naturally requires a circuit to be controlled, so that the cost is high, and there is a problem that as the number increases, the control becomes complicated.

[0009] Therefore, an object of the present invention is to firstly make it impossible to blank the control period at the time of turning on the power, and then to make it possible to control a plurality of power supplies without using a sample and hold circuit. It is.

[0010]

In order to solve the above problems, according to the present invention, a switching power supply connected to a DC motor has a terminal for limiting output, and a controller is connected to the switching power supply to connect a DC motor. In the control device of the DC motor for controlling the speed of
One of the input / output terminals of the three-terminal switch means having an input / output terminal and a control terminal is connected to the output limiting terminal of the switching power supply, and the other is connected to the one terminal when the three-terminal switch means is on. "H" or "L" so that the output limiting terminal of the switching power supply becomes active.
Level, and the control terminal of the three-terminal switch means is connected to a power supply so as to be turned on;
The control terminal is connected to the controller, and an ON / OFF circuit for turning off the three-terminal switch means by inputting a release signal from the controller is employed.

By employing such a configuration, when the power is turned on, the control terminal turns on the three-terminal switch means (eg, transistor, FET, relay, etc.), and activates the output limiting terminal of the control circuit of the switching power supply. To stop the output of the switching power supply. Thereafter, when the controller operates and outputs a release signal to the output control terminal, the three-terminal switch means is turned off, and the output voltage is applied from the switching power supply to the DC motor to inactivate the output limiting terminal of the switching power supply. Is done.

A multiplexer circuit is provided between a plurality of DC motor driving switching power supplies and a single controller, and each output of the multiplexer circuit is connected to a voltage setting input of each switching power supply via an integration capacitor. In addition, the input of the multiplexer circuit is connected to the controller, and the control signal for setting the output voltage is output from the controller to the respective power supply devices by switching the multiplexer circuit. At this time, the amplitude and the duty ratio of the pulse train of the output control signal are output. Can be adopted such that each switching power supply has a predetermined output voltage.

By employing such a configuration, the integration capacitors at each output of the multiplexer circuit can output a predetermined set voltage to the switching power supply.

At this time, by adopting a configuration in which a buffer circuit is provided between the integrating capacitor and each switching power supply, the input impedance of the control voltage input of the switching power supply as viewed from the capacitor is increased, and conversely, the control of the switching power supply is performed. Since the impedance of the capacitor as viewed from the voltage input can be reduced, the responsiveness and linearity of the control signal can be improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, as shown in FIG. 1, a plurality of DC brushless motors (hereinafter, referred to as DC motors) 2 are controlled by a single controller 1, and a driving switching power supply 3 is provided for each DC motor 2. Is provided.

In this embodiment, the DC motor 2 is a motor for a blower fan such as a freezer or a refrigerator.

As shown in FIG. 2, the driving switching power supply 3 is a power supply IC 4 for general-purpose PWM (pulse width modulation).
And a step-down type in which a freewheel diode 7 is provided in parallel between the switching transistor 5 and the reactor 6.

The power supply IC 4 includes a triangular wave generation circuit and a comparison circuit. For example, as shown in FIG.
A PWM output is output by comparing a slice level based on f with the set voltage V0 and a triangular wave oscillated by the internal oscillator.

Further, the power supply IC 4 has a dead time control terminal d for setting an upper limit of the on-time. By activating this terminal, oscillation can be regulated and the PWM output can be stopped. It has become.

Each of the driving switching power supplies 3 is shown in FIG.
Is connected to the controller 1 via a buffer circuit B, an integrating capacitor C, and a multiplexer circuit 8, as shown in FIG.

That is, as shown in FIG. 1, a multiplexer circuit 8 is provided between the switching power supply 3 for driving the DC motor and the controller 1, and the multiplexer circuit 8
Are connected to the respective outputs 9 and the inputs of the respective switching power supplies 3 via an integrating capacitor C and a buffer circuit B, respectively.

