UPSL1630 Datasheet, PDF (5/7 Pages) Unisonic Technologies – PSR, SINGLE STAGE, AC-DC LED DRIVER WITH ACTIVE

UPSL1630
Preliminary
CMOS IC
 APPLICATION INFORMATION
The UTC UPSL1630 is a primary-side-control AC-DC LED driver which can achieve high power factor and
accurate LED current for an isolate lighting application in a single stage converter. The LED current can be
controlled accurately from the primary side information and integrates power factor correction function and works in
DCM and constant OFF time mode for reducing the harmonic current emission (THD).
Startup Control
A soft-start function is implemented to prevent the transformer from entering into CCM. The V_DD pin of UTC
UPSL1630 is charged through a startup resistor. When the V_DD voltage reaches V_TH(ON), the internal startup circuit is
disabled and the IC turns on. Then, the STP pin is clamped to lower than V_DD voltage about 0.2V.
Operating Current
The Operating current of UTC UPSL1630 is as low as 3mA. Good efficiency and very low standby power can be
achieved.
Constant Current Operation
UTC UPSL1630 use the primary side constant current control method to accurately control the LED current. The
LED real current can be approximated as:
I_LED
≈
1
2
×
N_P
N_S
0.4V
R_CS
Where N_P is primary winding, N_S is secondary winding; R_CS is an external current sensing resistor.
Power Factor Correction
The primary side current increases linearly from zero to peak value, during the external MOSFET on-time. When
the primary current reaches the threshold, UTC UPSL1630 turns off the power MOSFET immediately. After a
constant OFF time, T_OFF, UTC UPSL1630 turns on the power MOSFET again. The peak current threshold follows
the rectified sinusoidal-shape of main line voltage. As a result, the envelope of the inductor current is
sinusoidal-shaped, high power factor is therefore achieved in this way.
Over-voltage Protection
UTC UPSL1630 built-in two over-voltage protection schemes:
(1) If DSEN pin’s voltage is detected above 3.2V for three times, UTC UPSL1630 turns off the PWM switching signal,
and V_DD voltage gradually drops to UVLO threshold, and the system will be re-started. The threshold voltage of the
output over voltage protection can be easily defined as:
V_{OUT _ OVP}
=
3.2
×
(1+
R5
R6
)
×
N_S
N_A
-V_D8
Where N_S is the secondary winding, N_A is auxiliary winding, V_D8 is the forward bias of the secondary side rectifier
diode.
(2) If V_DD pin’s voltage exceeds 19.2V three times, UTC UPSL1630 turns off the PWM switching signal, and V_DD
gradually drops to UVLO threshold, and then the system will be re-started.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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