Invention Grant
- Patent Title: Driving multiple parallel LEDs with reduced power supply ripple
- Patent Title (中): 驱动多个并联LED,降低电源纹波
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Application No.: US12099729Application Date: 2008-04-08
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Publication No.: US07843148B2Publication Date: 2010-11-30
- Inventor: Christian Gater , Roel Van Ettinger
- Applicant: Christian Gater , Roel Van Ettinger
- Applicant Address: US CA San Jose
- Assignee: Micrel, Inc.
- Current Assignee: Micrel, Inc.
- Current Assignee Address: US CA San Jose
- Agency: Patent Law Group LLP
- Agent Brian D. Ogonowsky
- Main IPC: H05B37/02
- IPC: H05B37/02

Abstract:
An LED driver is disclosed that drives LEDs connected in parallel. Instead of applying current to all the parallel-connected LEDs at the same time, under control of a common PWM brightness control signal, the application of current to each parallel path is staggered by using staggered brightness control signals. The turning on of the LEDs in the different parallel paths will have the same duty cycle but will be out of phase. This reduces ripple in the power supply by reducing the magnitude of the instantaneous current sink. In one embodiment, a shift register contains a binary representation of the PWM duty cycle, and a clock shifts the bits along the shift register. The PWM brightness control signals for each parallel path of LEDs are tapped from different positions along the shift register so that the PWM brightness control signals are identical but staggered.
Public/Granted literature
- US20090251071A1 Driving Multiple Parallel LEDs with Reduced Power Supply Ripple Public/Granted day:2009-10-08
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