Electrical transmission or interconnection systems – Plural supply circuits or sources – Diverse or unlike electrical characteristics
Reexamination Certificate
1999-04-22
2001-08-21
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Plural supply circuits or sources
Diverse or unlike electrical characteristics
C307S046000
Reexamination Certificate
active
06278202
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power supply circuit and a disk drive provided with the power supply circuit.
A typical example of a conventional power supply circuit for supplying electric power to a largely variable power-consuming load is a power supply circuit used for disk drives capable of storing and retrieving information held on disk media.
Referring to
FIGS. 1
to
3
, the conventional power circuit used for a portable type MD (magnetic disk) recording and reproducing device will be described below.
In
FIGS. 1
to
3
, there is shown a recording and reproducing means 1 composed of a pickup, a pickup servo, a pickup drive and radio-frequency amplifier, which writes data on a disk by a high-power laser beam generated by the pickup and reads data from a disk by a micro-power laser beam generated therefrom.
There is shown a signal processing circuit
2
for transferring data from and to the recording and reproducing means 1 and processing the data by companding (compressing and expanding), which circuit includes a memory
2
a
in which data compressed when recording by the signal processing circuit
2
and compressed data read from the disk are stored. While the data is compressed and stored by the signal processing circuit
2
with the memory
2
a
, the pickup has nothing to do and, therefore, stops emission of a laser beam to the disk and the pickup servo and the drive also stop. This realizes a considerable saving in electric power since the load while the pickup halts is smaller than a half of the load while the pickup being in operation.
Numeral
3
denotes a microcomputer for control of an entire system of the MD recording and reproducing device and numeral
4
denotes a signal converting circuit whereby data input through an input terminal is converted from analog to digital and transferred to the signal processing circuit
2
and data output from the signal processing circuit
2
is converted from digital to analog and transferred to an output terminal.
A first voltage increasing/decreasing circuit
5
a
(up-down type DC-DC converter)
5
a
is used for increasing or decreasing a voltage from a power supply circuit (to be described later) to 2.5 volts and a second voltage increasing/decreasing circuit (up-down type DC-DC converter)
5
b
is used for increasing and decreasing a voltage from the power supply circuit (to be described later) to 2.8 volts. The first voltage increasing/decreasing circuit (DC-DC converter circuit)
5
a
is connected to a circuit requiring the power supply of 2.5 volts while the second voltage increasing/decreasing circuit (DC-DC converter circuit)
5
b
is connected to a circuit requiring the power supply of 2.8 volts. The decreasing or increasing of voltage transferred from the power supply circuit (to be described later) is needed because the voltage may not be constant and is more and less than a required value.
There is also shown a dry battery
6
a
, a rechargeable battery
6
b
capable of charging and discharging and an AC adapter
6
c
for converting an alternating current to a direct current. These components are selectively attached and detached by a user of the device. The magnitudes of the output voltages of the respective power sources, i.e., the AC adapter
6
c
, the rechargeable battery
6
c
and the dry battery
6
a
become smaller in the described order. The dry battery
6
a
are inserted in a battery case
10
as illustrated in
FIGS. 2A
,
2
B and the battery case
10
is then fitted at its male terminals in corresponding female terminals of the device body
20
as illustrated in FIG.
3
. The battery case
10
is electrically connected to the device body
20
by turning a tightening screw. Because current from the dry battery
6
a
is constant in line to the first DC-DC converter circuit
5
a
and the second DC-DC converter circuit
5
b
, power loss due to resistance of a transmission line from the dry battery
6
a
to a load cannot be neglected.
Switches
7
a
,
7
b
and
7
c
are used for turning on the power supply from the dry battery
6
a
, the rechargeable battery
6
b
and the AC adapter
6
c
respectively. The switches
7
a
,
7
b
,
7
c
are turned on and off according to control signals of the microcomputer
3
to transmit the power to the first DC-DC converter circuit
5
a
, the second DC-DC converter circuit
5
b
and a voltage increasing circuit
8
to be described later. The switches
7
a
,
7
b
and
7
c
may be of, e.g., a power MOSFET (metal-oxide-semiconductor transistor) having small on-resistance.
Diodes
7
d
,
7
e
,
7
f
are disposed in parallel with the switches
7
a
,
7
b
,
7
c
respectively. When any of the power sources was disconnected by the user, another power supply whose output voltage is next in magnitude to that of the removed power supply is selected to output a voltage through the diode corresponding to the selected power supply.
A voltage increasing circuit
8
is used for increasing an input voltage to 2.8 volts. This circuit is connected to the switches
7
a
,
7
b
and
7
c
respectively and can receive power from the dry battery
6
a
, the rechargeable battery
6
b
and the AC adapter
6
c
. The power from the dry battery
6
a
is increased to 2.8 volts and further transmitted. On the other hand, the power generated by the rechargeable battery
6
b
or the AC adapter
6
c
is transmitted without being increased since the output voltage is higher than 2.8 volts.
A voltage decreasing circuit
9
is used for decreasing the power voltage fed from the voltage increasing circuit
8
to 2.5 volts that is then used for driving the microcomputer
3
. The voltage increasing circuit
8
and the voltage degreasing circuit
9
is provided to drive the microcomputer
3
first without fail when a start (power) key (not shown) of the MD recording and reproducing device is turned on. Namely, the first voltage increasing and decreasing circuit
5
a
is controlled by the microcomputer
3
and, therefore, it cannot drive the microcomputer
3
.
In the above-described MD recording and reproducing device, the microcomputer
3
is unconditionally driven when a start key (not shown) on the device is turned on, and it recognizes the power sources attached to the device body by measuring voltage of each power supply and selects one of the attached power sources according to the priority in the order of the AC adapter
6
c
, the rechargeable battery
6
b
and the dry battery
6
a
. The microcomputer
3
then turns on a switch (
7
a
,
7
b
or
7
c
) corresponding to the selected power supply to transmit power therefrom to the device. The microcomputer
3
determines the output voltage of the power supply when the output increases and when data is written or read by the device, compares the measured voltage with a warning level and a life-end level preset for each power supply mode and gives a warning indicating the battery approaching to the life end level or stops the power supply mode when its output reaches the life end level.
The warning voltage level of a dry battery
6
a
when writing data on a disk is 1.0 volts and its life-end level is 0.9 volts. The warning level of the battery
6
a
when reading data from a disk is 1.0 volts and the life-limit level is 0.8 volts. The warning level and the life-limit level of the battery
6
a
for the writing operation are set higher than those for the reading operation. This is because the load during the recording operation is higher than the load during the reproducing operation and, furthermore, the data recording operation is not completed by writing main data on a magnetic disk (MD) and continues until UTOC (User Table Of Contents) data relating to the main data is recorded in a UTOC area. Namely, the recording operation requires additional power energy for writing UTOC data for all the main data written during the operation.
The above-described conventional device involves the following drawbacks:
1. The microcomputer may have a hang-up or a dead halt.
When the device was de-energized by eventually disconnecting a power s
Ohshita Akihiro
Sakagawa Masahiro
Conlin David G.
Dike Bronstein, Roberts & Cushman IP Group of Edwards & Angell,
Fleming Fritz
Sharp Kabushiki Kaisha
Tucker David A.
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