JPH0522478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor drive circuit, and more particularly to a motor forward/reverse switching circuit.

A three-phase motor will be explained as an example of a conventional DC motor. Fig. 1 is an explanatory diagram of the rotation principle of a three-phase bidirectional energizing type motor, and Fig. 2 is a logic group showing switching of the energizing section to each coil (hereinafter referred to as
(denoted as U ₁ , U ₂ , V ₁ , V ₂ and W ₁ , W ₂ respectively). Further, FIG. 3 shows a general drive circuit for a three-phase motor. In Fig. 1, 1 is a rotor;
2, 3, and 4 are three-phase coils U, V, and W of the stator (hereinafter simply referred to as coil U, coil V, and coil W)
and represents relative positional relationships. In order to simplify the explanation, the permanent magnet rotor 1 is fixed, and the coils U, V, and W are attached to the rotor 1.
It is assumed that the object moves relative to the object. In addition, the rotor 1 and the coils U, V, and W are developed linearly, and the magnetic field generated by the permanent magnet in which the N and S poles of the rotor 1 are arranged alternately is generated by the coils U, V, and W.
A closed magnetic path is formed between the yoke plates 5 and 6 which face each other with V and W in between. Here, each coil U, V, W is wound over approximately 180 degrees of electrical angle (that is, one N pole or one S pole), and the coils U, V, W are It is assumed that they are arranged with a phase difference of 120 degrees in electrical angle. Waveform groups 7 to 12 shown in FIG.
For example, the rotational position of the motor is detected using a Hall element or the like. Figure 3 shows the general 3
This shows the phase motor drive circuit, 13, 14,
15 indicates a PNP transistor (hereinafter referred to as Q ₁ , Q ₂ , Q ₃ ), and 16, 17, 18 indicates an NPN transistor (hereinafter referred to as Q ₄ , Q ₅ , Q ₆ ). 19 is a coil U, 20 is a coil V, 21 is a coil W, and 22 is a motor drive power source (hereinafter referred to as a battery).
Connect the emitters of Q ₁ , Q ₂ , and Q ₃ in parallel, _and
Connect the collectors of Q ₂ and Q ₃ to the corresponding collectors of Q ₄ , Q ₅ , and Q ₆ and ground the emitters of Q ₄ , Q ₅ , and Q ₆ , respectively, and connect the Q ₁ and Q ₄ and Q ₂ mentioned above and
The connection between the collectors of Q ₅ , Q ₃ and Q ₆ is connected to the corresponding coil U ₁₉ , coil V ₂₀ and coil
W ₂₁ and the other ends of the three coils U, V, and W are connected to each other. Note that the voltages applied to the bases of the transistors in the figure U ₁ , V ₁ , W ₁ , U ₂ , V ₂ , W ₂
are made to match the voltage waveform symbols in FIG. 2 above, and the waveform group shown in FIG. 2 is the drive voltage waveform (hereinafter referred to as waveform) in the motor drive circuit of FIG. 3.

Next, the principle of rotation of the motor will be described. First of all, as shown in Figures 1 and 2, each phase coil is assumed to be at a position of θ ₀ (t ₁ ), and when each coil moves from this point by an electrical angle of 60° (θ ₁ ), that is, When the coil U reaches the N pole (t ₂ ), Q ₁ is turned ON by waveform U ₁ and Q ₅ is turned ON by waveform V ₂ . As a result, the motor drive current changes from Q ₁ to coils U, V
Flows to _Q5 via. Here, a Lorentz force in the same rotational direction is generated in each coil by the current flowing through the front and rear ends of the coils U and V and the magnetic flux crossing these coils. Therefore, each coil moves to the position θ ₂ which is further advanced by an electrical angle of 60° (t ₃ ). At this time, waveform V ₂ is “L”
, and the current to coil V is cut off. However, since _Q6 turns ON due to waveform _W2 , the motor drive current flows from _Q1 to _Q6 via coil U and coil W. Since the rotational force generated in the coils is the same as the force and direction described above, each coil moves to the position θ ₃ which is further advanced by 60 degrees in electrical angle (t ₄ ). Thereafter, the motor rotates while switching the coil current in the same manner.

