MP4054 – NON-ISOLATED OFFLINE LED CONTROLLER WITH ACTIVE PFC

MP4054 Rev. 1.0

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12

12/25/2014

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(typical 0.413V);

sensing

resistor

connected

between the MOSFET source and GND.

In high-side solution (including both Buck and

Buck-boost),

the

proprietary

direct-current

control method allows the MP4054 to control

the LED current accurately. The mean value of

the

output

LED

current

is

calculated

approximately as:

REF

o

FB

V

I

R



sensing

resistor

connected

between the FB RC filter and GND in high-

side solution

Power-Factor Correction (PFC)

MULT is connected to a pull-up resistor from

the rectified-instantaneous-line voltage; the

multiplier output is sinusoidal. This signal sets

the sinusoidal inductor peak current. This

achieves a high power factor (PF).

Inductor current

Multiplier output

Figure 4: Power-Factor Correction

The maximum output voltage of the multiplier is

clamped to 2.0V, setting the cycle-by-cycle

current limit.

VCC Under-Voltage Lockout (UVLO)

When the VCC voltage drops below the UVLO

threshold 9.5V, the IC stops switching and

shuts down; the operating current is very low

under this condition. VCC is then charged by

the external resistor from the AC line. Figure 5

shows the typical waveform of UVLO.

Figure 5: VCC Under-Voltage Lockout

Auto Starter

The MP4054 integrates an auto-restart that

begins timing when the MOSFET turns off. If

ZCD fails to send a turn-on signal after 190µs, a

turn-on signal is initiated. This avoids an

unnecessary IC shut down if ZCD misses

detection.

Minimum Off Time

The MP4054 operates with variable switching

frequency. The frequency changes with the

input instantaneous line voltage. To limit the

maximum

frequency

and

enhance

EMI

performance, the chip employs an internal

minimum OFF-time of 5.5µs.

Leading-Edge Blanking (LEB)

Internal

leading-edge-blanking

(LEB)

is

employed to prevent a switching pulse from

terminating

prematurely

due

to

parasitic

capacitance discharging when the MOSFET

turns on. During the blanking time, the path

from CS/ZCD to the current comparator input is

blocked. Figure 6 shows the leading-edge

blanking time. The LEB time of OCP detection

is relatively short at 280ns.

t

V

CS

t

Figure 6: Leading-Edge Blanking