High-Power Switch Mode Power Supplies (SMPS): Applications & Design
Designing high-power switch mode power supplies (SMPS) requires careful selection of topology and close attention to factors like component choices and cooling system design. These power supplies can deliver outputs ranging from less than 1W to several kilowatts. In addition to design considerations, engineers must navigate evolving energy efficiency standards and comply with various regulations.
Overview of High-Power SMPS Markets and Applications
High-output power supplies are essential for a wide range of applications across the medical, industrial, transportation, and automotive sectors.
In medical applications, power supplies must meet exceptionally high standards for safety, electromagnetic compatibility (EMC), and reliability due to the highly risk-averse nature of the field. Medical-grade power supplies and medical equipment are designed to comply with IEC60601-1 safety standards and IEC60601-1-2 EMC standards, which directly influence their internal design. Medical equipment often requires longer development cycles, extensive vendor support, and a longer operational lifespan compared to commercial-grade devices. As a result, these power supplies need sustained vendor support over many years.
High-power medical applications include:
The industrial sector is another major area for high-power applications. Industrial DC/DC and AC/DC power supplies are integral to modern automated factories.
Common examples include:
In medical applications, power supplies must meet exceptionally high standards for safety, electromagnetic compatibility (EMC), and reliability due to the highly risk-averse nature of the field. Medical-grade power supplies and medical equipment are designed to comply with IEC60601-1 safety standards and IEC60601-1-2 EMC standards, which directly influence their internal design. Medical equipment often requires longer development cycles, extensive vendor support, and a longer operational lifespan compared to commercial-grade devices. As a result, these power supplies need sustained vendor support over many years.
High-power medical applications include:
- Surgical tables
- Motorized hospital beds
- Diagnostic or biological facilities
- Test or measurement systems
- Portable hemodialysis machines
- Respiratory equipment (ventilators, CPAP machines, and so on)
- MRI, CT, and PET scanners
- Laser equipment
The industrial sector is another major area for high-power applications. Industrial DC/DC and AC/DC power supplies are integral to modern automated factories.
Common examples include:
- Industrial automation and control systems
- Lathes and other industrial machinery
- Material handling equipment
- Welders
- Electric heaters and ovens
- Industrial robots
- Test and measurement equipment
Industrial grade power supplies must operate reliably across a wide range of temperatures, humidity levels, and shock/vibration conditions while handling short circuits and input voltage surges. Many are equipped with high-speed data and control bus interfaces, enabling seamless integration into Supervisory Control and Data Acquisition (SCADA) systems. These isolated DC/DC power supplies ensure fault-tolerant operations, mitigate ground loops, isolate subsystems, and enhance operator safety.
Railway Applications
DC/DC and AC/DC power supplies for railway applications must deliver reliable performance over extended lifetimes, even under extreme conditions such as high temperatures, freezing cold, shock, and vibration. Compliance with the EN50155 standard is critical for railway engineering and rolling stock. This standard defines stringent requirements for input voltage range, electrical isolation, operating temperature, shock and vibration tolerance, humidity resistance, EMC performance, reliability, and expected lifespan.Key railway applications include:
- Railway rolling stock
- On-board and trackside systems
- High-voltage battery-powered systems
- Distributed power supply architectures
Electrical Vehicle (EV) Applications
The rapid adoption of electric vehicles (EV) is driving a surge in demand for advanced power supplies to support EV charging infrastructure. Consumers increasingly expect larger battery capacities with faster charging times, prompting a shift toward higher battery operating voltages, from 400V to 800V. This evolution is creating new opportunities and challenges for high-power charging solutions.
Fig. 2: A typical EV home charging system
High-power EV chargers vary significantly in design based on their installation location and end-user needs. Charging power can range from under 2kW for small applications, such as electric scooters, to as much as 1MW for large fleet and utility vehicle charging. Most EV chargers are unidirectional, as the onboard charger (OBC) in vehicles is typically not designed for bidirectional power transfer. However, EVs equipped with a DC charging socket that directly accesses the high-voltage battery can function as energy storage systems (ESS). This capability enables various applications, including:
- Vehicle-to-home (V2H) power generation
- Vehicle-to-grid (V2G) peak shaving
- Vehicle-to-vehicle (V2V) charging or jump-starting another EV
While the EV charging ecosystem is expected to transition to bidirectional topologies, significant regulatory and technical challenges must be resolved before widespread adoption is feasible.
