US4864216A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Light emitting diode array current power supply
Assignee: HP Inc
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Filing: 1989-01-19
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Granted: 1989-09-05
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Expires: 2009-01-19
Abstract
Abstract A power supply circuit for an LED print head has a reference current source connected to a printer system reference voltage for providing a second reference voltage for an individual, integrated circuit chip. A plurality of substantially similar field effect transistors have their gates connected to the chip reference voltage for providing substantially similar current to each of a plurality of light emitting diodes. The current is enabled to each such LED by the presence or absence of a data signal. A reference resistor in the reference current source permits adjustment so that each of a plurality of integrated circuit chips can provide substantially similar current to each of a plurality of LED dice, or adjust the current level, if required, to achieve similar light output from each LED.
Inventors
- 👤 Steven Kalata
- 👤 Donald M. Reid
- 👤 Charles A. Brown
- 👤 Billy E. Thayer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 11:43
CPC Classifications
G; G05; G05F; G05F1/00; G05F1/10; G05F1/46; G05F1/56; G05F1/561; G06; G06K; G06K15/00; G06K15/02; G06K15/12; G06K15/1238; G06K15/1242; G06K15/1247
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
120 words
A power supply for a light emitting diode print head wherein the LEDs on the print head have substantially uniform light output as a function of current, comprising: a plurality of integrated circuit chips, each chip having a plurality of outputs for supplying current to each of a plurality of respective LEDs; means for applying a system reference voltage to each of the integrated circuit chips; means for generating a chip reference voltage for each of the plurality of chips in response to the system reference voltage; and means for applying a current to each LED output which is a function of the respective chip reference voltage and the presence or absence of a data signal for such LED output.
Claim 2
Dependent Claim
120 words
A power supply for a light emitting diode print head wherein the LEDs on the print head have substantially uniform light output as a function of current, comprising: a plurality of integrated circuit chips, each chip having a plurality of outputs for supplying current to each of a plurality of respective LEDs; means for applying a system reference voltage to each of the integrated circuit chips; means for generating a chip reference voltage for each of the plurality of chips in response to the system reference voltage; and means for applying a current to each LED output which is a function of the respective chip reference voltage and the presence or absence of a data signal for such LED output.
Claim 3
Dependent Claim
35 words
A power supply as recited in claim 1 further comprising means for setting the chip reference voltage for a respective chip to a value for equalizing current output for all of the integrated circuit chips.
Claim 4
Dependent Claim
34 words
A power supply as recited in claim 2 wherein the means for generating a chip reference voltage comprises a constant current source and a reference resistor for setting a constant current from such source.
Claim 5
Dependent Claim
58 words
A power supply as recited in claim 3 wherein the means for applying current for each LED comprises a data FET and a output driver FET in series, the gate of the output driver FET being connected to the chip reference voltage, and further comprising means for applying a data signal to the gate of the data FET.
Claim 6
Dependent Claim
34 words
A power supply as recited in claim 4 wherein the constant current source comprises a FET substantially the same as the output driver FETs and having the chip reference voltage applied to its gate.
Claim 7
Dependent Claim
58 words
A power supply as recited in claim 1 wherein the means for applying current for each LED comprises a data FET and a output driver FET in series, the gate of the output driver FET being connected to the chip reference voltage, and further comprising means for applying a data signal to the gate of the data FET.
Claim 8
Dependent Claim
82 words
A power supply for a light emitting diode print head comprising: a reference FET; a plurality of output driver FETs substantially similar to the reference FET, each having an output for connection to an LED; means for interconnecting the gates of all the FETs with the output of the reference FET; means for passing a constant current through the reference FET; and means for enabling current flow from each output driver FET to its respective LED in response to a data signal.
Claim 9
Dependent Claim
82 words
A power supply for a light emitting diode print head comprising: a reference FET; a plurality of output driver FETs substantially similar to the reference FET, each having an output for connection to an LED; means for interconnecting the gates of all the FETs with the output of the reference FET; means for passing a constant current through the reference FET; and means for enabling current flow from each output driver FET to its respective LED in response to a data signal.
Claim 10
Dependent Claim
30 words
A power supply as recited in claim 7 wherein the means for passing a constant current comprises an op-amp regulated current source and a reference resistor for setting the current.
