JPH0145274Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a safety device for brushless motors used in record players, tape recorders, etc. More specifically, the present invention relates to a safety device that aims to prevent damage to the motor and drive circuit due to abnormal current when the rotor, which constitutes a part of the motor, is driven while being removed. FIG. 1 shows a basic drive circuit of a conventional brushless motor to which the safety device of the present invention is applied. In the figure, 1 is a drive controller, 2
A and 2b are two-phase drive windings, 3a and 3b are two-phase rotor position detection elements, and 4 is a rotor. The controller 1 detects the position of the rotor 4 using detection elements 3a and 3b, and drives the rotor 4 by passing necessary current through the windings 2a and 2b. By the way, if the power supply Vcc is applied while the rotor 4 is removed for some reason, the controller 1 will not be able to obtain proper signals from the detection elements 3a and 3b, and an abnormal current will be generated in the windings 2a and 2b. They may flow and burn out.
The present invention aims to provide a safety device that prevents the above-mentioned accidents from occurring.

The present invention includes a two-phase winding 2a that drives the rotor 4,
2b, two-phase rotor position detection elements 3a, 3b that detect the position of the rotor 4, and the detection elements 3a,
In the drive circuit for the brushless motor shown in FIG. 1, which includes a controller 1 that controls the current flowing through the two-phase windings 2a and 2b by the output of the two-phase rotor position detecting elements 3a, A pair of window comparators are provided to detect whether or not the output of the window comparator 3b is within a specified range, and when the outputs of the two window comparators are both within the specified range, power is supplied to the drive circuit. A safety device for a brushless motor is provided, which is characterized by shutting off the motor. In FIG. 2, 5 and 6 are window comparators whose outputs become "H" only when the outputs of 3a and 3b are within a specified range. The outputs of the window comparators 5 and 6 become inputs to an AND gate 7, and the output of the AND gate 7 is connected to the base of a control transistor 8. A power transistor 9 controls the supply of power to this drive circuit, and is controlled by the control transistor 8. FIG. 3 is a time chart showing the relationship between the outputs of the position detection elements 3a and 3b and the outputs of the window comparators 5 and 6, which change as the rotor 4 rotates, when the rotor 4 is normally installed. In other words, when the rotor is properly installed, the outputs of the two position detection elements are simultaneously output to the third position detection element.
It does not fall within the window level shown by the two dashed lines in the figure, and as a result, at least one of the outputs of the two window comparators is "L". Therefore, the output of AND gate 7 is always “L”
, transistor 8 is off, transistor 9
is on and power is supplied to the drive circuit.
If the rotor is removed, the outputs of the two position sensing elements will both fall within the above window level. As a result, the outputs of the two window comparators both become "H", the output of the AND gate 7 becomes "H", transistor 8 is turned on, transistor 9 is turned off, and the power supply to the drive circuit is cut off. Ru.

As described above, the safety device of the present invention has an excellent effect of protecting the controller and windings when the rotor of a brushless motor is removed.

[Brief explanation of the drawing]

FIG. 1: A drive circuit for a conventional brushless motor, FIG. 2: A drive circuit for a brushless motor according to the present invention, and FIG. 3: A diagram showing the relationship between the output of a position detection element and the output of a window comparator during normal operation. Symbol, 1...controller, 2a, 2b...two-phase winding, 3a, 3b...two-phase rotor position detection element,
4...Rotor, 5, 6...Window comparator, 7...AND gate, 8...Control transistor, 9...Power transistor.

Claims (1)

[Scope of utility model registration request] A two-phase winding that drives a rotor, a two-phase position detection element that detects the position of the rotor, and a controller that controls current flowing through the two-phase winding based on the output of the position detection element. In the brushless motor drive circuit, a pair of window comparators are provided to detect whether the outputs of the two-phase rotor position detection elements are within a specified range, and the outputs of the two window comparators are both A safety device for a brushless motor, characterized in that the supply of power to the drive circuit is cut off when the range is within the specified range.