AC/DC & DC/DC Converters: Standard Power Solutions and Applications
Designers of power supplies understand that using high-quality AC/DC power supplies, DC/DC converters, and switching regulators in their design architectures leads to a high-reliability end product that users will appreciate. There are numerous design requirements for compact power supplies in a wide variety of applications, including medical, test & measurement, industrial, mobility, automation, Internet of Things (IoT), and high power density, among others.
Electronic devices plugged into an outlet require a high-quality AC/DC converter to convert the AC power input into DC power output. For most designs, semiconductor devices operate on DC power. DC/DC converters are typically selected to power designs with a regulated and stable voltage, especially when the input source is fluctuating. This type of power converter is designed with high-frequency switching circuits, coupled with inductors, switches, and capacitors that help reduce the switching noise in the system. The result is a solid and stable regulated DC voltage output.
Electronic devices plugged into an outlet require a high-quality AC/DC converter to convert the AC power input into DC power output. For most designs, semiconductor devices operate on DC power. DC/DC converters are typically selected to power designs with a regulated and stable voltage, especially when the input source is fluctuating. This type of power converter is designed with high-frequency switching circuits, coupled with inductors, switches, and capacitors that help reduce the switching noise in the system. The result is a solid and stable regulated DC voltage output.
DC/DC Converters: A Basic Overview
DC/DC converters come in various types, each designed to address specific voltage regulation needs in electronic systems. Let’s explore the different types of DC/DC converters, examining their key functions and features.
The Buck Converter
The step-down (buck) converter can convert a higher DC input voltage into a stabilized, but lower, DC voltage at its output. See Figure 1.
Fig. 1: An example of a simple DC/DC Buck Converter Voltage Regulator (Image from Reference 1)
The advantage of buck converters is that losses are low, enabling efficiencies of over 97%. The switching frequencies range into the hundreds of kHz. A good power density architecture is achieved using smaller inductors along with a fast transient response capability. During its switching cycle, when the FET switch is disabled, the output level drops to zero. This enables very low no-load power consumption. Taken together, these advantages make the buck regulator an attractive replacement for a linear voltage regulator in a variety of applications.
Buck converters do come with a disadvantage: The Pulse Width Modulation (PWM) regulator feedback circuit needs to have a minimum output ripple to reach proper regulation. This is because the regulation occurs cycle by cycle. In addition, the output ripple depends on the duty cycle, which is a maximum at 50%. In this case, it would not be possible to achieve ripple and noise down to μV levels; this can only be achieved by using linear regulators that are non-switching.
If a designer requires a cleaner power supply, a linear regulator can be placed after a buck regulator, to achieve the best performance of both topologies. This is made possible because the linear regulator Power Supply Rejection Ratio (PSRR) greatly reduces ripple/noise at its output.
Fig. 1: An example of a simple DC/DC Buck Converter Voltage Regulator (Image from Reference 1)
The advantage of buck converters is that losses are low, enabling efficiencies of over 97%. The switching frequencies range into the hundreds of kHz. A good power density architecture is achieved using smaller inductors along with a fast transient response capability. During its switching cycle, when the FET switch is disabled, the output level drops to zero. This enables very low no-load power consumption. Taken together, these advantages make the buck regulator an attractive replacement for a linear voltage regulator in a variety of applications.
Buck converters do come with a disadvantage: The Pulse Width Modulation (PWM) regulator feedback circuit needs to have a minimum output ripple to reach proper regulation. This is because the regulation occurs cycle by cycle. In addition, the output ripple depends on the duty cycle, which is a maximum at 50%. In this case, it would not be possible to achieve ripple and noise down to μV levels; this can only be achieved by using linear regulators that are non-switching.
If a designer requires a cleaner power supply, a linear regulator can be placed after a buck regulator, to achieve the best performance of both topologies. This is made possible because the linear regulator Power Supply Rejection Ratio (PSRR) greatly reduces ripple/noise at its output.
The Boost Converter
A step-up, or boost, converter power design converts a lower input voltage into a stable and solid higher voltage at the output. Figure 2.
Figure 2: An example of a simple DC/DC boost converter regulator (Image from Reference 1)
The advantage of using a boost converter architecture is that the output voltage can be varied with the mark-space ratio (defined as the ratio between the high time and the low time, or the duty cycle). For example, a 50% duty cycle occurs when the voltage high time is equal to the voltage low time of the PWM signal in order to be equal to, or “boosted” above, the input voltage VIN.
This functionality allows the boost converter, for example, to boost a low battery voltage output to a more useful higher-voltage level. However, a boost ratio that is more than two or three times the input would make feedback stability more difficult to maintain at a solid level. In addition, because the input current pulses would increase proportionally, compared with the boost gain, a converter that triples its input voltage would draw three times its input current. This level of pulsed input current can even lead to increased EMI, and to voltage-drop levels at the battery input leads.
