JPH07320209A - Magnetic writing device - Google Patents

Abstract

(57) [Abstract] [Purpose] To make the circuit as simple as possible, operate the switching element stably, and prevent the element from being damaged. [Structure] CMOS type analog switch integrated circuit (IC3
1 or IC 51) is used to form a bridge-shaped network, and the write coil 22 is connected to the bridge-shaped network. Then, the current limiting resistors R ₁₁ and R ₁₂ are connected to the positive power source side and the negative power source side of the bridge network, and CM
Each analog switch is operated within the power supply voltage range of the OS type analog switch integrated circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic writing device, and more particularly, when recording digital information with a magnetic head having a two-terminal single-winding coil, a CMOS type analog switch is used to make a simple structure and four The present invention relates to a technique for preventing a through current that does not pass through a write coil in a switch element.

[0002]

2. Description of the Related Art Conventionally, a photographic film for recording digital information by providing a substantially transparent magnetic layer has been known. As a magnetic writing device for recording digital information on such a photographic film, one using a writing head having a coil with a center tap as shown in FIG. 5 is known.

In the device using the write coil with the center tap shown in FIG. 5, the write circuit can be constructed by a simple circuit. In this circuit, the write current is supplied to the half coil of the write coil 12 (between the center tap 12a and the terminal 12b or between the center tap 12a and the terminal 12c) one by one, so that the current needs to be twice as large as that in the full coil winding. is there. In this circuit, both terminals 12b-1
It is advantageous in that a signal voltage comparable to a full coil can be obtained by reading the signal between 2c. It is to be noted that FIG. 8 shows signal waveforms in each part.

[0004]

By the way, in such a magnetic writing apparatus, since the head structure is rather complicated and the number of lead wires is large, the movement of the magnetic head 1 is restricted when the magnetic head 1 swings. It is disadvantageous in that it may In particular, when such a device is used as a writing / reading device for a film camera with a transparent magnetic layer, the magnetic head and the circuit must be constructed as simple as possible in consideration of the space for accommodating related parts and the cost.

Therefore, in order to make the circuit structure as simple as possible, an apparatus using a two-terminal single-turn coil as shown in FIG. 7 is advantageous. The magnetic writing device is a bridge circuit composed of transistors FT ₁ ～FT ₄ is four switching elements, the write coil 2 of the magnetic head 1
Binary currents in the forward and reverse directions are applied to 2. FIG. 8 shows the signal waveform of each part. In this circuit, since the two-terminal single-turn coil is used, the head structure is simplified.

However, with such a circuit configuration, the drive circuit becomes complicated. Also, transistors FT ₁ and F
If T ₃ , FT ₂ and FT ₄ are turned on at the same time, an excessive shoot-through current may flow, causing the transistors FT ₁ to FT _1- .
The FT ₄ may be damaged. The present invention has been made in view of such conventional problems. The magnetic head is a two-terminal single-winding coil system, and the circuit has a smaller number of parts than those conventionally used, and in the case of emergency. It is an object of the present invention to provide a highly reliable magnetic writing device with less risk of element damage.

[0007]

Therefore, in the magnetic writing apparatus according to the invention of claim 1, the write coil is wound around the magnetic head while the four switch means are connected so as to form a rectangle. Construct a bridge network,
Of the four connection points of the bridge network, both ends of the write coil are connected between two opposing connection points,
A power source is connected between the other two connection points to energize the write coil via the two switch means, and the four switch means are switched based on the information to be recorded to switch the energizing direction of the energizing current of the write coil. In the magnetic writing device, the four switch means are composed of four analog switches built in a CMOS type analog switch integrated circuit using the power supply as a driving power supply.

In the magnetic writing apparatus according to the second aspect of the present invention, the two connection points on the power source connection side of the bridge-shaped circuit network are each connected to the power source via a current limiting resistor. In the magnetic writing device according to the invention of claim 3, the analog switch has a switch-on time from the input of the drive signal to full conduction, and a switch-off time from the stop of the input of the drive signal to the cutoff. It is composed of longer elements.

[0009]

In the magnetic writing apparatus according to the first aspect of the present invention, when, for example, binary information is recorded via the magnetic head, a current of a constant amplitude is generated while switching the direction of direct current supplied from the direct current power source by the switch means. Supply to write head. Further, since the four switch means constituting the bridge-shaped circuit network are constituted by the CMOS type analog switches built in the CMOS type analog switch integrated circuit, the drive circuit can be made to have a simple circuit configuration. Become.

