JPS63110994A - Drive system of pulse-motor - Google Patents

Abstract

PURPOSE:To simplify constitution while reducing the noises of a pulse motor by directly controlling a clock applied to the base of a transistor conducting constant-current control by a microprocessor. CONSTITUTION:A first transistor 5 is connected in series with the lower terminal of a winding 6 for a pulse motor. A second transistor 10 is connected in series with the upper terminal of the winding 6. A base drive circuit 4 drives the base of the transistor 5, and a base drive circuit 11 drives the base of the transistor 10. With outputs from a microprocessor 2, a clock CLK1 is input to the base drive circuit 4 through an output port 3, and a clock CLK2 is input to the base drive circuit 11. Constant-current control is performed by the clock CLK2.

Description

[Detailed Description of the Invention] [Summary] A constant current drive type pulse motor in which a second transistor is connected in series to the upper end of the winding of the pulse motor, and a first transistor is connected in series to the lower end of the pulse motor. In the driving method, the microprocessor directly controls the clock applied to the base of the second transistor that performs constant current control.

[Industrial application field]

The present invention relates to an improvement of a constant current drive type pulse motor drive system.

[Conventional technology]

FIG. 5 is a diagram showing an example of a conventional pulse motor drive system. In the figure, 1 is a ROM, 2 is a microprocessor, 3 is an output port, 4 is a base drive circuit, 5 is a transistor, 6 is a winding of a pulse motor, and 7 is a diode. The microprocessor 1 sends the clock CLKI to the transistor 5 through the output port 3.
Send to.

Clock CLKI is amplified by base drive circuit 4 and applied to the base of transistor 5. The transistor 5 is turned on when the clock CLKI goes high, and turns off when the clock CLKI goes low. When the transistor 5 is turned on, current flows through the winding 6, and when the transistor 5 is turned off, current flows through the closed loop formed by the winding 6 and the diode 7. FIG. 6 is a diagram showing the clock CLKI and the winding current in the device of FIG. 5. Although the frequency of the clock CLKI is determined by the speed of the pulse motor, the device of FIG. 5 has the disadvantage that at low speeds the current flowing through the winding vA5 increases and extra torque is generated.

FIG. 7 is a diagram showing the other side of the conventional pulse motor drive system. In the figure, 8 is a current detection resistor, 9 is a comparator, 10 is a transistor, 11 is a base drive circuit, and 12
1 indicates an AND circuit, and 13 indicates a diode. The comparator 9 compares the voltage across the resistor 8 with the reference voltage. ,
When the former is larger than the latter, a low level signal is output.

The output of comparator 9 becomes clock CLK2. The clocks CLKI and CLK2 are input to the AND circuit 12.

The output of the AND circuit 12 is applied to the base of the transistor 100 via the base drive circuit 11. The base drive circuit 11 has an inversion function. transistor 1
When 0 is turned off, current flows through the closed loop consisting of the winding 6, transistor 5, diode 7, etc. When transistor 5 and transistor 10 are both turned off, diode 7
A current flows through the winding 6 and the diode 13, and is returned to the power supply. FIG. 8 is a diagram showing the clock and winding current in the device of FIG. 7. When the clock CLKI rises, the winding current increases rapidly. When the winding current exceeds the set value, the output of the comparator 9 (clock CLK2) becomes a low level, and the output of the AND circuit 12 also becomes a low level (logic O).
become. When the output of the AND circuit 12 becomes logic O, the transistor 10 is turned off and the winding current decreases. When the winding current decreases, comparator 9 outputs a high level, which turns transistor 10 on again. The same operation is repeated below. The device shown in FIG. 7 includes a current detection resistor 8, a comparator 9, and a reference voltage source V. , which has the disadvantage of increasing the cost of the device. Also,
If the frequency of the clock CLK2 is low, the noise of the pulse motor increases, so it is preferable that the frequency of the clock CLK2 is high, but in the device shown in FIG. 7, it is difficult to arbitrarily determine the frequency of the clock CLK2.

[Problem to be solved]

As mentioned above, the conventional device shown in FIG. 5 has the disadvantage that extra torque is generated at low speeds, and the conventional device shown in FIG. 7 has a large physical configuration and a large pulse motor noise. etc., have some drawbacks.

The present invention was created in view of this point, and aims to provide a pulse motor drive system that can reduce the physical configuration and reduce the noise of the pulse motor. There is.

