Today, the smaller the volume and weight of the laptop, the tablet computer, or the larger cell phone needs a smaller, faster charging charger. But it is effective to convert AC to DC and the flyback converter with only a few components is the first choice topology to limit the volume of the battery charger. The development of the power adapter is also at the critical point. Can the active clamp flyback chipset break the volume limit?

"Smart phones need not only a smaller size, but also a larger power charger, while active clamp flyback energy releases more power in smaller space," Wu Weiqiang, director of business development at TI (TI), said at a media conference in Shenzhen. In particular, active clamp flyback eliminates switching losses and reduces EMI to achieve a zero voltage switch (ZVS) with appropriate control clamping; secondly, it can improve efficiency by circulating leakage of energy and transferring it to the output instead of dissipation to achieve higher efficiency than the traditional flyback converter; finally, a higher power density can be achieved. The lower switching energy consumption makes the switching frequency higher and makes the passive components smaller. The new chipset launched by TI combines the UCC28780 active clamp flyback controller and the UCC24612 synchronous rectifier controller with a working frequency of up to 1MHz, helping to halve the power size of the AC/DC adapter and the USB PD charger.

John Stevens, the TI high voltage product system and application engineering manager, further said: "with the launch of the UCC28780+UCC24612 chipset, the designers can intelligently control the active clamp flyback, which is impossible for the existing scheme. The new active clamp flyback solution can achieve high 1MHz efficiency in the AC/DC adapter and USB power supply charger. 1MHz is a very important indicator, which means that the adapter size can be reduced by 50%. Of course, TI is also the first company to launch such products. "

The advantages of UCC28780+UCC24612 are mainly embodied in three aspects: 1, power density doubling, accurate programmable over power protection providing unified heat dissipation design to achieve high power density; 2, high efficiency, multi mode control can achieve high efficiency, exceeding European CoC Tier2 and American DoE Level VI efficiency standard; 3, simplified design, through With the help of adaptive ZVS control, engineers can easily design the system through the combination of resistors. Through the data, the advantages of the chipset can be illustrated more intuitively. The chipset can reduce the occupancy space by 50%, the load efficiency of 95%, and the energy consumption less than 40mW.

Of course, the advantages of chipset are also closely related to the characteristics of each chip. Among them, the UCC28780 frequency can reach 1MHz, and it supports GaN or Si FET at the same time. The innovative ZVS algorithm provides the first class efficiency, and also has the advanced protection function, and can achieve high frequency no radiator. "The heat of the controller is mainly from loss, and the active clamp can store energy and transmit it to the output, instead of using the energy to deal with the leakage by using the resistance - Capacitor - diode or Zener clamp," Mr. Wu Weiqiang said to the question of why UCC28780 can achieve high frequency and no radiators. . The intelligent control clamp also provides a zero voltage switch. This eliminates the two main loss sources, minimizes loss and improves efficiency through circulating leakage energy, thus achieving high frequency non radiators and greatly reducing the size. " The UCC24612 controller Si FET supports up to 1MHz frequency, the wide voltage operation range is the highest support 200V, intelligent control provides near ideal diode simulation system, high performance, simplified design.

John Stevens also said: "TI is committed to providing a complete set of solutions from input to output to maximize the satisfaction of engineers. Therefore, for the design above 75W, the designer can also match the chipset with a new 6 pin PFC controller UCC28056 to achieve the high efficiency of all line voltages greater than 90% under the 10% load and the 25mW standby power consumption at the lowest 115Vin. The always opened PFC can start at the moment, reducing the number of components to let the system set up The meter is simpler, and there is no noise in the AC/DC application. " Based on UCC28056, it can simplify system design and provide industry minimum standby power for AC/DC applications, which can be applied to digital TV, game desktop computers, adapters, electric tools and other AC/DC adapter applications.

At present, engineers can use plug and play EVM evaluation design, and can also use the volume only of similar products on the market 1/3, 30W/in3, 92% efficiency, 65W USB Type-C PD AC/DC adapter reference design fast start high voltage system design. Wu Weiqiang also pointed out that TI's active clamp flyback chipset is mainly aimed at a higher power new market, rather than a traditional 5W or 10W product. The UCC28780+UCC24612 chipset will use the mobile phone as a breakthrough point and will expand into a wider application market in the future.