Adapt DC Voltage To Perform PWM DImming Of High-Brightness LEDs

Focus:

Hysteretic controllers used to drive high-brightness LEDs typically have a PWM input for dimming control. Traditional dimmers produce a 1- to 10-Vdc signal, which must be converted to a PWM signal for use with a hysteretic controller. Although the conversion of dc to PWM is simple, it's difficult to make PWM duty cycle vary linearly with control voltage. A quad op amp forms the basis of a control circuit that accomplishes this task.

What you’ll learn:

• How to convert a dc dimming control voltage to a PWM signal for dimming high-brightness LEDs
• How to make a PWM signal's duty cycle vary linearly with a dc control voltage

Notes:

ED's Ideas For Design

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Author & Publication:

Jim Christensen, strategic application engineer, Maxim Integrated Products Inc., Sunnyvale, Calif., Electronic Design, Jun 26 2008

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