JPH0731180A - Drive circuit for brushless motor - Google Patents

Abstract

PURPOSE:To allow generation of a drive current unlimitedly close to a sine wave through a relatively small circuitry, i.e., low resolution digital processing. CONSTITUTION:Second step current generating circuits 5a-7a generate step currents corresponding to the variation widths of step wave signals outputted from first step current generating circuits 5-7. When a triangular signal outputted from a triangular wave generating circuit 9 is amplified by current control amplifiers 9-11, the amplification factors are determined based on the ratios of output currents from the second step current generating circuits 5a-7a. Since the amplitude of triangular signal fits to each level of step wave signals a smoothly varying drive signal can be obtained through low resolution digital processing, i.e., small scale circuitry.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a brushless motor, and more particularly to a drive circuit for reducing a position detecting element and generating a drive signal by a digital circuit.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to suppress vibration and torque ripple during rotation of a three-phase brushless motor. In order to reduce vibration and torque ripple, it is preferable to make the current waveform supplied to the stator windings sinusoidal,
For example, in Japanese Patent Laid-Open No. 55-100808, since the position detection signal obtained from the Hall element does not become an ideal sine wave due to various factors, the sine wave information is stored in a digital memory in advance and the motor is stored. A DC brushless motor that sequentially reads out the information in the memory by an output signal of a frequency generator (generally called an FG signal) connected to and converts the information into an analog voltage to generate a drive current having a sine wave shape close to an ideal voltage. It is shown.

[0003]

The above-mentioned method has a considerably large circuit scale as compared with the conventional method of processing in an analog manner, and the digital method is required to produce a smoothly changing drive current. There was a problem that the resolution of the circuit had to be increased considerably.

The present invention has been made in order to solve such a problem, and produces a drive current as close as possible to a sine wave with a relatively small-scale circuit configuration, that is, digital processing with low resolution. It is an object.

[0005]

In order to solve the above-mentioned problems, the brushless motor drive circuit of the present invention includes a position detecting means for detecting a rotational position of a rotor and generating a position detection signal, and the rotor. Rotation detection means for generating a rotation detection signal having a frequency higher than the position detection signal when rotating, and each level of the staircase wave signal whose level is switched stepwise each time an edge of the rotation detection signal arrives. A step controller that generates a timing signal according to the first step current generator that turns on and off the current of a current mirror circuit that outputs a current of a predetermined distribution ratio based on the timing signal to generate a staircase wave signal. Means, a triangular wave generating means for generating a triangular wave signal in synchronization with an edge of the rotation detection signal, and the first step current generation Second to generate a relatively equal output signal to change the width of each level of the staircase signal outputted from the stage
The step current generating means and the amplifying means for inputting the output signal of the triangular wave generating means and amplifying the triangular wave signal with an amplification factor proportional to the output current of the second step current generating means. It is a thing.

[0006]

According to the present invention, in the above structure, the second step current generating means generates the step current corresponding to each change width of the staircase wave signal output from the first step current generating means, and the triangular wave generating means generates the step current. Since the amplification factor for amplifying the output triangular wave signal by the amplifying means is determined by the current ratio of the output of the second step current generating means, the amplitude of the triangular wave signal fits each level of the staircase signal, It is possible to obtain a drive signal that smoothly changes while performing digital processing with low resolution, that is, with a small-scale circuit configuration.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a brushless motor drive circuit according to an embodiment of the present invention. First, the outline of the entire operation will be described with reference to FIG.
In FIG. 1, 1 is one of U phase, V phase, and W phase 1
It is a position detecting means for detecting the position of the rotor for the phase component, and is a means for comparing the output signal of the position detecting element shown in A of FIG. 2 and outputting the signal shown in B of FIG.

Hereinafter, in this embodiment, the position detecting element is U
The description will be given assuming that it is an element that detects the position of the U phase of the three phases of the V phase, the V phase, and the W phase. Reference numeral 2 denotes a rotation detecting means such as a frequency generator, and in this embodiment, the rotation detecting means 2 has a rotation angle of 12 per 360 degrees as shown in FIG.
The description will be given assuming that it is configured to output an emission pulse. Hereinafter, this signal is abbreviated as an FG signal.

[0009] outputs a signal _{u 1 ~u 6, v 1 ~v} 6, w 1 ~w 6 showing the output signal of the step controller 3 position detecting means 1 and the rotation detecting means 2 in FIG. 2 by a digital signal processing . Here, the signals u _{1 to} u ₆ are drive signals for energizing the U-phase stator windings, and the signals v _{1 to} v ₆ are drive signals for energizing the V-phase stator windings, w _{1 to} w ₆ Signal becomes a drive signal for energizing the W-phase stator winding.

The U-phase digital drive signal u shown in FIG.₁
~ U₆Is the first step current generation circuit 5 and E in FIG.₁Shown in
Staircase wavy analog whose level changes in 6 steps
Is converted into a digital signal and output. Where u₁Signal of
Staircase wave signal E whose level changes in 6 steps₁First level of
Corresponding to u₂Signal also corresponds to the second level,
Below, u₃~ U₆Correspond to 3rd to 6th levels respectively
To do. V-phase digital drive signal v shown in FIG.₁~ V₆,
W phase digital drive signal w₁~ W₆Also for U phase
In the same manner as the above, the first step current generation circuits 6 and 7
E in Fig. 2 respectively ₂, E₃Staircase wave-shaped analog signal shown in
Is converted to.

By adding a slope to the signals E _{1 to} E ₃ , a driving signal that changes smoothly can be obtained (FIG. 4).
Shows the case where the slope signal Su is added to the staircase wave signal E ₁ to generate the U-phase drive current Um), but the amplitude of the slope current to be added and the respective level values of the staircase wave are temperature changes and resistance values. Even if the element variations such as the above are not consistent with each other, a smoothly varying drive signal cannot be obtained. The present invention provides a method of absorbing the influence of temperature change and element variation and adding a slope with high accuracy. This is realized by the slope control signal generation circuit 4, the second step current generation circuits 5a to 7a, and the current control amplifiers 9 to 11. In this embodiment, for convenience, the second step current generation means is realized by the slope control signal generation circuit 4 and the second step current generation circuits 5a to 7a.

