JPS6125055Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE The present invention relates to a magnetic recording method, and more particularly to a circuit for monitoring a write current during recording.

Conventionally, as this type of write current monitoring circuit, a system as shown in FIG. 1 has been used. In FIG. 1, L1 is a write head, Q1 and Q2 are transistors forming a differential amplifier, R1 and R2 are resistors that determine the write current, and R3 is a resistor for detecting the write current.

In FIG. 2, IN1 and IN2 are input signals that control transistors Q1 and Q2 of the differential amplifier.IL1 is a write current flowing through the write head, and the polarity changes depending on the input signals IN1 and IN2. DET is a voltage generated across the resistor R3, and a constant voltage V is generated whenever either transistor Q1 or Q2 is conductive.

If the lead wire of write head L1 or the coil of write head is disconnected in FIG. 1, the current flowing to transistor Q1 or Q2 decreases, and the voltage DET generated across resistor R3 also decreases as shown in FIG.
It is small as shown.

Therefore, by monitoring the voltage at terminal DET in FIG. 1, it is possible to know whether the write current is flowing normally to the write head.

However, in general, in the method shown in Figure 1, the resistance values of resistors R1 and R2 are set to the resistance value of write head L1 and the resistance value of resistor R3 in order to reduce the influence of fluctuations in the saturation voltage of the transistor and the resistance value of the write head. Since the write current confirmation signal DET in FIG. 2 has a sufficiently large value compared to the resistance value, the difference between the normal voltage V and the abnormal voltage V is not very large. There were problems such as the need for an amplifier between the logic circuit and the logic circuit because the voltage value was small.

The present invention provides a write current monitoring circuit that eliminates the above drawbacks by monitoring the voltage at the connection point between the write head drive circuit and the write head using a circuit that is separate from the existing write head drive circuit. be.

Further, the present invention provides a write current monitoring circuit with a simplified circuit configuration.

According to the present invention, regarding an apparatus for recording information by magnetic recording, in a circuit that drives a write current to a write head using a differential amplifier, the write current is determined by monitoring the voltage of the coil of the write head. A write current monitoring circuit that can check whether the current is flowing normally to the write head is obtained.

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 3, the embodiment of the present invention is a differential amplifier constituted by transistors Q1, Q2 and resistors R1, R2, transistors Q1, Q2
a write head L1 connected to the collector of the transistor Q1, a level shift diode D1 and a light emitting diode D2 connected to the collector of the transistor Q1 and each connected in series, a phototransistor Q3 optically coupled to the light emitting diode D2 and its load. Includes resistor R3.

In FIG. 3, the signals IN1 and IN shown in FIG.
When a signal like that shown in 2 is input, the signal shown in Fig. 3 L
As shown by IL1 in FIG. 4, a write current flows through the write head indicated by 1, the direction of which changes depending on the input signal of the differential amplifier. At this time, the voltage at the collector of transistor Q1 in FIG. 3 becomes as shown by the solid line in FIG. 4 VC1. In the waveform VC1 of FIG. 4, v1 indicates the collector voltage of the transistor Q1 during the period when the transistor Q1 of FIG. 3 is conductive, and v2 indicates the collector voltage of the transistor Q1 during the period when the transistor Q2 is conductive. The level shift diode is such that the collector voltage of transistor Q1 is V of VC1 in Figure 4.
1 or v2, no current flows through the light emitting diode D2, and current flows through the effecting diode D2 only when VC1 reaches a voltage of v2 or higher. Therefore, when the circuit of FIG. 3 is operating normally and transistor Q1 or Q2 is conductive and current is flowing to write head L1, no current flows to light emitting diode D2, so phototransistor Q3 is non-conducting. It becomes conductive and the output terminal DET is at the "1" level as shown by the solid line of the waveform DET in FIG.

In the circuit shown in FIG. 3, when the lead wire between the write head L1 and the transistors Q1 and Q2 or the coil of the write head is disconnected, if the signals shown in FIG. 3 IN1 and IN2 are input to the input terminals IN1 and IN2, As shown by the broken line _VC1 in FIG. 4, the collector voltage of the transistor Q1 in FIG. 3 is higher than that during normal operation, and a current flows through the level shift diode D1 and the light emitting diode D2. When current flows through the light emitting diode D2, the phototransistor Q
3 is in a conductive state, so the 4th terminal is connected to the output terminal DET.
A pulse as shown by the broken line in the waveform DET in the figure is generated.

Therefore, when the circuit shown in FIG. 3 drives a write current to the write head, it can be determined whether the write current is flowing normally by monitoring the waveform of the output terminal DET.

As explained above, the present invention detects a disconnection in the write head circuit by monitoring the coil voltage of the write head in the differential write head drive circuit. This has the advantage that it can be performed using a separate circuit, and the signal level handled by it can be increased.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional write head drive circuit, FIG. 2 is a diagram showing a time chart of the circuit of FIG. 1, FIG. 3 is a diagram showing a write head drive circuit according to the present invention, and FIG. FIG. 4 is a diagram showing a time chart of the circuit of FIG. 3; Q1, Q2...transistor, R1, R2, R
3...Resistor, L1...Write head, D1...Level shift diode, D2...Light emitting diode, Q3...Phototransistor, IN1, IN2...
…Input terminal, DET…Output terminal, VCC…Power supply terminal.

Claims (1)

[Scope of utility model registration request] Two collector load type transistors whose collectors are connected to a common power supply and whose emitters are grounded, a write head coil connected between the collectors of the two transistors, and a voltage at the collectors that exceeds a predetermined value. 1. A write current monitoring circuit comprising: means for detecting that a write current has occurred.