MP4027 – PRIMARY-SIDE CONTROL, OFFLINE LED CONTROLLER WITH ACTIVE PFC

MP4027 Rev. 1.02

www.MonolithicPower.com

8

12/9/2014

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© 2014 MPS. All Rights Reserved.

PIN FUNCTIONS

Pin #

Name

Description

1

VCC

Power Supply Input.

Supply power for the control signals and driving high-current

MOSFET. Bypass to ground with an external bulk capacitor (typically 4.7µF).

2

MULT

Multiplier Input.

Connect to the tap of resistor divider between the rectified AC line and

GND. The half-wave sinusoid provides a reference signal for the internal-current-control

loop. MULT is used for brown-out protection detection.

3

NTC

LED Temperature Protection.

Connect an NTC resistor from this pin to GND can reduce

the output current to protect the LED when ambient temperature rising high. Apply an

external PWM signal on this pin can dim the LED with PWM mode.

A 2.2nF to 4.7nF ceramic cap is recommended to connect from NTC to GND to bypass

the high frequency noise when activate temperature protection. For PWM dimming, the

cap can be removed.

4

COMP

Loop Compensation Input.

Connect a compensation network to stabilize the LED driver

and maintain an accurate LED current.

5

GND

Ground.

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

6

FB

Feedback Input.

If the accurate LED current is needed, connect this pin to the LED-

current-sensing resistor.

7

CS/ZCD

Current-Sense and Zero-Current Detection.

This is a MPS proprietary dual function pin.

When the gate driver turns on, CS/ZCD senses the MOSFET current. The difference

between the sensed voltage and the internal sinusoidal-current-reference determines

when the MOSFET turns off.

When the gate driver turns off, the zero crossing (after blanking time) triggers GATE turn-

on signal. Connect CS/ZCD to a resistor divider through a diode between the auxiliary

winding and GND.

Output over-voltage condition is detected through ZCD. During every turn-off interval, if

the ZCD voltage exceeds the over-voltage protection threshold, after the 1.6µs

and the system stops switching until auto-restart.

CS/ZCD is used for primary-side over-current protection. If the sensing voltage reaches

2.46V (after blanking time), the primary-side over-current protection is triggered and the

system stops switching until auto-restart.

A 10pF ceramic cap is recommended to connect CS/ZCD to GND to bypass the high-

frequency noise. In order to reduce RC delay influence on the accuracy of the current-

recommended.

8

GATE

Gate Drive Output.

This totem-pole output stage can drive a high-power MOSFET with a

peak current of 0.8A source and 1A sink. The high-voltage limit is clamped to 14.5V to

avoid excessive gate-drive voltage. The drive-voltage is higher than 6.7V to guarantee a

sufficient drive capacity.