JPS5847839Y2 - chiyokuryuumo-tanokudou warmer - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a drive circuit suitable for use in a small brushless DC motor.

FIG. 1 is a principle diagram showing an example of a brushless DC motor to which the present invention can be applied.

In FIG. 1, a rotor 1 is composed of a ring-shaped core 2 and magnets 3.

The magnet 3 is magnetized with NS magnetic poles facing each other over approximately 120 degrees, and this magnet 3 allows a magnetic circuit 4 a
, 4b are formed.

A stator 5 is arranged concentrically inside the rotor 1, and three-phase armature windings 6a, 6b, and 6C are wound around the stator 5 at equal intervals.

Now, when the winding 6a is in the position shown, this coil 6a
When a current (2) as shown in the figure is applied, this current (2) interlinks with the magnetic flux at right angles to generate a rotational force F, and the rotor 1 starts rotating.

Note that at this time, no current flows through the windings 6b and 6C.

Next, when the rotor 1 has rotated approximately 120 degrees, when the current is turned off to the winding 6a and the current is applied to the winding 6b, the rotor 1 further rotates by 120 degrees.

Next, by passing a current through the winding 6C, the rotor 1 further rotates by 120°.

In this way, every time the rotor 1 rotates 120°, the winding 6
The rotor 1 can continue to rotate by repeatedly passing current through a, 6b, and 6C in sequence.

Although the DC motor with two-pole and three-phase windings has been described above, the number of poles can be further increased, and the number of windings can be changed accordingly.

Although FIG. 1 shows an outer rotor type motor, the same principle as described above can also be applied to a so-called inner rotor type motor in which a magnetized rotor is disposed inside a ring-shaped yoke.

In the above brushless DC motor, the winding 6
In order to sequentially flow current through a, 6b, and 6C, a switching element such as a transistor is connected to each winding, and a switching voltage is sequentially applied to each switching element every time the rotor 1 rotates 120 degrees. ing.

This switching voltage can be obtained based on a detection signal from a rotational position detector provided separately (not shown).

Further, when controlling the speed of this DC motor, a speed control voltage obtained by a rotation detector such as a frequency generator or a tachogenerator that is interlocked with the rotor is applied to each winding.

FIGS. 2A and 2B show a conventional example of a DC motor drive circuit for performing the above-described operation.

In FIG. 2A, switching transistors Qa, Q6 .
Switching voltages Esa, Esb, :ESC are sequentially applied to each base of Qc every 120 degrees of rotation angle of the rotor 1.

A speed control voltage EC is applied to the base of the speed control transistor Q1, and the collectors of the transistors Qa and Qb are collectively connected to the collector of the speed control voltage EC.

Therefore, transistor Qa. When switching voltages Esa, Esb, and Esc are sequentially applied to Qb and Qo, and these transistors are sequentially turned on, each winding 6a,
A current corresponding to the rotational speed flowing through the transistor Q1 controlled by the control voltage EC sequentially flows through the transistors 6b and 6C, whereby the rotor 1 is driven to rotate at a predetermined speed.

Figure 2B shows switching transistors QB, Qb+Qo
, Ql, which have polarities opposite to those of B in the figure are shown.

Starting torque T of the DC motor driven by the above circuit configuration and voltage V across each winding 6a, 6b, 6C 1. becomes .

However, K: constant, φ: magnetic flux, R: winding DC resistance, E:
+B power supply voltage, VCES: ) transistor Qa, Q
b.

Let it be the collector-emitter saturation voltage of Qo and Ql.

As is clear from the above formula, each winding 6 a , 6 b , 6
The voltage ■ applied to C is the voltage V of the transistor from the power supply voltage E.

It is equal to E5 minus twice. Therefore, when starting with a low power supply voltage, the starting torque T becomes small.

Therefore, a drive circuit shown in FIG. 3 is used when a motor with a small starting torque is used at a low power supply voltage.

In the figure, drive circuits 7a, 7b, 7C having the same configuration are provided for each winding 6a, 6b, 6C.

In the drive circuit 7a, a control voltage E is applied to the base.

A transistor Q2 to which Esa is applied and a transistor Q3 to which a switching signal Esa is applied to the base are connected in cascade.

The collector of the transistor Q2 is connected to the 10B power supply via the load resistor R1, and is also connected to the base of the next stage transistor Q4.

The emitter of this transistor Q4 is connected to the 10B power supply, and the collector is connected to the base of the driving transistor Qa.

The collector of this transistor Qa is connected to the 1B power supply via the winding 6a, and the emitter is grounded.

The drive circuits 7a7b and 7C also have a similar configuration and have a winding 6b.

6C is a drive transistor Q6. Qc is connected.

According to the above configuration, each transistor Qa, Q6 . Qc is driven in an active state by base voltages each superimposed with a switching voltage EC.

In this case, one drive transistor is connected to one winding, so the voltage VL in both equations becomes large,
Therefore, the starting torque T can be increased.

In the drive circuit of FIGS. 2A and 2B described above, the transistors Qa, Q6 . Even if Qc is conductive in the saturated state, each collector-emitter saturation voltage ■.

, the control voltage E.

The current based on the current is not distributed to each winding 6 a , 6 b , and 6 C at the same rate, resulting in torque unevenness.

