JP2571582B2 - DC motor speed controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a speed control device for a DC motor.

2. Description of the Related Art An apparatus for controlling the speed of a DC motor using a speed control IC is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-207890. As shown in FIG. 3, this conventional device comprises a first terminal connected to a positive terminal of a power source (3) via a first resistor (4) having a positive temperature characteristic as an external passive element; A second terminal connected to the positive terminal via a DC motor (1), a third terminal grounded, a fourth terminal grounded via a second resistor (5),
A third resistor as an external passive element between the terminal and the terminal (6)
A constant current transistor (7) having an emitter connected to the fourth terminal and a collector connected to the fifth terminal, and one input terminal connected to the collector of the constant current transistor (7). And an error amplifier (8) whose other input terminal is connected to the second terminal, wherein the first terminal is always configured to flow in proportion to the current flowing to the second terminal. A DC motor which generates a voltage corresponding to the back electromotive force of the DC motor (1) between the fifth terminals and operates as a constant power source having a negative internal resistance having an absolute value equal to the internal resistance of the DC motor. It constitutes a speed control IC (2).

Problems to be Solved by the Invention However, in this conventional example, the IC (2) is provided with a fourth terminal for compensating for a change in speed based on the temperature coefficient of the DC motor, and the fourth terminal is provided with a constant current transistor (7).
And a second resistor (temperature-sensitive resistance element) (5) having a negative temperature coefficient is externally connected to the fourth terminal. Therefore, the number of IC terminals increases by one, and an expensive temperature-sensitive resistance element is required, which is disadvantageous in terms of space and cost.

The present invention has been made in view of such a point,
An object of the present invention is to provide a control device for a DC motor in which a temperature coefficient of the DC motor is compensated by a configuration in an IC.

Means for Solving the Problems In order to achieve the above object, according to the present invention, a first terminal connected to a power supply plus terminal via a first resistor having a positive temperature coefficient, and a DC motor A second terminal connected to the first terminal, a third terminal grounded, and the first terminal.
A fifth terminal to which a third resistor is connected between the first terminal and the fifth terminal, wherein a current proportional to a current flowing through the second terminal always flows through the first terminal; A speed control device for a DC motor including a DC motor speed control IC for generating a voltage corresponding to a reverse voltage of the DC motor between the terminal and a terminal, wherein the IC has an emitter connected to the third terminal and a collector connected to the third terminal. A first constant current transistor connected to the five terminals; an error amplifier having one input terminal connected to the collector of the constant current transistor and the other input terminal connected to the second terminal; the current I ₁ current I ₂ flowing in the current transistor is a current mirror
And a mirror current supply means for supplying a reference voltage source having no temperature characteristic, one end of which is connected to the plus side of the reference voltage source and the other end of which is an emitter of a PNP transistor. first and IC resistor connected to the negative side of the reference voltage via the inter-base to determine the I _1,
A second IC resistor inserted between the base of the PNP transistor and the negative side of the reference voltage source; a second end of a diode having one end connected to the negative side of the reference voltage; third and IC resistor connected, which is connected to the other end of the diode consists of a second constant-transistor flowing a current to the current mirror to the I _1, the second IC resistor and the third IC resistor Are determined so as to compensate for the temperature coefficient of the DC motor.

According to such a configuration, the temperature coefficient of the DC motor is compensated, so that the rotation speed of the DC motor can always be kept constant irrespective of the temperature, and the speed control IC requires only a small number of terminal pins. Since temperature compensation can be realized by the ratio of two resistors formed in the IC, there is no need to externally attach a temperature-sensitive resistance element.

EXAMPLE In FIG. 1 embodying the present invention, the same parts as those in FIG. In this embodiment, the fourth terminal is not provided in the IC (2), and the emitter of the constant current transistor (hereinafter referred to as "first constant current transistor") (7) is connected to the third terminal for grounding. I have. The constant current I _{2 of} the first constant current transistor (7)
It is determined in the form of current mirror current I _1. The mirror current supply circuit for providing the I ₁ (9), first the I ₁ means the temperature characteristic nor a reference voltage source for determining (10), connected to both ends of the reference voltage source (10) A first IC resistor (R ₁ ) and the emitter-base of the PNP transistor (11). That is, the voltage of the reference voltage power supply V ₀ (10), when the V _EB and emitter-base forward voltage of the PNP transistor (11), I ₁ is _{I 1 = (V 0 -V EB} ) /
R ₁

By the way, in the above equation, the resistance (R ₁ ) has a positive temperature coefficient, and V _EB has a negative temperature coefficient. However, since V _EB changes greatly with temperature, for example, when the temperature rises, I ₁ also increases. In order to compensate for this, a diode (12) composed of a transistor and the second and third IC resistors (R ₂ ) and (R ₃ ) are connected as shown in FIG. resistance conduction voltage V _{EB of) (R 2) (R 3} ) obtained by dividing the voltage value _{V EB · R 2 / (R} 2 + R 3) occurs. here,
Since V _EB has a negative temperature characteristic, the temperature characteristic of the voltage at the point (a) acts to offset the temperature characteristic of V _EB of the PNP transistor (11).