[Means for solving problems]

FIG. 1 is a diagram showing the principle of the present invention. A first transistor 5 is connected in series to the lower end of the winding 6 of the pulse motor, and a second transistor 10 is connected in series to the upper end of the winding 6. Base drive circuit 4 drives the base of transistor 5, and base drive circuit 11 drives the base of transistor 10.

The clock CLKI is inputted to the base drive circuit 4, and the clock CLK2 is inputted to the base drive circuit 11.

Inside the output port 3 there is a latch for the clock CLKI and a latch for the clock CLK2. Microprocessor 2 can write data to these latches. Note that the diodes 7 and 13 are diodes for flyback processing.

〔Example〕

FIG. 2 is a diagram showing the configuration of one embodiment of the present invention.

In the figure, 14 indicates a power supply voltage detection circuit, and 15 indicates an input port. The base drive circuit 11 is connected to the output port 3. The clock CLK2 is turned on/off by turning on/off a predetermined latch (not shown) in the output port 3. The power supply voltage Vcc is input to the power supply voltage detection circuit 14, and the power supply voltage detection circuit 1
The power supply voltage value measured by 4 is set in a predetermined register (not shown) in input port 15. The microprocessor 2 can know the value of the power supply voltage VCC by reading the contents of this register. Third
The figure is a diagram showing the clock and winding current in the device of FIG. 2. When the clock CLKI becomes high level, the transistor 5 is turned on. The clock CLKI maintains a high level state for a time T0, and then goes to a low level. Then, after a predetermined period of time has elapsed, the level becomes high again. Thereafter, the same operation is repeated. Clock CLK2 is clock C
It rises at the same time as LKI, maintains a high level state for T, time, then becomes a low level state, becomes high level again after 12 hours have elapsed, and becomes low level again after T5 hours. Thereafter, the state of T2 and the state of T are repeated. The current {circle around (2)} flowing through the winding 6 becomes as shown in the figure and maintains a substantially constant value.

FIG. 4 is a diagram showing the processing of the microprocessor of FIG. 3. Note that this example assumes that the pulse motor is for driving the print head of a printer. First of all,
Detect the value of power supply voltage.

Next, check whether it is printed in ANK (alphanumeric, kana) or kanji characters. In the case of alphanumeric and kana printing, the on period T is determined according to the power supply voltage from the ANK speed table.

The lower 2 degrees of the off period determines the on period T3. In the case of kanji printing, the ON period T1. The lower 2 degrees of the off period determines the on period T3.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, the seventh
The physical configuration can be made simpler than the conventional example shown in the figure, and the noise of the pulse motor can be reduced. Furthermore, according to the embodiments shown in FIGS. 2 to 4, stable torque can always be generated even if the power supply voltage changes.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle of the present invention, Fig. 2 is a block diagram of one embodiment of the invention, Fig. 3 is a diagram showing the clock and winding current in the embodiment of Fig. 2, and Fig. 4 is a diagram showing the clock and winding current in the embodiment of Fig. 2. Figure 5 is a diagram showing an example of a conventional pulse motor drive system, Figure 6 is a diagram showing the clock and winding current in the device shown in Figure 5, and Figure 7 is a diagram showing the processing of the microprocessor in Figure 5. is the conventional pulse
FIG. 8 is a diagram showing the other side of the motor drive system, and is a diagram showing the clock and winding current in the device of FIG. 7. 1...ROM, 2...Microprocessor, 3...
- Output port, 4... Base drive circuit, 5... Transistor, 6... Pulse motor winding, 7... Diode, 10... Transistor, 11... Base drive circuit, 13 ...Diode, 14...Power supply voltage detection circuit, 15...Input port.

Claims (1)

[Claims] A winding (6) of a pulse motor, a second transistor (10) connected in series to one end of the winding (6), and a second transistor (10) connected in series to the other end of the winding (6). a base drive circuit (11) for driving the base of the first transistor (5), a base drive circuit (11) for driving the base of the second transistor (10), and a base drive circuit (4) for driving the first transistor (5). ), a latch for supplying the clock CLK2 to the base drive circuit (11), and a latch for supplying the clock CLK2 to the base drive circuit (4).
an output port (3) with a latch for providing 1;
A pulse motor drive system characterized by comprising a microprocessor (2) that sets data to an output port (3).