In the magnetic writing apparatus according to the second aspect of the present invention, the two connection points on the power supply connection side of the bridge-shaped circuit network are connected to the power supply via the current limiting resistors, respectively. In the CMOS type analog switch integrated circuit, the analog switch is composed of a semiconductor, and the drive circuit of the semiconductor analog switch is also housed in the same integrated circuit.
The operating voltage of the switch element must be within the range of the positive and negative power supply voltages of the CMOS type analog switch drive circuit,
It is desirable to have a margin of several volts between the positive and negative power supply voltages in order to keep the conduction resistance of the analog switch sufficiently low.

Therefore, by connecting the connection point of the bridge network to the power supply via the current limiting resistor, the switching voltage range of the write coil is narrowed and the CMO
Since there is a margin in the voltage range of the power supply of the drive circuit in the S-type analog switch integrated circuit, the switching voltage can be considered even if the current value of the voltage drop due to the analog switch, the operating temperature, and the variation of the analog switch integrated circuit are taken into consideration. Does not exceed the voltage range of the power supply of the drive circuit in the CMOS type analog switch integrated circuit, and the CMO
The drive circuit in the S-type analog switch integrated circuit can operate with a margin within the voltage range of the power supply. Furthermore, even if a through current flows through the switch element in the bridge, the first and second current limiting resistors prevent the element from being damaged.

In the magnetic writing device according to the third aspect of the present invention, since the analog switch whose switch-on time is longer than the switch-off time is used, a large through-current flows from the DC power supply to the ground without passing through the write coil. Is prevented.

[0013]

Embodiments of the present invention will be described below with reference to FIGS. First, the first embodiment will be described. This is a device configured by using a ready-made or custom-made CMOS analog switch integrated circuit (hereinafter referred to as "IC").

In FIG. 1 showing the first embodiment, a magnetic head 1 is a head for recording digital information on a substantially transparent magnetic layer provided on a photographic film, for example.
The write coil 22 having a two-terminal winding is wound around the magnetic head 1. For the IC 31, for example, a ready-made CMOS type analog switch DG201A is used. This IC31
Includes analog switches 35 to 38, and auxiliary circuits 39 to 42 for driving the analog switches for each analog switch. A signal obtained by inverting the input signal IN by the inverter 43 is input to the auxiliary circuits 40 and 41. When the input signal IN is at the low level (≦ 0.8 V), the analog switches 35 to 38 are turned on (conduction state), and when the input signal IN is at the Hi level (≧ 2.4 V), the analog switches 35 to 38 are turned on. Off (cutoff state)
Becomes These four analog switches 35-38
As shown, they are combined in a bridge shape.

The four analog switches 35 to 38 are selected so that the switch-on time is appropriately later than the switch-off time. Switch-on time means input IN
Is a switching time from when the input is input to when it is completely turned on, and the switch-off time is a switching time from when the input of the input IN is stopped until it is completely turned off.

If the switch-on time is faster than the switch-off time of the switch that has passed the write current Iw ₂₁ until then, the write current Iw ₂₁ has a large penetration from the DC power source to the ground without passing through the write coil 22. It flows as an electric current. Therefore, it is possible to prevent such shoot-through current from flowing by using an analog switch whose switch-on time is appropriately slower than switch-off time.

Incidentally, this CMOS type analog switch DG
In 201A, the switch-on delay time is usually about 480 n.
s, the switch-off time is 370 ns, the analog switches 35 to 38 do not turn on at the same time, and even if the resistance values of the current limiting resistors R ₁₁ and R ₁₂ are small, a large through current flows to the analog switches 35 to 38. Does not flow.

The analog switches 35 to 38 are semiconductor switches, and normal switching operations are expected unless a voltage higher than the voltage range during switching is supplied to the auxiliary circuits 39 to 42 housed in the same IC 31. Can not. Therefore, the voltage supply terminal 31a of the IC 31 is connected to the DC power supply, and one ends of the analog switches 36 and 35 are connected to the DC power supply of the voltage + V _S via the current limiting resistor R ₁₁ . Further, the terminal 31b on the downstream side of the IC 31 is connected to the voltage -V _S.
Of the analog switches 37 and 38 is connected to the negative power source of the voltage −V _S via the current limiting resistor R ₁₂ . Therefore, the resistors R ₁₁ and R ₁₂ , which are the limiting resistors of the write current Iw ₂₁ , are connected to the analog switch 3 as shown in the figure.
5 to 38 and the write coil 22 are connected to the outside, and a voltage 2V _S is supplied to the auxiliary circuits 39 to 42.

