JPH01206895A - Stepping motor drive circuit - Google Patents

Abstract

PURPOSE:To prevent generation of a high current, by connecting the output of two comparators detecting the collector voltage of a transistor driving first- phase and third-phase windings respectively to the base of a transistor with a phase different from that of another transistor. CONSTITUTION:The collector voltage of a transistor 1 driving a first-phase winding 10 and that of a transistor 2 driving a third-phase winding 20 are detected by comparators 11, 12 and inputted to the bases of driving transistors 2, 1, respectively. Consequently, while said transistor 2 is in the ON state, the output of said comparator 12 has a low electric potential and the transistor 1 maintains the OFF state. While the transistor 1 is in the ON state, the transistor 2 maintains the OFF state by the comparator 11. Therefore, the transistors 1 and 2 are not in the ON state at the same time, and a high current can be prevented from flowing through the windings 10, 20 of a stepping motor.

Description

Detailed Description of the Invention (Industrial Application Field) This invention relates to a stepping motor drive circuit that is often used as a digitally controlled drive device, and in particular, a stepping motor that eliminates the adverse effects caused by the switching time difference between two transistors that drive a bifilar winding. This invention relates to a motor drive circuit.

(Prior Art) In the switching operation of a transistor, the switching time is different depending on when the transistor changes from a non-conducting state to a conducting state and when it changes from a conducting state to a non-conducting state. However, conventionally, in this type of drive circuit, even if there is a difference in switching delay time between the drive transistors in the final stage, this difference is not normally processed, and only when it is especially necessary, other logic It is used with an additional circuit.

(Problems to be Solved by the Invention) The conventional stepping motor drive circuit described above, for example, changes the input signal to change the first transistor that drives the first phase winding from an off state to an on state. If the second transistor that drives the third phase winding is changed from on to off at the same timing as the input signal changes, the first transistor will immediately turn on, but the second transistor will turn on immediately. Transistors have a switching delay time, so after being on for a few microseconds,
Turns off. Therefore, there is a time period during which both the first transistor and the second transistor are in the on state for several microseconds. However, since the stepping motor's windings have bifilar windings for the first and third phases, the inductance component of the windings is lost, and the stepping motor's first and third phase windings have a very large amount of inductance. A large current flows through.

Conversely, even if the timing of the input change to change the first transistor from the on state to the off state and the second transistor from the off state to the on state is performed at the same time, the first phase winding and the third phase winding A very large current flows through the winding.

These large currents not only do not contribute to the torque generated by the motor, but also have the risk of damaging the first and second transistors that drive them, and become a source of noise that affects other circuits. There are drawbacks.

The present invention eliminates such drawbacks and prevents the two transistors that drive the two windings of the stepping motor's PI-FI winding from becoming conductive at the same time, thereby reducing the risk of transistor damage and noise generation. The purpose is to provide a stepper motor drive circuit without any steps.

(Means for Solving the Problems) In order to achieve the above object, the stepping motor drive circuit of the present invention drives the first phase winding 10 of the bifilar winding with the first transistor 1, and In a stepping motor drive circuit in which the third phase winding 20 is driven by the second transistor 2, in order to clamp the base potential of the second transistor 2, the collector voltage of the first transistor 1 is adjusted by the first comparator 11. The output of the first comparator 11 is connected to the base circuit of the second transistor 2, and in order to clamp the base potential of the first transistor 1, the collector voltage of the second transistor 2 is set to the second The output of the second comparator 12 is connected to the first transistor 10 base circuit.

(Example) Next, the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a time chart showing examples of signal waveforms input to the embodiment of FIG. 1.

As shown in FIG. 1, in this embodiment, the first phase winding 10 and the third phase winding 2 of the stepping motor are similar to the prior art.
The open collector gate circuit Z0 inputs a signal S0 that commonly controls 0 and sends out its inverted output, and the gate circuit Z turns on and off the winding 10 and the winding 2.
A first-phase and third-phase common control circuit is constituted by a series circuit of transistors 3 and 4 that simultaneously supply drive circuit power supply voltage VD to zero.