First, the slope control signal generating circuit 4 is shown in FIG.
Us ₁ ~us ₆ in, vs ₁ ~vs _6, ws ₁ the circuit that generates a signal indicating the ~ws _6, us _{1 ~us 6} becomes slope control signal of the U phase, vs ₁ ~vs ₆ is V It becomes a phase slope control signal, and ws _{1 to} ws ₆ become W phase slope control signals. Those corresponding to the magnitude of the amplitude of the slope when the _{us 1 ~us 6, vs 1 ~vs} 6, signals ws ₁ to WS ₆ is the addition of slopes in the aforementioned staircase signal E ₁ to E ₃ .
That is, considering the case where the slope is added to the staircase wave signal E ₁ shown in FIG. 4 to generate the sine wave signal Um shown in FIG. 4, the first step, the twelfth step, the thirteenth step, the The amplitude of the slope of 24 steps (corresponding to the first level of the staircase wave signal E ₁ ) and the second step, the 11th step, the 14th step, the 23rd step (the staircase wave signal E 1
₍ Corresponding to the second level of ₁ ) is different, and the amplitude of the slope corresponds to each of the first to sixth levels of the staircase signal E ₁ like the slope current Su shown in FIG. Need to change.

Thus, us ₁ to us ₆ , vs _{1 to} vs ₆ ,
ws _{1 to} ws ₆ correspond to the levels of the U-phase, V-phase, and W-phase slope signals. us _{1 to} us ₆ , vs _{1 to} v
The signals s ₆ and ws _{1 to} ws ₆ are input to the second step current generation circuits 5a to 7a and output the analog signals G _{1 to} G ₃ shown in FIG. The amplitude values of the signals G _{1 to} G ₃ correspond to the amplitude value of the slope to be added.

Next, the triangular wave generating circuit 8 outputs the triangular wave signal S ₀ shown in FIG. 4 in synchronization with the rotation detecting means 2, that is, the edge of the FG signal. The triangular wave signal S ₀ is configured such that its amplification factor is relatively equal to the current values of the currents G _{1 to} G ₃ output from the second step current generation circuits 5a to 7a. Entered in. In the current control amplifiers 9 to 11, the triangular wave signal S ₀ is adjusted to a predetermined amplitude and the slope current Su shown in FIG. 4 is output. In addition to the staircase wave currents E _{1 to} E ₃ , Um, Vm, Wm in FIG. Drive signal is obtained.

The details of the operation will be described below from the step controller 3 first. FIG. 5 shows a specific circuit example of the step controller. In FIG. 5, inverters 301 to 304, D flip-flops (hereinafter abbreviated as DFF) 305 to 306, NAND
In the circuit 3A including the gates 307 to 309, the signal B (Uh) shown in FIG.
From the NAND gate 309 to the pulse signal (30) shown in FIG. 6 at the first edge of the FG signal after the transition from "H" to "H".
In the circuit for outputting 9), this signal becomes the reference position signal for generating the drive signal. The operation starts with the signal Uh.
Is changed from "L" to "H", the output of DFF305 is changed from "L" to "S" in synchronization with the trailing edge of FG.
On the other hand, the output of the DFF 306 shifts from "L" to "H" in synchronization with the leading edge of the FG. That is, the output of the DFF 305 and the output of the DFF 306 always have a phase delay of FG half cycle. 6 shows a waveform diagram of this portion, which shows the signal Uh.
7 shows a waveform in the case where the edge of the first FG after the arrival of is the leading edge. In addition, the NAND gate 3
07 to 309 take the exclusive OR of the output of the DFF 305 and the output of the DFF 306, and output “H” when both outputs are equal, and output “L” when they are different. The difference between the output of the DFF 305 and the output of the DFF 306 is that the section from the edge of the first FG to the edge of the second FG after the signal Uh changes from “L” to “H” and the signal Uh is “H”. It is a section from the edge of the first FG to the edge of the second FG after shifting from "L". In this section, the output of NAND gate 309 is "
However, since the signal Uh is input to the NAND gate 309, the output of the NAND gate 309 is forced to be "H" when the signal Uh is "L".
From the output of the AND gate 309, a pulse having a pulse width of FG half cycle is generated at the first FG edge after the signal Uh shifts from "L" to "H".

Next, in the circuit composed of the NAND gates 310 to 316, if the first FG edge after the signal Uh changes from "L" to "H" is the leading edge, NAN.
If the input FG is inverted and output from the output of the D gate 316, while the first FG edge after the signal Uh changes from "L" to "H" is the trailing edge, NAND
The output of the gate 316 is a circuit that outputs the input FG as it is. That is, if the signal Uh changes from "L" to "
If the edge of the first FG after becoming "H" is the leading edge, the output of the DFF 306 at this time is "
Then, the output of the NAND gate 310 becomes "L" and the output of the DFF 305 becomes "L".
As it is, that is, the output of the NAND gate 311 is “H”
As it is, the NAND gate 312 outputs “H” and the NAND gate 313 outputs “L”. As a result, the NAND gate 316 outputs the inverted signal of the FG output from the inverter 301. Signal U
When the edge of the first FG after h changes from "L" to "H" is the trailing edge, the operation is the same except that the values of the outputs are reversed.

