MP163 – 700V, NON-ISOLATED, OFFLINE REGULATOR WITH INTEGRATED LDO

MP163 Rev. 1.01

www.MonolithicPower.com

16

8/11/2017

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© 2017 MPS. All Rights Reserved.

APPLICATION INFORMATION

Topology Options

such as buck, boost, buck-boost, and flyback.

Component selection is based on the

Typical

Selecti

The input capacitor supplies DC input voltage

for the converter. Figure 6 shows the typical DC

bus voltage waveform of a half-wave rectifier

and a full-wave rectifier.

Vin

DC input voltage

t

V

DC(min)

V

DC(max)

AC input voltage

Vin

DC input voltage

t

V

DC( min)

V

DC(max)

AC input voltage

Figure 6: Input Voltage Waveform

Typically, the use of a half-wave rectifier

requires an input capacitor rated at 3µF/W for

the universal input condition. When using a full-

wave rectifier, the input capacitor is chosen

between 1.5 ~ 2µF/W for the universal input

condition. A half-wave rectifier is recommended

for output applications less than 2W. Otherwise,

use a full-wave rectifier.

Under very low input voltages, the inductor

current ramps up slowly. It may not reach the

current limit during

time should be less than the minimum value of

Selecting the Inductor

The MP163 has a minimum off time limit that

determines the maximum power output. A

power inductor with a larger inductance

increases the maximum power. Using a very

small inductor may cause failure at full load.

The maximum power in CCM can be calculated

with Equation (7)



omax

o peak

V

PV (I

)

2L

(7)

The maximum power in DCM can be calculated

with Equation (8):





2

omax

peak

minoff

11

PLI

2

(8)

For

mass

production,

tolerance

on

the

parameters (such as peak

the minimum off time) should be taken into

consideration.

Freewheeling Diode

Select a diode with a maximum reverse voltage

rating greater than the maximum input voltage

and a current rating determined by the output

current.

The reverse recovery of the freewheeling diode

can affect efficiency and circuit operation during

CCM, so use an ultra-fast diode

UGC10JH.

Selecting the Output Capacitor

The output capacitor is required to maintain the

DC output voltage. Estimate the output voltage

ripple

CCM _ ripple

ESR

so

i

Vi R

8f C



  

(9)

Estimate the output voltage ripple in DCM with

Equation (10):

2

pk

o

o

DCM _ ripple

pk

ESR

so

pk

II

I

VI

R

fC

I

















(10)

It is recommended to use ceramic, tantalum, or

low ESR electrolytic capacitors to reduce the

output voltage ripple.

Feedback Resistors

The

resistor

divider

connected

to

FB

determines

the

output

voltage.

Choose

appropriate R1 and R2 values to

set the