Further, an open collector gate circuit Z1 inputs the first phase drive signal S1 and sends out its inverted output, and a first transistor that controls the current flowing through the first phase winding 10 by the output of the gate circuit Z. 1 constitutes a first phase drive circuit. Also, input the third phase drive signal S,
Open collector gate circuit Z that sends out its inverted output
, and the output of the same gate circuit Z, the third phase winding 20
A third phase drive circuit is configured by the second transistor 2 that controls the current flowing in the second transistor 2 .

Furthermore, as a circuit for removing the adverse effects caused by the switching delay of transistor 1 or 2, which is a feature of this embodiment, a voltage obtained by dividing the collector voltage of the first transistor 1 by a resistor hole and a A first comparator has a reference voltage Vn obtained by dividing the logic circuit power supply voltage VCC with resistors R1 and R6 as an input, and has an open collector output connected to the base of the second transistor 2. 11, the voltage obtained by dividing the collector voltage of the second transistor 2 by resistors 几 and R4 are used as positive inputs, the reference voltage k is used as a negative input, and the output of the open collector is used as the base of the first transistor 1. The connected second comparator 12 constitutes a large current prohibition circuit.

Next, the operation will be explained.

Now, at time t1 shown in FIG. 2, the first phase drive signal S1 (in the figure) changes from high potential to low potential, and the output of open collector gate circuit Z1 becomes high potential, so transistor 1
An attempt is made to cause transistor 1 to turn on by causing a base current to flow through it.

At the same time, the third phase drive signal S changes from a low potential to a high potential, and the output of the open collector gate circuit Z becomes a low potential, attempting to turn off the transistor 2. However, since transistor 2 has a switching delay time, it remains on for several microseconds.

While transistor 2 is on, the potential obtained by dividing the collector voltage of transistor 2 is applied to comparator 1.
Since it is lower than the reference voltage Vn which is the negative input of the comparator 12, the output of the comparator 12 becomes a low potential, suppressing the base potential of the transistor 1 to a low potential and keeping the transistor 1 in an off state. After that, when transistor 2 leaves the on state and the collector voltage of transistor 2 increases, comparator 12
is inverted and transistor 1 is turned on. Therefore, at the instant of time t, transistors 1 and 2 are not turned on at the same time.

Similarly, at time t2 shown in FIG. and 2 are never on at the same time.

(Effects of the Invention) As explained above, the present invention allows the outputs of two comparators that detect the respective collector voltages of the transistor that drives the first phase winding and the transistor that drives the third phase winding to be set to be different from each other. By connecting to the bases of the phase drive transistors, the two transistors are turned on at the same time, which has the effect of preventing large current from flowing through the winding circuit of the stepping motor.

Therefore, by using this embodiment, damage to the transistor due to the large current can be prevented with a simple circuit without requiring any other logic circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. FIG. 2 is a time chart showing examples of each waveform input to the embodiment of FIG. 1. 1... First transistor 2... Second transistor 3.4... Transistor 10... First phase winding 11 of stepping motor...
First comparator 12...Second comparator 20...Third phase winding R of the stepping motor
,,R,,R,,R,,R,...Resistor So...Common control signal S,...First phase drive signal S! ...Third phase drive signal VCC...Logic circuit power supply voltage VD...Drive circuit power supply voltage ■R...Reference voltage 2, . 21,2. ...Gate circuit patent applicant NEC Corporation

Claims (1)

[Claims] In a stepping motor drive circuit in which a first phase winding of a bifilar winding is driven by a first transistor, and a third phase winding of the bifilar winding is driven by a second transistor, the base potential of the second transistor is , the collector voltage of the first transistor is compared with a reference voltage by a first comparator, the output of the first comparator is connected to the base circuit of the second transistor, and the collector voltage of the first transistor is A second comparator compares the collector voltage of the second transistor with a reference voltage to clamp the base potential of the second transistor.
A stepping motor drive circuit in which the output of the comparator is connected to the base circuit of the first transistor.