JPS5918872Y2 - Motor drive circuit protection device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a protection device for a motor drive circuit, and more specifically, detects an AC signal with a frequency proportional to the motor rotation speed, operates a monostable multi-circuit, and smooths the output. This device relates to a protection device in a motor drive circuit that drives a motor at a constant speed by comparing the DC voltage obtained by converting the DC voltage with a reference voltage and controlling the deviation to zero. Automatically suppresses sudden changes in motor speed when the motor starts or stops, thereby preventing the power transformer and transistors in the circuit from burning out due to temperature rise caused by the large current that flows when the motor starts or stops. For example, the present invention can be applied to a turntable drive motor for a disc player of an audio device.

The prior art and its problems will be explained with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram of a speed control system of a motor that drives a turntable of a disk player at a constant speed, and FIG. 2 is a waveform diagram of signals at various parts in FIG.

In Fig. 1, 1 is a DC motor that drives a turntable 2, and 3 is a frequency/voltage converter that detects an AC signal with a frequency proportional to the number of rotations of the motor 1, and converts this detected AC signal into a monostable By inputting it into a multi-circuit and smoothing the output of this monostable multi-circuit, a DC voltage proportional to the motor speed is obtained and output.

Reference numeral 4 denotes a power supply that supplies stabilized DC voltage to the frequency/voltage converter 3 and an amplifier 7 to be described later, and is composed of a power transformer that transforms a commercial AC voltage, a rectifier circuit, and a DC voltage stabilization circuit.

5 is a reference power supply that generates a reference DC voltage, and 6 is a comparator that calculates the deviation between the reference voltage from the reference power supply 5 and the DC voltage from the frequency/voltage converter 3, and outputs the resulting deviation signal. Send to amplifier 7.

The output of this amplifier 7 is applied to the motor 1, and the speed of the motor 1 is controlled in the direction of making the deviation signal zero.

Figure 2 shows that the capacity of the power transformer used in the power supply 4 in the circuit of Figure 1 is sufficiently large, and that a completely stabilized and smoothed DC voltage ±Vcc is output from the DC voltage stabilization circuit. It shows an operation waveform diagram of each part signal when the

4 in Figure 2 is the waveform of the DC voltage Vcc output from the DC voltage stabilization circuit of the power supply 4 in Figure 1, 3' is the output waveform of the monostable multi-circuit in the frequency/voltage converter 3, and 7 is the amplifier 7 is a diagram showing the waveform of the output signal, and 2 is a diagram showing the rotational speed change state when the turntable 2 is started.

□According to the circuit in Figure 1, it is possible to control the rotation speed of the turntable 2 at a constant speed, but when it starts or stops, the motor 1
A large current flows through the motor, and the armature coil burns out due to the temperature rise caused by this current, and parts with large capacitance are required for the detector that detects the motor rotation speed and the monostable multi-circuit that receives this detection signal as input. Furthermore, if the motor 1 is a transistor-driven motor, there is a problem in that the drive transistor, the control transistor in the power supply 4, etc. must be made large enough to withstand burnout or burnout.

This invention detects sudden changes in rotation speed when starting or stopping the motor.
It is an object of the present invention to provide a motor drive circuit protection device that automatically suppresses the problem with a simple circuit configuration, thereby making it possible to eliminate the above-mentioned inconveniences that occur when starting or stopping the motor.

The feature of this invention is that the power supply for the monostable multi-circuit in the frequency/voltage converter includes a ripple large enough to reverse the operation of the monostable multi-circuit when the motor starts or stops, and when the motor rotates at a constant speed. The solution is to use a power supply that generates a ripple-containing DC voltage whose ripple is reduced to a level that does not allow the monostable multicircuit to operate.

The present invention will be explained below with reference to the drawings.

FIG. 3 is a circuit diagram of an embodiment of a power supply that generates a ripple-containing DC voltage that generates large ripples when the motor starts or stops, but that ripples disappear when the motor is rotating at a constant speed.

In Figure 3, e is a commercial AC power supply, Tr is a step-down power transformer that also serves as insulation, D1 to D4 are rectifying diodes, C1 and C2 are smoothing capacitors, and ±VB are capacitors C1 and C2, respectively. This is the DC voltage generated at the terminals.

Ql and Q2 are transistors for voltage stabilization, and R□ and R2, which are connected in series to the load, are transistors Q1. Q
The resistor inserted between the base terminal and collector terminal of 2, Z
Dl and ZD2 are constant voltage diodes that supply a reference voltage for voltage stabilization, and ±Vcc is a stabilized DC voltage that is output.

