Continental Device India Pvt. Ltd

An ISO/TS 16949,

ISO 9001 and ISO 14001 Certified Company

TCIL6568

TCIL6568_REV02_22102016

D a t a s h e e t

Page 4 of 10

2.2.6、Output Over-Voltage Protection

The TCIL6568 detect the output voltage through ZCD pin during demagnetize process. When

the voltage of ZCD pin exceeds the OVP threshold, the OVP signal will be triggered and latched,

the MOSFET will be turned off and the IC work at quiescent mode, the VCC voltage dropped

below the UVLO which will make the IC shut down and the system restarts again. The output OVP

setting point can be calculated as:

1.6V

1

2

1

_

×

+

=

R

R

R

V

OVP

LED

1.6V

Latc

h

TOVPS

Vcc

R2

R1

L

D2

R4

C2

Fig.3 Principle of VCC OVP

To prevent OVP trigger falsely for inductor surge spike, the TCIL6568 designed LEB time to

ensure zero current detect sample point fall in the flat range, which is shown in Fig.4.

VZCD

t

TOVPS

0V

Sample Point

Fig.4 ZCD Pin Voltage and OVP Sample Point

2.2.7、Output Short-Circuit Protection

When the LED is shorted to ground, the output voltage is clamped to zero. The winding can’t

supply current for Vcc, so Vcc will drop down. Since the Vcc is below VCC off voltage, the

system will restart and operate in hiccup mode until the shorted condition is removed.