• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Power Supply Simulate

Status
Not open for further replies.

Pommie

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

Back to the drawing board. :D
 

MikeMl

Well-Known Member
Most Helpful 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.

43.png

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?

43a.png

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...
 

Attachments

Last edited:

crutschow

Well-Known Member
Most Helpful Member

audioguru

Well-Known Member
Most Helpful 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
Most Helpful 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..!!!
 

Attachments

crutschow

Well-Known Member
Most Helpful Member

JimB

Super Moderator
Most Helpful Member

Ian Rogers

User Extraordinaire
Forum Supporter
Most Helpful Member
I take it you view simulation as a computer "game"? :rolleyes:
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
Most Helpful Member
Did a SIM (TINA TI) of a 555 Latch that worked "perfectly" with the circuit as below (note arrow on "Reset" line):
upload_2017-7-5_9-4-7.png

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

Added a cap on the breadboard to the "Reset" pin:
upload_2017-7-5_9-11-54.png
And all was well.

As Ian counsels:
... As soon as I have something, I'll build and test!! ...
Sound advice.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top