# US 12,759,288 B2 · Head unit and liquid ejection apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,759,288 B2 - Document ID: US12759288B2 - Status: Granted - Kind: B2 - Application number: 18/925,223 - Filed: 2024-10-24 - Published: 2025-05-01 - Granted: 2026-10-13 - Earliest claimed: 2023-10-25 - Assignees: Seiko Epson Corporation - Applicants: Seiko Epson Corporation - Inventors: Toshimichi Yamada - Web page: https://patentgrep.com/patent/US12759288B2 ## CPC - B41J 2/04541: {Specific driving circuit} - B41J 2/0451: {for detecting failure, e.g. clogging, malfunctioning actuator} - B41J 2/04548: {Details of power line section of control circuit} - B41J 2/0455: {Details of switching sections of circuit, e.g. transistors} - B41J 2/04581: {controlling heads based on piezoelectric elements} - B41J 2/04588: {using a specific waveform} - B41J 2/04596: {Non-ejecting pulses} - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS ## Abstract A head unit includes a drive signal output circuit including a first constant current output circuit for outputting a first constant current signal based on a first DC voltage signal, a second constant current output circuit for outputting a second constant current signal based on a second DC voltage signal, and a selection control circuit for controlling the first constant current output circuit and the second constant current output circuit based on an ejection control signal, the selection control circuit controls whether the first constant current output circuit outputs the first constant current signal and whether the second constant current output circuit outputs the second constant current signal based on the ejection control signal, and the drive signal output circuit outputs a first drive signal corresponding to the first constant current signal and the second constant current signal to a first piezoelectric element. ## Claims ### Claim 1 A head unit comprising: a first ejection unit which includes a first piezoelectric element to be driven by a first drive signal, and is configured to eject a liquid due to drive of the first piezoelectric element; and a drive signal output circuit to which a first DC voltage signal having a first voltage value, a second DC voltage signal having a second voltage value, and an ejection control signal are input, and which is configured to output the first drive signal, wherein the drive signal output circuit includes a first constant current output circuit configured to output a first constant current signal based on the first DC voltage signal, a second constant current output circuit configured to output a second constant current signal based on the second DC voltage signal, and a selection control circuit configured to control the first constant current output circuit and the second constant current output circuit based on the ejection control signal, the selection control circuit is configured to control whether the first constant current output circuit outputs the first constant current signal and whether the second constant current output circuit outputs the second constant current signal based on the ejection control signal, and the drive signal output circuit is configured to output the first drive signal corresponding to the first constant current signal and the second constant current signal. ### Claim 2 (depends on 1) The head unit according to claim 1, wherein the first voltage value is greater than the second voltage value, the first constant current output circuit includes a P-channel FET, and the second constant current output circuit includes an N-channel FET. ### Claim 3 (depends on 1) The head unit according to claim 1, wherein a third DC voltage signal having a third voltage value is further input to the drive signal output circuit, the drive signal output circuit includes a third constant current output circuit configured to output a third constant current signal based on the third DC voltage signal, the selection control circuit is configured to control whether the third constant current output circuit outputs the third constant current signal based on the ejection control signal, and the drive signal output circuit is configured to output the first drive signal corresponding to the first constant current signal, the second constant current signal, and the third constant current signal. ### Claim 4 (depends on 3) The head unit according to claim 3, wherein the first voltage value is larger than the second voltage value, the third voltage value is larger than the first voltage value, the first constant current output circuit includes an N-channel FET and a P-channel FET, the second constant current output circuit includes an N-channel FET, and the third constant current output circuit includes a P-channel FET. ### Claim 5 (depends on 1) The head unit according to claim 1, further comprising: a second ejection unit which includes a second piezoelectric element driven by a second drive signal, and is configured to eject the liquid due to the drive of the second piezoelectric element, wherein the drive signal output circuit includes a fourth constant current output circuit configured to output a fourth constant current signal based on the first DC voltage signal, and a fifth constant current output circuit configured to output a fifth constant current signal based on the second DC voltage signal, the selection control circuit is configured to control whether the fourth constant current output circuit outputs the fourth constant current signal and whether the fifth constant current output circuit outputs the fifth constant current signal based on the ejection control signal, and the drive signal output circuit is configured to output the second drive signal corresponding to the fourth constant current signal and the fifth constant current signal. ### Claim 6 (depends on 1) The head unit according to claim 1, wherein the drive signal output circuit is configured to output the first drive signal including an ejection waveform which drives the first piezoelectric element so that the liquid is ejected from the first ejection unit. ### Claim 7 (depends on 1) The head unit according to claim 1, wherein the drive signal output circuit is configured to output the first drive signal including a microvibration waveform which drives the first piezoelectric element so that the liquid is not ejected from the first ejection unit. ### Claim 8 (depends on 1) The head unit according to claim 1, wherein the drive signal output circuit is configured to output the first drive signal including an inspection waveform for inspecting a state of the first ejection unit. ### Claim 9 (depends on 1) The head unit according to claim 1, wherein the first constant current output circuit includes a first constant current circuit one end of which is supplied with the first DC voltage signal, another