UC3843 Switching Mode Power Supply (SMPS) Circuit 12V, 10A

UC3843 Switching Mode Power Supply (SMPS) Circuit 12V, 10A

UC3843 switching power supply for 12V projects

On this blog we'll look at a switch mode power supply based on the UC3843 PWM driver IC. The feasible power output is approximately 120W (12V, 10A). The project requires only a handful of components and the circuit is of moderate complexity. It follows a Flyback SMPS topology, the output voltage can be easily modified for any value from 5-30V by simply altering the secondary windings.

Video Tutorial (www.youtube.com/@electrobuff)

UC3843 IC Overview

The UC3843 is a popular integrated circuit (IC) commonly used in power supply applications. It is part of the UC384x family of pulse-width modulation (PWM) controllers designed for switching power supply applications. Here's an overview of the UC3843 IC, including its applications, pros and cons, and pinout with pin functions:

Applications:

1. Switched-Mode Power Supplies (SMPS): The UC3843 is widely used in the design of flyback, forward, and push-pull switch-mode power supplies.

2. Battery Chargers: It can be employed in the design of battery chargers, providing a regulated and efficient charging process.

3. LED Drivers: The UC3843 can be used to design LED drivers for efficient power regulation and control.

4. Voltage Regulators: In applications where precise voltage regulation is required, the UC3843 can be used to design voltage regulators.

5. Inverters: It is also used in inverter circuits for converting DC power to AC power in applications like uninterruptible power supplies (UPS) and solar inverters.

Pros and Cons:

Pros:

• Versatility: The UC3843 is versatile and can be used in a variety of power supply and control applications.
• Wide Operating Voltage Range: It can operate over a wide voltage range, making it suitable for different power supply designs.
• Reliability: When properly implemented, it can provide stable and reliable power regulation.

Cons:

• External Components Required: The UC3843 requires external components, including resistors, capacitors, and inductors, to function as part of a complete power supply circuit.
• Not Ideal for High-Frequency Applications: While suitable for many applications, the UC3843 may not be the best choice for very high-frequency applications.

Pinout and Pin Functions:

The UC3843 typically comes in an 8-pin dual-in-line (DIP) package. Here's a brief overview of the pinout and pin functions:

1. Pin 1 (CS): Current Sense Input. Connects to the sense resistor to monitor the output current.

2. Pin 2 (VFB): Voltage Feedback Input. Connects to a voltage divider that samples the output voltage for feedback control.

3. Pin 3 (RT/CT): Oscillator Timing Resistor and Capacitor Connection. Connects to external components to set the frequency of the internal oscillator.

4. Pin 4 (GND): Ground. Connects to the ground reference of the circuit.

5. Pin 5 (Vcc): Supply Voltage Input. Connects to the positive supply voltage, typically between 8V and 30V.

6. Pin 6 (OUT): Output. Provides the PWM output signal to drive an external power transistor.

7. Pin 7 (Discharge): External capacitor connection for the discharge of the timing capacitor during the discharge portion of the oscillator cycle.

8. Pin 8 (Error Amplifier Output): Output of the error amplifier, which compares the feedback voltage to the reference voltage.

Understanding the functions of each pin is crucial for designing and configuring the UC3843 in a specific application. The external components connected to these pins, such as resistors, capacitors, and inductors, will determine the operating characteristics of the IC in a given power supply circuit. For detailed specifications and application information, it's recommended to refer to the datasheet provided by the manufacturer.