Datasheet Linear Technology LT8391

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Design Notes

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  60V Buck-Boost LED Driver with Up to 98% Efficiency Has Internal PWM Dimming and Spread Spectrum &mdash DN548
  PDF, 216 Kb, File published: Feb 1, 2016
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  60V Buck-Boost LED Driver with Up to 98% Efficiency Has
  Internal PWM Dimming and Spread Spectrum – Design Note 548
  Keith Szolusha
  The LTВ® 8391 60V four-switch buck-boost LED driver
  is designed to drive high power LEDs up to 250W and
  to flawlessly transition between two-switch boost,
  four-switch buck-boost, and two-switch buck regions
  of operation. A patent pending four-switch buck-boost
  current-sense resistor control scheme provides a
  simple, yet masterful method for the IC to run in peak
  current mode control in all regions of operation with
  a single sense resistor. This new generation buckboost LED driver features spread spectrum frequency
  modulation and internally generated PWM dimming,
  which work together. The LT8391 has flicker-free
  PWM dimming with both internal and external PWM
  dimming, even when spread spectrum is turned on
  (another patent pending technique). Synchronous buck-boost converters with four power
  switches can deliver very high efficiency while providing both step-up and step-down DC/DC conversion.
  Combining the capabilities of two separate converters (buck and boost) has the advantage of reduced
  solution size and cost. Four-switch converters should
  be able to operate with just two switches for highest
  efficiency when only step-up or step-down conversion is needed. However, they must also be able to
  utilize four-switch operation as VIN and VOUT approach …

Articles

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  Buck-Boost LED Driver Reaches 98% Efficiency, Features Internal PWM Dimming and Spread Spectrum without Flicker &mdash LT Journal
  PDF, 2.3 Mb, File published: Feb 8, 2016
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  Buck-Boost LED Driver Reaches 98% Efficiency, Features
  Internal PWM Dimming and Spread Spectrum without Flicker
  Keith Szolusha Four-switch converters combine two converters (a buck and boost) into a single
  converter, with the obvious advantage of reduced solution size and cost, plus relatively
  high efficiency conversion. High performance 4-switch converters have carefully
  designed control schemes. For instance, for highest efficiency, a 4-switch converter
  should operate with only two switches when only step-up or step-down conversion
  is needed, but bring in all four switches as VIN approaches VOUT. A well-designed
  buck-boost converter gracefully transitions between the three regions of operation—
  boost, buck and buck-boost—by taking into account the challenge of combining
  three control loops—2-switch boost, 2-switch buck and 4-switch operation.
  Figure 1. LT8391 4V–60V 4-switch synchronous
  buck-boost LED driver powers a 25V, 2A (50W)
  string of LEDs at up to 98% efficiency. L1
  4.8ВµH 0.004О© 10О© The LT8391 60V 4-switch buck-boost LED
  driver is designed to drive high power
  LEDs and to flawlessly transition between
  2-switch boost, 4-switch buck-boost, and
  2-switch buck regions of operation. 10О©
  10nF VIN
  4V TO 60V 0.1ВµF M1 + 47ВµF 4.7ВµF
  63V 100V
  Г—2 SW1 LSP LSN SW2 BST1 BG2 GND TG2 VIN VOUT INTVCC …

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Manufacturer's Classification

• Power Management > LED Driver ICs > Buck-Boost LED Drivers