JPS6142288A - Drive circuit of brushless motor - Google Patents

Abstract

PURPOSE:To reduce the capacity of a filter capacitor and to decrease a space and a cost by combining soft switching signals smoothened at displacing curve from the output signal of position detecting means, logarithmically compressing it, adding it to a drive circuit. CONSTITUTION:Hall elements Hu-Hm generate output signals of 3 phases in response to relative positional relation between a stator and a rotor, and the output signals are applied through amplifiers A1-A3 to a signal composite circuit SSM. This circuit SSM logarithmically compresses the output signals of the amplifiers A1-A3 to combine the soft switching signals of rectangular pulse shape smoothened at displacing curve. This soft switching signal is again logarithmically compressed by amplifiers A5, A6, applied to the bases of power transistors Q31-Q36 for forming a drive circuit through upper and lower stage predrivers PD1, PD2 to flow currents to drive coils Lu-Lw.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a drive circuit for a brushless motor.

BACKGROUND OF THE INVENTION As a drive circuit for a conventional brushless motor, a three-phase 1200 switching current supply system as shown in FIG. 10 is known. In this system, the Hall element Hu.

Hv and Hw generate three-phase sine wave-like output signals as shown in FIG. This output signal is applied to the signal synthesis circuit SM via amplifiers A1 to A3. The signal synthesis circuit SM is digitally configured with a logic circuit, detects a zero cross point where the output signals of the amplifiers A1 to A3 become OV, and outputs three-phase rectangular wave pulses. Power transistors Q31 to Q36 constitute a final stage driver, and the signal synthesis circuit SM
The three-phase drive coil L is driven by three-phase rectangular wave pulses from
u +LV, LWK As shown in FIG. 11, a current is applied to rotate the rotor. The current flowing through the drive coils Lu, Lv, and Lw is detected by a current detection resistor R8, and the rotational speed of the rotor is detected by a speed detector. The current feedback amplifier A4 uses a differential amplifier A41 to extract the difference between the output voltage VcTL of the speed detector and the speed command voltage VREF.
Furthermore, the difference between the voltage and the voltage of the differential current detection resistor R8 is extracted by the differential amplifier A42. The output signal voltage changes under the control of the output signal of the signal synthesis circuit SM differential amplifier A42, and the filter capacitors Cu, Cv, C
w is a capacitor of at least 1077F or more provided to reduce mechanical noise and electrical noise generated due to sudden changes in current when switching the energization of the drive coils L u and L v + L w.

Invention t≦Problem to be Solved In the three-phase 120° switching energization method described above, the signal synthesis circuit SM synthesizes three-phase rectangular wave pulses from the output signals of the amplifiers A1 to A3 and applies them to the bases of the power transistors Q31 to Q36. By this, the drive coils Lu, Lv, Lw
Since the energization is switched, the drive coil L at the time of the energization switching is
Filter capacitors cu, Cv, and Cw of 10 μF or more are essential to reduce noise caused by sudden changes in the currents of u, Lv, and Lw.
It is disadvantageous in terms of cost. Also, during high-speed rotation, the filter capacitor Cu.

The energy consumption of CV and CW increases, making them virtually unusable. Furthermore, filter capacitors Cu, Cv.

Mechanical noise countermeasures using CW have little effect on motors other than those with cores, and are a major bottleneck.

Means for Solving the Problems The present invention provides a stator having an m-phase drive coil, a rotor having magnetic poles, and an m-phase sine wave pattern according to the relative positional relationship between the stator and the rotor. position detecting means for obtaining an output signal; and a signal for logarithmically compressing the output signal of the position detecting means, shaping the waveform into a rectangular wave pulse with a waveformed inflection point, and synthesizing it into an m-phase soft switching signal. a synthesis circuit;
The present invention includes an amplifier circuit that logarithmically compresses the output signal of the signal synthesis circuit again, and a drive circuit that uses the output signal of the amplifier circuit to control energization of the m-phase drive coil.

The action position detection means generates an m-phase sine wave-like output signal according to the relative positional relationship between the stator and the rotor, and this output signal is logarithmically compressed by a signal synthesis circuit to smooth the inflection point. The waveform is shaped into a rectangular wave pulse and synthesized into an m-phase soft switching signal. The output signal of the signal synthesis circuit is again logarithmically compressed by the amplifier circuit, and the drive circuit uses the output signal of the amplifier circuit to control energization of the m-phase drive coil.

Embodiment FIG. 1 shows an embodiment of the present invention, and this embodiment is an example of a three-sensor, three-phase, 120° switching energization system.

The Hall element Hu I HV I Hw is a three-phase drive coil Lu.