Auxiliary Power Requirements
AC/DC auxiliary supplies must meet the efficiency and performance demands of EV chargers. These systems are often deployed in overvoltage category III (OVC III) environments, where they must withstand dips, surges, and transients, such as those caused by lightning strikes. Environmental factors can also pose challenges, as chargers are frequently installed in harsh conditions, including damp, dusty, or dirty garages. Additionally, available AC supply voltages may vary, with options such as three-phase 480VAC or 277VAC. To ensure reliability, auxiliary AC/DC modules and internal switching regulators or DC/DC converters must provide robust voltage conversion and isolation, even in these demanding settings.
Design Considerations for High-Power SMPS Applications
Switch-mode power supplies (SMPS) are overwhelmingly preferred over linear designs for high-power applications due to their superior efficiency and power density. Various DC/DC converter topologies offer different combinations of performance and cost. While low-power applications often favor simple and cost-effective designs like flyback or forward topologies, high-power applications prioritize efficiency and performance—metrics that typically increase both cost and complexity. Four topologies are widely used in high-power DC/DC converter designs: the half-bridge, full-bridge, two-transistor push-pull, and resonant LLC converters.
Half-bridge and full-bridge converters
The half-bridge topology is scalable for higher power levels and is based on the forward converter design. Although it uses fewer components and is cost-effective for 230V AC and power factor correction (PFC) applications, it has limitations. A dead-time is required between switch cycles to prevent shoot-through currents, which reduces the duty cycle to approximately 45%. Additionally, the transformer in this design is larger, as it only sees half the input voltage per cycle.
Full-bridge converters overcome the limitations of half-bridge designs by using four switches to allow the transformer primary to see the full input voltage on each cycle. While the timing circuit is more complex and requires two isolated high-side drivers, this design achieves a nearly 50% duty cycle, improving efficiency and reducing switching losses. The added component cost is relatively minor in high-power applications.
Fig. 3: The half-bridge and full-bridge topologies
Full-bridge converters overcome the limitations of half-bridge designs by using four switches to allow the transformer primary to see the full input voltage on each cycle. While the timing circuit is more complex and requires two isolated high-side drivers, this design achieves a nearly 50% duty cycle, improving efficiency and reducing switching losses. The added component cost is relatively minor in high-power applications.
Fig. 3: The half-bridge and full-bridge topologies
Resonant LLC converters
Resonant LLC converters are popular for high-power applications due to their ability to achieve high efficiency, often in the upper 90% range. This topology minimizes switching losses through zero-voltage switching (ZVS), even under no-load conditions. It is particularly well-suited for applications with wide input voltage ranges, such as EV high-speed chargers, where efficiency and performance are critical. However, its increased complexity and cost can be disadvantages.
Fig. 4: The half-bridge LLC converter
Bidirectional EV charging requires a different approach. While a unidirectional onboard charger (OBC) typically uses an LLC resonant converter, this design is limited to unidirectional operation. For bi-directional charging, a CLLC resonant converter is preferred for the DC-DC stage. This topology offers high efficiency and a wide output voltage range, enabling both charging and discharging modes, making it ideal for advanced EV applications. The choice of topology depends on the specific performance and cost requirements of the application. RECOM’s AC/DC and DC/DC Books of Knowledge provide detailed insights into these topologies and their best-use cases.
Fig. 4: The half-bridge LLC converter
Bidirectional EV charging requires a different approach. While a unidirectional onboard charger (OBC) typically uses an LLC resonant converter, this design is limited to unidirectional operation. For bi-directional charging, a CLLC resonant converter is preferred for the DC-DC stage. This topology offers high efficiency and a wide output voltage range, enabling both charging and discharging modes, making it ideal for advanced EV applications. The choice of topology depends on the specific performance and cost requirements of the application. RECOM’s AC/DC and DC/DC Books of Knowledge provide detailed insights into these topologies and their best-use cases.
High-power design considerations for AC/DC converters
Low-power AC/DC designs can often rely on a simple diode bridge rectifier. However, high-power designs require a power factor correction (PFC) input stage to meet electromagnetic compatibility (EMC) regulations. The PFC stage can be integrated with the DC/DC stage as a single unit or implemented as a standalone front end in a modular design.
Three-Phase Vienna Rectifier Topology
For higher-power AC/DC converters, a three-phase PFC topology, like the Vienna rectifier (Figure 5), offers significant advantages. This active three-level topology reduces high switching voltage stress on transistors by employing a capacitive divider to halve the supply voltage. Efficiency can be further enhanced by partially or fully replacing the input diodes with synchronized switching transistors. For more information on AC/DC converter design, refer to RECOM’s previously mentioned AC/DC and DC/DC Books of Knowledge.
