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UC3842BNG application field and working principle

UC2842BNG is a high performance current-mode pulse width modulation (PWM) controller with an internal frequency-compensation circuit, making it suitable for use in low-medium power, high frequency switching mode power supplies (SMPS) and other similar power converters. In general, UC3842 is intended as a control element to achieve regulation in switching power supplies.

Application Field

UC3842BNG is mostly used in offline flyback, forward and buck converters, DC to DC converters, the secondary side of phase-shifted full-bridge converters, and other circuit with current-mode control. It can be used for fixed frequency, such as 50KHz, for low-medium power SMPS, such as battery chargers, electronic lights and electrical motor control, as well as for current-mode control to achieve regulation in AD/DC SMPS.

Working Principle

The UC3842BNG is a high performance current-mode PWM controller which controls the output voltage by sensing the current in the power switch under load conditions. The current sense signal amplifies and filters by an op-amp and then is transformed to a voltage signal that can be sensed to generate feedback control. The UC3842BNG implements a fixed frequency oscillator composed of an external resistor and capacitor. This oscillator can be disabled if the user requires a synchronous rectifier, or uses external signals from a different regulator. The UC3842BNG also includes an optimal current limit circuit and an internal latch protection mechanism. In addition, the UC3842BNG includes anti-cross conduction circuitry, which prevents shoot-through in an AC-DC converter.

Conclusion

The UC3842BNG is a high performance current-mode PWM controller which can works perfectly in high frequency switching mode power supplies (SMPS) and other similar power converters. It\'s mainly used in the field of offline flyback, forward and buck converters, DC to DC converters, the secondary side of phase-shifted full-bridge converters, and other circuit with current-mode control. It works by sensing the current in the power switch under load conditions, implementing fixed frequency oscillator using an external resistor and capacitor, with optimal current limit circuit and an internal latch protection mechanism.

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