JPS6253189A - Braking circuit for dc motor - Google Patents

Abstract

PURPOSE:To reduce the effect of noises on other electrical parts by connecting a switching element between power applying terminals for a motor, bringing the switching element to an ON state and applying braking to the motor. CONSTITUTION:When a switch 3 is closed, a motor M is supplied with the DC voltage of a battery 2 through a diode 7, and the motor M is turned. When the switch 3 is turned OFF, a transistor 8 is brought to an ON state by back electromotive force generated in the motor M. Accordingly, both terminals T1, T2 for the motor M are short-circuited, thus applying braking to the motor M.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a braking circuit suitable for use in braking a DC motor used primarily in automobiles.

"Prior Art" In automobiles, direct motors are used to drive power windows and the like. By the way, this type of DC motor may be braked when stopped, and in this case, electrical braking may be applied.

FIG. 2 is a diagram showing the configuration of a conventional motor drive circuit. When the common terminal C of the switch 1 is connected to the terminal, the voltage of the battery 2 is supplied to the motor M, and the motor M rotates. Furthermore, if common terminal C and terminal B of switch 1 are connected, the voltage supply to motor M is cut off, and a short circuit is created that shorts terminals 'I'1 and T2 of motor M. A current II due to the back electromotive force generated in the motor M flows through the circuit, and the motor M is thereby electrically braked.

"Problems to be Solved by the Invention" By the way, in general, switch l and motor M are provided at separate locations, so the wiring connecting switch l and motor M becomes long, and for this reason, when motor M stops, There is a problem in that the two-way current 11 in the circuit becomes a noise source for other electronic components. When electronic components such as microcomputers are installed in automobiles, as is the case these days, it is necessary to prevent the generation of such noise as much as possible.

This invention has been made in view of the above-mentioned circumstances, and is designed to reduce as much as possible the influence of noise generated when electrically braking a DC motor. is intended to provide.

[Means for Solving the Problems] The present invention provides a braking circuit for a DC motor driven by a DC power supply supplied via an opening/closing means, in which a braking circuit is provided between two power supply terminals of the DC motor directly or with a resistor. and a switch element control circuit that turns off the switch element when the opening/closing means is in a closed state and turns on the switch element when the opening/closing means is in an open state. It is characterized by

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention. In this figure, 2 is a battery, 3 is a motor M.
4 is a brake circuit according to the embodiment. This braking circuit 4 includes a variable resistor 5 and a resistor 6 inserted in series between the power supply lines, a diode 7 inserted into the positive power supply line, an emitter connected to the cathode of the diode 7, and a base connected to the variable resistor 5 and the resistor. At the connection point of 6,
It is composed of transistors 8 (switch elements) each having a collector connected to a negative power supply line. In addition, the variable resistor 5 mentioned above. Resistance 6. The diode 7 constitutes a switch element control circuit 9.

In the above configuration, when the switch 3 is turned on, the DC voltage of the battery 2 is supplied to the motor M via the diode 7, and the motor M rotates. At this time, transistor 8
A voltage obtained by subtracting the voltage across the variable resistor 5 from the forward voltage drop of the diode 7 is applied between the emitter and the base of the diode 7, and if the variable resistor 5 is properly adjusted, a reverse bias is applied. As a result, transistor 8 enters the cut-off state.

Next, when the switch 3 is turned off, a back electromotive force is generated in the motor M due to rotation due to the inertia of the motor M.

Due to this back electromotive force, the base current of the transistor 8 flows through the path of the terminal TI- of the motor M, the emitter of the transistor 8, the base, and the resistor 6, and the transistor 8
turns on.

As a result, a short circuit is formed between both terminals '1' and T2 of the motor M, and the current due to the counter electromotive force flows through the short circuit, and the motor M is braked. In this case, the diode 7 acts as a current blocker.The current flowing from the terminal Tl of the motor M to the resistor 5 is blocked by the diode 7.

In this manner, in the above embodiment, the transistor 8 automatically switches depending on whether the switch 3 is turned on or off, mainly due to the action of the diode 7. As a result, it becomes possible to install the braking circuit 4 near the motor M, and by installing it in this way, the influence of noise caused by the braking flow of the motor M can be extremely reduced. Further, according to the above embodiment, the second switch 3
There is no need to use a device that connects both No and NC contacts like the switch 1 shown in the figure, so there is an advantage that the structure of the switch 3 is simplified. Further, in the above embodiment, since the transistor 8 is used, the life span is longer than that of a mechanical contact.

Note that a resistor may be inserted in series with the collector of the transistor 8. In this case, the braking characteristics of the motor M can be changed depending on the low pressure value. Furthermore, a field effect transistor may be used as the transistor 8.

"Effects of the Invention" As explained above, the braking circuit according to the present invention includes a switching element connected directly or through a resistor between two power application terminals of a DC motor, and a switching element connected between two power supply terminals of a DC motor when the switching means is in a closed state. Since it has a switch element control circuit that turns off the switch element and turns on the switch element when the opening/closing means is in the open state, it is possible to install the switch element very close to the DC motor. , the influence of noise on other electronic components can be minimized. Further, the braking circuit according to the present invention has the advantage that it can be easily added to a conventional circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG.
The figure is a circuit diagram showing the configuration of a conventional motor drive circuit. 4... Braking circuit, 8... Transistor (switch element), 9... Switch element control circuit. Figure 1 Figure 2

Claims (1)

[Claims] In a braking circuit for a DC motor driven by a DC power supply supplied via an opening/closing means, two of the DC motors are
a switch element connected directly or through a resistor between two power application terminals, and the switch element is turned off when the switching means is in a closed state, and the switching element is turned on when the switching means is in an open state. A DC motor braking circuit comprising a switch element control circuit.