Fig. 5: Three-phase Vienna Rectifier topology PFC
Fig. 5: Three-phase Vienna Rectifier topology PFC
Cooling System Design
Operating temperature is a critical consideration in power supply design, whether for AC/DC or DC/DC systems. Temperature has a significant impact on semiconductor reliability, with failure rates doubling for every 10°C increase. Therefore, managing and dissipating excess heat is, therefore, a top priority for designers. Despite the high efficiencies of modern high-power systems—often exceeding 90%—effective thermal management remains essential.
Cooling Techniques
The most common cooling methods for AC/DC and DC/DC power supplies include conduction, convection, forced air, and liquid cooling. Each approach offers unique advantages for managing temperature and improving system efficiency.- Conduction cooling: This method transfers heat through direct contact from a higher-temperature component to a cooler surface. Many DC/DC converters feature flat surfaces designed to attach directly to external heat sinks or cold plates, which dissipate heat efficiently.
- Convection cooling: Heat is removed using natural airflow (a low-density fluid) that surrounds and contacts the device. Convection cooling is effective if the ambient air temperature remains cooler than the device, within specified limits. Many power devices are rated for natural convection cooling under such conditions.
- Forced air cooling: Fans are used to circulate air over the power supply or within the enclosure. This technique allows for higher power density by enhancing heat dissipation. Power supplies requiring forced air cooling typically specify a minimum airflow to maintain rated power output.
- Liquid cooling: Liquid-cooled systems circulate fluids to dissipate heat. This approach enables higher power densities with minimal noise, as no fan is required. A key benefit of liquid cooling is the ability to target and cool specific hotspots without relying on bulky internal heat sinks.
Silicon Carbide: An Emerging Trend in High-Power Design
High-power systems prioritize efficiency over cost and complexity, driving many innovations in this segment. Wide bandgap semiconductors, particularly silicon carbide (SiC) and gallium nitride (GaN), are increasingly replacing traditional silicon-based devices like Si MOSFETs and IGBTs in these applications. Among these, SiC is the more mature technology and is widely adopted for its unique properties, including a high critical electric field, fast electron velocity, high thermal conductivity, and a melting point of 300°C. These characteristics help SiC devices achieve low on-state resistance (R(DS)on), resulting in reduced switching and conduction losses—ideal for high-current applications.
Advantages of Silicon Carbide in DC/DC Designs
In DC/DC converters, SiC devices operate at higher switching speeds, allowing for greater power density and smaller magnetic components. Their superior efficiency minimizes switching losses, and their high thermal tolerance simplifies thermal management, reducing development time and costs.Advantages of Silicon Carbide in AC/DC Designs
In AC/DC converters, SiC technology replaces traditional PFC boost topologies with the more efficient totem-pole PFC architecture. Eliminating the power-wasting diode bridge improves efficiency by enabling higher switching frequencies and reducing the conduction path to just two semiconductor devices. While the totem-pole PFC was historically limited to discontinuous-mode operation (DCM) in low-power designs due to the body diode limitations of Si MOSFETs, SiC MOSFETs enable continuous conduction mode (CCM) operation. This advancement delivers higher efficiency, lower EMI, and increased power density.SiC MOSFETs vs. IGBTs: A Comparison
SiC MOSFETs also offer significant advantages over IGBTs. While IGBTs require ultrafast freewheeling diodes due to their lack of body diodes, their maximum switching frequency is limited to approximately 20kHz. This limitation results in larger and heavier magnetic and passive components compared to SiC-based designs. SiC devices, by contrast, achieve higher switching frequencies and better overall efficiency, making them a superior choice for high-power applications.RECOM Standard High-Power Product Families
RECOM offers a broad range of high-power products tailored to the diverse markets discussed earlier. These solutions address the specific needs of medical, industrial, railway, and EV applications.
Medical Applications
RECOM’s modular REM and RACM series converters deliver complete, compliant solutions that accelerate design timelines, simplify certification processes, and shorten time to market. These medical-grade DC/DC and AC/DC power supplies feature:
These features ensure compliance with the stringent ES/IEC/EN 60601-1 3rd Edition medical safety standard, offering an additional layer of protection beyond functional isolation.
- Reinforced isolation with two means of patient protection (2MOPP)
- Low leakage (BF and CF ratings)
- Creepage and clearance distances exceeding 8mm
These features ensure compliance with the stringent ES/IEC/EN 60601-1 3rd Edition medical safety standard, offering an additional layer of protection beyond functional isolation.
Industrial Applications
RECOM provides one of the most extensive portfolios of industrial-grade power supplies, featuring over 25,000 standard products. These cost-effective, safety-approved, and EMC-certified solutions cover power levels up to 10kW and offer isolation ratings from 1kVDC to 5kVAC. Available in various form factors, RECOM’s industrial power supplies are designed to meet the demands of diverse industrial environments.