Figure 3 shows the relationship between the output voltage ±Vcc in the circuit and the capacitor terminal voltage ±VB before voltage stabilization.
In the figure and FIG. 5, a shows the waveform of ±vB, and b shows the waveform of ±Voo.

If the circuit in FIG. 3 is used as the power supply 4 in FIG. 1 and the capacity of the power transformer Tr in FIG. 3 occurs.

This is because the current flowing through the motor 1 is large at startup and stoppage, and therefore the voltage drop in the power transformer Tr is large.

The waveform of ±Voo obtained by voltage stabilization of the voltage regulator 8 with such a large pulsation amplitude is as shown in Figure 4.
It will contain notupuru.

However, the voltage drop across the power transformer Tr during normal operation when the motor 1 is rotating at a constant speed is smaller than the voltage drop during startup or stoppage, and therefore the VB waveform is shown in Figure 5a. As such, the pulsation amplitude is small.

Constant voltage diode ZD1. Zener voltage V2D of ZD2
By selecting a value lower than the minimum voltage value of the pulsating voltage VB, the output voltage V can be stabilized.

0, a completely smoothed DC voltage as shown in FIG. 5b1 can be obtained.

FIG. 6 is a circuit diagram explaining that a monostable multi-circuit performs inversion operation due to power supply ripple.

In FIG. 6, Q3. Q4 is a transistor, C3 is a capacitor, D5 is a diode, R3-R6 are resistors, ±
Vcc is a driving voltage.

If the driving voltage is a completely smoothed DC voltage, transistor Q3 will be activated when there is no input on the INPUT side.
is off, transistor Q4 is on, and each time a trigger pulse is received on the INPUT side, transistor Q4 is turned off for a certain period of time determined by capacitor C3 and resistor R4, and the output pulse is output from the transistor. It occurs between the ground and collector of Q4.

However, 1. If the driving voltage ±VCo includes ripples, for example -V.

Considering the case where Ripple is on C, INPUT
When there is no input on the side and transistor Q4 is in the on state, if the absolute value of 1 co becomes smaller than a certain value due to the ripple on -Vcc, transistor Q4
The base and emitter of the transistor Q4 are reverse biased, and the transistor Q4 is turned off, thereby generating an output pulse.

Also, ten v. Considering the case where there is a ripple on C, this voltage is connected to resistor R3, capacitor C3, and diode D.
Similarly to the above, when the magnitude of +Vcc falls below a certain predetermined value, transistor Q4 is turned off, thereby generating an output pulse.

In other words, when a ripple-containing DC voltage is used as a power source for driving a monostable multi-circuit, if the amplitude of the included ripple exceeds a certain level, the monostable multi-circuit will be triggered by this ripple, and the ripple size will increase. An output pulse is generated each time the value exceeds a certain predetermined value.

Figures 7 and 8 are diagrams of an example in which a power supply having the characteristics shown in Figure 4 is used in the turntable constant speed control system of Figure 1; Figure 7 is an overall circuit diagram; The figure is a diagram of signal waveforms at each part.

In Fig. 7, 1 is a permanent magnet type two-phase motor;
12 is the leading phase armature coil, 12 is the lagging phase armature coil, and 13 is the rotor magnet.

Leading phase coil 11 and lagging phase coil 12 are electrically 90
The rotor magnet 1 is arranged so that the phase difference is in degrees.
A turntable 2 is directly connected to the rotating shaft of 3.

H1 and H2 are Hall elements, which are fixed at predetermined positions within the motor 1 so as to detect the magnetic pole position of the rotor magnet 13.

Hl is a leading phase Hall element whose detection output is amplified by leading phase amplifier OP1 and applied to the leading phase coil 11, H2 is a lagging phase Hall element whose detection output is applied to lagging phase amplifier OP2. Amplified and delayed phase coil 12
is applied to

R8-R15 are amplifier OP1. This is a resistor inserted in the illustrated position of OP2.

4 is a power supply, which has the characteristics explained in FIG. 4, and whose output voltage ±vcc is applied to the amplifier OP1. It is applied as a voltage for driving the monostable multi-circuit in OP2 and the frequency/voltage converter 3.

Reference numeral 10 denotes a speed generator for detecting the speed of the motor 1, which generates an alternating current voltage having a frequency proportional to the motor speed.

31 is a waveform shaping circuit in the frequency/voltage converter 3, 32 is a monostable multicircuit, and 33 is a smoothing circuit.

In the waveform diagram of FIG. 8, a portion A on the left side of the broken line shows the waveforms of the respective signals when the motor 1 is started, and a portion B on the right side of the broken line shows the waveforms of the respective signals when the motor 1 is at a constant speed.

