JP2003088170A - Energization control circuit for linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energization control circuit for a linear motor wherein radiation noise is reduced as compared with conventional cases and frequency can be increased. SOLUTION: In the energization control circuit for linear motor, smoothing circuits 7 and 8 are placed between a switch circuit 1 where two sets of switching elements Q1 and Q4, and Q2 and Q3 are alternately turned on and off to generate PWM pulses, and output terminals 4 and 5 with which a load 6 is connected. The smoothing circuits 7 and 8 are connected between the respective output terminals 4 and 5 and GND of the switch circuit 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor energization control circuit for controlling energization of a linear motor that converts electrical energy into linear mechanical energy.

[0002]

2. Description of the Related Art As one of such linear motors, a three-phase moving coil type brushless DC linear motor is used. In this linear motor, for example, as a stator, a plurality of field magnets are arranged in the moving direction of the mover so that adjacent magnetic poles have different polarities alternately, and the phase is shifted by 2π / 3 in electrical angle. It has a basic structure in which a phase coil is arranged to face a field magnet through a magnetic gap having a sinusoidal magnetic flux density distribution, and a Hall element is arranged in each coil. The Hall element detects the magnitude and direction of the magnetic flux of the field magnet, and applies a sinusoidal drive current having a magnitude and direction corresponding to the magnetic flux to each coil. As a result, currents having a phase difference of 120 degrees (2π / 3) are input to the coil, so that a constant thrust is obtained. As another brushless DC linear motor,
Movable magnet type is also used. Movable magnet type brushless D
The C linear motor detects a magnetic pole of a mover (magnet) by a hall element or a linear scale, magnetizes a stator (coil) to a predetermined polarity by a drive circuit, and linearly moves the mover (magnet). . However, when using Hall elements, the same number of Hall elements as coils are required, and the wiring becomes complicated. Therefore, a linear scale is generally used to simplify the wiring.

The linear motor is driven by inputting a direct current into an inverter circuit, performing pulse width modulation (PWM) at a switching frequency of several KHz to several tens KHz, and outputting a sine wave current to a movable coil. . Examples of conventional inverter circuits are shown in FIGS. 9 (a) and 9 (b).
Shown in. In both figures, a switching element Q1, Q2, Q3, Q4 connected to the DC power supply voltage Ei constitutes a bridge circuit, and an output terminal Vo1 of the switching elements Q1, Q2 and an output terminal Vo of the switching elements Q3, Q4.
A load 8 (moving coil) is connected between the two. According to this circuit configuration, the gate signals whose pulse widths and polarities are controlled are given to the switching elements Q1 and Q2 and the switching elements Q3 and Q4 to turn on / off the switching elements.
The off control is performed, and a predetermined sine wave current is output. Further, FIG. 9B shows the smoothing circuit 13 including the inductor L3 and the capacitor C3 connected between the output terminals of the circuit of FIG. 9A.

[0004]

In order to improve the performance of the linear motor, it is necessary to reduce the ripple of the current output from the inverter circuit and to improve the frequency characteristic. For that purpose, the inverter circuit is required. It is required to increase the switching frequency of the. However, Fig. 9 (a)
If a high frequency is attempted with this circuit configuration, a high frequency current will flow through the cable or load that connects the inverter circuit and the load, and there is the problem that noise radiating to the outside from the cable or load will occur. This radiant noise causes malfunction or damage of the device. According to the circuit configuration of FIG. 9B, the radiation noise between the output terminals can be reduced, but the radiation noise between the output terminals and GND cannot be removed. Therefore, it is an object of the present invention to provide a conduction control circuit for a linear motor, which can reduce radiation noise more than before and can control conduction at a high frequency.

[0005]

