PWM (Pulse Width Modulation) control chips are the "brains" of switching power supplies, regulating the output voltage by adjusting the duty cycle of the switching transistor. These integrated circuits generate square-wave signals with variable pulse widths, where the duty cycle (the ratio of on-time to the total switching period) determines the amount of energy transferred to the output. By comparing the feedback voltage (proportional to the output) with a reference voltage, the PWM controller adjusts the duty cycle to maintain a stable output voltage, even with varying input voltages or load currents.

Common PWM control chips include the UC3842, a popular choice for low-power applications, which features an internal oscillator, error amplifier, and current-sense comparator for overcurrent protection. More advanced chips, such as the LM5022 or LT3845, offer higher switching frequencies (up to several megahertz), synchronous rectification support, and adaptive dead-time control to prevent shoot-through in half-bridge or full-bridge topologies. Some modern controllers also integrate digital interfaces (e.g., I2C) for programmability, allowing for dynamic adjustment of output voltage and protection parameters.

The choice of PWM chip depends on factors like input voltage range, output power, switching frequency, and required protection features, all of which influence the overall efficiency and reliability of the switching power supply.

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