Next, the inverters 317, 325, 32
6, T flip-flop (hereinafter abbreviated as TFF) 3
Circuit 3B composed of 18 to 320 and NAND gates 321 to 324, inverters 327 to 334, and NAN.
The circuit 3C composed of the D gates 335 to 355 is a NAND
An FG signal output from the gate 316 (hereinafter, this FG signal is distinguished from the FG signal output from the rotation detecting means and is referred to as an FG ₁ signal) and a pulse signal output from the NAND gate 309 (hereinafter,
This pulse signal is designated as the reference position signal P ₀ ) and outputs position signals P _{1 to} P ₁₂ whose pulse positions are shifted step by step as shown in FIG. First, the operation of the circuit 3B including the inverters 317, 325, 326, the TFFs 318 to 320, and the NAND gates 321 to 324 will be described. This circuit is a circuit for outputting the signals 318 to 320 shown in FIG. 6 from the reference position signals P ₀ and FG ₁ . The TFFs 318 to 320 basically operate as counters,
If the reference position signal P ₀ is given (whether P ₀ becomes “L”) or all the inverted outputs of the TFFs 318 to 320 become “H”, the TFF 318 is reset and TF is set.
F319 and 320 are set.

The operation will be described below with reference to FIG.
Now, at time t ₁ , the reference position signal P ₀ changes from “H” to “
When it becomes L ″, the TFF 318 is reset and the TFF 31
9,320 is set. Then at time t ₃ , F
When G ₁ changes from “H” to “L”, the output of the TFF 318 changes from “L” to “H”, which causes the TFF 319.
Output changes from "H" to "L". Next, at time t ₄ , FG ₁ changes from “H” to “L”, so that TFF
The output of 318 shifts from "H" to "L". Next, at time t ₅ , if FG ₁ changes from “H” to “L”, TFF
The output of 318 changes from “L” to “H”, which changes the output of the TFF 319 from “L” to “H”, which causes the output of the TFF 320 to shift from “H” to “L”. Hereinafter, the TFFs 318 to 320 are counted each time the trailing edge of FG ₁ arrives. Time t ₆
If FG ₁ changes from “H” to “L” at TFF31
The output of 8 shifts from "H" to "L", which causes T
All the inverting terminal outputs of the FFs 318 to 320 shift to "H". Therefore, the output of the NAND gate 321 is "L".
, The output of the NAND gate 322 becomes “H”, the output of the NAND gate 323 becomes “L”, and the output of the NAND gate 324 becomes “L”.
H ”, and via the inverter 325, the TFF 319,
Set 320. By repeatedly performing the above-described operation, the outputs of the TFFs 318 to 320 are output as shown in FIG.
The signals 318 to 320 shown in are obtained.

Next, the inverters 327 to 334, NAN
The circuit 3C composed of the D gates 335 to 355 has the above-mentioned signal.
No. 318-320 and FG₁To P₂~ P₁₂Circuit to generate
Is. P₁About the output from the NAND gate 324.
It is obtained by inverting the applied signal. P₂Is F
G₁And output of TFF319 and output of TFF320
Obtained from the NAND output of_FourIs FG₁And TFF
Three-way NAND output of the output of 318 and the output of TFF320
Obtained from force, also P₆Is FG₁And inversion of TFF318
Output and the inverted output of TFF 319 are three NAND outputs?
Similarly obtained from P₈Is FG₁And the output of TFF318 and T
Obtained from the NAND outputs of the three parties of the output of FF319,
Like P_TenIs FG₁And the inverted output of TFF318 and TFF3
Obtained from the three NAND outputs of the inverted output of 20,
To P₁₂Is FG₁And the output of TFF318 and the output of TFF319
Inverted output and inverted output of TFF320 output from four NANDs
Obtained from power. Then P₃Are NAND gates 341-
343 circuit with P₂And P _FourIs generated from. Tsuma
At time t as shown in FIG.₁At P₂The trailin
When the edge arrives, the output of the NAND gate 341 becomes "
Transition from L "to" H. "Next, time t₂At P₂
Is changed from "L" to "H", the NAND gate 343
Both inputs become "H", so output (P₃) Is "
L ". Next, time t₃At P_FourThe trail
Output of NAND gate 341
Goes to "L", so the output of NAND gate 343
(P₃) Returns to "H". In this way, the NAND gate 3
The output of 43 is P₂"L" at the leading edge of
R, P_FourSo that it becomes “H” at the trailing edge of
Because it is made, P₂And P_FourBetween P₃The pulse signal of
To live. P_Five, P₇, P₉, P₁₁About P₃As well as raw
Formed, P_FiveIs P_FourAnd P₆From P₇Is P₆And P₈From P₉
Is P ₈And P_TenFrom P₁₁Is P_TenAnd P₁₂Is generated from
It P generated as above₁~ P₁₂From NAND game
356-379 and inverters 380-400
2 shown in FIG.₁~ U₆, V₁~ V₆, W
₁~ W₆Is generated. Like this step controller
3 outputs the output of the position detecting means 1 and the output of the rotation detecting means 2.
Drive signal is generated from the signal by digital signal processing
It Further, although not particularly described so far, N in FIG.
The circuits of the AND gates 401 to 406 are U phase, V phase, W phase.
When adding a slope to the staircase wave drive signal of
Circuit that generates loop switching signals Usw, Vsw, Wsw
Yes, add a slope to the staircase signal as shown in Figure 4.
When the drive signal has an upward slope (
If the electrical angle is 0 to 90 degrees and 180 to 270 degrees)
Adds the slope as it is, and when the slope is downhill (see Fig. 4
In the case of waveform, electrical angle 90-180 and 270-360
In order to add the slope signal by inverting
belongs to.

Next, the slope control signal generation circuit 4 will be described.
Will be explained. FIG. 7 shows the slope control signal generation circuit 4
It shows a specific circuit example. Slope control signal
us ₁~ Us₆, Vs₁~ Vs₆, Ws₁~ Ws₆Also the above
Drive signal u of controller output₁~ U₆, V₁~ V₆，
w₁~ W₆Position signal P₁~ P₁₂Based on.
Below us₁~ Us₆The operation of generating will be described. Figure
In FIG. 7, a circuit composed of NAND gates 420 to 427
The path is the position signal P generated by the step controller 3.₁
~ P₁₂From us₁~ Us₆Is a circuit for generating. Tsuma
, Us₁Is P₁₂Set at the trailing edge of P₂
Flip-flops reset on the trailing edge of
Circuit (comprising NAND gates 420 and 421)
Generated by us₂Is P₂And P₁₁Generated from NAND
Is, us₃Is P₃And P_TenGenerated from NAND,_Four
Is P_FourAnd P₉Generated from NAND,_FiveIs P_FiveAnd P₈
Generated from NAND,₆Is P₆Trailing
Set with P.₈Reset at the trailing edge of
Flip-flop circuit (NAND gate 426,
427)). Also, vs₁~ V
s₆Circuit (NAND gates 428 to 43)
5), ws₁~ Ws₆Circuit (NAND gate 4
36-443), the same operation is performed.

