Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-04-25
2002-09-17
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C347S237000, C347S238000, C347S247000, C347S249000
Reexamination Certificate
active
06452342
ABSTRACT:
TECHNICAL FIELD
The present invention relates to generally a self-scanning light-emitting device, particularly to a self-scanning light-emitting device in which the number of bonding pads can be decreased.
BACKGROUND ART
A light-emitting device in which a plurality of light-emitting elements are arrayed on the same substrate is utilized as a light source of a printer, in combination with a driver circuit. The inventors of the present invention have interested in a three-terminal light-emitting thyristor having a pnpn-structure as an element of the light-emitting device, and have already filed several patent applications (see Japanese Patent Publication Nos. 1-238962, 2-14584, 2-92650, and 2-92651.) These publications have disclosed that a self-scanning function for light-emitting elements may be implemented, and further have disclosed that such self-scanning light-emitting device has a simple and compact structure for a light source of a printer, and has smaller arranging pitch of thyristors.
The inventors have further provided a self-scanning light-emitting device having such structure that an array of light-emitting thyristors having a transfer function is separated from an array of light-emitting thyristor having a write function (see Japanese Patent Publication No. 2-263668.)
Referring to
FIG. 1
, there is shown an equivalent circuit diagram of a conventional self-scanning light-emitting device. This self-scanning light-emitting device is a type of two-phase driving device. In the figure, reference characters T
1
, T
2
, T
3
. . . designate light-emitting elements, D
1
, D
2
, D
3
. . . coupling diodes, R
1
, R
2
, R
3
load resistors, respectively, the light-emitting elements being consisted of three-terminal light-emitting thyristors. All of the cathodes of the light-emitting elements are connected to the ground, the anodes of odd-numbered light-emitting elements to a clock pulse &phgr;
1
line
11
, the anode of even-numbered light-emitting elements to a clock pulse &phgr;
2
line
12
, respectively. Each gate of the light-emitting elements is connected to a power supply voltage &phgr;
GK
line
14
via respective load resistor R
1
, R
2
, R
3
. . . . The gate electrodes of neighboring light-emitting elements are connected to each other via respective coupling diodes D
1
, D
2
, D
3
. . . . Lines
11
,
12
and
14
are derived outward via bonding pads
21
,
22
and
24
, respectively. The gate of the light-emitting element T
1
is connected to the bonding pad
23
for a start pulse &phgr;
s
. In the figure, reference numeral
10
shows a chip for the integrated self-scanning light-emitting device.
Bonding pads
21
,
22
and
23
are connected to output terminals
41
(&phgr;
1
),
42
(&phgr;
2
) and
43
(&phgr;
s
) of a driver circuit
40
via exterior current limiting resistors
51
,
52
and
53
, respectively, and the bonding pad
24
is directly connected to a output terminal
44
(&phgr;
GK
) of the driver circuit
40
.
Referring to
FIG. 2
, there is shown the timing of driving pulses &phgr;
1
, &phgr;
2
, &phgr;
GK
and &phgr;
s
from the driver circuit
40
. The levels of each pulse include High level and Low level, Low level being equal to a cathode potential, i.e. a ground potential.
In
FIG. 2
, L (T
1
), L (T
2
), L (T
3
) . . . show the state of the light emission of the element T
1
, T
2
, T
3
. . . , the element being emitting state, i.e. on-state at the timing of a shaded area.
The timing diagram of
FIG. 2
is illustrated with divided three modes, i.e. MODE-
1
(standby mode), MODE-
2
(transition mode), and MODE-
3
(transfer mode). In the standby mode (MODE-
1
), all of the light-emitting elements are off-state with &phgr;
1
, &phgr;
2
, &phgr;
GK
and &phgr;
s
being Low level. Transition mode (MODE-
2
) has a time duration during which the power supply voltage pulse &phgr;
GK
is required to be driven to High level. In the transfer mode (MODE-
3
), the light-emitting element T
1
is turned on when the clock pulse &phgr;
1
is driven to High level during the start pulse &phgr;
s
is at Low level. The start pulse &phgr;
s
is turned to High level just after the element T
1
is turned on. After the element T
1
is turned on, the on-state of the elements is transferred by means of two-phase clock pulses &phgr;
1
and &phgr;
2
.
According to the structure of this conventional self-scanning light-emitting device, four bonding pads
21
(&phgr;
1
),
22
(&phgr;),
23
(&phgr;
s
) and
24
(&phgr;
GK
) are required in a chip due to the wiring to the driver circuit, consequently it is difficult to make such a chip small.
DISCLOSURE OF INVENTION
The object of the present invention is to provide a self-scanning light-emitting device in which the number of bonding pads in a chip may be decreased to 2 or 3.
According to the present invention, the number of pads in a chip may be decreased in a self-scanning light-emitting device comprising an array of a plurality of three-terminal light-emitting elements linearly arranged each having a control electrode for controlling threshold voltage or current; electrical means having unidirectional characteristic to voltage or current for connecting the control electrodes of neighboring light-emitting elements to each other; two clock pulse lines for applying two-phase clock pulses alternately to one of two terminals except the control electrode of each light-emitting element, one phase clock pulse of the two-phase clock pulses causing the threshold voltage or current of the light-emitting elements in the vicinity of a turned-on light-emitting element to vary via the electrical means, and the other phase clock pulse of the two-phase clock pulses causing the light-emitting element neighbored to the turned-on light-emitting element to turn on; and a power supply line connected to each of the control electrodes of the light-emitting elements via a load resistor, respectively.
In order to realize this, the following approaches may be adopted.
(1) The resistance of the load resistor connected to the light-emitting element to be turned on at first is selected to be smaller than that of other resistors. As a result, the bonding pad for a start pulse may be omitted.
(2) A diode or resistor is connected between one of the two clock pulse lines and the control electrode of the light-emitting element to be turned on at first. As a result, the bonding pad for a start pulse may be omitted.
(3) A logical OR circuit consisting of a diode-diode logic is connected between the two clock pulse lines and the power supply line. As a result, the bonding pad for the power supply pulse may be omitted.
(4) A logical OR circuit consisting of a diode-diode logic is connected between the two clock pulse lines and the power supply line, and a diode or resistor is connected between one of the two clock pulse lines and the control electrode of the light-emitting element to be turned on at first. As a result, the bonding pads for the start pulse and the power supply pulse may be omitted.
Also, the present invention is applicable to a type of self-scanning light-emitting device wherein transfer and light emission functions are separated. This type of device comprises an array of a plurality of three-terminal transfer elements linearly arranged each having a control electrode for controlling threshold voltage or current; electrical means having unidirectional characteristic to voltage or current for connecting the control electrodes of neighboring transfer elements to each other; two clock pulse lines for applying two-phase clock pulses alternately to one of two terminals except the control electrode of each transfer element, one phase clock pulse of the two-phase clock pulses causing the threshold voltage or current of the transfer elements in the vicinity of a turned-on transfer element to vary via the electrical means, and the other phase clock pulse of the two-phase clock pulses causing the transfer element neighbored to the turned-on transfer element to turn on; a power supply line connected to each of the control electrodes of the transfer
Nippon Sheet Glass Co. Ltd.
RatnerPrestia
Vo Tuyet T.
Wong Don
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