JPH03198689A - Drive circuit of motor - Google Patents

Abstract

PURPOSE:To suppress deviation of a driving voltage based on an early effect of a transistor in a comparing voltage forming circuit by applying the output of a voltage booster to the forming circuit to depend a comparing voltage upon a first power source voltage. CONSTITUTION:When a power source voltage VS is applied to the base of a control transistor Q31, a voltage of the voltage VS=VS+2VD (VD: forward voltage of diodes D1, D2) is output from the emitter of an output transistor Q32. The voltage VS depends upon the voltage VS without depending upon a power source voltage VCC, and is set to a voltage always higher by 2VD than the voltage VS. Accordingly, the voltage VS is applied to an input terminal IN to suppress an early effect of transistors Q2, Q4, Q12, Q14, Q22, Q24 to output suitable driving voltages U, V, W. As a result, a motor performs normal rotation.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a motor drive circuit.

(b) Prior Art FIG. 2 is a circuit diagram showing a conventional motor drive circuit used for a capstan motor of a VTR, etc., and shows a drive voltage U for driving a three-phase motor.

It outputs V and W.

In FIG. 2, the area inside the one-dot chain line is the second power supply voltage ■.

This is a comparison voltage creation circuit S that creates a comparison voltage by applying C to an input terminal IN. In the comparison voltage generation circuit S, Il+Il+I are alternating currents obtained by each three-phase Hall element detecting the rotational position of a motor (not shown), and have a phase shift of 120 degrees. , current mirror circuit CM, , CM, , CM,
is supplied to Transistors Q, ,Q, ,Q, ,Q, constitute a current mirror circuit, and transistors Q,
, Q, the current mirror circuit CM,
A collector current proportional to the output current flows. Also, transistors Q, , Q6 . Q constitutes a current mirror circuit, and a collector current proportional to the collector current of transistor Q6 flows through the collector of transistor Q5. Similarly, transistor Q Il+ Q I
f Q I3. Q11 constitutes a current mirror circuit, and the collector of transistor Qt+Q++ is
A collector current flows that is proportional to the output current of the current mirror circuit CM. Similarly, transistor Q! l
+Q2! +Qsr, Ql( constitute a current mirror circuit, and a collector current proportional to the output current of the current mirror circuit CM flows through the collector of the transistor Q t 2+ Q t 1. Note that the transistors Q , Q ,.

Q21, Q, Q, ,Q, , are each the same size.

Here, transistor Q ++ Q + 4. Q!
Since the collectors of the + terminals are commonly connected, the collector of the transistor Q6 is connected to the collector of the transistor Q1! Q l
A combined collector current of 11 Q 21 flows. Also, the transistors Q 5Q , Q , , Q , 5Q , Q
,,Q2. Since Q and Q each constitute a current mirror circuit, the transistor Q6+ Q+s+ 0
2g carries the same collector current proportional to the combined current flowing through the collector of transistor Q6. Therefore, the currents III with a phase shift of 120 degrees from each other
II and II are current mirror circuits CM, CM, , respectively.
When supplied to CM, the difference current H1 between the collector currents of transistors Q, , Q, and transistor Q l 1+ Q
l 1 collector current difference current H7, transistor Q
A difference current H8 between the collector currents of 2L+02N is output as a comparison current for the drive voltages U, V, and W, respectively.

The non-inverting input terminal (+) of the operational amplifier OP1 has a reference voltage V5/
2 is applied, and the inverting input terminal (-
), the comparison current H1 is input resistor R6 and feedback resistor R2
The operational amplifier OP outputs a driving voltage U. Similarly, from the operational amplifiers OP, , OP, the driving voltage
, W are output. Incidentally, the amplitudes of the drive voltages U, V, and W are varied according to the power supply voltage 5 applied to the operational amplifiers op, , op, , op (drive voltage generation circuit).

With the above configuration, the three-phase motor rotates by applying drive voltages having a phase shift of 120 degrees to the drive coil.

(c) Problems to be Solved by the Invention In FIG. 2, the power supply voltage V. 0 must be higher than the power supply voltage V5 in order to operate the comparison voltage generation circuit. However, when the power supply voltage ■cc is much larger than the power supply voltage ■5, the transistor Q 2 + Q ++ Q +
2+ Q Il+ Q tl+ The collector-emitter voltage of Q ff1l increases depending on the power supply voltage ■cc, and the transistor Q ++ Q 4+ 01
2+ Q 11+ Q! ! The collector current of +Q 21 becomes larger than the originally required current value due to the rounding effect of the PNP transistor. As a result, the differential current H,,H,,H, deviates from the originally required value, and accordingly, the drive voltages V,V.

W also deviates from the originally required value, and as a result,
There was a problem that uneven rotation of the motor occurred.

For example, in the case of a type in which the upper and lower limits of the amplitude of the comparison currents H1, Hx, and Hs are limited to predetermined values, the upper and lower limits of the amplitude of the comparison currents H, , H, , H, Even if the currents fluctuate, uneven rotation of the motor will not occur, but if the center of the amplitude of the comparison currents H, , H, , H1 changes due to the arc effect, uneven rotation of the motor will occur.

