# US 7,411,359 B2 · Apparatus and method for providing dimming control of lamps and electrical lighting systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,411,359 B2 - Document ID: US7411359B2 - Status: Granted - Kind: B2 - Application number: 10/569,588 - Filed: 2004-08-26 - Published: 2007-03-15 - Granted: 2008-08-12 - Earliest claimed: 2003-08-27 - Assignees: e.Energy Double Tree Limited - Inventors: Shu-hung Henry Chung; Ngai Man Ho; Shu-Yuen Ron Hui - Web page: https://patentgrep.com/patent/US7411359B2 ## CPC - H05B 41/3921: {with possibility of light intensity variations} - H05B 41/3924: {by phase control, e.g. using a triac (H05B41/3922 takes precedence)} - H05B 41/3927: {by pulse width modulation (H05B41/3922 takes precedence)} - Y10S 315/04: Dimming circuit for fluorescent lamps - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract Dimming of an electrical lamp of the type driven by a ballast is provided by a reactive power device in series between the AC supply and the ballast. The reactive power device provides a variable auxiliary voltage out of phase by 90 or 270 degrees with the current such that a smaller magnitude voltage is applied to the lamp. The dimming device has a switch to enable/disable dimming. When the switch is enabled, the voltage applied to the lamp is controlled by a half-bridge inverter with a pair of totem pole power electronic switches, along with a pair of DC series capacitors and a low-pass filter. ## Claims ### Claim 1 Apparatus for providing dimming control of an electrical lamp of the type driven by a ballast that is provided between an AC supply and the lamp, comprising means located in series between the AC supply and the ballast for inserting an auxiliary voltage, said auxiliary voltage being out of phase with said AC supply, whereby the supply voltage is the vectorial combination of a voltage applied to the ballast and the auxiliary voltage, such that the magnitude of the voltage applied to the ballast is smaller than the magnitude of the voltage of the AC supply, and further comprising means for controlling the auxiliary voltage for varying the voltage applied to the lamp, wherein the phase of the auxiliary voltage is maintained 90 or 270 degrees out of phase with a current flowing through said apparatus, and wherein the magnitude of the auxiliary voltage is used for varying the voltage applied to the lamp. ### Claim 2 (depends on 1) Apparatus as claimed in claim 1 wherein said means for inserting an auxiliary voltage comprises a power converter for generating said auxiliary voltage. ### Claim 3 (depends on 2) Apparatus as claimed in claim 2 wherein said power converter comprises a half-bridge inverter comprising two switches that are switched at high-frequency to generate a pulse-width-modulated (PWM) waveform as an output. ### Claim 4 (depends on 3) Apparatus as claimed in claim 3 wherein the PWM output of said half-bridge inverter is filtered to provide said auxiliary voltage. ### Claim 5 (depends on 3) Apparatus as claimed in claim 3 further comprising means to select a desired DC link voltage for the half-bridge inverter in order to control the magnitude of the auxiliary voltage. ### Claim 6 (depends on 5) Apparatus as claimed in claim 5 further comprising means to maintain said DC link voltage at a desired value. ### Claim 7 (depends on 6) Apparatus as claimed in claim 6 wherein a closed loop control scheme is used for maintaining said DC link voltage at said desired value and for maintaining the phase of said auxiliary voltage 90 or 270 degrees out of phase with said current. ### Claim 8 (depends on 2) Apparatus as claimed in claim 2 wherein said power converter comprises a full-bridge inverter. ### Claim 9 (depends on 1) Apparatus as claimed in claim 1 further comprising switch means whereby said apparatus may be by-passed if dimming control is not required and the voltage of the AC supply is applied directly to the ballast. ### Claim 10 An electrical lighting system comprising at least one lamp connected to an AC supply through a ballast, said system further comprising means for providing dimming control of said at least one lamp, said dimming control means comprising means located in series between the AC supply and the ballast for inserting an auxiliary voltage, said auxiliary voltage being out of phase with said AC supply, whereby the supply voltage is the vectorial combination of a voltage applied to the ballast and the auxiliary voltage, whereby the voltage applied to the ballast has a magnitude that is smaller than the magnitude of the voltage of the AC supply, and further comprising means for controlling the auxiliary voltage for varying the voltage applied to the lamp, wherein the auxiliary voltage is maintained at 90 or 270 degrees out of phase with a current flowing through said dimming control means, and wherein the magnitude of the auxiliary voltage is used for varying the voltage applied to the lamp. ### Claim 11 (depends on 10) A system as claimed in claim 10 wherein said dimming control means comprises a power converter for generating said auxiliary voltage. ### Claim 12 (depends on 11) A system as claimed in claim 11 wherein said power converter comprises a half-bridge inverter comprising two switches that are switched at high-frequency to generate a pulse-width-modulated (PWM) waveform as an output. ### Claim 13 (depends on 12) A system as claimed in claim 12 wherein the PWM output of said half-bridge inverter is filtered to provide said auxiliary voltage. ### Claim 14 (depends on 12) A system as claimed in claim 12 further comprising means to select a desired DC link voltage for the half-bridge inverter in order to control the magnitude of the auxiliary voltage. ### Claim 15 (depends on 14) A system as claimed in claim 14 further comprising means to maintain said desired DC link voltage. ### Claim 16 (depends on 15) A system as claimed in claim 15 wherein a closed loop control scheme is used for maintaining said DC link voltage at said desired value and for maintaining the phase of said auxiliary voltage 90 or 270 degrees out of phase with said current. ### Claim 17 (depends on 11) A system as claimed in claim 11 wherein said power converter comprises a full-bridge inverter. ### Claim 18 (depends on 10) A system as claimed in claim 10 further comprising switch means for bypassing said dimming control means if dimming control is not required and the voltage of the AC supply is applied directly to the ballast. ### Claim 19 (depends on 10) A system as claimed in claim 10 wherein said ballast is a magnetic ballast. ### Claim 20 (depends on 10) A system as claimed in claim 10 wherein said ballast is an electronic ballast of the type that enables a light to be dimmed by reduction of the AC input voltage to the ballast. ### Claim 21 (depends on 10) A system as claimed in claim 10 wherein said at least one lamp comprises a plurality of lamps. ### Claim 22 A method for providing dimming control of an electrical lamp driven by a ballast, comprising inserting an auxiliary voltage between an AC supply and said ballast, said auxiliary voltage being out of phase with the voltage of said AC supply whereby the supply voltage is the vectorial combination of a voltage applied to the ballast and the auxiliary voltage, wherein the auxiliary voltage is maintained 90 or 270 degrees out of phase with a current supplied to the ballast. ### Claim 23 (depends on 22) A method as claimed in claim 22 wherein the auxiliary voltage is generated by a power converter. ### Claim 24 (depends on 23) A method as claimed in claim 23 wherein said power converter comprises a half-bridge inverter including two switches that are switched at high frequency to generate a pulse-width-modulated (PWM) waveform as an output. ### Claim 25 (depends on 24) A method as claimed in claim 24 further comprising filtering the output of the half-bridge inverter to produce said auxiliary voltage. ### Claim 26 (depends on 24) A method as claimed in claim 24 wherein the magnitude of the auxiliary voltage is controlled by setting the DC link voltage of the half-bridge inverter. ### Claim 27 (depends on 26) A method as claimed in claim 26 further comprising maintaining the magnitude of the DC link voltage at a desired value. ### Claim 28 (depends on 23) A method as claimed in claim 23 wherein the power converter is a full-bridge converter.