UCS1602SG-S08-R datasheet(6/8 Pages) UTC

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UCS1602S

Preliminary

LINEAR INTEGRATED CIRCUIT

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QW-R103-123 .a

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FUNCTIONAL DESCRIPTION (Cont.)

(4) Constant Output Power Limit

When the primary current, across the primary wind of transformer, reaches the limit current, the output GATE

driver will be turned off after a small propagation delay tD. This propagation delay will introduce an additional current

proportional to tD×VIN/Lp. Since the propagation delay is nearly constant regardless of the input line voltage VIN.

Higher input line voltage will result in a larger additional current and hence the output power limit is also higher than

that under low input line voltage. To compensate for this output power limit variation across a wide AC input range,

the threshold voltage is adjusted by adding a positive ramp. This ramp signal rises from VSENSE-L to VSENSE_H, and

then flattens out at VSENSE_H. A smaller threshold voltage forces the output GATE drive to terminate earlier. This

reduces the total PWM turn-on time and makes the output power equal to that of low line input. This proprietary

internal compensation ensures a constant output power limit for a wide AC input voltage range (90VAC to 264VAC).

(5) Protection section

The IC takes on more protection functions such as OLP, OVP and OTP etc. In case of those failure modes for

continual blanking time, the driver is shut down. At the same time, IC enters auto-restart, VCC power on and driver is

reset after VCC power on again.

OLP

After power on, IC will shutdown driver if over load state occurs for continual TD-OLP. OLP case as followed Fig.5.

OVP

OVP will shutdown the switching of the power MOSFET whenever VCC>VOVP. The OVP case as followed Fig.6.

Fig.5 OLP case

Fig.6 OVP case

OTP

OTP will shut down driver when junction temperature TJ>T(THR) for continual a blanking time.

UCS1602SG-S08-R 데이터시트(PDF) 6 Page - Unisonic Technologies