Another disadvantage of the boost converter is that its output cannot be switched off without adding a second switch, placed in series with the input. This is because disabling the PWM controller alone would not disconnect the load from the input. Power designers should not allow a boost converter’s input voltage to rise above its output voltage. In such a case, the PWM controller could then keep S1, in Figure 3, open continuously. The input and output would be connected directly from L1 and D1 without regulation. Highly damaging currents may flow that could quickly damage the converter along with its load. Designers who cannot avoid this condition must employ a replacement topology that permits both buck and boost operation.
Figure 2: An example of a simple DC/DC boost converter regulator (Image from Reference 1)
The advantage of using a boost converter architecture is that the output voltage can be varied with the mark-space ratio (defined as the ratio between the high time and the low time, or the duty cycle). For example, a 50% duty cycle occurs when the voltage high time is equal to the voltage low time of the PWM signal in order to be equal to, or “boosted” above, the input voltage VIN.
This functionality allows the boost converter, for example, to boost a low battery voltage output to a more useful higher-voltage level. However, a boost ratio that is more than two or three times the input would make feedback stability more difficult to maintain at a solid level. In addition, because the input current pulses would increase proportionally, compared with the boost gain, a converter that triples its input voltage would draw three times its input current. This level of pulsed input current can even lead to increased EMI, and to voltage-drop levels at the battery input leads.
Another disadvantage of the boost converter is that its output cannot be switched off without adding a second switch, placed in series with the input. This is because disabling the PWM controller alone would not disconnect the load from the input. Power designers should not allow a boost converter’s input voltage to rise above its output voltage. In such a case, the PWM controller could then keep S1, in Figure 3, open continuously. The input and output would be connected directly from L1 and D1 without regulation. Highly damaging currents may flow that could quickly damage the converter along with its load. Designers who cannot avoid this condition must employ a replacement topology that permits both buck and boost operation.
Buck-Boost (Inverting) Converter
The buck-boost converter (also known as flyback converter) can convert an input voltage to a regulated, negative output voltage, which can go higher or lower than the absolute value level of that input voltage. The image in Figure 3 shows a simplified schematic of the Buck/Boost converter.
Figure 3: A simplified schematic of a Buck/Boost regulator (Image from Reference 1)
The input voltage of a buck-boost converter may be higher or lower than the regulated output voltage. That capability is useful for applications that may require a stabilized voltage output from a battery that can have a terminal voltage between 9V (when discharged) and 14V (fully charged). Buck-boost converters can help stabilize the outputs of photovoltaic cells. Solar cells are able to deliver high voltage and current when in bright sunlight but revert to low voltage and low current when the sunlight is blocked or diminished. As the voltage/current relationship changes in such an example, a buck-boost converter can be quite useful for Maximum Power Point Tracking (MPPT) because the input/output voltage ratio can be continuously adjusted.
The greatest disadvantage of a buck-boost converter is its inverted output voltage. If used with a battery, the output voltage inversion is irrelevant because the battery supply can be left floating and the -VOUT may then be connected to ground in order to yield a positive-going output voltage. Another disadvantage is that the switch S1 is without a ground connection. This means that a level translator is needed in the PWM output circuit, a factor that can quickly add design cost and complexity.
Figure 3: A simplified schematic of a Buck/Boost regulator (Image from Reference 1)
The input voltage of a buck-boost converter may be higher or lower than the regulated output voltage. That capability is useful for applications that may require a stabilized voltage output from a battery that can have a terminal voltage between 9V (when discharged) and 14V (fully charged). Buck-boost converters can help stabilize the outputs of photovoltaic cells. Solar cells are able to deliver high voltage and current when in bright sunlight but revert to low voltage and low current when the sunlight is blocked or diminished. As the voltage/current relationship changes in such an example, a buck-boost converter can be quite useful for Maximum Power Point Tracking (MPPT) because the input/output voltage ratio can be continuously adjusted.
The greatest disadvantage of a buck-boost converter is its inverted output voltage. If used with a battery, the output voltage inversion is irrelevant because the battery supply can be left floating and the -VOUT may then be connected to ground in order to yield a positive-going output voltage. Another disadvantage is that the switch S1 is without a ground connection. This means that a level translator is needed in the PWM output circuit, a factor that can quickly add design cost and complexity.
DC/DC Converter Applications
DC/DC converters have numerous applications in the electronics industry. Let’s discuss the primary application areas.
Automation
In general, the main requirement for using DC/DC power supplies in automation applications centers on isolation. Isolation would ensure that the power design avoids any interference with other equipment. The DC/DC converter should also be designed into a system, taking care to avoid any ground loops or potential differences that may disturb the operation of the automatic control system.
