Lighting
Street lighting |
The suggested power MOSFETs for PFC and HB-LLC are the same |
Energy efficiency, a long lifetime, remote control, small form |
proposed before for the related stages of single string case, while |
factor, and extended temperature range(-40 ° C) are the main |
for the buck and reverse buck, the 60-100V low-voltage STripFET |
requirements for the LED street lighting market, and usually |
F7 power MOSFETs series can be adopted. As for the output |
require more than 75W. |
diodes, we propose the STPS schottky diodes, the FERD field |
For single string architectures, we often implement the primary |
effect rectifier and the Ultrafast diodes series( STTH with ≥ |
side regulation costant current( PSR-CC) control technique using a |
200V) in the HB-LLC, buck and reverse buck circuits. For the PFC |
digital approach with a PFC regulator followed by a HB-LC |
stage the same ones reported in the single string case can be |
resonant stage( fig. 8). |
used. |
For both stages( power and LED control), ST offers analog and |
digital driving solutions. |
Fig. 8 – Digital single string PSR-CC LED driver
In this case, the LED driver architecture is based on two stages— PFC and HB-LC circuits( fig. 8) and a single digital IC can manage both. For the single digital IC, ST offers the STLUX, a new series of dedicated digital lighting controllers, as well as several STM32 high-performance microcontrollers.
Different power MOSFETs are suggested for each of the two stages:
Ÿ PFC( boost): the 600-650Vbr MDmesh M2 series or the 600V MDmesh M2-EP series. Both families have an extremely low Qg and are optimized for light load conditions. The M2- EP is tailored for high fsw.
Ÿ HB-LC: the 500-600Vbr MDmesh DM2 series, the 600Vbr MDmesh M2 series, or the 600V MDmesh M2-EP series. The DM2 series has an improved trr of intrinsic diode and high dV / dt capability.
Concerning output rectification, the 600V ultrafast series STTH 06 is suggested for PFC( both TM and CCM), while the STPSC silicon carbide diodes are suggested only for the PFC-CCM. For the HB- LC, the suggested output diodes are the same as the ones reported previously in the commercial single string approach.
The multiple strings power supply architecture consists of a main power supply providing a constant bus voltage and a subsequent multiple strings( fig. 9). Usually the main power stage, consisting of a high power factor correction( PFC) stage combined with an LLC resonant converter, provides the constant voltage bus. The subsequent LED strings control is implemented by multiple buck or reverse buck converters.
Fig. 9 – Analog multiple strings architecture based on Combo controller
Fig. 10 – Digital solution
ST’ s offerings for these two digital ICs are the same ones reported in the single string case, and the STM8 family microcontroller can also be used for the reverse buck of the secondary side.
STEVAL-ILL066V1 100W, digital single-string PSR-CC LED driver
STEVAL-ILL078V1 60V-1A, buck LED driver converter
STEVAL-ILL053V1 130W, analog power supply for LED Driving
Fig. 11 – Main system evaluation boards for street lighting
STEVAL-ILL056V1 48V-3A, buck LED driver converter
The gate drivers suggested for PFC and HB-LLC are the same mentioned in the single string case; in the reverse buck scenario, the gate drivers mentioned in the commercial digital LED multiple strings management case are appropriate.
A wide array of system evaluation boards for street lighting single and multiple strings are available. Some of these are shown in fig. 11. Also, the STEVAL-ILL074V1 / V2( 60W analog power supply for LED driving) and STEVAL-ILL077V1( 60W digital multiple-string LED driver) shown in fig. 7 are appropriate for street lighting applications.
The eDesignSuite software tool The eDesignSuite is an easy-to-use, comprehensive software suite ready to help customers define their needs by transforming their application requirements into satisfactory solutions based on the wide range of ST products. The suite includes
ELE Times | 55 | March, 2017