Next, to reverse the rotation direction of the motor, the direction of the current flowing through the coils can be reversed. To do this, the drive waveforms U ₁ and U ₂ , V ₁ and V ₂ , and W ₁ and W ₂ of the motor drive circuit shown in FIG. 3 may be replaced, and their polarities may be reversed. Now waveform U ₁ ,
A detailed explanation will be given below using U ₂ as an example. FIG. 4 shows a state diagram of waveforms U ₁ and U ₂ during forward/reverse switching. The left side of the dashed line T in the figure is the forward rotation mode, and the right side is the reverse rotation mode. In other words, the drive waveform with waveform U ₁ during forward rotation changes to the drive waveform with waveform U ₂ when switching to reverse mode, with the polarity reversed, and similarly, the drive waveform with waveform U ₂ during forward rotation. but,
When switching to reverse mode, the polarity is reversed and the drive waveform becomes _U1 . Looking at the waveform _U2 , it is "H" just before switching from normal rotation to reverse rotation. and
Even if the base of _Q4 changes to reverse mode and the waveform _U2 changes to "L", it remains ON for a while due to the base accumulation effect. On the other hand, when _Q1 changes to reverse mode, it immediately changes to the ON state by waveform _U1 . Therefore, when switching the motor rotation direction, Q ₁ , Q ₄
Both are in the ON state, and from battery 22
There was a problem that the current flowing to the ground via Q ₁ and Q ₄ became excessive. In the above explanation, the relationship between waveforms U ₁ and U ₂ was described for convenience, but
A similar phenomenon occurs with waveforms V ₁ and V ₂ or waveforms W ₁ and W ₂ as well.

SUMMARY OF THE INVENTION An object of the present invention is to provide a means for overcoming the above-mentioned problems and preventing excessive current from flowing through a motor drive circuit when switching the rotational direction of a motor.

In order to achieve the above object, the present invention turns off the speed control terminal when switching the rotation direction using a forward/reverse switching signal, and provides a drive current cutoff period to prevent excessive current from flowing. .

The present invention will be explained below with reference to a circuit diagram illustrating the principle of the present invention shown in FIG. 5 and a waveform diagram of a motor forward/reverse switching signal shown in FIG. 6. First, the configuration will be explained with reference to FIG. In each figure, the same or equivalent parts are given the same reference numerals. 23 is a motor drive signal generator, 24 is a terminal, 25 is a level discriminator, and 26 is a switch.The difference from the conventional circuit shown in FIG. 3 is that each base of Q ₁ to _{Q 6} is connected in parallel. The motor drive signal generator 23 is connected to the terminal 24 and the level discriminator 25, and the level discriminator 25 is connected to the switch 26, and one end of the switch 26 is connected to the motor drive signal generator 23. By connecting one side of the battery 22 and grounding the other end, the motor drive signal generator 23 receives the motor forward/reverse switching signal voltage 27 shown in FIG. 6 which is input to the terminal 24.
A forward drive waveform or a reverse drive waveform is applied to the bases of Q _{1 to Q 6 depending on the polarity of the Q 1} to Q ₆ .

Next, the effect will be explained. As shown in Figure 6,
When the rotational direction of the motor is switched from the forward rotation direction to the reverse rotation direction, the forward/reverse rotation switching signal voltage 27 changes from "L" to "H". Then, arbitrary set voltages a and b are provided within this voltage change range, and the level discriminator 25 is turned off only in the period _T1 in which the forward/reverse switching signal voltage 27 passes through the points a and b. This opens the switch 26 and opens the battery 22 circuit.
Since the motor is turned off, no drive current flows to the motor during this _T1 period. Further, the same effect occurs when the rotation of the motor is switched from the reverse rotation direction to the forward rotation direction.

Next, one embodiment of the present invention will be described based on the drawings. FIG. 7 is a circuit diagram showing a specific embodiment of the present invention, and FIG. 8 is a characteristic diagram of a motor forward/reverse switching circuit. First, the configuration will be explained. 2
8 is a speed control signal input terminal; 29 is a converter that converts the amount of current from the current source 30 into an amount proportional to the speed control voltage input to the speed control signal input terminal 28;
Reference numeral 31 denotes a changeover switch, which selects 30a of the current sources 30 according to the signal from the motor drive signal generator 23.
The current is passed through the drive stage PNP transistor 32 (hereinafter referred to as
Q ₇ ) serves as the basis for the
Note that in FIG. 7, for the sake of simplicity, only one phase of the drive stage transistor is shown, and the motor drive coils U ₁ , V ₁ , W ₁ , U ₂ ,
V ₂ and W ₂ are also not shown. 33 is also a changeover switch, which changes the current of 30b of the current sources 30 to the drive stage according to the signal from the motor drive signal generator 23.
It serves to supply the base of the NPN transistor 34 (hereinafter referred to as _Q8 ). Note that 35 is a switch, 36 is a constant current source, and 37 and 38 are
PNP transistors (hereinafter referred to as Q ₉ and Q ₁₀ ),
A comparator is configured using a constant voltage source 39 as a reference voltage (Eb), and 40 and 41 are resistors. Also 4
2 is a constant current source, 43 and 44 are PNP transistors (hereinafter referred to as Q ₁₁ and Q ₁₂ ), 45 is an NPN transistor (hereinafter referred to as Q ₁₃ ), 46 is a constant voltage source (Ea), and 47 is also a constant current source. Indicates a constant voltage source. A selector switch 31 is connected in parallel to the motor drive signal generator 23.
33, and the movable contact of the changeover switch 31 is connected to 30a of the current sources 30, and the movable contact of the changeover switch 33 is connected to 30b of the current sources 30. Motor drive coils U ₁ , V ₁ , W ₁ (not shown) are installed between the fixed contacts of the changeover switch 31 and the base of Q ₇ , respectively.
, and motor drive coils U ₂ , V ₂ , W ₂ (not shown) are connected between the fixed contacts of the changeover switch 33 and the base of Q ₈ , respectively, and the above
Q ₇ and Q ₆ are connected in series to the battery 22.
The converter 29 is connected to the current source 30 and also to a contact of a switch 35 having a speed control signal input terminal 28, and the other contact of the switch 35 is grounded. Next, a series circuit of Q ₉ and resistor 40 and Q ₁₀ and resistor 4 are connected in parallel and symmetrically to constant current source 36 connected to constant voltage source 47.
In a series circuit with 1, connect terminal 2 to the base of Q ₉ .
A constant voltage source 39 is connected to the bases of Q 4 and Q ₁₀ , respectively, and the collectors of Q ₉ and Q ₁₀ are connected to the motor drive signal generator 23, respectively.
Further, a constant current source 42 connected to the constant voltage source 47
At collector earth _{Q 11} and _{Q 12 connected} in parallel and _{symmetrically to} , Q ₁₁ and Q ₁₂ are connected to the base of Q ₁₃ , the collector of Q ₁₃ is connected to the switch 35, and a constant voltage source 46 is connected to the emitters.

Next, the effect will be explained. Figure 8 shows Q ₉ ,
This figure shows a characteristic diagram of a comparator configured by Q _10. In the figure, the horizontal axis is the forward/reverse switching signal voltage 27 input to the base of Q ₉ , and the vertical axis is Q ₉ and Q ₁₀ .
Both characteristic curves 48 and 49 are shown on the same drawing as the collector voltage of . The figure B corresponds to the characteristic diagram of the figure A above.
5 is a characteristic curve 50 showing the period during which the switch 5 is turned on.
During forward rotation _{, Q9} is ON and _Q10 is OFF, so
Q ₁₁ is in the OFF state and Q ₁₂ is in the ON state. Therefore, all the current of the constant current source 42 flows to _Q12 , and the base voltage of _Q13 is kept at V _F (voltage when the transistor is ON).However, the constant voltage source 46 is connected to the emitter of _Q13 . Because of this, _Q13 does not turn on.

