JPH0531395B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a drive circuit for a brushless motor.

BACKGROUND ART As a drive circuit for a brushless motor, a three-phase 120° switching energization system as shown in FIG. 10 is known. In this method, the Hall element Hu,
Hv and Hw produce three-phase sine wave-like output signals as shown in Figure 11, depending on the relative positional relationship between the stator, which has three-phase drive coils Lu, Lv, and Lw, and the rotor, which has magnetic poles. and this output signal is sent to amplifier A.
1 to A3 to the signal synthesis circuit SM. The signal synthesis circuit SM is digitally constituted by a logic circuit, and synthesizes the rectangular wave output signals of the amplifiers A1 to A3 to output a three-phase 120 degree switching waveform signal. Power transistors Q31 to Q36 constitute a final stage driver, and a signal synthesis circuit.
The three-phase rectangular wave pulses from the SM cause current to flow through the three-phase drive coils Lu, Lv, and Lw as shown in FIG. 11 to rotate the rotor. Drive coil Lu, Lv,
The current flowing through Lw is detected by a current detection resistor RS. The control amplifier A41 extracts the difference between the speed command voltage V _CTL and the reference voltage V _REF as a current command voltage, and further outputs the current command voltage and the current detection resistor.
The current feedback amplifier A42 outputs the difference with the voltage of RS. The signal synthesis circuit SM is a current feedback amplifier A4
The output signal voltage is controlled by the output signal of 2, and the filter capacitors Cu, Cv, and Cw are controlled by the mechanical noise and electrical noise generated by sudden changes in current when switching the energization of the drive coils Lu, Lv, and Lw. A capacitor of at least 10 μF or more installed to reduce noise.

Problems to be Solved by the Invention In the three-phase 120° switching energization method described above, the signal synthesis circuit SM
The energization of the drive coils Lu, Lv, Lw is switched by combining the phase 120 degree switching waveform signals and adding them to the bases of the power transistors Q31 to Q36.
Filter capacitors Cu, Cv, and Cw of 10 μF or more are essential to reduce noise generated by sudden changes in Lw current, which is disadvantageous in terms of space and cost. Furthermore, during high-speed rotation, the energy consumption of the filter capacitors Cu, Cv, and Cw increases, making them practically unusable. Furthermore, mechanical noise countermeasures using filter capacitors Cu, Cv, and Cw are less effective for motors other than those with cores, and are a major drawback.

Means for Solving the Problems The present invention provides a stator having an m-phase drive coil;
A rotor having magnetic poles, a position detecting means for obtaining an m-phase sine wave-like output signal according to the relative positional relationship between the stator and the rotor, and a position detecting means for logarithmically compressing the output signal of the position detecting means. A signal synthesis circuit that shapes the waveform into a rectangular wave pulse with rounded inflection points and synthesizes it into an m-phase soft switching signal, an amplifier circuit that logarithmically compresses the output signal of this signal synthesis circuit again, and this amplifier circuit. m above using the output signal of
and a drive circuit that controls energization of the drive coils of the phases.

Operation The position detection means generates an m-phase sine wave-like output signal according to the relative positional relationship between the stator and the rotor,
This output signal is logarithmically compressed by a signal synthesis circuit, shaped into a rectangular wave pulse with rounded inflection points, 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.