end of which is electrically coupled to the first piezoelectric element, and which is configured to output a first current signal based on the first DC voltage signal, and a second constant current circuit one end of which is supplied with the first DC voltage signal, another end of which is electrically coupled to the first piezoelectric element, and which is configured to output a second current signal based on the first DC voltage signal. ### Claim 10 (depends on 9) The head unit according to claim 9, wherein the selection control circuit controls a current value of the first constant current signal by controlling whether the first constant current circuit outputs the first current signal and whether the second constant current circuit outputs the second current signal based on the ejection control signal. ### Claim 11 A liquid ejection apparatus comprising: a first ejection unit which includes a first piezoelectric element to be driven by a first drive signal, and is configured to eject a liquid due to drive of the first piezoelectric element; a drive signal output circuit to which a first DC voltage signal having a first voltage value, a second DC voltage signal having a second voltage value, and an ejection control signal are input, and which is configured to output the first drive signal; and a control circuit configured to output the ejection control signal, wherein the drive signal output circuit includes a first constant current output circuit configured to output a first constant current signal based on the first DC voltage signal, a second constant current output circuit configured to output a second constant current signal based on the second DC voltage signal, and a selection control circuit configured to control the first constant current output circuit and the second constant current output circuit based on the ejection control signal, the selection control circuit is configured to control whether the first constant current output circuit outputs the first constant current signal and whether the second constant current output circuit outputs the second constant current signal based on the ejection control signal, and the drive signal output circuit is configured to output the first drive signal corresponding to the first constant current signal and the second constant current signal. ### Claim 12 (depends on 11) The liquid ejection apparatus according to claim 11, wherein the first voltage value is greater than the second voltage value, the first constant current output circuit includes a P-channel FET, and the second constant current output circuit includes an N-channel FET. ### Claim 13 (depends on 11) The liquid ejection apparatus according to claim 11, wherein a third DC voltage signal having a third voltage value is further input to the drive signal output circuit, the drive signal output circuit includes a third constant current output circuit configured to output a third constant current signal based on the third DC voltage signal, the selection control circuit is configured to control whether the third constant current output circuit outputs the third constant current signal based on the ejection control signal, and the drive signal output circuit is configured to output the first drive signal corresponding to the first constant current signal, the second constant current signal, and the third constant current signal. ### Claim 14 (depends on 13) The liquid ejection apparatus according to claim 13, wherein the first voltage value is larger than the second voltage value, the third voltage value is larger than the first voltage value, the first constant current output circuit includes an N-channel FET and a P-channel FET, the second constant current output circuit includes an N-channel FET, and the third constant current output circuit includes a P-channel FET. ### Claim 15 (depends on 11) The liquid ejection apparatus according to claim 11, further comprising: a second ejection unit which includes a second piezoelectric element driven by a second drive signal, and is configured to eject the liquid due to the drive of the second piezoelectric element, wherein the drive signal output circuit includes a fourth constant current output circuit configured to output a fourth constant current signal based on the first DC voltage signal, and a fifth constant current output circuit configured to output a fifth constant current signal based on the second DC voltage signal, the selection control circuit is configured to control whether the fourth constant current output circuit outputs the fourth constant current signal and whether the fifth constant current output circuit outputs the fifth constant current signal based on the ejection control signal, and the drive signal output circuit is configured to output the second drive signal corresponding to the fourth constant current signal and the fifth constant current signal. ### Claim 16 (depends on 11) The liquid ejection apparatus according to claim 11, wherein the drive signal output circuit is configured to output the first drive signal including an ejection waveform which drives the first piezoelectric element so that the liquid is ejected from the first ejection unit. ### Claim 17 (depends on 11) The liquid ejection apparatus according to claim 11, wherein the drive signal output circuit is configured to output the first drive signal including a microvibration waveform which drives the first piezoelectric element so that the liquid is not ejected from the first ejection unit. ### Claim 18 (depends on 11) The liquid ejection apparatus according to claim 11, wherein the drive signal output circuit is configured to output the first drive signal including an inspection waveform for inspecting a state of the first ejection unit. ### Claim 19 (depends on 11) The liquid ejection apparatus according to claim 11, wherein the first constant current output circuit includes a first constant current circuit one end of which is supplied with the first DC voltage signal, another end of which is electrically coupled to the first piezoelectric element, and which is configured to output a first current signal based on the first DC voltage signal, and a second constant current circuit one end of which is supplied with the first DC voltage signal, another end of which is electrically coupled to the first piezoelectric element, and which is configured to output a second current signal based on the first DC voltage signal. ### Claim 20 (depends on 19) The liquid ejection apparatus according to claim 19, wherein the selection control circuit controls a current value of the first constant current signal by controlling whether the first constant current circuit outputs the first current signal and whether the second constant current circuit outputs the second current signal based on the ejection control signal.