When we need to use an inverter circuit diagram. Sometimes we cannot find it. But here is how to make inverter circuit within 5 minutes. In two simple inverter schematic diagram below. Just using two transistors, two resistors, and one transformer only. They can convert a battery 12v DC to 220VAC/120VAC to apply a small light bulb or a maximum 10 watts lamp.
They include two circuit ideas
1. Very Simple Inverter circuit using MJ2955 (PNP transistors)
2. Micro Inverter circuit diagram using TIP41 or 2N6121 ( Chayapol made its small size)
Very Simple Inverter circuit diagram using MJ2955
This is a simple inverter schematic diagram. I need to use a small light bulb at outdoor. Which it is no electricity, 220VAC.
My friend borrows mine 150 watts inverter. Which I used it in the car. It does works so well. So I do not have an inverter. Thus I need to build a new inverter in a hurry.
The main idea of the inverter circuit diagram
In this case, I do not need a high power and a long time using. Because I use the power of 10 watts for just a brief moment (30 minutes approximately).
Then, I look for all the parts in my store. I have a lot of MJ2955 power transistors.
Thus, I choose an inverter circuit diagram like Figure 1. It is so easy. It two MJ2955, two 68 ohms resistors, and one transformer only.
You see really it is possible!
The MJ2955 inverter circuit diagram
Both transistors and two resistors are set in an astable multivibrator mode. The power transistors drive the transformer. It converts DC pulse to AC high voltage.
Which it looks like a below inverter. But it uses PNP transistor and high power than one.
My friend that is a guru about power electrical tells me. This circuit style will not have capacitors. But it can generate the frequency. The transformer secondary works as a load that can transform electrical to high voltage, in this case, is 220V but not sure is 50Hz.
However, the frequency output does not need to use with the load.
Let’s build this circuit.
This circuit is very simple but tiny size. I assemble them on the heatsink and connects all wires as Figure in the video below.
As video I use 12V battery 2.5Ah size as a source, secondly, I measure output AC voltage is 225-volts. Next, I apply lamps to the circuit. The voltage lower to 190-volts and can keep up power.
The parts you need
Q1,Q2—MJ2955 or TIP2955 PNP power transistors = 2 Pcs.
R1,R2—68 ohms 2watts to 5 watts resistors = 2 pcs.
T1—12V CT 12V / 220V or 110V transformer = 1 pcs.
If you want 20 watts output, use 1A transformer.
Heatsink, 12V battery, etc.
Also, You may use the project below it looks great.
Micro Inverter circuit diagram using TIP41 or 2N6121
This circuit looks like above tiny inverter circuit above. Also, It converts 12V battery to ACV in range of 180V to 220V. At the output frequencies from 30Hz up to 65 Hz.
You can use it to general appliances under 10 watts. For example, Small fluorescent light bulb, LED lamps, timers, etc.
The LED save energy than fluorescent light bulb at same the lightness.
Also, this micro inverter circuit uses a normal transformer and dual NPN transistor. In assembling the circuit you just wiring the parts together by a leg to leg only. You may take about 5 minutes only to finish this circuit.
Note: Please read “Testing/application” below for real application.
The general inverter circuit uses an oscillator to drive a transformer with a power transistor.
Using dual transistors is push-pull switching, alternately works ON and OFF. Both transistors should have similar in a gain rate. But do not need the same.
How it works
When enter the power to the circuit. Either transistor will saturate (closed circuit) faster than one.
Suppose Q1 has closed the circuit first. The collector current of Q1, so it creates a magnetic field in the coil L2. Then, it gets more base voltage through R1. Q1 so quickly into a state of a closed circuit. Also, it makes Q2 is an opened circuit.
The condition is like this until the transformer core reaches saturation point. Thus, the current flows to R1 reduce until cannot make Q1 in closed circuit status. The Q1 is the opened circuit.
In opposite, while Q1 is slowly changing from the closed circuit into opened circuit status. Q2 will begin to conduct more currents. The current will flow through R2 to increase a bias current to Q2. It makes Q2 to be closed circuit quick.
Now, the current of the battery will flow to coil L1 in a reverse direction. It causes the voltage induction to be the opposite polarity in the secondary coil of a transformer.
The Q2 will still conduct current until the transformer core reaches saturation.
After that, this process of the closed-opened circuit between Q1 and Q2, will be the same again. As long as, DCV is fed into the circuit
The capacitor across primary of transformer makes the output AC voltage to be smoothed or low noise.
How to make inverter
For in the project, use a few components. So It has how wiring circuit below, without PCB layout. I suggest some making techniques, as follows.
1. Use a mica insulator insert between case and body of the transistor. Then, use a plastic insulator. Next, hold the transistor body with hex nut and metal screw, as the figure below.
2. Remember! Do not any lead of transistor touch to a case or short circuit between these lead.
3. Use ohmmeter check short circuit of various devices does not short circuit to a case as below.
I test working as follows step:
1. Get the 12V battery, 2.5Ah. Or 12VDC regulated power supply, the current is more than 2A for testing.
2. Use AC volts meter to measure by setting 500 VAC range or AC volts digital meter like I use.
3. Apply the 12 V battery to this project.
4. Measure the output voltage. You should read voltage between 220V to 330V.
After that, try to use this inverter circuit project to load, 3 watts LED lamp. Because of Low power consumption.
This circuit has the output power about 5 watts to 10 watts only.
As above video, LED lamp glows brightly for 3 hours. Because it uses 0.5A only.
I assemble parts include 2 x TIP41 with the heatsink, 1K-resistors on the universal PCB board.
Note: Since, I have limit parts so use near parts only. I use 0.75A, 9V CT 9V transformer and two pcs of TIP41.
If you want to use higher watts. You can change some parts.
In the event of adding power is 20 watts. It requires the transformer that provides the current over than 2A and changes R1 and R2 are 100 ohms 5W instead.
Q1, Q2—TIP41 or 2N6121, transistor NPN 40W 45V 4A
LED1—Red LED or as you need.
Resistors (0.5W +/- 5% Carbon)
C1—0.1uF 630V, mylar capacitor
T1—Transformer 220 VAC primary coil/10-0-10V, 750 mA- secondary coil
F1—Fuse- 0.5 A
AC- plug, mica insulator, LED, plastics, 12 VDC Battery, solid Wires no. 20 AWG length 1 feet, nut and screw, etc.
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