The drive signals u _{1 to} u ₆ , generated in this way,
v _{1 to} v ₆ and w _{1 to} w ₆ are the first step current generation circuits 5 to 5, respectively.
7 and slope control signals us _{1 to} us ₆ , vs ₁ to
vs ₆ , ws _{1 to} ws ₆ are the second step current generation circuit 5
a to 7a, the drive signal is a staircase wave signal indicated by E _{1 to} E ₃ in FIG. 3, and the slope control signal is a signal indicated by G _{1 to} G ₃ in FIG. 3 (hereinafter, this signal is referred to as a gain control signal). Express). Hereinafter, the first step current generation circuits 5 to 7 and the second step current generation circuits 5a to 7 will be described.
A will be described.

FIG. 8 shows a concrete circuit example of the first step current generating circuit 5 and the second step current generating circuit 5a, and both circuits are shown here as a mixture for convenience. That is, the transistors 501 and 50
3,505,507,509,511,525,52
7,529,531,533,535, diode 53
7, 539, 541, 543, 545, 547, resistor 5
13, 515, 517, 519, 521, 523, and inverters 549, 551, 553, 555, 55
The first step current generation circuit 5 is composed of a circuit composed of 7,559 and includes transistors 502, 504, 506, 5
08,510,512,526,528,530,53
2,534,536, diodes 538,540,54
2,544,546,548, resistors 514,516,5
18, 520, 522, 524, and inverter 55
The circuit composed of 0, 552, 554, 556, 558, 560 constitutes the second step current generating circuit 5a. Incidentally. Although not shown here, the first in V phase and W phase
The step current generation circuits 6 and 7 and the second step current generation circuits 6a and 7a have the same configuration.

In FIG. 8, transistors 501-51 are provided.
2 and resistors 513 to 524 constitute current source circuits 51 to 62, in which the current source circuits 51 and 5 are connected.
2 have the same current value, the current source circuits 53 and 54 have the same current value, the current source circuits 55 and 56 have the same current value, and the current source circuits 57 and 58 have the same current value. The current values of 59 and 60 are the same, and the current values of the current source circuits 61 and 62 are the same. Further, the current value of the current source circuits 51, 52, 63 is set to I
₁ , the current value of the current source circuits 53 and 54 is I ₂ , the current source circuit 5
5,56 current value I ₃ in a current value I ₄ of the current source circuit 57 and 58, the current value of the current source circuit 59, 60 I _5, the current value of the current source circuit 61, 62 by the I ₆ For example, these current values are configured to satisfy the following equation.

I ₁ = I ₀ · sin 15 degrees (1) I ₂ = I ₀ · (sin 30 degrees −sin 15 degrees) ··· (2) I ₃ = I ₀ · (sin 45 degrees −sin 30 degrees) · _{·· (3) I 4 = I} 0 · (sin60 degrees -sin45 _{degrees) ··· (4) I 5 =} I 0 · (sin75 degrees -sin60 _{degrees) ··· (5) I 6 =} I 0 · ( sin 90 degrees-sin 75 degrees) (6) However, in the formulas (1) to (6), I ₀ is a reference current value.

In the IC, the accuracy of the ratio of the resistance value and the area is good, so that the transistors 501 to
If the emitter area of 512 and the resistance values of the resistors 513 to 524 are set so as to satisfy the expressions (1) to (6), a current source circuit that satisfies the expressions (1) to (6) can be realized relatively easily. In the first step current generation circuit 5 and the second step current generation circuit 5a configured as described above,
First, the operation of the first step current generation circuit 5 will be described.

Now, when the drive signal u ₁ is "H", the transistor 525 is turned off, so that the current I ₁ given from the current source circuit 51 is outputted as it is through the diode 537. On the other hand, when u ₁ is “L”, the transistor 525
Is turned on, the current I supplied from the current source circuit 51 is
₁ is the collector current of the transistor 525, and no current flows through the diode 537. In other words, the input signal is "
When it is H ", the current I sent from the current source circuit 51
_{When 1} is the output current, the output current is 0 when it is "L". Operation for the other input signal _{u 2 ~u 6, us 1 ~us} 6 are identical.

Next, the operation when the drive signals u _{1 to} u ₆ output from the step controller 3 are input to the first step current generating circuit 5 will be described with reference to FIG. In FIG. 9, drive signals u _{1 to} u _{6 at} time t ₀ .
Since the values of all are "L", the value E _{1 of the} output current is 0 at this time. Next, when u ₁ becomes “H” at time t ₁ , the transistor 525 is turned off, and the current I ₁ of the current source circuit 51 is sent to the output terminal via the diode 537. At this time, since u _{2 to} u ₆ are “L”, the current flowing to the output is only the current I ₁ of the current source circuit 51, and the output current E ₁ is I _1, that is, I ₀ · sin 15 degrees. Next, at time t ₂ , if u ₂ becomes “H”, the transistor 527 is turned off, so that the current I of the current source circuit 53 is
₂ is sent to the output terminal via the diode 539.
Therefore, the output current E ₁ is I ₁ + I _2, that is, I ₀ · sin3
It will be 0 degrees. Similarly, at time t ₃ , the output current E ₁ is I
₀ · sin 45 degrees, and at time t ₄ , the output current E ₁ is I ₀
-Sin 60 degrees, the output current E ₁ is I _{0 at} time t _5.
-Sin 75 degrees, the output current E ₁ is I _{0 at} time t _6.
-Sin 90 degrees = I ₀ .

