Info about constant current control for parallel LEDs

[liuyonggen_1]

Could you tell me the kinds of constant current control about parallel LED?
Thanks for your help!

 

[szekit]

Re: about LED!

what is parallel LED?

i used high-swing cascoded current source to get the high voltage swing and high output resistance.

are u driving a few LEDs or a bunch (i.e., display)? watch out for process variation on Vt if u are driving a display.

 

[liuyonggen_1]

Re: about LED!

Thanks for your reply!
In fact, I would like to know some control techniques or ways to adjust the brightness of the LED. For example, PWM control, LDO control and digital control or discrete look-up table control.

 

[stoned]

Re: about LED!

attachment's paper may be help you

 

[DrWhoF]

Re: about LED!

**broken link removed**

https://www.electronics-lab.com/projects/games/003/index.html

 

[elantra]

about LED!

Normally parallel LEDs are drived by charge pump circuit, and the driver seems like paralleled LDOs. Use resistor to sample the current to keep the current constant. sometimes it is diffuricult to keep the leds the same brightness. current match of 0.006 is quite a commerical value. Some companies such as linear tech provide such products, you can search and have a look.

 

[liuyonggen_1]

Re: about LED!

Normally parallel LEDs are drived by charge pump circuit, and the driver seems like paralleled LDOs. Use resistor to sample the current to keep the current constant. sometimes it is diffuricult to keep the leds the same brightness. current match of 0.006 is quite a commerical value. Some companies such as linear tech provide such products, you can search and have a look.

Thanks for your suggestions!
could you tell me whether LED adjusts the brightness by using different voltage reference(keeping the resistor constant) or by changing the resistance while keeping the voltage reference constant?

Added after 10 minutes:

Thanks for your self-giving help!

I have two questions

For discrete brightness control
whether LED adjusts the brightness by using detect resistor network while keeping voltage reference (voltage drop on the detect resistors) constant or by changing the value fo voltage reference while keeping the detect resistor constant?

For PWM control
how to adjust the brightness of the LED continuously? could you show me some detailed circuit structures and its principles?

Added after 17 minutes:

could someone tell the principle of some parts of MAX1537 shown with PDF?

The most-left part:
the terminal SET connected with a set resistor, could you tell me the role of the two PMOS especially the right PMOS?

 

[liuyonggen_1]

Re: about LED!

Help me!

could someone give me some detailed circuits about the control part of adjusting the brightness for LED?

E-Mail: liuyonggen_1@163.com

 

[gharibe_12000]

Re: about LED!

hi ,
this pdf files are very good . tnx 4 u .
:idea: