# US 5,331,477 A · Low voltage, constant current magnetic transducer drive system for digital recording

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- Number: US 5,331,477 A
- Document ID: US5331477A
- Status: Granted
- Kind: A
- Application number: 07/992,451
- Filed: 1992-12-17
- Granted: 1994-07-19
- Earliest claimed: 1991-12-24
- Assignees: TEAC Corporation
- Inventors: Sho Sugiyama
- Web page: https://patentgrep.com/patent/US5331477A

## CPC

- G11B 11/10508: {by modulating only the magnetic field at the transducer}
- G11B 5/09: Digital recording
- H03K 17/6871: {the output circuit comprising more than one controlled field-effect transistor}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)

## Abstract

A magnetic transducer has its opposite coil extremities connected to a direct current power supply via a pair of inductance elements, respectively. The transducer coil is excited not only from the power supply but from the inductance elements as a write control circuit applies a binary write control signal, representative of digital information to be recorded, to a pair of semiconductor switches thereby causing the same to be alternately turned on and off. Being typically in the form of metal oxide semiconductor field effect transistors, the semiconductor switches permit the flow therethrough of a current of varying magnitudes when open. A pair of reverse blocking diodes are therefore connected in series with the respective semiconductor switches in order to make constant the current flowing through the transducer.

## Claims

### Claim 1

A low voltage, constant current digital recording system comprising:
(a) a magnetic transducer having a coil;
(b) a direct current power supply;
(c) a pair of inductance elements connected respectively between a pair of opposite extremities of the transducer coil and a first terminal of the power supply;
(d) a pair of semiconductor switches connected respectively between the pair of opposite extremities of the transducer coil and a second terminal of the power supply;
(e) a write control circuit connected to the pair of semiconductor switches for applying thereto a binary write control signal representative of digital information to be recorded, in order to cause the semiconductor switches to be alternately turned on and off, with the consequent excitation of the transducer coil not only from the power supply but also from the inductance elements;
(f) a pair of reverse blocking diodes connected in series with the pair of semiconductor switches, respectively, in order to prevent current flow, during the excitation of the transducer coil with the closure of either of the semiconductor switches, through the other of the semiconductor switches; and
(g) a pair of antiringing inductance elements connected in series with the pair of semiconductor switches, respectively;
(h) whereby the transducer coil can be excited with a more constant current, and with a lower supply voltage, than heretofore.

### Claim 2 (depends on 1)

The low voltage, constant current digital recording system of claim 1 wherein each antiringing inductant element comprises:
(a) A bead of magnetic material having a hole; and
(b) a conductor extending through the hole in the bead.

### Claim 3

A low voltage, constant current digital recording system comprising:
(a) a magnetic transducer having a coil;
(b) a direct current power supply;
(c) a pair of inductance elements connected respectively between a pair of opposite extremities of the transducer coil and a first terminal of the power supply;
(d) a pair of semiconductor switches connected respectively between the pair of opposite extremities of the transducer coil and a second terminal of the power supply;
(e) a write control circuit connected to the pair of semiconductor switches for applying thereto a binary write control signal representative of digital information to be recorded, in order to cause the semiconductor switches to be alternately turned on and off, with the consequent excitation of the transducer coil not only from the power supply but also from the inductance elements;
(f) a pair of reverse blocking diodes connected in series with the pair of semiconductor switches, respectively, in order to prevent current flow, during the excitation of the transducer coil with the closure of either of the semiconductor switches, through the other of the semiconductor switches;
(g) a first antiringing resistor connected between the first extremity of the transducer coil and ground; and
(h) a second antiringing resistor connected between the second extremity of the transducer coil and the ground;
(i) whereby the transducer coil can be excited with a more constant current, and with a lower supply voltage, than heretofore.