JPH02276493A - Controlling circuit for sensorless motor - Google Patents

Abstract

PURPOSE:To start stably without generating any abnormal oscillation upon starting by a method wherein the title circuit is provided with a prohibiting means, prohibiting the driving of another one coil for a predetermined period of time upon driving one coil, and a prohibiting time selecting means, selecting a prohibiting time in the prohibiting means. CONSTITUTION:Upon starting, a prohibiting time determined by transistors Q1, Q4, Q7, is specified by a time, in which the charging voltage of respective capacitors C1-C3 is reduced to the voltage of the sum of a saturated voltage between the collector and the emitter of the transistor Q11 and the voltages between respective bases and respective emitters of the transistors Q1, Q4, Q7. The prohibiting time upon normal rotation is specified by a time, in which the charging voltages of respective capacitors C1-C3 is reduced to the voltages of the sum of the forward voltage of a diode D4 and voltages between respective bases and respective emitters of the transistors Q1, Q4, Q7. Accordingly, the prohibiting time may be shortened upon the normal rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a control circuit for a sensorless motor that determines the rotational direction of the sensorless motor.

(Prior Art) Generally, the rotational direction of a motor is controlled by detecting the rotational direction of the motor with a Hall element. On the other hand, sensorless motors do not use any detection elements such as Hall elements, but instead detect the back electromotive force generated in the motor coil and use this as a pseudo sensor signal to control the rotation direction. There is.

FIG. 4 is a circuit diagram showing the configuration of a conventional control circuit that controls the rotational direction of a sensorless motor.

In the figure, UL, VL, and WL are each coil of a three-phase motor, COMI to C0M3 are voltage comparators, and AND1
-AND3 are AND gates, Q1-QLO are NPN transistors, R1-R14 are resistors, D1-D4 are diodes, 01-C3
are each a capacitor, and S is a start detection circuit. In addition, in this circuit, each coil UL, VL, WL
The start circuit for sequentially controlling the on state is omitted.

Next, the operation of the above circuit will be explained using the timing chart of FIG. Now, for example, when the output of AND1 is '1 level, transistor Q2 is turned on,
Furthermore, transistor Q3 is turned on. As a result, current flows from the motor power supply voltage VM to the U-phase coil UL via the transistor Q3. At the same time, capacitor C1 is rapidly charged via transistor Q2.

The charging voltage vC1 is the base of transistor Q3.

Emitter voltage VBE% Forward voltage V of diode D1
, and the base current I of transistor Q3.

It is given by the sum of the voltage drop In-R3 that occurs across the resistor R3. This voltage vC1 is larger than the sum of the base-emitter voltage VBE of the transistor Q7 and the forward voltage vF of the diode D4, so the transistor Q
7 turns on. Then, one input of the Android game) AND3 becomes "OR level," and this Android game's AND3
Since the output of is also at the '0'' level, transistors Q8 and Q9 are turned off, and the current that was flowing through the coil WL until now stops flowing.In other words, this W phase is inhibited,
The W phase changes from the on state to the off state.

On the other hand, at this time, in the V phase, the inverted input voltage of the voltage comparator C0M2 becomes larger than the non-inverted input voltage, and its output becomes "0" level, so no current flows through the coil VL, and this V phase is held in its previous off state.

Similarly, when the ■ phase is turned on and current flows through the coil VL, the U phase is inhibited and held in the off state, and the W
When the phase is turned on and current flows through the coil W L +, the V phase is inhibited and held in the off state.

In this way, current is passed through each coil so that one phase is always on, and by regularly controlling the order in which current flows through each coil, the motor is controlled so that it always rotates in a fixed direction. be done.

(Problem to be Solved by the Invention) By the way, transistors Ql, Q4. During the time when each of Q7 is on, that is, the prohibited time, the initial charging voltage of each capacitor C1 to C3 is equal to the voltage of transistor Q1. Q4. The voltage between each base and emitter of Q7. and the forward voltage V of the diode D4. That is, conventionally, the prohibited time is fixed to a certain value.

By the way, when the motor is rotating steadily, the back electromotive force generated in each coil is sufficiently large, so even if this prohibition time is fixed, no inconvenience occurs.

However, when starting rotation, the following disadvantages occur because the back electromotive force generated in each coil is small. Now, transistor Q5. For example, at time t1 in FIG. 2 when Q6 turns on and the ■ phase changes from the off state to the on state.
Consider the behavior when .

