JPH0356097A - Driving circuit for stepper motor - Google Patents

Abstract

PURPOSE:To obtain a driving method which utilizes torque effectively, is heard to step out, and provides a short settling time by controlling a stepper motor so as to change its torque characteristic according to its rotation angle. CONSTITUTION:A direction signal (f) indicating the rotating direction of a stepper motor 5 and step pulses (g) are inputted into a state storing circuit 2. Outputs (a), (b) from encoders (A), (B) mounted on the stepper motor 5 are inputted into a state storing circuit 1. The outputs from the state storing circuits 1, 2 are decoded by a decode circuit 3 and signals PH11-PH41 drive the windings L1, L2 of the stepper motor 5 via a stepper motor driving circuit 4 comprising an H type bridge. By such arrangement, high efficiency control provided with four input step pulses (g) is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a stepping motor drive circuit for moving a magnetic head, etc. of a flexible disk device. (Prior Art) Flexible disk devices are widely used as external storage devices for personal computers and the like because they are small and inexpensive. This flexible disk device consists of a flexible disk having a predetermined number of tracks, a magnetic head, and the like. Data is then recorded on tracks on the flexible disk via this magnetic head.

Therefore, a drive mechanism is provided to move this magnetic head to each track. Such a drive mechanism generally includes a stepping motor that has n sets (phases) of windings and rotates by a predetermined angle (step angle) when one of the windings is energized, and an input step pulse. It consists of a drive circuit that switches the current flowing through each winding of the stepping motor based on a signal, and a lead screw that moves the magnetic head horizontally when the stepping motor rotates. When the step pulse signal is input, this drive circuit sequentially switches the excitation phase of the stepping motor. (Problem to be Solved by the Invention) As described above, the stepping motor drive circuit of a conventional flexible disk device simply switches the excitation phase of the stepping motor sequentially when a step pulse signal is input. Therefore, since 100% of the stepping motor's torque is not utilized, there is a high probability that the stepping motor will step out when it starts rotating. Also, since the stepping motor does not have a special Brake II arm when the motor stops operating, it takes a long time to settle. As described above, the conventional stepping motor drive circuit has problems to be solved.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a stepping motor drive circuit for a flexible disk device, etc., which can reduce the probability of step-out of the stepping motor and shorten the settling time. It's about doing. (Means for Solving the Problems) In order to achieve the above object, the stepping motor drive circuit of the present invention includes a state memory circuit that counts input step pulses and stores the counted value, and a state memory circuit that counts input step pulses and stores the counted value. In a stepping motor drive circuit comprising a decoder that decodes stored count values and a driver circuit that excites each phase of the stepping motor based on the decoded output of the decoder, the stepping motor is at a stop position. a first encoder that detects that the stepper/gumometer has rotated by a step angle and has reached approximately the midpoint of the step angle; a first storage element that holds one state while the last signal is output by the second encoder; a second storage element that holds one state when a signal is output, the first storage element holds one state, and holds the other state when a signal is output from the second encoder; , a first monostable circuit that outputs a pulse signal with a predetermined pulse width when the first storage element holds the other state and the second storage element holds one state; a reset circuit that detects a fall of the predetermined pulse signal outputted by the monostable circuit and sets the second storage element to the other state, and the decoder is stored in the state storage circuit. Decoding is performed based on the count value and the states of the first and second storage elements. (Example) Next, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of an embodiment of the present invention. In the figure, 1.2 is a state memory circuit, 3 is a decoder that decodes the output signal of the state memory circuit 1.2, 4 is a stepping motor driver circuit, 5 is a stepping motor, and A is a state memory circuit in which the stepping motor is operated in either direction. Encoder B outputs a signal when the stepping motor rotates and reaches approximately the midpoint of the step angle.B is an encoder that outputs a signal when the stepping motor reaches a predetermined stop (rest) position. The state memory circuit 2 is
Flip-flops FF3, FF4, inverter G2, and exclusive OR (referred to as EXOR gate) GIO, G13
It consists of The state storage circuit 1 is composed of flip-flops FFI, FF2, AND gates G5 to G9, G14, OR gate GIO, and a monostable circuit 20.21 that outputs a pulse signal of a predetermined pulse width when a signal is input. The stepping motor driver circuit 4 has a circuit structure called a so-called I-type bridge in order to operate the stepping motor 5 reversibly. The direction signal f specifies the rotation direction of the stabbing motor 5.

