JPH03143293A - Driving controlling circuit for dc motor - Google Patents

Abstract

PURPOSE:To properly control the rotational frequency of a DC motor by giving voltage due to a voltage generating section, to a Zener diode, via an impedance converting section, and by contriving bias current flowing through the Zener diode, to be hardly permitted to flow to the voltage generating section. CONSTITUTION:The combined point of the collector of a transistor Tr3 with a resistor RT is connected to the base of a transistor Tr2, and the emitter of the transistor Tr2 is connected to the anode of a Zener diode Z1, and the collector of the transistor Tr2 is earthed. Then, with the transistor Tr2, an emitter follower is formed, and the impedance converting section of high input impedance/low output impedance is formed. By such composition, most of bias current Iz flows to the side of the collector of the transistor Tr2, and current IB2 flows slightly into the resistor RT from the base.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a drive control circuit that controls the rotational speed of a DC motor.

(Prior Art) A conventional drive control circuit of this type is a PLL (Phase Locked Loop) as shown in FIG.
Circuits using circuits are known. In this circuit, a signal having a reference frequency (S) outputted from a reference oscillator 41 and a signal whose rotational speed of a DC motor 42 can be supplemented by a frequency generator 43 and amplification and waveform shaping are performed by an amplification and shaping circuit are connected in phase. The output of the phase comparator 45 is supplied to a comparator 45 to perform phase comparison and output a pulse (according to the phase difference) as a result of the comparison.The output of the phase comparator 45 is supplied to a low-pass filter 46/\, where it is converted into a DC voltage and sent to a mixer. 47. The output of the amplification and shaping circuit 44 is applied to the F-V converter 48, where it is converted into a voltage corresponding to the frequency, and is applied to the mixer 47, where it is added to the output of the low-pass filter 46. P
The LL circuit alone is provided because it is powerless against two human forces having the same phase and different frequencies. The output of the mixer 47 is applied to a power amplifier 49, subjected to necessary amplification, and then applied to the DC motor 42. As a result, the DC motor 42 rotates at a rotation speed corresponding to the frequency of the output signal of the reference oscillator 41.

However, P L 1. , the drive control circuit using the circuit is complicated because the PLI circuit is integrated into an IC, and the frequency generator 4 is attached to the shaft of the DC motor 42.
3, the structure of the DC motor 42 becomes complicated and large.

On the other hand, there is a proportional current control method as a rotation speed control method when high-precision control such as using a PLL circuit is not required. This method is based on the following theory.

When the DC motor is in rotation, its equivalent circuit is the fifth
As shown in the figure, the back emf E. A series circuit is formed between the DC power source 51 and a resistor Ra made of a wire-wound resistor or the like. Here, the rotation speed of the DC motor is ω, and the back electromotive force constant is 8 (V
/rpm), the load torque is T, and the torque constant is KT (
g-m/'A>, and if the current I and lightning voltage 8 are as shown in Figure 5, then EC-Ke×ω...
...(1) T=KxI, ...
...(2)■8=Ec+■, R0...(3
), and if the current is changed by the load torque T and the voltage is constant, then the back electromotive force E. changes, and as a result, the rotational speed fluctuates.

Therefore, even if the current ■8 changes, the back electromotive force E. The voltage V is constant, that is, the rotational speed is constant.

By changing , constant rotation can be obtained regardless of the load torque T.

In order to realize this principle, the configuration of the drive control circuit shown in FIG. 6 has conventionally been adopted. DC (direct current) motor 5
Power is supplied from the transistor Trl constituting the power amplification section to 0. The electric current mXB flowing into the DC motor 50 through this transistor "rl is detected by the transistor Tr3. A resistor R[ is connected between the power supply ■.0 and the emitter of the transistor Tr3. Also, the power supply V.0 and Connect the resistor R8 and let the current ■ flow through the resistor R3.
Connect the C motor 50 side and the base of the 1-transistor Tr2. A current (2) corresponding to a current of 1° flows through the transistor Tr2 configured in this manner. This current IE is caused to flow through the resistor R1 to generate a voltage 8□, and the voltage generated by this resistor R is increased by V7 by the Zener diode Z1, and the potential is applied to the base of the transistor "rl, and the base and collector of this transistor Tr1 are are connected through resistor R7, and current ■7 is passed through resistor R7 by power source ■.0.
Let it flow.

