JPH067435B2 - Magnetic bubble memory device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a magnetic bubble memory device, and more particularly to a rotating magnetic field generating current drive circuit used for transferring magnetic bubbles. More specifically, the present invention relates to a drive current waveform. Is related to the drive timing pulse for keeping constant.

[Background of the Invention]

Generally, in a magnetic bubble memory device, in order to transfer a magnetic bubble, it is necessary to apply a magnetic field rotating in the plane of the magnetic thin film in which the magnetic bubble exists (hereinafter referred to as a rotating magnetic field). In order to generate this rotating magnetic field, 90 ° is applied to two sets of rotating magnetic field generating coils (hereinafter referred to as coils) wound orthogonally to each other as shown in FIG. 1a.
A method of flowing sine wave current, triangular wave current or trapezoidal wave current with different phases is used. The case of driving by a triangular wave will be described as an example. An X current I _X as shown in FIG. 1B is passed through the X coil 10 and the Y coil 20 in FIG. 1A at a phase advanced by 90 ° with respect to the Y current I _Y. Then, a rotating magnetic field rotating counterclockwise can be generated.

Usually, the magnetic bubble is not always transferred by the rotating magnetic field, but when the magnetic bubble is not used, the rotating magnetic field may be stopped to stop the magnetic bubble.
In such a case, the magnetic bubble is stopped and then restarted. In the conventional magnetic bubble memory device, the rotating magnetic field driving timing pulse is the same as that in the steady state in this case as well. . However, such a conventional magnetic bubble memory device has a problem that the rotating magnetic field current at the time of restart becomes small and stable operation cannot be obtained.

FIG. 2 shows an example of a triangular wave drive circuit, and FIG. 3 shows the relationship between the input signal pulse and the output waveform to the circuit by the conventional method. First, in order to pass a current in the + direction shown in the coil 5, a + ON signal is input to the coil pre-driver (CPD) 8, and the coiled pre-driver 8 causes the MOSFET 1
And MOSFET2 are output signals required to ON, current MOSFET 1 → coil 5 from the power source _{V R}
→ Flows in the direction of MOSFET 2. The current value flowing at this time increases almost linearly, and the current value I _L is Here, V _R : power supply voltage L: inductance of coil 5 t: time Then, when the + ON signal returns to 0, the coil 5
Due to the inductance of, the current tends to continue to flow, and the energy stored in the coil 5 is released through the parasitic substrate diode of the MOSFET 3 and the MOSFET 4, so that the path of MOSFET 4 (diode) → coil 5 → MOSFET 3 (diode) At, the current flows, and its value gradually decreases until it finally returns to zero. Similarly, in order to pass a current through the coil 5 in the-direction, a -ON signal is input to the coil pre-driver 8.

Here, when the current of the coil 5 is flowing in a steady state, in the stray capacitances Cs ₁ 6 and Cs ₂ 7, the potential and the charge are always constant immediately before the + ON signal and the -ON signal depending on the direction of the current flow. It is in a constant state. However, in the start cycle, the voltage at the coil end becomes a potential determined by the impedance of the circuit (normally 0 potential). In this state, when the rotating magnetic field current is started to flow, the stray capacitances Cs ₁ 6 and Cs ₂ 7 are charged up, so that the current flowing force is weakened and the current of the coil 5 at the start, that is, the rotating magnetic field current is reduced. . That is, in FIG. 3, the peak value I _PS of the rotating magnetic field current at the time of start becomes smaller than the peak value I _P of the rotating magnetic field current at the time of operation in the steady state, and the operation margin at the time of start decreases. There was a point.

[Object of the Invention]

The present invention has been made in order to solve such a conventional problem, and an object of the present invention is to provide a magnetic bubble memory device which is stable and has a wide operation margin, in which the rotating magnetic field generation current waveform is always constant. Especially.

[Outline of Invention]

In order to achieve such an object, the present invention compensates for the decrease in the rotating magnetic field current value at the start due to the stray capacitance of the rotating magnetic field current circuit of the magnetic bubble memory device by the drive timing pulse width to generate the rotating magnetic field. It keeps the current waveform constant.

Example of Invention

 Hereinafter, the present invention will be described in detail based on Examples.

In the triangular wave drive circuit of FIG. 2, as shown in FIG. 4, the waveform of the + ON signal input to the coil pre-driver 8 has a wider pulse width by ΔT than the pulse in the steady state operation only at the start, and the steady state. Since the stray capacitances Cs ₁ 6 and Cs ₂ 7 are charged up during the time ΔT by making the operation pulse whose phase is ΔT earlier than that of the pulse at the time of operation, the rotation thereof at the time of start as well. The peak value of the magnetic field current can be the same as the peak value of the rotating magnetic field current during steady operation.

Here, the increment ΔT of the pulse width of the + ON signal pulse at the start is the stray capacitance values Cs ₁ and Cs ₂ in each rotation example.
Needless to say, it may be appropriately determined in consideration of the above.

As described above, according to the present invention, the operating pulse for the rotating magnetic field generating current circuit for transferring the magnetic bubbles is changed at the start from the pulse width and the timing thereof during the steady operation, so that the rotating magnetic field is changed. The current waveform for generation can be kept constant.

In this embodiment, a MOSFET is used as the switch element of the rotating magnetic field generating current circuit and a triangular wave current is used as the current waveform. However, the present invention is not limited to these, and the switch element is a bipolar transistor (+ reverse current). It is obvious, of course, that the same effects of the present invention can be obtained even if the current waveform is a trapezoidal wave current or a sine wave current.

Further, the compensation of the stray capacitance by the pulse width and the timing is selectively applied to one of the X coil and the Y coil or both the X coil and the Y coil of the rotating magnetic field generating coils according to the purpose and use of the magnetic bubble memory device. You can apply.

〔The invention's effect〕

As described above, according to the magnetic bubble memory device of the present invention, the waveform of the rotating magnetic field generating current can be always constant regardless of whether the rotating magnetic field is generated at the start or during the steady operation. This has the effect of preventing a decrease in the operating margin of the device and widening the stable operating area.

[Brief description of drawings]

1a and 1b are perspective views and main current waveform diagrams of main parts of an X coil and a Y coil used in a magnetic bubble memory device, and FIG. 2 is a main part circuit diagram showing an example of a rotating magnetic field current circuit. FIG. 4 is a diagram showing a conventional rotating magnetic field driving pulse, a rotating magnetic field generating current and a coil end voltage, and FIG. 4 is a diagram showing a rotating magnetic field driving pulse, a rotating magnetic field generating current and a coil end voltage according to the present invention. 1, 2, 3, 4 ... MOSFET, 5 ... Rotating magnetic field generating coil, 6, 7 ... Stray capacitance, 8 ... Coil pre-driver, 10, 20 ... Rotating magnetic field generating coil.

Claims (1)

[Claims] 1. A magnetic bubble memory device comprising a rotating magnetic field generating coil for transferring a magnetic bubble and a current circuit including four MOSFETs for driving the coil in a bridge form. In order to compensate the influence, the leading edge of the drive pulse of the MOSFET is positioned earlier in time when the rotating magnetic field is started than when in the rotating magnetic field steady operation, so that the width of the drive pulse is made wider than that in the rotating magnetic field steady operation. The magnetic bubble memory device is also characterized in that it is widened when the rotating magnetic field is started.