MP4655–PURE, SINGLE-STAGE, LLC, LED CURRENT AND SYSTEM VOLTAGE CONTROLLER

MP4655 Rev 1.0

www.MonolithicPower.com

24

2/2/2016

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© 2016 MPS. All Rights Reserved.

LED Current Compensation Loop (ICOMP)

ICOMP is the compensation node for the LED

current control loop. Connect a capacitor in

series with a resistor on ICOMP or an R-C-C

network (see Figure 6). The zero composed of

pole formed by the LED output. See Equation

(10):

LED

ICOMP

ICOMP

eq _ LED

OUT _ LED

OUT _ LED

LED

11

1

(10% to 20%) * V

R* C

R

* C

*C

I

==

(10)

Figure 6: Compensation Network on ICOMP

System Output Voltage Compensation Loop

through LLC Control (VCOMP)

VCOMP is the compensation node for the system

output voltage control loop through the LLC

frequency. Connect a capacitor in series with a

resistor on VCOMP or an R-C-C network (see

formed by the system output. See Equation (11):

bus

VCOMP

VCOMP

Vbus

OUT _ Vbus

OUT _ Vbus

out _ full

11

1

V

R* C

R

* C

*C

I

==

(11)

typically.

designed to be around half of the operating

frequency. See Equation (12):

op

VCOMP

VCOMP _ P

f

1

2* R

* C

2

=

π

(12)

Figure 7: Compensation Network on VCOMP

System Output Voltage Compensation Loop

through Duty-Controlled NMOS (DCOMP)

DCOMP is the compensation node for the

system output voltage control loop through the

duty-controlled NMOS. Connect a capacitor in

series with a resistor on DCOMP or an R-C-C

network (see Figure 8).

Figure 8: Compensation Network on DCOMP

recommended to cancel the pole formed by the

system output. See Equation (13):

bus

DCOMP

DCOMP

Vbus

OUT _ Vbus

OUT _ Vbus

out _ full

11

1

V

R* C

R

* C

*C

I

==

(13)

typically.

designed to be around half of the operating

frequency. See Equation (14):

op

DCOMP

DCOMP _ P

f

1

2* R

* C

2

=

π

(14)