Similarly, in FIG. 3, the drive circuits 7 a and 7 b
, 7 C switching voltage Esa, Esb, E
Saturation voltage VCES of transistor Q3 to which sc is applied
If there is a variation in the voltage, this will cause a variation in the emitter potential of the transistor Q2.
The voltage V l- applied to each drive circuit is different, and therefore the control gain is different in each drive circuit, making it impossible to obtain smooth rotational torque.

The present invention is intended to solve the above problem, and it feeds back the voltage of the winding to a speed control element such as transistor Q2, and connects a switching element such as transistor Q1 within this feedback loop. .

An embodiment of the present invention will be described below with reference to FIG.

FIG. 4 shows a DC motor drive circuit of the type shown in FIG. 3 which is capable of low voltage driving, and includes a drive circuit 8a for a winding 6a, and windings 5a and 5c having the same configuration as this drive circuit 8a. It is comprised of drive circuits 8 a and 8 b for.

In the drive circuit 8a, the base of the PNP transistor Q5 is provided with an input terminal 9a for the control voltage EC, the emitter is connected to the 1B power supply via the resistor R2, and the collector is connected to the base of the NPN type tositransistor Q7. and resistance R
3 to the collector of an NPN transistor Q6.

The switching voltage E is applied to the base of this transistor Q6.
An input terminal 10a to which sa is applied is provided, and the emitter is grounded.

The collector of the transistor Q7 is connected to the 10B power supply via the resistor R4, and the PNP transistor Q8ρ
The emitter is connected to the collector of the transistor Q6 via a resistor R5.

The emitter of the transistor Q8 is connected to the 10B power supply, and the collector is connected to the base of the NPN transistor Qa.

The collector of this transistor Q8 is connected to the 1B power supply via the winding 6a, and the emitter is grounded.

Also, the collector of this transistor Q8 and the transistor Q
It is connected to the emitter of No. 5 via a feedback resistor R6.

Note that the drive circuits 8b and 8C also have input terminals 9b and 9C to which the control voltage EC is applied and switching voltages Esb and E.
An input terminal 10b and an IOC to which sc is applied are provided, respectively.

According to the above configuration, transistor Q5. Q7. Q8 and Qa constitute an amplifier with an amplification rate of A.

Then, when the control voltage EC is applied to the terminals 9a, 9b, and 9C, and for example, the switching voltage Esa is applied to the transistor Q6, the transistor Qa becomes conductive and the winding 6a
A current flows depending on the speed.

At this time, the voltage across the winding 6a is fed back to the emitter of the transistor Q5 via the feedback resistor R6.

The feedback amount β of this feedback loop is determined by the ratio between resistor R6 and resistor R2.

The gain G of a feedback amplifier circuit in which a feedback loop with a feedback amount β is connected to an amplifier with an open gain A is generally expressed as follows.

Here, if A is made large enough by setting A>1, then becomes.

That is, if the open gain A of the amplifier is determined to be A>1 by selecting the constant of each transistor and the value of each resistor,
The gain of the entire feedback amplification circuit is determined by the feedback amount β, and the feedback amount β is determined by the ratio of the resistors R6 and R2.

In FIG. 4, a switching transistor Q6 is included in the feedback loop, and if A>1, the collector-emitter voltage of this transistor Q6 is .

Even if E varies among the drive circuits 8 a , 8 b , 8 C, it can be almost ignored.

Therefore, the control system gain is substantially the same for each drive circuit, and torque unevenness can be eliminated.

The present invention provides a DC motor that generates rotational force by sequentially passing a current interlinked with magnetic flux through a plurality of windings, in which an output transistor Qa is connected in series with the winding 6a to a power source. Amplifying circuit Q5. whose open gain is sufficiently larger than 1 for determining the current flowing in Q5. Q7
．． Q8. Q, and a control transistor Q5 included in this amplification circuit and having a base supplied with a speed control voltage EC;
A drive circuit 8a includes a switching transistor Q6 connected in series to the control transistor Q5 to control on/off of the control transistor Q5, and a feedback path R6 for feeding back the voltage of the winding 6a to the control transistor Q5. , relates to a drive circuit for a DC motor characterized in that a plurality of windings 6a, 6b, and 6C are each provided with a drive circuit.

Therefore, according to the present invention, it is possible to eliminate the influence of variations in switching elements, etc. in the winding drive circuit, and the control gain of each drive circuit becomes substantially constant, thereby eliminating torque unevenness.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of a brushless DC motor to which the present invention can be applied, Figs. 2 A, B, and 3 are conventional drive circuit diagrams, and Fig. 4 is a drive circuit diagram showing an embodiment of the present invention. . In addition, in the symbols used in the drawings, 6a, 6b,
6C is a winding, 7a, 7b, and 7C are drive circuits, and R6 is a feedback resistor.

Claims (1)

[Scope of utility model registration request] In a DC motor that generates rotational force by sequentially passing current that interlinks with magnetic flux through multiple windings, there is an output transistor connected in series with the windings to the power supply, and an output transistor connected to the power supply in series with the windings. an amplifier circuit whose open gain is sufficiently larger than 1 for determining the flowing current;
A control transistor included in this amplification circuit and having a base supplied with a speed control voltage, a switching transistor connected in series with this control transistor to control on/off of this control transistor, and a switching transistor that controls the voltage of the winding as above. A drive circuit for a DC motor, characterized in that each of the plurality of windings is provided with a drive circuit having a feedback path that returns to the emitter of the control transistor.