By turning on transistor Q5, capacitor C
2 is charged, which turns off the transistor Q1 and inhibits the U phase, changing the U phase from an on state to an off state. After this, the pre-charged capacitor C1 starts discharging, and the resulting voltage is the base-to-emitter voltage VBE of the transistor Q7 and the forward voltage vP of the diode D4.
When the voltage becomes less than the sum of the voltage, the transistor Q7 turns off and one input of the AND gate AND3 becomes the ``1 m level.At this time, the output of the voltage comparator C0M3 becomes the voltage after the transistor Q7 turns off during normal rotation. Predetermined time “0”
° Maintain level. However, if the back electromotive force of each coil is small, the voltage comparator C
The output of OMB changes to "1" level. As a result, the output of the AND gate AND3 becomes the a1m level, transistors Q8 and Q9 are turned on, and the W-phase coil WL is
Current flows from the motor power supply voltage VM and the W phase turns on. Then transistor Q4 turns on, and the AND gate AN
Since the output of D2 becomes the "OR" level, the transistor Q5, which has been turned on in advance, is cut off. In other words, in this case, abnormal oscillation occurs, which disturbs a stable starting operation.

On the other hand, if the prohibited time is fixed to a long time that satisfies the operation at the start, normal operation cannot be expected during normal high-speed rotation.

This invention was made in consideration of the above-mentioned circumstances, and its purpose is to prevent abnormal oscillation at the time of starting,
An object of the present invention is to provide a control circuit for a sensorless motor that can perform a stable start.

[Structure of the invention]

(Means for Solving the Problems) A control circuit for a sensorless motor according to the present invention includes a prohibiting means for prohibiting the driving of one coil for a predetermined period of time when one coil is being driven, and prohibition in the prohibiting means. The present invention is characterized by comprising a prohibition time selection means for selecting L time.

(Operation) The prohibition time selection means selects a relatively long prohibition time when the motor starts, and selects a relatively short prohibition time during normal rotation.

As a result, a stable start is performed at the time of starting, and stable high-speed rotation is performed during normal rotation.

(Examples) Hereinafter, the present invention will be explained by examples with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of a control circuit for a sensorless motor according to the present invention. In addition, the same reference numerals are attached to the parts corresponding to those in the conventional case for explanation. In the figure, UL, VL
, WL are respective coils of the three-phase motor, and one end of each of these coils is commonly connected to the motor power supply voltage VM.

COMI to C0M3 are voltage comparators, respectively. The voltage at the other end of the V-phase coil VL and the voltage at the other end of the U-phase coil UL are input to the inverting input terminal of the U-phase voltage comparator COMI via resistors R1 and R2, respectively. Furthermore, the voltage at the other end of the W-phase coil WL and the voltage at the other end of the ■-phase coil UL are input to the inverting input terminal of the ■-phase voltage comparator C0M2 via resistors R5 and R6, respectively. Furthermore, W
The voltage at the other end of the U-phase coil UL and the voltage at the other end of the W-phase coil WL are input to the inverting input terminal of the phase voltage comparator C0M3 via resistors R9 and RIO, respectively. Also,
A reference voltage Vr, which will be described later, is input in parallel to each non-inverting input terminal of the voltage comparators COMI to C0M3. In addition,
The values of the resistors R1, R5, and R9 are made equal to each other, and the values of the resistors R2, R6, and RIO are also made equal to each other. That is, the voltages Vu, Vv, and Vw, which are added together via two resistors, are respectively supplied to the inverting input terminals of the voltage comparators COMI to C0M3.

The outputs of the three voltage comparators COMI to C0M3 are input to one input terminal of each of the three AND gates AND1 to AND3. The above three AND gates ANDI~AND
Three NPN transistors Q1. Q4. Each collector of Q7 is connected.

The output terminals of the three AND gates AND1 to AND3 have three NPN transistors Q2, Q5, . Each base of Q8 is connected. These transistors Q2.
Q5. The collector of Q8 is connected to the logic power supply voltage VCC. Further, the transistor Q2. Q5. Each emitter of Q8 is connected to each diode DI, D2 . D3 and NPN transistors Q3. Q6. Connected to each base of Q9. In addition, the above transistor Q
2. Q5. Between each emitter of Q8 and the ground voltage,
Each resistor R4, R8, R12 and each capacitor C1, C2,
C3 are connected in parallel. And above 3
capacitor CI.

Each terminal voltage of C2 and C3 is the voltage of the above transistor Q゛7゜Q.
It is input to each base of 1 and Q4.

Two resistors R13 and R14 and an NPN transistor QIO are connected between the motor power supply voltage VM and the ground voltage.
The collector and emitter of are connected in series, and the reference voltage V is obtained from the series connection point of the two resistors R13 and R14.
The off operation is controlled by the start detection circuit S.