A three-phase sine wave-like output signal as shown in FIG. 2 is generated depending on the relative positional relationship between the stator having Lv and Lw and the rotor having magnetic poles, and this output signal is transmitted to amplifiers A1 to A1.
3 to the signal synthesis circuit SSM. The signal synthesis circuit SSM uses 100% of the output signals of the amplifiers A1 to A3 to synthesize a three-phase rectangular wave pulse-like soft switching signal in an analog manner.
The output signal of is logarithmically compressed to synthesize a rectangular wave pulse-like soft switching signal with blunted inflection points. This soft switching signal is transmitted through an amplifier circuit A consisting of three differential multipliers.
5. Logarithmically compressed again by A6, upper predriver P
By applying current to the drive coils l, u, lv, j, and w as shown in FIG. The rotor rotates. The current flowing through the drive coils Lu, LV, and LW is for current detection.
It is detected by resistor R8, and the rotational speed of the rotor is detected by a speed detector.

The current feedback amplifier A4 uses a differential amplifier A4 to extract the difference between the output voltage VCTL of the speed detector and the speed command voltage VIP as a current command signal, and outputs the difference between this and the voltage of the current detection resistor R8 as a differential signal. It is taken out by amplifier A42. The voltage at the midpoint of the drive coils Lu, Lv+Lw is detected by a coil midpoint detector. Coil midpoint feedback amplifier A7
is the detection voltage of the coil midpoint detector and the reference voltage (power supply voltage V
'A)(!: of cc is compared by differential amplifiers A71 and A72, and the output is multiplied by the output signal of current feedback amplifier A4 by multipliers Ml and M2. Amplifier circuits A5 and A6 are multipliers M
The output signal voltage changes under the control of the output signals 1, 1 and 2, and the speed of the rotor is controlled.

Feedback control of coil current and coil midpoint voltage feedback control are performed. The filter capacitors CU, (::V, (:W) are provided to reduce noise caused by current changes when switching the energization of the drive coils Lu, Lv, and Lw. The drive coil L u +
L ■ + L ''' energization control is carried out, so 0.
A capacitor of about 1 μF is used. Therefore, it is advantageous in terms of space and cost, and the energy consumption of the Nemo filter capacitor Cur Cv + Cw can be reduced during high-speed rotation, and mechanical noise can also be reduced for motors other than those with a core.

FIG. 3 specifically shows this embodiment, and in the figure R
1 to R30 are resistors, Q1 to Q62 are transistors, D1
~DIO is a diode, and 01~C5 are capacitors. Note that the capacitors 01 to C3 are the filter capacitors Cu, Cv, ('w) of about 0.1 μF.

In amplifiers A1 to A3 and signal synthesis circuit SSM, μ
When the output voltage of the phase Hall element Hu is Vu, the collector current IC2゜Ic of the transistors fi Q2 and Q3 is
a is expressed by the following formula.

However, l is the charge of the electron, k is Portsma/constant, and T is the absolute temperature. Here, if 1vul>100mV, the respective collector currents IC2 and Ica have waveforms as shown in FIG. 4, and are subjected to logarithmic compression. ■ Phase.

The output voltages of the W-phase Hall elements HV and HW are also the same as the collector currents I of the transistors Q4 to Q, which are also logarithmically compressed.
C4 to Ic7, and these collector currents IC2
~3-phase soft switching signals IC2, 5 shifted by 120 degrees from IC7; LC! 4,7,Ic6. s is synthesized by the following equation.

IC2,5= IC2+ Ic5 IC4,7= IOA + IC7 IO6,8= IC6+ ICI+ The pattern of this synthesis is shown in FIG. Hall element Hu,
Even if fluctuations, interphase differences, etc. occur in the output of l(v, l(w), the distortion of the composite currents Ics,a, Ic4,7, IC6,8 is small.The composite currents Ic2,5, IC4,7, Ic6...
a is a voltage VR12 to VR14 due to resistors R12 to R14.
is converted into and transmitted to the subsequent stage.

Amplification circuit A5. A6 is transistor Q16~Q18゜Q
It is composed of three differential multipliers consisting of ll to Q15, and by logarithmically compressing the output signal voltage VR12γVR14 of the previous stage again, the variation in the three-phase soft switching signal due to the circuit error of the previous stage is suppressed.

Allocates signals to the lower predrivers PDI, , PD2. This situation is shown in FIG. Here, transistors Q12 to Q18. IC the collector current of Q62! 12~
■018 r Set to Ic62. Upper and lower drive signals (upper.

The magnitude of the output signal to the lower stage predriver PDI and PD2 is IC! 62 + IC12, and this IC62 + IC12 is controlled by the coil midpoint feedback amplifier A7, so that the gain difference between the upper stage driver and the lower stage driver is always kept at zero.

The upper and lower predrivers PDI, PD2 and power transistors Q31 to Q36 are transistors Q19 to Q36,
This is a current amplification section composed of resistors R18 to R20 and diodes D1 to D3, and the output current IC! la~
IC! 1B is amplified and supplied to drive coils lu, Lv, and 1w.

The current feedback amplifier A4 is composed of transistors Q37 to Q52 and resistors R21 to R24, and has a speed command voltage VREF.
A current command signal is created by taking the difference between the current command signal and the output voltage VCTL of the speed detector, and the difference between this and the detection voltage of the current detection resistor R25 (R3) is taken and transmitted to the subsequent stage.

The coil midpoint detector CD is set to 3 by diodes D5 to D7.
Only the highest value of the phase drive coil Lu, Lv, Lw voltage waveform is detected, and only the lowest value of the 3-phase drive coil Lu, Lv, Lw voltage waveform is detected by diodes D8 to DIO, and the highest value is detected by resistors R29 and R30. Drive coil Lu by determining the value of the bar between the value and the lowest value.

Obtain the midpoint voltage of LV and LW. This situation is shown in FIG.

The coil midpoint feedback amplifier A7 uses the base voltage of the transistor Q57 as a reference voltage, and uses the base voltage of the transistor Q58 as the drive coil midpoint voltage. As mentioned above, when the gain balance of the lower stage current amplification section is balanced, the midpoint voltage of the drive coil matches the reference voltage, and the transistor Q57.
Collector currents IC67 and IC58 of Q58 are equal.

When the gain of the upper stage current amplification section becomes higher than the gain of the lower stage current amplification section, VB57 <VB58, IC57> I
c5s, ICl3>IC62, the input signal to the upper stage current amplification section decreases, and the gain balance is maintained. Conversely, when the gain of the upper stage current amplification section decreases, VB57
> VB68 r Ic5r< Ic5g, Ic
Since t2<IC62, the input signal to the upper stage current amplification section increases and the gain balance is maintained. As described above, the drive coil midpoint voltage is always kept at a constant value, and the soft switching signal waveform is maintained. Further, the bias of this amplifier A7 is supplied from the current feedback amplifier A4, and an output signal corresponding to the output signal of the current feedback amplifier giA4 is transmitted to the subsequent stage while maintaining the above function.

FIG. 8 shows a portion of another embodiment of the invention.

This embodiment is an example of a two-sensor, four-phase noft inoting energization method, and includes two sensors (Hall elements) HA,
HB outputs a two-phase sine wave-like output signal 1b corresponding to the relative positional relationship between the stator and rotor to the signal synthesis circuit 55M2 via amplifiers AA and AB. Signal synthesis circuit 55M2
Substantially in the same manner as in the above embodiment, the output signals of amplifiers AA and AB are logarithmically compressed to synthesize four-phase soft switching signals. This 4-phase soft switching signal is passed through an amplifier circuit consisting of 4 differential multipliers, a Bridry No.
In addition to the bases of transistors Q63 to Q70, fixed E four-phase drive coils 1 to L4 are energized. Current feedback amplifier, coil midpoint detector, coil midpoint feedback amplifier,
Filter capacitors 06-C9 are provided in the same manner as in the above embodiment.

The present invention can be similarly applied to a drive circuit for a five-phase or more brushless motor, and something other than a Hall element may be used as the position detection means.

FIG. 9 shows another embodiment of the invention.

This embodiment is an example of a one-sided energization method, and in the above embodiment, the amplifier circuit A5, the upper stage pre-drib inode (PDI), the power transistors Q31 to Q33, and the coil midpoint detector CD
, the coil midpoint feedback amplifier A7 is omitted.

Although this embodiment is an example of a three-phase brushless motor, the present invention can be similarly applied to a four-phase or more brushless motor.