The controller 1 has a D / A conversion output 11
And a timer circuit, and a control microcomputer (hereinafter referred to as a microcomputer) 1 having a plurality of I / O ports 10 as shown in FIG.
As shown in the figure, by connecting the D / A conversion circuit output 11 to the input IN of the multiplexer circuit 8 and connecting the I / O port 10 to the select input 13 of the multiplexer circuit 8, the set voltage can be changed to the corresponding switching power supply. 3 can be output.

Further, the I / O port 10 "of the microcomputer 1
, A detection pulse from each DC motor 2 is input via the interface IF, and the speed of each motor 2 can be detected by an internal processing program.

The integrating capacitor C is connected in parallel to the multiplexer outputs a to n and the input of the switching power supply 3,
The output of the multiplexer circuit 8 can be held.

Further, a resistor R5 is connected in parallel to the integrating capacitor C, and discharges the charge of the integrating capacitor C with a predetermined time constant.

As shown in FIG. 1, the buffer circuit B is a voltage follower circuit having a gain of 1, a high input impedance, and a low output impedance.

This circuit includes a switching power supply 3
ON / O for controlling ON timing of
An FF circuit 14 is provided.

As shown in FIG. 4, the ON / OFF circuit 14 is a switch circuit combining pnp transistors Q1 and Q2 and an npn transistor Q3, and connects the collector and the emitter of the pnp transistor Q1 to the dead time control terminal d of the power supply IC4. Connect to built-in power supply terminal V1,
The base is connected to the connection point between the resistors R21 and R22.
At this time, since one end of the resistor R21 is connected to the built-in power supply terminal V1 of the IC4 and one end of the resistor R22 is grounded, the pnp transistor Q1 is turned off when the built-in power supply terminal V1 is turned off, and the built-in power supply terminal V1 is turned off. When it is on, it becomes active and turns on, and the voltage of the built-in power supply terminal V1 is applied to the dead time control terminal d. on the other hand,
The collector of the pnp transistor Q2 is connected to the connection point between the resistors R21 and R22. The emitter of the pnp transistor Q2 is connected to the built-in power supply terminal V of the power supply IC4.
The base b is connected to the connection point between the load resistances R23 and R24 of the collector of the npn transistor Q3 whose emitter is grounded. The base of the transistor Q3 is connected to the I / O port 10 'of the microcomputer 1. I have.

For this reason, the microcomputer 1 uses the transistor Q3
Is turned off, the transistor Q2 is turned off, and no current flows, so the potential at the connection point between the resistors R21 and R22 drops, and the transistor Q1 turns on. Then, power supply I
The voltage (3 volts or more) of the built-in power supply terminal V1 is applied to the dead time control terminal d of C4. here,
The dead time control terminal d is a terminal for determining the upper limit of the on-time of the PWM. Usually, when a voltage of 3 volts or more is applied, that is, when the "H" level is input, the on-time becomes 0, The power supply IC 4 stops operating.

On the other hand, when the microcomputer 1 turns on the transistor Q3, the transistor Q2 turns on, and a current flows to raise the potential at the connection point between the resistors R21 and R22.
Therefore, the transistor Q1 is turned off, and the power supply IC4
Dead time control terminal d and built-in power supply terminal V1
The voltage between the resistors R8 and R9 is applied between them. As a result, the upper limit of the on-time of the dead time control terminal d is determined by the time constants of R8 and C5 in FIG.

Incidentally, if the ON / OFF circuit 14 is used, the stopping of the rotating motor 2 can be easily performed. That is, when the motor 2 is to be stopped, the transistor Q3 is turned off.
F, transistor Q2 is turned off and Q1 is turned off.
Since it becomes N and the dead time control terminal d can be held at the “H” level, the output of the switching power supply 3 can be stopped and the motor 2 can be stopped.

