Regs (regards not regulator)
Malcolm
,
This above picture is the typical application circuit of LM431, it shows us how to adjust VKA. If we replace R1 with LEDs, LEDs current will be adjusted by R2 and Vref. If Vref and R2 is constant, LEDs current will be constant too
From efficiency point, maybe only LM431 is not a good solution because input resistor will share more power dissipation.
This is the circuit I would normally use to generate a constant current of about 25mA. The input voltage is anything up to 37volts. The required resistor is calculated (roughly) by 1.2 volts divided by the current required. Eg 1.2V/.025A= about 47 ohms Resistor power is Voltage squared/Resistance (eg 1.2*1.2/47ohms = 30mW) OR Current*Current*Resistance The power disipitation in the LM317 is of course the voltage drop across it multiplied by the current flowing through it (eg same current as going through your LED, "current through a series circuit is the same")
NOTE:-47 ohm resistor used
LM317 (small TO-92 packages) http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=BBVYM0BUEM3HMCQLCIPZK0Q?N=551&Ntk=gensearch_001|gensearch_001&Ntt=lm317|to-92&Ntx=&displaytext=&_requestid=163594
your solution is only for small power LED driver.How about Power LED(350mA current or more ) for resistor will result in lower efficiency
Hello!
If a 24VAC power supply, can be solved with the LM317 and the MOSFET controller. The solution is to link http://www.sper.hr/eng/wld.htm.Works for years. No inductors. Effiency about 70%. It can be used 1..8 LED. |
Hello!
If a 24VAC power supply, can be solved with the LM317 and the MOSFET controller. The solution is to link http://www.sper.hr/eng/wld.htm.Works for years. No inductors. Effiency about 70%. It can be used 1..8 LED. |
