TOP257GN

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The TOP257GN family of ac/dc controllers are high voltage integrated circuit devices used in offline switchers, such as standby and offline power supplies, whiteware, lighting and communication equipment. It provides the converter with a safe and efficient electronic solution that helps reduce its complexity, cost and size.

Working principle of TOP257GN

The TOP257GN family works by efficiently controlling the basic switch-mode power supply (SMPS) functions. It features a low-side MOSFET, allowing pulse width modulation (PWM) switching of a single-ended primary inductor converter (SEPIC) circuit that utilizes oscillator-controlled switching frequencies and current mode control. The device provides the system with high current performance through the use of patented valley-mode PWM controlled operation, providing "soft switching" of the MOSFETs. The TOP257GN devices are designed to be pin-to-pin compatible with the TOPSwitch-J devices and the TOPSwitch-HX devices, making it easy for users to easily migrate from the older devices to the newer and more efficient TOP257GN family.

TOP257GN Application Field

The TOP257GN family is mainly targeted at low-cost, low-power, universal ac/dc applications. These include whiteware and kitchen appliances, small home appliances, security systems, smart office/home lighting, handheld instruments, telecom systems, portable media players, battery powered products, and defense/space systems. The low-side MOSFET on the TOP257GN enables it to be used in both single and multiple output applications, with each output independently regulated. It also supports both ac/dc and dc/dc topologies, allowing freedom for designers to choose the best suitable power topology for the particular application.

The TOP257GN family features an innovative, multi-level power-ring architecture that simplifies the development of various alternative power solutions. This advanced topology distributes each of the power converter\'s core functions, such as PWM control, output voltage feedback, and current sense across multiple, independent power ring stages. This keeps all high-voltage, low-voltage, and digital power rings isolated from each other, simplifying layout, reducing device size, and minimizing electromagnetic interference (EMI). What’s more, it is particularly suitable for applications that require multiple outputs, or output voltage sequencing, or both.

Features of TOP257GN

The TOP257GN family offers numerous features that make it attractive for ac/dc applications. It includes all the necessary features of a basic, but efficient, and reliable SMPS, such as auto stand-by mode, input under-voltage lockout and over-current protection. It also includes built-in overvoltage protection, over-temperature protection, and cycle-by-cycle current-sense protection. The device is available in both Standard and High-Voltage versions, and in a range of package options, including post-mountable and surface-mountable packages.

The TOP257GN family is highly efficient, with a peak efficiency of up to 96%. It has a frequency dithering feature that allows the device to adapt its frequency cycle to the load, depending on the switching conditions. Its PWM control feature supports a wide range of input voltage from 42V down to 8V. It also features a patented safe operating area (SOA) for the MOSFETs, providing superior protection against overload, over-current, and short circuit conditions.

The TOP257GN family is ideal for applications operating at low power levels. It offers a low standby power of less than 250mW, and it is capable of achieving a high no-load efficiency of over 81%. In addition, it is stable and compatible with a wide range of output capacitors, allowing cost-effective designs with low-ESR capacitors or capacitors with high ripple current capabilities.

Conclusion

The TOP257GN family of ac/dc controllers are high-performance, efficient, and cost-effective solutions for use in a variety of applications, such as whiteware, lighting, home and office applications, and communication systems. By offering a range of features and benefits, such as low standby power, high efficiency, and noise-free operation, it simplifies the design process, helping to reduce the cost of the end systems. It is also easy to migrate from older, less efficient topologies to the more efficient TOP257GN family, making it a sound choice for designers who require reliable and cost-effective solutions.

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