KR900007221Y1 - Safety circuit for brushless d.c. motor - Google Patents

Abstract

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Description

Safety circuit for brushless DC motor

1 is a safety circuit diagram according to a first embodiment of the present invention.

2 is a safety circuit diagram according to a second embodiment of the present invention.

3 is a conventional drive control circuit diagram for a brushless DC motor.

4 is an output timing diagram of a drive signal for a brushless DC motor.

* Explanation of symbols for main parts of the drawings

ANDl, AND2, AND3: 2-input AND gate

LC: 3-phase logic NOT: NOT gate

TR1, TR2, TR3, TR4. TR5: Transistor SC: Stator Coil

OR: 3 input OR gates D4, D5, D6: Diode

RD: Rotor

The present invention relates, for example, to a safety circuit for a brushless DC motor mounted on a fuel supply pump of an automobile. More specifically, the driving current of a brushless DC motor is simultaneously applied to two or more stator coils of a brushless DC motor. It relates to a safety circuit for stopping the rotation of a brushless DC motor when supplied.

3 shows a conventional drive control circuit of a three-phase brushless DC motor.

As shown, a 3-position sensor MP for sensing the magnetic pole position of the rotor RO magnetized by the permanent magnet is attached close to the outer circumference of the rotor RO at intervals of 120 °. The output signal from the sensor MP is input to the position detection circuit MPC.

The position detection circuit MPC converts the output signal from the position sensor MP into a logic " 1 " signal, for example, and outputs this logic signal to the three-phase logic circuit LC.

According to the magnetic pole position signal generated by the position detection circuit MPC, the three-phase logic circuit LC outputs the first phase output terminal θ ₁ and the second phase at the output timing of each phase as shown in FIG. The drive signal DS through the resistors R1, R2, and R3 to the transistors TR1, TR2, and TR3 from the terminal θ ₂ and the third phase output terminal θ ₃ , respectively. Outputs

The transistors TR1, TR2, and TR3 are turned on whenever the drive signal DS generated from the three-phase logic circuit LC is input to each base of the transistor so that the drive current of the rushless DC motor is increased. It is sequentially supplied to each of the three-phase stator coils SC from the power supply + B to rotate the rotor RD.

Diodes D1, D2, and D3 are connected in parallel to respective stator coils SC to absorb surges in the stator coils SC.

In the conventional drive control circuit for a brushless DC motor, when the three-phase logic circuit LC is affected by external noise or the like, the drive signal DS is very irregular regardless of the regular output timing shown in FIG. Sometimes it is printed. As a result, for example, the driving signal DS may be output simultaneously from the second phase output terminal θ ₂ and the first phase output terminal θ ₁ of the three-phase logic circuit LC.

In this case, the transistors TR1 and TR2 are turned on at the same time, and the driving current is simultaneously supplied to the first phase stator coil and the second phase stator coil.

As described above, when a plurality of stator coils are energized at the same time, the stator coils of the phases to which the original driving current should not be supplied act as a load to reduce the rotation speed of the rotor RO and consume excessive power.

Accordingly, an object of the present invention is to provide a safety circuit suitable for preventing the abnormal rotation of the brushless DC motor and preventing excessive power consumption.

According to the present invention, in a drive control circuit for controlling a switching device for generating a drive signal for a brushless DC motor at a predetermined output timing and for supplying a drive current to the stator coil of the brushless DC motor, the safety circuit generates a drive signal. A detection circuit for detection and an output circuit for generating a signal for turning off the switching device when the detection circuit simultaneously detects the drive signals when the drive signals are generated simultaneously in the drive control circuit.

In operation, when a drive signal is simultaneously output from the drive control circuit to the plurality of switching devices, the drive signal is simultaneously detected by the safety circuit to generate an abnormal signal.

This abnormal signal is used to turn off the switching device that energizes the driving current to each stator coil or to turn off the power supply circuit that supplies the driving power to each stator coil. Accordingly, the driving current energized to each stator coil. It acts to block.

The invention will next be better understood from the appended claims and the following detailed description with reference to the drawings.

Referring to FIG. 1, the safety circuit SFC1 is connected to a conventional composition control circuit for a three-phase brushless DC motor shown in FIG. More specifically, the first phase output terminal θ ₁ of the three-phase logic circuit LC is connected to one input terminal of each of the two input AND gates AND1 and AND2, and the second phase output terminal is connected. (θ ₂ ) is connected to the other input terminal of the two-input AND gate AND1 and AND2 and one input terminal of the two-input AND gate AND3.

The third phase output terminal θ ₃ is connected to the other input terminal of the two-input AND gate AND3 and the other input terminal of the two-input AND gate AND1.

The output terminals of the two input AND gates AND1, AND2 and AND3 are connected to the respective input terminals of the three input OR gate. The output terminal of the three-input OR gate OR is connected to the base of the NPN transistor TR4.

The emitter of the transistor TR4 is connected to the zero volt terminal of the power supply + B.

The cathodes of the three diodes D4, D5, and D6 are connected to the collector of the transistor TR4. The anodes of diodes D4, D5, and D6 are in contact with respective bases of transistors TR1, TR2, and TR3.

