Alternative IC for Constant Off Time PWM Current-Mode Controller for LED Applications

[localbroadcast]

Hello! I am building a circuit around the IC with part number ncl30105. It is a current-mode controller for driving LEDs. It uses current sensing and a constant OFF time to control the switching of an external mosfet. The OFF time is set by using an external resistor, so you can set the off time based on your specific needs. The current limit can also be set in the same way for whatever current your LEDs require.

I really like this device because it makes controlling the current to my LEDs relatively simple. If I want to dim the LEDs, there is also an enable pin that allows an outside PWM signal to turn the driver on and off independant from the constant current control.

The problem is that I can only find one seller of this chip and the price isn't all that great. If I could find an equivalent chip that basically does the same thing, I would love to hear about it. Anyone know of such a chip??

If it came down to it, I could always program a microcontroller to do the same function.. but that's a lot more complicated and not all that cheap either.

I've attached the datasheet for this chip.
Thanks for reading!

 

[BobK]

Perhaps the reason you are not finding many alternatives is that you are looking for one that is explicity current-mode. Any voltage-mode controller can be used for current control simply by using a sense resistor instead of a voltage divider to the voltage sense input. Typically they need 1.2V as the voltage feedback (as opposed to 1V on your controller), but I have even found some that require only 0.6V, which makes it more efficient for current control. If you are running only a single LED, even 0.6V can detract from your efficiency, but you could use an opamp to amplify the current sense voltage and bring it down to 10s of millivolts lost.

Bob