JPH0652003U - Magnetic reproduction circuit - Google Patents

Abstract

(57) [Abstract] [Objective] The present invention is a highly accurate and extremely reliable magnetic reproduction which can prevent the destruction of card data at the time of data rewriting by simply adding it to the magnetic reproduction circuit of the F2F system. The purpose is to provide a circuit. The magnetic reproducing circuit of the present invention includes a differential amplifier circuit 2 for amplifying a signal reproduced by the magnetic head 1, and a rectangular wave signal obtained by inverting the output signal at the peak point of the amplified signal a of the differential amplifier circuit 2. c peak detection circuit 3 and differential amplifier circuit 2
And a reference voltage circuit 4 that supplies a reference voltage b to the peak detection circuit 3, an F2F demodulation circuit 5 that receives the rectangular wave signal c of the peak detection circuit 3 and modulates the frequency, and a comparison between the amplified signal a and the comparison voltage g. A signal comparator 7 that outputs a signal at a change point of the rectangular wave signal c, detects a magnetic signal level abnormality, and an output level detection circuit 6 including a flip-flop 8 are provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a magnetic reproducing circuit used in an electric magnetic card reader / writer or the like.

[0002]

[Prior art]

 In recent years, prepaid cards have rapidly spread in the distribution industry, and there is a demand for a high-precision card reader / writer that performs arithmetic processing on the read data and records it again as new data. Circuits are being developed and researched.

A conventional magnetic reproducing circuit will be described below. FIG. 4 is a block diagram of a conventional magnetic reproducing circuit. In FIG. 4, 1 is a magnetic head for converting the voltage of the signal recorded on the magnetic card, 2 is a differential amplifier circuit for amplifying the signal reproduced by the magnetic head 1, and 3 is the output signal inverted at the peak point. , A peak detection circuit having a rectangular wave signal, 4 a reference voltage circuit for supplying a reference voltage to the differential amplifier circuit 2 and the peak detection circuit 3, and 5 an F2F demodulation circuit for demodulating data.

The operation of the magnetic reproducing circuit configured as described above will be described below. FIG. 5 is a waveform diagram showing the operation of the conventional magnetic reproducing circuit. 4 and 5, the signal recorded on the magnetic card is voltage-converted by the magnetic head 1 to obtain the amplified signal a of the differential amplifier circuit 2 biased to the reference voltage b generated by the reference voltage circuit 4. The amplified signal a is input to the peak detection circuit 3 to obtain a square wave signal c whose output is inverted at the peak point of the amplified signal a. This rectangular wave signal c is a frequency-modulated (F2F-modulated) signal, which is digitally processed by the F2F demodulation circuit 5 and is output at a bit delimiter between the card running signal d that is at a low level during the magnetic signal input period. A clock signal (clock pulse for sampling demodulated data) e and a read data signal (demodulated data) f indicating the data of the bit are obtained.

Next, a method of processing a prepaid card for a card reader / writer incorporating the above conventional magnetic reproducing circuit will be described.

FIG. 6 is a flow chart at the time of card processing of a card reader / writer using a conventional magnetic reproducing circuit. In FIG. 6, the card is taken in, the card data is read by the magnetic head 1 (S51), if the data is normal (S52), data processing is performed (S53), the data is rewritten (S56), and the data is read. (S57) If the data is normal (S58), the card is ejected.

[0007]

[Problems to be solved by the device]

 However, in the above-mentioned conventional configuration, there is a problem that the card data or the magnetic head 1 cannot be normally recorded down to a deep layer due to space loss due to dust or the like attached to the magnetic head 1 and the card data is easily destroyed. In other words, since it is strong against space loss when reading data (Dμm at recording density 210 BPI), peak detection is possible even with a small magnetic signal input, and normal reading is possible. Since it is weak (about D / 5 μm at a recording density of 210 BPI), normal recording cannot be performed, and the data read operation for subsequent data verification malfunctions, resulting in the destruction of the initially written data. There was a problem.

The present invention solves the above-mentioned conventional problems, and by simply adding it to the magnetic reproducing circuit of the F2F system, it is possible to prevent the destruction of card data at the time of data rewriting with high accuracy and extremely. It is an object to provide a magnetic reproducing circuit having high reliability.

[0009]

[Means for Solving the Problems]

 In order to achieve this object, the magnetic reproducing circuit of the present invention detects an abnormality in the magnetic signal input level due to space loss, etc. by using the amplified signal of the magnetic head and the rectangular wave signal obtained by the conventional magnetic reproducing circuit. To do. Specifically, a differential amplifier circuit that amplifies the signal reproduced by the magnetic head, and a peak detection circuit that inverts the output signal at the peak point of the amplified signal of the differential amplifier circuit to form a rectangular wave signal. A reference voltage circuit that supplies a reference voltage to the dynamic amplification circuit and the peak detection circuit, an F2F demodulation circuit that receives the rectangular wave signal of the peak detection circuit and demodulates the data, and a comparison signal of the amplified signal and the comparison voltage. Is output at the change point of the rectangular wave signal, and an output level detection circuit for detecting an abnormality in the magnetic signal level is provided.

[0010]

[Action]

 With this configuration, since it is possible to detect an abnormality in the magnetic signal input level due to space loss during data reproduction, it is possible to prevent magnetic data from being destroyed by avoiding data recording after the abnormality is detected.

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a magnetic reproducing circuit according to an embodiment of the present invention. In FIG. 1, 1 is a magnetic head, 2 is an operation amplification circuit, 3 is a peak detection circuit, 4 is a reference voltage circuit, and 5 is an F2F demodulation circuit, which are the same as those in the conventional example shown in FIG. No. and the description is omitted. Reference numeral 6 is an output level detection circuit composed of a voltage comparator 7 and a flip-flop 8.

The operation of the magnetic reproducing circuit of the present embodiment configured as described above will be described below.

FIG. 2 is a waveform diagram showing the circuit operation of the magnetic reproducing circuit according to the embodiment of the present invention. In FIGS. 1 and 2, the inverting input of the voltage comparator 7 is supplied with the amplification signal a of the differential amplifier circuit 2, and the non-inverting input is connected with the reference voltage b of the reference voltage circuit 4 and the resistor R1. The comparison voltage g divided into a predetermined potential by R2 is input. That is, in a region where the amplified signal a exceeds the comparison voltage g, the output of the voltage comparator 7 is inverted and the waveform h is output. On the other hand, the amplified signal a is waveform-shaped by the peak detection circuit 3 into a rectangular wave signal c whose output is inverted at the peak point, and is clocked to the F2F demodulation circuit 5 and the flip-flop 8. The card running signal d obtained by the F2F demodulation circuit 5 is input to the flip-flop 8 to determine the output state when there is no magnetic signal input. As a result, the Q output of the flip-flop 8 becomes valid while the magnetic signal is being input, that is, while the card running signal d is at a low level, and the lower peak point of the amplified signal a of the differential amplifier circuit 2 is compared. At point A where voltage g cannot be exceeded, it changes from high level to low level, and this is held until point B where the next lower peak point exceeds comparative voltage g. Therefore, it is possible to detect the level decrease of the magnetic signal input by the low level of the level detection output i.

In the present embodiment, the comparison voltage g is set to a lower level than the reference voltage b, and the level is detected from the lower peak point of the amplified signal a. On the contrary, the comparison voltage g is changed to the reference voltage b. The level may be set to a higher level and the level may be detected from the upper peak point of the amplified signal a. Further, by providing a large number of such level detection circuits, multi-level level detection may be performed.

Next, a method of processing a prepaid card for a card reader / writer incorporating the magnetic reproducing circuit of the present embodiment will be described.

FIG. 3 is a flow chart of the card processing of the card reader / writer using the magnetic reproducing circuit according to the embodiment of the present invention. In FIG. 3, the card is read and the data is read (S1). If the data is normal (S2), it is confirmed whether the output level is normal (S3), and if the data is normal, data processing is performed (S4). If the data processing is normal (S6), the data is rewritten (S7) and the data is read and collated (S8). It is confirmed whether the data is normal (S9). If the data is normal, it is confirmed whether the output level is normal (S10) and the card is ejected.

As described above, according to this embodiment, it is possible to detect the state of the magnetic output level at the time of reading the data without affecting the demodulation of the data, and it is possible to detect the abnormal level at the time of the initial reading. Is detected and the subsequent recording of data is suppressed, the effect of preventing the destruction of card data is obtained. Also, by checking the level status at the time of data verification after data recording, it is possible to judge whether stable recording has been performed.

[0019]

[Effect of device]

 As described above, according to the present invention, since the level detection circuit for outputting the comparison signal of the amplified signal and the comparison voltage at the change point of the rectangular wave signal is provided, the abnormality of the magnetic signal input level due to the space loss can be detected. Since it is possible to build a highly accurate and extremely reliable card system that can prevent the destruction of card data, it can be easily incorporated into a conventional F2F magnetic reproducing circuit. It is possible to realize a magnetic reproducing circuit with low cost and excellent mass productivity.

[Brief description of drawings]

FIG. 1 is a block diagram of a magnetic reproducing circuit according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a circuit operation of a magnetic reproducing circuit according to an embodiment of the present invention.

FIG. 3 is a flowchart of a card processing of a card reader / writer using a magnetic reproducing circuit according to an embodiment of the present invention.

FIG. 4 is a block diagram of a conventional magnetic reproducing circuit.

FIG. 5 is a waveform diagram showing the circuit operation of a conventional magnetic reproducing circuit.

FIG. 6 is a flowchart of card processing of a card reader / writer using a conventional magnetic reproducing circuit.

[Explanation of symbols]

 1 magnetic head 2 differential amplifier circuit 3 peak detection circuit 4 reference voltage circuit 5 F2F demodulation circuit 6 output level detection circuit 7 voltage comparator 8 flip-flop

Claims (1)

[Scope of utility model registration request] 1. A differential amplifier circuit for amplifying a signal reproduced by a magnetic head, a peak detection circuit for inverting an output signal at a peak point of an amplified signal of the differential amplifier circuit to form a rectangular wave signal, and the difference. A reference voltage circuit that supplies a reference voltage to the dynamic amplification circuit and the peak detection circuit, an F2F demodulation circuit that receives the rectangular wave signal of the peak detection circuit and demodulates data, and a rectangular comparison signal between the amplified signal and a predetermined potential. A magnetic reproducing circuit, comprising: an output level detecting circuit that outputs an abnormality at a magnetic signal level by outputting at a change point of a wave signal.