FIG. 2 is an explanatory diagram of the operation of the circuit diagram of FIG. 1.

Figure 3 shows the truth value of decoder 3. In addition, in the same figure, the "L" level is r O J and "T I"
The level is expressed as "1". Next, the operation when four step pulse signals g are input in the circuit diagram of FIG. 1 will be described. Here, in the initial state, the output signals QO to Q3 of the flip-flops FFI to FF4 are
is L level, and the direction signal f (JL level. Therefore, the input terminals dO to d4 of the decoder 3 are all "
Since a signal of "L" level is input, PHi 1 (i=1 to 4) becomes "H" as shown in FIG. r L J
, r L J , r}{j. Based on these output signals, the stepping motor driver circuit 4 causes current to flow through the windings Ll and L2 of the stepping motor 5 in the directions of arrows el and e2, for example. As a result, the torque characteristics of the stepping motor 5 are as shown in FIG.
Becomes PHA.

In such a state, when the step pulse g is input, it is inverted by the inverter G2 and the flip-flop F
It is input to F3, FF4 and AND gates G5, G9.

As a result, the signal QO of flip-flop FF4 is rl,
Changes from J level to rH level. In addition, all the input terminals of the AND gate G5 are input with rH, level signals, and the AND gate G5 outputs rH, level signals, so the signal Q2 of the flip-flop FFI is also rH.
Changes from l, J level to r H J level. Therefore, dO to d4 of decoder 3 is 1 to rL), rL'', r
Since signals of H,,'LJ+rl, level are input, PH21 changes to r}{J level and PH41 changes to 'LJ level. Based on this PHil signal, the stepping motor driver circuit 4 changes to step Current is passed through the windings Ll and L2 of the stepping motor 5 in the directions of arrows el and e4.As a result, the torque characteristic of the stepping motor becomes PHB, and the stepping motor 5 starts rotating in a predetermined direction. , when the step angle reaches approximately the midpoint, encoder A detects this and adds signal a to AND date G8.

At this time, an H level signal is input to the other input terminal of AND gate G8, and AND gate G8 outputs a Tr level signal, so signal Q3 of flip-flop FF2 changes from L level to H level. do. As a result, the level of the input terminals dO to d4 of the decoder 4 is
L soh' L J, rH JrHJ, rLJ
, r} [becomes J. Therefore, the torque characteristic of the stepping motor 5 becomes PHC, and the maximum available torque is maintained.

If the step pulse g is input again before the stepping motor 5 rotates the step angle, the following operation is performed. The signal QO of flip-flop FF4 changes from H level to L level. Since the signal Q1 at the L level is input to one input terminal of the EXOR gate G13, and the signal QO at the {■ level} is input to the other input terminal,
EXOR gate G13 outputs H level. EXOR
This}I level signal is input to one input terminal of the gate G10, and the level direxin signal f is input to the other input terminal, so the EXOR gate GIO
} Input the level signal to the D terminal of the 7 flip-flop FF3. Therefore, when the step pulse g is input to the flip-flop 1FF3, the signal Q1 of the flip-flop FF3 changes from L level to H level. In addition, an inverter G is connected to the first to third human power terminals of the AND game G9.
Since the H-level step pulse g inverted at step 2, the H-level signal Q2, and the H-level signal Q3 are input, an H-level signal is output. This H level signal is passed through the flip-flop F via the OR gate G10.
Since it is input to the RR child of F2, the flip-flop FF
2 signal Q3 changes from H level to L level. When the stepping motor 5 rotates through a step angle, the encoder B outputs a signal b. At this time, the signal Q3 of the flip-flop FF2 has changed to the L level, so signals of the H level, H level, and L level are input to the first to third input terminals of the AND gate G6, so that the flip-flop FF1 remains unchanged. As a result, the input terminals do to d4 of the decoder 3 have r1,,,rl
,,rH"rH",'L" can be manually created, so
PH11 outputs rL'', NI'', rH'', and rL'', respectively. The stepping motor driver circuit 4 is
Based on these signals, the stepping motor 5 is driven so that the torque characteristic PHC is achieved. This operation is performed by stepping pulse f, encoder A
This is done every time signal a of encoder B and signal b of encoder B are input. That is, when the second signal a is output from the encoder A, the torque characteristic of the stepping motor 5 changes from PHC to PHD, and when the third signal a is output, the torque characteristic of the stepping motor 5 changes from PHC to PHD.
Changes from D to P }t A.