Claim 11
Dependent Claim
40 words
A power supply as recited in claim 7 wherein the means for enabling current flow comprises a data FET in series with each output driver FET and means for applying a data signal to the gate of the data FET.
Claim 12
Dependent Claim
155 words
A power supply for a light emitting diode print head comprising: a plurality of integrated circuit chips, each chip having a plurality of outputs for supplying current to each of a plurality of respective LEDs; means for applying a system reference voltage to each of the integrated circuit chips; means for applying a current source voltage to each of the integrated circuit chips; and a reference resistor connected to each integrated circuit chip; each such integrated circuit chip comprising: a reference current source connected to the system reference voltage for providing a chip reference voltage; a plurality of data transistors, each being connected to a respective LED output; means for applying a data signal to the gate of each data transistor; a plurality of output driver transistors connected to the current source voltage and to a respective data transistor; and means for connecting the chip reference voltage to the gate of each output driver transistor.
Claim 13
Dependent Claim
155 words
A power supply for a light emitting diode print head comprising: a plurality of integrated circuit chips, each chip having a plurality of outputs for supplying current to each of a plurality of respective LEDs; means for applying a system reference voltage to each of the integrated circuit chips; means for applying a current source voltage to each of the integrated circuit chips; and a reference resistor connected to each integrated circuit chip; each such integrated circuit chip comprising: a reference current source connected to the system reference voltage for providing a chip reference voltage; a plurality of data transistors, each being connected to a respective LED output; means for applying a data signal to the gate of each data transistor; a plurality of output driver transistors connected to the current source voltage and to a respective data transistor; and means for connecting the chip reference voltage to the gate of each output driver transistor.
Claim 14
Dependent Claim
36 words
A power supply as recited in claim 10 comprising a reference resistor connected to the reference current source on each integrated circuit chip for setting the current in the reference current source on the respective chip.
Claim 15
Dependent Claim
16 words
A power supply as recited in claim 10 wherein each transistor is a field effect transistor.
Claim 16
Dependent Claim
31 words
A power supply as recited in claim 10 wherein the reference current source provides the reference voltage at the drain of a p-channel FET having its drain connected to its gate.
Claim 17
Dependent Claim
34 words
A power supply as recited in claim 13 wherein the output driver FETs are also p-channel FETs and each of the output driver FETs has its drain connected to a respective data FET source.
Claim 18
Independent Claim
142 words
A method for obtaining uniform light output from a plurality of light emitting diodes on an LED print head comprising the steps of: sorting a plurality of LED dice, each having a plurality of LEDs thereon, according to their light output as a function of current; placing a plurality of such LEDs having substantially the same light output as a function of current in a row on a substrate; placing a row of integrated circuit chips on the substrate beside the row of LED dice; providing current to each LED from a separate output driver on one of the integrated circuit chips; controlling the current from all the output drivers on each integrated circuit chip with a chip reference voltage; and adjusting the chip reference voltages for individual chips, if required, for providing substantially the same light output from each LED die.
Claim 19
Independent Claim
142 words
A method for obtaining uniform light output from a plurality of light emitting diodes on an LED print head comprising the steps of: sorting a plurality of LED dice, each having a plurality of LEDs thereon, according to their light output as a function of current; placing a plurality of such LEDs having substantially the same light output as a function of current in a row on a substrate; placing a row of integrated circuit chips on the substrate beside the row of LED dice; providing current to each LED from a separate output driver on one of the integrated circuit chips; controlling the current from all the output drivers on each integrated circuit chip with a chip reference voltage; and adjusting the chip reference voltages for individual chips, if required, for providing substantially the same light output from each LED die.
Claim 20
Dependent Claim
29 words
A method as recited in claim 15 comprising providing a system reference voltage to all of the integrated circuit chips for controlling all the chip reference voltages in synchronism.
Claim 21
Dependent Claim
33 words
A method as recited in claim 15 wherein the step of adjusting a chip reference voltage comprises selecting a resistance value in a constant current source for providing a desired chip reference voltage.
Claim 22
Dependent Claim
24 words
A method as recited in claim 15 comprising switching current from each output driver to its respective LED in response to a data signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-09-04 | 1993-03-06 | 1993-09-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-09-04 | 1997-03-06 | 1997-09-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-09-04 | 2001-03-06 | 2001-09-05 | $7700.00 | Window Closed / Lapsed |