LM3402 showing unusual response

[chirag2239]

Hello,

I am creating an LED driver using LM3402HV. When I connect the circuit as shown in attached datasheet, it shows unusual response.

When I connect the R(ON) resistor to pin 7 and then measure the voltage on PIN 8, it reduces to 7V from 40V. My VIN voltage is 40V. My requirement is 36V/480mA. What I need to do to maintain the Vin at 36V on this pin? The value of Ron is 220K. I am driving a strip of 96 LEDs. 12 in series and 8 columns of 12 series connected LEDs in parallel. Do I need a higher capacity power supply?

I have created whole Circuit but at the output, I am getting only 5V. What to do?

Then I disconnected all the parts and one by one, I checked all the components and its voltage, then the problem is same as before. Why the voltage is getting down? Is there any problem in this design? Do I need to increase the input voltage?

Please help me to solve this issue.

Thanks.
Chirag

 

[KlausST]

Hi,

measure the voltage on PIN 8, it reduces to 7V from 40V. My VIN voltage is 40V.

Pin8 is V_In voltage, how can it be it reduces to 7V when you say your input voltage is 40V?

In doubt connect a 200k resistor between pin8 (V_in) and pin6 (RON) as recommended in the datasheet.

This circuit is not suited for a breadboard.

Klaus

 

[chirag2239]

Hello,

I have achieved the voltage by changing the R(ON) resistor. I have obtained 32V at output. But when I tried to connect LED Tubelight, it did not worked.

Here is the complete schematic of my circuit. Please help me to solve this issue.

Thanks.
Chirag

- - - Updated - - -

The resistor I have changed to R(On) is of 330k. Please ignore 59k in schematic.

- - - Updated - - -

Yes, I have done one test. I have supplied the rectified DC voltage. It is 40V. But still its not working. My tubelight is having 105 LEDs in strip. I think the current is not sufficient for this because the LED glows with very poor intensity. Its too low so I think I need higher current source. Even though I need suggestions from you guys.

Thanks.
Chirag