JP2002315348A - Pwm-current controlled inductive load drive, control provided therewith, and method for driving inductive load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently suppress or prevent heat generation from a voice coil motor, when the voice coil motor 20 is in a stop with respect to a PWM-current controlled inductive load drive which drives and controls an electromagnetic motor, such as voice coil motor, by PWM current control, a control provided with the inductive load drive, and to provide a method for driving an inductive load. SOLUTION: By making control operation to switch the carrier frequency of the voice coil motor 20 at a stoppage to a value higher than the carrier frequency of the voice coil motor, when driving, the response characteristics of the voice coil motor 20 are maintained as desired, without increasing the size of the overall equipment, and heat generation from the voice coil motor 20 at stoppage is suppressed efficiently or prevented, without causing switching loss.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PWM current control type inductive load driving device (hereinafter, referred to as a driving device) for driving and controlling an electromagnetic motor such as a voice coil motor by PWM current control, and a control device including the driving device. The present invention relates to an inductive load driving method.

[0002]

2. Description of the Related Art A conventional driving device will be described with reference to FIGS.

[0003] This driving device has a full bridge circuit 10
, A voice coil motor 20 and a current sensor 30.

[0004] The full bridge circuit 10 is configured by connecting four switching elements 11 to 14 in full bridge.

[0005] Voice coil motor 20 and current sensor 30
Are both intermediate points 15, 16 of the full bridge circuit 10.
Connected in series with respect to each other.

[0006] Of the switching elements 11 to 14, a set of switching elements 11 and 14 are simultaneously turned on by a pulse voltage P1 shown in FIG. 6A, and a set of switching elements 12 and 13 is shown in FIG. ) Are simultaneously turned on by the pulse voltage P2 shown in FIG. These pulse voltages P1,
The width of P2 is controlled by a control unit (not shown) within one cycle T0 of the carrier frequency, so that the magnitude of the load current I flowing through the voice coil motor 20 is set and controlled.

In this case, a dead time td at which the switching elements 11 to 14 are simultaneously turned off when the switching elements of each group are turned on / off is set so that the switching elements 11 to 14 are not simultaneously turned on.

As shown in FIG. 6C, the load current I is such that the voice coil motor 20 is an inductive load and
Since the inductive load is driven by the pulse voltages P1 and P2, a transient phenomenon occurs at each switching,
It includes a current ripple Iripple that increases and decreases with respect to the average current Iave.

[0009]

By the way, the inventors of the present invention have conducted intensive studies to elucidate the cause of the above-mentioned driving device, since the voice coil motor 20 was generating heat when the voice coil motor 20 was stopped. It was found that heat was generated due to the large current ripple Iripple at the time.

Therefore, the present inventors have repeated studies for preventing or suppressing this heat generation as follows.

As one of them, by providing a coil 70 between the power supply + Vcc and the full bridge circuit 10 as shown in FIG. The overall size and weight increase.

As another one, voice coil motor 20
By setting the drive voltage to a low value, although a certain effect could be obtained in suppressing heat generation, the response characteristics when the voice coil motor 20 was driven decreased.

[0013] Various studies have been repeated in this way, but all have the above-mentioned problems.

Therefore, in the course of further study, when the carrier frequency was set to a high value, the heat generation when the voice coil motor 20 was stopped could be greatly suppressed, but only the driving characteristics of the voice coil motor 20 deteriorated. However, there is a problem that the switching loss increases.

Therefore, the present invention does not increase the size of the entire device, maintains the desired response characteristics for the voice coil motor, and does not reduce the switching loss. It is a common problem to be solved to efficiently suppress or prevent heat generation when the voice coil motor is stopped.

[0016]

(1) A PWM current control type inductive load driving device according to the present invention is configured such that each of an inductive load connected to an intermediate point of a full bridge circuit composed of a plurality of switching elements performs a switching operation. A PWM current control type inductive load driving device that controls a width of a pulse voltage applied to an element to turn on and off the element within one cycle of a carrier frequency to control a driving state and stop driving of the element, A control operation for switching the carrier frequency when the inductive load is stopped to be higher than the carrier frequency when driving is performed.

According to the present invention, the carrier frequency at the time of stopping the inductive load is set higher than that at the time of driving, so that the load current ripple at the time of stopping is suppressed small, so that the heat generation of the inductive load at the time of stopping is reduced. It can be suppressed. Further, by setting the carrier frequency at the time of driving to be low, it is possible to prevent a reduction in switching loss and to maintain a response characteristic of the inductive load. Furthermore, an external coil for suppressing heat generation of the inductive load at the time of stoppage is not required, and the size of the device can be reduced.

In this case, the carrier frequency at the time of driving only needs to be set lower than the carrier frequency at the time of stopping, and may be the same as the conventional one, or may be set lower to maintain or improve the response. Is also good.

Preferably, the present invention includes a detecting means for detecting a driving / stop state of the inductive load, and a control means for switching and controlling a carrier frequency in response to a detection input of the detecting means.

In the present invention, preferably, the inductive load is:
An electromagnetic motor.

(2) The control device of the present invention detects a full bridge circuit composed of a plurality of switching elements, an electromagnetic motor connected to an intermediate point of the full bridge circuit, and a drive / stop state of the electromagnetic motor. Detecting means, and control means for applying a pulse voltage to each switching element to turn them on and off to drive the electromagnetic motor by a PWM current control type, wherein the control means detects a pulse voltage applied to each of the switching elements. The width is controlled within one cycle of the carrier frequency to control the drive of the electromagnetic motor and the stop of the drive, and in response to the detection input of the detection means, the carrier frequency is set low when the electromagnetic motor is driven. When the operation is stopped, the carrier frequency is set high.

According to the present invention, the carrier frequency at the time of stopping the inductive load is set higher than that at the time of driving, so that the load current ripple at the time of stopping is suppressed small, so that the heat generation of the inductive load at the time of stopping is reduced. It can be suppressed. Further, by setting the carrier frequency at the time of driving to be low, it is possible to prevent a reduction in switching loss and to maintain a response characteristic of the inductive load. Furthermore, an external coil for suppressing heat generation of the inductive load at the time of stoppage is not required, and the size of the device can be reduced.

(3) In the PWM current control type inductive load driving method of the present invention, an inductive load connected to an intermediate point of a full bridge circuit including a plurality of switching elements is applied to each of the switching elements and applied to these switching elements. A PWM current control type inductive load driving method of controlling the width of a pulse voltage for turning on and off the power supply within one cycle of a carrier frequency to control the driving and the stop of the driving. The frequency is set low, and the carrier frequency is set high when the operation is stopped.

According to the present invention, the carrier frequency at the time of stopping the inductive load is set higher than that at the time of driving, so that the load current ripple at the time of stopping is suppressed small. As a result, the heat generation of the inductive load at the time of stopping is reduced. It can be suppressed. Further, by setting the carrier frequency at the time of driving to be low, it is possible to prevent a reduction in switching loss and to maintain a response characteristic of the inductive load. Furthermore, an external coil for suppressing heat generation of the inductive load at the time of stoppage is not required, and the size of the device can be reduced.

The components of the switching element, the detecting means, the inductive load, and the control means in the present invention are not limited to the embodiments, but may be any elements having the above functions. .

Further, in the claims of the present specification, it is reserved that a correction for changing the combination of the respective constituent elements and a correction for reducing the number of combinations are possible.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below based on embodiments shown in the drawings.

In this embodiment, a description will be given by applying the present invention to a voice coil motor as an inductive load. Further, the drive device of the present embodiment is incorporated in a control device that operates a controlled device such as a nozzle.

FIGS. 1 to 4 relate to an embodiment of the present invention, FIG. 1 is a circuit diagram of a driving device, FIGS. 2 and 3 are timing charts for explaining the operation of the driving device of FIG.
FIG. 4 is a waveform diagram of the load current when the voice coil motor is driven and stopped.

Referring to FIG. 1, 10 is a full bridge circuit, 20 is a voice coil motor, 30 is a current sensor, 40 is control means, and 50 is a controlled device.

The full-bridge circuit 10 is composed of switching elements 11 to 14 which are connected to each other in full-bridge.

Voice coil motor 20 and current sensor 30
Are serial connection parts 15, 1 of the switching elements 11 to 14.
It is connected in series between six, that is, at the midpoint.

As an example of the inductive load, the voice coil motor 20 is a motor that requires a high-speed response, such as a motor that does not require a high-speed response or a linear motor that has a small electric time constant.

The current sensor 30 serves as current detection means.
It is preferably constituted by CT, but is not limited to this, and any form of current measurement may be used.

The control means 40 comprises an A / D converter 41, a CP
It includes a U42, a memory 43, an input unit 44, and a pulse voltage generation circuit 45.

The A / D converter 41 is of the successive approximation type and has a well-known structure, so that its detailed circuit configuration is not shown and its detailed description is omitted.

The A / D converter 41 outputs a sampling (clock) pulse having a sampling frequency sufficiently higher than the PWM carrier frequency, for example, several to several tens of times by the CPU.
42, the output of the current sensor 30 is A / D-converted based on the sampling pulse and input to the CPU 42.

In this case, a sampling pulse inside the A / D converter 41 may be used.

The CPU 42 is composed of a microcomputer, controls input of a sampling pulse to the A / D converter 41, calculates an average value and an instantaneous value of a load current, and calculates a duty ratio of a pulse voltage based on the calculated value. It performs data input / output, various calculations, control, and output, which will be described later, such as calculations.

Note that the function of the A / D converter 41 is
2 and the A / D converter 41 may be omitted.

The memory 43 stores an operation program of the CPU 42 and other necessary data such as a PWM carrier frequency and a sampling frequency, and is composed of, for example, a ROM and a RAM.

The input section 44 is for inputting the contents of an external operation by the operator to the CPU 42 in the form of a digital signal, and is connected between the series connection sections 15 and 16 as the contents of the operation. Voice coil motor 20
The input operation is performed for the type of the information, the content of the feedback control, and the like.

The pulse voltage generating circuit 45 inputs a pulse voltage to each of the switch elements 11 to 14 in accordance with a control command from the CPU 42.

As described above, the full bridge circuit 10, the voice coil motor 20, the current sensor 30, and the control means 4
0 indicates that the control device is configured.

On the other hand, the controlled device 50 is controlled by the voice coil motor 20. For example,
This is a nozzle or the like that moves up and down in a printed circuit board mounting apparatus.

In the present embodiment, the duty ratio of the pulse width for turning on each of the switch elements 11 to 14 is controlled within one cycle of a predetermined PWM carrier frequency, so that the load flowing through the voice coil motor 20 is controlled. In controlling the magnitude of the current I, the current sensor 30
And the control means 40 sets the carrier frequency when the voice coil motor 20 is stopped to be higher than the carrier frequency when the voice coil motor 20 is driven, in response to the detection input. I have.

For this setting, the memory 43 stores the carrier frequency f1 when the voice coil motor 20 is driven.
And the carrier frequency f2 (> f1) at the time of stoppage are stored.

The CPU 42 supplies a required value to the voice coil motor 20 based on the current set value from the input unit 44 and the detection output of the current sensor 30 A / D converted by the A / D converter 41. Control is performed.

The CPU 42 determines the load current I to the voice coil motor 20 based on the detection input of the current sensor 30.
Is calculated, and the average current Iave is treated as a current for detecting the state of the voice coil motor 20.

The CPU 42 controls, for example, the current zero line where the average current Iave becomes zero to a plus side to rotate the voice coil motor 20 to one side to control the controlled device 50 to a required state. (For example, by raising the nozzle), the voice coil motor 20 is controlled to the minus side, and the voice coil motor 20 is rotated to the other side.
Control 0 to another state (for example, lower the nozzle).

As described above, the CPU 42 drives the voice coil motor 20 by controlling the average value current Iave of the load current I. When the CPU 42 is stopped, the carrier frequency is increased to suppress the ripple of the load current I to a small value. Thus, the heat generation of the voice coil motor 20 can be prevented.

Hereinafter, the operation when the voice coil motor 20 is driven and when it is stopped will be described separately. (1) When the voice coil motor 20 is driven (see FIG. 2):
2A and 2B show the state when the voice coil motor 20 is driven. FIG. 2A shows the waveform of the load current I, FIG. 2B shows the waveform of the pulse voltage P1 for the switching elements 11 and 14, and FIG. ) Shows the waveform of the pulse voltage P2 for the switching elements 12 and 13.

When the voice coil motor 20 is driven, the CPU 42 reads the low carrier frequency f1 from the memory 43, and outputs a control signal to the pulse voltage generation circuit 45 corresponding to one cycle T1 of the low carrier frequency f1. Thereby, the pulse voltage generation circuit 45 outputs pulse voltages P1 and P2 corresponding to the on / off duty of each of the switching elements 11 to 14 set by the control signal.

As a result, although the current ripple Iripple is large, the voice coil motor 20 is driven with high responsiveness. (2) When the voice coil motor 20 is stopped (see FIG. 3):
3 (a) shows the waveform of the load current I, FIG. 3 (b) shows the waveform of the pulse voltage P1 for the switching elements 11 and 14, and FIG. 3 (c). ) Shows the waveform of the pulse voltage P2 for the switching elements 12 and 13.

