# Power Supply Simulate

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#### Suraj143

##### Active Member
How can this output voltage go beyond 6.2V? If there is a zenner diode...!!

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#### Pommie

##### Well-Known Member
Did you intend to attach a schematic?

Mike.

#### Suraj143

##### Active Member
Hi I attached my diagram.

#### Pommie

##### Well-Known Member
Have you checked the current through the zener?

Mike.

Here it is.

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#### Pommie

##### Well-Known Member
You have 5A at 9V (45W) in a device rated at 300mW. The resistance of the device at that current isn't even in the datasheet.

Mike.

#### crutschow

##### Well-Known Member
Don't you think 4.7A is a little excessive for a 250mW diode?
In real life that zener would be smoke.

Back to the drawing board.

#### Suraj143

##### Active Member
Ok so what do I have to change?

#### Nigel Goodwin

##### Super Moderator
Ok so what do I have to change?
How about doing electronics and not computer 'games'

#### Pommie

##### Well-Known Member
You could start by reading this document. It has a very similar circuit on page 2 along with the calculations necessary.

Mike.

#### MikeMl

##### Well-Known Member
For starters, make R1 = 1Meg (1000000) Ohms, instead of 1m (0.001) Ohms. In Spice, little m is milli, while Meg is mega... Also, Sine Voltage sources are specified in peak Volts, not RMS, so you have to multiply 230*1.414. I love {} curly braces...

Here it is again, with the first order problems fixed. I also wanted to see how much current can be delivered by this off-line power supply, so I added a stepped resistive load of 200, 400, 600, and 800Ω. Note it does ok at 200Ω to 600Ω, but a load of 800Ω is questionable.

The next potential problem to check is what happens if you plug in this supply at the instant that the line voltage is at its peak value of ~330V. Here I show the peak in-rush current if the switch is closed at the worst possible time. Will R2, C1, and D2 stand occasional 7A peak currents?

At what time would you close the switch to check the peak current through D1? What is max peak current that could occur?

Simulation is very useful to answer questions about a circuit. You have to learn the tool to make it work for you, and you also have to subject the simulated results to a smell test. For example, it is obvious (to me at least) why the Zener current was too high GIGO ...

Attached are the two running simulations...

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#### crutschow

##### Well-Known Member
How about doing electronics and not computer 'games'
I take it you view simulation as a computer "game"?

#### Nigel Goodwin

##### Super Moderator
I take it you view simulation as a computer "game"?
Yep, it's not doing electronics

#### audioguru

##### Well-Known Member
A Simulation program (computer game) has no common sense. It showed 45W in a little 300mW zener diode and gave no warning because it didn't care.

#### MikeMl

##### Well-Known Member
A Simulation program (computer game) has no common sense. It showed 45W in a little 300mW zener diode and gave no warning because it didn't care.
So what do you want? An animation with a puff of smoke? During a simulation run, LTSpice intrinsically saves the power dissipated by every component, along with the voltage at every node, and the current in every branch. You just have to ask it for the info, or plot it.

It is the user of the simulation program that has no common sense, but guess what, that same user wouldn't have a clue until the user saw the puff of smoke coming from the real part in a breadboard.

#### Suraj143

##### Active Member
Ok thank you everybody.

@ Mike

You are correct.After changing the 1Meg resister to uppercase the problem solved.I have limited knowledge on this tool

Actually I need to check the 230V power is available or not & take an isolated signal to another circuit.Attached the final diagram.

In this case the maximum load will be LED load, that is 10mA. Is this load enough for the circuit..!!!

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#### crutschow

##### Well-Known Member
Yep, it's not doing electronics
Well, then let's whip out the old slide-rule and get started on that valve design.

#### JimB

##### Super Moderator
let's whip out the old slide-rule and get started on that valve design
Sounds good to me!
JimB

#### Ian Rogers

##### User Extraordinaire
Forum Supporter
I take it you view simulation as a computer "game"?
Nigel likes the smell of getting it wrong once in a while... I have been burnt by software sim... As soon as I have something, I'll build and test!!

#### cowboybob

##### Well-Known Member
Did a SIM (TINA TI) of a 555 Latch that worked "perfectly" with the circuit as below (note arrow on "Reset" line):

On real life breadboard, the latch did not always reset.

And all was well.

As Ian counsels:
... As soon as I have something, I'll build and test!! ...