inverter Circuit using SG3524

Introduction and Video Overview

The video introduces the topic of designing an inverter using the SG3524 IC. The viewers are encouraged to follow the video carefully for a better understanding. The video will cover various sections including the input filter, oscillation circuit, driver section, transformer section, output section, and feedback section.

Designing the Input Section

• The input section starts with the battery positive (B+) connection.

• There is a 12V regulator instead of a 5V regulator.

• Two 10uF capacitors are used for smoothing the current flow during inversion to maintain battery stability.

• A cutoff switch is connected to V+ to shut down the system when turned off.

Understanding the Oscillation Circuit

• Pin 1 of SG3524 is used for feedback voltage correction.

• Pins 1 and 2 are operational amplifiers that balance the input and output voltages at either 220V or 110V depending on standby mode.

• Feedback helps maintain output voltage stability as battery voltage drops during discharge.

Exploring Pin Functions in Oscillation Circuit

• Pin 3 serves as an oscillator output for connecting external oscillators if needed.

• Pins 4 and 5 are grounded for loop connections.

• Pins 6 and 7 control frequency settings (50Hz or 60Hz) through a variable resistor (470k or adjustable).

• Capacitor C1 (104 or non-polarized capacitor) is recommended for pin 7 to avoid high-frequency switching issues.

• Resistor adjustment from pin 6 to ground can be set around 140k for desired frequency range.

Understanding Additional Pin Functions

• Pin 9 serves as a composition pin for soft start functionality, gradually powering up the inverter upon startup.

• Capacitor value selection affects soft start duration (e.g., 4.7uF for faster startup).

• Pin 10 is connected to the battery low circuit (not ground) and determines when the IC shuts down based on an analog signal (between 3V and 5V).

Conclusion

The video concludes by explaining that pin 10 should not be connected to ground but rather to the battery low circuit. This connection determines when the IC shuts down based on an analog signal within a specific voltage range. The video suggests further exploration in the next video for connecting pin 10 to the battery low circuit.

Timestamps are approximate and may vary slightly depending on the source video.

New Section

This section discusses the importance of maintaining equal voltage outputs on pin 11 and pin 14 of the IC. If there is a significant difference in voltage between these pins, it indicates a faulty IC.

Voltage Output Discrepancy

• The voltage difference between pin 11 and pin 14 should not exceed 0.5 volts.

• Pin 12 serves as the collector for pin 11, while pins 13 and 15 also act as collectors within the IC.

• The IC utilizes transistors to generate output signals and provide a stable reference voltage at pin 16.

• The recommended MOSFETs for this circuit are IRFZ44N, but alternatives like IRF3205 or IRFP250 can be used based on the inverter's capacity.

New Section

This section explains the purpose of resistors connected to the gates of MOSFETs and introduces a shutdown resistor to prevent open circuits during switching.

Gate Resistors and Shutdown Resistor

• The resistors (11k) connected to the gates (pin 14 and pin 11) help control current flow when driving MOSFETs without dedicated drivers.

• It is advisable to use low resistance values such as 4.7 ohms, 10 ohms, or even up to 100 ohms.

• A shutdown resistor (22k) ensures that no residual charge remains when the oscillator stops switching, preventing open circuits during switching.

• Instead of using a 22k resistor, a lower value like a 10k resistor can be used depending on specific design requirements.

New Section

This section provides information about the transformer used in the circuit and suggests additional components for smoothing and filtering purposes.

Transformer and Additional Components

• The recommended transformer is a center-tapped 12V transformer, with 12V on each side of the center tap.

• The output voltage of the transformer is approximately 220V, which can be further smoothed using a capacitor (0.1 microfarad, 400V) connected across the output.

• A fuse (16A) can be added based on the inverter's capacity to protect against overcurrent situations.

New Section

This section discusses how to calculate the required capacity for designing an inverter and introduces a feedback circuit using a small transformer.

Inverter Capacity Calculation and Feedback Circuit

• The calculation of inverter capacity involves determining the number of MOSFETs required and selecting an appropriate transformer size.

• Further calculations related to capacity are not provided in this transcript.

• A feedback circuit utilizes a small 12V transformer connected to the output of the inverter.

• The output from this small transformer is then connected to a full bridge rectifier, followed by filtering components such as capacitors (10 microfarads) and resistors (4.7k).

• Adjusting a variable resistor (10k) connected to pin one of the IC allows for fine-tuning until an output voltage of 220V is achieved.

New Section

This section concludes the discussion by encouraging viewers to leave comments or questions while emphasizing that proper adjustment ensures correct feedback and voltage regulation.

Conclusion

• Viewers are encouraged to leave comments or questions regarding the content discussed in the video.

• Proper adjustment of components, particularly the variable resistor, ensures accurate feedback and voltage regulation within the circuit.