When using the motor as a capstan motor,
If an unstable state occurs while the motor is rotating at a low speed, there is a problem in that it causes wow and flutter such as uneven color on the screen and undulating sound.

(d) Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and it generates a drive voltage for driving a motor by applying a reference voltage and a comparison voltage, The motor also includes a drive voltage generation circuit in which the amplitude of the drive voltage is varied according to a first power supply voltage of the motor, and a comparison voltage generation circuit that creates the comparison voltage based on a second power supply voltage. ,
In a motor drive circuit that controls the rotation speed of the motor according to the amplitude of the drive voltage, a voltage increase circuit that increases the first power supply voltage by a predetermined amount is provided, and the output of the voltage increase circuit is set to the comparison voltage. The comparison voltage is made to depend on the first power supply voltage by applying it to a generation circuit.

(E) Effect According to the present invention, the comparison voltage is made dependent on the first power supply voltage by applying the output of the voltage increase circuit to the input of the comparison voltage generation circuit. It is possible to minimize deviations in driving voltage due to the earth effect of the transistor.

(f) Example The details of the present invention will be specifically explained with reference to the drawings.

In FIG. 2, which shows a conventional motor drive circuit, transistors Q 1+ Q 1+ 012+ Q +1+
Q22+Q Supply voltage within the range that does not saturate Ill
If cc is set higher than the power supply voltage ■5, the transistor QI Q4+ Qll O+4+ Q22
+ Q24's arch effect can be suppressed. In other words, if the comparison voltage generation circuit S is operated based on the power supply voltage (2), which is a voltage of more than ten volts, the above-mentioned round effect can be suppressed.

However, due to circuit design, it may not be possible to set the power supply voltage vc0 as described above. Transistor Q.

Q, ,Qll QllI Qll This problem is serious because the collector-emitter voltage of Qllll depends on the power supply voltage ■Co.

FIG. 1 is a circuit diagram showing a voltage increasing circuit according to the present invention, and the above problem is solved by applying the output of the voltage increasing circuit to the input of the comparison voltage generating circuit S.

In FIG. 1, control transistor Q9. The collector is grounded and the emitter is a diode D.

connected to the cathode of The anode of the diode DI connected in series with the diode D2 is connected to the power supply voltage Vco via a resistor R1. Also, the output transistor Q
1. The base is connected to the emitter of the control transistor Q31 via two stages of diodes D, , D, and the collector is connected to the power supply voltage VCC. Then, by applying the power supply voltage 5 to the base of the control transistor Q12, the voltage V
5'=V5+2VD (VD' diode D +,
A voltage of D (forward voltage of t) is output. The voltage V5
' is the power supply voltage V5 without depending on the power supply voltage ■cc
, and is always set at a potential 2゜ higher than the power supply voltage V5. Therefore, by applying the voltage 5' to the input terminal IN in FIG.
+Q 1+ Q 12. Q 11+ Q 2t+ Q
The arc effect of 21 is suppressed as much as possible, and the drive voltage U is appropriate.
, V, and W are output, and as a result, the motor rotates normally.

As described above, the comparison voltage applied to the inverting input terminals of the operational amplifiers op, , op, , op does not depend on the power supply voltage Vcc but depends on the power supply voltage V5, so that the motor can rotate normally. In particular, when the circuit of the present invention is used in a VTR capstan motor drive circuit, wow and fluff
(g) Effects of the Invention According to the present invention, the comparison voltage applied to the drive voltage generation circuit is independent of the second power supply voltage and is equal to the first power supply voltage. Therefore, it is possible to suppress the deviation of the drive voltage as much as possible based on the rounding effect of the transistor inside the comparison voltage generation circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a voltage increasing circuit according to the present invention, and FIG. 2 is a circuit diagram showing a conventional motor drive circuit. S... Comparison voltage creation circuit, OP+, Op,, op. ...Comparator, Ql, ...Control transistor, Q
8. ...output transistor, D,,D,...diode.

Claims (2)

[Claims] (1) A drive voltage that generates a drive voltage for driving a motor by applying a reference voltage and a comparison voltage, and in which the amplitude of the drive voltage is varied according to a first power supply voltage of the motor. A motor drive circuit comprising: a generation circuit; and a comparison voltage creation circuit that creates the comparison voltage based on a second power supply voltage; the motor drive circuit controls the rotation speed of the motor according to the amplitude of the drive voltage; A voltage raising circuit is provided to raise the first power supply voltage by a predetermined amount, and an output of the voltage raising circuit is applied to the comparison voltage generation circuit, thereby making the comparison voltage dependent on the first power supply voltage. Characteristic motor drive circuit. (2) The voltage increase circuit includes a control transistor whose output path is connected between one power source and the other power source, and a diode connected between the one power source and the output path of the control transistor; an output transistor whose input is connected to an output path of the control transistor through the diode, and applying a first power supply voltage to the input of the control transistor increases the voltage by a predetermined amount from the first power supply voltage. 2. A motor drive circuit according to claim 1, wherein the increased voltage is obtained from an output path of said output transistor.