first electronic design thing (bridge rectifier) - Electronic Circuits Projects Diagrams Free

infested_ysy · 13th September 2006, 03:40 AM

Hey there,

I just started my electronic lessons in my university, and as my first assignment, I'm supposed to build an AC rectifier, from 240V 50hz input to 24V DC, with 3% max ripple factor and 250mA max load current.

I tried using Multisim to simulate the circuit, and here's what I get:

Am I doing it right? Also, what does the transformer "PQ_4_120" means? I tried googling it, and I found nothing meaningful :/. The load current is the current across the capacitor, is it? I get 3.076A according to multisim.

Help please? D:

audioguru · 13th September 2006, 04:00 AM

Ask your teacher what the transformer sim numbers are in Multisim.

Your circuit doesn't have a load, therefore it doesn't have any output current. Ohm's Law says a resistor across the output and ground can be its 250mA load. It is 24V/250mA= 96 ohms. Your 62k resistor has a value so high that the voltage divider action of it with the load reduces the output voltage to only 37mVDC instead of 24VDC. When you remove the useless resistor, you will find that your 1uF filter capacitor has a value far too small to reduce the high ripple voltage.

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13th September 2006, 03:40 AM	(permalink)
infested_ysy	first electronic design thing (bridge rectifier) Hey there, I just started my electronic lessons in my university, and as my first assignment, I'm supposed to build an AC rectifier, from 240V 50hz input to 24V DC, with 3% max ripple factor and 250mA max load current. I tried using Multisim to simulate the circuit, and here's what I get: Am I doing it right? Also, what does the transformer "PQ_4_120" means? I tried googling it, and I found nothing meaningful :/. The load current is the current across the capacitor, is it? I get 3.076A according to multisim. Help please? D:

13th September 2006, 04:00 AM	(permalink)
audioguru	Ask your teacher what the transformer sim numbers are in Multisim. Your circuit doesn't have a load, therefore it doesn't have any output current. Ohm's Law says a resistor across the output and ground can be its 250mA load. It is 24V/250mA= 96 ohms. Your 62k resistor has a value so high that the voltage divider action of it with the load reduces the output voltage to only 37mVDC instead of 24VDC. When you remove the useless resistor, you will find that your 1uF filter capacitor has a value far too small to reduce the high ripple voltage. __________________ Uncle $crooge