# US 9,049,772 B2 · Driving method for discharge lamp, driving device for discharge lamp, light source device, and image display apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,049,772 B2 - Document ID: US9049772B2 - Status: Granted - Kind: B2 - Application number: 13/740,940 - Filed: 2013-01-14 - Published: 2013-05-23 - Granted: 2015-06-02 - Earliest claimed: 2008-12-05 - Assignees: Seiko Epson Corporation - Applicants: Seiko Epson Corporation - Inventors: Shigeyasu Soma; Tetsuo Terashima - Web page: https://patentgrep.com/patent/US9049772B2 ## CPC - H05B 41/16: in which the lamp is fed by DC or by low-frequency AC, e.g. by 50 cycles/sec AC {, or with network frequencies} - H05B 41/2928: {for protecting the lamp against abnormal operating conditions} - Y02B 20/00: Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract In at least one embodiment of the disclosure, a driving device for a discharge lamp includes an alternating current supply section and a frequency modulation section. The alternating current supply section supplies two electrodes of the discharge lamp with an alternating current. The alternating current comprises a plurality of modulation periods. The frequency modulation section modulates a frequency of the alternating current so as to provide a plurality of retentive periods within each of the modulation periods. Each retentive period has a constant frequency that is different from a frequency of its temporally adjacent retentive periods. The frequency modulation section lengthens a length of at least one of the retentive periods in the modulation period in response to a predetermined condition occurring. The frequency of at least one of the retentive periods is equal to or higher than a predetermined reference frequency. ## Claims ### Claim 1 A driving device for a discharge lamp, comprising: an alternating current supply section configured to supply two electrodes of the discharge lamp with an alternating current; and a frequency modulation section configured to modulate a frequency of the alternating current in accordance with a first modulation pattern and a second modulation pattern respectively including a plurality of retentive periods, each retentive period having a constant frequency and temporally adjacent retentive periods having different frequencies from each other, wherein the frequency modulation section is configured to modulate the frequency in accordance with the first modulation pattern when a predetermined condition is not met, and modulate the frequency in accordance with the second modulation pattern when the predetermined condition is met, and the second modulation pattern is a pattern in which a length of at least one of the retentive periods having a frequency equal to or higher that a predetermined reference frequency of the plurality of retentive periods in the first modulation pattern is elongated. ### Claim 2 (depends on 1) The driving device according to claim 1, wherein the predetermined condition is determined based on a deterioration state of the discharge lamp, and the frequency modulation section modulates the frequency of the alternating current in accordance with the second modulation pattern in response to a determination that a deterioration of the discharge lamp is in progress. ### Claim 3 (depends on 2) The driving according to claim 2, further comprising: a lighting time accumulation section configured to calculate an accumulated lighting time from a start of use of the discharge lamp as a parameter representing the deterioration state of the discharge lamp, and wherein the frequency modulation section modulates the frequency in accordance with the second modulation pattern in response to the accumulated lighting time being higher that a predetermined value. ### Claim 4 (depends on 1) The driving device according to claim 1, wherein the second pattern is a pattern in which a length of the retentive period having a highest frequency of the plurality of retentive periods in the first modulation pattern is elongated. ### Claim 5 (depends on 1) The driving device according to claim 1, wherein the second pattern is a pattern in which a length of a least one of the retentive periods, excluding elongated retentive periods, of the plurality of retentive periods in the first modulation pattern is shortened. ### Claim 6 (depends on 1) The driving device according to claim 1, wherein the second pattern is a pattern in which a length of the retentive periods having a frequency equal to or higher than the predetermined reference frequency of the plurality of retentive periods in the first modulation pattern is elongated. ### Claim 7 (depends on 1) The driving device according to claim 1, wherein the predetermined reference frequency is a frequency at which flicker is apt to occur. ### Claim 8 An image display apparatus comprising: a discharge lamp configured to emit light; a light modulation section configured to modulate the light emitted from the discharge lamp; a projection optical system configured to project the light modulated by the light modulation section; an alternating current supply section configured to supply two electrodes of the discharge lamp with an alternating current to light the discharge lamp; and a frequency modulation section configured to modulate a frequency of the alternating current in accordance with a first modulation pattern and a second modulation pattern respectively including a plurality of retentive periods, each retentive period having a constant frequency and temporally adjacent retentive periods having different frequencies form each other, wherein the frequency modulation section is configured to modulate the frequency in accordance with the first modulation pattern when a predetermined condition is not met, and modulate the frequency in accordance with the second modulation pattern when the predetermined condition is met, and the second modulation pattern is a pattern in which a length of at least one of the retentive periods having a frequency equal to or higher than a predetermined reference frequency of the plurality of retentive periods in the first modulation pattern is elongated. ### Claim 9 A driving method for a discharge lamp, comprising: supplying an alternating current between two electrodes of the discharge lamp; modulating a frequency of the alternating current in accordance with a first modulation pattern and a second modulation pattern respectively including a plurality of retentive periods, each retentive period having a constant frequency and temporally adjacent retentive periods having different frequencies from each other; and modulating the frequency in accordance with the first modulation pattern when a predetermined condition is not met, and modulating the frequency in accordance with the second modulation pattern when the predetermined condition is met, the second modulation pattern being a pattern in which a length of at least one of the retentive periods having a frequency equal to or higher than a predetermined reference frequency of the plurality of retentive periods in the first modulation pattern is elongated.