STEVAL-LLL004V1 Data brief 75 W digitally controlled constant current LED driver reference design Features Wide input voltage range 85 265 V AC Transition Mode PFC Two constant current outputs working in transition mode based on different topologies: Buck topology Inverse buck topology Output current: 500 mA 2.5% Number of LEDs connected at output: 16 24 white LEDs (3.3 V each) PFC > 0.97 and THD < 20% at full load with input voltage 85-265 V AC Peak Efficiency at maximum load 90% Comprehensive safety protections: Open/no-load circuit protection Short-/overload circuit protection Soft start implementation LED dimming range: 0.5% to 100% Analog dimming Digital dimming Dimming control options: Push button 0-10 V input Summary table Meets EN55022 Class B STEVAL-LLL004V1 WEEE and RoHS compliant STEVAL-LLL004V1 evaluation board Mainstream ARM Description Cortex-M0 Access line MCU with 128 The STEVAL-LLL004V1 digitally controlled constant current LED driver reference STM32F071CBT6 Kbytes Flash, 48 design features a PFC stage and two DC-DC converters designed to work in MHz CPU and CEC transition mode (TM) for optimal efficiency. functions The LED driver can deliver 75 W output power and implements both analog and N-channel 600 V, digital techniques for flicker free dimming down to 0.5% of the maximum brightness 0.550 typ., 7.5 A level. The board features high efficiency, a very high power factor above 0.97, and a MDmesh M2 EP STD11N60M2-EP low THD across wide input voltage and load conditions, thanks to the high Power MOSFET in a DPAK package performance ST power products and the advanced algorithms running on the 32-bit STM32F0 microcontroller. VIPerPlus family: Low voltage energy saving fixed VIPER012LS frequency high voltage converter DB3630 - Rev 2 - July 2019 www.st.com For further information contact your local STMicroelectronics sales office.STEVAL-LLL004V1 LED driver reference design overview 1 LED driver reference design overview The principal design objectives of this LED driver board are to deliver considerable performance in terms of efficiency (90%), power factor (>0.97), THD (<20%), wide dimming range (down to 0.5%) and EN55022 EMC pre- compliance, as well as facilitate design optimization over a wide range of operating points with little or no hardware configuration. A reference design based on digital algorithms supported by a programmable STM32 microcontroller therefore seemed to be the ideal solution. The implementation of digital control as opposed to analog is gaining popularity in power conversion circles for its superior flexibility regarding control loop parameter and on-the-fly operating point adjustment for any given condition, without needing to modify the hardware. Additionally, digital control ensures greater stability under noisy conditions and tends to be less sensitive to component tolerances, temperature variations and voltage drift. An appropriate programmable digital controller can also simplify the implementation and customization of advanced lighting solution features like flicker-free, high-resolution dimming, connectivity for remote control and dimming, diagnostic protection and monitoring. Figure 1. STEVAL-LLL004V1 block diagram 85 - 265V AC Mains Buck Connector PFC DC-BUS Bridge STD11N60M2-EP LED string Filter Rectifier PM8841 gate driver PFC I/P voltage PFC gate drive MCU PFC O/P voltage PFC ZCD PFC overcurrent Buck zcd STM32F0 L6395 Buck gate drive I-buck zcd HS gate driver short circuit, open circuit STM32F071CB push buttons NTC I buck gate drive 0-10V Inverse buck Connector LED string PM8834 gate driver STD11N60M2-EP Auxilliary Supply The digital controller chosen for the STEVAL-LLL004V1 LED driver reference design is the STM32F071CB microcontroller featuring a generous set of hardware peripherals. The MCU controls the PFC, the buck and inverse-buck DC-DC power conversion stages in transition mode (TM), which maximizes efficiency by turning the Power MOSFET switch ON as the current in the inductor reaches zero, and implements both analog and digital dimming. The advanced control timer (TIMER1) in STM32F071CB can work together with the other timers via the Timer Link feature for synchronization or event chaining, simplifying the task of the designer. The PFC provides a regulated high-voltage DC rail and ensures that the current drawn from the mains is highly sinusoidal and in phase with mains voltage. A proportional-integral (PI) control loop is included in the PFC stage DB3630 - Rev 2 page 2/8