# Question about HV9910B Led driver

#### ir_tronik

Joined Jul 12, 2017
16
I have a design on LED driver circuit that using HV9910B.
My input is 7V - 30V
I want to drive a single LED that has a Forward voltage of 2.1V with 350mA

Is it correct if I design the output voltage minimum is 3V? do I need to add another resistor in series?
I know that we have the Rcs for current sense and the voltage at the Rcs must be 0.25V

So my question is it correct if design the output voltage 3V to drive a single LED 2.1V at 350mA?

#### Danko

Joined Nov 22, 2017
1,774
I have a design on LED driver circuit that using HV9910B.
My input is 7V - 30V
Minimum of your input should be not 7V, but 8V:

So my question is it correct if design the output voltage 3V to drive a single LED 2.1V at 350mA?
You are not able to set any specific output voltage.
Select Rcs for output current 350mA, then voltage on LED automatically will 2.1V.
do I need to add another resistor in series?
It is not necessary to add resistor in series with LED.

Last edited:

#### ir_tronik

Joined Jul 12, 2017
16
Minimum of your input should be not 7V, but 8V:
View attachment 241138

You are not able to set any specific output voltage.
Select Rcs for output current 350mA, then voltage on LED automatically will 2.1V.

It is not necessary to add resistor in series with LED.
I already tested with my power supply, the IC is ON when 7V.
Another problem is, can we set the input voltage 60V then at the output is for 2.1V LED. I have tested the configuration. But, the circuit burnt with the LED. The Rt that I use here is 1kOhm.

Does it I have to play with the frequency value? to adjust these 60V input to 2.1V LED?

#### Danko

Joined Nov 22, 2017
1,774
I already tested with my power supply, the IC is ON when 7V.
You are lucky.
I have tested the configuration. But, the circuit burnt with the LED. The Rt that I use here is 1kOhm.
1kΩ is too small.
It is better to use recommended values of resistor Rt:

Does it I have to play with the frequency value? to adjust these 60V input to 2.1V LED?
You can play with frequency value in recommended range (Rt=226kΩ...1MΩ), but it will not adjust voltage on LED.
Again: LED voltage depends only on LED current (2.1V for 350mA). Current of LED sets by Rcs and is indifferent to Vin and frequency.
HV9910 calculator (HV9910.exe in ZIP archive):

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#### Ian0

Joined Aug 7, 2020
8,944
What is the maximum Vds rating of your MOSFET?