For example, isolated DC/DC converters might be used in automation to help break up ground loops. This would allow separation of noise-sensitive parts of a circuit from the source of that noise. A regulated and isolated DC/DC converter can help minimize electrical noise using that isolation. The choice of an isolated and regulated DC/DC converter for voltage conversion would help prevent electrical noise isolation, and ensure immunity to line surges and dropout/dips.
For example, isolated DC/DC converters might be used in automation to help break up ground loops. This would allow separation of noise-sensitive parts of a circuit from the source of that noise. A regulated and isolated DC/DC converter can help minimize electrical noise using that isolation. The choice of an isolated and regulated DC/DC converter for voltage conversion would help prevent electrical noise isolation, and ensure immunity to line surges and dropout/dips.
Internet of Things (IoT) and the Industrial Internet of Things (IIoT)
The IoT is consumer-oriented while the IIoT, a subset of the IoT, is industrial-oriented. The IoT and the IIoT are systems of inter-related objects, connected on the Internet, which make it possible to collect, share, and transfer data over wireless networks with virtually no human intervention. These two systems feature distributed intelligence, countless interconnected sensors and actuators, along with decentralized control.
The IIoT is made up of devices that collect large amounts of data compared to IoT devices, which generate a relatively lower volume of data. An IIoT example is a single turbine compressor blade that can generate more than 500Gb of data every day. Beyond connectivity, IoT and IIoT are all about the information these devices can collect, leading to powerful insights. Typically, rugged, isolated DC/DC converters are needed to power IIoT sensors, such as those monitoring the condition of industrial machines. Large power surges may occur with the starting and stopping of heavy machinery. As a result, isolated DC/DC converters with isolation of 3kV to 4kV are required to protect the sensors.
Creating smart spaces, the IoT and the IIoT leverage sensors in environments/objects that can communicate to gain intelligence. IoT examples include a business setting that has lighting with smart capabilities to adjust to ambient light levels, and even to the number of people present. Within the IoT, machines can monitor their own functionality, or adapt to daily routines in homes. The IoT automatically saves energy while providing human comfort. The IoT also needs power designers that choose cost-effective and high-power-density DC/DC power supply modules. In this space, applications include smart offices, which are filled with intelligent sensor nodes. Energy harvesting is another excellent application that leverages DC/DC converters.
Power supplies for the IoT and the IIoT need to be highly efficient, at low and full load levels. DC/DC power supplies designed to handle fast transient and dynamic load currents are best suited for these environments. Such power supplies must be physically compact, reliable, and cost-effective. These DC/DC power supplies will be as ubiquitous as the sensors, processors, radios, and actuators that they are designed to power.
See this video entitled “What is the Internet of Things”.
The IIoT is made up of devices that collect large amounts of data compared to IoT devices, which generate a relatively lower volume of data. An IIoT example is a single turbine compressor blade that can generate more than 500Gb of data every day. Beyond connectivity, IoT and IIoT are all about the information these devices can collect, leading to powerful insights. Typically, rugged, isolated DC/DC converters are needed to power IIoT sensors, such as those monitoring the condition of industrial machines. Large power surges may occur with the starting and stopping of heavy machinery. As a result, isolated DC/DC converters with isolation of 3kV to 4kV are required to protect the sensors.
Creating smart spaces, the IoT and the IIoT leverage sensors in environments/objects that can communicate to gain intelligence. IoT examples include a business setting that has lighting with smart capabilities to adjust to ambient light levels, and even to the number of people present. Within the IoT, machines can monitor their own functionality, or adapt to daily routines in homes. The IoT automatically saves energy while providing human comfort. The IoT also needs power designers that choose cost-effective and high-power-density DC/DC power supply modules. In this space, applications include smart offices, which are filled with intelligent sensor nodes. Energy harvesting is another excellent application that leverages DC/DC converters.
Power supplies for the IoT and the IIoT need to be highly efficient, at low and full load levels. DC/DC power supplies designed to handle fast transient and dynamic load currents are best suited for these environments. Such power supplies must be physically compact, reliable, and cost-effective. These DC/DC power supplies will be as ubiquitous as the sensors, processors, radios, and actuators that they are designed to power.
See this video entitled “What is the Internet of Things”.
Industrial Power
In industrial applications, fork-lift trucks and other materials-handling equipment use traction batteries rated from 320V to 600V. A series of on-board power supplies can optionally generate 24V or 48V from the high-voltage battery rated at 4kW with high efficiency. A 19-inch-rack product version can be baseplate- or liquid-cooled.
Electric Vehicles (EV)
With the availability of fossil fuels decreasing, electric vehicles (EVs) have surged as a solution to reduce fossil fuel dependence and help sustain natural resources.
