Lm317 need at least 3v higher than the output. My source is only 3.7v and vf of the led is 3~3.5v. So it would not work. Unless if there is a way to amplify the volts before lm317.Can you draw your circuit using correct symbols and not blocks, you would be better using a Lm317 as a current driver.
How to check tour library. And is this circuit OK? Or it need changes? If need changes I will first study your library. But how to get into your library.If you check out my library I have several ways to do this.
i used it to increase the voltage. it is given in datasheet that the voltage can be set from Vref (2.5v) upto 30V. Please correct me.Your circuit wont work, as a TL431 has an internal reference of 2.5v, your better off supplying the led direct from the power with a transistor and diodes.
If you check out my library I have several ways to do this.
I would do this with a transistor and a couple of diodes.
I'll sketch something up.
I did not understand.V_R4=300mA*0.33Ω=0.099V.
The V_R1 is quite low, so the current flows through the R1,R2 and Pot also will be low, and the range of (+) input voltage should be around 0.08V~0.2V or some more range.
R3 was in parallel, using it to get a lower voltage, and sometimes was used it to avoid the (+)input floating when the pin 2 of pot is disconnect.I did not understand.
According to what I studied with my own self reading here and there
the shunt regulator getting very low current due to R1 and that will be iR1= 3v/660 = 4.54mA. and due to R2 and pot the shunt regulator outputs voltage = Vref * (1+R2/Pot) = 2.5 * (1+10k/10k) = 5V.
The current gain of d882 is 150.
so if the current input receiving by d882 is 4.54ma. the current flow from collector to emitter is 150 times 4.54mA.
ie. 4.54*150 = 681mA. I don't know what is the use of R3 and R4. and what is the use of lm358 there? if it is just acting as switch.
how much voltage will be near - pin of lm358? how to calculate the voltage near - pin. and if positive pin is more than the negative pin. the output will be 3v right?R3 was in parallel, using it to get a lower voltage, and sometimes was used it to avoid the (+)input floating when the pin 2 of pot is disconnect.
So if we don't care the R3, then V_pot = 3V/(R1+R2+Pot)=3V/(680Ω+20K+10K)=0.097mA=97uA.
You can calculate the voltage of pot and the voltage of (+) input.
Using R4 to get a voltage to comparing with the (+)input.
Let me explain what I am doing. before that. I have to thank you for teaching me and taking your time for me. May God bless you.I just uploaded the circuit to be your reference, you may check it and modify it to suit your application.
View attachment 80457
Thread starter | Similar threads | Forum | Replies | Date |
---|---|---|---|---|
K | Testing of a M5450B7 LED Driver | General Electronics Chat | 2 | |
E | Failed Led Driver Advice/help | Technical Repair | 8 | |
Dual BJT constant current driver help | General Electronics Chat | 14 | ||
rotary encoder line driver output | General Electronics Chat | 3 | ||
S | LED driver Feedback line diode | Homework Help | 4 |