The drive signal DS is output from the first phase output terminal θ ₁ of the three-phase logic circuit LC to the base of the transistor TR1 through the resistor R1 at the output timing shown in FIG. When TR1 is turned on and a drive current is supplied from the power supply (+ B) to the first phase stator coil SC, external noise is inputted to the three-phase logic circuit LC and the three-phase logic circuit ( The operation of the circuit element of the LC) is influenced so that, for example, the driving signal DS is simultaneously output from the first phase output terminal and the second phase output terminal.

In this state, the transistors TR1 and TR2 are turned on at the same time, and a driving current is simultaneously supplied to the first and second phase stator coils.

In this case, since the first phase stator coil is properly supplied with the flow, but the second phase stator coil is not supplied with the original current, the second phase stator coil acts as a kind of load of the first phase stator coil and thus the rotor (RO). Decreases the rotation speed and output torque.

The safety circuit SFC1 is provided for dismantling the state.

When the driving signal DS is simultaneously output from the first phase output terminal θ ₁ and the second phase output terminal θ ₂ of the three-phase logic circuit LC, the logic is applied to the two input terminals of the two-input AND gate AND2. A "1" signal is applied, and in turn a logic "1" signal is output to the three input OR gate OR.

The three input OR gate OR then outputs a logic " 1 " signal.

As a result, transistor TR4 is turned on, and each base of transistors TR1, TR2, and TR3 passes through diodes D4, D5, D6, and TR4. Grounded. Therefore, all the transistors TR1, TR2, and TR3 are turned off to prevent the driving current from being supplied to the respective stator coils SC from the power supply + B.

When there is no influence of the external noise on the three-phase logic circuit LC, the drive current is sequentially supplied to each stator coil at a normal timing.

In the above embodiment, external noise affects the three-phase logic circuit LC, and a drive signal is output from the first and second phase output terminals θ ₁ and θ ₂ of the three-phase logic circuit LC. When output at the same time, the two-input AND gate AND2 generates a logic " 1. "

Similarly, when the second phase output terminal θ ₂ of the three-phase logic circuit LC is a normal drive signal output terminal and an abnormal drive signal is output from the three phase output terminal θ ₃ , the two-input AND gate AND3. Generates a logic "1". When the three-phase output terminal θ ₃ is a normal drive signal output terminal and an abnormal signal is output from the first phase output terminal θ ₁ , the two-input AND gate AND1 generates a logic “1”.

As a result, the transistors TR1, TR2, and TR3 are turned off in each of the above cases.

Next, another embodiment of the present invention will be described with reference to FIG.

In the second embodiment, the safety circuit SFC2 is provided in the same manner as the safety circuit SFC1 of the first embodiment. The output terminals θ ₁ , θ ₂ and θ _{3 of the} three-phase logic circuit LC are connected to the input terminals of the two input AND gates AND1, AND, and AND3, respectively.

The output terminal of the three-input OR gate OR is connected to the input terminal of the NOT gate NOT, and the output terminal of the NOT gate NOT is connected to the base of the NPN transistor TR5.

The power supply + B for supplying driving power to each stator coil is connected to the collector of the transistor TR5, while the center point NP of each stator coil SC is connected to the emitter of the transistor TR5.

In the safety circuit SFC2 as described above, external noise affects the three-phase logic circuit LC, and external terminals θ ₁ , θ ₂ , and θ _{3 of the} three-phase logic circuit LC. When a drive signal is simultaneously output from a plurality of output terminals of the at least one gate of the two-input AND gates AND1, AND, andAND3, a logic " 1 " The output signal from OR) becomes a "1" signal.

As a result, the NOT gate NOT outputs a logic " 0 " signal and is applied to the base of the transistor TR5.

As a result, the transistor TR5 is turned off and cuts off the driving power supplied from the power supply + B to the neutral point NP of the stator coil SC.

When the external noise is not affected by the three-phase logic circuit SC, the driving current is sequentially supplied to each stator coil at normal timing.

Although a suitable embodiment of the present invention has been described as described above, it can be implemented that various structural modifications and applications can be carried out without departing from the spirit of the present invention.

Claims (3)

Controlling the switching devices (TR1, TR2, TR3, TR5) to generate the drive signal (DS) for the brushless DC motor at a predetermined output timing, and to supply the drive current to the stator coil (SC) of the brushless DC motor In the driving control circuits MPC and LC, the safety circuit is a detection circuit AND1, AND2, AND3, OR for detecting the driving signal DS and the detection circuit when the driving signal is simultaneously generated from the driving control circuit. And an output circuit (TR4: NOT) for generating a signal for turning off the switching device when the drive signals are simultaneously detected. The method of claim 1, wherein the output circuit TR4 generates a signal for turning off the switching devices TR1, TR2, TR3 connected to the respective stator coils SC of the brushless DC motor. Safety circuit characterized in that. The safety circuit according to claim 1, wherein the output circuit NOT generates a signal for turning off one of the switching devices TR5 connected to the center point NP of the stator coil SC. Circuit.