EV development is characterized by:
As EVs increasingly populate our roads, these cars, buses, and trucks need more charging stations, which are being deployed along major roads and highways as well as in local areas. EV charging stations’ power levels are fast reaching several kW of power. DC/DC converters with increased isolation and high insulation strength are critical to these charging stations. DC/DC converters are used to provide regulated power to the network interface of the EV charger. This component ensures reliable communication between the EV and the charging station, as well as connectivity to the Internet.
EV development is characterized by:
- increasing battery capacity
- faster charging
- longer lifespan
- improved power density
As EVs increasingly populate our roads, these cars, buses, and trucks need more charging stations, which are being deployed along major roads and highways as well as in local areas. EV charging stations’ power levels are fast reaching several kW of power. DC/DC converters with increased isolation and high insulation strength are critical to these charging stations. DC/DC converters are used to provide regulated power to the network interface of the EV charger. This component ensures reliable communication between the EV and the charging station, as well as connectivity to the Internet.
Railway
A key application for industrial high power DC/DC converters is in railway applications. This sector includes applications for railway rolling stock, on-board and trackside applications, industrial applications, high voltage battery-powered applications, and distributed power supply architectures. Typically, DC/DC converters are used in railway environments to convert DC battery voltages to a lower voltage for use in various control and energy systems. Railway rolling stock designs have a DC power distribution system that uses batteries that are deployed to maintain electrical power in the event a generator fails.
For these applications, DC/DC converters must be designed and constructed in accordance with EN 50155 to ensure that harsh environmental conditions do not affect operation. These DC/DC converters are exposed to extremely tough conditions such as heat, frost, vibration, and mechanical impact, all of which can cause serious damage to electronic components. Engineers require DC/DC converters that can withstand these potentially catastrophic conditions and are certified for railway applications.
For these applications, DC/DC converters must be designed and constructed in accordance with EN 50155 to ensure that harsh environmental conditions do not affect operation. These DC/DC converters are exposed to extremely tough conditions such as heat, frost, vibration, and mechanical impact, all of which can cause serious damage to electronic components. Engineers require DC/DC converters that can withstand these potentially catastrophic conditions and are certified for railway applications.
High Power Density
The power density of a DC/DC converter is a measure of the output power divided by the volume of the DC/DC converter, expressed as watts of output power per cubic centimeter. A high value, meaning more power for a given volume, is a design advantage.
Power in Small Packages: 3D Power Packaging for Low-Power DC/DC Converters
Low-power, non-isolated DC/DC switching regulators are cost-effective solutions that meet increasing demands for better performance with improved power density. Their packages need to be small so that they can compete with discrete designs. Non-isolated DC/DC designs face the challenge of being highly efficient while maintaining a small form factor. The use of faster switching techniques, such as in wide bandgap designs, helps reduce size while maintaining strong efficiency. RECOM achieves high power density with an over-molded “flip-chip-on-lead frame” construction. EMI is reduced due to smaller switching current loops in the design.
To increase power density with 3D Power Packaging, watch the video ‘Big power in small packages’.
To increase power density with 3D Power Packaging, watch the video ‘Big power in small packages’.
High Power Density DC/DC Converters for Industrial and Electro-Mobility Applications
The RP and RPA series are board-mounted DC/DC converters with a power rating of 30W to 240W and a power density of up to 4.5W/cm3. This is one of the highest power densities available for this class of DC/DC converters. A major reason for the excellent power density is that these devices use planar transformers in their design. These transformers reduce the overall package size without compromising efficiency or output power.
This construction method supports a fully automated production process, which leads to high reliability and excellent cost-effectiveness. These two series are best for space-constrained industrial, test-and-measurement, transport, railway, and other demanding applications that require a 4:1 input voltage range and even an excellent 10:1 input voltage range.
This construction method supports a fully automated production process, which leads to high reliability and excellent cost-effectiveness. These two series are best for space-constrained industrial, test-and-measurement, transport, railway, and other demanding applications that require a 4:1 input voltage range and even an excellent 10:1 input voltage range.
Medical
Medical applications are high risk by nature. Electronic equipment, especially those containing power electronic devices, must meet extremely high standards of safety and reliability. Medical power supplies need to have properties that meet the necessary standards for medical use in hospitals and other medical environments.
Medical-grade DC/DC converters require reinforced isolation with two means of patient protection (2MOPP), low leakage, and a creepage/clearance distance greater than 8mm. Reinforced isolation provides an added level of safety beyond standard isolation, to meet the medical safety standard ES/IEC/EN60601-1 3rd Ed. High isolation and low noise are critical to medical-grade DC/DC converters. Since patients or operators are always involved with equipment containing such devices, they must be protected in the event of a fault.
Medical-grade DC/DC converters require reinforced isolation with two means of patient protection (2MOPP), low leakage, and a creepage/clearance distance greater than 8mm. Reinforced isolation provides an added level of safety beyond standard isolation, to meet the medical safety standard ES/IEC/EN60601-1 3rd Ed. High isolation and low noise are critical to medical-grade DC/DC converters. Since patients or operators are always involved with equipment containing such devices, they must be protected in the event of a fault.
High-Grade Medical DC/DC Converters
High-grade medical DC/DC converters are designed to be safe for humans. They meet either type BF (Electrically connected to patient but not directly to heart) or CF (Electrically connected to the heart of the patient) environments. These can be used in incubators, ultrasonic devices, or defibrillators. The power supplies meet the 2MOPP (Means of Patient Protection) spec, which involves high isolation and a robust insulation capability. The internal transformers have reinforced insulation and help limit the leakage current that may reach the patient.
Some medical-grade DC/DC converters are regulated and have a 250VAC working voltage. Additional specifications may include a 5kVAC to 10kVAC/1 minute reinforced isolation and leakage currents as low as 2µA. There may be other options that can reduce standby power to milliwatt levels. A 1W converter in a very compact SIP7 package is currently the smallest complete medical supply on the market. Midpower ranges are available, too. These DC/DC converters are cost-effective at 3.5W, 5W, and 6W. They come in an SMD or THT package, with an input voltage range of 2:1, and the output voltage can be 3.3V, 5V, 9V, 12V, 15V, or 24V, depending on the series.
Some medical-grade DC/DC converters are regulated and have a 250VAC working voltage. Additional specifications may include a 5kVAC to 10kVAC/1 minute reinforced isolation and leakage currents as low as 2µA. There may be other options that can reduce standby power to milliwatt levels. A 1W converter in a very compact SIP7 package is currently the smallest complete medical supply on the market. Midpower ranges are available, too. These DC/DC converters are cost-effective at 3.5W, 5W, and 6W. They come in an SMD or THT package, with an input voltage range of 2:1, and the output voltage can be 3.3V, 5V, 9V, 12V, 15V, or 24V, depending on the series.
Cost-Effective Medical DC/DC Converters
These DC/DC converters have reinforced 250VAC continuous working isolation with greater than 8mm creepage/clearance and provide 2MOPP. They also come with extended reinforced isolation of up to 8kVDC, making them suitable for high-voltage applications. All key features required for critical medical applications are included, while keeping costs contained. The DC/DC converters are available with both pins as well as surface mount devices.
DC/DC Converter Selection Considerations
Isolated DC/DC converters offer the following advantages:
Non-isolated DC/DC converters offer this advantage:
- Isolating the grounding between input and output means that the grounding scheme of the DC source can be different from the load on the output
- Designers can “map” a wide range of different levels of DC voltage on the input relative to the output
- If the converters have very low capacitance on their output, they will more readily and safely allow multiple, isolated DC/DC converters to be placed in parallel on the same DC bus
Non-isolated DC/DC converters offer this advantage:
- Their DC input and output are connected to the same potential. These types of DC/DC converters are buck, boost, or buck-boost.
Bidirectional DC/DC Converters
A bidirectional DC/DC converter is a relatively new architecture in many emerging applications, including automotive, server, and renewable-energy systems. Low-voltage bidirectional DC/DC converters are typically non-isolated. There are three key applications: automotive, server, and renewable-energy systems.
AC/DC Converters: A Basic Overview
The transformer in Figure 4 has two primary windings of 115V which are shown connected in parallel or series via the input voltage selector switch. The two series-wired 6V secondary windings lead to a nominal 12VAC output which becomes rectified by the bridge rectifier BR and then DC-smoothed by the output capacitor, C. This gives a typical output voltage of about 14VDC. The full-bridge rectifier uses a four-diode typical configuration.
Fig. 4: An example of an unregulated basic AC/DC converter power supply (Image from Reference 2)
Fig. 4: An example of an unregulated basic AC/DC converter power supply (Image from Reference 2)
AC/DC Converter Applications
Among the many applications for AC/DC converters, let’s explore the primary ones.
Medical
When electronic devices do not come into direct contact with the patient and are only handled by trained operators, they are classified as Means of Operator Protection (MOOP). This means they typically only need to meet the 60950-1 and 62368-1 ITE standards for Laboratory Environment Compliance. Medical electronic designs use a MOPP, an electrical safety standard used by standards organizations across the globe. These include the American National Standards Institute (ANSI), Canadian Standards Association, and European Commission under IEC60601-1. MOPP safety standards establish basic requirements for medical electrical equipment.
Medical applications using AC/DC power supplies achieve the highest level of safety protection when they use 2MOPP. Note that some power supply manufacturers highlight units as meeting medical approvals regardless of whether the unit has 1MOPP or 2MOPP. These compact medical-grade power supplies have a universal AC input voltage range, 4kVAC isolation, low standby power consumption, active PFC (> 0.95), and do not require a minimum load.
Listen to this podcast for more details "Medical-Grade AC/DC converters - RACM series".