Then, when the fourth step pulse g is input, the signal Q3 of the flip-flop 1FF2, the signal Q3 of the flip-flop 1FF2,
Signal Q1 of F3 and QO of flip-flop FF4 each change from H level to L level. At this time, the stepping motor 5 continues to rotate with the torque characteristic PHA. Then, when the step angle reaches the midpoint, the encoder A outputs the signal a, so the signal Q2 of the flip-flop FF3 changes from the L level to the H level. Therefore, the stepping motor 5 continues to rotate with the torque characteristic PHB. Then, when the stepping motor 5 rotates by the step angle, the encoder B outputs a signal b indicating that it has rotated by the step angle. As a result, the flip-flop 1FF
Q2 of I changes from H level to L level. Therefore, the input terminals do to d4 of the decoder 3 have rL'', rH
'', rL'', 'LJ+ rl, J can be manually generated, so PHL1 is rL'', rl,'', r}{'', r}
{'' is output respectively. The stepping motor driver circuit 4 controls the stepping motor 5 with torque characteristics P H
D, that is, rotate in the opposite direction. In parallel with this operation, H level output signals Q2 and Q3 are input to the AND gate G14, so that a }I level signal is output. When the monostable circuit 20 outputs a pulse signal d with a predetermined pulse width in synchronization with the rise of this signal, the monostable circuit i%
21 outputs a pulse e in synchronization with the falling edge of this pulse signal d. This pulse e resets the flip-flop FF2, and the signal Q3 becomes L level. Therefore, the stepping motor 5 rotates in the opposite direction for a period of time equal to the pulse width of the pulse signal d of the monostable circuit 20.
D and the brakes are applied, which speeds up the settling time. After this operation is completed, the system returns to its initial state, so
The stepping motor 5 is controlled to have the torque characteristic PHA and maintains the current position. Therefore, the stepping motor 5 remains stationary at a stable point. (Effects of the Invention) As explained above, according to the stepping motor drive circuit of the present invention, the torque of the stepping motor can be used effectively. Therefore, even with high-speed step pulses, it is possible to prevent step-out and shorten the settling time.

[Brief explanation of drawings]

1 is a diagram showing the configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the embodiment of FIG. 1, and FIG. 3 is a diagram showing the truth value of the decoder 3. 1.2... State memory circuit, 3... Decoder, 4... Stepping motor driver circuit, 5... Stepping motor, 20.21
...monostable circuit, A, B...encoder, FF1~
FF4...flipflop.

Claims (1)

[Claims] A state memory circuit that counts input step pulses and stores the counted value; a decoder that decodes the counted value stored in the state memory circuit; A stepping motor drive circuit that includes a driver circuit that excites each phase of the stepping motor, and a first encoder that detects that the stepping motor is at a stop position; and a first encoder that detects that the stepping motor is at a stop position; a second encoder that detects that the step angle has almost reached the midpoint, and maintains one state from when the first step pulse is input until the last signal is output by the second encoder; a first storage element that holds one state and holds one state when a signal is output by the first encoder; a second storage element that holds one state and holds the other state when a signal is output from the second encoder; a first monostable circuit that outputs a pulse signal with a predetermined pulse width; and a fall of the predetermined pulse signal outputted by the first monostable circuit is detected and and a reset circuit that sets the second storage element to the other state, and the decoder performs decoding based on the count value stored in the state storage circuit and the states of the first and second storage elements. Stepping motor drive circuit.