In order to achieve the above object, the inventor of the present invention has earnestly studied the reduction of radiation noise accompanying the higher frequency of a conventional PWM control circuit, and arrived at the present invention. That is, in the energization control circuit for a linear motor of the present invention, a smoothing circuit is provided between a switch circuit that generates a PWM pulse by alternately turning on and off a plurality of switching elements and an output terminal to which a load is connected. At the same time, the smoothing circuit is characterized in that it is connected between each output terminal and GND. In the linear motor energization control circuit of the present invention, the smoothing circuit can be formed by an inductor and a capacitor. According to the invention, P
A smoothing circuit is provided between the switch circuit for generating the WM pulse and the output terminal, and the smoothing circuit includes each output terminal and GND.
Since the output terminals are connected to each other, the voltage between the output terminals is smoothed with respect to the GND level, and radiation noise can be reduced even if each switch is controlled to be turned on and off at a high frequency.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The details of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing the principle of the energization control circuit for a linear motor of the present invention. The energization control circuit of the present invention has a P connected to the power supply voltage Ei via the smoothing capacitor C4.
It has a WM modulation switch circuit 1, a switch control circuit 2 that controls the driving of the switch circuit 1, and a feedback circuit 3 that supplies a control signal to the switch control circuit 2 via a current detector 9. The switch circuit 1 has four PWs.
The M modulation switches Q1, Q2, Q3 and Q4 are connected so as to form an H-type bridge circuit, and two sets of PWM modulation switches Q1, Q4 and Q2, Q3 are alternately turned on / off to form a single switch. The power supply is configured to pass an alternating current through a load 6 connected between the output terminals 4 and 5. That is, switch Q
By turning on 1 and Q4 (turning off switches Q2 and Q3), the current flows from the switch Q1 through the first output terminal 4 and the second output terminal 5 to the switch Q4, and turns on the switches Q2 and Q3 (switches). By turning off Q1 and Q4), current flows from the switch Q3 through the second output terminal 5 and the first output terminal 4 to the switch Q2. Particularly, in the present invention, smoothing circuits 7 and 8 are provided between the output terminals 4 and 5 to which the switch circuit 1 and the load 6 are connected, and the smoothing circuits 7 and 8 are connected between the output terminals 4 and 5 and GND. ing. As a result, the voltage between the output terminals is smoothed with respect to the GND level, and the generation of radiation noise can be reduced even if each switch is on / off controlled at a high frequency.

FIG. 2 is a diagram showing an embodiment of an energization control circuit for a linear motor according to the present invention. The power supply voltage Ei is connected to, for example, a switching regulator (not shown) that converts commercial alternating current into direct current. Switch circuit 1
Four PWM modulation switches (for example, NPN type transistors) Q1, Q2, Q3 and Q4 are connected so as to form an H-type bridge circuit, and two sets of PWM modulation switches Q1 are connected in the same manner as described in FIG. It is configured such that Q4 and Q2, Q3 are alternately turned on / off to allow an alternating current to flow through the load 6 connected between the output terminals 4 and 5. In the present invention, P
As a switch for WM modulation, in addition to the above transistors,
MOS field effect transistor (MOSFET) with high switching speed or insulated gate bipolar transistor (IBGT) with low power consumption in the gate part
Etc. can be used.

Bases of switches Q1 and Q2 and switch Q
In order to supply a control signal to the bases of Q3 and Q4 via the drive circuits 20 and 21, respectively, the drive circuits 20 and 2
1 is connected to the output terminal of the comparator 31. The (+) input terminal of the comparator 31 is connected to the output terminals of the error amplifiers 32 and 33 formed of operational amplifiers having a negative feedback loop, and the (-) input terminal of the comparator 31 is connected to the variable resistor 30 for adjusting the amplitude of the triangular wave. It is connected. The (+) input terminal and the (-) input terminal of the operational amplifier 33 are connected to the emitter sides of the switches Q2 and Q4, respectively. Also in the energization control circuit of FIG. 2, between the first output terminal 4 and GND and between the second output terminal 5 and GND.
And smoothing circuits 7 and 8 are connected between and. The smoothing circuit 7 includes an inductor L1 and a capacitor C1, and the smoothing circuit 8 includes an inductor L2 and a capacitor C2.

The operation of the energization control circuit shown in FIG. 2 will be described with reference to the timing chart of FIG. FIG. 3 is a timing chart when 50% amplitude modulation is performed. When the power supply voltage Ei is input, the PWM modulation switch Q1,
The switch Q4 and the switches Q2 and Q3 are alternately turned on and off in synchronization with each other at a predetermined frequency (fs). Here, the duty ratio D = Ta / Tb (Ta: time width, Tb: cycle)
Then, since the average value of the output voltage is proportional to the duty ratio D, the output voltage can be adjusted by controlling the time width Ta. Switching frequency (fs)
Is given by 1 / Tb, and is usually several KHz to several hundred KH.
It is set during z. As shown in FIG. 3, between t0 and t1, the duty ratio (D1) of the switch Q1 is equal to the duty ratio (D2) of the switch Q2 and the switch Q2.
The duty ratio (D3) of 3 becomes equal to the duty ratio (D4) of the switch Q4. t1-t2 and t2-t
The magnitude relationships of the duty ratios among the three are D1> D2 and D3 <D4. t3-t4, t4-t5 and t5-
The magnitude relationship of the duty ratio during t6 is D1 <D2 and D3> D4.

