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.
Figure 2: A typical EV home charging system (Source: RECOM)
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.
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.
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
Figure 3: The half-bridge and full-bridge topologies (Source: RECOM)
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.
Resonant LLC converter
Figure 4: the half-bridge LLC converter (Source: RECOM)
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.
The topology has two resonant frequencies. The first is the series resonance tank formed from CR and LR and the second the parallel resonance tank formed by CR and LM + LR. The advantage of the double resonances is that one or the other takes precedence according to load. So, while a series resonant circuit has a frequency that increases with reduced load and a parallel resonant circuit has a frequency that increases with increasing load, a well-designed series parallel resonant circuit has a stable frequency over the whole load range. The switching frequency and values of LR and CR are chosen so that the transformer primary winding is in continuous resonance and sees an almost perfect sinusoidal waveform.
The resonant LLC has the advantage over both push-pull and half-bridge topologies of being suitable for a wide range of input voltages. The downside to the resonant LLC topology is its increased complexity and cost.
Bi-directional EV charging requires a different approach. A unidirectional OBC is typically an LLC resonant converter but this is a unidirectional topology. A bi-directional CLLC resonant converter is therefore preferred for the DC-DC stage, as it combines high efficiency with a wide output voltage range in both charging and discharging modes.
High-power design considerations for AC/DC converters
Low-power designs can make do with a simple diode bridge rectifier, but a higher-power AC/DC designs must use a power factor correction (PFC) input stage to comply with EMC regulations. The PFC can either combined with the DC/DC stage into a single unit or added as a standalone front end in a modular design.
Fig. 5: Three-phase Vienna Rectifier topology PFC (source: RECOM)
For higher power AC/DC converters, a three-phase PFC topology such as the Vienna rectifier (Figure 5) can be used. This is an active three-level topology that reduces high switching voltage stress on the transistors by using a capacitive divider to halve the supply voltage. The input diodes can be either partly or fully replaced with synchronized switching transistors to increase the efficiency further.
RECOM’s AC/DC Book Of Knowledge, mentioned earlier, covers AC/DC converter design in greater detail.
Fig. 5: Three-phase Vienna Rectifier topology PFC (source: RECOM)
For higher power AC/DC converters, a three-phase PFC topology such as the Vienna rectifier (Figure 5) can be used. This is an active three-level topology that reduces high switching voltage stress on the transistors by using a capacitive divider to halve the supply voltage. The input diodes can be either partly or fully replaced with synchronized switching transistors to increase the efficiency further.
RECOM’s AC/DC Book Of Knowledge, mentioned earlier, covers AC/DC converter design in greater detail.
Cooling system design
Another design consideration is the operating temperature of the power supply, whether AC/DC or DC/DC. There is a well-established relationship between operating temperature and reliability for semiconductor components. Higher temperatures equate to higher failure rates, with a statistical halving of the reliability for every 10°C increase in temperature. Managing and dissipating excess heat is thus an important priority for the power supply designer. Even though high-power designs typically boast efficiencies well in excess of 90%, thermal management is still required.
The most common cooling techniques for AC/DC and DC/DC power supplies include conduction, convection, air, and liquid cooling techniques. Each of these cooling techniques can provide a temperature management solution that increases the effectiveness and efficiency of the application.
Conduction cooling is the transfer of heat from a higher-temperature part to a lower-temperature part by direct contact. For example, many DC/DC converters have a flat surface that is designed to mount directly to an external heat sink or cold plate that will conduct the heat away from the power device by direct contact, thereby cooling it.
Convection cooling transfers heat from the power device by the action of the natural air flow (a low-density fluid) surrounding and contacting the device. Many power devices are rated for natural convection cooling so long as the air surrounding the unit remains within a limited temperature range that is cooler than the device.
Fans can also be mounted on the front or rear of either the power supply or the surrounding cabinet to supply forced air cooling. This method allows for greater power density. Many power supplies that require forced air cooling will specify a minimum airflow to achieve rated power.
Liquid cooled power supplies use circulating fluids to cool down the system resulting in higher power capabilities with little noise as there is no cooling fan. The advantage of liquid cooling is that hot spots can be targeted and individually cooled without the need for bulky internal heat sinks.
