JPH063998B2 - DC motor control drive circuit - Google Patents

Description

The present invention relates to a control drive circuit for a DC motor, and more particularly to a chopper control circuit capable of reducing energy loss when a relatively large capacity DC motor is turned on.

A control circuit is required to control the rotation direction and speed of the DC motor, but the provision of this control circuit causes energy loss. For example, the one shown in FIG. 1 is a control circuit for chopper-controlling the DC motor M with four transistors T _{r1 to} T _r4 . In this case, the transistors T _r1 to T _r1 .
If T _r4 is used in a completely saturated state, the main loss for driving the motor at that time is the loss that occurs when the transistor passes through the active region during switching of the transistor and the collector-emitter when each transistor is ON. This is the loss of the inter-voltage V _CE . Among them, if the switching time is sufficiently shorter than the chopper cycle, that is, the ON-OFF cycle, V _{CE of the} transistor T _r occupies most of the loss of the chopper type motor drive circuit.
There are various methods for driving the motor in the circuit shown in FIG. 1, but as an example, the transistors T _r1 and T _r3 are transistors for forward and reverse rotation of the motor, and the transistor T
_{Let r2} and T _r4 be speed control transistors. That is,
Assuming that the normal rotation of the motor M is taken in the direction of the figure, the transistor T _r1 is always turned on and the transistor T _r4 is turned on.
-By turning it off, speed control in the forward direction of the motor becomes possible. In the case of reverse rotation of the motor, the transistor T _r3 is always turned on and the transistor T _r2 is turned on and off, whereby the same operation can be performed. The diodes D _{1 to} D ₄ in the circuit shown in FIG. ₁ are freewheeling diodes for power regeneration. In this case, when the motor M is relatively small, in other words, when it is a small power motor, it is possible to use the general-purpose small power type switching transistor by sufficiently saturating the transistors T _{r1 to} T _r4 with a small base current. it can. Since the motor M is increased collector current of the motor current or the transistor T _r1 through T _r4 increases, transistor T _r1 through T _r4, it is necessary to flow a large base current compared to the low-power type of the base resistor There is a problem in that the resistance loss becomes very large when the switch is attached. As a countermeasure for this, as shown in FIG. 2, a means for connecting the respective switching transistors in Darlington connection to obtain the current amplification factor h _FE of the transistors can be considered. With such a Darlington circuit, the total current amplification factor is, for example, h _FE (TOTAL) = h _FE1 × h for the transistors T _r1 and T _r5.
It becomes _{FE5 and} can drive a small base current compared to the high power motor drive circuit using the circuit of FIG. However, when the Darlington circuit is adopted, the switching transistor is not completely saturated, and there remains a problem that a loss corresponding to V _{CE of} the additional transistor occurs. That is, the normal Darlington connection and the complementary Darlington connection are as shown in FIGS. 3A and 3B. Generally, V _CE in the Darlington connection is V _CE (sat) ≈V _BEb +
It becomes V _CEa . Providing a separate supply of T _ra to the V _CE (sat) of the transistor T _rb is the transistor T _ra of V _CE not added is taken generally. In this case, measures are taken so that the voltage between the two power supplies (a) shown in FIG. 4 is usually about 0.6 to 1 V, that is, V _IN2 ≈V _IN1 + (0.6 to 1). This eliminates the apparent V _CE loss of the additional transistor. However, in this case, a problem remains in that a separate power source is required. On the other hand, when an inductive load is added to the switching transistor, the effect of adding a square wave voltage to the load current appears. That is, when the repetitive pulse waveform α is input to the input transistor Tr B as shown in FIG. 5, _assuming that the motor M in FIG. 6 has no inductance L or has a small inductance L, FIG. A pulsating current flows as shown in FIG. When a DC motor is used, it is generally preferable to let a steady current flow through the motor because of the torque characteristics (T∝IaIf) of the motor. Therefore, as shown in FIG. 6, the inductance L is connected and inserted in series with the motor M, and the inductance L is connected to the motor M in FIG.
It is conceivable to flow a steady current as shown in. For example, in the circuit of FIG. 1, when the inductance of the motor M is small, the motor current I becomes close to a triangular wave, but by inserting the inductance in the motor circuit, the smoothed motor current is passed through the motor M. The magnitude L of the inductance to be inserted is determined so that the motor current is sufficiently smoothed and a predetermined ripple voltage L (ΔI / ΔT) = v is obtained. In this case, ΔT is 1 / 2f (f: switching frequency) ΔI is the fluctuation of the motor current, and v
Is set to a value corresponding to the transistor forward voltage V _CE .

The present invention is based on the above-mentioned premise, and an object thereof is to provide a DC motor control drive circuit capable of smoothing a motor current by using an inductance and at the same time reducing a loss due to an apparent V _CE of a Darlington switch transistor. Is.

To this end, the DC motor control drive circuit of the present invention comprises two complementary Darlington-connected transistors for switching for motor rotation direction control and two Darlington-connected transistors for motor rotation speed control. A chopper circuit including a DC motor circuit is configured, a primary side winding of a coil is inserted in the DC motor circuit, and an emitter of a first-stage side transistor of a complementary Darlington-connected transistor from a secondary side winding of the coil and It is configured to supply a voltage between the collectors of the rear side transistors, and the inductance value of the coil is sufficiently smoothed for the motor current, and further,
It is characterized in that the voltage is selected so as to have a desired value.