Here, an example in which the ON / OFF circuit 14 is provided for each switching power supply 3 has been described, but the present invention is not limited to this, and one ON / OFF circuit 14 is provided.
It is obvious that the output of the switching power supply 3 may be connected to a plurality of switching power supplies 3 in parallel.

This embodiment is configured as described above, and its operation will be described next.

When the power supply is turned on, the power supply I
A voltage is applied to C4 and the microcomputer 1 simultaneously.

Therefore, the voltage of the power supply IC 4 gradually increases from 0V and reaches the operation start voltage. At this time,
The voltage of the built-in power supply terminal V1 of the power supply IC 4 is also gradually increasing, and the transistor Q1 of the ON / OFF circuit 14 connected to this terminal V1 is turned on before reaching the operation start voltage of the power supply IC 4. At this time, the microcomputer 1 has not reached the operation start voltage, the I / O port 10 'is inactive, the transistor Q3 is off, and the transistor Q2 is also off. As a result, the dead time control terminal d of the power supply IC 4 is maintained at the “H” level, so that the power supply IC 4 maintains the state in which the oscillation output is stopped.

On the other hand, the microcomputer 1 reads the program when the operation start voltage is reached, and when the reading is completed, the I / O port 1 connected to the ON / OFF circuit 14.
Activate 0 '.

When the I / O port 10 'is activated, the transistor Q3 of the ON / OFF circuit 14 is turned on and the transistor Q2 is turned on. Therefore, the transistor Q1 is turned off, and the dead time control terminal d of the power supply IC4 is turned off. It becomes "L" level. As a result, the power supply IC 4 operates to output a voltage from the switching power supply 3.

As described above, since the switching power supply 3 can be operated after the microcomputer 1 is started, no blank period is generated in the control.

When the switching power supply 3 is started, the microcomputer 1 switches the multiplexer outputs a to n as shown in FIG.
And outputs a pulse train having an amplitude and a duty ratio corresponding to the output voltage.

That is, as shown in FIG. 5, the pulse train is obtained by changing the output level of the D / A conversion output 11 of the microcomputer 1 and the duty ratio. The pulse period is T, the ON period is t _H , Assuming that the amplitude voltage is V, the output voltage Vc of the capacitor is Vc = V × t _H / T. As described above, since the output voltage can be set by changing the amplitude level and the duty ratio, the voltage of a plurality of power supplies can be controlled without using a sample and hold circuit.

At this time, the integration capacitor C is set to have a sufficiently large capacity so that a predetermined voltage can be maintained even when charging and discharging are repeated, and the time constant is set by the resistor R5 connected in parallel, thereby setting the period T. To output an accurate voltage.

This voltage is output to the power supply IC 4 of the switching power supply 3 via the buffer circuit B.
Assuming that there is no buffer circuit B as shown by the broken line in FIG. 6, the amplification degree of the amplifier of the internal circuit of the power supply IC 4 is reduced due to the resistor R5. Therefore, by providing the buffer circuit B, the power supply IC 4 and the resistor R5 are separated, and the input impedance viewed from the capacitor C is increased. Further, a resistor R6 is connected to the output side of the buffer circuit B.
By increasing the output impedance of the buffer circuit B as viewed from the power supply IC 4, a decrease in the amplification degree of the internal circuit of the power supply IC 4 is prevented, and the linearity is improved.

As described above, the plurality of switching power supplies 3 can be controlled without providing a sample and hold circuit.

FIG. 7 shows another embodiment of the ON / OFF circuit 14 as a second embodiment.

In this embodiment, the ON / OFF circuit 14 is applied to an insulation type DC motor control device using a high frequency transformer T, and the control circuit and the ON / OFF circuit 14 are constituted by photocouplers P1 and P2. ing.

That is, the comparator comp is connected to the photocoupler P1 connected to the power supply IC 4, the D / A conversion output 11 of the microcomputer 1 is input to one input of the comparator comp connected to the photocoupler P1, and the other is input. , The detection voltages of the detection resistors r1 and r2 are input, and a voltage setting signal is input.

