Mengenal cara kerja switch-mode power supply

Summary

This video script explains the workings of a Switch Mode Power Supply (SMPS), focusing on the conversion of AC to DC and vice versa. The process involves multiple steps, including transforming AC to DC, oscillating it back to AC at high frequencies, and then converting it into stable DC output. Components like resistors, diodes, capacitors, transistors, and transformers work together to ensure smooth operation. The video also highlights the importance of feedback circuits to regulate voltage, ensuring the system provides a constant 5V DC output, making it more efficient compared to traditional power supplies.

Takeaways

• 😀 SMPS (Switched-Mode Power Supply) converts AC (Alternating Current) into DC (Direct Current) through a multi-step process, not as straightforward as it may seem.
• 😀 The process starts by converting AC to DC, then to high-frequency AC, and back to DC again.
• 😀 A typical power adapter changes 220V AC to 5V DC, with components like diodes, capacitors, resistors, and a transformer.
• 😀 The AC input passes through a resistor (260 ohms), diodes (like N4007), and a filter capacitor (2.2 µF, 450V) to convert AC to DC.
• 😀 The high-frequency AC is created by an oscillator circuit, using transistors (S8050, 13001) and diodes (1N4148) to generate frequencies between 15-50 kHz.
• 😀 The transformer in the circuit consists of primary, secondary, and auxiliary windings, with the auxiliary winding powering the oscillator.
• 😀 A feedback loop with optocouplers and diodes (like 1N5819) regulates the output voltage and prevents overvoltage.
• 😀 Capacitors (22 µF, 50V) and resistors help stabilize the voltage, while the diodes in the secondary circuit convert the AC to stable DC.
• 😀 The feedback system uses a Zener diode (4.2V) to control the output voltage, ensuring it doesn't exceed the set value (e.g., 5V).
• 😀 SMPS is more efficient than conventional power supplies because it uses high-frequency oscillation instead of low-frequency AC, reducing the size and weight of transformers.

Q & A

What is the primary function of an SMPS (Switch Mode Power Supply)?

The primary function of an SMPS is to convert alternating current (AC) into direct current (DC), while efficiently regulating and providing stable output voltage for powering electronic devices.

How does the process of AC to DC conversion occur in an SMPS?

In an SMPS, AC voltage first passes through a bridge rectifier consisting of four diodes (N4007), which converts it into DC. A filter capacitor (450V, 2.2µF) smooths out the DC signal.

Why does an SMPS use high-frequency AC instead of the standard 50-60 Hz AC for power conversion?

SMPS uses high-frequency AC (15-50 kHz) because it allows for a smaller transformer size compared to conventional power supplies that operate on the lower frequency of 50-60 Hz from the power line.

What role does the transformer play in an SMPS circuit?

The transformer in an SMPS circuit steps up or steps down the high-frequency AC voltage, which is essential for adjusting the voltage to the required levels for the output.

What is the significance of the feedback loop in an SMPS?

The feedback loop, which includes components like the optocoupler and Zener diode, helps regulate and stabilize the output voltage by adjusting the circuit's operation based on the output conditions.

What components are involved in the oscillation stage of an SMPS?

The oscillation stage of an SMPS involves transistors (such as S8050 and 13001), a high-frequency transformer, diodes, capacitors, and an optocoupler. These components work together to convert DC to high-frequency AC.

How does the optocoupler function within the SMPS circuit?

The optocoupler in an SMPS transmits feedback signals without direct electrical contact. It uses an LED to activate a phototransistor, allowing the circuit to adjust and regulate the output voltage.

What happens when the output voltage exceeds 5V in an SMPS?

When the output voltage exceeds 5V, a Zener diode (with a 4.2V breakdown voltage) triggers the optocoupler to reduce the voltage, thereby ensuring the system stabilizes and does not exceed the desired output.

Why is the resistor (260kΩ) included in the AC input stage of an SMPS?

The 260kΩ resistor acts as a protective element. It prevents excessive current from damaging the circuit by limiting the current during initial power-on and acts as a fuse to prevent overloading.

What is the purpose of the filter capacitor in an SMPS?

The filter capacitor smooths the rectified DC voltage to reduce ripple, ensuring the output voltage is clean and stable for powering electronic devices.