STMicroelectronics HVLED805 Evaluation Board EVALHVLED805 EVALHVLED805 Data Sheet

20/29

Doc ID 18077 Rev 1

The current control structure uses the voltage V

C

 to define the output current, according to 

(7). Actually, the CC comparator will be affected by an internal propagation delay Td, which 
will switch off the MOSFET with a peak current than higher the foreseen value.

This current overshoot will be equal to:

Will introduce an error on the calculated CC setpoint, depending on the input voltage.

The HVLED805 implements a Line Feedforward function, which solves the issue by 
introducing an input voltage dependent offset on the current sense signal, in order to adjust 
the cycle-by-cycle current limitation.

The internal schematic is shown in 

         

t

t

t

t

I

P

I

s

Q

I

C

T

R

C

V

CLED

I

−

=

CLED

I

IN

d

P

P

V T

Δ I

L

⋅

=