Motore di ricerca datesheet componenti elettronici |
|
744772100 Scheda tecnica(PDF) 7 Page - NXP Semiconductors |
|
744772100 Scheda tecnica(HTML) 7 Page - NXP Semiconductors |
7 / 21 page UM10406 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2010. All rights reserved. User manual Rev. 01 — 3 August 2010 7 of 21 NXP Semiconductors UM10406 SSL1523 5 W LED driver 6. Board system optimization To meet specific customer application requirements, the modifications described in the following sections are possible. 6.1 Changing the output current and LED current One of the major advantages of a flyback converter over other topologies, is its suitability for driving LED configurations with a broad range of voltages. Essentially, changing the winding ratio whilst maintaining the value of the primary inductance, will shift the output working voltage accordingly. Part of the efficiency of the driver is linked to the output voltage. A lower output voltage will require increased transformation ratio, and will cause higher secondary losses. In practice, a mains operated flyback converter will have an efficiency > 80 % for high output voltages (like 40 V) down to 50 % for very low output voltages < 3 V. At low voltages, synchronous rectification becomes advisable to reduce rectification losses. The NXP TEA 1761/TEA1762 can be used for this purpose, see Ref. 1. For exact calculations of transformer properties and peak current, refer to Ref. 2 application note AN10754, “How to design an LED driver using the SSL2101”, see Ref. 2. 6.2 Changing the output ripple current The output ripple current is mostly determined by the LED voltage, the LED dynamic resistance and the output capacitor. The present value of C10 has been chosen to optimize the capacitor size under typical load. The resulting ripple of ± 30 % will result in an expected deterioration of light output < 1 %. The size for the buffer capacitor (C10) can be estimated from Equation 1: (1) Using a series of LEDs, the dynamic resistance of each LED can be multiplied by the number of LEDs. The current sense resistor (R10) should also be included in this calculation. Example: For a ripple current of ± 30 %, and a mains frequency of 50 Hz, and a total dynamic resistance of 7 Ω, the resulting capacitance value will be 3.3333 / (314*7) = 1500 μF. The capacitor must be specified for the HF switching related ripple current of about 0.35 times the average effective LED current (ILED(AV)). For high lifetime applications, the ripple current specification of the electrolytic capacitor must be increased. For details, please contact the capacitor supplier. 6.3 Changing the load curve The current load curve can be divided into the following two regions: • Where the current control loop regulates the output current, the constant current output • Where the IC limits the peak input current of the converter, the constant power output C 10 I ΔI ------ 1 2 πf net R dynamic ⋅ ---------------------------------------- ⋅ = |
Codice articolo simile - 744772100 |
|
Descrizione simile - 744772100 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEETIT.COM |
Lei ha avuto il aiuto da alldatasheet? [ DONATE ] |
Di alldatasheet | Richest di pubblicita | contatti | Privacy Policy | scambio Link | Ricerca produttore All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |