STCH02 datasheet(16/24 Pages) STMICROELECTRONICS

部件名	STCH02

功能描述	Offline PWM controller for ultra-low standby adapters

PDF	24 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

标志

16 / 24 page

Application information

STCH02

16/24

DocID028766 Rev 1

3.7

Voltage feedforward block

The current control structure uses the voltage VC to define the output current, according to

Equation 1. 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.

The STCH02 device 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 external schematic configuration is shown in Figure 9.

Figure 9. Feedforward compensation: internal schematic

The RZCD resistor can be calculated as follows:

Equation 2

where RFF is an internal parameter, defined in Table 5 on page 7.

In this case the peak drain current does not depend on input voltage anymore.

S E N S E

F F

P R

P R I

A U X

Z C D

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STCH02 数据表(PDF) 16 Page - STMicroelectronics