The most common cooling techniques for AC/DC and DC/DC power supplies include conduction, convection, air, and liquid cooling techniques. Each of these cooling techniques can provide a temperature management solution that increases the effectiveness and efficiency of the application.
Conduction cooling is the transfer of heat from a higher-temperature part to a lower-temperature part by direct contact. For example, many DC/DC converters have a flat surface that is designed to mount directly to an external heat sink or cold plate that will conduct the heat away from the power device by direct contact, thereby cooling it.
Convection cooling transfers heat from the power device by the action of the natural air flow (a low-density fluid) surrounding and contacting the device. Many power devices are rated for natural convection cooling so long as the air surrounding the unit remains within a limited temperature range that is cooler than the device.
Fans can also be mounted on the front or rear of either the power supply or the surrounding cabinet to supply forced air cooling. This method allows for greater power density. Many power supplies that require forced air cooling will specify a minimum airflow to achieve rated power.
Liquid cooled power supplies use circulating fluids to cool down the system resulting in higher power capabilities with little noise as there is no cooling fan. The advantage of liquid cooling is that hot spots can be targeted and individually cooled without the need for bulky internal heat sinks.
Silicon carbide: an emerging trend in high-power design
High power designs value high efficiency over component cost or design complexity compared to their low-power counterparts so many innovations appear first in the high-power segment.
For example, a high-power design has traditionally used Si MOSFETS or Si IGBTs for the power switching function, but wide bandgap devices based on silicon carbide (SiC) and gallium nitride (GaN) are beginning to replace silicon devices in this application. SiC is the more mature technology and is being adopted in high-power systems due to its unique combination of critical electric field, electron velocity, high melting point (300°C), and high thermal conductivity. On the transistor level, this leads to a low on-state resistance (R(DS)on) that allows for low switching loss and low conduction losses, making it ideal for high-current applications.
In a DC/DC design, the faster switching speed of the SiC devices leads to greater power density through the use of much smaller magnetics and much greater efficiency due to lower switching losses. The higher operating temperature of SiC also reduces the development time and cost associated with thermal management design.
In an AC/DC design, the use of SiC allows the replacement of the conventional PFC boost topology, with its power-wasting diode bridge, by the more-efficient totem-pole PFC. Eliminating the bridge rectifiers improves PFC efficiency by switching at a higher frequency and reducing the number of semiconductor devices in the conduction path from three to two.
The theoretical advantages of the totem-pole PFC architecture have been recognized for many years, but a high-power implementation was previously impractical as the body diode of the Si MOSFETs limits totem-pole application to discontinuous-mode operation (DCM) and low power levels. In contrast, the SiC MOSFET allows the totem pole PFC to operate in CCM for high efficiency, low EMI, and increased power density.
A SiC MOSFET also has advantages over an IGBT. The IGBT does not contain a body diode so an ultrafast freewheeling diode may be used instead. But the IGBT’s maximum switching frequency is limited to around 20kHz due to high switching and conduction losses. The low maximum switching frequency increases the weight and size of the magnetics and passive components compared to a SiC solution.
For example, a high-power design has traditionally used Si MOSFETS or Si IGBTs for the power switching function, but wide bandgap devices based on silicon carbide (SiC) and gallium nitride (GaN) are beginning to replace silicon devices in this application. SiC is the more mature technology and is being adopted in high-power systems due to its unique combination of critical electric field, electron velocity, high melting point (300°C), and high thermal conductivity. On the transistor level, this leads to a low on-state resistance (R(DS)on) that allows for low switching loss and low conduction losses, making it ideal for high-current applications.
In a DC/DC design, the faster switching speed of the SiC devices leads to greater power density through the use of much smaller magnetics and much greater efficiency due to lower switching losses. The higher operating temperature of SiC also reduces the development time and cost associated with thermal management design.
In an AC/DC design, the use of SiC allows the replacement of the conventional PFC boost topology, with its power-wasting diode bridge, by the more-efficient totem-pole PFC. Eliminating the bridge rectifiers improves PFC efficiency by switching at a higher frequency and reducing the number of semiconductor devices in the conduction path from three to two.
