UC3853D

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UC3853D is a monolithic integrated circuit which is designed for incredibly efficient Power Factor Correction (PFC) applications. The UC3853D has the capability to perform automatic start-up and control operations in a Zero Voltage Soft Switching Converter (ZVMSS) topology. It has been manufactured to provide complete control solutions for applications such as AC/DC power supplies, computer peripheral power optimization and power factor correction.

The UC3853D is mainly employed in PFC enable power factor correction circuitry as it implements an integral-mode average current mode control with a single pulse fixed on time (SPOT) control. This type of control provides high efficiency power factor correction in a simple loop, preventing the distortion of input current waveforms and complying with virtually any standards required by government or utility companies. Moreover, the UC3853D’s wide operating range makes it suitable for input voltages of anywhere between 20VAC to 460VAC.

The working principle of the UC3853D is to measure the output current of the PFC converter and to adjust it accordingly, in order to stick as close as possible to a reference voltage signal. The signal that sets the desired value is compared to the output of the converter and when the signal is lower than the output from the converter, a “down signal” is sent to pulse width modulation (PWM) comparator, the signal is then low and the output of the converter pops.

By controlling the PWM comparator, the output of the converter is increased or decreased according to the comparison made between the input signal and the output signal of the converter. This ensures that the output of the converter is better regulated, providing higher power factor, higher efficiency and lower distortion percentage.

The UC3853D is provided with a lot of useful features that make it convenient and suitable to use as a PFC controller. It has active consumption current control that reduces power dissipation in the PWM comparator and can also detect single-cycle overloads and provide corresponding warning signals depending on the fault type. Other features include protection against over temperature, over voltage and line reflections, latched protection signals, a “Skip Mode” that reduces AC line disturbances, and an internal voltage loss compensation that maintains stable operation despite any line voltage variations.

The UC3853D is typically used for power factor correction in single-stage or multi-stage PFC converters. In a single-stage converter, during every half-cycle of the input AC, the output current of the converter follows a sinusoidal waveform. This type of converter is suitable for low power applications and has good rectification efficiency. The multi-stage converter is suitable for high power applications, where the output current waveform is closer to a square wave. The UC3853D is suitable for both types of converters and its automatic start-up and control features enables a stable and effective control of the output current.

To summarize, the UC3853D is a monolithic integrated circuit designed for incredibly efficient Power Factor Correction applications in either single-stage or multi-stage PFC converters. The IC provides complete control solutions and can implement an integral-mode average current mode control with a single pulse fixed on time (SPOT) control. It also has many useful features such as active consumption current control, protection against over temperature and line reflections, as well as a “Skip Mode” that reduces AC line disturbances. The UC3853D is therefore a perfect solution for applications such as AC/DC power supplies, computer peripheral power optimization and power factor correction.

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