In the drive control circuit configured as above, when analyzed assuming that each transistor Trl Tr3 is an ideal transistor and the pace emitter voltage ■ BE is zero, ■ a = EC + 8 × Ra ■ a = ■ Z + VR lower VRT - The following equations hold true.

From equations (6) and (7), VRT-(R3,/RE) I8 Substituting this into equation (5) yields xR.

・・・・・・(4) ・・・・・・(5) ・・・・・・(6) ・・・・・・(7) V, = VZ + (R3/'RE) RT x I.

On the other hand, considering equation (4), EC+■8 ・R,a3Vz + (R3/RE
) R Ding Ae.・・・・・・
...(8) is obtained, and by transforming this, EC
V2-I, ((R3/R,E) RT Ra)
becomes. Here, if we set E c −V z, (R3/
'RE)RT Ra"0,', R/R=R/R...(9)S・
Ea-T, and when the relationship of equation (9) holds true, equation (8) holds regardless of Ia, that is, regardless of load torque T. At this time, the rotation speed of the DC motor 50 becomes ω-7/Ko.

With the constants set as described above, a current ■ corresponding to the current ■ is detected in the current detection section including the transistor Tr3.

is detected, and this current ■ is passed through the resistor IRT to create a voltage VR.
The number of rotations of the DC motor 50 can be kept constant by generating a lower voltage and controlling the voltages of the transistors T, 1 forming the power amplifying section via the Zener diode Z1.

(Problems to be Solved by the Invention) However, the above-mentioned analysis of the conventional DC motor drive control circuit was performed in an ideal state, and in reality, the bias current , flowing through the Zener diode z1, flows directly into the resistor RT. RT = IE + 1Z, and Ia that should be obtained from equations (6) and (7)
There was a problem in that the relationship ``oCVRT'' did not occur, and the rotation speed could not be controlled accurately.

Furthermore, the pace emitter voltage ■B is applied to the transistor "r3.
Since E actually exists, instead of formula (7), ■aR3:
There was a problem in that the following equations were established, the value of the current (2) was detected to be smaller than the actual value, and the rotational speed could not be controlled accurately.

The present invention was made to solve the problems of the conventional DC motor drive control circuit, and its purpose is to provide a drive control 111i1D path that can accurately control the rotational speed of a DC motor. be.

[Structure of the Invention (Means for Solving the Problems) Therefore, the present invention includes a power amplification section that receives bias control via a Zener diode and supplies power to a DC motor, and a power amplification section that receives power through the Zener diode. a current detection section that detects the current flowing to the DC motor via a transistor; a voltage generation section that generates a voltage corresponding to the current detected by the current detection section; and a voltage generation section that generates a voltage corresponding to the current detected by the current detection section; A drive control circuit for a DC motor was constructed by including an impedance conversion section with a high input impedance and a low output impedance that converts the impedance and supplies the impedance to the Zener diode.

Furthermore, in the present invention, in addition to the above configuration, the transistor of the current detection section is of a bipolar type, and a voltage drop element that produces a voltage drop equal to the base-emitter voltage is provided in the path of the current to be detected in the current detection section. A DC motor drive control circuit was constructed by connecting them.

Furthermore, in addition to the above configuration, a phase compensation section for compensating the phase of the output of the power amplification section is connected to the path through which the detected current of the current detection section reaches the voltage generation section, thereby configuring a DC motor drive control circuit. .

Further, a DC motor drive control circuit was constructed by adding a switching section for starting/stopping power supply by the power amplifying section in response to an external control signal to the above structure.

Furthermore, in addition to the above configuration, a DC motor drive control circuit is constructed by including an overcurrent detection section that generates a control signal to turn on and off the switching section based on the zero voltage generated in the voltage generation section.