The theoretical advantages of the totem-pole PFC architecture have been recognized for many years, but a high-power implementation was previously impractical as the body diode of the Si MOSFETs limits totem-pole application to discontinuous-mode operation (DCM) and low power levels. In contrast, the SiC MOSFET allows the totem pole PFC to operate in CCM for high efficiency, low EMI, and increased power density.
A SiC MOSFET also has advantages over an IGBT. The IGBT does not contain a body diode so an ultrafast freewheeling diode may be used instead. But the IGBT’s maximum switching frequency is limited to around 20kHz due to high switching and conduction losses. The low maximum switching frequency increases the weight and size of the magnetics and passive components compared to a SiC solution.
RECOM standard high-power product families
RECOM offers many families of high-power standard products that are optimized for the markets discusses earlier.
For medical applications, RECOM’s modular REM and RACM series converters offer complete, compliant solutions that reduce design time, simplify end-user certification and provide faster time to market. These medical grade DC/DC converters and AC/DC power supply series feature reinforced isolation with two means of patient protection (2 x MOPP), low leakage (BF and CF ratings) and > 8mm creepage and clearance distances. Reinforced isolation provides an additional level of safety beyond the standard functional isolation to comply with the medical safety standard ES/IEC/EN 60601-1 3rd Ed.
For industrial power supplies, RECOM offers the most comprehensive industrial portfolio available, with over 25,000 standard products. RECOM industrial-grade power supplies are cost-effective, safety-approved, and EMC-certified power supplies in many form factors with power levels up to 10kW and isolation from 1kVDC up to 5kVAC.
For railway use, RECOM and its subsidiary RECOM Power Systems (RPS) offer three-phase AC input battery chargers with active power factor correction, complying with railway standards, available with ratings at 3.2kW (RMOC3200 series) and 5kW (RMOC5000 series) which can be cascaded up to 20kW. The RMOC3200 series also operates with DC inputs up to 800V. Outputs from both series are available suitable for 24Vnom up to 110Vnom (and all in between 36/48/72/96). RECOM also offers DC/DC and DC/AC railway power supplies for both on-board and trackside applications.
For EV charging, RECOM offers a wide range of isolated DC/DC converters suitable for powering the high-side gate drivers as well as OVCIII-rated auxiliary power AC/DC converters. RPS offers full-custom solutions that include battery chargers, balancers and conditioners for mobile and stationary applications. The inputs can be single- or three-phase, and the outputs can be customer-specified to 20kW or more. Bidirectional designs are available for energy recovery applications. All products provide full protection, monitoring, and control through intelligent interfaces.
For medical applications, RECOM’s modular REM and RACM series converters offer complete, compliant solutions that reduce design time, simplify end-user certification and provide faster time to market. These medical grade DC/DC converters and AC/DC power supply series feature reinforced isolation with two means of patient protection (2 x MOPP), low leakage (BF and CF ratings) and > 8mm creepage and clearance distances. Reinforced isolation provides an additional level of safety beyond the standard functional isolation to comply with the medical safety standard ES/IEC/EN 60601-1 3rd Ed.
For industrial power supplies, RECOM offers the most comprehensive industrial portfolio available, with over 25,000 standard products. RECOM industrial-grade power supplies are cost-effective, safety-approved, and EMC-certified power supplies in many form factors with power levels up to 10kW and isolation from 1kVDC up to 5kVAC.
For railway use, RECOM and its subsidiary RECOM Power Systems (RPS) offer three-phase AC input battery chargers with active power factor correction, complying with railway standards, available with ratings at 3.2kW (RMOC3200 series) and 5kW (RMOC5000 series) which can be cascaded up to 20kW. The RMOC3200 series also operates with DC inputs up to 800V. Outputs from both series are available suitable for 24Vnom up to 110Vnom (and all in between 36/48/72/96). RECOM also offers DC/DC and DC/AC railway power supplies for both on-board and trackside applications.