Hall elements Hu, Hv, Hw are three-phase drive coils
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 Lu, Lv, and Lw, and the rotor having magnetic poles, and this output signal is transmitted to the amplifier. The signals are logarithmically compressed by A1 to A3 and added to the signal synthesis circuit SSM. signal synthesis circuit
SSM uses 100% of the output signals of amplifiers A1 to A3 to synthesize three-phase 120-degree soft switching waveform signals in an analog manner. This soft switching signal is again logarithmically compressed by the amplifier circuits A5 and A6, which are composed of three differential multipliers, and then sent to the power transistors Q31 to Q forming the drive circuit via the upper stage pre-driver PD1 and the lower stage pre-driver PD2.
In addition to the base of 36, drive coils Lu, Lv,
The rotor rotates when a current is passed through Lw as shown in Figure 2. Drive coil Lu, Lv, Lw
The current flowing through is detected by the current detection resistor RS. The control amplifier A41 outputs the difference between the speed command voltage V _CTL and the reference voltage V _REF as a current command voltage, and the current feedback amplifier A42 outputs the difference between this and the voltage of the current detection resistor RS. drive coil
The voltage at the midpoint of Lu, Lv, and Lw is detected by a coil midpoint detector. The coil midpoint feedback amplifier A7 is connected to the detection voltage of the coil midpoint detector and the reference voltage (power supply voltage).
(1/2 of VCC) by differential amplifiers A71 and A72, and the output thereof is multiplied by the output signal of current feedback amplifier A42 by multipliers M1 and M2. Amplifier circuit A
5 and A6 are controlled by the output signals of multipliers M1 and M2 to change the output signal voltage, and perform rotor speed control, coil current feedback control, and coil midpoint voltage feedback control. Filter capacitor Cu, Cv,
Cw is to prevent oscillation of the final driver stage.
A capacitor with a small capacity of about 0.1 μF is installed, and the power supply control of the drive coils Lu, Lv, and Lw is performed not by the capacitors Cu, Cv, and Cw, but by the signal synthesis circuit SSM.
Then, the switching is performed using a soft switching signal whose inflection point is blunted by the amplifier circuits A5 and A6. Therefore, it is advantageous in terms of space and cost, and can cope with high-speed rotation by reducing the energy consumption of the filter capacitors Cu, Cv, and Cw, and can also reduce mechanical noise for motors other than those with cores.

FIG. 3 specifically shows this embodiment, in which R1 to R30 are resistors, Q1 to Q62 are transistors, D1 to D10 are diodes, and C1 to
C5 is a capacitor. Note that capacitor C1~
C3 is the filter capacitor Cu of about 0.1 μF,
Cv, Cw.

In the amplifiers A1 to A3 and the signal synthesis circuit SSM, if the output voltage of the μ-phase Hall element Hu is Vu, the collector current of the transistors Q2 and Q3 is
I _C2 and I _C3 are expressed by the following equations.

I _C2 = 200/ _1+e q/KT (-Vu) μA I _C3 = 200/ _1+e q/KT (+Vu) μA where q is the electron charge, K is Boltzmann's constant, and T
is the absolute temperature. Here, if |Vu|>100 mV, the respective collector currents I _C2 and I _C3 have waveforms as shown in FIG. 4, and are subjected to logarithmic compression. v phase,
The output voltages of the w-phase Hall elements Hv and Hw are similarly converted to the collector currents I _C4 - I _C7 of the transistors Q ₄ -Q ₇ which have undergone logarithmic compression, and are 120° from these collector currents I _C2 - I _C7 . Three-phase soft switching signals I _C2,5 , I _C4,7 , and I _C6,3 shifted by each phase are synthesized using the following equation.

I _C2,5 = I _C2 + I _C5 I _C4,7 = I _C4 + I _C7 I _C6,3 = I _C6 + I _C3 The pattern of this synthesis is shown in Figure 5. Hall element
Even if fluctuations or interphase differences occur in the outputs of Hu, Hv, and Hw, the distortion in the combined currents I _C2,5 , I _C4,7 , and I _C6,3 is small. The combined currents I _C2,5 , I _C4,7 , and I _C6,3 are converted into voltages V _R12 to V _{R14 by resistors R12 to R14} and transmitted to the subsequent stage.

Amplifier circuits A5 and A6 are transistors Q16 to Q
18, Q13 to Q15, and logarithmically compresses the output signal voltages V _R12 to V _R14 of the previous stage to suppress variations in the three-phase soft switching signals due to circuit errors in the previous stage. Further, signals are distributed to the upper and lower predrivers PD1 and PD2. This situation is shown in FIG. Here, the collector currents of transistors Q12 to Q18 and Q62 are assumed to be I _C12 to I _C18 and I _C62 . The magnitudes of the upper and lower drive signals (output signals to the upper and lower predrivers PD1 and PD2) are determined by I _C62 and I _C12 , and these I _C62 and I _C12 are controlled by the coil midpoint feedback amplifier A7 to drive the upper stage driver. The gain difference between the lower driver and the lower driver is always kept at zero.

