UPS604 Datasheet, PDF (8/12 Pages) Unisonic Technologies – HIGH PERFORMANCE CURRENT MODE POWER SWITCH

UPS604
LINEAR INTEGRATED CIRCUIT
„ FUNCTIONAL DESCRIPTION(Cont.)
(5) Constant Output Power Limit
When the SENSE voltage, across the sense resistor R_S, reaches the threshold voltage, around 0.8V, the output
GATE drive will be turned off after a small propagation delay t_D. This propagation delay will introduce an additional
current proportional to tD×V_IN/Lp. Since the propagation delay is nearly constant regardless of the input line voltage
V_IN. 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 this variation for wide AC input range, the threshold voltage is
adjusted by the V_IN current. Since V_IN pin is connected to the rectified input line voltage through a resistor R_VIN, a
higher line voltage will generate higher V_IN current into the V_IN pin. The threshold voltage is decreased if the V_IN
current is increased. Smaller threshold voltage, forces the output GATE drive to terminate earlier, thus reduce the
total PWM turn-on time and make the output power equal to that of low line input. This proprietary internal
compensation ensures a constant output power limit for wide AC input voltage from 90VAC to 264VAC.
(6) 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, V_CC power on and driver is
reset after V_CC power on again.
OLP
After soft-start phase end, IC will shutdown driver if over load state occurs for continual T_D-OLP. OLP function will
not inactive during soft-start phase. OLP case as followed FIG. 6. The test circuit as followed FIG.8. T_D-OLP=5.53×T_SS.
OVP
There are two kinds of OVP circuits, the first OVP function are enabled only when V_SS<V_{SS (DEACT)} & V_FB>V_FB
(OLP) ^{during soft-start phase. During above condition, driver will be shutdown if over voltage state occurs (V}CC^>VOVP1⁾
for continual a blanking time. The first OVP function will not inactive after soft-start phase. The second OVP will
shutdown the switching of the power MOSFET whenever V_CC>V_OVP2. The first OVP case as followed FIG.7. The test
circuit as followed FIG.9.
FIG.6 OLP case
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FIG.7 OVP case
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QW-R119-006.E