DW8533 Non-Isolated Buck LED Regulator With PFC and High Voltage MOSFET

DONGWOON-DW8533 Order information

DW8533 Non-Isolated Buck LED Regulator With PFC and High Voltage MOSFET General Description:

The DW8533 is a constant current LED regulator with high current accuracy which applies to single stage  step-down power factor corrected LED drivers. 600V power MOS is integrated, which can significantly  simplify the design of LED lighting system.

High accuracy of output current is achieved by sampling the output current directly. Critical conduction mode operation reduces the switching losses and largely increases the efficiency. DW8533 is  supplied from the output directly, and auxiliary winding is not needed.  

DW8533 has multi-protection functions which largely enhance the safety and reliability of the system,  including VCC over-voltage protection, VCC UVLO, short-circuit protection, LED open protection, cycle-by-cycle current limit and over-temperature protection.

Non-Isolated Buck LED Regulator With PFC and High Voltage MOSFET DW8533 Features:

●No auxiliary winding；

●600V High voltage MOSFET integrated；

●High Current accuracy of line and load regulation ；

●High power factor with low output current-ripple；

●Critical conduction mode ;

●High efficiency over wide operating range;

●Cycle by Cycle current limit;

●LED short protection ;

●LED open protection ;

●Over-temperature protection;

●Compact SOP7 Package;

Non-Isolated Buck LED Regulator With PFC and High Voltage MOSFET DW8533 Applications:

●AC/DC LED driver applications

●Signage and decorative LED lighting

●General lighting of flat panel displays

●RGB backlight

●General purpose constant current source

●IBulb light

Non-Isolated Buck LED Regulator With PFC and High Voltage MOSFET DW8533 Pin Information

DW8533 Block Diagram:

DW8533 Typical Application Circuit:

Absolute Maximum Ratings⁽¹⁾

Note 1. Exceeding these ratings may damage the device.

         2. Measured on JESD51-7, 4-layer PCB.  

         3. The DW8533  guarantees  robust  performance  from -40°C  to 150°C  junction  temperature.  The  junction temperature  range  specification  is  assured  by  design,  characterization  and  correlation  with  statistical process controls.  

        4. The DW8533 includes  thermal protection  that  is  intended to  protect  the  device in overload  conditions. Thermal protection  is  active when  junction  temperature  exceeds  the  maximum  operating  junction temperature.  Continuous  operation over the  specified  absolute maximum  operating  junction  temperature may damage the device.

Absolute Maximum Ratings

     Use  of  the  IC  in  excess  of  absolute  maximum  ratings  such  as  the  applied  voltage  or  operating  temperature range (T_J) may result in IC damage. Assumptions should not be made regarding the state of the IC (short mode or open mode) when such damage is suffered. The implementation of a physical safety measure such as a fuse should  be  considered  when  use  of  the  IC  in  a  special  mode  when  the  absolute  maximum  ratings  may  be exceeded is anticipated.

DW8533 Recommended Operating Condition

DW8533 Typical Operating Characteristics

(V_IN=85VAC~264VAC, V_OUT=67V, Io=320mA, ,unless otherwise noted)

DW8533 Detailed Descriptions

  The DW8533 is  a  constant  current  LED  regulator  which  applies  to  non-isolation  step-down  LED  system with power factor correction. 600V power MOS is integrated, which can significantly simplify the design of LED lighting system. DW8533 can achieve excellent line and load regulation, high efficiency and low BOM cost.

Start Up

 When the pull-up resistor charges VCC up to 21V, the gate drive signal begins to switch, and the output begins to provide power to the VCC pin when the output is enough. An internal voltage clamp is attached to the VIN pin to prevent VCC from being too high. An internal 10mA current pulls the VCC down and stop switching when it is above 43V  and  restart  switching  when  VCC  is  pulled  down  to 35V.  When  VCC  is  lower  than  7.7V,  it  stops switching.

Loop Compensation

 An  integrator  configuration  is  applied  to  the  output  current  feedback  loop  with  a  capacitor  connected  to  the COMP pin. For offline applications, the crossover frequency should be set much less than the line frequency of 120Hz  or  100Hz.  To  have  a  good  PFC  performance,  a  capacitor  of  0.1μF  connected  to  COMP  pin  is recommended.

LED Over Temperature Protection

When DW8533 is hotter than 150°C, the chip stops switching, thus the output current decreases to zero; when the temperature is decreased to 135°C, the chip starts switching again.

LED Open Protection

  The  output  voltage  can  be  detected  by  the  FB  pin.  When  the  FB  voltage  is  higher  than  3.0V,  the  LED  open protection  is  triggered  and  the  power  MOSFET  gate  driver  stops  switching.  After  several  seconds,  the  gate driver starts switching again.

 The  recommended  FB  pin  voltage  is  about 2.5V  at  rated  output，and  it’s  pull-up  resistor  is  typically  in hundreds KΩ level.

LED Short Protection

  DW8533 judges LED short from the FB voltage. During a shorted LED condition, DW8533 reduces the internal command  current  to  a  very  low  level  and  slows  down  the  switching  frequency  to 1.25  kHz to  decrease  the output current.

 If  LED short or  LED open  protection  are  false  triggered  by unreasonable  PCB  layout, a  20pF  capacitor paralleled to FB pin and GND can solve the problem.

PCB Layout Guidelines

1.  DW8533 The VCC pin must be locally bypassed with a capacitor.

2.  Make the area of the power loop as small as possible in order to reduce the EMI radiation.

3.  The chip should be far away from the heating components, such as MOSFET, transformer and diode.

4.  Note the chip ground is not connected to the cathode of the input capacitor as usual.

Application Reference

VIN:       90VAC~264VAC

VOUT:   32~65V

IOUT:     320mA

PF:       >0.9

Key words of this article：DW8533, Non-Isolated, Buck LED Regulator ,High PFC,  High Voltage MOSFET