LED driver general requirements
Driving LEDs faces many challenges. For example, the forward voltage will change with temperature and current. The LED forward voltage of different individuals, different batches, and different suppliers will also vary. In addition, the color of the LED The point will also drift as the current and temperature change.
In addition, multiple LEDs are often used in applications, which involves the arrangement of multiple LEDs. Among the various arrangements, it is preferred to drive a single string of LEDs in series because this method provides excellent current matching performance regardless of how the forward voltage changes and how the output voltage (Vout) "drifts".
Power factor correction
Power Factor Correction (PFC) is mandatory for any power class specified by the US Department of Energy (DOE) ENERGY STAR Solid State Lighting (SSL) specification. This standard applies to a range of specific products, such as recessed lights, cabinet lights and table lamps, where the LED driver power factor for residential applications must be greater than 0.7, and for commercial applications greater than 0.9; however, this standard is a voluntary standard. The European Union's IEC61000-3-2 Harmonic Content Standard specifies the total harmonic distortion performance of lighting applications with power greater than 25 W, with a maximum limit equivalent to total harmonic distortion (THD) of 0.94.
While not all countries absolutely mandate improved power factor in lighting applications, some applications may have this requirement, such as utilities that promote commercial applications of products with high power factor in utilities, and utilities. When an organization purchases/maintains a street light, it can also decide whether it is required to have a high power factor (usually >0.95+) according to their wishes.
Figure 1: Schematic diagram of the application circuit of active PFC
PFC technology includes both passive PFC and active PFC. Passive PFC solutions are bulky and require additional components to better change the current waveform to achieve a power factor of about 0.8 or higher. Among them, in lower power applications of less than 5 W to 40 W, almost the standard choice of flyback topology requires only passive components and minor circuit modifications to achieve a power factor greater than 0.7.
The active PFC (see Figure 1) is typically added to the circuit as a dedicated power conversion section to change the input current waveform. Active PFCs typically provide boost, with a wide input range of 100 to 277 Vac, and a PFC output voltage range of 450 to 480 Vdc. If the PFC section is properly designed, it can provide 91% to 95% energy efficiency. However, with the addition of active PFC, a dedicated DC-DC conversion is still required to provide current regulation.
Frequency inverters for 3-phase asynchronous motors from 1 to 700 HP, constant torque applications for 575-690V applications. For 230V and 460V drive applications consider the new Altivar Process ATV900 drive family.
Inverter 3 Phase,Electric Frequency Converter,High Power Electric Inverter,Schneider Inverter 3 Phase
Wuxi Trenty Machinery & Equipment Co., Ltd. , https://www.elec-inverter.com