JPS6096197A - Drive circuit of 1-2 phase excitation type step motor - Google Patents

Abstract

PURPOSE:To smoothen a torque by providing switching means for switching the base current of a control transistor, thereby switching the currents of one phase exciting time and two phase exciting time in case of driving 1-2 phases. CONSTITUTION:When an ON signal is inputted from an input signal terminal 1, a driver transistor 6 becomes ON, and a voltage is applied to a resistor 22. This voltage becomes the base voltage of a feedback transistor 10, and balanced at the point that becomes the same as the base voltage of a current controlling transistor 18, and the collector current of a driver 6 becomes constant. When an ON signal is inputted to an input terminal 5, the base voltage of the transistor 18 decreases, and the constant current value decreases. This switching is performed at the one phase exciting time and at the two phase exciting time, thereby driving 1-2 phases.

Description

[Detailed Description of the Invention] Technical Field> The present invention relates to a drive circuit for a step motor, and more specifically, a drive circuit that smoothes the torque during one-phase excitation and two-phase excitation by switching a constant current value. It is about conversion.

<Prior Art> Conventionally, in the 1-2 phase drive of a step motor, a method of changing the voltage during 1-phase excitation and during 2-phase excitation by driving with two power sources has often been used.

FIG. 2 shows an example of a conventional two-power supply voltage circuit. In this circuit, a desired voltage can be selected by switching transistors 28 and 29. However, since the step motor's torque is determined by ampere turns, this method
The torque during phase excitation and two-phase excitation cannot be accurately smoothed.

Further, FIG. 3 shows a general freely configurable chopping type constant current circuit. In this circuit, comparators 50 and '
51 performs voltage comparison to determine the constant current value. At this time, the current value is stopped at the self-excitation frequency. This frequency is in the audible range and is audible. In this circuit, by changing the comparison voltages of comparators 30 and 61, 1! Although the flow value can be set freely, there are drawbacks such as the influence of noise and vibration caused by chopping. Also, a large capacity transistor was required to switch the current value.

Purpose> An object of the present invention is to smooth the torque by switching the current during 1-phase excitation and during 2-phase excitation when driving a step motor in 1-2 phases.

Another object of the present invention is to realize a freely settable constant current drive circuit using only small capacity current transistors without using large capacity current transistors.

<Characteristics> In the constant current drive of a step motor, the present invention inserts a resistor between the emitter of the drive transistor and the ground, applies this resistance voltage to the base of the feedback transistor, and connects this collector to the base of the drive transistor. By doing so, the current is limited, and by making the emitters of the four-phase feedback transistors common, placing a transistor in a differential relationship with this, connecting it to a constant power supply, and switching the base voltage of this transistor, When driving the step motor in 1-2 phases, the current value during 1-phase excitation and during 2-phase excitation is switched to smooth the torque during 1-phase excitation and 2-phase excitation.

Figure 1 shows an embodiment of the present invention, in which 1, 2, 3.4 are input signal terminals for each phase, 5 is a switching input signal terminal, and 6, 7 are input signal terminals for each phase.
, 8.9 is a Darlington transistor for driver, 10
, 11, 12, 15 are feedback transistors, 14, 1
5, 16, 17 are each phase coil of the step motor, 1B is a transistor for current control, 19.20 is a current mirror constant current circuit, 21 is a switching transistor for switching, 22.25, 24.25 is a current value This is a detection resistor.

The operation will be explained. When an ON signal is input from the input signal terminal 1, the driver transistor 6 is turned on, and a voltage is applied to the resistor 22. This voltage becomes the base voltage of the feedback transistor 10, and is balanced in that it becomes the same as the base voltage of the current control transistor 18, so that the collector current of the driver 6 becomes constant. By inputting an ON signal to the input terminal 5, the base voltage of the transistor 18 decreases, and the constant current value decreases. This switching is performed during 1-phase excitation and during 2-phase excitation to perform 1-2 phase drive.

The relationship between torque during 1-phase excitation and 2-phase excitation is as follows: Holding torque during 1-phase excitation is T, and that during 2-phase excitation is T.
2, T2=J'T T.

It becomes. Also, the torque of a step motor is determined by ampere turns. In the present invention, since the drive current is determined by the voltage value at the base of the control transistor 18, the resistance value can be easily set by determining the resistance value so that the switched voltage value has the above relationship.

In the circuit shown in FIG. 1, the emitter sections 10, 11, 12, and 13 are constructed with constant current circuits, but the same effect can be achieved even if they are constructed with resistors.

Effect> Since the present invention has a spider-like structure, the effect is as follows for small signal transistors 1B, 19.20 and 21.
By adding , it becomes possible to freely set and switch the current value. Also, 18 transistors are 10, 11.1211
Since they are in a differential relationship with the base transistors, the current values of all transistors can be controlled by 18 base voltages.

Further, according to the present invention, a constant current circuit capable of switching constant current values can be constructed without performing a circuit binder.

Furthermore, by adding several parts to the conventional constant current circuit, it is possible to switch the constant current, and when driving 1-2 phases,
It is possible to equalize the torque of one-phase excitation and two-phase excitation.

Furthermore, compared to a constant voltage circuit, the present invention eliminates dependence on the power supply, so a stabilized power supply is not required in the power supply circuit, and the price of the power supply circuit can be reduced.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 2 shows a conventional dual power supply voltage circuit, and FIG. 6 shows a conventional chopping type constant current circuit. 1.2, 3.4... Signal input terminals 6.7, 8.
9... Drive transistor 10, 11, 12
．． 13... Feedback transistors 14, 15, 16. ．． 17...Each phase coil 5 of the step motor...Switching signal input terminal 18...Current control transistor 19.20.
...Current mirror constant current circuit 21...
Figure 2: 4m1 group of transistors for switching

Claims (1)

[Claims] A drive transistor connected to each phase coil of the motor, a current value detection resistor placed between the emitter electrode of the drive transistor and ground, and a current value detection resistor connected to the base electrode of the drive transistor and connected to the collector. Electrode force; connected feedback transistor,
a constant current circuit connected to a common connection point of the emitter electrodes of each of the feedback transistors, a control transistor whose emitter electrodes are connected to the common connection point, and the fl;
WE Wh times '16° of a 1-2 phase excitation type step motor characterized by comprising a switching means for switching the base current of a transistor used for IJ.