That is, with respect to the write current Iw _21, it is usual to provide a series resistance to determine the maximum current so that the relation of I = V _S / R (R = R ₁ + _RH ) can be obtained. In this case, if a series resistance is directly connected to the write coil 22, the switching potentials of the analog switches 35 to 38 become almost the same as the power source potential, and the voltage of the power source supplied to the auxiliary circuits 39 to 42 has no margin.
Extra voltage drop may occur at ~ 38. In addition, this voltage drop is due to the switching current value, operating temperature and I
This often differs due to variations in C31, etc., making it difficult to set the write current Iw ₂₁ accurately.

In the CMOS type analog switch IC, the analog switch is composed of a semiconductor, and the drive circuit of the semiconductor analog switch is also housed in the same integrated circuit. However, the operating voltage of the analog switch is positive or negative of that of the CMOS type analog switch IC. It is necessary to be within the range of the power supply voltage, and it is desirable to have a margin of several volts with respect to the positive and negative power supply voltages in order to keep the conduction resistance of the analog switch sufficiently low.

Therefore, by connecting as shown in FIG. 1, the power supply potential of the auxiliary circuits 39 to 42 is higher than the + side terminal voltage of the analog switches 35 to 38, and the negative power supply side of the auxiliary circuits 39 to 42 is connected. Set the potential to analog switch 35
It can be made lower than the terminal voltage on the − side of −38.
Further, due to the voltage drop of the resistors R ₁₁ and R ₁₂ , the voltage range of the contact circuits of the analog switches 35 to 38 can be made smaller than the power supply voltage of the auxiliary circuits 39 to 42.
Furthermore, if a current limiting resistor is connected in series with the write coil 22 as shown in FIGS. 5 and 7 which are conventional circuit examples, if the four contacts of the analog switches 35 to 38 are simultaneously turned on, an excessive through current flows. Although the IC 31 may be damaged by the current limiting resistor R in the circuit configuration of FIG.
_{Since 11} and R ₁₂ are connected to the power source and the ground side of the analog switches 35 to 38, a through current is prevented from flowing.

Next, the operation will be described. When recording digital binary information on the magnetic layer of a photographic film, the direction of a constant-amplitude current flowing through the write coil 22 is switched between forward and reverse to write on the magnetic layer. FIG. 2 is a timing chart for recording digital binary information by using, for example, a three-part method as a recording method. In the three-part method, the recording information is "1" when the time until the input signal IN falls to the Low level (CLK) and rises to the Hi level is "1" at each cycle T, and when the time is 1 / 3T. It is set to "0".

When the input signal IN (the signal at the point A ₃ ) falls to the low level, the energizing circuit turns the positive power source (voltage + V _S ) →
Resistance R ₁₁ → analog switch 35 → writing coil 22
→ analog switch 38 → resistor R ₁₂ → negative power supply (voltage -V
_S ), and the write current Iw ₂₁ flows through this energizing circuit. The current limiting resistors R ₁₁ and R ₁₂ are connected to the positive power source side and the negative power source side of the bridge circuit network, respectively, and the write current Iw ₂₁ flows through the resistors R ₁₁ and R ₁₂ , so that the write coil 22 has The switching voltage range is narrowed and IC3
There is a margin in the voltage range of the power supply of the drive circuit in No. 1.

Next, the input signal IN rises to Hi level.
When it goes off, the energizing circuit is positive power supply → resistance R ₁₁→ analog switch
C 36 → writing coil 22 → analog switch 37 →
Resistance R₁₂→ Negative power supply energization circuit is formed and write current
Iw_{twenty one}The energizing direction of is reversed. At this time as well,
The voltage fluctuation range of the log switches 37 and 36 is
It will be smaller than the power supply voltage range, and write within this voltage range.
The coil 22 will be switched.

