MP4060—TRIAC Dimmable PFC, PSC LED Controller for 200-265VAC LEDs

MP4060 Rev. 1.0

www.MonolithicPower.com

18

5/27/2015

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Figure 6—Leading-edge blanking

Output Over-Voltage Protection (OVP)

Output over-voltage protection (OVP) prevents

the components from over-voltage damage. The

voltage of the auxiliary winding positive plateau is

proportional to the output voltage, so the OVP

block monitors this auxiliary winding voltage to

apply an OVP function (see Figure 7). Once ZCD

triggered, the gate driver turns off, and the IC

works in quiescent current mode. When the VCC

voltage drops below the UVLO threshold, the IC

shuts down and the system re-starts. The output

OVP set point is calculated with Equation (2):

⋅⋅

=

+

aux

ZCD2

out _ ovp

ZCD _ OVP

sec

ZCD1

ZCD2

NR

VV

NR

R

(2)

Where:

Figure 7—OVP sampling circuit

To avoid switch-off spikes mis-triggering OVP,

Figure 8).

Figure 8—ZCD voltage & OVP sampling

Cycle-by-Cycle Current Limit

There is cycle-by-cycle current limit on S. When

blanking time), the switching turns off to limit the

peak current value.

Primary Over-Current Protection (OCP)

S has an internally integrated comparator for

primary side OCP. When the gate is on, the

comparator is enabled. Over-current occurs

IC shuts down and re-starts after VCC drops

below UVLO. The OCP function block diagram is

shown in Figure 9.

S

D

OCP

Gate

Rs

latch

Blanking

Figure 9—Over-current protection circuit

LED Short-Circuit Protection (SCP)

When an LED short circuit occurs, the IC reduces

the switching frequency to 7 kHz. The the output

power at this condition is limited within a safe

range.