For EV charging, RECOM offers a wide range of isolated DC/DC converters suitable for powering the high-side gate drivers as well as OVCIII-rated auxiliary power AC/DC converters. RPS offers full-custom solutions that include battery chargers, balancers and conditioners for mobile and stationary applications. The inputs can be single- or three-phase, and the outputs can be customer-specified to 20kW or more. Bidirectional designs are available for energy recovery applications. All products provide full protection, monitoring, and control through intelligent interfaces.
RECOM custom high-power design capabilities
RPS specializes in customized solutions and has an ideal solution for any application requiring high-power plug & play units. Whether the input is high voltage DC from a fuel-cell or single/three phase AC, RECOM Power Solutions ensure high power density and excellent efficiency.
RECOM supplies solutions for industry, automation, medical engineering, and transportation for stationary or mobile installation depending on application. These solutions ensure top functionality, reliability, and extremely long life with active PFCs on AC lines or overvoltage-protected DC inputs on DC lines as well as the latest switching topologies and concepts with digital control. Platform designs make excellent price/specification ratios possible as well as lower time-to-market with modified standard solutions.
Consult this page to see high-power designs that have been developed as platform solutions. RECOM can quickly modify these solutions to satisfy unique customer needs in a quick and cost-effective manner. Platform features include:
RPS also offers modular high-power PFC stages with ratings up to 4kW. These PFC front ends can achieve power factors of more than 0.95 with typical efficiency of 92%.
RECOM supplies solutions for industry, automation, medical engineering, and transportation for stationary or mobile installation depending on application. These solutions ensure top functionality, reliability, and extremely long life with active PFCs on AC lines or overvoltage-protected DC inputs on DC lines as well as the latest switching topologies and concepts with digital control. Platform designs make excellent price/specification ratios possible as well as lower time-to-market with modified standard solutions.
Consult this page to see high-power designs that have been developed as platform solutions. RECOM can quickly modify these solutions to satisfy unique customer needs in a quick and cost-effective manner. Platform features include:
- DC output: 12, 24, 36 , 48, 110, 500 VDC or other voltages on request
- Excellent efficiency and compact design
- Cascadable power and n+1 redundancy
- Standard, modified standard and full custom design solutions
- Digital interfaces for control and monitoring (e.g., PM-Bus)
RPS also offers modular high-power PFC stages with ratings up to 4kW. These PFC front ends can achieve power factors of more than 0.95 with typical efficiency of 92%.
Why choose RECOM for a high-power application
RECOM offers an extensive range of high-power supplies that satisfy AC/DC, DC/DC, and DC/AC requirements. The table below summarizes our standard and customized high-power product capabilities.
For more information on high-power designs, browse our large selection of standard products that cover a large number of market segments and applications. Or download one of our technical resources: whitepapers, reference designs, application notes, reports, or selection of applicable safety standards.
If you’re considering a custom project design, to find out how we can help.
| Attributes | High Power solutions for DC or AC line |
|---|---|
| AC/DC or DC/DC | Available Features / Options: |
| Power (W) | up to 50000W Modules, cascadable up to 20000W |
| Isolation | Isolated or non isolated |
| Nr. of Outputs | Single or multible outputs |
| Vin (V) | 20 - 264 1AC 200 - 600 3AC 200 - 2500VDC |
| Vout (V) | low voltage or >1kV |
| Isolation (kV) | up to 6kV |
| Connection | Screw Terminals, Cage Clamps others on request |
| Mechanical style | Open frame Chassis mounting, enclosed 19"-Rack style |
| Certifications | CE, EN 55024, EN 55032, EN 62368, UL 60950-1, EN 50155 |
| MIN Operating Temp (°C) | -40.0 / -50.0 |
| MAX Operating Temp (°C) | 70.0 / 85.0 |
| Protections | OCP, OTP, OVP, SCP |
| Trim Pin Output Voltage Adjustment | ADJUSTABLE |
| Interfaces | I²C, Ethernet, CAN, ….? |
| Directives | REACH, RoHS 2+ (10/10), WEEE |
| Warranty | 3 Years |
| Regulation | Regulated |
For more information on high-power designs, browse our large selection of standard products that cover a large number of market segments and applications. Or download one of our technical resources: whitepapers, reference designs, application notes, reports, or selection of applicable safety standards.
If you’re considering a custom project design, to find out how we can help.