JPS6339485A - Position sensing circuit for dc brushless motor - Google Patents

Abstract

PURPOSE:To prevent the direct intrusion of line noises to a control circuit, and to obviate leakage currents through the control circuit by transmitting a position sensing signal by using a photo-coupler, etc. CONSTITUTION:A higher harmonic component is removed by filters 1a-1c in a signal waveform acquired by synthesizing a pulse-width modulated voltage waveform given to a winding and winding induced voltage, and an approximately sine wave is outputted. Outputs from the filters 1a-1c and potential at a vertual neutral point are compared by comparators 2a-2c, and outputs from the comparators are transmitted over photo-couplers 10a-10c. Outputs from the photo-couplers 10a-10c are inputted to a control circuit 3 as position sensing signals, and a proper conduction mode is selected.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention detects the position of a DCC brushless morph permanent magnet rotor by using a back electromotive force induced in an armature winding ((l position). This relates to the detection circuit.

(Prior art) As an example of a conventional device detection circuit of this type, the second
The figure shows a block diagram of the 11'/position detection circuit configuration of a DC brushless camera disclosed in Japanese Unexamined Patent Publication No. 52-A-0415p3.

(Configuration) U, V, and W are each of the three phases, la, lb
, lc are each low-pass filter composed of components such as a resistor and a capacitor (both not shown). 2a, 2b, 2
c is each comparator that compares the output of the bowl filter with the virtual middle rr point constant potential created by combining each filter.

The outputs of these comparators are manually input to the control circuit 3. FIG. 3 shows each filter la.

This is an example of the configuration of lb and lc, 4 and 5 are resistors, and 6 is a capacitor.

(Operation) Next, the operation will be explained. Figure 4 (a), (b)
.

(c) shows the signal output waveform timing charts of the waste filters la, lb, and lc and the waste comparators 2a, 2b, and 2c for one phase, which are not shown in FIGS. 2 and 3, respectively. This is what is shown. Figure (a) shows the waveform of the filter human input signal, in which the voltage applied to line A from the outside is synthesized by the line induced voltage and switching elements such as power transistors (not shown).

The voltage applied to the winding from the outside is pulse width modulated in order to vary the effective voltage. Therefore, (1) Figure A1: The υ waveform contains high-order harmonic components.

(1)) The figure shows the irises waveform after passing through the filter. The harmonic components have been removed, and the fundamental sine wave has been obtained at approximately 90°.
〃is falling. (C) is an output signal obtained by comparing the waveform in (b) with the virtual neutral point potential (equal to the ground level in (b)) by each of the comparators 2a, 2b, and 2c. These outputs are used as position signals, and the control circuit 3 (second
(Figure) selects the energization mode suitable for the position signal, controls switching elements such as power transistors, and energizes the main body of the DC brushless motor (none of which is shown), which has a synchronous motor structure and has a permanent magnet rotor. By doing so, the motor was configured to continue rotating.

(Problem to be solved by the invention) The conventional position detection circuit of a DC brushless motor is as follows.
Since it is configured as follows, the armature winding terminal and the control circuit are electrically connected. The armature winding is
It is a strong electric system that supplies power for driving the motor, while the control circuit is a weak electric electronic circuit using a microcomputer, etc., so if these are electrically connected, noise in the strong electric system will be generated. It invades the weak electric system and causes malfunction (cl) Ij:C. In addition, if this divine control circuit power supply system is used to control electrical circuits that may come into contact with the human body, such as switches in consumer equipment, the leakage from the strong electrical system may cause a shock to the human body. ′j− danger+
[There was].

This invention solves the problems of the conventional example as described in 1-11.
In order to achieve this, the winding end r and the control circuit are electrically separated, and in terms of signal transmission, the provision of a position detection circuit that enables the same operation as in the past [1]
It has been the target.

(One step to solve the problem) Therefore, in the position detection circuit according to the present invention, a low-pass filter that removes harmonic components from the wire end voltage, and a virtual neutral pyroelectric (By providing a comparator that compares I, and a stage that transmits the signal by electrically insulating the output of the comparator, such as a poto coupler, the objective L1 is achieved.) be.