Hl is the leading Hall element H1, H2 is the lagging Hall element H
2, and a is the output voltage ± of the power supply 4, which has the characteristic that no ripple occurs even when the motor starts or stops.
Amplifier OP1 when using a power supply that generates Voo.
The output waveform of OP2 is shown.

4 is a waveform diagram of the output voltage ±voc when a power supply 4 is used that has a characteristic of generating an output voltage containing ripple in its output voltage Vcc during high load current when starting or stopping the motor. It is.

In the part P of this waveform diagram, the leading phase armature coil 11.
The current flowing through both lagging phase armature coils 12 is +vco
Since it is supplied with more power, a larger ripple will occur, which will trigger the monostable multi-circuit 32.

Furthermore, in the N portion, since the current flowing through both armature coils 11 and 12 is supplied from -vcc, a large ripple occurs, which causes the monostable multi-circuit 32 to be triggered.

Amplifier OP1 when a power supply that generates such ripple is used as power supply 4. FIG. 8 shows the output waveform of OP2.

This will be explained in more detail with reference to FIG.

When the motor is rotating at a constant speed, the output waveform of the monostable multi-circuit 32 in FIG. 7 is as shown in FIG. 9A, for example.
This is smoothed by the smoothing circuit 33 and becomes as shown in B.

The output of this smoothing circuit 33 is compared with the reference power supply 5, and the motor is controlled at a constant speed. However, if the monostable multi-circuit 32 is triggered by power supply ripple at startup,
The outputs of the monostable multi-circuit 32 and the smoothing circuit 33 are as shown in Figure 0 and Figure D, respectively, and as a result, the output of the comparator 6 is as shown in Figure E, and current no longer flows through the Hall elements H1 and H2. The output waveform of amplifier OP1 is shown in diagram F.

However, in the above description, it is assumed that the power supply ripple frequency is higher than the speed generator frequency at constant speed.

When starting or stopping the motor at positions c and e in Figure 8, +Voo is connected to the leading phase armature coil 11.
Therefore, the lagging phase armature coils 12 are supplied with current from 1 and 0, respectively, so that the control transistors Q1 and 10 of the power supply circuit (FIG. 3) The current flowing through Q2 is +Vcc.

This is approximately % of the case where current is supplied to both armature coils 11 and 12 from either one of Voo.

In addition, in this case, since the unregulated power supply voltage (1)8 increases only approximately, the control transistor Q1. The Q2 collector loss is about %.

Starting the motor with the device in Figure 8, d and f,
In the case of a stoppage, no current flows through the armature coils 11 and 12, so the control transistor Q in the circuit of the power supply 4
1. The current flowing through Q2 is extremely small, the collector loss is small, and the load on the power transformer is also extremely small.

According to the present invention, it is possible to reduce the capacity of transistors and power transformers used in the motor drive circuit, and the device can be made smaller and cheaper. Temperature rise can be kept low.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of the prior art, FIG. 3 is a circuit diagram of an embodiment of the present invention, FIGS. 4 and 5 are diagrams showing waveforms in the circuit of FIG. 3, and FIG. An explanatory diagram of a monostable multi-circuit inverting operation due to power supply ripples, Fig. 7 is an embodiment circuit diagram of a turntable drive circuit to which the present invention is applied, Fig. 8 is a waveform diagram of signals of various parts of the circuit shown in Fig. 7, Fig. 9 This figure is a waveform diagram for explaining in detail the waveforms in FIG. 8. Explanation of symbols, 1...DC motor, 2...
・Turntable, 3...Frequency/voltage converter, 4...Power supply, 5...Reference power supply, 6.
...Comparator, 7...Amplifier, 11.12
... Armature coil, 13 ... Rotor magnet, 31 ... Waveform shaping circuit, 32 ...
... Monostable multi-circuit, 33... Smoothing circuit.

Claims (1)

[Scope of utility model registration request] Detects an AC signal with a frequency proportional to the motor rotation speed, operates a monostable multi-circuit, smoothes the output, compares the DC voltage obtained with a reference voltage, and controls the deviation to zero. In a motor drive circuit that drives a motor at a constant speed, when the motor is rotating at a constant speed, the monostable multi-circuit is driven by a ripple large enough to prevent the monostable multi-circuit from operating in reverse when the motor is rotating at a constant speed. By installing a power supply that generates ripple-containing DC voltage with ripples large enough to cause the stable multi-circuit to operate in reverse, sudden changes in motor speed can be suppressed to automatically reduce the temperature rise of circuit components when the motor starts or stops. A motor drive circuit protection device characterized by suppressing