JPS62123981A - Hall ic - Google Patents

Abstract

PURPOSE:To prevent the damage of a coil and a transistor by detecting the period of revolution from an output signal from a Hall element detecting the position of revolution of a body of revolution and interrupting or limiting motor driving currents when the number of revolution of a motor reaches the number of revolution set or less. CONSTITUTION:An output signal from a Hall element 4 detecting the position of revolution of a body of revolution is inputted to amplifying circuits 5, 6 while being inputted to a differential pulse generating circuit 8, thus generating trigger pulses. A flip-flop 11 is set by the trigger pulses. A charge and discharge circuit 9 repeats the charge and discharge of a capacitor 15 by the trigger pulses, and a period detector circuit 10 decides the time period of the charge and discharge. When a charge signal reaches a predetermined level, the period detecting circuit 10 transmits a reset signal over the flip-flop 11. When the flip-flop 11 is reset, output currents from the amplifiers 5, 6 are interrupted,and conduction to output transistors 12, 13 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Hall IC used as a rotor position detection means for a DC brushless motor, which is widely used as a drive source for industrial and video equipment, etc. It is.

BACKGROUND OF THE INVENTION In recent years, brushless single current motors have been used in various consumer and industrial equipment because they are brushless and have a long service life. 2. Description of the Related Art Hall ICs, in which a Hall element, which is a magnetically sensitive element, and an amplifier circuit are integrated are widely used because of their simplicity.

The conventional Hall IC described above will be explained below with reference to the drawings.
and a drive circuit for a DC brushless motor. FIG. 3 is a schematic diagram of a normal brushless motor, and FIG. 4 is its circuit diagram.

In FIGS. 3 and 4, the DC brushless motor is composed of a Hall IC 21, a permanent magnet (rotor) 22, and a stator coil 23, 24, and the magnetic flux magnetized to the rotor 22 is passed through the Hall IC 21. Detected, Hall IC21
The output signal of the Hall element 25 built in is sent to the amplifier circuit 26.
The signal is amplified to a required level by the signal, and the transistor 27 is turned on and off depending on its polarity. Now, Hall IC
When the output level of transistor 21 is, for example, a high potential (hereinafter referred to as H), transistor 27 is conductive, and therefore transistor 2
8 is ON (transistor 29 is OFF), current is applied to the stator coil 23, and the rotor 22 is rotated.On the other hand, the rotor 22 rotates, the polarity changes, and the Hall IC 2
When the output level of the transistor 1 becomes a low potential (hereinafter referred to as "A"), the transistor 27 becomes OF I' t:, and the base current is supplied to the output transistor 29 through the resistor 30 and the diode 31, 32, and the output transistor 29 It turns ON (transistor 28 is OFF), and current is passed through the stator coil 24 to continuously drive it to rotate. For such conventional motors, for example 1-National T
electrical report JV.

1.26. No. 5, pages 796-800.

Problems to be Solved by the Invention However, in the conventional motor as described above, when the motor is locked, a large current is supplied to the stator coil. Also, the heat generation and temperature rise of the output transistor becomes large, causing problems such as burning out of the coil and destruction of the transistor.

Means for Solving the Problems In view of the above-mentioned drawbacks of the conventional art, the present invention detects the rotation period of the motor in the Hall IC, and automatically turns off the motor drive current when the rotation speed of the motor becomes less than or equal to a set number of circuits. It is constructed by adding a circuit that performs a limiting function.

Effect: With the above-described configuration, the present invention utilizes the fact that the stator coil current is proportional to the motor rotation speed, detects the rotation period from the output signal of the Hall element, and detects when the motor rotation speed is less than or equal to the set rotation speed. When this occurs, the motor drive current is automatically cut off or limited to prevent motor coil burnout and output transistor destruction.

Embodiment Hereinafter, a Hall IC and its driving circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an internal circuit diagram of a Hall IC in an embodiment of the present invention. In FIG. 1, 1.2 is a stator coil,
12 and 13 are output transistors that supply current to the stator coil, and 3 is a Hall IC.

4 is a Hall element, 5 and 6 are amplifier circuits that output signals of opposite polarity, and 7 is a stabilizing power supply that stabilizes the voltage applied to the Hall IC. At the same time, one of them is manually inputted to the differential pulse generation circuit 8 to generate a pulse. Furthermore, the flip 70 knob 11 is set by this trigger pulse. 9 is a charging/discharging circuit that controls charging and discharging of the capacitor 14 in response to the trigger pulse; 10 is a period detector circuit that determines the time period of the charging and discharging; when the charging signal reaches a predetermined level, A reset signal is supplied to the flip-flop 11, and the flip-flop is reset to cut off the output current of the amplifier 5.6 and stop energizing the output transistor.

Regarding the Hall IC configured as above, the first
The operation will be explained using FIG.

First, the time chart in Figure 2 shows the waveforms of each part in Figure 1 in each state when the motor is started, when rotating at a constant speed, and when the motor is locked, where a is the Hall element output, b is the trigger pulse, C is the charge/discharge waveform of the charge/discharge circuit, d is the output waveform of the period detection circuit, and e is the output waveform of the flip-flop. When the motor is locked and the output level of the charging circuit reaches a predetermined level VO, a set signal is input to the flip-flop (hereinafter referred to as the output waveform d of the period detection circuit), which inverts the state of the output e of the flip-flop. The output current of the amplifier is cut off and the power supply to the output transistor is stopped.By the way, when the motor is started, a predetermined time delay determined by the resistor 14 and capacitor 15 occurs, and the potential level in the waveform of C does not reach Vo. Since the flip-flop is not reset, sufficient base current is supplied to the output transistor and the motor starts, so there is no problem.

Effects of the Invention As described above, according to the present invention, a Hall IC composed of a normal Hall element and an amplifier detects the rotation period of the motor, and when the rotation speed of the motor becomes less than the set rotation speed, the By adding a circuit that functions to limit the motor drive current, a simple configuration can prevent coil burnout, output transistor destruction, and permanent magnet demagnetization when the motor is locked, improving reliability. It has a huge effect. Further, according to the present invention, the starting current is not set even at the time of starting, so starting performance is good.

[Brief explanation of drawings]

Fig. 1 is an internal circuit diagram of a Hall IC according to an embodiment of the present invention, Fig. 2 is a time chart showing waveforms of each part in Fig. 1, Fig. 3 is a schematic diagram of a conventional brushless motor, and Fig. 4 is FIG. 2 is a drive circuit diagram of a conventional brushless motor. 1.2... Stator coil, 12.13...
...Output transistor, 3...Hall IC, 4
······Hall element. Name of agent: Patent attorney Toshiki Nakao and one other person. f: ILJ ℃ 0 Figure 3 Figure 4 ■,.

Claims (1)

[Claims] a Hall element as a position detection means for detecting the rotational position of a rotating body; an amplifier circuit for amplifying an output signal of the Hall element to drive an output transistor for switching the current-carrying phase of the stator winding; A Hall IC comprising a period measuring circuit that measures the time period of an output signal, and a reset circuit that stops energizing the output transistor when the period exceeds a predetermined period.