MP4021A データシートの表示（PDF） - Monolithic Power Systems

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MP4021A

Primary Side Control Offline LED Controller with Active PFC

Monolithic Power Systems 

MP4021A—PRIMARY SIDE CONTROL OFFLINE LED CONTROLLER WITH ACTIVE PFC

PIN FUNCTIONS

Pin #

1

2

3

4

5

6

7

8

Name Pin Function

MULT

ZCD

VCC

GATE

CS

GND

Multiplier input. Connect this pin to the tap of resistor divider from the rectified voltage of the

AC line. The half-wave sinusoid signal to this pin provides a reference signal for the internal

current control loop.

Zero-current detection. A negative going-edge triggers the turn-on signal of the external

MOSFET. Connect this pin to a resistor divider between the auxiliary winding to GND. Over-

voltage condition is detected through ZCD. Every switching turn-off interval, if ZCD voltage

is higher than the over-voltage-protection (OVP) threshold after the 1.5µs blanking time, the

over-voltage protection will trigger and the system will stop switching until auto-restart

comes. ZCD pin can also monitor over-current condition. Connect this pin thru a diode to a

resistor divider between CS to GND. Every switching turn-on interval, if ZCD voltage is

higher than the over-current-protection (OCP) threshold after the 280ns blanking time, the

over-current protection will trigger and the system will stop switching until auto-restart

comes.

Power supply input. This pin supplies the power for the control signal and the high-current

MOSFET grade drive output. Bypass this pin to ground with an external bulk capacitor of

typically 22µF in parallel with a 100pF ceramic cap to reduce noise.

Gate drive output. This totem pole output stage is able to drive a high-power MOSFET with

a peak current of 1A source capability and 1.2A sink capability. The high level voltage of

this pin is clamped to 13.5V to avoid excessive gate drive voltage. And the low level voltage

is higher than 6V to guarantee enough drive capacity.

Current sense. The MOSFET current is sensed via a sensing resistor to its source lead. The

comparison between the resulting voltage and the internal sinusoidal-current reference

signal determines when the MOSFET turns off. A feed-forward from the rectified AC line

voltage connected to the current sense pin maximizes the line regulation. If the pin voltage

is higher than the current limit threshold of 2.5V (after turn-on blanking) the gate drive will

turn off.

Ground. Current return for the control signal and the gate drive signal.

FB/NC Feedback signal. Leave this pin floating (NC) for primary-side control.

COMP

Loop compensation input. Connect a compensation network to stabilize the LED drive and

maintain an accurate LED current.

MP4021A Rev.1.04

www.MonolithicPower.com

5

7/5/2013

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