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inverter and transformer rating....

ahmed hassan

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i have one question related to my circuit that i attached...

>>here some details about the circuit:

This is AC circuit mini inverter 10W - 30W. It Converts 12VDC to 220VAC Output 10W to 30W . Use easy Circuit Square Wave Oscillator Generator 50Hz. So Boost up Current High by D313 or H1061 or TIP41, Drive Transformer output 220V 50HZ From Voltage Supply 12V 1A - 2A.

my friend already succeed developed the circuit by using 12V/240V 0.5A transformer. the question is:

1. if want the output current higher than 0.5A (let say 1A), do i need to change the transformer rating from 0.5A to 1A?

2. the details of the circuit say that input voltage and current is 12V and 1-2A, but they are using 0.5A of fuse...i seem not understand how this happen because what i know the fuse is going to blow immediately by the effect of over the fuse rating .. or i misunderstood here?



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The 2SD313 output transistors operate poorly above 1A but still have some gain at 2A.
Then the output from the inverter will be 16W.

The 2SC1815 oscillator transistors have a max allowed reverse emitter-base voltage of only 5V but will have avalanche breakdown in this circuit that is missing protection diodes.

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about the 1st question, here i edited because of typing error.

1. if i want the output current higher than 0.5A (let say 1A), do i need to change the transformer rating from 0.5A to 1.0A?

because i use motor (aquarium water pump) as load at the output inverter and the rating is 240V and 35W. base on my calculation, the current is 0.145A. what i know is the motor need inrush current to start operate. so, the total current is 0.145x7=1.02A. that why i need to increase the current up to 1A. or there is another way to increase the current?


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You should use MOSFETs instead of BJTs as they have a lower voltage drop.

Here's a schematic I found using Google.

You don't have to use all four MOSFETs, two will do as it's only lower power. I'd recommend using a 9V transformer because it's easier to get hold of and will give you closer to 12V out.


If the output power is 35W, the input power will be 42W (assuming 80% efficiency) because the using a centre tapped winding increases the copper losses you need to overrate it by √2 which means I would suggest using a 5A 9V-0-9V transformer.

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