jit_singh_tara
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smps design for (vcc,+5v,+14v dc)
Dear Friends ,
I am new to smps design , You can say a beginner . I have an application where i need 3 supplies :
Vcc(+5v) ,+5v , +14V (driving relays) .
For Mcu : I need to save some variables in eeprom on power off .Currently i used to do this by following method:
I used to have 3 supplies from a transformer rating : 12 - 0 - 12 , 0 - 12 (350 mA)
12-0-12 winding used to generate vcc and +5v both from separate 7805 regulator.
0 - 12 winding to generate +14v for relay switching.
a. Vcc from 7805 (with a big cap added) so that in case of power failure mcu should get some extra time before turning off.
b.+5V another supply from 7805 which goes off immediately on power off . This supply was connected after dropping down using resistors to the base of transistor switching ckt so that it just remains on , any voltage lower than this dropped voltage would change the state of the transistor so that when power goes off the transistor gives a high connected to INT pin(21) of pic mcu 16f886 .
Basically i was detecting power off using transistor as a switch and connecting it to int pin so that on getting interrupt i could save some variables in eeprom.
3. UNregulated +14v dc for switching relays.
Now I need to design a system where i need to switch six 12v sugar cube relays , sense power off condition to save variables in eeprom .
But i need to have smps power supply for driving the same because of the space constraint.PLease suggest how to proceed.
Dont have hands on experience on designing smps .Or smps transformer ?
PLease suggest how should i proceed to generate these 3 voltage vcc, +5v , +14 volt using smps.
And can i add big cap on vcc generated from smps to implement the same logic of memory saving here , or there is some better method of doing it......
Dear Friends ,
I am new to smps design , You can say a beginner . I have an application where i need 3 supplies :
Vcc(+5v) ,+5v , +14V (driving relays) .
For Mcu : I need to save some variables in eeprom on power off .Currently i used to do this by following method:
I used to have 3 supplies from a transformer rating : 12 - 0 - 12 , 0 - 12 (350 mA)
12-0-12 winding used to generate vcc and +5v both from separate 7805 regulator.
0 - 12 winding to generate +14v for relay switching.
a. Vcc from 7805 (with a big cap added) so that in case of power failure mcu should get some extra time before turning off.
b.+5V another supply from 7805 which goes off immediately on power off . This supply was connected after dropping down using resistors to the base of transistor switching ckt so that it just remains on , any voltage lower than this dropped voltage would change the state of the transistor so that when power goes off the transistor gives a high connected to INT pin(21) of pic mcu 16f886 .
Basically i was detecting power off using transistor as a switch and connecting it to int pin so that on getting interrupt i could save some variables in eeprom.
3. UNregulated +14v dc for switching relays.
Now I need to design a system where i need to switch six 12v sugar cube relays , sense power off condition to save variables in eeprom .
But i need to have smps power supply for driving the same because of the space constraint.PLease suggest how to proceed.
Dont have hands on experience on designing smps .Or smps transformer ?
PLease suggest how should i proceed to generate these 3 voltage vcc, +5v , +14 volt using smps.
And can i add big cap on vcc generated from smps to implement the same logic of memory saving here , or there is some better method of doing it......
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