TOP246YN Power Integrations, TOP246YN Datasheet - Page 22
Manufacturer Part Number
IC OFFLINE SWIT UVLO HV TO220
Off Line Switcherr
Specifications of TOP246YN
66 ~ 132kHz
Voltage - Output
-40°C ~ 150°C
Package / Case
TO-220-7 (Formed Leads), 5 Leads
Input / Supply Voltage (max)
Input / Supply Voltage (min)
Duty Cycle (max)
Operating Temperature Range
- 40 C to + 150 C
No. Of Outputs
No. Of Pins
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Figure 43. 250 W, 48 V Power Supply using TOP249.
A High Efﬁciency, 250 W, 250-380 VDC Input Power Supply
The circuit shown in Figure 43 delivers 250 W (48 V @
5.2 A) at 84% efﬁciency using a TOP249 from a 250 VDC to
380 VDC input. DC input is shown, as typically at this power
level a p.f.c. boost stage would preceed this supply, providing the
DC input (C1 is included to provide local decoupling). Flyback
topology is still usable at this power level due to the high output
voltage, keeping the secondary peak currents low enough so
that the output diode and capacitors are reasonably sized.
In this example, the TOP249 is at the upper limit of its power
capability and the current limit is set to the internal maximum
by connecting the X pin to SOURCE. However, line sensing
is implemented by connecting a 2 MΩ resistor from the L pin
to the DC rail. If the DC input rail rises above 450 VDC, then
TOPSwitch-GX will stop switching until the voltage returns to
normal, preventing device damage.
Due to the high primary current, a low leakage inductance
transformer is essential. Therefore, a sandwich winding with
a copper foil secondary was used. Even with this technique,
the leakage inductance energy is beyond the power capability
of a simple Zener clamp. Therefore, R2, R3 and C6 are added
in parallel to VR1. These have been sized such that during
normal operation, very little power is dissipated by VR1,
the leakage energy instead being dissipated by R2 and R3.
No Load Consumption:
≤ 1.4 W (300 VDC)
< 100 mV pk-pk
2.2 nF Y1
However, VR1 is essential to limit the peak drain voltage
during start-up and/or overload conditions to below the 700 V
rating of the TOPSwitch-GX MOSFET.
The secondary is rectifed and smoothed by D2 and C9, C10 and
C11. Three capacitors are used to meet the secondary ripple
current requirement. Inductor L2 and C12 provide switching
A simple Zener sensing chain regulates the output voltage.
The sum of the voltage drop of VR2, VR3 and VR4 plus the
LED drop of U2 gives the desired output voltage. Resistor R6
limits LED current and sets overall control loop DC gain.
Diode D4 and C14 provide secondary soft-ﬁnish, feeding
current into the CONTROL pin prior to output regulation and
thus ensuring that the output voltage reaches regulation at start-
up under low line, full load conditions. Resistor R9 provides a
discharge path for C14. Capacitor C13 and R8 provide control
loop compensation and are required due to the gain associated
with such a high output voltage.
Sufﬁcient heat sinking is required to keep the TOPSwitch-GX
device below 110 °C when operating under full load, low line
and maximum ambient temperature. Airﬂow may also be
required if a large heatsink area is not acceptable.
All resistor 1/8 W 5% unless
VR2 22 V
VR3 12 V
VR4 12 V
3 µH 8A