As described above, in the first step current generating circuit 5, the sinusoidal staircase wave signal E ₁ is generated by inputting the u _{1 to} u ₆ drive signals output from the step controller 3. . Further, here, the current ratio of the current source circuits 51, 53, 55, 57, 59, 61 is (1)
Since the sine wave staircase wave signal is output because the setting is made according to the equation (6), the current source circuits 51, 53, 55, 57,
An arbitrary staircase wave signal is possible depending on how to set 59, 61.

Next, referring to FIG. 9, the second step
Output from the slope control signal generation circuit 4 to the current generation circuit 5a.
Forced signal us₁~ Us₆About the operation when is input
And explain. us₁~ Us₆Basically when is entered
Drive signal u to the first step current generation circuit 5₁~
u₆The operation is the same as when is input.
At time t₀Then us₁Only "H", so transition
By turning off the star 526, the diode 538 is turned on.
Current I from the current source circuit 52 flowing into the output terminal via
₁Ie I₀・ Sin 15 degree is output current G₁Value of
Time t₂Then us ₂Only the output current becomes "H", so the output current
G₁Is the current I from the current source circuit 54.₂Ie I₀・
(Sin 30 degrees-sin 15 degrees). And so on
Time t₃Then the output current G₁Value of I₀・ (Sin 45 degrees-
sin 30 degrees), time t_FourThen the output current G₁Value of I₀・
(Sin 60 degrees-sin 45 degrees), time t_FiveThen output power
Flow G₁Value of I₀・ (Sin 75 degree-sin 60 degree), hour
Tick t₆Then the output current G₁Value of I₀・ (Sin 90 degree-s
in 75 degrees).

As described above, in the first step current generating circuit 5 and the second step current generating circuit 5a, the drive signal and the slope control signal generated by the digital signal processing are stepped according to the current ratio of the current source circuits 51 to 62. Convert to a wavy analog signal. At that time, there is almost no variation in the resistance ratio and area ratio inside the IC, and good accuracy can be obtained, so the absolute value of the current also changes when converting to an analog signal as described above, but the relative value changes with temperature and variation. Since it does not change, the obtained signal waveform itself does not change. Although only the U phase has been described here, the V phase,
The structure and operation of the W phase (first step current generation circuits 6 and 7 and second step current generation circuits 6a and 7a) are the same as those in the U phase.

Next, the triangular wave generating circuit 8 will be described. FIG. 10 shows a specific circuit example of the triangular wave generating circuit. In FIG. 10, a circuit including a transistor 801 and a resistor 803 and a circuit including a transistor 802 and a resistor 804 are a current source circuit 81 and a current, respectively. The current source circuit 8 constitutes the source circuit 82.
The common baseline of 1,82 is the first shown in FIG. 8 for convenience.
It is assumed that the step current generation circuit 5 and the current source circuits 51 to 62 of the second step current generation circuit 5a are connected to the common baseline. Further, here, it is assumed that the current values of the two current source circuits 81 and 82 are equal to each other, and the resistance value of the resistor 805 is the resistance 80.
It is assumed that the resistance value is set to be larger than the resistance value of 6. The triangular wave generating circuit configured as described above includes an inverter 835.
By inputting the FG signal to the FG signal, the emitter of the transistor 814 outputs a triangular wave S ₀ synchronized with the edge cycle of the FG signal as shown in FIG.
Let S _MAX be the sum of the voltage value generated by the current flowing from the resistor 805 and the voltage value of the battery 807, and the voltage value generated by the current flowing from the current source circuit 82 to the resistor 806 and the voltage of the battery 807. If the sum of the values is S _MDL , the maximum value of the triangular wave signal S ₀ output from the emitter of the transistor 814 is S _MAX , and its amplitude value is 2.
(S _MAX- S _{M DL} ).

The operation will be described below with reference to the waveform chart shown in FIG. First, the inverters 834 to 836,
The circuit 87 including the NAND gates 837 to 843 is an FG.
This is a circuit in which the output of the NAND gate 843 becomes "H" when the value of the signal transits, and the output of the NAND gate 843 becomes "L" when the value of the inverter 834 becomes "H". That is, when the input of the inverter 834 is "L", that is, its output is "H" at time t ₀ , FG
Either the output of the NAND gate 838 or the output of the NAND gate 841 depends on the value of the signal.
H ″. In the case of FIG. 11, F at time t ₀
Since the G signal is "L", the output of the NAND gate 841 is "H". Next, at the instant when the FG signal shifts from "L" to "H" at time t ₁ , both inputs of the NAND gate 842 become "H", so NAND
The output of the gate 842 becomes "L", which causes NA
The output of the ND gate 843 becomes "H". The same is true at the moment when the FG signal shifts from "H" to "L". At this time, the output of the NAND gate 839 becomes "L", which causes the output of the NAND gate 843 to become "L".
H ".

Before explaining the operation when the input of the inverter 834 becomes "H", for convenience sake, the transistor 8 when the output of the NAND gate 843 becomes "H" will be described.
08-814, current source circuit 815, and capacitor 8
The operation of the circuit composed of 16 will be described. Transistor 80
8 to 814 and the current source circuit 815 constitute a voltage follower circuit of the operational amplifier, and the NAND gate 843.
When the output of is "H", the transistor 810 turns on,
This causes the transistors 808 to 813 to operate.
As a result, the capacitor 816 is rapidly charged and the emitter voltage of the transistor 814 becomes equal to the voltage S _MAX given from the transistor 808. Next, the transistors 824 to 827, 829, 830 and the current source circuit 82.
The circuit 84 composed of 8, the resistors 830 and 832, and the battery 833 constitutes a comparator circuit. If the voltages input from the bases of the transistors 824 and 825 are equal, the output voltage from the collector of the transistor 830 is “H”. If the base voltage of the transistor 825 is smaller than the base voltage of the transistor 824, the output voltage from the collector of the transistor 830 is "
L ″. Therefore, at time t ₁ , NA
When the output of the ND gate 843 becomes "H", the transistors 808 to 813 are activated and the transistor 814 is activated.
Has an emitter voltage equal to the voltage S _MAX applied to the base of the transistor 808, that is, the comparator 8
The two input voltages of 4 become equal, and the comparator output from the collector of the transistor 830 becomes "H". The above operation is instantaneously performed, and the output of the comparator 84 is "
The output of the inverter 834 becomes "L" when it becomes "H"
As a result, the flip-flop circuit composed of the NAND gates 840 and 841 is reset, and the output of the NAND gate 842 shifts from "L" to "H".
The output of the gate 843 returns to "L". That is, the output of the NAND gate 843 is "Every time the edge of the FG signal arrives."
H ″ and the operation of transistors 808-813 charges capacitor 816 so that the emitter voltage of transistor 814 is equal to the base voltage S _MAX of transistor 808, which causes comparator 84
Output becomes "H", and the output of the NAND gate 843 returns to "L". On the other hand, when the NAND gate 843 becomes "L", the transistors 808 to 813 are turned off and the capacitor 816 starts discharging gradually. The discharging speed at this time depends on the collector current of the transistor 822. That is, when the collector current of the transistor 822 is large, the discharge rate is fast, and when it is small, the discharge rate is slow. In this example of this circuit, a triangular wave signal is generated by using the charge and discharge of the capacitor 816. In particular, in this circuit, as described below, F
Even if the frequency of the G signal, that is, the number of rotations of the motor changes, a triangular wave signal having a constant amplitude is constantly obtained. This operation will be described below.

As described above, the capacitor 816 is charged and discharged.
Transistor 81 forming an emitter follower circuit
The triangular wave signal S shown in FIG.₀Is output
This signal S₀Is smoothed by the smoothing circuit 83,
Its average voltage S_MEANIs output. This average voltage S_MEAN
Is input to the base of transistor 818,
The transistors 818 to 821 form an operational amplifier, and
The voltage S input to the base of the transistor 818_MEANIs
The voltage S input to the base of the transistor 819 _MDLThan
Also becomes large (that is, the triangular wave signal S₀The amplitude of
(Meaning that) and the collector of the transistor 820
The voltage output from the
The collector current of the capacitor 822 increases,
Discharge speed increases, triangular wave signal S₀The amplitude of
The average voltage S output from the smoothing circuit 83
_MEANOperates in a decreasing direction. On the other hand, transistor 8
Voltage S input to the base of 18_MEANTransistor 8
Voltage S input to the base of 19_MDLLess than
(That is, the triangular wave signal S₀Means that the amplitude of
Is output from the collector of the transistor 820.
Voltage drops, which causes the transistor 822
The discharge speed of the capacitor 816 is reduced due to the decrease in the collector current.
Becomes gentle, and the triangular wave signal S₀The amplitude of
The average voltage S output from the smoothing circuit 83 by_MEAN
Operates in an increasing direction. In this way the transistor 8
In the negative feedback loop of the operational amplifier composed of 18-821
Therefore, the average voltage S output from the smoothing circuit 83_MEANIs S
_MDLWorks to be equal to. In other words, this is FG
Regardless of the frequency of the signal, the
The triangle wave signal S of constant amplitude is constantly output from the mitter.₀Is output
Means to be By the operation described above, Transis
The maximum value from the emitter of the switch 814 is S_MAXAnd the amplitude is 2.
(S_MAX-S_MDL) Triangular wave signal is output and the current control
It is input to the width devices 9 to 11.

Next, the current control amplifiers 9 to 11 will be described. FIG. 12 shows a concrete circuit example of the current control amplifiers 9 to 11. In FIG. 12, transistors 901 to 908, 915, 916, 919 to 93 are included.
2, the resistors 909 to 914, 933 to 939, the current source circuits 917 and 918, and the battery 940 constitute the current control amplifier 9 that outputs the U-phase slope signal Su. In this embodiment, only the U-phase current control amplifier 9 is shown, but basically the V-phase and W-phase current control amplifiers 10 and 11 are basically shown.
Also has the same configuration as the current control amplifier 9. 12
Among them, the transistor 908 and the resistor 909 are the current source circuit 95.
Although not shown in the drawing, the transistor 9
The base of 08 is the current source circuits 51 to 62 of the first step current generation circuit 5 and the second step current generation circuit 5a.
In the following description, it is assumed that the current value is connected to the common base line and the reference current value is I ₀ shown in the equations (1) to (6) for convenience of explanation. Further, the transistors 905 to 907 and the resistor 91
It is assumed that the current mirror circuit 91 composed of 0 to 912 is configured such that the emitter current values of the transistors 905 to 907 are equal to each other.
21 and 922 and resistors 933 and 934, the current mirror circuit 92 is configured so that the emitter current values of the transistors 921 and 922 are equal, and the current mirror circuit including transistors 927 to 929 and resistors 935 to 937. 93 is a transistor 925
It is assumed that the emitter current values of 927 are the same, and the current mirror circuit 94 including the transistors 930 and 931 and the resistors 938 and 939 is such that the emitter current values of the transistors 930 and 931 are 1: 2. It is assumed to be configured in. The current control amplifier 9 configured as described above generates a signal current generated when the triangular wave signal S ₀ output from the triangular wave generation circuit 8 is given to the base of the transistor 901 and the current value I ₀ of the current source circuit 95 and the second value. The gain control signal G ₁ output from the step current generation circuit 5a is amplified and output at a ratio with the current value of the gain control signal G ₁ . The operation will be described below.

The resistance value of the resistor 913 is R ₉₁₃ , the emitter dynamic resistances of the transistors 901 and 902 are both re, and the triangular wave signal S ₀ is applied to the base of the transistor 901, so that from the transistor 901 to the collector of the transistor 902 via the resistor 913. Signal current flowing with
Then, the amplitude of the triangular wave signal S ₀ is 2 · (S _MAX −
Since S _{MD L} ), ia is obtained by the following equation.