Medical applications using AC/DC power supplies achieve the highest level of safety protection when they use 2MOPP. Note that some power supply manufacturers highlight units as meeting medical approvals regardless of whether the unit has 1MOPP or 2MOPP. These compact medical-grade power supplies have a universal AC input voltage range, 4kVAC isolation, low standby power consumption, active PFC (> 0.95), and do not require a minimum load.
Listen to this podcast for more details "Medical-Grade AC/DC converters - RACM series".
Automation
Automation refers to technology that uses sensors, actuators, and feedback techniques to operate independently, without continuous control. An isolated local power supply is an essential part of the power architecture that supplies the sensor/feedback/actuator control system. Automation-technology power supplies include devices and modules required to supply AC/DC power to sensors, evaluation units and actuators with electrical power. They convert voltage from normal energy networks to levels suitable for sensors and actuators, ensuring reliable operation within a system. These power supplies are usually isolated so that cross-interference, ground loops, and potential differences do not disrupt the automatic control system.
Internet of Things (IoT) & Industrial Internet of Things (IIoT)
The IIoT is a subset of the IoT, sharing common technologies such as sensors, connectivity, cloud platforms, and analytics. The IoT enables distributed intelligence, featuring multiple/interconnected sensors and actuators with a focus on decentralized control. Sensors integrated into designated spaces, environments, or objects create “smart” systems by adding communication-enabled intelligent sensors. To power the IoT, designers use high-efficiency AC/DC power supplies with low standby power consumption. Application areas include smart offices, equipped with numerous intelligent sensor nodes, as well as energy harvesting.
Let’s discuss the requirements for a mains-powered AC/DC supply for IoT applications.
The AC/DC supply needs to be low power, since typical devices require only a few watts. The supply should be small, to accommodate the tight space constraints of IoT sensors. Additionally, the supply must handle a wide variation in load current, reflecting the periodic transitions of the IoT node between active and sleep modes. The AC/DC converter must include this important feature: a very low, no-load power consumption. These AC/DC converters also need to meet the requirements for worldwide certification, ensuring compatibility to power systems in commercial and industrial environments, whether domestic or foreign. Cost-effectiveness is critical, as a high volume of supplies is needed for widespread IoT implementations.
Watch this video titled “What is the Internet of Things.”
Let’s discuss the requirements for a mains-powered AC/DC supply for IoT applications.
The AC/DC supply needs to be low power, since typical devices require only a few watts. The supply should be small, to accommodate the tight space constraints of IoT sensors. Additionally, the supply must handle a wide variation in load current, reflecting the periodic transitions of the IoT node between active and sleep modes. The AC/DC converter must include this important feature: a very low, no-load power consumption. These AC/DC converters also need to meet the requirements for worldwide certification, ensuring compatibility to power systems in commercial and industrial environments, whether domestic or foreign. Cost-effectiveness is critical, as a high volume of supplies is needed for widespread IoT implementations.
Watch this video titled “What is the Internet of Things.”
Home Automation, Smart Homes & Smart Office
Intelligently networked smart homes and smart offices require control systems with a large number of low-power nodes, actuators and sensors, typically operating in an “always on” state. Cost-effective AC/DC power supplies for home automation need to be able to power smart building infrastructures continuously with very low standby power consumption (e.g., just tens of milliwatts). These AC/DC supplies require an extra-wide input voltage range and compliance with full household (IEC/EN60335-1), CE (LVD+EMC+RoHS2) and industrial safety certifications (IEC/EN/UL60950).
In home automation, as well as in smart homes and smart offices, AC/DC power supplies must feature compact designs to simplify assembly techniques for installation both on and off the power boards. These supplies must also deliver local DC power with reinforced isolation while being regulated, short-circuit-proof, and overload-protected for the powering of smart-home automation applications. Designers can select 1W to 20W converters for versatile installation options or opt for 3W to 30W converters, which need to accommodate standard recessed wall boxes.
Low standby power consumption is also required: as low as 35mW, which falls below the European Commission ErP Ecodesign directive limits.
In home automation, as well as in smart homes and smart offices, AC/DC power supplies must feature compact designs to simplify assembly techniques for installation both on and off the power boards. These supplies must also deliver local DC power with reinforced isolation while being regulated, short-circuit-proof, and overload-protected for the powering of smart-home automation applications. Designers can select 1W to 20W converters for versatile installation options or opt for 3W to 30W converters, which need to accommodate standard recessed wall boxes.
Low standby power consumption is also required: as low as 35mW, which falls below the European Commission ErP Ecodesign directive limits.
