JPH0223091A - Brushless dc motor driving circuit - Google Patents

Abstract

PURPOSE:To reduce in size a brushless DC motor inexpensively by comparing a supply signal to a winding with the power source voltage of a power circuit, varying a control signal level by the difference, and forming a feedback loop. CONSTITUTION:A brushless DC motor driving circuit has a rotating angle detecting means 1 for a rotor, a driving waveform generator 2 for forming a supply signal of a stator winding on the basis of it, and a power circuit 4, and drives a motor. The output signal of the generator 2 is supplied to the circuit 4 through a gain varying circuit 3 for varying its gain, a differential voltage detector 5 and a control signal limiter 6 are provided, and the level of a control signal to be supplied to the circuit 3 is limited by the limiter 6. As a result, the excess input of the control signal is eliminated, and the saturation of the circuit 4 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a brushless DC motor drive circuit, and more particularly to a brushless DC motor drive circuit that prevents waveform distortion of signals supplied to the windings of a brushless DC motor.

BACKGROUND ART A brushless DC motor generally consists of a rotor made of permanent magnets and a stator having multiple windings, and the drive circuit that drives this brushless DC motor detects the rotation angle of the rotor with respect to the stator. a rotation angle detection circuit that generates a drive signal to drive each winding from the output signal of the rotation angle detection circuit, and a drive signal generation circuit that generates a drive signal to drive each winding from the output signal of the rotation angle detection circuit, and It consisted of a variable gain circuit that varied the serrations, and a power circuit that received the output signal from the variable gain circuit, amplified the power, and supplied it to the motor windings.

Furthermore, in conventional drive circuits, as a technique to prevent saturation of the power circuit due to excessive control signal input, the level of the III control signal is normally operated only within a range in which the power circuit is not saturated. For example, for a power supply voltage of 12V, the maximum voltage applied to the winding is limited to about 7V in normal use.

Problems to be Solved by the Invention However, when trying to control a motor by applying speed servo or phase υ-vo without limiting the control signal level with a conventional drive circuit, the reference speed or the The motor rotational speed and rotational phase become slightly slower than the reference phase, increasing the speed error and phase error, resulting in an excessive input of control signals, the gain of the variable gain circuit reaches its maximum, and the input signal of the power circuit becomes excessive. Therefore, the maximum possible power is applied to the motor windings at this time.

For this reason, the voltage applied to the motor windings increases to the voltage limited by the voltage supplied to the power circuit, the so-called power circuit becomes saturated, and the drive signal waveform becomes distorted and rectangular. As a result, abnormally large torque irregularities occur in the motor's drive torque, resulting in large mechanical vibrations and noise.Also, the motor winding has a large self-inductance, and the motor winding has a rectangular wave pattern. Since a voltage waveform is applied, a spike-like high voltage is generated at the rise and fall of this waveform, resulting in an increase in electrical noise.

In addition, even when limiting the control signal level, conventional drive circuits limit the input level of the control signal itself within a certain range to prevent saturation of the power circuit. It is necessary to consider the gain error up to the output of the power circuit, the error in the power circuit's non-saturation range (output dynamic range), and the humidity changes of these errors. 1. It is necessary to limit the control range to a narrower range than the range that does not saturate, and the control range is limited.1. Additionally, in some cases, a current drive method is used in which a current is supplied to the winding according to the control signal in order to keep the generated torque constant. In this case, by limiting the input control signal, the maximum rotational speed (winding When the winding current is limited to a level that does not saturate the power circuit (the back electromotive force voltage generated in the wire is at its maximum), the current cannot flow even when the motor is started, resulting in a significant drop in starting torque. There was a problem.

The present invention has been made in view of the above points, and an object of the present invention is to provide a drive circuit for a brushless DC motor that can fully utilize the capability of the motor.

Means for Solving the Problems FIG. 1 shows a block diagram of the principle of the present invention. The present invention includes a rotation angle detection means 1 for detecting the rotation angle of a rotor of a brushless DC motor with respect to a stator, and a drive for generating a signal to be supplied to the windings of the stator according to a detection signal of the rotation angle detection means 1. A variable gain circuit 3 receives the output signals of the waveform generating circuit 2 and the drive waveform generating circuit 2 and whose gain is varied according to an external control signal, and the variable gain circuit 3 amplifies the output signal of the variable gain circuit 3, In a brushless DC motor drive circuit comprising a power circuit 4 that supplies windings, a difference between an output signal voltage of the power circuit 4 and a power supply voltage supplied to the power circuit is detected, and a voltage difference is detected according to the voltage difference. a differential voltage detection circuit 5 that outputs a signal at a level equal to that of the differential voltage detection circuit 5; and the output signal of the differential voltage detection circuit 5 and the control signal are supplied, and the level of the control signal is limited according to the output signal level of the differential voltage detection circuit 5. and a control signal limiting circuit 6 for supplying the control signal to the variable gain circuit.

The operating rotation angle detection means 1 detects the rotation angle of the rotor with respect to the fixed r, and in accordance with this rotation angle, the drive waveform generation circuit 2 generates a waveform signal to be supplied to the windings installed on the stator. Occur.

The output signal of the drive waveform generating circuit 2 is supplied to a power circuit 4 via a variable gain circuit 3 whose gain is variable, amplified by the power circuit 4, and supplied to 'Dt'A. At this time, the difference between the output signal voltage of the power circuit 4 and the power supply voltage supplied to the power circuit 4 is detected by the differential voltage detection circuit 5, and the control signal limiting circuit 6 controls the gain variable circuit 3 according to the difference. The level of the control signal supplied to the device is limited. In other words, feedback is applied to the control signal according to the winding voltage.

Therefore, an excessive amount of the control signal is not input to the variable gain circuit 3, and saturation of the power circuit 4 can be prevented.

Example FIG. 2 shows a circuit diagram of a first embodiment of the invention.

In the figure, 7 is a rotation angle detection means, 8 is a drive waveform generation circuit,
Reference numeral 9 indicates a power circuit, 1o indicates a differential voltage detection circuit, and 11 indicates a control signal limiting circuit.

This embodiment is an application of the present invention to a type of brushless DC motor drive circuit that uses a general three-phase full-wave (push-pull) current drive type Hall element as a rotation angle detection means.

The rotation angle detection means 7 includes three Hall elements 1'G1 to HG.
The output signals of the Hall elements HG+ to HG3 of the rotation angle detection means 7 are shown in FIGS. 3A to 3C.

A drive waveform is generated by multiplying and sieving by a drive waveform generation circuit 8 which also serves as the drive waveform generation circuit 2 and the variable gain circuit 3 in the block diagram of FIG. Supply to 9. This multiplication waveform signal is transmitted to the transistor 023 of the power circuit 9.
~Q28, the current mirror circuits each include transistors 029~04G and resistors R+s~R3Q.

The output signal of this current mirror circuit is connected to the transistor Qs
s to Qss and a resistor VER<+=842, and supply it to the winding L1 as a waveform shown in FIG.
The waveform shown in FIG. 4(B) is supplied to the winding L2, and the waveform shown in FIG. Drive.

The differential voltage detection circuit 10 is connected to winding 1 of windings L+, L2, and L3.
+ peak of 1 voltage is connected to diode D+, D2.

The voltages rectified and detected by D3 and the voltages rectified and detected by the diodes D4 to D6 of the power supply voltage VMM of the power circuit 9 are connected to the transistors Qes + Qss and the resistor R.
=IJ-Rss, and the difference is the transistor Qy
o , Qy + and resistor R49.

The control signal limiting circuit 11 transmits the detection signal of the differential voltage detection circuit 10 to the transistors Qy 2 , Qy 3 and the resistor R-
The level of the control signal input from the terminal 12 is detected by the transistors Qe2 to Qsy and the resistors R45 to R45.
The control signal is controlled by a control signal limiting circuit 11 consisting of 47.

For example 1! When the difference between the source voltage VM and the winding voltage becomes smaller, that is, when the power circuit 9 approaches saturation, the voltage at the contact point 13 between the differential voltage detection circuit 10 and the control signal limiting circuit 11 becomes large. Resistor R4 of control signal limiting circuit 11
8 becomes larger. Therefore, a constant 1! which is made up of transistors Q2+ and QZ2 and resistors R+y and R+g that drive the drive waveform generation circuit 8 is formed. The control current of the current source is limited.

Therefore, the transistors QCs to Q? connect the drive waveform generation circuit 8 and the power circuit 9. + and transistor 023~
The current flowing through Q21+ is limited, thus preventing the power circuit 9 from becoming saturated.

In FIG. 4, the broken line indicates the waveform of the winding voltage when this embodiment is not used. As shown in FIG. 4, when the maximum voltage is applied without feedback as in this embodiment, the power circuit 9 becomes saturated, resulting in a rectangular waveform, and the motor rotation becomes awkward.

Next, a second embodiment will be explained with reference to FIG. Third
The circuit shown in the figure shows an example to which the present invention is applied in a so-called three-phase full-wave voltage driving force type. The rotation angle detection means 12 consists of three Hall elements HG4 to HG6 and resistors Rss and Rsa, and is a small Hall element! IG4 to HGs are connected in parallel to the power supply.

The output of the Hall element HG<~HGs is the transistor Q74
~Q83. Drive waveform generation circuit 13T consisting of resistors Rsa to R7° and diode D7: Hall elements HG4 to H
Comparing the voltage across Gs, transistors Q84 to Q9
9. Q1o7~Q++o and resistance Ry+, R
The variable gain circuit 14 consisting of y y * Ry s connects transistors Q+ + + to Q+ 48 and resistors Ry.
g ~ Rsg and transistor Q149 ~ Q + s t
5 + Vary the level of the signal supplied to the power circuit 15 consisting of resistors Rss to R98. The power circuit 15 amplifies the signal from the variable gain circuit 14 and supplies it to the windings b to 1-3.

Further, the signals supplied to the windings L+~[3 are supplied to the voltage 11i! It is compared with voltage VMM and the difference voltage is detected. The differential voltage detected by the differential voltage detection circuit 16 causes the transistor Q+ e s to be activated.

016610100-QI06 and resistors R72 to R76
The υ1111 signal limiting circuit 17 limits the level of the control signal and supplies it to the variable gain circuit 14. Therefore, the variable gain circuit 14 limits the level of the signal supplied to the power circuit 15.

Therefore, the power circuit 15 will never reach a saturated state.

In this embodiment, for example, if a signal with a waveform as shown in FIG. 6 (Δ) is generated at Ic+, and a signal with a waveform as shown in FIG. 6 (B) is generated at IC2, This results in a signal with a waveform as shown in Figure (C). Therefore, the power circuit 15 is supplied with a voltage having a waveform as shown in FIG. 6(D).

For example, if the output signal waveforms of the Hall elements HG4 to 11G6 are as shown in FIGS. 7(A) to (B), the winding L+-La has the waveforms shown in FIGS. A smooth waveform signal shown in is applied. 8th
In the figure, the broken line indicates that no feedback is applied, and the waveform is not smooth, so driving with a signal with such a waveform may cause torque unevenness, etc.

Effects of the Invention As described above, the present invention provides a feedback loop that compares the signal supplied to the winding with the power supply voltage of the power circuit and varies the control signal level based on the difference, thereby controlling the signal supplied to the winding. By configuring this, the signal level supplied to the windings will not be excessive due to excessive input of the control signal, and the power circuit will not be saturated, so distortion of the signal supplied to the windings can be prevented, and Since torque unevenness during overload can be reduced, power can be efficiently supplied to the windings with less vibration, noise, and electrical noise.Furthermore, since it can be configured by simply adding a relatively simple circuit to a conventional circuit, I
It has features such as being easily convertible to C, being inexpensive, and being able to be miniaturized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a circuit diagram of a first embodiment of the present invention, FIGS. 3 and 4 are waveform diagrams of main parts of the first embodiment of the present invention, and FIG. FIG. 5 is a circuit diagram of a second embodiment of the present invention, and FIGS. 6, 7, and 8 are waveform diagrams of essential parts of the second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Rotation angle detection means, 2... Drive waveform generation circuit, 3... Gain variable circuit, 4... Power circuit, 5...
... Differential voltage detection circuit, 6... Control signal limiting circuit. Kuzuko diagram

Claims (1)

[Scope of Claims] Rotation angle detection means for detecting a rotation angle of a rotor of a brushless DC motor with respect to a stator, and generating a signal to be supplied to the windings of the stator according to a detection signal of the rotation angle detection means. a drive waveform generation circuit that amplifies the output signal of the variable gain circuit; In a brushless DC motor drive circuit comprising a power circuit that supplies windings, a difference between an output signal voltage of the power circuit and a power supply voltage supplied to the power circuit is detected, and a voltage is determined according to the voltage difference. a differential voltage detection circuit that outputs a level signal; an output signal of the differential voltage detection circuit and the control signal are supplied; and the level of the control signal is limited according to the output signal level of the differential voltage detection circuit; A brushless DC motor drive circuit comprising a control signal limiting circuit that supplies the variable gain circuit.