Ia = 2 · (S _MAX −S _MDL ) / (R ₉₁₃ + 2 · re) (7) When this current flows through the transistors 903 and 904, a signal voltage is generated, and this signal voltage is generated by the transistor. The signal current ib is generated by being input to the differential amplifier composed of 919 and 920. Here, the voltage from the collector of the transistor 903 to the emitter of the transistor 903 and to the emitter of the transistor 920 via the transistor 916 is equal to the voltage from the collector of the transistor 904 to the emitter of the transistor 904 and to the emitter of the transistor 919 via the transistor 915. Therefore, the following equation is established.

V _BE903 + V _BE916 + V _BE920 = V _BE904 + V _BE915 + V _BE919 (8) Here, V _BE903 , V _BE904 , V _BE915 , V _BE916 , V
_BE919 and V _BE920 are transistors 903 and ₉₀ , respectively.
The base-emitter voltages of 4,915, 916, 919, and 920 are shown.

In equation (8), the transistors 915,
Reference numeral 916 constitutes a buffer circuit using an emitter follower, and the base-emitter voltages thereof are equal to each other, so that the expression (8) becomes the expression (9) as a result.

V _BE903 + V _BE920 = V _BE904 + V _BE919 (9) In the equation (9), the relation between the base-emitter voltage of the transistor and the emitter current V _BE = V _T · ln ( _IE /
The use of I _S), the emitter currents of the transistors 903 and 904 is expressed as I ₀ -ia and I ₀ + ia, respectively, the emitter current of the transistor 919 and 920 and the G _1/2-ib and G _1/2 + ib respectively Since it is expressed, the equation (9) becomes as follows.

[0041] _{V T · ln ((I 0} -ia) / I S) + V T · ln ((G 1/2 + ib) / I S) = V T · ln ((I 0 + ia) / I S) + V T Ln ((G ₁ / 2-ib) / I _S ) ... (10) Further, by rearranging the equation (10), ib = ia · G ₁ / (2 · I ₀ ) ... (11) Becomes Emitter current of the transistor 919 (G _1/2
-Ib) is the collector current of the transistor 924 as it is due to the current mirror circuit composed of the transistors 923 and 924, and therefore the output current io flowing from the collector of the transistor 920 to the emitter of the transistor 926.
_{Is, io = (G 1/2} + ib) - Thus _{(G 1/2-ib)} = 2 · ib ··· (12), (11), io (12) equation, io = ia · G ₁ / I ₀ ... (13) This current io is supplied from the collector of the transistor 928 to the current mirror circuit 94 by the current mirror circuit 93 and is output as the slope signal Su from the collector of the transistor 929, but the slope switching signal Usw input to the base of the transistor 932 is used.
Is "H", all the current supplied from the collector of the transistor 928 becomes the collector current of the transistor 932. Therefore, the current mirror circuit 94 does not operate, and the collector current of the transistor 929 becomes the slope signal Su as it is. On the other hand, when the slope switching signal Usw input to the base of the transistor 932 is "L", the current mirror circuit 94 operates. At this time, the mirror ratio of the current mirror circuit 94 is 2 for the collector current of the transistor 930 and 2 for the collector current of the transistor 931.
Therefore, the transistor 9
A current twice the current output from the collector of the transistor 929, that is, 2 · io, flows into the collector of 31. At this time, the current i from the collector of the transistor 929
Since o is supplied, io current is supplied from the output terminal to the collector of the transistor 931. That is, as shown in FIG. 12, the slope switching signal Usw is "
When it is "H", the slope current is supplied, and when it is "L", the slope current is absorbed.

In the above description, the current io indicates the magnitude of the slope current, that is, the amplitude. The amplitude value is (7),
From the equation (13), io = ia · G ₁ / I ₀ = 2 · G ₁ · (S _MAX −S _MDL ) / {(R ₉₁₃ + 2 · re) · I ₀ } (14) Here, (S _MAX −S _MDL ) is the difference between the voltages generated by the current source circuits 81 and 82 in the triangular wave generating circuit 8 shown in FIG. 10 flowing through the resistors 805 and 806, so the current source circuit 81, The current value of 82 is α · I
₀ , the resistance values of the resistors ₈₀₅ and ₈₀₆ are R ₈₀₅ ,
If R ₈₀₆ , then S _MAX −S _MDL = α · I ₀ · (R ₈₀₅ −R ₈₀₆ ) ... (15). Substituting equation (15) into equation (14), io = 2 · G ₁ · α · (R ₈₀₅ −R ₈₀₆ ) / (R ₉₁₃ +2 · re) (16) If the value of R ₉₁₃ in equation (16) is set sufficiently larger than the emitter dynamic resistance re, , (16) becomes as follows.

Io = 2 · G ₁ · α · (R ₈₀₅ −R ₈₀₆ ) / R ₉₁₃ (17) In the equation (17), for example, the value of α is 1, (R ₈₀₅ −R).
₈₀₆ ) / R ₉₁₃ is set to 1/2, io = G ₁ (18), and the amplitude of the slope signal Su output from the current control amplifier 9 is the second step current generation circuit 5a. Is equal to G ₁ output from.

Here, as described in the description of the first step current generating circuit 5 and the second step current generating circuit 5a, the value of G ₁ is the step wave output from the first step current generating circuit 5. Since each step value I _{1 to} I _{6 of the} signal is obtained, the amplitude of the slope signal Su output from the current control amplifier 9 finally becomes equal to the step values I _{1 to} I ₆ , and the staircase wave signal E _{1 is obtained.} The slope will be added with high accuracy. In the equation (17), the value of α and (R
_If the value of ( ₈₀₅ −R ₈₀₆ ) / R ₉₁₃ fluctuates or changes due to temperature change, the slope signal Su and the staircase wave signal E ₁ do not fit well, but inside the IC, the ratio of resistance values and transistor matching. In terms of characteristics, etc., the accuracy is very good, so variations in α value and (R ₈₀₅ -R ₈₀₆ ) / R ₉₁₃ value can be almost ignored, and the absolute value of each element is It changes but its ratio does not change. Further, in the case of the present embodiment, the current source circuits 51 to 62 of the first step current generating circuit 5 and the second step current generating circuit 5a, and the current source circuits 81 and 8 of the triangular wave generating circuit 8 are provided.
2. By making the base bias line of the current source circuit 95 of the current control amplifier 9 common, each current source circuit constitutes a current mirror circuit, and the configuration is even stronger against current variations and temperature changes. By adding the slope signal Su to the wave signal E ₁ , a smooth drive signal can be accurately obtained.

