slow start needed in TOPSWITCH
Posted by: rpaitich@gmail.com
on
I need to apply power (ca. 30 watts; universal off-line) to a device that starts slowly, and the FB is not a normal voltage FB. The TOPSWITCH family shuts off quickly if it doesn't get FB. I appreciate any simple ideas to keep the TOPSW alive until my FB takes over and controls things.
Comments
PI-Sarek,
Thanks for your note; this looks promising.
Ron
Hi,
It is possible to design a circuit with a "soft finish" characteristic.
Please see the example in the link below for reference:
http://www.powerint.com/sites/default/files/images/schematics/di142.gif
In this example diode D9, capacitor C20 and resistor R16 form the soft finish circuit. At start, capacitor C20 is discharged. As the output voltage start rising, charging current of C20 through the optocoupler diode creates a false sense of feedback resulting in a gradual increase in output voltage. Once the power supply reaches regulation and the feedback circuit starts working normally, C20 charges to the rail to which R16 is connected and the reverse biased diode D9 prevents any effect of this circuit on the normal operation. Capacitor C20 discharges through resistor R16 when the power supply is switched off thereby ensuring a "soft finish" at the next power-up.
I hope you find this useful. You may be able to modify this idea to suit your specific requirement.
Regards
PI-Sarek