On the other hand, in the photocoupler P2, one of the output terminals connected to the internal transistor q1 is connected to the dead time control terminal d of the power supply IC 4, and the other is connected to the built-in power supply terminal V1. The input terminal connected to the LED 15 of the photocoupler P2 is connected to the microcomputer 1
And the power port is connected to the power supply VD. When the power is turned on and the microcomputer 1 starts up, the output port becomes "L", the LED 15 is turned on, and the reference voltage is applied to the dead time control terminal d. For this reason, the switching power supply 3 holds the stopped state. When the microcomputer 1 starts up and sets the output port 10 'to "H", the dead time control terminal d becomes "L", so that the switching power supply 3 can output a predetermined voltage.

FIG. 8 shows a third embodiment.

In this embodiment, a multi-output PWM generator IC 20 is used.
Is a command from the microcomputer 1, and outputs a control signal (the same pulse train as described in the first embodiment) as shown in FIG. The output control signal is converted into a level signal by a low-pass filter (integrating capacitor) LPF and input to the power supply IC 4.

The other configuration and operation are the same as those of the first embodiment, and the description is omitted.

In the embodiment, the DC brushless motor has been described, but the present invention is not limited to this.
The present invention can be applied to all DC motors whose speed can be controlled by a DC voltage.

[0053]

The present invention is constructed as described above,
Since the / OFF circuit is provided, it is possible to prevent a blanking of the control period when the power is turned on.

Further, since the multiplexer circuit is switched so that the amplitude and the duty ratio of the pulse train of the control signal become the predetermined control voltage for each switching power supply, a plurality of power supplies can be controlled without using a sample and hold circuit. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment.

FIG. 2 is a block diagram of a switching power supply according to the first embodiment;

FIG. 3 is a diagram illustrating the operation of the first embodiment.

FIG. 4 is a circuit diagram of an output ON / OFF circuit according to the first embodiment;

FIG. 5 is a diagram illustrating the operation of the switching power supply according to the first embodiment;

FIG. 6 is an operation explanatory view of the first embodiment.

FIG. 7 is a block diagram of a second embodiment.

FIG. 8 is a block diagram of a third embodiment.

FIG. 9 is a block diagram of a conventional example.

FIG. 10 is a block diagram of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 microcomputer 2 DC brushless motor 3 switching power supply 4 power supply IC 8 multiplexer circuit 9 multiplexer output 10 I / O port 11 D / A converter output 12 multiplexer input 13 select input 14 output ON / OFF circuit B buffer circuit C integration capacitor P1 photo Coupler d Dead time controller V1 Built-in power supply terminal

Claims (3)

[Claims] A switching power supply connected to a DC motor has a terminal for limiting output, and a controller for connecting a controller to the switching power supply to control the speed of the DC motor. One of the input / output terminals of the three-terminal switch means having an input / output terminal and a control terminal is connected to the output limiting terminal, and the other of the switching power supply connected to the one terminal while the three-terminal switch means is on. "H" or "L" so that the output limit terminal is active
Level, and the control terminal of the three-terminal switch means is connected to a power supply so as to be turned on;
A control device for a DC motor, comprising: an ON / OFF circuit that connects the control terminal to the controller and inputs a release signal from the controller to turn off a three-terminal switch. 2. A switching circuit for driving a plurality of DC motors and a multiplexer circuit provided between a single controller, and each output of the multiplexer circuit is connected to a voltage setting input of each switching power supply via an integration capacitor. In addition, the input of the multiplexer circuit is connected to the controller, and the control signal for setting the output voltage is output from the controller to the respective power supply devices by switching the multiplexer circuit. At this time, the amplitude and the duty ratio of the pulse train of the output control signal are output. Wherein each switching power supply has a predetermined output voltage. 3. The DC motor control device according to claim 2, wherein a buffer circuit is provided between the integration capacitor and each switching power supply.