LM3447 Phase Dimmable, Primary Side Power Regulated, PFC Flyback Controller for LED Lighting | TI.com

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Phase Dimmable, Primary Side Power Regulated, PFC Flyback Controller for LED Lighting



The LM3447 is a versatile power factor correction (PFC) controller designed to meet the performance requirements of residential and commercial phase-cut dimmer compatible LED lamp drivers. The device incorporates a phase decoder circuit and an adjustable hold current circuit to provide smooth, flicker free dimming operation. A proprietary primary side control technique based on input voltage feedforward is used to regulate the input power drawn by the LED driver and to achieve line regulation over a wide range of input voltage. Valley switching operation is implemented to minimize switching loss and reduce EMI. An internal thermal foldback circuit is provided to protects the LEDs from damage based on the temperature sensed by a single external NTC resistor. Additional features include LED open circuit and short circuit protection, cycle-by-cycle FET over-current protection, burst mode fault operation using an internal 812ms fault timer and internal thermal shutdown.

The LM3447 is ideal for implementing dimmable, isolated single stage LED lamp drivers where simplicity, low-component count and small solution size are of primary importance. This device is currently available in a TSSOP 14-pin package.


  • Integrated Phase Angle Decode
    • Leading and Trailing Edge Compatible
    • Over 50:1 Dimming Range
  • Power Factor Correction with Low Total Harmonic Distortion
  • Primary Side Control Using Input Voltage Feedforward Technique
  • Input Power Regulation Scheme with Improved Line Regulation
  • Constant Power Operation of LEDs to Compensate for Forward Voltage
    Variations Over Temperature and Lifetime
  • Fixed Frequency Discontinuous Conduction Mode Operation
  • Valley Switching Operation to Achieve High Efficiency and Low EMI
  • Efficient TRIAC Hold Current Management
  • Thermal Foldback Function for LED Protection
  • LED Open Circuit and Short Circuit Protection


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Part number Order Input voltage (type) Vin (Min) (V) Vin (Max) (V) Iout (Max) (A) Vout (Min) (V) Vout (Max) (V) Regulated outputs (#) Topology Dimming method Power factor correction (Min) Type Switching frequency (Min) (kHz) Switching frequency (Max) (kHz) Iq (Typ) (mA) Vref (V) UVLO thresholds on/off (V) Features Operating temperature range (C) Package Group Package size: mm2:W x L (PKG)
LM3447 Order now AC/DC     7.5     17.5     2     9     60     1     Flyback     Forward Phase (Triac)
Reverse Phase    
Active     Inductive     60     120     1.6     1     10.5 / 7.5     Adjustable Switch Frequency
Soft Switching
Thermal Shutdown    
-40 to 125     TSSOP | 14     14TSSOP: 32 mm2: 6.4 x 5 (TSSOP | 14)    
LM3445 Order now AC/DC     8     12     2     9     60     1     Buck
Forward Phase (Triac)
Reverse Phase    
Inductive     30     1000     2     0.75     7.4 / 6.4     Adjustable Switch Frequency
Thermal Shutdown    
-40 to 125     SOIC | 14
VSSOP | 10    
14SOIC: 52 mm2: 6 x 8.65 (SOIC | 14)
10VSSOP: 9 mm2: 3 x 3 (VSSOP | 10)    
TPS92075 Order now AC/DC     11     18     2     9     120     1     Buck
Forward Phase (Triac)
Reverse Phase    
Active     Inductive     50     300     1.3     0.5     9.8 / 6.4     Adjustable Switch Frequency
Soft Start
Thermal Shutdown    
-40 to 125     SOIC | 8
SOT-23-THIN | 6    
8SOIC: 19 mm2: 3.91 x 4.9 (SOIC | 8)
6SOT-23-THIN: 5 mm2: 1.6 x 2.9 (SOT-23-THIN | 6)