UCL2310G-S08-R datasheet(6/7 Pages) UTC

6 / 7 page

UCL2310

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 7

www.unisonic.com.tw

QW-R125-061.a



APPLICATION INFORMATION (Cont.)

Protection Functions

The UTC UCL2310 offers rich protection functions to improve the system reliability.

When the LED is open circuit, the output voltage will gradually rise up. The VCC voltage will also rise up. When

VCC voltage reaches the 19V OVP threshold, it will trigger fault logic and the system stops switching. At some

catastrophic fault condition, if the VCC voltage continues to rise, the internal clamping circuit will limit the VCC voltage

to 23V, which helps improving the system reliability.

When the LED is shorted circuit, the system will work under 10kHz switching frequency. Meanwhile, the output

voltage is low and the auxiliary winding cannot charge the VCC pin. So the VCC pin voltage will gradually decrease

and finally reaches the UVLO threshold.

After the system enters into fault condition, the VCC voltage will decrease until it reaches UVLO threshold, then

the system will re-start again. If the fault condition is removed, the system will resume normal operation.

When the output is short circuit or the transformer is saturated, the CS peak voltage will be relatively high. When

CS voltage reaches the internal limitation (1V), the power MOSFE will be turned off instantaneously. This cycle by

cycle current limitation can help protecting the power MOSFET, the transformer and the output rectifying diode.

PCB Layouts

The following guidelines should be followed in UTC UCL2310 PCB layout:

Bypass Capacitor

The bypass capacitor on VCC pin should be as close as possible to the VCC and GND pins.

Ground Path

The power ground path for current sense resistor should be short and wide, and it should be as close as possible

to the IC ground (pin 2), otherwise the LED output current accuracy maybe affected. The IC signal ground for COMP

and FB components should be connected to the IC GND pin wit short traces and should be away from the power

ground path.

The Area of Power Loop

The area of main current loop should be as small as possible to reduce EMI radiation, such as the primary current

loop, the snubber circuit and the secondary rectifying loop.

FB Pin

The feedback resistor divider should be as close as possible to the FB pin, and the trace must keeps away from

dynamic node of the transformer and MOSFET DRAIN trace, otherwise the FB pin OVP function might have risk to

be mis-triggered by the system noise.

UCL2310G-S08-R Arkusz danych(PDF) 6 Page - Unisonic Technologies