# US 8,786,213 B2 · Compensating LED current by LED characteristics for LED dimming control > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,786,213 B2 - Document ID: US8786213B2 - Status: Granted - Kind: B2 - Application number: 13/706,219 - Filed: 2012-12-05 - Published: 2013-06-13 - Granted: 2014-07-22 - Earliest claimed: 2011-12-07 - Assignees: Richtek Technology Corporation - Applicants: Richtek Technology Corporation - Inventors: Shei-Chie Yang; Shui-Mu Lin; Jun-Sheng Cheng; Ming-Yu Lin; Chun-I Lin - Web page: https://patentgrep.com/patent/US8786213B2 ## CPC - H05B 47/10: Controlling the light source - H05B 45/14: using electrical feedback from LEDs or from LED modules - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract LED dimming control circuit and method compensate LED current or LED average current by LED characteristics to improve dimming efficiency and performance. LED characteristic related look-up tables are stored to provide compensation values, and input LED current setting information is compensated by the compensation values to generate corrected LED current setting information for determining LED brightness. ## Claims ### Claim 1 A LED dimming control circuit comprising: a register configured to receive and store a first LED current setting information; a storage unit connected to the register, configured to store a LED characteristic related look-up table and provide compensation values according to the first LED current setting information and the look-up table; and a compensator connected to the register and the storage unit, configured to compensate the first LED current setting information according to the compensation values to generate a second LED current setting information for determining LED brightness. ### Claim 2 (depends on 1) The LED dimming control circuit of claim 1, further comprising a second register connected to the compensator, configured to receive and store the second LED current setting information and provides the second LED current setting information at an output terminal of the LED dimming control circuit for adjusting LED current. ### Claim 3 (depends on 1) The LED dimming control circuit of claim 1, further comprising: second register connected to the compensator, configured to receive and store the second LED current setting information; and a PWM duty generator connected to the second register, configured to generate an output PWM signal according to the second LED current setting information stored in the second register, and provide the output PWM signal at an output terminal of the LED dimming control circuit for adjusting LED average current. ### Claim 4 (depends on 1) The LED dimming control circuit of claim 1, further comprising an interface circuit connected to the register and an input terminal of the LED dimming control circuit, configured to receive the first LED current setting information from an input terminal of the LED dimming control circuit and transmit the first LED current setting information to the register. ### Claim 5 (depends on 1) The LED dimming control circuit of claim 1, further comprising an interface circuit connected to the storage unit, configured to write or update the look-up table. ### Claim 6 (depends on 1) The LED dimming control circuit of claim 1, wherein the storage unit chooses the look-up table according to LED brightness data and LED temperature data. ### Claim 7 (depends on 1) The LED dimming control circuit of claim 1, further comprising a PWM duty detector connected to the register and an input terminal of the LED dimming control circuit, responsive to a clock signal to detect a duty of an input PWM signal at the input terminal of the LED dimming control circuit for generating the first LED current setting information. ### Claim 8 (depends on 7) The LED dimming control circuit of claim 7, wherein the PWM duty detector comprises: a sampling circuit responsive to the clock signal to sample the duty of the input PWM signal to generate a first sample value; a hysteresis circuit connected to the sampling circuit, configured to store a second sample value generated by the sampling circuit in a previous sampling process, and generate the first LED current setting information according to the first sample value, the second sample value, an upper bound and a lower bound; and a frequency detector connected to the hysteresis circuit, configured to detect a frequency of the input PWM signal to generate a detection signal for signaling the hysteresis circuit to adjust the upper bound and the lower bound; wherein if the first sample value is greater than the second sample value and the upper bound or if the first sample value is smaller than the second sample value and the lower bound, the first LED current setting information is determined according to the first sample value; otherwise, the hysteresis circuit maintains the first LED current setting information unchanged. ### Claim 9 (depends on 7) The LED dimming control circuit of claim 7, further comprising: a second register connected to the compensator, configured to receive and store the second LED current setting information; and a PWM duty generator connected to the second register, configured to generate an output PWM signal according to the second LED current setting information stored in the second register, and provide the output PWM signal at an output terminal of the LED dimming control circuit for adjusting LED average current. ### Claim 10 (depends on 9) The LED dimming control circuit of claim 9, wherein the PWM duty generator is responsive to the clock signal to control a varying speed of a duty of the output PWM signal according to the first LED current setting information received from the PWM duty detector. ### Claim 11 (depends on 1) The LED dimming control circuit of claim 1, wherein the compensator comprises a multiplier to multiply the first LED current setting information by the compensation values to generate the second LED current setting information. ### Claim 12 A LED dimming control method comprising: receiving and storing a first LED current setting information; providing compensation values according to the first LED current setting information and a LED characteristic related look-up table; and compensating the first LED current setting information according to the compensation values to generate a second LED current setting information for determining LED brightness. ### Claim 13 (depends on 12) The LED dimming control method of claim 12, further comprising adjusting LED current according to the second LED current setting information. ### Claim 14 (depends on 12) The LED dimming control method of claim 12, further comprising generating an output PWM signal according to the second LED current setting information for adjusting LED average current. ### Claim 15 (depends on 12) The LED dimming control method of claim 12, further comprising updating the look-up table. ### Claim 16 (depends on 12) The LED dimming control method of claim 12, further comprising choosing the look-up table according to LED brightness data and LED temperature data. ### Claim 17 (depends on 12) The LED dimming control method of claim 12, further comprising detecting a duty of an input PWM signal responsive to a clock signal for generating the first LED current setting information. ### Claim 18 (depends on 17) The LED dimming control method of claim 17, further comprising generating an output PWM signal according to the second LED current setting information for adjusting LED average current. ### Claim 19 (depends on 18) The LED dimming control method of claim 18, further comprising controlling a varying speed of a duty of the output PWM signal according to the first LED current setting information. ### Claim 20 (depends on 12) The LED dimming control method of claim 12, further comprising: sampling a duty of an input PWM signal responsive to a clock signal for generating a first sample value; determining an upper bound and a lower bound according to a frequency of the input PWM signal; and generating the first LED current setting information according to the first sample value, a stored second sample value, the upper bound and the lower bound; wherein if the first sample value is greater than the second sample value and the upper bound or if the first sample value is smaller than the second sample value and the lower bound, the first LED current setting information is determined according to the first sample value; otherwise, the first LED current setting information remains unchanged. ### Claim 21 (depends on 12) The LED dimming control method of claim 12, wherein the step of compensating the first LED current setting information comprises multiplying the first LED current setting information by the compensation values to generate the second LED current setting information.