UPSL101

Preliminary

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

7 of 8

www.unisonic.com.tw

QW-R125-027.b

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FUNCTION DESCRIPTION (Cont.)

Maximum Frequency Clamp

According to Transition Mode (TM) Operation principle, the switching frequency is inversely proportional to the

output power. Therefore, when the output power decreases, the switching frequency can become rather high without

limiting. The maximum switching frequency in UTC UPSL101 is internally limited to approximately 300kHz.

Power Factor Correction

The MULT pin is connected to the tap of the resistor divider from the rectified instantaneous line voltage and fed

as one input of the multiplier. The output of the multiplier will be shaped as sinusoid too. This signal provides the

reference for the current comparator and comparing with the primary side inductor current which sets the primary

peak current shaped as sinusoid with the input line voltage. High power factor can be achieved.

than 28V, OVP protection is triggered and GATE is shut down, so the device enters power on startup sequence

thereafter.

LED String Short Protection

When LED string is short, the positive plateau of auxiliary winding voltage is also near zero and the ZCD voltage is

low. If the voltage at ZCD pin is lower than a threshold of approximately 0.9V and lasts more than 10ms, the IC will

shut down.

LED String Open Protection

When the LED string open circuit happens, the positive plateau of auxiliary winding voltage increases and the ZCD

voltage is high. If the voltage at ZCD pin is higher than a threshold of approximately 4V, UTC UPSL101 will shut

down and restart again.

Thermal Shutdown

UTC UPSL101 provides an on chip thermal shutdown. The IC will stop switching when the junction temperature

exceeds the thermal shutdown temperature, typically 140°C.

Gate Drive Output

The UTC UPSL101 output stage is a fast totem-pole gate driver. Cross conduction has been avoided to minimize

heat dissipation, increase efficiency, and enhance reliability. The output driver is clamped at 12V to protect power

MOSFET transistors against undesired over-voltage gate signals.

Protection Control

voltage protection, LED open/short circuit protection, over temperature protection, over current protection, leading

below UVLO (ON) and the power converter enters power on start-up sequence thereafter.