Railway Applications
For railway systems, RECOM offers robust solutions that comply with railway standards. Notable offerings include:
Additionally, RECOM provides DC/DC and DC/AC power supplies for both on-board and trackside railway applications.
- Three-phase AC input battery chargers with active power factor correction (for example, RMOC3200 and RMOC5000 series), supporting cascaded configurations up to 20kW
- RMOC3200 series with DC input capability up to 800V
- Output options ranging from 24Vnom to 110Vnom (including intermediate values like 36, 48, 72, and 96Vnom)
Additionally, RECOM provides DC/DC and DC/AC power supplies for both on-board and trackside railway applications.
EV Charging Applications
RECOM’s EV portfolio includes a wide selection of isolated DC/DC converters for high-side gate drivers and OVCIII-rated auxiliary power AC/DC converters. RECOM Power Systems (RPS) extends these capabilities with full-custom solutions, such as:
All products are equipped with comprehensive protection, monitoring, and intelligent control interfaces to ensure reliable performance.
- Battery chargers, balancers, and conditioners for mobile and stationary applications
- Single- or three-phase input configurations with outputs customizable up to 20kW or higher
- Bidirectional designs for energy recovery applications
All products are equipped with comprehensive protection, monitoring, and intelligent control interfaces to ensure reliable performance.
RECOM Custom High-Power Design Capabilities
RPS specializes in customized high-power solutions, providing plug-and-play units tailored to a wide range of applications. Whether the input is high-voltage DC from a fuel cell or single/three-phase AC, RECOM Power Solutions deliver exceptional power density and efficiency. RECOM offers solutions across industries, including automation, medical engineering, transportation, and general industrial use, for both stationary and mobile installations. These designs are built to ensure:
- Top-tier functionality and reliability
- Extremely long service life
- Active PFCs for AC inputs and overvoltage protection for DC inputs
- The latest switching topologies and digital control features
Platform Solutions
RECOM develops platform-based designs to deliver excellent price-to-specification ratios and reduced time-to-market. These platforms can be quickly modified to meet unique customer needs, ensuring cost-effective and tailored solutions. Key platform features include:
- DC output options: 12, 24, 36, 48, 110, 500VDC, or custom voltages upon request
- High efficiency and compact form factors
- Cascadable power capabilities with n+1 redundancy
- Standard, modified standard, and fully customized design options
- Digital control and monitoring interfaces (for example, PM-Bus)
High-power PFC stages
RECOM also offers modular high-power PFC stages with ratings up to 4kW. These PFC front ends achieve power factors exceeding 0.95 and typical efficiencies of 92%, making them ideal for demanding applications.
Why Choose RECOM for a High-Power Application
RECOM offers a comprehensive range of high-power supplies designed to meet diverse AC/DC, DC/DC, and DC/AC requirements. These solutions include both standard products and fully customizable options to address specific application needs. The table below summarizes RECOM’s standard and customized high-power product capabilities.
RECOM’s extensive product line is tailored to meet the needs of a wide range of market segments and applications. For more information, explore our standard product offerings, or download resources such as whitepapers, reference designs, application notes, reports, and safety standards documentation.
If you’re considering a custom project, contact our engineering team for a tailored solution designed to meet your unique requirements.
| Attribute | Specifications |
|---|---|
| Power (W) | Up to 50,000W (modules cascadable up to 20,000W) |
| Isolation | Isolated or non isolated |
| Number of outputs | Single or multible outputs |
| Input voltage (Vin) | 20–264V (1AC), 200–600V (3AC), 200–2500V (DC) |
| Output voltage (Vout) | Low voltage or >1kV |
| Isolation voltage | Up to 6kV |
| Connection | Screw terminals, cage clamps, and custom options on request |
| Mechanical style | Open frame, chassis mounting, enclosed, or 19" rack style |
| Certifications | CE, EN 55024, EN 55032, EN 62368, UL 60950-1, EN 50155 |
| Operating temperature | Min: -40°C/-50°C, Max: 70°C/85°C |
| Protections | Overcurrent protection (OCP), overtemperature protection (OTP), overvoltage protection (OVP), short-circuit protection (SCP) |
| Output adjustment | Adjustable trim pin for output voltage |
| Interfaces | I²C, Ethernet, CAN, and more |
| Directives | REACH, RoHS 2+ (10/10), WEEE |
| Warranty | 3 years |
| Regulation | Regulated |
RECOM’s extensive product line is tailored to meet the needs of a wide range of market segments and applications. For more information, explore our standard product offerings, or download resources such as whitepapers, reference designs, application notes, reports, and safety standards documentation.
If you’re considering a custom project, contact our engineering team for a tailored solution designed to meet your unique requirements.