JP4171158B2 - Supply method of write current - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for supplying a write current in a magnetic recording apparatus. More specifically, the present invention relates to a write current supply method in a magnetic recording apparatus used for a high coercive force card that requires a larger write current than a low coercive force card.
[0002]
[Prior art]
Conventionally, the recording magnetic head such as a card reader, the current for writing (hereinafter, referred to herein as the write current) As a method of supplying, for example, those using the circuit shown in FIGS. 9 to 11 .
[0003]
A circuit 101 shown in FIG. 9 includes a coil 102 constituting a magnetic head, a power supply 103 having a single voltage for supplying power, a switching element 104 such as a transistor for switching the direction of the write current Iw, and a switching element 104. And a constant current source 106. In this circuit 101, a constant write current Iw set by a constant current source 106 is supplied , and each switching element 104 is appropriately turned on / off by a gate 105 in accordance with predetermined recording information. A magnetic field is generated to record information on a recording medium such as a magnetic card.
[0004]
In the circuit 111 shown in FIG. 10, the write current Iw is set and supplied not by the constant current source 106 but by the current limiting resistor 107.
[0005]
In addition, as in the circuit 112 shown in FIG. 11, there is a circuit in which the write current Iw is set by the current control resistor 107 and four switching elements 104 are provided to constitute an inverter circuit. In this circuit 112, according to predetermined recording information, the four switching elements 104 are appropriately turned on / off to supply the write current Iw to the coil 102 of the magnetic head.
[0006]
[Problems to be solved by the invention]
However, in a card reader compatible with a Hi-Co card, ie, a high coercive force card, which requires a larger write current than a Lo-Co card, that is, a low coercive force card, the gap between the magnetic heads is greatly increased due to the high coercivity of the card. However, the conventional write current supply method has the following problems.
[0007]
First, when the number of windings of the coil 102 is increased in order to generate a large amount of magnetic flux, there is a problem that the inductance increases and the rise of the write current Iw is delayed. On the other hand, when the voltage to be supplied is increased in order to increase the rise of the write current Iw, there is a problem that the power loss of the circuit increases and the circuit heat is generated or the allowable power consumption of the device is exceeded. On the other hand, if the number of windings of the coil 102 is suppressed, it is necessary to flow a large write current in order to generate a large magnetic flux, and there is a problem that the power loss increases.
[0008]
Here, as shown in FIGS. 12 and 13, by using the power supply voltage switching means, the power supply voltage is increased only for a certain time T1 when the write current Iw starts to flow, so that the rise of the write current Iw is accelerated. A method of switching to a lower power supply voltage and suppressing power consumption can be considered. However, in practice, since the impedance fluctuates due to production variations and characteristics of the magnetic head or the like, or a temperature change depending on the usage environment, it is difficult to switch the power supply voltage properly with this method. For example, as shown in FIG. 12, when the impedance is larger than that assumed, the switching timing of the power supply voltage is too early, and the write current Iw is raised by a low voltage, resulting in a long rise time. On the other hand, as shown in FIG. 13, if the impedance is smaller than the expected one, the switching timing of the power supply voltage is too late, and a high voltage is applied to the circuit. Problems occur.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide a stable write current supply method that suppresses circuit power loss and has a fast rise time.
[0010]
[Means for Solving the Problems]
In order to achieve this object, the invention described in claim 1 flows to the drive circuit of the magnetic head of the magnetic recording apparatus used in the high coercive force card that requires a larger write current than the low coercive force card, and responds to the recorded information. A write current supply method in which a rise occurs when the current direction is switched by turning on and off a transistor switch incorporated in the drive circuit, and the write current to the high coercive force card is the target current of the write current. In addition , the write current flowing in the drive circuit is passed through the constant current circuit so that the drop voltage suddenly rises when the write current starts to reach the target current value, and the write current and the write current reach the target current value. The voltage drop when the write current rises based on the relationship with the voltage drop that suddenly increases when starting By switching the power supply voltage that supplies power to the drive circuit when it becomes higher than the reference voltage, the write current is supplied to the coil of the magnetic head with a high power supply voltage only during the rising period of the write current and with a low power supply voltage outside the rising period. I am trying to supply.
[0011]
Therefore, the write current rises quickly by supplying a high power supply voltage during the rise period of the write current, while the write current rises sufficiently by detecting the voltage of the current detection circuit that changes in response to the rise of the write current. By detecting the voltage of the current detection circuit corresponding to the state, it is possible to switch to a low power supply voltage at an optimal timing, and to stabilize the write current to the set target value outside the write current rising period.
[0012]
The write current to the high coercive force card is set as the target current value of the write current, and the write current is written based on the relationship between the write current and the drop voltage that rapidly increases when the write current starts to reach the target current value. The voltage drop when the current rises is used as a reference voltage, and the power supply voltage that supplies power to the drive circuit is switched when the voltage drop becomes higher than the reference voltage .
[0013]
Therefore, by setting the target value of the predetermined write current without providing the current limiting resistor or the like, it is possible to launch the write current to quickly, the constant current circuit changes in accordance with the rise of the write current by detecting the drop voltage, it is possible to switch the power supply voltage to supply the write current at the optimum timing.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.
[0015]
FIG. 1 shows a circuit to which the write current supply method of the present invention is applied. This circuit 1 constitutes a drive circuit for a magnetic head for writing in a magnetic recording apparatus used for a Hi-Co card, ie, a high coercive force card, which requires a larger write current than a Lo-Co card, ie, a low coercive force card. The coil 2 constituting the magnetic head, the switching element 4 for switching the direction of the write current Iw, the gate 5 for controlling the switching element 4, the power supply means 6 capable of switching the power supply voltage, and the current detection circuit 7 Composed in combination. Then, by detecting the voltage V1 of the current detection circuit 7, detecting that the write current Iw has risen, and switching the power supply voltage at that timing, the rise period of the power supply voltage Vb is high only during the rise period of the write current Iw. Outside, the write current Iw is supplied with a low power supply voltage Va.
[0016]
Further, the circuit 1 of the present embodiment combines the constant current circuit 8 with the current detection circuit 7, and the current detection circuit 7 detects the drop voltage V1 of the constant current circuit 8 and detects that the write current Iw has risen. Like to do. The constant current circuit 8 is configured such that the write current Iw flowing through the circuit 1 has a set constant value, and in FIG. Hereinafter, in this embodiment, it is simply referred to as a constant current source 8.
[0017]
The power supply means 6 in this embodiment includes a high power supply voltage Vb and a low power supply voltage Va as power supply voltages, and the high power supply voltage Vb is connected to the circuit 1 via the transistor switch 9 so as to be turned on and off, and is low. The power supply voltage Va is connected to the circuit 1 via the diode 10. With this configuration, when the transistor switch 9 is on, power is supplied to the circuit 1 by the high power supply voltage Vb, and during this time, the low power supply voltage Va is partitioned by the diode 10 and power is not supplied. On the other hand, when the transistor switch 9 is turned off, the power supply by the high power supply voltage Vb is cut off, and the power supply by the low power supply voltage Va is started.
[0018]
Here, in order to suppress the power loss of the circuit 1, it is desirable that the power supply voltage be as low as possible. For this reason, the low power supply voltage Va is set as low as possible so that sufficient power can be supplied to the circuit when the write current Iw reaches a constant target current value I ′ by the constant current source 8. On the other hand, the high power supply voltage Vb is a minimum high voltage that can raise the write current Iw sufficiently quickly.
[0019]
The current detection circuit 7 includes a reference voltage V1 ′ and a comparator 11, and is connected between the constant current source 8 and the transistor switch 9. The comparator 11 compares the input drop voltage V1 with the reference voltage V1 ′, and outputs a Low signal when the drop voltage V1 is smaller than the reference voltage V1 ′. Thereby, the transistor switch 9 is turned on. On the other hand, when the drop voltage V1 is larger than the reference voltage V1 ′, the comparator 11 outputs a Hi signal. Thereby, the transistor switch 9 is turned off.
[0020]
Next, a method for detecting the rise of the write current Iw and switching the power supply voltage will be described.
[0021]
FIG. 2 shows the relationship between the write current Iw and the voltage drop V1 of the constant current source 8. The horizontal axis T represents the time axis.
[0022]
As shown in FIG. 2A, the write current Iw rises toward the target current value I ′ set by the constant current source 8 when a predetermined power supply voltage is supplied to the circuit 1. On the other hand, as shown in FIG. 2B, the drop voltage V1 of the constant current source 8 is almost short-circuited, that is, the drop voltage V1 is low until the write current Iw reaches the target current value I ′. . Then, the voltage drop starts abruptly when the write current Iw starts to reach the target current value I ′, and the drop voltage V1 rises. Eventually, when the write current Iw reaches the target current value I ′, the drop voltage V1 converges to the drop voltage V1 ″ corresponding to the target current value I ′.
[0023]
That is, the period during which the drop voltage V1 is low corresponds to the rising period of the write current Iw. On the other hand, when the voltage drop starts and the drop voltage V1 starts rising from a low state, the write current Iw is sufficiently rising. I can judge. Accordingly, by switching the power supply voltage at the timing when the drop voltage V1 of the constant current source 8 changes, the write current Iw is supplied with the high power supply voltage Vb during the rising period of the write current Iw and with the low power supply voltage Va after the rising period. It becomes possible to do. The reference voltage V1 ′ of the current detection circuit 7 of the present embodiment sets the value of the drop voltage V1 in a state where the write current Iw sufficiently rises from the relationship between the write current Iw and the drop voltage V1 (FIG. 2). (B)).
[0024]
In the circuit 1 configured as described above, according to the write current supply method of the present invention, a stable write current Iw is rapidly supplied as follows.
[0025]
First, the high power supply voltage Vb is supplied to the circuit 1 (step 1 in FIG. 6), and thereby the write current Iw starts to rise. Until the write current Iw rises sufficiently, the drop voltage V1 of the constant current source is almost short-circuited and is lower than the reference voltage V1 ′ (step 2; No). As a result, the output of the comparator 11 is Low (Step 3, Step 5; Yes), the transistor switch 9 is kept on (Step 6), and power is continuously supplied to the circuit 1 by the high power supply voltage Vb. During this time, the low power supply voltage Va is partitioned by the diode 10 and does not supply power. Here, since the high power supply voltage Vb is set so that the write current Iw can be raised sufficiently quickly, the write current Iw quickly rises toward the target value current value I ′. When the write current Iw rises sufficiently, the voltage drop of the drop voltage V1 starts abruptly. For this reason, the drop voltage V1 becomes higher than the reference voltage V1 ′ (step 2; Yes). As a result, the output of the comparator 11 becomes Hi (step 4), and the transistor switch 9 is turned off (step 7). Thereby, the power supply by the high power supply voltage Vb is cut off (step 7), and the power supply by the low power supply voltage Va is started (step 8). The write current Iw that sufficiently rises and approaches the target current value I ′ reaches the target current value I ′ smoothly and stably by the low power supply voltage Va.
[0026]
FIG. 3 shows the rising state of the write current Iw along the time axis T. 4 shows how the write current Iw rises due to the high power supply voltage Vb, and FIG. 5 shows how the write current Iw rises due to the low power supply voltage Va. In the figure, T1 indicates the time when the voltage is switched.
[0027]
Thus, the rising period is a high supply voltage Vb of the write current Iw, the low power supply voltage Va is in a stable period of the write current Iw, so as to supply the write current Iw, consumption of the device while suppressing power loss of the circuit It is possible to reduce the power and supply the write current Iw that is fast and stable.
[0028]
Further, in the method for supplying the write current Iw according to the present invention, the power supply voltage is not switched in a fixed time, but the voltage drop is detected as described above, and the feedback for judging the power supply voltage switching timing is provided. The power supply voltage is switched at an optimal timing according to the rise of the write current Iw. Therefore, the switching timing is too early and the rise time of the write current Iw becomes long or the switching timing is delayed due to variations in production characteristics and characteristics of the magnetic head, etc., or fluctuations in impedance due to temperature changes depending on the usage environment. Thus, problems such as power loss of the circuit 1 and generation of noise can be avoided. That is, it is possible to optimize the power supply voltage switching timing (T1 in FIG. 3) in order to suppress the power loss of the circuit 1 and speed up the rise of the write current Iw.
[0029]
The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention.