The output voltage between the output terminal 4 and GND is Vo
1, the output voltage between the output terminal 5 and GND is Vo2, and the output voltage between the output terminals 4 and 5 is Vo3, the voltage waveform between the output terminal 8 and GND and the output terminal 9 and GND between t0 and t6. A current having a voltage waveform obtained by synthesizing the voltage waveforms of (3) flows between the output terminals 4 and 5. Therefore, between t0 and t1, the duty ratio D1 of the switch Q1 and the duty ratio D2 of the switch Q2 have a relationship of D1 = D2, so that the output voltage (Vo1) is 1/2 the power supply voltage [1/2. E
i] stabilizes. When D1> D2, Vo1> 1/2
・ Ei, while when D1 <D2, Vo1 <1/2 ・
It becomes Ei.

On the other hand, the duty ratios of the switches Q3 and Q4 change in the opposite relationship to the switches Q1 and Q2. That is, when D1> D2, the duty ratio between t1-t2 and t3-t4 is D3 <D4, and when D1 <D2,
The duty ratio between t3-t4, t4-t5 and t5-t6 is D3> D4. Therefore, the voltage (Vo3 = Vo1 + Vo2) between the output terminals can be freely adjusted within the range from the GND level to the power supply voltage (Ei) by changing the duty ratio of the switch.
Moreover, since the smoothing circuit is inserted between the output terminals,
The voltage (Vo3) between the output terminals is smoothed with respect to the GND level, and even if the PWM modulation switch is on / off controlled at a high frequency, the generation of radiation noise can be reduced.

FIG. 4 is a timing chart when the energization control circuit of FIG. 2 performs 100% amplitude modulation. Also in this case, the output voltage between the output terminal 4 and GND is Vo1,
When the output voltage between the output terminal 5 and GND is Vo2 and the output voltage between the output terminals 4 and 5 is Vo3, the output terminal 4 and G
A current having a voltage waveform obtained by combining the voltage waveform between ND and the voltage waveform of the output terminal 5 and GND flows between the output terminals 4 and 5, and the duty ratio of the switch is controlled,
It can be seen that the output voltage can be adjusted. For example, t0-t
Since the duty ratio D1 of the switch Q1 and the duty ratio D2 of the switch Q2 are in the relationship of D1 = D2 = 0 between 1, the output voltage (Vo3) is 0, and then t1-t.
During the period of 5, D1> D2 (= 0), so Vo3 = Vo1, and after t5, since D1 (= 0) <D2, Vo3 = Vo2. On the other hand, the duty ratios of the switches Q3 and Q4 change in the opposite relationship to the switches Q1 and Q2.

FIG. 5 is a circuit diagram according to another embodiment of the present invention, and the same functional portions as those in FIG. 2 are designated by the same reference numerals. When the present invention is applied to the energization control circuit of the three-phase moving coil type brushless linear motor, the circuit configuration as shown in FIG. 5 is suitable. 6 switch circuits 1 (3 sets)
PWM modulation switches Q1, Q2, Q3, Q4, Q
5, Q6 are connected so as to form a bridge circuit, and are connected to respective loads (Y-shaped connected coils) 6U, 6V, 6W via output terminals 4U, 4V, 4W. Smoothing circuits 7U, 7V, 7W are connected between the switch circuit 1 and the output terminals 4U, 4V, 4W. PWM of each set
The modulation switch is driven by feedback circuits 3U, 3V, 3W and switch control circuits 20, 21, 22 via current detectors 9U, 9V, 9W. This control circuit also turns on and off the PWM modulation switches of each set alternately in the same manner as described with reference to FIG. 1, and outputs the output terminals 4U, 4V,
It is configured so that an alternating current flows through the loads 6U, 6V, and 6W that are respectively connected to 4W.

FIG. 6 is a block diagram of an energization control circuit for a linear motor according to another embodiment of the present invention. The switch circuit 1 includes two PWM modulation switches Q1 and Q2, and a load 6 is connected between the output terminals 4 and 5. A smoothing circuit 7 is connected between the switch circuit 1 and the output terminals 4 and 5. The PWM modulation switch includes a feedback circuit 3 and a switch control circuit 20 via a current detector 9.
Driven by. This energization control circuit is configured to turn on / off the PWM modulation switch so that an alternating current flows through the load 6 connected between the output terminals 4 and 5.

