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Switching Regulator Packages Are Getting Smaller

【Introduction】Switching regulator circuits have existed for many years, and users can choose to design their own products using discrete components, or they can buy modular finished products. Today, technologies that can meet the latest efficiency, EMI and power density requirements are making modular solutions more attractive.

Whether used directly in the load or as part of a distributed power architecture, non-isolated switching regulators have long been the workhorse for efficiently converting DC power rails to lower or higher voltages. The first designs in the 1950s used vacuum tubes, which significantly improved conversion efficiency compared to alternative “linear regulators”, while also opening up the possibility of boosting DC voltages previously only possible with bulky mechanical vibrators. accomplish. It was not until the 1970s that the first switching power supply IC control chip Silicon General SG1524 using “voltage mode” control appeared. Its success opens new doors for alternative options using different control and conversion technologies. With decades of development, although bipolar transistors and Diodes are still widely used, it has become a trend to be replaced by MOSFETs and MOSFET synchronous rectifiers in the future. Even the current Si-FETs are also affected by broadband such as SiC and GaN. Threat of interstitial materials.

Conversion efficiency is a criterion for measuring the development of switching regulators. This number has climbed steadily over the years, from 80% to 97%, with conversion efficiencies even higher than 97% in the latest designs. Higher efficiency means higher power density, measured in watts/cm3, which tells you how much power a given volume of components in a design can deliver. The power densities marked out in the data sheets are getting higher and higher, some of which are somewhat “creative”. For example, some IC regulators advertise data that do not take into account all necessary external components, especially bulky inductors and capacitors. Cooling is often an issue as well, with staggering power densities only achieved with nearly unrealistic air flow rates or overly complex water cooling. The ambient operating temperature range is also important, not only the heat sink temperature, but if the part must be significantly derated above a certain room temperature, this will directly reduce the useful power.

State-of-the-art switching regulator developments

The development of non-isolated switching regulators is also a history of continued improvements and developments in component integration in terms of efficiency and functionality. As the load requirement has dropped from 5V to 3.3V and then to below 1V now, the output voltage continues to decrease. As the input voltage increases, so does the system power, requiring higher bus voltages and lower current consumption. IC control chips simplify the design of discrete components, where the controller integrates switching transistors and magnetic components.Peripheral functions such as fault monitoring, current sharing, synchronization and sequencing are increasingly used in IC design

Suppliers have been selling fully packaged converter modules from the early days of switching regulator designs, helping customers save the effort and risk of designing in-house while providing an efficient solution. But sometimes it’s hard to promote because experienced engineers don’t want to pay high prices for products they can design themselves. For a product that has been sold for many years, even design timing issues and associated risks from in-house are tolerable, and years of sales are enough to cover several times the R&D costs. In addition, the sense of accomplishment brought by designing a switching power supply from scratch is also part of the reason.

Things are different now, original equipment manufacturers (OEMs) do not have expertise in power supply design, and the technology required to achieve optimal performance can be very specialized, even involving processes that the OEM may not be able to provide, such as ferrite Forming of body material. In addition to this, product life cycles have become shorter, which means that development costs and delays due to design optimization or repeated EMC testing have a greater impact on the return on investment (Figure 1).

Switching Regulator Packages Are Getting Smaller

Figure 1: Delayed product launch equals lost revenue

Of course, control IC manufacturers do provide various aspects of application information to make the design look easy, but these simplified design tools cannot predict actual circuit requirements. For example, the recommended output capacitance is often too low to handle real-life dynamic loads, which can swing by a million times between active and sleep states, producing unacceptable voltage jumps (Figure 2).

Switching Regulator Packages Are Getting Smaller

Figure 2: A load step in a buck converter causes voltage transients

Inductors in application notes are also often “whitewashed”, with suggested components for optimum performance regardless of price or availability. In fact, choosing the best Inductor can take weeks to evaluate performance over temperature, frequency, and load current (static and dynamic). Other parameters, such as the saturation characteristics of the inductor and the leakage field can be very important in the design. The EMC performance of a complete design is a “big unknown” that is not known until the final PCB is routed and the final components are selected, at which point changes can be expensive. A similar situation occurs with capacitors, where important information to evaluate (such as self-inductance) is often not available from the data sheet, so it can be difficult to select the best part among the intricate relationship between performance and cost.