In addition, the three transistors Q1. Q4゜Q7 (7)
Each emitter is commonly connected, and a diode D4 is inserted in the forward direction between this common emitter and the ground voltage. Furthermore, the collector and emitter of an NPN transistor Qll are connected in parallel to the anode and cathode of this diode D4. And this transistor Q
ll on.

The off-operation is also controlled by the start detection circuit S. The start detection circuit S includes each of the coils UL, VL,
The starting time of the motor is detected by detecting the value of the back electromotive voltage generated in WL, and both transistors QIO and Qll are controlled to be in the ON state only during a predetermined period after the start.

Note that in this circuit as well, each coil UL, VL
, WL are omitted.

Next, the operation of the above embodiment circuit will be explained using the timing chart of FIG. 2 and the voltage waveform diagram of FIG. 3.

First, the motor is started by a start circuit (not shown). At this start, the coil is UL.

Since the back electromotive voltage generated in VL and WL is low, both transistors QIO and Qll are turned on by the start detection circuit S for a predetermined period after this start. When the transistor QIO is turned on, the voltage VM is divided by two resistors R13 and R14. Then, this reference voltage V "is R1/R2-R5/R6-R9
When the value of each resistor is set so that /RIO-2, the voltage is lower than VM and 2/3 as shown in Figure 3.
It is set to Vrs higher than that of VM. On the other hand, when transistor Qll is turned on, diode D4
The anode voltage of the collector of the transistor Qll is smaller than the forward voltage of the diode D4.

Set to emitter saturation voltage.

Therefore, at this start, transistor Q1. Q4
．． Q7 inhibits the charging voltage of each capacitor C1 to C3 from the collector-emitter saturation voltage of transistor Qll and transistors Ql, Q4 . Each base of Q7,
It is defined by the time it takes for the voltage to drop to the sum of the emitter voltage. The value of the above voltage is, for example, 0.2V, which corresponds to the collector-emitter saturation voltage of an NPN transistor.

If the voltage between base and emitter is 0.7v, 0.9v
become. Conventionally, this voltage value is given by the sum of the forward voltage of the diode D4 and the voltage between the base and emitter of the NPN transistor, and the value is about 184V, so in this example circuit, this voltage is reduced. The ban will be extended accordingly.

Here, for example, transistor Q5. Let us consider the operation at time t1 in FIG. 2 when Q6 is turned on and the ■ phase changes from the off state to the on state. When transistor Q5 turns on, capacitor C2 is charged, which turns off transistor Q1 and inhibits the U phase.
The phase changes from an on state to an off state. Thereafter, the capacitor C1, which had been charged in advance, starts discharging, and when its voltage becomes below 0.9V, the transistor Q7 is turned off, and the prohibition of the W phase is canceled. However, transistor Q
7 is longer than before, so even if the back electromotive force of each coil is relatively small, the transistor Q
The output of the voltage comparator C0M3 changes to the "0" level before the voltage comparator C0M3 turns off.

As a result, the output of the AND gate AND3 remains at the "0m level", the transistors Q8 and Q9 remain off, and no abnormal oscillation occurs.

On the other hand, when normal rotation occurs after the start, the start detection circuit S turns off both transistors Q10°Qll. When the transistor QIO is turned off, the value of the reference voltage V' is equal to the voltage VM. When the transistor Ql+ is turned off, the anode voltage of the diode D4 is set to its forward voltage. be done.

Therefore, during normal rotation, the transistor Ql.

Q4. The inhibit time due to Q7 is for each capacitor 01 to C3.
The charging voltage of the diode D4 and the transistors Ql, Q4 . Each base of Q7.

It is defined by the time it takes for the voltage to drop to the sum of the emitter voltage. The value of this voltage is, for example, 1.4v. Therefore, during normal rotation, the inhibition time is shorter than when starting, and high-speed rotation becomes possible.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a control circuit for a sensorless motor that can perform a stable start without causing abnormal oscillation at the time of start.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a configuration according to an embodiment of the present invention;
FIG. 2 is a timing chart for explaining the operation of the above embodiment circuit, FIG. 3 is a voltage waveform diagram for explaining the operation of the above embodiment circuit, and FIG. 4 is a circuit diagram of a conventional circuit. UL, VL, WL-yil, 00M1~C0M3...
Voltage comparator, AND1 to AND3...and gate,
Q1~Qll...NPN type transistor, R1-R
14...Resistor, D1~D4...Diode, 01~
C3...Capacitor, S...Start detection circuit. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] In a control circuit for a sensorless motor that sequentially drives each coil of a sensorless motor having a plurality of coils, a prohibiting means for prohibiting driving of another coil for a predetermined period of time when one coil is being driven; 1. A control circuit for a sensorless motor, comprising prohibition time selection means for selecting a prohibition time in the prohibition means.