Industrial Automation
Industrial AC/DC power converters are frequently used for battery charging. Three-phase AC input battery chargers typically offer ratings of 3.2kW (RMOC3200 series with DC inputs up to 800V) and 5kW (RMOC5000 series) and must support cascading up to 20kW. Both series have outputs for 24/36/48/72/96/110V nominal. The SD2800 series, operates at nominal 44V or 24V three-phase AC input and provides 28V or 14V, respectively, at 2.8kW and 1.4kW. The SAB10000 series provides 10kW of battery charging from three-phase AC (20VDC output) or 600VDC nominal input (24VDC output). The series is also bidirectional so that battery charge can be returned to the AC. Modular, standalone power factor correction front ends are available at 800W, 1600W and 3200W (single-phase AC input) and at 4kW (three-phase AC input). These products are available in 19-inch racks, open-frame or chassis formats, or custom configurations.
High Power Density
Power density, which measures the power output per unit volume, is important in a power supply, especially in space-constrained environments. In power electronics, improving efficiency is important because it enhances power density. One sure way to increase power density is to reduce component sizes. Designers should choose the smallest possible capacitors, inductors, transformers, and heat sinks that still meet design needs. Applications that require the highest efficiency (in the order of 99%) and high-power density (73 W/in³) are high-end servers and telecommunications. Not surprisingly, AC/DC converters are used in these applications.
Industrial
Modern industry demands smaller sizes and footprint, with solid power density numbers. Modern advances in switching controllers, topologies and components enable AC/DC power supplies to achieve twice the power density of previously designed converters. To compete, new designs must improve safety, reliability, efficiency, and performance. Designers must know how much AC input voltage swing their selected AC/DC converter will be handling in their design.
In most industries, the output from the AC mains ranges from a nominal 100 VAC up to 277 VAC for use around the globe. It is critical that the AC/DC converter function efficiently over the entire load range, from full load to light load, and even in no-load conditions. Most AC/DC converters are internationally safety certified to UL/IEC/EN standards, with Certification Body (CB) Reports. Saving energy is critical to customers, and many applications switch automatically into standby to reduce power consumption.
In most industries, the output from the AC mains ranges from a nominal 100 VAC up to 277 VAC for use around the globe. It is critical that the AC/DC converter function efficiently over the entire load range, from full load to light load, and even in no-load conditions. Most AC/DC converters are internationally safety certified to UL/IEC/EN standards, with Certification Body (CB) Reports. Saving energy is critical to customers, and many applications switch automatically into standby to reduce power consumption.
Test and Measurement
In the Test and Measurement sector, devices range from desktop products to server rack installations. These systems need AC input voltages, which can span a nominal 90VAC to 277VAC and sometimes higher for industrial applications. Low power, PCB-mounted AC/DC converters range between 3W and 20W and are frequently designed into these systems. If higher power is needed, such as from 40W to 550W, designers may choose chassis-mounted options. Operating without a fan is challenging in a Test & Measurement environment. For this setting, all selected AC/DC converter solutions must be able to provide useful power at high temperatures without the benefit of forced air.
230W and 550W products are available with the addition of baseplate cooling. Safety certifications for different end-application environments are available according to IEC/EN 61010, IEC/EN 62368, IEC/EN 60601, and EN 60335 requirements. AC/DC converters must meet electromagnetic compatibility (EMC) standards without using any added components. All AC/DC devices must have low mains leakage current, critical in test and measurement applications and, particularly, in medical environments. Applications that require sensitive measurements need low-output noise AC/DC power supplies, which benefit designers in many test and measurement systems.
230W and 550W products are available with the addition of baseplate cooling. Safety certifications for different end-application environments are available according to IEC/EN 61010, IEC/EN 62368, IEC/EN 60601, and EN 60335 requirements. AC/DC converters must meet electromagnetic compatibility (EMC) standards without using any added components. All AC/DC devices must have low mains leakage current, critical in test and measurement applications and, particularly, in medical environments. Applications that require sensitive measurements need low-output noise AC/DC power supplies, which benefit designers in many test and measurement systems.
Mobility and e-Mobility
AC/DC converters can provide power to electronic devices that require a conversion process from AC to DC. In this section, we will discuss applications for AC/DC converters in both mobility and e-mobility.
Mobile vs. Mobility: The term ‘mobile’ pertains to mobile technology and devices, which are essentially the ‘nuts and bolts’ that enable mobility. Mobility is an umbrella term for mobile and ensures whether everything within the nuts and bolts work well together.
Mobile vs. Mobility: The term ‘mobile’ pertains to mobile technology and devices, which are essentially the ‘nuts and bolts’ that enable mobility. Mobility is an umbrella term for mobile and ensures whether everything within the nuts and bolts work well together.
e-Mobility
The typical applications for e-mobility include electric vehicles (EV), all types of scooters, and similar small vehicles. These devices need battery chargers and on-board power converters for device motor drives and any auxiliary equipment. To replace gasoline-engine vehicles with electric power, a larger network of charging stations and outlets is needed. Currently, approximately 113,600 charging outlets exist in the United States for plug-in electric vehicles along roadways; 36% of them are in the state of California. There is a concerted effort under way to build much faster chargers to lower existing charging times to under 20 minutes.
