NCP1611 Ver la hoja de datos (PDF) - ON Semiconductor

Número de pieza

componentes Descripción

Fabricante

NCP1611

Enhanced, High-Efficiency Power Factor Controller

ON Semiconductor 

NCP1611

DETAILED PIN DESCRIPTION

Pin Number

Name

1

VCONTROL

2

VSENSE

3

FFCONTROL

4

CS / ZCD

5

Ground

6

Drive

7

VCC

8

Feedback

Function

The error amplifier output is available on this pin. The network connected between this pin and

ground adjusts the regulation loop bandwidth that is typically set below 20 Hz to achieve high

Power Factor ratios.

Pin1 is grounded when the circuit is off so that when it starts operation, the power increases

slowly to provide a soft−start function.

A portion of the instantaneous input voltage is to be applied to pin 2 in order to detect

brown−out conditions. If Vpin2 is lower than 0.9 V for more than 50 ms, the circuit stops pulsing

until the pin voltage rises again and exceeds 1.0 V.

This pin also detects the line range. By default, the circuit operates the “low−line gain” mode. If

Vpin2 exceeds 2.2 V, the circuit detects a high−line condition and reduces the loop gain by 3.

Conversely, if the pin voltage remains lower than 1.7 V for more than 25 ms, the low−line gain

is set.

Connecting the pin 2 to ground disables the part once the 50 ms blanking time has elapsed.

This pin sources a current representative to the line current. Connect a resistor between pin3

and ground to generate a voltage representative of the line current. When this voltage exceeds

the internal 2.5 V reference (VREF), the circuit operates in critical conduction mode. If the pin

voltage is below 2.5 V, a dead−time is generated that approximately equates

[66 ms x (1 − (Vpin3/VREF))]. By this means, the circuit forces a longer dead−time when the

current is small and a shorter one as the current increases.

The circuit skips cycles whenever Vpin3 is below 0.65 V to prevent the PFC stage from

operating near the line zero crossing where the power transfer is particularly inefficient. This

does result in a slightly increased distortion of the current. If superior power factor is required,

offset pin 3 by more than 0.75 V offset to inhibit the skip function.

This pin monitors the MOSFET current to limit its maximum current.

This pin is also connected to an internal comparator for Zero Current Detection (ZCD). This

comparator is designed to monitor a signal from an auxiliary winding and to detect the core

reset when this voltage drops to zero. The auxiliary winding voltage is to be applied through a

diode to avoid altering the current sense information for the on−time (see application

schematic).

Connect this pin to the PFC stage ground.

The high−current capability of the totem pole gate drive (−0.5/+0.8 A) makes it suitable to

effectively drive high gate charge power MOSFETs.

This pin is the positive supply of the IC. The circuit starts to operate when VCC exceeds 10.5 V

(A version, 17.0 V for the B version) and turns off when VCC goes below 9.0 V (typical values).

After start−up, the operating range is 9.5 V up to 35 V. The A version is preferred in

applications where the circuit is fed by an external power source (from an auxiliary power

supply or from a downstream converter). Its maximum start−up level (11.25 V) is set low

enough so that the circuit can be powered from a 12 V rail. The B version is optimized for

applications where the PFC stage is self−powered.

This pin receives a portion of the PFC output voltage for the regulation and the Dynamic

Response Enhancer (DRE) that drastically speeds−up the loop response when the output

voltage drops below 95.5% of the desired output level.

Vpin8 is also the input signal for the (non−latching) Over−Voltage (OVP) and Under−Voltage

(UVP) comparators. The UVP comparator prevents operation as long as Vpin8 is lower than

12% of the reference voltage (VREF). A soft OVP comparator gradually reduces the duty−ratio

when Vpin8 exceeds 105% of VREF. If despite of this, the output voltage still increases, the

driver is immediately disabled if the output voltage exceeds 107% of the desired level (fast

OVP).

A 250 nA sink current is built−in to trigger the UVP protection and disable the part if the

feedback pin is accidentally open.

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