In the above embodiment, the current values of the current source circuits 51 to 62 of the first and second step current generating circuits 5 and 5a are set to (1) to (1) to obtain a sinusoidal drive signal.
The current source circuits 51 to 51 are set so as to satisfy the equation (6).
By changing the current value of 62, staircase wave signals of various patterns can be generated, and the current values of the current source circuits 51 and 52, the current values of 53 and 54, the current values of 55 and 56, and the same 57 and 58. By making the current values of, the same 59, 60, and the same 61, 62 current values equal, a slope signal fitted to the staircase wave signal can be accurately generated, and a smoothly varying drive signal can be generated.

Further, in the above embodiment, the rotation detecting means 2 is described as outputting 12 pulse signals per 360 electrical degrees, but the number of pulses is not limited to 12 pulses, for example, rotation. If the detection means 2 outputs 10 pulses per 360 electrical degrees, the level of the staircase wave signal may be changed in 5 steps with the arrival of the pulse edge. In this case as well, the same configuration as that of the above embodiment is used. It is clear that it has the same effect with.

Further, the step controller 3, the slope control circuit 4, the first step current generating circuits 5 to 7, and the second step current generating circuits 5a to 7 shown in the above embodiment.
The specific circuit of a, the triangular wave generation circuit 8, and the current control amplifiers 9 to 11 is merely a specific example, and various circuit configurations having the same function may be considered in addition to the specific circuit shown in the above embodiment. Needless to say.

[0048]

As described above, the brushless motor drive circuit of the present invention can generate a drive current as close as possible to a sine wave with a relatively small-scale circuit configuration, that is, by digital processing with low resolution, and can generate stairs. Since variations and temperature changes can be absorbed even when a slope is added to the wave signal, and a slope signal fitted to the staircase wave signal can be obtained, there is a great effect in suppressing noise and torque ripple during motor rotation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a brushless motor drive circuit according to an embodiment of the present invention.

FIG. 2 is a timing waveform chart for explaining the operation of the brushless motor drive circuit in the embodiment of the present invention.

FIG. 3 is a timing waveform chart for explaining the operation of the brushless motor drive circuit in one embodiment of the present invention.

FIG. 4 is a timing waveform chart for explaining the operation of the brushless motor drive circuit in the embodiment of the present invention.

FIG. 5 is a circuit diagram showing a specific circuit example of a step controller according to an embodiment of the present invention.

6 is a timing waveform chart for explaining the operation of the step controller in FIG.

FIG. 7 is a circuit diagram showing a specific circuit example of a slope control signal generation circuit according to an embodiment of the present invention.

FIG. 8 is a circuit diagram showing a specific circuit example of a first step current generation circuit and a second step current generation circuit according to an embodiment of the present invention.

9 is a waveform diagram for explaining the operation of a specific circuit of the first step current generation circuit and the second step current generation circuit in FIG.

FIG. 10 is a circuit diagram showing a specific circuit example of a triangular wave generation circuit according to an embodiment of the present invention.

11 is a waveform diagram for explaining the operation of a specific circuit of the triangular wave generation circuit in FIG.

FIG. 12 is a circuit diagram showing a specific circuit example of a current control amplifier according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Position detection means 2 Rotation detection means 3 Step controller 4 Slope control signal generation circuit 5-7 1st step current generation circuit 5a-7a 2nd step current generation circuit 8 Triangular wave generation circuit 9-11 Current control amplifier 12 Vertical distribution , Rotation direction switching circuit 13 drive circuit 14 to 16 three-phase stator winding

Claims (3)

[Claims] 1. A position detecting means for detecting a rotational position of a rotor to generate a position detection signal, and a rotation for generating a rotation detection signal having a frequency higher than the position detection signal when the rotor rotates. A detection means, a step controller that generates a timing signal corresponding to each level of the staircase signal whose level is switched stepwise each time an edge of the rotation detection signal arrives, and a current that outputs a current of a predetermined distribution ratio. The current of the mirror circuit is set to O based on the timing signal.
First step current generating means for generating a staircase wave signal by turning off N, OFF, triangular wave generating means for generating a triangular wave signal in synchronization with an edge of the rotation detection signal, and output from the first step current generating means Second step current generating means for generating an output signal relatively equal to the variation width of each level of the staircase wave signal, and the output signal of the triangular wave generating means are input to the second step current generating means. A brushless motor drive circuit comprising: an amplifying means for amplifying the triangular wave signal with an amplification factor proportional to an output current. 2. The triangular wave generating means supplies first and second current source circuits added to a common base of a current mirror circuit and a current of the first current source circuit to a first resistance circuit. And a second voltage generating circuit in which the current of the second current source circuit is supplied to the second resistance circuit. The amplitude of the triangular wave signal is the first voltage generating circuit. 2. The brushless motor drive circuit according to claim 1, wherein the brushless motor drive circuit is configured to be an integral multiple of the voltage difference between the voltage of the voltage generation circuit and the voltage of the second voltage generation circuit. 3. The amplifying means includes a third current source circuit added to the common base of the current mirror circuit, a first differential transistor whose emitters are connected to each other through a resistor, and outputs of the differential transistor. A load transistor for logarithmically compressing a current to convert it into a voltage; and a second differential transistor for exponentially expanding the logarithmically compressed signal,
The amplification factor of the amplification means is equal to the current of the third current source circuit and the second current source circuit.
2. The brushless motor drive circuit according to claim 1, wherein the brushless motor drive circuit is configured so as to be determined by the ratio of the step current generation means to the current.