MP4030—PRIMARY-SIDE-CONTROL, OFFLINE LED CONTROLLER WITH PFC

MP4030 Rev.1.02

www.MonolithicPower.com

13

4/16/2013

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Inductor Current

Multiplier Output

Figure 4: Power-Factor Correction

The multiplier’s maximum output voltage to the

current comparator is clamped to 2.3V to limit the

cycle-by-cycle current. The multiplier’s minimum

output voltage is clamped to 0.1 to ensure a turn-

on signal during the TRIAC dimming OFF interval,

which pulls down the rectifier input voltage and

accurately detects the dimming phase.

reaches 10V, the internal charging circuit stops

charging, the control logic initializes and the

internal main MOSFET begins to switch. Then

the auxiliary winding takes over the power supply.

However, the initial auxiliary-winding positive

below the 9V threshold, the internal charging

This cycle repeats until the auxiliary winding

If any fault occurs during this time, the switching

and the internal charging circuit will stop and

the internal charging circuit re-charges for auto-

restart.

10V

9V

Vcc

Internal

Charging Circuit

And Regulates the VCC

Auxiliary Winding Takes Charge

Fault happens

Gate

Switching Pulses

7V

Auto Start

The MP4030 includes an auto starter that starts

timing when the MOSFET turns off. If ZCD fails

to send a turn-on signal after 122µs, the starter

will automatically sends a turn-on signal to avoid

unnecessary Ic shutdowns if ZCD fails.

Minimum OFF Time

The MP4030 operates with a variable switching

frequency; the frequency changes with the

instantaneous input-line voltage. To limit the

maximum

frequency

and

get

good

EMI

performance, the MP4030 employs an internal

minimum OFF-time limiter of 5.6µs, as shown in

Figure 6.

ZCD

GATE

5.6us

Figure 6: Minimum OFF time