The other end of the diode (12) is connected to the second constant current transistor (15) which mirrors the I _1. The emitter of the second constant current transistor (15) is also connected to the third grounding transistor.
Connected to terminal. The collector of the PNP transistor (11) is connected to the transistor (14) via another PNP transistor (13). This transistor (14)
Are connected to each other, and the emitter is connected to the third terminal. The base is commonly connected to the bases of the first and second constant current transistors (7) and (15). Further, the collector and the base of the transistor (14) are connected to the plus side of the reference voltage power supply (10) via a high resistance (16). The positive terminal of the reference voltage power supply (10) is connected to the positive terminal of the external power supply (3) via the sixth terminal of the IC (2).

By the way, the ratio R _{2 of} the second and third IC resistances (R ₂ ) and (R ₃ )
/ R ₃ contributes to the temperature coefficient of the constant current I ₂ as shown in FIG. Thus, the rotational speed of the DC motor be determined R ₂ / R ₃ so as to compensate for the temperature coefficient of the DC motor becomes constant irrespective of the temperature. When specifically a temperature coefficient of about -0.12% / ° C. ferrite magnet of the DC motor (1), corresponding to a point where the temperature coefficient of the second FIG I ₂ becomes equivalent and the temperature coefficient of the ferrite magnets (P) R ₂ / R ₃
Should be set.

In this embodiment, PNP transistor (13) is provided in order to reduce the variation of the current I ₁ due to the voltage fluctuation of the power source (3). The voltage fluctuation of the power supply (3) is unavoidable especially when it is a battery, and a large potential difference occurs at the beginning of use and during the life of the battery. PNP transistors in means for determining a constant current I ₁ (11) is not good constant current with respect to it because voltage variations are PNP type, another PN
By providing the P transistor (13), the constant current fluctuation can be reduced.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various changes and modifications can be made without departing from the gist of the invention described in the appended claims.
Modifications are possible.

Effect of the Invention According to the present invention, the means for making the rotation speed of the DC motor constant regardless of the temperature is realized by two resistors provided in the IC, so that the number of external terminals of the speed control IC is reduced. This eliminates the need for externally attaching an expensive temperature-sensitive resistance element, which is advantageous in terms of cost and space.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a DC motor speed controller embodying the present invention, and FIG. 2 is an explanatory diagram thereof. FIG. 3 is a circuit diagram of a conventional example. ... First terminal,... Second terminal,... Third terminal,... Fifth terminal, (1) DC motor, (2) Speed control IC, (3) Power source, (4) )... First resistor, (6)... Third resistor, (7)... First constant current transistor, (8)... Error amplifier, (9)... Mirror current supply circuit, (10). ... reference voltage source, (11) ... PNP transistor, (12) .... diodes, (15) .... the second constant current transistor, (R ₁₎ (R ₂₎ (R ₃₎ ...... first, second 2, the third IC resistor.

Claims (1)

(57) [Claims] 1. A first terminal connected to a power supply positive terminal via a first resistor having a positive temperature coefficient, a second terminal connected to a power supply positive terminal via a DC motor, and grounded. A third terminal, and a fifth terminal to which a third resistor is connected between the first terminal and the second terminal.
A DC motor speed control IC configured to flow a current proportional to a current flowing through the terminal and having a DC motor speed control IC for generating a voltage corresponding to a reverse voltage of the DC motor between a first terminal and a fifth terminal; In the control device, the IC includes:
An emitter is connected to the third terminal and a collector is connected to the fifth terminal.
A first constant current transistor connected to a terminal; an error amplifier having one input terminal connected to the collector of the constant current transistor and the other input terminal connected to the second terminal; current I ₂ flowing through the transistor and a mirror current supply means for supplying a current I ₁ to the current mirror, said mirror current supply means includes a reference voltage source having no temperature characteristics, one end of the reference voltage source first and IC resistor and the other end connected to the plus side is connected to the negative side of the reference voltage through the emitter-base of the PNP transistor to determine the I _1, base and the reference voltage source of the PNP transistor A second IC resistor inserted between the other end of the diode and a third IC resistor connected to the other end of the diode having one end connected to the minus side of the reference voltage and the base of the PNP transistor. When, the electric current to the current mirror to the I ₁ is connected to the other end of the diode 2
A constant current transistor, wherein the ratio of the second IC resistance to the third IC resistance is determined so as to compensate for the temperature coefficient of the DC motor.