In order to clarify the effect of the present invention, the results of comparing the radiation noise and the voltage waveform of the energization control circuit of the present invention and the conventional energization control circuit will be described with reference to FIGS. The radiation noise is the input voltage (Ei) = DC2
4V, output is measured as 1A (1V) / L = 7mH,
In each figure, the vertical axis represents the noise level (25 dB / DIV) and the horizontal axis represents the frequency (10 MHz / DIV). In the energization control circuit of FIG. 2, the result of measuring the noise between the output terminals with an oscilloscope (FFT analysis) is shown in FIG. 7A, and the result of measuring the radiation noise between each output terminal and GND is shown in FIG.
It shows in (b). For comparison, the noise between the output terminals of the energization control circuit (without the smoothing circuit) of FIG. 9A is measured with an oscilloscope, and the result is shown in FIG.
The result of measuring the noise between D is shown in FIG. FIG. 11A shows the result of measuring the noise between the output terminals of the energization control circuit (smoothing circuit between the output terminals) of FIG. 9B with the oscilloscope, and the result of measuring the noise between the output terminals and GND. Is shown in FIG. From these noise measurement results, when the smoothing circuit is inserted between the output terminals, as compared with the case where there is no smoothing circuit and the case where the smoothing circuit is provided between the output terminals, the output terminals and the output terminals and the GND are It can be seen that noise can be reduced together. When the smoothing circuit is provided between the output terminals, the noise between the output terminals can be reduced, but the noise between each output terminal and GND is not reduced.

FIG. 8A shows the voltage waveform between the output terminals of the energization control circuit of the present invention, and FIG. 8B shows the voltage waveform between the output terminals. FIG. 9A for comparison
12A shows a voltage waveform between the output terminals of the energization control circuit (without a smoothing circuit) and FIG. 12B shows an enlarged view thereof. It can be seen from FIGS. 8 and 12 that the present invention can supply a current with a small ripple to the load.

[0017]

As described above, according to the present invention, it is possible to reduce the radiation noise due to the high switching frequency. Therefore, the high frequency characteristics are improved, the ripple of the output current is reduced, and a highly reliable linear motor conduction control circuit can be obtained.

[Brief description of drawings]

FIG. 1 is a principle diagram of an energization control circuit for a linear motor according to the present invention.

FIG. 2 is a block diagram of an energization control circuit for a linear motor according to an embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of the energization control circuit of FIG.

FIG. 4 is another example of an operation explanatory diagram of the energization control circuit of FIG.

FIG. 5 is a block diagram of an energization control circuit for a linear motor according to another embodiment of the present invention.

FIG. 6 is a block diagram of an energization control circuit for a linear motor according to another embodiment of the present invention.

7 is a diagram showing a result of measuring noise between output terminals in the energization control circuit of FIG. 2 [(a)] and a diagram showing a result of measuring noise between each output terminal and GND [(b)]. is there.

FIG. 8 is a diagram [(a)] showing a voltage waveform between the output terminals and a diagram [(b)] showing a voltage waveform between the output terminals in the energization control circuit of FIG. 2;

FIG. 9 is a diagram showing a conventional energization control circuit [(a),
(B)].

10A is a diagram showing a result of measuring noise between output terminals in the energization control circuit of FIG. 9A [A] and a diagram showing a result of measuring noise between each output terminal and GND. )].

FIG. 11 is a diagram showing the result of measuring the noise between the output terminals in the energization control circuit of FIG. 9 (b) [(a)] and the diagram showing the result of measuring the noise between each output terminal and GND. )].

FIG. 12 is a waveform diagram [(a)] between each output terminal and GND in the energization control circuit of FIG. 9 (a) and its enlarged view [(b)].

[Explanation of symbols]

1: PWM modulation circuit 2: Switch control circuit 3: Feedback circuits 4, 5, 4U, 4V, 4W: Output terminals 6, 6U, 6V, 6W: Loads 7, 8, 7U, 7V, 7W: Smoothing circuits 9, 9U , 9V, 9W: current detectors 20, 21, 22: drive circuit 30: variable resistor 31: comparators 32, 33: error amplifiers Q1, Q2, Q3, Q4, Q5, Q6: PWM modulation switches L1, L2, L3: inductors C1, C2, C3, C4, C5, C6: capacitors

Claims (2)

[Claims] 1. A smoothing circuit is provided between a switch circuit that generates a PWM pulse by alternately turning on and off a plurality of switch elements and an output terminal to which a load is connected, and the smoothing circuit has each output terminal. And a GND are connected between the linear motor energization control circuit. 2. The energization control circuit for a linear motor according to claim 1, wherein the smoothing circuit includes an inductor and a capacitor.