UCC3817DWTR

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The UCC3817DWTR is a high voltage, fixed frequency pulse width modulator (PWM) integrated circuit (IC). It is designed for applications requiring the near unity power factor in ac-dc power supplies and rectifiers. It is particularly suited for applications where high peak power, fast transient response, and loop control stability are required. The UCC3817DWTR incorporates a low-side power MOSFET and a voltage controlled oscillator (VCO) which is phase locked to an input voltage. It also includes a voltage loop feedback network, an error amplifier, a temperature compensated current source, and an over temperature protection circuit.

The UCC3817DWTR is used mainly in applications requiring power factor correction (PFC). The main purpose of PFC is to reduce the harmonics produced by operation at other than the fundamental frequency and to keep voltage load at near unity. This helps to reduce the reactive power in the system resulting in lower losses, higher efficiency and better overall power quality. The UCC3817DWTR uses a pulse width modulator (PWM) to convert an input AC voltage into a DC voltage that is regulated at a desired level. This device operates in a continuous conduction mode (CCM) and uses an average current mode control loop to regulate the output voltage.

The UCC3817DWTR has two main blocks: a low-side power MOSFET and a voltage control oscillator (VCO). The power MOSFET switches the primary side current with a fixed frequency (50kHz to 500kHz) and modulated duty cycle (duty ratio). The duty cycle is the ratio of the switching window to the entire switching period. The VCO is used to generate the pulse timing signals to the power MOSFET. It provides a fixed frequency clock signal, which is phase locked to a voltage on the primary side of the transformer by means of a voltage loop feedback network. This network consists of a series of resistors and capacitors connected in a voltage divider configuration.

The UCC3817DWTR also includes an error amplifier for loop gain adjustment and a temperature compensated current source for bias current adjustment. The over temperature protection circuitry is provided to protect the device from overexposure to high temperature conditions. It prevents self-oscillation and N-type MOSFET protection in power circuits. It also offers under-voltage lock out (UVLO) and over-voltage protection (OVP).

The UCC3817DWTR is widely used in ac-dc power supplies and rectifiers. The high-voltage tolerance of the power MOSFET and the average current mode control provide excellent stability and fast dynamic response, which makes it suitable for applications requiring high peak power and fast transient response.

The UCC3817DWTR is a robust and cost-effective solution for power factor correction in power electronics applications. It offers high voltage tolerance, fast response, and excellent stability. In addition, it incorporates temperature protection and over-voltage protection. The combination of features makes it suitable for applications requiring power factor correction and improved system efficiency.

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