Hi, I have a 230V AC power supply at 50Hz. I also have a center-tapped transformer that steps down 230V to ±18V (i.e., +18V, 0V, -18V) with a current rating of 5 amperes. To power my electronics, I need DC outputs of +15V, -15V, +5V, +12V, and -12V. I wish to know

1) Which diode is best for a bridge rectifier?
I’m considering using the MBR20100 diode.

2) Should I use only a capacitor filter, or LC/CLC filters? What values should I choose? Simulations suggest larger values perform better.

3) Can I connect LM7815, LM7805, LM7808, and LM7812 in parallel at the positive output (Point A in the circuit image)? Similarly, can I connect LM7915 and LM7912 in parallel at the negative output (Point B)?

4) Do I need to attach a heatsink to the transformer? Conceptually, does the transformer only draw power when the electronic circuit is consuming current (i.e., when the regulators output power), or is it always active and generating heat even when idle?

5) Since I need more DC power from the positive rail than the negative rail, does that mean I need to dissipate more heat on the negative side, or just on the side where more power is used?

 

78XXX Voltage reglutor IC has 1A maxium current

 

1) Which diode is best for a bridge rectifier?
I’m considering using the MBR20100 diode.

That diode will work. Overkill, but it will work.

2) Should I use only a capacitor filter, or LC/CLC filters? What values should I choose? Simulations suggest larger values perform better.

I wouldn't bother with chokes (inductors). You have a lot of headroom for the regulators, so shouldn't need anything near 15,000uF.

3) Can I connect LM7815, LM7805, LM7808, and LM7812 in parallel at the positive output (Point A in the circuit image)? Similarly, can I connect LM7915 and LM7912 in parallel at the negative output (Point B)?

Yes.

4) Do I need to attach a heatsink to the transformer? Conceptually, does the transformer only draw power when the electronic circuit is consuming current (i.e., when the regulators output power), or is it always active and generating heat even when idle?

No.

5) Since I need more DC power from the positive rail than the negative rail, does that mean I need to dissipate more heat on the negative side, or just on the side where more power is used?

Just where the regulator is dissipating more power.

 

For CLC filter circuit i am thinking to take

• C1: 2200µF
• L: 50mH
• C2: 1000µF

but it don't give result in simulation

 

For CLC filter circuit i am thinking to take

• C1: 2200µF
• L: 50mH
• C2: 1000µF

but it don't give result in simulation

You probably already have 50mH in the transformer windings or leakage inductance. Don't bother with inductors. A 50mH inductor at 5A is about 100mm cube and will cost as much as your transformer, because not so many people know how to make them.
If you were making a power supply for any amplifier 75 years ago, before electrolytic capacitors became reliable, then it would have been a good idea, but not any more.

 

Have you considered adding also a +3.3 V output?

 

Have you considered adding also a +3.3 V output?

Now that TTL is nearly extinct, you don’t need much current on the 5V or 3.3V lines.
I would recommend deriving the 5V from one of the higher voltages using a simple switching regulator such as a LMR38010 or LMR38020, then deriving the 3.3V form Your 5V using a linear regulator such as LD1117 or LP2951. That gives an efficient 5V supply, and a nice, quiet accurate 3.3V for microcontrollers.