NCP1654

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5

Detailed Pin Description(s)

Pin Number

Name

Function

6

Feed−Back /

Shutdown

This information is used for both the output regulation, the over−voltage protection (OVP), and

output undervoltage protection (UVP).

5

Vcontrol /

Soft−Start

The voltage of this pin Vcontrol directly controls the input impedance and hence the power factor

of the circuit. This pin is connected to an external capacitor Ccontrol to limit the Vcontrol band-

width typically below 20 Hz to achieve near unity power factor.

The device provides no output when Vcontrol < 0.7 V.

Vcontrol is grounded when the circuits is off.

In B version, when it starts to operate, Vcontrol raises slowly by inside 20 mA current source

as a function of time. Hence reduce the voltage and current stress on the MOSFET. Soft Start

function is achieved.

In A version, when it starts to operate, Vcontrol raises rapidly by inside 200 mA current source. It

is to boost the PFC output in a short time before the operation of the converter behind the PFC

stage.

4

Brown−Out / In

Connect a resistor network among the rectified input voltage, pin4, and ground. And connect a

capacitor between pin4 and ground. Pin4 detects a voltage signal proportional to the average

input voltage.

This signal which is proportional to the RMS input voltage Vac is also for over−power limitation

(OPL) and PFC duty cycle modulation. When the product

2

R u

OPL is activated and the Drive Output duty ratio is reduced by pulling down Vcontrol indirectly to

reduce the input power.

3

Current Sense Input

2

Multiplier Voltage

operates in peak current mode.

1

Ground

−

8

Drive

The high current capability of the totem pole gate drive (±1.5 A) makes it suitable to effectively

drive high gate charge power MOSFET.

7

the operating range is 9 V up to 20 V.