MP023 – PRIMARY-SIDE CC/CV CONTROLLER

MP023 Rev. 1.1

www.MonolithicPower.com

13

7/18/2016

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© 2016 MPS. All Rights Reserved.

OPERATION

The MP023 is a primary-side controller that

provides

accurate,

constant

voltage

and

constant current regulation without the need of

an optocoupler or secondary feedback circuit.

As shown in the Typical Application diagram,

the circuit is designed to operate with a minimal

number of external components.

Start-Up

The IC is self-supplied by the internal high-

voltage current source, which is drawn from HV.

Once the voltage on VCC reaches the VCC on

current source turns off for better efficiency.

Afterward,

the

auxiliary

winding

of

the

transformer takes over the power supply. When

the IC stops switching, and the internal high-

voltage current source turns on again (see

Figure 2).

Figure 2: VCC UVLO

Peak Current Control on the Primary Side

in Figure 3.

Figure 3: Simplified Flyback Converter

The current rises linearly at a rate shown in

Equation (1):

Pin

m

dI (t)

V

dt

L



(1)

Figure 4: Primary Current Waveform

can be calculated with Equation (2):

CS

pk

S

V

I

R



(2)

See Equation (3):

2

mpk

1

EL I

2



(3)

The power transferred from the input to the

output can be calculated with Equation (4):

2

mpk s

1

PL I f

2



(4)

In

constant

current

(CC)

operation,

the

switching frequency (see Figure 5).