Effects of the Invention As described above, according to the present invention, a soft switching signal with blunted inflection points is synthesized from the output signal of the position detecting means by a signal synthesis circuit, logarithmically compressed by an amplifier circuit, and then applied to the drive circuit. By applying a soft switching signal with a blunted inflection point to the driving coil KA, the capacitance of the filter capacitor can be reduced, which is advantageous in terms of space and cost. Furthermore, it can handle high-speed rotation, and can reduce mechanical noise even for motors other than those with a core.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a waveform diagram showing the Hall element output waveform and coil energization waveform of the same embodiment, and Fig. 3 is a circuit specifically showing the same embodiment. figure,
4 to 7 are waveform diagrams showing the signal waveforms of each part of the same embodiment, FIG. 8 is a block diagram showing a part of another embodiment of the present invention, and FIG. 9 is another embodiment of the present invention. Block diagram showing the first
FIG. 0 is a block diagram showing a conventional three-phase 120° energization method, and FIG. 11 is a waveform diagram showing the Hall element output waveform and energization waveform of the same method. Hu, Hv, Hw, HA, HB''Position detection means, SS
M. 55M2 ・Signal synthesis circuit, A5. A6...Amplification circuit, Q31-Q36, Q63-Q70...Power transistor for drive circuit, Lu, Lv, Lw,
Ll to L4 drive coil. Ryo G Illustration (Diagram 0 Procedural Amendment February 26, 1985 Patent Application No. 160709 of 1989 2 Title of the invention Brushless motor drive circuit 3 Relationship with the person making the amendment Patent applicant name (223) Sankyo Seiki Seisakusho Co., Ltd. 4
Agent Address: 4-5-4 Kyodo, Setagaya-ku, Tokyo "
"Detailed Description of the Invention" column and drawings (1) Page 2 of the specification, lines 11-12, "The output signal...
・Correct ``detect it'' to ``synthesize the rectangular wave output signal.'' (2) “Square wave pulse” on page 2, line 12.15 [
Correct it to ``120 degree swivel waveform signal''. (3) On page 2, lines 18-19, “The rotor...
・Delete "Detected". (4) Correct "current feedback amplifier A4 is the output voltage of the speed detector" on the 20th line of the second page to "control amplifier A41 is the speed command voltage". (5) Correct "speed command voltage" in the first line of page 3 to "reference voltage". (6) Correct ``taken out as a current command voltage, and then the difference thereof'' in lines 1 and 2 of page 3 to ``taken out as a current command voltage, and furthermore, the current command voltage.'' (7) On page 3, lines 3 and 4, "taken out by differential amplifier A42" is corrected to "J output by current feedback amplifier A42.""amplifier" should be corrected to "current feedback amplifier". (9) "Low intensity" in line 9 of page 3 is corrected to "reduction." (10) Change “Square wave pulse” on page 3, line 14 to “12
Correct it to ``0 degree switching waveform signal''. (11) In page 5, line 17, "through" is corrected to "logarithmically compressed by". (12) Correct "rectangular wave pulse-like soft switching signal" in lines 19 and 20 of page 5 to "120 degree soft switching waveform signal". (13) On page 6, lines 1 to 3, [there is, and the mountains are combined. ”
Correct it to "Yes." (14) Delete "also detected in..." in lines 11 and 12 of page 6. (15) On page 6, line 13, "current feedback amplifier A4 is the output voltage of the speed detector" is corrected to "control amplifier A41 is the speed command voltage". (16) Correct "speed command voltage" in line 14 of page 6 to "reference voltage". (17) "Differential amplifier..." on page 6, lines 14-15.
・Output the current command signal as the current command voltage.
Correct. (18) [Differential amplifier A42
Correct J taken out to "output from current feedback amplifier A42". (19) Change "A4" in the first line of page 7 to rA42. Correct to H. (20) “Drive coil...” on page 7, lines 7 to 12.
used. "In order to prevent oscillation in the final driver stage, a capacitor with a small capacity of about 0.1 μF is provided, and the energization control of the drive coils Lυ, Lv, and Lν is performed not by the capacitors Cu, Cv, and Cw. Signal synthesis circuit SSM
and amplifier circuit A5. This is performed using a soft switching signal whose inflection point is blunted by A6. ” is corrected. (21) Change “Q11 to Q15” on page 9, line 13 to “Q
13-Q15”. (22) "Current feedback amplifier A4J" on page 10, line 12
is corrected to "control amplifier 11A41 and current feedback amplifier A42". (23) "Correct speed command voltage J to "reference voltage" on page 10, line 13. (24) Correct "speed detector output voltage" in line 14 of page 1O to "speed command voltage". (25) Replace “A4” on page 12, line 1.2 with rA42J.
Correct each. (26) Insert "control amplifier," before "current feedback" on page 12, line 16. (27) Figures 1, 3, 9, and 10 in the drawings are corrected as shown in the attached sheets.

Claims (1)

[Claims] a stator having an m-phase driving coil; a rotor having magnetic poles; a position detection means for obtaining an m-phase sine wave-like output signal according to the relative positional relationship between the stator and the rotor; A signal synthesis circuit that logarithmically compresses the output signal of the position detection means, shapes the waveform into a rectangular wave pulse with rounded inflection points, and synthesizes it into an m-phase soft switching signal, and a signal synthesis circuit that converts the output signal of this signal synthesis circuit again. It includes an amplifier circuit that performs logarithmic compression, and a drive circuit that uses the output signal of the amplifier circuit to control energization of the m-phase drive coil, and a soft switching signal that is like a rectangular wave pulse with the inflection point blunted. A drive circuit for a brushless motor, characterized in that the drive coil is energized.