JPH0449888A - Rotating pulse generation circuit of brushless motor - Google Patents

Abstract

PURPOSE:To obtain a stable pulse with a simple structure by making a differential amplification circuit using a current mirror circuit of an unbalanced current ratio as an active load instead of a resistor and unbalancing the duty ratio of an output waveform. CONSTITUTION:A position signal waveform (d) appearing on the collector of a transistor 12 is clipped with the VBE of a transistor 14. The current ratio of a current mirror is unbalanced by a resistor 13, therefore, the duty ratio of an output waveform is also unbalanced. A position signal waveform (e) appearing on the collector of a transistor 19 is clipped with the VBE of a transistor 20. The phases of the two waveforms are shifted inversely. The transistors 14 and 20 form a sort of NOR circuit and a waveform transmitted from their common collector is as shown by (f). Two pulses are thus generated every turn of the electrical angle.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotation pulse generation circuit for a brushless motor.

Conventional technology In recent years, small DC motors have been used not only in the acoustic field, but also in information and
Its excellent controllability has also been recognized in the industrial field, and its applications are rapidly expanding. Among these, brushless motors have no contact parts such as brushes and commutators, and have the advantage of long life, so their use as industrial motors where reliability is particularly important is expanding. Under these circumstances, the drive method of small axial fans has been switched from alternating current to direct current in recent years, and the number of direct current axial fans using brushless motors is increasing.

As the packaging density of industrial equipment such as computer-related equipment increases, direct current axial fans become necessary for cooling the equipment, and their reliability is also required to be high. In other words, if the motor stops for some reason, it not only prevents the motor coil from burning out, but also issues an alarm to the device itself to prevent accidents.
It has become necessary to automatically return to normal rotation when the cause is removed.

In FIG. 4, a magnetic detection circuit 11 a position signal amplification circuit 2
．． Output circuit 3. The coil 4 constitutes a fan drive motor. In this case, if the motor stops due to external factors or is operated at low speed under overload, the coil 4 will be burnt out due to excessive current and the motor will no longer function. In order to eliminate these problems, the following circuit configuration is used to cut off the output circuit 3 and prevent excessive current from flowing. That is, 5' indicates transistors 9 and 10 that constitute a differential amplifier whose load is the resistor 41, and transistor 16 which constitutes a differential amplifier whose active loads are transistors 18 and 19 that constitute a current mirror circuit. and 17, and transistors 14 and 20 that share a collector that receives signals from the load 41 and the transistor 19.
A rotation pulse circuit consisting of the above-mentioned common collector generates a pulse output in synchronization with the rotational position of the rotor.

Reference numeral 6 indicates a flip circuit which receives signals from the inversion detection transistor 26 and the inverter 30, and connects the capacitor 23 that stores electric charge to the constant current source 24 to put it in a charged state, or connects it to a constant current source 25 to put it in a discharged state. It is a flop circuit. 7 is a lock detection circuit composed of resistors 27 and 28 that determine hysteresis, a comparator 29, and the above-mentioned inverter 30, and is used for lock protection when the rotor is locked and the potential of the above-mentioned capacitor 23 rises to point A in Fig. 3. driving the transistor 31 to cut off the output circuit 3;
When the voltage drops to 0 point, an output is made to energize the output circuit 3. During normal operation, the discharge transistor 22 is connected to the capacitor 2 by the pulse output from the rotating pulse circuit 5'.
Discharge the charge of 3. 8, 15 and 21 are constant current sources.

The situation at this time will be explained in more detail using FIG.

This figure shows the charging and discharging states of the capacitor 23. During normal operation, a rotating pulse signal is periodically output at intervals of T1, so the potential of the capacitor 23 reaches the potential vopp that cuts off the output circuit 3. is not reached. Therefore, the motor continues to rotate without stopping. On the other hand, if the motor is stopped due to an external factor, the potential of the capacitor 23 continues to rise and reaches point A. When the point A is reached, the lock detection circuit 7 operates and cuts off the output circuit 3 via the lock protection transistor 31. The potential further increases to point B, that is, V H” V ref l +V
When BE is reached, the reversal detection transistor 26 operates to switch the contact of the flip-flop circuit 6 to the constant current R25fuq, and the capacitor 23 is placed in a discharged state. Therefore, the potential continues to fall and reaches the zero point.

