HVLED805 datasheet(20/29 Pages) STMICROELECTRONICS

No de pièce	HVLED805

Description	Off-line LED driver with primary-sensing

PDF	29 Pages

Scroll/Zoom	100%

Fabricant	STMICROELECTRONICS [STMicroelectronics]

Site Internet	http://www.st.com

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20 / 29 page

Application information

HVLED805

20/29

Doc ID 18077 Rev 1

5.6

Voltage feedforward block

The current control structure uses the voltage VC 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:

Equation 8

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 Figure 17.

Figure 16.

Constant current operation: Switching cycle waveforms

CLED

−

CLED

Δ I

⋅

HVLED805 Fiches technique(PDF) 20 Page - STMicroelectronics