(Function) According to the configuration of the first invention, since the voltage from the voltage generation section is applied to the Zener diode via the impedance conversion section, almost no bias current flowing through the Zener diode flows to the voltage generation section, thereby controlling the rotation speed. can be done more accurately.

According to the second invention, the same voltage drop as the voltage drop due to the base-emitter voltage of the bipolar transistor 0 is generated in the path of the current flowing to the DC motor, and the current to be detected is not affected by the base-emitter voltage. It becomes a current, allowing for more accurate rotational speed control.

According to the third aspect of the invention, the phase of the electric power supplied to the DC motor is compensated, so that the so-called oscillation phenomenon is eliminated, and the rotation speed can be controlled more accurately (stablely).

According to the fourth invention, the DC motor can be turned on and off as needed by switching, and the rotation speed can be controlled more accurately.

Furthermore, according to the fifth invention, when an overcurrent flows through the DC motor and the voltage generated by the voltage generator increases, the DC motor can be stopped, and the rotation speed can be controlled more accurately (safely).

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. Fig. 1 shows an example of the present invention.

In the same figure, the same components as in Figure 6 have the same number. , and the explanation thereof will be omitted.

In the embodiment shown in FIG.
The resistor RT that generates the voltage "RT" and the anode of the Zener diode Z1 are coupled by an impedance conversion section consisting of the transistor Tr2, and the voltage generated in the resistor R1 is applied to the anode of the Zener diode Z1.Specifically, , the junction between the collector of transistor Tr3 and resistor RT is coupled to the base of transistor Tr2, the emitter of transistor "r2 is coupled to the anode of Zener diode Z1, and the collector of transistor Tr2 is grounded. As a result, the transistor "r2 constitutes an emitter follower and constitutes an impedance conversion section with high input impedance and low output impedance. With this configuration, most of the bias current Iz flows to the collector side of the transistor "r2, and the bias current Iz flows from the base to the resistor. 2 is smaller than the current flowing into RT. That is, if the current amplification factor of the transistor ``r22'' is hfe, then ■B2'' = ■Z /hfe ・'・I B2 (I E ) Even if the current of Ip + IB2 flows into the resistor R, the influence of As much as possible.

Furthermore, in the embodiment of FIG. 1, in order to eliminate the error between the detected current (1) and the detected current (8) due to the pace-emitter voltage VBE3 of the transistor "r3, the diode D1, which is a voltage drop element, is connected to the current T. Specifically, the anode of the diode D1 is connected to the resistor R8,
The cathode was connected to the base so that a current 8 would flow from the cathode to the collector of the transistor Trl. Here, when the current 8 flows, the voltage drop f1 caused by the diode D1 is the pace emitter voltage VBE3.
Use a diode that is equal to . Then, ■aR3+Vf1=■ERE×BE3Here, Vf
1×BE3 Therefore, I aR3''E−I E RE 3 , formula (7) is realized, and errors in electric current and detection can be reduced.

Furthermore, in the embodiment shown in FIG. 15, the collector of the transistor Tr3 is grounded via a capacitor C, which is a phase compensation section. With this configuration, it is possible to eliminate the situation where the DC motor 50 is in a so-called oscillation state due to a change in the phase of the electric power (voltage and current) applied to the DC motor 50 due to the conventional proportional current control method, and to perform phase compensation. (voltage and current), making it possible to stably rotate the DC motor 50.

In Fig. 2, in order to control the stop/start of rotation of the DC motor 50 from the outside (controller), in addition to the configuration shown in Fig. 1, a transistor Tr4 is provided, the collector of which is the base of the transistors T and 1, and the emitter is grounded. , an on/off control signal is given to the base via the signal line 30.

A power supply ■ is connected to the signal line 30 via a resistor R1. C is given. According to this configuration, when the controller applies an H level control signal to the signal line 30, the transistor Tr
A voltage of 0.7V or more is applied to the base 4 of 4, and the 1 helangistor Tr
4 is turned on, the transistor Tr1 is cut off, and the DC motor 50 is stopped. On the other hand, signal line 3
When an L level control signal is applied to the transistor Tr
A voltage of 0.7V or less is applied to the base of the DC motor 4, the transistor "r4 is cut off, and the rotation of the DC motor 50 is controlled.