Then, the lock detection circuit 7 operates to energize the output circuit 3 via the clock protection transistor 31 and simultaneously switch the contact of the flip-flop circuit 6 to the constant current source 24 side. The potential of the capacitor 23 continues to rise again, and when it reaches point D, the same operation as at point A occurs. During this time T:1. The motor repeats 0FF10N at intervals of T4 until the external factor is removed. T4
When the external factor is removed in the interval , the motor is energized and generates rotation pulses. This pulse causes the discharging transistor 22 to operate, and the capacitor 23 is discharged, returning to a steady state.

Problems to be Solved by the Invention FIGS. 2(a) to 2(c) show the operation of the rotation pulse circuit 5' of FIG. 4. (a) shows a position signal waveform generated at both ends of the resistor 41, which is clipped by the VBH of the transistor 14. (b) is the above transistor 1
The position signal waveform appearing at the collector of transistor 9 is clipped by VBH of the transistor 20. Both are 180° out of phase with each other. (C) is a waveform output from the common collector of a type of NOR circuit configured by the transistors 14 and 20. In this way, two pulses are generated every time it rotates in electrical angle. However, it is susceptible to the influence of temperature, and for example, the dotted line shows the waveform when the temperature is low; in this case, the above transistor 1
The VBE of 4 and 20 rises due to low temperature, and as shown in C), changes to become larger during the pulse. If the conditions are extremely bad, the two pulses will stick together, or conversely, if the temperature is high, no pulses will be generated. To address these problems, the present invention aims to obtain stable pulses with a simple configuration.

Means for Solving the Problems The present invention configures a differential amplification circuit using a current mirror circuit with an unbalanced current ratio as an active load in place of the resistor 41, and makes the duty ratio of the output waveform unbalanced. It is.

Operation With this configuration, both become active loads, for example, the VBE of the transistors 14 and 20
The pulse width output from the common collector is not affected by variations in the common collector.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows the circuit configuration of the magnetic detection circuit 12.
Position signal amplification circuit 2. Output circuit 3. The coil 4 constitutes a fan drive motor. Reference numeral 5 designates a rotating pulse circuit that includes a resistor 13, transistors 9 and 10 that form a differential amplifier whose active loads are transistors 11 and 12 that form a current mirror circuit, and transistors 18 and 19 that form a current mirror circuit. This is a rotary pulse circuit consisting of transistors 16 and 17 forming a differential amplifier as an active load, and transistors 14 and 20 which receive output signals from the transistors 12 and 19 and share a collector. A pulse output is generated from the common collector in synchronization with the rotational position of the common collector.

Hereinafter, the structure and operation of the flip-flop circuit 6 and the lock detection circuit 7 will be omitted as they are the same as in the conventional example.

FIGS. 2(d) to 2(f) show the operation of the rotation pulse circuit 5. FIG. (cl) is the position signal waveform appearing at the collector of the transistor 12, and is the VB of the transistor 14.
Clipped by H. However, since the current ratio of the current mirror is set to be unbalanced by the resistor 13, the duty ratio of the output waveform is also unbalanced. (e) is a position signal waveform appearing at the collector of the transistor 19, which is clipped by the VBH of the transistor 20. Both are inversely out of phase with each other.

(f) is a kind of NOR with the above transistors 14 and 20.
This is the waveform output from the common collector of the circuit. In this way, two pulses are generated every time it rotates in electrical angle.

According to this method, even if the VBE of the transistors 14 and 20 changes due to a change in temperature, the pulse width of the output waveform does not change.

Effects of the Invention As detailed above, according to the present invention, it is possible to obtain stable rotational pulses against temperature fluctuations with a simple circuit configuration, and the subsequent circuit processing is facilitated, reducing the number of parts, etc. It's large.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of an embodiment according to the present invention, FIGS. 2 and 3 are operation explanatory diagrams, and FIG. 4 is a circuit configuration diagram of a conventional example. 1... Magnetic detection circuit, 2... Position signal amplification circuit, 3... Output circuit, 4... Coil, 5... Rotating pulse circuit, 6...
Flip-flop circuit, 7... Lock detection circuit, 31... Lock protection transistor. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (1)

[Claims] A constant current source, a magnetic detection element that detects the rotational position of the rotor, a position signal amplification circuit that amplifies the output of the magnetic detection element, two sets of differential amplification circuits each having an active load, and an AND ( A rotation pulse generation circuit for a brushless motor, comprising a current mirror circuit having a different current ratio on one of the active loads.