According to this structure, since the bridge-shaped circuit network is constructed by utilizing the CMOS type analog switch integrated circuit, the magnetic writing device can be constructed by a simple circuit, and a commercially available one can be used. Then, the circuit can be constructed at low cost. In addition, the current limiting resistors R ₁₁ and R ₁₂
, Respectively, on the positive power supply side of the bridge circuit network composed of analog switches of the CMOS type analog switch integrated circuit,
Since it is connected to the connection point on the negative power supply side, the switching voltage range of the write coil 22 is narrowed, the voltage range of the power supply of the drive circuit in the IC 31 can be widened, and the current value of the voltage drop by the analog switch can be used. In consideration of temperature and variations in the analog switch integrated circuit, the switching voltage does not exceed the voltage range of the power supply of the drive circuit in the CMOS analog switch integrated circuit. The drive circuit can operate with a margin within the voltage range of the power supply. Further, even if a through current flows through the switch element in the bridge, the current is limited by the resistors R ₁₁ and R ₁₂ , the analog switches 35 to 38 are prevented from being damaged, and the reliability is improved.

Further, the analog switches 35 to 38 do not turn on at the same time because the switch-on time is longer than the switch-off time, so that a large through current from the positive power supply to the negative power supply flows without passing through the write coil 22. Is prevented. Next, a second embodiment will be described. This is a device configured by using an analog switch IC having 2 circuits × 2 contact circuits.

FIG. 3 shows the circuit configuration of the second embodiment, and FIG. 4 shows its signal waveform. IC51 has 2 circuits ×
This is an analog switch IC having a two-contact circuit, and if this IC51 is used, the analog switches 52 and 53 of two circuits × two contacts operate simultaneously by one input signal IN. By bridge-connecting the analog switches 52 and 53, the same function as in the first embodiment can be exerted.

It is desirable to use break-before-make contacts for the analog switches 52 and 53. An analog switch IC with make-before-break contact operation may be used, but current limiting resistors R ₁₁ and R
Depending on the resistance value of _12, a large current may flow instantaneously, which may damage the analog switch IC, which consumes a large amount of current and is economically disadvantageous.

According to such a configuration, even if the apparatus is configured by using another commercially available analog switch IC having a logic configuration of 2 circuits × 2 contacts, the same operation as in the first embodiment can be performed, and the drive circuit Can be made even easier.

[0030]

As described above, in the magnetic writing device according to the first aspect of the present invention, the four switch means forming the bridge circuit network are analog switches built in the CMOS type analog switch integrated circuit. Therefore, the drive circuit can have a simple circuit configuration.

In the magnetic writing device according to the second aspect of the present invention, since the two current limiting resistors are respectively connected to the connection points on the power source side of the bridge circuit network, the switching voltage range of the write coil is the CMOS type analog. It becomes narrower than the voltage range of the drive power supply of the switch integrated circuit. Therefore, there is a margin in the voltage range of the power supply of the drive circuit in the analog switch integrated circuit, and the switching voltage can be kept within the voltage range of the power supply of the drive circuit in the analog switch integrated circuit. Further, there is little risk of element damage and the reliability is improved.

In the magnetic writing apparatus according to the third aspect of the present invention, since the switch element having the switch-on time longer than the switch-off time is used, a large through-current flows from the DC power supply to the ground without passing through the write coil. Can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment according to the present invention.

FIG. 2 is a timing chart of FIG.

FIG. 3 is a circuit diagram of a second embodiment according to the present invention.

FIG. 4 is a timing chart of FIG.

FIG. 5 is a circuit diagram when a conventional coil with a center tap is used.

6 is a timing chart of FIG.

FIG. 7 is a circuit diagram when a conventional two-terminal single-turn coil is used.

8 is a timing chart of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Magnetic head 22 Writing coil (2-terminal single-turn coil) 31,51 CMOS type analog switch integrated circuit (I
C) R ₁₁ , R ₁₂ current limiting resistor

Claims (3)

[Claims] 1. A winding coil is wound around a magnetic head, and four switch means are connected to form a rectangle to form a bridge-shaped network, and four connection points of the bridge-shaped network are formed. Of the two, the both ends of the write coil are connected between two opposing connection points, the power source is connected between the other two connection points, the write coil is energized via two switch means, and information to be recorded. In the magnetic writing device for switching the direction of the energization current of the write coil by switching the four switch means based on the above, the four switch means are built in a CMOS type analog switch integrated circuit using the power source as a driving power source. A magnetic writing device characterized by being composed of two analog switches. 2. The magnetic writing according to claim 1, wherein the two connection points on the power supply connection side of the bridge-shaped network are respectively connected to the power supply via current limiting resistors. apparatus. 3. The analog switch is constituted by an element in which a switch-on time from the input of a drive signal to full conduction is longer than a switch-off time from the stop of input of a drive signal to the cutoff thereof. The magnetic writing device according to claim 1, wherein the magnetic writing device is a magnetic writing device.