Next, when the motor switches from forward rotation to reverse rotation (section indicated by _T0 in FIG. 8B), the forward/reverse rotation switching signal voltage 27 corresponding to the terminal 24 increases, so that
Q ₉ turns OFF and Q ₁₀ starts to turn ON. Therefore, the 8th
As shown in Figure A, when the collector voltage of Q ₁₀ increases and reaches E _a , the base voltage of Q ₁₃ becomes E _a +V _F , so Q ₁₃ turns ON. At this time, switch 35
is activated, dropping the speed control signal input terminal 28 to "L" and cutting off the current to _Q7 and _Q8 . Furthermore, the fifth
In the principle explanatory circuit diagram shown in the figure, the switch 26 is
However, in the embodiment shown in Fig. 7, switch 3 is turned OFF.
Turn on 5 to get the same effect. When the forward/reverse switching signal voltage further increases, _Q9 turns OFF,
Since Q ₁₀ turns ON, Q ₁₁ turns ON, the base voltage of Q ₁₃ is fixed at V _F , and Q ₁₃ turns OFF again. Then, the switch 35 is turned off and the current supply to Q ₇ and Q ₈ is resumed.

Note that a similar operation is performed when the rotation is changed from reverse rotation to normal rotation.

As explained above, according to the present invention, the motor forward/reverse switching signal is inputted with a predetermined time constant, and the forward/reverse switching is performed within the motor drive current cutoff period. Excessive pulse current does not flow through the circuit, eliminating problems such as damage to the drive transistor, and
The effect of being able to prevent power supply voltage fluctuations and unnecessary radiation caused by the above-mentioned excessive current can be obtained.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the rotation principle of a three-phase bidirectional current-carrying motor, Fig. 2 is a logic group diagram showing switching of the energizing section to each coil, and Fig. 3 is a general three-phase motor drive circuit diagram. FIG. 4 is a state diagram of waveforms during forward/reverse switching, FIG. 5 is a circuit diagram explaining the principle of this invention, and FIG. 6 is a waveform diagram of the motor's forward/reverse switching signal.
FIG. 7 is a circuit diagram showing a specific embodiment of the present invention, and FIG. 8 is a characteristic diagram of a motor forward/reverse switching circuit. Explanation of symbols, 1... Rotor, 2, 3, 4... 3-phase coil of stator, 5, 6... Yoke plate, 7-1
2...Waveform group, 13-15...PNP transistor _Q1 , _Q2 , _Q3 , 16-18...NPN transistor _Q4 , _Q5 , _Q6 , 19...Coil U, 20...Coil V, 21...Coil W, 22...Battery,
23...Motor drive signal generator, 24...Terminal,
25...Level discriminator, 26...Switch, 27
...Forward/reverse switching signal voltage, 28...Speed control signal input terminal, 29...Converter, 30...Current source, 3
1, 33...Selector switch, 32...PNP transistor _Q7 , 34...NPN transistor _Q8 , 3
5... Switch, 36, 42... Constant current source, 3
7, 38...PNP transistor Q ₉ , Q ₁₀ , 39,
46, 47... Constant voltage source, 40, 41... Resistor,
43, 44...PNP transistor Q ₁₁ , Q ₁₂ , 4
5...NPN transistor Q ₁₃ , 48, 49, 50
...Characteristic curve.

Claims (1)

[Claims] 1. A rotor magnet and N for rotationally driving the rotor magnet (N is an integer of 2 or more).
A motor drive signal generator for driving a motor equipped with stator coil groups of each phase, which detects the rotational position of the rotor magnet and generates a energization period switching signal for the stator coil group of each phase based on the detection result. a motor drive stage consisting of a plurality of transistors that sequentially switch and supply drive current to the stator coil group of each phase in response to the energization period switching signal; and a motor drive stage that detects the rotational speed of the rotor magnet and generates a speed control signal. a converter that controls the amount of drive current supplied from the motor drive stage to the stator coil group of each phase according to the speed control signal; In the drive circuit, the motor drive signal generator is controlled according to the voltage level of the forward/reverse rotation switching signal, and the energization period switching signal is switched from one of the energization period switching signal for forward rotation and the energization period switching signal for reverse rotation to the other; means for switching the rotational direction of the rotor magnet; and during a period of voltage level change for switching the rotational direction of the rotor magnet with the forward/reverse rotation switching signal;
A motor characterized by comprising means for detecting a period in which the voltage level is in a preset level range, and prohibiting the supply of drive current from the motor drive stage to the stator coil group of each phase during the period. Forward/reverse switching circuit.