FIG. 3 shows a circuit configuration in which a configuration for stopping the rotation of the DC motor 50 when an overcurrent flows to the DC motor 50 is added to the circuit configuration shown in FIG. Here, a Zener diode Z2 is connected between the base of the transistor Tr2 and the signal line reaching the bases of the transistors T and 4. The Zener voltage V72 of the Zener diode Z2 is set to be smaller than the voltage (2) RT that occurs across the resistor R1 when the current (18) becomes larger than a predetermined value and an overcurrent flows through the DC motor 50 FL. In addition, the anode of the Zener diode and the resistor R1
A diode D2 for preventing backflow is connected between the two. According to this configuration, when the DC motor 50 is locked due to a mechanical abnormality and the maximum current flows, the power supply to the DC motor 50 can be stopped in the following manner for protection.

Under current, IE has the relationship I a KIF as mentioned above, and ■a becomes ■RT. Here, if the current Ia flowing into the DC motor 50 is suppressed, the current value at this time becomes ■E1. ■a
1. Assuming the voltage value is ■8t, ■alR3= 1E1RE
□ VRTl −■EIRT,', ENG aI
Rs” (RE,/RT) VRTl
−'= VRTI −I al (R3RT / R
E > Therefore, if you select the Zener voltage V72 that becomes 1a1 (R8R1/RE) - VRT1 = V12 + BE4, the DC motor 50
When an abnormality occurs and a current ■8 of ■, >■a1 flows, the Zener diode Z2 surrenders and ■Z2 flows and turns on the transistor Tr4, so the transistor Tr1 is cut off and current flows to the DC motor 50. Engineering. This will prevent the influx of people and provide protection.

6 [Effects of the Invention] As explained above, according to the present invention, errors in rotation speed control due to non-ideal circuitry, which is a drawback of the current proportional system, can be reduced, and rotation can be controlled stably and safely. This has the effect that the rotational speed of the DC motor can be accurately controlled as a whole.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of one embodiment of the present invention, Figures 2 and 3 are circuit diagrams of other embodiments of the present invention, and Figure 4 is a block diagram of a DC motor drive control circuit using a PLL circuit. 5 is a diagram showing an equivalent circuit of a DC motor, and FIG. 6 is a diagram showing a drive control circuit for a DC motor using a conventional current proportional method. 50...DC motor "rl~"r4...Transistor Z1. Z2... Zener diode D1. D2...Diode R3, RE, RZ, R,, R1=°゛Resistor C...Capacitor

Claims (5)

[Claims] (1) A power amplification unit that receives bias control via a Zener diode and supplies power to the DC motor, and a current detection unit that detects the current flowing to the DC motor via the power amplification unit via a transistor. a voltage generating section that generates a voltage corresponding to the current detected by the current detecting section; and a high input impedance, low output impedance, converting the impedance of the voltage generated by the voltage generating section and applying it to the Zener diode. A DC motor drive control circuit equipped with an impedance conversion section. (2) The transistor of the current detection section is of a bipolar type, and a voltage drop element that produces a voltage drop equal to the base-emitter voltage is connected to the passage of the current to be detected in the current detection section. Claims (
1) Drive control circuit for the DC motor described above. (3) A phase compensation section for compensating the phase of the output of the power amplification section is connected to the path through which the detected current of the current detection section reaches the voltage generation section. 2
) Drive control circuit for the DC motor described in ). (4) The DC motor according to any one of claims (1) to (3), further comprising a switching unit that starts/stops power supply by the power amplification unit based on an external control signal. Drive control circuit. (5) Claims (1) to (4) further comprising an overcurrent detection section that generates a control signal for turning on and off the switching section based on the voltage generated in the voltage generation section.
) A drive control circuit for a DC motor according to any one of the above.