In more complex products, added features like battery conditioning and bidirectional converters for energy balancing are needed. A solid performance range of suitable AC/DC converters is necessary for these kinds of applications. Battery conditioners (computerized devices that charge, maintain, and prevent sulfation from occurring in lead batteries), along with power-factor front ends, would reduce harmonic distortion (for example from 45% to 5%) and significantly improve system power factor performance. Power factor measures how efficiently the electrical power is being used to perform useful work.
AC/DC e-mobility applications need to be rugged, reliable with long lifetimes, have broad environmental capability with sealed and weatherproof options, power factor correction (PFC), battery charging/conditioning capability, and 20kW+ rating. High power AC/DC converters can be used for special applications. One typical example is an AC/DC converter that can operate at nominal 44V or 24V three-phase AC input while providing a 28V or 14V capability at either 2.8kW or 1.4kW. Other AC/DC devices are battery chargers/conditioners specially designed for the e-mobility market, which is categorized by battery voltages of less than 24V, 24V, 36V, 48V, and even greater than 48V. The 24V segment typically accounts for more than 25% of the electric mobility revenue share. These AC/DC converters are rated at 2kW and 1kW, respectively, with excellent wide output operating voltage ranges to enable designers with flexible applications.
In this segment, some AC/DC converters have modular standalone power factor correction front ends that are also available rated at 800W, 1600W, and 3200W (single-phase AC input) and at 4kW (three-phase AC input). Some of these AC/DC solutions fit into designs in a 19-inch rack, open-frame or chassis formats. Other key applications for these AC/DC converters in e-mobility are EVs and EV charging systems, with the addition of railway and transportation.
In more complex products, added features like battery conditioning and bidirectional converters for energy balancing are needed. A solid performance range of suitable AC/DC converters is necessary for these kinds of applications. Battery conditioners (computerized devices that charge, maintain, and prevent sulfation from occurring in lead batteries), along with power-factor front ends, would reduce harmonic distortion (for example from 45% to 5%) and significantly improve system power factor performance. Power factor measures how efficiently the electrical power is being used to perform useful work.
AC/DC e-mobility applications need to be rugged, reliable with long lifetimes, have broad environmental capability with sealed and weatherproof options, power factor correction (PFC), battery charging/conditioning capability, and 20kW+ rating. High power AC/DC converters can be used for special applications. One typical example is an AC/DC converter that can operate at nominal 44V or 24V three-phase AC input while providing a 28V or 14V capability at either 2.8kW or 1.4kW. Other AC/DC devices are battery chargers/conditioners specially designed for the e-mobility market, which is categorized by battery voltages of less than 24V, 24V, 36V, 48V, and even greater than 48V. The 24V segment typically accounts for more than 25% of the electric mobility revenue share. These AC/DC converters are rated at 2kW and 1kW, respectively, with excellent wide output operating voltage ranges to enable designers with flexible applications.
In this segment, some AC/DC converters have modular standalone power factor correction front ends that are also available rated at 800W, 1600W, and 3200W (single-phase AC input) and at 4kW (three-phase AC input). Some of these AC/DC solutions fit into designs in a 19-inch rack, open-frame or chassis formats. Other key applications for these AC/DC converters in e-mobility are EVs and EV charging systems, with the addition of railway and transportation.
Mobility
The term Mobility refers to EVs, disability scooters, and other small mobile vehicles. These vehicles need battery chargers as well as on-board power management to drive motors and auxiliary equipment. The key features of AC/DC converters in this sector are ruggedness, long lifetime, high reliability, extreme environmental requirements, weatherproofing and sealing of AC/DC power solutions, PFC, and power ratings up to and exceeding 20kW. In battery conditioning and conditioning, bidirectional power converters are used for energy balancing. Power factor front ends are also a part of mobility. There are also working platform power designs that may be adapted to customer specifications for new and custom designs.
Fake vs. Original Components
Counterfeit power supply components can wreak havoc in the design world. These devices can malfunction or not function at all. If they do function, they potentially can injure people or even cause a fire. Naturally, any of those outcomes would severely hurt a supplier’s reputation.
The Importance of the Right Partner
It is highly recommended that buyers purchase known manufacturer products from their global distributors. Savvy designers and purchasing people know that acquiring electronic components and power supplies from trusted distributors and manufacturers represent the best route to ensure a fully functional, reliable, and safe end-product design.
References
(1) Chapter 1 An Introduction to Buck, Boost, and Buck/Boost Converters, RECOM DC/DC Book of Knowledge
(2) Chapter 2 Linear AC/DC Power Supplies, RECOM AC/DC Book of Knowledge
(2) Chapter 2 Linear AC/DC Power Supplies, RECOM AC/DC Book of Knowledge