[0030]
For example, as shown in FIG. 7, assuming that the target current value of the write current Iw is set by the damping and current limiting resistor 12, the drop voltage V2 is detected and the rise of the write current Iw is detected. Also good. However, in this case, since the resistor 12 is connected, the rise is delayed as compared with the case where the constant current source 8 is used.
[0031]
Further, as shown in FIG. 8, the control voltage V3 of the constant current circuit 8 may be detected to detect that the write current Iw has risen.
[0032]
【The invention's effect】
As apparent from the foregoing description, in the method of supplying the write current of the present invention, the rise time of the La site currents up quickly up the write current by supplying a high power supply voltage, whereas in response to the rise of the write current By detecting the voltage of the current detection circuit that changes and detecting the voltage of the current detection circuit corresponding to the state in which the write current has risen sufficiently, the power supply voltage is switched to a lower power supply at the optimal timing, and the write current is outside the rising period. Then, the write current can be stabilized at the set target value. As a result, even in a magnetic head with a large inductance corresponding to a high coercive force card, power consumption is suppressed, and the write current rise time is shortened with a minimum required power, and a stable write current is obtained. Can supply.
[0033]
Further, by setting the target value of the predetermined write current without providing the current limiting resistor or the like, it is possible to launch the write current to quickly. Further, by detecting the drop voltage of the constant current circuit changes in accordance with the rise of the write current can switch the power supply voltage to supply the write current at the optimum timing.
[Brief description of the drawings]
FIG. 1 is a schematic circuit diagram showing an example of a circuit to which a write current supply method of the present invention is applied.
2A and 2B are diagrams showing a relationship between a write current and a voltage drop of a constant current source in the same circuit, where FIG. 2A shows a change in write current along a time axis T, and FIG. 2B shows a change in voltage drop. Is shown along the time axis T.
FIG. 3 is a diagram showing a rising state of a write current in the circuit along a time axis T.
FIG. 4 is a diagram showing a rising state of a write current supplied by a high power supply voltage along the time axis T in the same circuit.
FIG. 5 is a diagram showing a rising state of a write current supplied by a low power supply voltage along the time axis T in the circuit.
FIG. 6 is a flowchart showing a method of switching from a high power supply voltage to a low power supply voltage in the circuit.
FIG. 7 is a schematic circuit diagram showing another example to which the write current supply method of the present invention is applied, and showing an example using a current limiting resistor.
FIG. 8 is a schematic circuit diagram showing another example to which the write current supply method of the present invention is applied, and showing an example of detecting a control voltage of a constant current circuit.
FIG. 9 is a diagram illustrating an example of a circuit using a conventional write current supply method.
FIG. 10 is a diagram showing another circuit using a conventional write current supply method;
FIG. 11 is a diagram showing another circuit using a conventional write current supply method;
FIG. 12 is a diagram illustrating a state in which a write current rises when a power supply voltage is switched over a certain period of time and a state in which switching timing is early.
FIG. 13 is a diagram illustrating a state in which a write current rises when a power supply voltage is switched for a predetermined time, and a state in which the switching timing is late.
[Explanation of symbols]
7 Current detection circuit 8 Constant current source (constant current circuit)
Iw Write current Vb High power supply voltage Va Low power supply voltage

Claims (1)

It flows to the drive circuit of the magnetic head of the magnetic recording device used for the high coercive force card that requires a larger write current than the low coercive force card, and the transistor switch incorporated in the drive circuit is turned on / off according to the recorded information The write current supply method in which rising occurs when the direction of the current is switched, wherein the write current to the high coercive force card is set as the target current value of the write current and the current flowing to the drive circuit A write current is passed through a constant current circuit so that the drop voltage suddenly increases when the write current starts to reach the target current value, and suddenly when the write current and the write current start to reach the target current value. the voltage drop in a state in which the write current rises to the reference voltage based on the relationship between the drop voltage rises, By switching the power supply voltage that supplies power to the drive circuit when the drop voltage becomes higher than the reference voltage, the power supply voltage is high only during the rising period of the write current, and the power supply voltage is low outside the rising period. A write current supply method characterized in that the write current is supplied to a coil of a magnetic head.

Images