SE1051 SEAWARD [Seaward Electronics Inc.], SE1051 Datasheet - Page 5

• Manufacturer Part Number: SE1051
• Description: Constant Voltage and Constant Current Controller
• Manufacturer: SEAWARD [Seaward Electronics Inc.]

Start Up and Short Circuit Conditions
Under start-up or short-circuit conditions the SE1051 does not have a high enough supply voltage. This is due
to the fact that the chip has its power supply line in common with the power supply line of the charger system.
Consequently, the current limitation can only be ensured by the primary PWM module, which should be
designed accordingly.
If the primary current limitation is considered not to be precise enough for the application, then a sufficient
supply for the SE1051 has to be ensured under any condition. It would then be necessary to add some
circuitry to supply the chip with a separate power line. This can be achieved in numerous ways, including an
additional winding on the transformer.
The following schematic shows how to realize a low-cost power supply for the SE1051 (with no additional
windings).
Please pay attention to the fact that in the particular case presented here, this low-cost power supply can
reach voltages as high as twice the voltage of the regulated line. Since the Absolute Maximum Rating of the
SE1051 supply voltage is 18V, this low-cost auxiliary power supply can only be used in applications where
the regulated line voltage does not exceed 9V.
Revision 12/4/2008
Rs
Cs
Preliminary and all contents are subject to change without prior notice.
© Seaward Electronics, Inc., 2006. • www.seawardinc.com.cn • Page 5
1.210 V
240mV
Ictrl
Vcc
Rsen se
Vsense
CCL
VCL
SE1051
Fig. 3
Ric2
Vout
GND
Vctrl
22 pF
Rout
Ric1
Cic1
C2
2.2nF
To prim a ry
Rvc1
Cvc1
2.2nF
R2
R1
Vout+
Vout-