Currently, state-of-the-art switching regulator designs achieve high power density through control ICs, which are typically BGA packages measuring only 2mm x 2mm with a pad matrix pitch of only 0.4mm. This may not be suitable for the user’s PCB assembly process as precise tin printing and expensive X-ray imaging are required to check for shorts or bad solder joints. Likewise, a converter control IC may require a complex multilayer PCB with filled and buried vias to the ground plane to efficiently dissipate heat from the package to the board. Even if the user does not need to use this complex PCB in other circuits, they still need to pay for the PCB manufacturing cost.

The latest switching regulators are versatile

Some will argue that power modules must be generic and not the best solution for an application, and RECOM’s latest generation is capable of high performance under a wide range of operating conditions. Such as RECOM’s 0.5A RPMH series, the input voltage range is up to 65V, and the output voltage range is adjustable from 2.5V to 28V. These features are all packed into an EMI-shielded 12.19mm x 12.19mm x 3.75mm package and can operate at temperatures up to 105°C without forced air cooling (Figure 3). The RPMB series with the same package and higher output current of 3A can operate at input voltages up to 36V with an adjustable output range of 1V to 24V. The same type of RPM series with 6A output current has a lower maximum input voltage and uses the same package size.

Switching Regulator Packages Are Getting Smaller

Figure 3: 6A switching regulator (RECOM RPM series) in 12.19mm x 12.19mm x 3.75mm package

Since these modules are highly integrated, adding a range of control and monitoring functions such as on/off control, remote sensing, remote feedback, soft-start, power good signaling and power-up sequencing does not add much to the manufacturing cost. These modules feature general fault protection against input undervoltage, short circuit, overcurrent, and overheating. Applications can run from almost zero current to the rated maximum under various sleep or full load conditions, so modules typically employ phase-cutting techniques such as multiphase converter topologies to minimize light load power consumption and Improve efficiency.

RECOM’s power modules will use advanced production techniques to achieve the highest power density, such as leadframe flip-chip technology with overmolding. The RECOM RPX series (Figure 4), for example, is available in a 4.5mm x 4mm x 2mm QFN package and is rated at 2.5A, while some parts do not require forced air cooling and are rated to operate up to 95°C at full load. In the case of the RPX series, this part requires an external capacitor for maximum performance. This can actually help improve the overall power density, for example, the power supply may already have input capacitance, so the output capacitance can be chosen to achieve the desired voltage rating. If the capacitor is internal, the size must be increased and the voltage rating is the maximum voltage after trimming.

Switching Regulator Packages Are Getting Smaller

Figure 4: 2.5A Switching Regulator in 4.5 x 4 x 2mm QFN Package (RECOM RPX Series)

On-board regulators often need to be both step-up and step-down. Generally used in battery-powered devices, it is necessary to maintain power for as long as possible when the battery is discharged. To get a positive output voltage from a positive input, the traditional solution is to use a SEPIC, ZETA or Cuk converter, all of which require two magnetic components and complex control loops. As integration increases, modular converters enable different topologies at low cost, such as a four-switch buck-boost, which is in fact a set of MOSFETs that can be configured “on the fly” as switches or diodes, between buck and Switch seamlessly between boost modes. Take the RECOM RBB series as an example, it is packaged in an LGA with a current rating of 3A, a 3kW module in a half-brick package with an input of 9V to 60V and an output voltage of 0V to 60V. Usually used in 48V to 24V or 12V to 24V battery power conversion, electric vehicles, battery voltage regulators or laboratory high-power DC power supplies.

It’s obvious whether you want modules or “DIY”

Purchasing a switching regulator module that combines all process and design techniques to achieve optimum performance not only reduces product development risk but also saves users valuable time and money. Sourcing, warehousing, and handling one component will be more cost-effective in terms of supplier and inventory management compared to suppliers facing different components, and can even include custom magnetic components if optimum performance is required. This can also save SMD placement and testing time; for some necessary cases, it can also save the time and cost of certification body approval. In addition, this solves the problem of replacement products, as more and more modules have functions and pinouts that conform to industry standards such as DOSA. When calculating the total cost, the modular solution from RECOM is sure to win: you don’t have to do it anymore, because we’ve done it for you!

Source: RECOM

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