[Function] In the position detection circuit for a DC brushless motor of the present invention having the configuration as described in 1 below, the winding terminals and the control circuit are electrically connected to each other by a hair stage such as a photocoupler that is electrically insulated and transmits signals. This prevents line noise from directly entering the control circuit and prevents leakage current through the control circuit.

(Embodiments of the Invention) The present invention will be described below based on embodiments. Fig. 1 shows a configuration block diagram of an embodiment of a position detection circuit for a DC brushless motor according to the invention. Example 2
Components that are the same or equivalent to those in the figures are indicated by the same reference numerals.

(Configuration) In 1, Ia, lb, and lc are each low-pass filter, 2a, 2b, and 2c are each resistor for current limiting, and 12a
, 12b, and 12c are pull-up resistors, and 3 is a control circuit. Each of the low-pass filters la, 1b, and lc has the same configuration as in the conventional example shown in FIG. 2.3.

(Operation) Next, the operation of this embodiment in the configuration described below will be explained. The 111 waveform and operation from the manual input of each filter la, lb and IC to the output of bowl comparators 2a, 2b and 2c are exactly the same as those shown in FIG. 4 of the conventional example. That is, the signal waveform a, which is a combination of the pulse width modulated voltage waveform applied to the winding and the winding-induced 1f-, has its harmonic components removed by the filters la, lb, and Ic, and is A string wave is obtained. The potential of the virtual neutral point of this signal waveform is determined by the comparators 2a and 2b.

By comparing 2C, an output signal waveform C can be obtained. When the comparator output is Hi (high) level, each photocoupler 10a, 10b.

The LED (light-emitting lamp) at 10c does not light up, and the output transistor is off. Therefore, the pull-up resistors 12a, 12b, and 12c cause the outputs of the respective photocouplers 10a, Job, and 10c to become Hi level.

Each comparator 2a.

When the outputs of 2b and 2c are at Lo (low) level, current flows through the LEDs of each photocoupler 10a, 10b, 10c and the valley current limiting resistors 11a, llb, and lie.
ED lights up. Therefore, the phototransistor on the output side is turned on, and the output of each photocoupler 10a, 10b, 10c becomes Lo level. That is, each comparator 2a
, 2b.

Since the same output as the output of 2C is obtained, the photocoupler output is used as a position detection signal to be manually inputted to the control circuit 3. The control circuit 3 selects an appropriate energizing motor based on this position signal and controls a switching element such as a power transistor (not shown) to drive a DC brushless motor (with a synchronous motor structure) that drives a permanent magnet rotor. The motor is rotated by energizing the motor (both not shown).

〔Effect of the invention〕

As described below-4-, according to the present invention, the position detection signal is transmitted using a photocoupler, etc.
-The winding end r- and the control circuit can be electrically separated 1- to prevent noise from entering the signal line and leakage current from the strong electrical system, which can cause shock to the human body! j, the 11 ability to get angry is gone.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the configuration of a position detection circuit of a DC brushless motor according to an embodiment of the present invention, FIG. 2 is a block diagram of a position detection circuit of a conventional DC brushless motor, and FIG. FIG. 4, which is a configuration diagram of each low-pass filter in the example or the first embodiment, is a timing chart of each signal waveform of the position detection circuit in the conventional example or the above embodiment.

Claims (2)

[Claims] (1) A synchronous motor having a permanent magnet rotor and a three-phase armature winding, a position detection circuit that generates a position signal of the rotor from a voltage induced at the end of the winding, and a position detection circuit that generates a position signal of the rotor from a voltage induced at the end of the winding. A control circuit that reads and generates a command signal to switch the energization mode to the armature winding, and energization switching means using a switching element that applies voltage to a predetermined armature winding in accordance with the energization mode switching signal. In the DC brushless motor, the position detection circuit includes a low-pass filter that removes harmonic components from the winding end voltage, and a comparator that compares the output of the filter with a virtual neutral point potential. A position detection circuit for a DC brushless motor, comprising means for electrically insulating the comparator output and transmitting a signal. (2) The position detection circuit for a DC brushless motor according to claim 1, wherein the comparator output is electrically insulated.