SG3525 900W Regulated Switching Power Supply for High Power Amplifi...

SG3525 Switching Mode Power Supply with Regulation (Dual Rail PSU)

Complete Circuit Diagram

SG3525 Regulated Switch Mode Power Supply with Dual Rail Output

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SG3525 PWM IC Overview:

The SG3525 is a widely used Pulse Width Modulation (PWM) controller integrated circuit designed for regulating power supply and inverter applications. Below is an overview of the SG3525 PWM IC, including its pinout, pin functions, internal block diagram, oscillator frequency and output frequency formula, feedback mechanism, features, as well as its pros and cons.

SG3525 PWM IC Pinout and Internal Block Diagram

SG3525 pwm IC Pinout and internal block diagram

1. Pinout: The SG3525 typically comes in a 16-pin dual in-line package (DIP) or surface-mount package. Here is the pinout:

• Pin 1: Error Amplifier Output (Comp)
• Pin 2: Inverting Input (Comp)
• Pin 3: Non-Inverting Input (Comp)
• Pin 4: Ground
• Pin 5: Offset Voltage Adjust (Vref)
• Pin 6: Shutdown
• Pin 7: Dead Time Control (CT)
• Pin 8: Output Control (RT)
• Pin 9: Output (Q)
• Pin 10: Output (Q)
• Pin 11: Vcc - Positive Power Supply
• Pin 12: Voltage Feedback Compensation (FB)
• Pin 13: Timing Resistor (RT)
• Pin 14: Timing Capacitor (CT)
• Pin 15: Oscillator Output
• Pin 16: Oscillator Input

2. Pin Functions:

• Comp (Pins 1, 2, 3, 12): Error amplifier inputs for feedback and compensation.
• Ground (Pin 4): Ground reference for the IC.
• Vref (Pin 5): Offset voltage adjustment for the error amplifier.
• Shutdown (Pin 6): Used to disable the PWM output.
• CT (Pin 7): Sets dead time in push-pull outputs.
• RT (Pin 8): Sets the frequency of the internal oscillator.
• Q (Pins 9, 10): Outputs for driving external components.
• Vcc (Pin 11): Positive power supply pin.
• FB (Pin 12): Provides feedback for voltage regulation.
• RT (Pin 13): Timing resistor for the oscillator.
• CT (Pin 14): Timing capacitor for the oscillator.
• Oscillator Output (Pin 15): Output of the internal oscillator.
• Oscillator Input (Pin 16): Input for the external oscillator.

3. Internal Block Diagram: The internal block diagram of the SG3525 includes an error amplifier, voltage reference, oscillator, PWM comparator, dead time control, and output drivers. The error amplifier compares the feedback voltage (FB) with a reference voltage (Vref) to control the duty cycle of the PWM output.

4. Oscillator Frequency and Output Frequency Formula: The frequency of the internal oscillator is determined by the values of the timing resistor (RT) and timing capacitor (CT). The formula for the oscillator frequency (fosc) is given by:

${�}_{\text{osc}}=\frac{1.2}{{�}_{�}\cdot {�}_{�}}$

The output frequency (fout) can be calculated using the formula:

${�}_{\text{out}}=\frac{{�}_{\text{osc}}}{2}$

5. Feedback Mechanism: The feedback mechanism involves the voltage feedback (FB) pin, where an external voltage divider is connected to provide feedback from the output. The error amplifier compares this feedback voltage with the reference voltage, adjusting the duty cycle of the PWM output to regulate the output voltage.

6. Features:

• Wide input voltage range.
• Adjustable dead time control.
• Internal voltage reference.
• Shutdown capability for power conservation.
• Pulse-by-pulse current limiting.
• Output can be configured for single-ended or push-pull operation.

7. Pros:

• Versatile and widely used in power supply and inverter applications.
• Adjustable parameters for fine-tuning.
• Efficient control of PWM signals.
• Shutdown feature for power-saving.

8. Cons:

• Requires additional external components for complete functionality.
• May not be suitable for low-power applications due to its higher current consumption.

In summary, the SG3525 PWM IC is a versatile controller commonly used in power supply and inverter designs. Its flexibility and adjustable parameters make it a popular choice among electronics designers, although it also requires additional external components for a complete power supply or inverter circuit. Understanding its pin functions, features, and feedback mechanism is essential for proper utilization in electronic designs.