MP4001

– UNIVERSAL INPUT HIGH BRIGHTNESS WLED DRIVER

MP4001 Rev 1.02

www.MonolithicPower.com

14

5/1/2018

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© 2018 MPS. All Rights Reserved.

A

B

C

D

Figure 11: Waveform of Valley Fill Circuit

The valley fill circuit makes the interval that the

circuit is powered by AC line extremely increased

to make increase the power factor.

Here choose two 22uF/250V capacitors and

three 400V/1A diode to construct the valley fill

circuit.

Select the Inductor

The MP4001 work in BCM, select a proper

inductor value to ensure the operating frequency

is at the design range: The maximum operating

frequency for MP4001 is 110kHz, the frequency

must set higher than 20kHz to avoid noise.

bus _ max

out _ min

out _ min

s _ max

LED

bus _ max

(V

V

) V

1

L

f

2 I

V









bus _ min

out _ max

out _ max

s _ min

LED

bus _ min

(V

V

) V

1

L

f

2 I

V









Choose a 680uH inductor with the maximum

operating frequency around 60kHz and minimum

operating frequency around 20kHz.

The saturated current of inductor must be greater

than twice of LED current.

Select Power MOSFET

The voltage stress of MOS must be greater than

the maximum input voltage (375V).

The peak current through the MOSFET is the

peak value of inductor current, which equals

twice of LED current. The RMS current of MOS

can be gotten from the following equation.

out

MOS_ RMS

LED

bus

V

I

2* I

*

3* V



Choose a MOSFET with 600V voltage rating and

2.4A current rating.

Select Rectifying Diode

The voltage stress of the rectifying diode must be

greater than the maximum input voltage (375V).

The average current of the rectifying diode can

be calculated by following equation.

out

D _ AVG

LED

bus

V

I

2* I

*(1

)

V



Choose an ultra-fast diode with 600V voltage

rating and 1A current rating.

Select Current Sense Resistor

The current sense resistor is selected by the

following.

CS

LED

300mV

R

2* I



Use a 500mOhm and a 2.49Ohm resistor parallel

as the current sense resistor.

Select the Output Capacitor

The output capacitor should be large enough to

filter the output ripple current and so that the LED

current ripple is in a desired range.

For a ceramic output capacitor, its value should

be:

L _ PEAK

OUT

s _ min

LED

LED _ ripple _ pk _ pk

I

C

8f

R

I





Where RLED is the dynamic resistor of LED load.

LED

LED

LED

V

R

I







occurs

at

the

minimum

input

voltage

and

maximum

output

voltage

condition

for

this

application.

bus _ min

LED _ max

LED _ max

s _ min

L _ PEAK

bus _ min

(V

V

) * V

f

L * I

* V



