MP4001

– UNIVERSAL INPUT HIGH BRIGHTNESS WLED DRIVER

MP4001 Rev. 1.02

www.MonolithicPower.com

10

5/1/2018

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© 2018 MPS. All Rights Reserved.

OPERATION

Internal Regulator

MP4001 employs a high-voltage with 500V

break down voltage JFET circuit, which allows

the universal AC line input to power the IC

directly. The MP4001 integrated a smart LDO

which conducts only when the voltage on IN pin

is lower than 24V. With such smart LDO design,

the IC power dissipation is significantly reduced

and high frequency operation is feasible. The

output waveform of VCC voltage is a sawtooth

wave when this LDO is active, the peak and

valley value of this sawtooth wave are 9.8V and

8.9V.

To avoid the risk that the VCC voltage drops

too low to cause the driving capability of DRIVE

signal, the MP4001 integrated another LDO to

regulate the VCC voltage to 8.5V. The following

figure shows the structure of internal LDO.

MP0

MP0

8.5V

MP1

VCC

High Voltage

Switch

9.8V

8.9V

Figure 2: Functional Block Diagram of LDO

is at the range of 14V-24V and MP1 is the 8.5V

LDO.

Figure3 shows the waveform of VCC voltage in

different VCC capacitance. To design the VCC

capacitor value, the following conditions must

be satisfied:

1. The MP0 should be active every time the IN

voltage gets to 14V-24V.

2. The MP1 should NOT be active when the IN

voltage is higher than 24V to ensure the high

efficiency.

3. the VCC voltage can NOT drop to lower than

VCC UVLO value.

The following is to follow these limitations

line

VCC

Q

s

g

VCC

VCC

(9.8V 8.9V)

VCC

(9.8V 8.5V)

1

t

2*f

I

I

f *Q

VCC

C

*

I

t



 















quiescent current of MP4001, fs is switching

MOSFET.

For

most

application

a

10uF-22uF

VCC

capacitor is recommended.

24V

14V

8.5V

8.9V

9.8V

8.5V

8.9V

9.8V

8.9V

9.8V

8.5V

VCC

VCC

VCC

Large Cap

Mid Cap

Small Cap

Figure 3: VCC Voltage in Different Capacitance

LED Current Regulation and Valley Detection

With a floating buck converter configuration, as

shown in the typical application circuit, MP4001

turns off the MOSFETs Q1 with a peak current

control. The peak current is sensed with a

peak current is regulated as:

L _ PEAK

sense

300mV

I

R



In normal operations, MP4001 turns on Q1

when the current in the freewheeling diode

goes to zero. As a result, the average LED

current is well regulated as: