Easy 12V DC to 220V AC Inverter Circuit
Easy 12V DC to 220V AC Inverter Circuit
Inverter Circuit Diagram Overview
inverter circuit electrobuff.blogspot.com
The circuit is based on a classic astable multivibrator circuit using BJTs. The BD140 transistors act as current amplifiers to power the TIP142 power transistors gates. The transformer is a standard iron-cored transformer, the output voltage is dependent on the turns ratio and the input voltage.
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| Astable multivibrator inverter circuit electrobuff.blogspot.com |
An astable multivibrator is a type of oscillator circuit that generates a continuous square wave output without the need for an external triggering signal. It is often implemented using two bipolar junction transistors (BJTs) in a configuration known as a BJT astable multivibrator. The circuit relies on the switching behavior of the transistors to create a repetitive oscillation.
Here's how a basic two-BJT astable multivibrator works:
Components:
Two BJTs (Transistor Q1 and Q2): NPN transistors are commonly used.
Resistors (R1, R2, and RE): These resistors determine the biasing and timing in the circuit.
Capacitors (C1 and C2): These capacitors play a crucial role in determining the frequency of the oscillation.
Power Supply (Vcc): Provides the necessary voltage for the circuit.
Operation:
Initial State:
Assume one transistor, let's say Q1, is initially in the ON state (saturated), and the other transistor, Q2, is in the OFF state (cut-off).
The capacitor C1 charges through resistor R1 and forward-biased transistor Q1.
Charging Phase:
As capacitor C1 charges, the voltage across it increases.
Once the voltage across C1 reaches a threshold (determined by the base-emitter voltage of Q2), Q2 starts turning on.
Switching State (Transition):
As Q2 turns on, it pulls the collector voltage of Q1 low, forcing Q1 into the OFF state.
Simultaneously, capacitor C2 starts charging through resistor R2 and forward-biased transistor Q2.
Discharging Phase:
With Q1 off, C1 begins to discharge through resistor RE (emitter resistor) and the base-emitter junction of Q2.
As C2 charges, its voltage reaches a threshold, causing Q1 to start turning on.
Repeat:
The cycle then repeats, with the transistors alternately switching states in response to the charging and discharging of capacitors C1 and C2.
This continuous switching between the two states generates a square wave output at the collector terminals of both transistors.
Frequency Determination:
The frequency of oscillation is primarily determined by the values of resistors R1, R2, RE, and capacitors C1 and C2.
The formula for the frequency (f) is approximately given by:
Frequency = 0.693 / ((R1 + 2*R2) * C1)
Output Waveform:
The circuit produces a square wave output with a duty cycle close to 50%, making it suitable for applications like clock generators and pulse generators.
In summary, the two-BJT astable multivibrator circuit utilizes the charging and discharging of capacitors through transistors to create a continuous oscillation, generating a square wave output. The timing components (resistors and capacitors) control the frequency of the oscillation.
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