When the voice coil motor 20 is stopped, the CPU 42 reads the high carrier frequency f2 from the memory 43 and outputs a control signal to the pulse voltage generation circuit 45 corresponding to one cycle T2 of the high carrier frequency f2. Thereby, the pulse voltage generation circuit 45 outputs pulse voltages P1 and P2 corresponding to the on / off duty of each of the switching elements 11 to 14 set by the control signal.

As a result, the current ripple Iripple is reduced, and when the voice coil motor 20 is stopped, heat generation due to the current ripple Iripple is suppressed.

Although the waveform of the load current I is partially shown in FIGS. 2 and 3, it changes as a whole as shown in FIG. For example, the nozzle goes up in the area a, goes down in the area b, and stops at the point c.

As described above, according to this embodiment, the carrier frequency when the voice coil motor 20 is stopped is set to be higher than that when the voice coil motor 20 is driven. Is suppressed.

A case where the above embodiment is specifically applied will be described.

That is, when the resistance value of the voice coil motor 20 is 11.9Ω (400 μH, drive voltage 48 V, carrier frequency 40 kHz during driving), when the voice coil motor 20 is stopped (load current I zero [A] is set). The measured surface temperature of the voice coil motor 20 is as follows: when the carrier frequency at the stop is 40 kHz: 60 ° C. When the carrier frequency at the stop is 200 kHz: 42 ° C. When the carrier frequency is set higher at the stop, the voice As a result, the heat generation temperature of the coil motor 20 was greatly reduced.

The present invention is not limited to the above embodiment, and various applications and modifications are conceivable. (A) In the above embodiment, the voice coil motor 20 is used as the inductive load. However, the present invention is not limited to this, and another electromagnetic motor or another inductive load may be used. (B) In the above-described embodiment, the controlled device 50 is a nozzle that moves up and down in a printed circuit board mounting device.
It is not limited to this.

[0062]

As described above, according to the present invention, the desired response characteristics of the voice coil motor are maintained without increasing the size of the entire device, and the switching loss is reduced. , Heat generation when the voice coil motor is stopped can be efficiently suppressed or prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a PWM current control type inductive load driving device according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the driving device of FIG. 1;

FIG. 3 is a timing chart for explaining the operation of the driving device of FIG. 1;

FIG. 4 is a diagram showing a waveform of a load current of the voice coil motor of FIG. 1;

FIG. 5 is a circuit diagram of a conventional PWM current control type inductive load driving device.

6 is a timing chart for explaining the operation of the driving device of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Full bridge circuit 11-14 Switching element 20 Voice coil motor (inductive load) 30 Current sensor 40 Control means 50 Controlled apparatus

Continuation of the front page F term (reference) 5H007 AA04 BB06 BB11 CB04 DA03 DA05 DB01 DB12 DC02 DC04 EA02 EA08 EA09 FA14 FA18 GA08 5H570 BB03 HA06 HB16

Claims (5)

[Claims] 1. An inductive load connected to an intermediate point of a full bridge circuit including a plurality of switching elements, the width of a pulse voltage applied to each switching element to turn on and off the switching element within one cycle of a carrier frequency. What is claimed is: 1. A PWM current control type inductive load driving device for controlling the driving state and controlling the driving to stop, wherein the control operation switches a carrier frequency when the inductive load is stopped to be higher than a carrier frequency when driving. And a PWM current control type inductive load driving device. 2. The apparatus according to claim 1, further comprising: detecting means for detecting a drive / stop state of the inductive load; and control means for controlling switching of a carrier frequency in response to a detection input of the detecting means. Characteristic PWM current control type inductive load driving device. 3. The PWM current control type induction load driving device according to claim 1, wherein the induction load is an electromagnetic motor. 4. A full-bridge circuit comprising a plurality of switching elements, an electromagnetic motor connected to an intermediate point of the full-bridge circuit, detection means for detecting a driving / stop state of the electromagnetic motor, Control means for applying a pulse voltage to turn them on and off to drive the electromagnetic motor by a PWM current control type, wherein the control means sets the width of the pulse voltage applied to each of the switch elements to one cycle of a carrier frequency. While controlling the driving of the electromagnetic motor and the stop of its driving, in response to the detection input of the detection means, when driving the electromagnetic motor,
A control device for setting a low carrier frequency and setting a high carrier frequency when operation is stopped. 5. A pulse voltage applied to each switching element to turn on and off the inductive load connected to an intermediate point of a full bridge circuit including a plurality of switching elements within one cycle of a carrier frequency. A PWM current control type inductive load driving method for controlling the driving and stopping the driving, wherein the carrier frequency is set low when the inductive load is driven, and the carrier frequency is raised when the operation is stopped. Setting a PWM current control type inductive load driving method.