According to the present invention, with such a configuration, the inductance L inserted in the motor circuit is increased to suppress the current fluctuation amount with respect to the voltage of the chopper circuit as much as possible to maintain the constant torque characteristic of the motor (in the experiment, the current value becomes about 1H. It has been confirmed that the fluctuation disappears), and the ripple component is sent to the secondary side winding in a state where the action of L is not completely eliminated, the energy is smoothed, and the desired Darlington transistor is obtained. A voltage can be supplied.

The details of the present invention will be described below with reference to the drawings illustrating an embodiment.

In FIG. 7, reference numeral 1 is a drive control circuit, and the drive control circuit 1 connects a DC motor M to a power source 4 via a control circuit 2 and a motor circuit 3.

The control circuit 2 includes transistors T _r1 , T _r2 , T _r3 and T _r4.
Are connected as shown. T _r1 and T _r3 are transistors for forward and reverse rotation of the motor, and T _r2 and T _r4 are transistors for speed control. Therefore, if the normal rotation of the motor M is taken in the direction shown in FIG. 7, the transistor T _r1 is always turned on and the transistor T _r4 is _turned on.
-By turning OFF, speed control of the motor M in the forward direction becomes possible. In the case of the reverse rotation of the motor M, the transistor T _r3 is always turned on and the transistor T _r2 is turned on and off, whereby the speed control in the reverse direction becomes possible. Motor circuit 3
Inductors L ₁ and L ₂ are connected in series before and after the motor M. The size of the inductance L (L ₁ , L ₂ ) is Is determined by. Here, ΔT is 1 / 2f (f: switching frequency), ΔI is a fluctuation of the motor current, and v is a ripple voltage having an amplitude value corresponding to the transistor forward voltage V _CE .

The transistor T _r1 makes a complementary Darlington connection together with the transistor T _r5 , and also the transistor T _{r3.
Makes a} complementary Darlington connection with the transistor T _r7 . Then, another power source corresponding to a in FIG. 4 of the transistor T _r5 is a smoothing circuit for smoothing the energy from the triangular waveform including the ripple as shown in FIG. 5 (β) from the inductance L ₁ directly inserted in the motor circuit. Rectified by
The rectified voltage is used. Similarly, the transistor T _r7
The other power source of (1) also uses energy from the inductance L ₂ directly inserted in the motor circuit. In the smoothing circuit, in each complementary Darlington connection, the voltage difference between the power supplies is set to about 0.6 to 1 V, that is, V _IN2 = V _IN1 + (0.6 to 1) by a voltage limiter or the like. This smoothing circuit may have any circuit configuration as long as it has a function as described above. The lower transistors T _r2 and T _{r4 form a} normal Darlington connection together with the transistors T _r6 and T _r8 , respectively. The lower transistors T _r2 and T _r6
The _reason why the complementary Darlington connection with the same separate power supply as the upper part was not used for T _r4 and T _{r8 is} that the loss during switching was more problematic than the loss during use compared to the forward / reverse transistor above. That is, one of the upper transistors is always ON, and the collector loss appears constantly, which is much larger than that of the lower transistor for speed control. Further, when reverse biasing the bases of the switching transistors of all the switching transistors used for these, it is desirable to speed up the switching time of the transistors. The diodes D _{1 to} D ₄ are freewheeling diodes for power regeneration.

In the DC motor control drive circuit configured in this way, the transistors for forward and reverse rotation of the motor are connected in complementary Darlington to increase the current amplification factor of the transistor, and by providing a separate power supply The loss due to V _CE can be eliminated. Further, by inserting the inductances L ₁ and L ₂ into the motor circuit, even when a repetitive pulse waveform is input to the input transistor, a steady current can be passed through the motor M and stable driving can be performed. further,
Particularly importantly, since the above-mentioned inductance L ₁ or L ₂ is used as the separate power supply in the complementary Darlington connection, a separate power supply device is not required as the separate power supply, which is advantageous in terms of energy consumption.

FIG. 8 shows a DC motor control drive circuit according to another embodiment of the present invention. In the embodiment shown in FIG. 8, the inductances L ₁ and L ₂ in the motor circuit shown in FIG. Integrated into one inductance L, and
By connecting diode D, capacitor C, and resistor R around the Darlington connection transistor, reverse bias the base of the transistor at the time of switching, erasing the residual charge remaining in the base, and speeding up the switching time to turn on-off It was done.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a conventional DC motor control drive circuit,
FIG. 2 is a circuit diagram showing a DC motor control drive circuit that requires a larger current than that in FIG. 1, FIG. 3 is a circuit diagram showing an example of Darlington connection, and FIG. 4 is a circuit showing complementary Darlington connection for supplying another power source. FIG. 5 is an explanatory diagram showing current waveforms, FIG. 6 is a motor drive circuit diagram with one power source showing a circuit in which an inductance is inserted in a motor circuit, and FIG.
FIG. 8 is a circuit diagram showing a DC motor control drive circuit according to an embodiment of the present invention, and FIG. 8 is a circuit diagram showing a DC motor control drive circuit according to another embodiment of the present invention. M: Motor, T _r1 , T _{r2 to} T _r8 ... Transistor, L
₁ , L ₂ ... Inductance, D _{1 to} D ₄ ... Regenerative diode.

Claims (1)

[Claims] 1. A chopper circuit including a DC motor circuit is constituted by two complementary Darlington connection transistors for switching for controlling a motor rotation direction and two Darlington connection transistors for controlling a motor rotation speed. A primary winding of the coil is inserted in the DC motor circuit, and a voltage is supplied from the secondary winding of the coil between the emitter of the first-stage transistor and the collector of the second-stage transistor of the complementary Darlington-connected transistor. The DC motor control drive circuit according to claim 1, wherein the inductance value of the coil is selected so that the motor current is sufficiently smoothed and the voltage has a desired value.