Upper and lower predrivers PD1, PD2 and power transistors Q31 to Q36 are transistors Q1
9~Q36, resistor R18~R20, diode D
1 to D3, which amplifies the output currents I _C13 to I _C18 of the previous stage and supplies the drive coils Lu,
Supply to Lv and Lw.

Control amplifier A41 and current feedback amplifier A42 are transistors Q37 to Q52 and resistors R21 to R2.
4, the reference voltage V _REF and the speed command voltage V _CTL
A current command signal is created by calculating the difference between the two, and the difference between this and the voltage detected by the current detection resistor R25 (RS) is calculated and transmitted to the subsequent stage.

Coil midpoint detector CD is diode D5-D7
detects only the highest value of the three-phase drive coil Lu, Lv, Lw voltage waveform, and also detects the highest value of the voltage waveform of the three-phase drive coil Lu, Lv, Lw.
By detecting only the lowest value of the three-phase drive coil Lu, Lv, Lw voltage waveform and finding 1/2 of the highest and lowest values with resistors R29 and R30, the drive coil Lu, Lv, Lw Obtain the midpoint voltage. This situation is shown in FIG.

The coil midpoint feedback amplifier A7 is a transistor Q5.
The base voltage of transistor Q is the reference voltage, and the transistor Q
Let the base voltage of 58 be the drive coil midpoint voltage.
As mentioned above, when the gain balance of the lower stage current amplification section is balanced, the drive coil midpoint voltage matches the reference voltage, and the collector currents I _C57 and I C58 of the transistors Q57 and _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,
V _B57 <V _B58 , I _C57 > I _C58 , and I _C12 > I _C62 , so 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, V _B57 > V _B58 , I _C57 < I _C58 , and I _C12 < I _C62
As a result, 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. Also, this amplifier A7
The bias is supplied from the current feedback amplifier A42, and while maintaining the above function, the current feedback amplifier A42
An output signal corresponding to the output signal of is transmitted to the subsequent stage.

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

This embodiment is an example of a 2-sensor 4-phase soft switching energization method, and the 2 sensors (Hall elements) HA and HB generate a 2-phase sine wave pattern according to the relative positional relationship between the stator and rotor. The output signal is outputted to the signal synthesis circuit SSM2 via amplifiers AA and AB. The signal synthesis circuit SSM2 logarithmically compresses the output signals of the amplifiers AA and AB and synthesizes four-phase soft switching signals in substantially the same manner as in the above embodiment. These 4-phase soft switching signals are applied to the bases of power transistors Q63 to Q70 via an amplifier circuit and pre-driver consisting of 4 differential multipliers, and the 4-phase drive coils L1 to L4 of the stator are energized. . A control amplifier, a current feedback amplifier, a coil midpoint detector, a coil midpoint feedback amplifier, and filter capacitors C6 to 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 and the upper stage predriver
PD1, power transistors Q31 to Q33, coil midpoint detector CD, 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 detection means by a signal synthesis circuit, logarithmically compressed by an amplifier circuit, and applied to the drive circuit. Therefore, a soft switching signal with a blunted inflection point is applied to the drive coil, and 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 the drawing]

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, Fig. 3 is a circuit diagram specifically showing the same embodiment, and Figs. 4 to 7 are signals of various parts of the same embodiment. A waveform diagram showing waveforms, FIG. 8 is a block diagram showing a part of another embodiment of the present invention, FIG. 9 is a block diagram showing another embodiment of the present invention, and FIG. 10 is a conventional three-phase 120 11 is a block diagram showing the switching energization method. 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,
SSM, SSM2...signal synthesis circuit, A5, A6...
...Amplification circuit, Q31 to Q36, Q63 to Q70...
...Power transistor for drive circuit, Lu, Lv,
Lw, L1 to L4... Drive coil.

Claims (1)

[Claims] 1. A stator having an m-phase drive coil, a rotor having magnetic poles, and 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 an output signal of this signal synthesis circuit. an amplifier circuit that logarithmically compresses the
and a drive circuit that controls energization of the m-phase drive coil using the output signal of the amplifier circuit, and energizes the drive coil with a soft switching signal in the form of a rectangular wave pulse with the inflection point blunted. A brushless motor drive circuit characterized by: