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’.
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’.
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.
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.
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 SIP-7 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 SIP-7 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 can have these advantages:
- 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 will be able to “map” a large range of different levels of DC voltage on the input relative to the output
- If they 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
- Their DC input and output are connected to the same potential. These types of DC/DC converters are Buck, Boost or Buck-Boost.
Bi-directional DC/DC converters
A bidirectional DC/DC converter is a relatively new architecture in many new applications, including automotive, server and renewable-energy systems. Low-voltage bidirectional DC/DC converters are typically non-isolated.
Three key applications for Bi-directional DC/DC converters are automotive, server and renewable-energy systems.
Three key applications for Bi-directional DC/DC converters are automotive, server and renewable-energy systems.
A basic AC/DC converter overview
Figure 4: An example of an unregulated basic AC/DC converter power supply (Image from Reference 2)
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.
AC/DC Converter applications
There are many key applications for AC/DC converters and in this section, the primary application areas for AC/DC converters will be discussed.
Medical
When electronic devices do not come into direct contact with the patient and are only handled by trained operators they are classified in category Means of Operator Protection (MOOP), which means they typically only need to meet 60950-1 and 62368-1 ITE standards for Laboratory Environment Compliance.
Medical electronic designs use a Means of Patient Protection (MOPP), an electrical safety standard set forward by standards organizations across the globe; these are the American National Standards Institute (ANSI), Canadian Standards Association, and European Commission in IEC60601-1. MOPP safety standards set basic the safety requirements for medical electrical equipment.
Medical applications for AC/DC power supplies with 2 x Means of Patient Protection (MOPP) safety approval for mains-powered medical applications. The highest level of safety protection comes from using 2 x MOPP. Note that some power supply manufacturers typically highlight power supplies as meeting medical approvals whether the unit has 1 MOPP or 2 MOPP.
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.
See this podcast for more details
Medical electronic designs use a Means of Patient Protection (MOPP), an electrical safety standard set forward by standards organizations across the globe; these are the American National Standards Institute (ANSI), Canadian Standards Association, and European Commission in IEC60601-1. MOPP safety standards set basic the safety requirements for medical electrical equipment.
Medical applications for AC/DC power supplies with 2 x Means of Patient Protection (MOPP) safety approval for mains-powered medical applications. The highest level of safety protection comes from using 2 x MOPP. Note that some power supply manufacturers typically highlight power supplies as meeting medical approvals whether the unit has 1 MOPP or 2 MOPP.
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.
See this podcast for more details
Automation
Automation is technology which uses sensors, actuators, and feedback techniques which can function without continuous control. An isolated local power supply is part of the power architecture that will supply the sensor/feedback/actuator control system.
Automation technology power supplies are those devices and modules that are required to supply AC/DC power to sensors, evaluation units and actuators with electrical power. Voltage that is supplied, from normal energy networks, is converted to the proper voltage and power that needs to be applied to sensor and actuator devices in order to ensure their important operation in a system.
These power supplies are usually isolated so that interference from cross-interference, ground loops, and potential differences, will not interfere with the automatic control system.
Automation technology power supplies are those devices and modules that are required to supply AC/DC power to sensors, evaluation units and actuators with electrical power. Voltage that is supplied, from normal energy networks, is converted to the proper voltage and power that needs to be applied to sensor and actuator devices in order to ensure their important operation in a system.
These power supplies are usually isolated so that interference from cross-interference, ground loops, and potential differences, will not interfere with the automatic control system.
Internet of Things (IoT) and the Industrial Internet of Things (IIoT)
The IIoT is a subset of the IoT. This is because they both share common technologies such as sensors, connectivity, cloud platforms, as well as analytics.
The IoT enables a distributed intelligence, with multiple/interconnected sensors and actuators with decentralized control. Sensors are part of designated spaces, environments or objects that become “smart” via the addition of intelligent sensors that are able to communicate.
In order to power the IoT, designers use high efficiency AC/DC power supplies with low standby power consumption. Application areas include Smart Offices, with many intelligent sensor nodes, as well as energy harvesting.
Let’s take a look at the requirements for a mains-powered AC/DC supply for IoT applications.
The AC/DC supply needs to be low power, since only a few watts will typically be needed. The supply should be small, to meet the tight space constraints of IoT sensors which are compact. The AC/DC supply should also be able to handle a wide variation in load current, because the IoT node will periodically switch from active to sleep mode.
The AC/DC converter needs to have the important feature of a very low, no-load power consumption. These AC/DC converters will also need requirements for worldwide certification, in order to power systems in a domestic and foreign, commercial and industrial, environment. These power supplies need to be quite cost effective since there are needs for a great number of supplies in so many worldwide designs. See this video entitled “What is the ‘Internet of Things.”
The IoT enables a distributed intelligence, with multiple/interconnected sensors and actuators with decentralized control. Sensors are part of designated spaces, environments or objects that become “smart” via the addition of intelligent sensors that are able to communicate.
In order to power the IoT, designers use high efficiency AC/DC power supplies with low standby power consumption. Application areas include Smart Offices, with many intelligent sensor nodes, as well as energy harvesting.
Let’s take a look at the requirements for a mains-powered AC/DC supply for IoT applications.
The AC/DC supply needs to be low power, since only a few watts will typically be needed. The supply should be small, to meet the tight space constraints of IoT sensors which are compact. The AC/DC supply should also be able to handle a wide variation in load current, because the IoT node will periodically switch from active to sleep mode.
The AC/DC converter needs to have the important feature of a very low, no-load power consumption. These AC/DC converters will also need requirements for worldwide certification, in order to power systems in a domestic and foreign, commercial and industrial, environment. These power supplies need to be quite cost effective since there are needs for a great number of supplies in so many worldwide designs. See this video entitled “What is the ‘Internet of Things.”
Home Automation, Smart Homes, and Smart Office
Intelligently networked smart homes and smart offices will require control systems with a large number of low power nodes, actuators and sensors which will typically be “always on”. Cost effective AC/DC power supplies for home automation need to be able to power smart building infrastructures 24/7 with very low standby power consumption (such as just tens of mW). These AC/DC supplies must also have an extra-wide input voltage range and full household (IEC/EN60335-1), CE (LVD+EMC+RoHS2) and industrial safety certifications (IEC/EN/UL60950).
AC/DC power supplies, in Home Automation, Smart Homes, and Smart Offices, will need to have compact sizes so that assembly techniques can easy install on- or off-the power board. These supplies must also be able to deliver local DC power with reinforced isolation that will be reliable, regulated, short-circuit proof and overload-protected for the powering of smart home automation applications.
Designers can use 1 to 20W converters for versatile installation options and 3 to 30W converters which will have to fit into standard recessed wall boxes.
These AC/DC converters also need to have low standby power consumption: down to 35mW (this is below European Commission ErP Ecodesign directive limits)
AC/DC power supplies, in Home Automation, Smart Homes, and Smart Offices, will need to have compact sizes so that assembly techniques can easy install on- or off-the power board. These supplies must also be able to deliver local DC power with reinforced isolation that will be reliable, regulated, short-circuit proof and overload-protected for the powering of smart home automation applications.
Designers can use 1 to 20W converters for versatile installation options and 3 to 30W converters which will have to fit into standard recessed wall boxes.
These AC/DC converters also need to have low standby power consumption: down to 35mW (this is below European Commission ErP Ecodesign directive limits)
Industrial Automation
Industrial AC/DC Power Converters are often used for battery charging.
Three-phase AC input battery chargers typically have ratings at 3.2kW (RMOC3200 series with DC inputs up to 800V) and 5kW (RMOC5000 series) must be able to be cascaded up to 20kW. Both of these series have outputs for 24/36/48/72/96/110 V 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) but is also bi-directional so that battery charge can be returned to the AC.
Modular, stand-alone 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“ rack, open frame or chassis formats, or to customer specification.
Three-phase AC input battery chargers typically have ratings at 3.2kW (RMOC3200 series with DC inputs up to 800V) and 5kW (RMOC5000 series) must be able to be cascaded up to 20kW. Both of these series have outputs for 24/36/48/72/96/110 V 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) but is also bi-directional so that battery charge can be returned to the AC.
Modular, stand-alone 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“ rack, open frame or chassis formats, or to customer specification.
High Power Density
Power density is a measure of power output per unit volume. This is important in a power supply, especially in a space-restricted area.
Efficiency is a prime issue in power electronics. Improving efficiency in power supplies will improve 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 will 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 telecom. AC/DC converters are used in such an applications.
Efficiency is a prime issue in power electronics. Improving efficiency in power supplies will improve 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 will 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 telecom. AC/DC converters are used in such an applications.
Industrial
Modern industry demands decreasing size, footprint, with solid power density numbers than AC/DC predecessors. Modern advances in switching controllers, topologies and components enable AC/DC power supplies to have 2X the power density than in previously designed converters. New designs must improve upon safety, reliability, efficiency, and performance in order to be competitive.
Designers must know how much input AC input voltage swing their selected AC/DC converter will be handling in their design. In most industry in the Western hemisphere, the output from the AC mains range 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 down to light load, and even to 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 in order to reduce power consumption.
Designers must know how much input AC input voltage swing their selected AC/DC converter will be handling in their design. In most industry in the Western hemisphere, the output from the AC mains range 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 down to light load, and even to 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 in order to reduce power consumption.
Test & Measurement
In the Test & Measurement sector, devices can span from desktop products to server rack installations. Such systems need AC input voltages which can span a nominal 90VAC to 277VAC, and often times higher for some industrial applications.
Low power, PCB mounted AC/DC converters, range from 3W to 20W 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 environment is often challenging in a Test & Measurement environment. All selected AC/DC converter solutions for this environment 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, EN 60335 requirements.
Good AC/DC converters will need to meet ElectroMagnetic Compatibility (EMC) standards without the use of any added components. All AC/DC devices will need to have low mains leakage current that is critical in Test & Measurement applications, and in particular in medical environments. Applications that require sensitive measurements, will need low output noise AC/DC power supplies which is a significant benefit to designers in many Test & Measurement systems.
Low power, PCB mounted AC/DC converters, range from 3W to 20W 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 environment is often challenging in a Test & Measurement environment. All selected AC/DC converter solutions for this environment 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, EN 60335 requirements.
Good AC/DC converters will need to meet ElectroMagnetic Compatibility (EMC) standards without the use of any added components. All AC/DC devices will need to have low mains leakage current that is critical in Test & Measurement applications, and in particular in medical environments. Applications that require sensitive measurements, will need low output noise AC/DC power supplies which is a significant benefit to designers in many Test & Measurement systems.
Mobility and e-Mobility
AC/DC converters are able to 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’ is regarding mobile technology and devices, which are essentially the ‘nuts and bolts’ that enable mobility. Mobility is an umbrella for mobile and ensures whether or not everything within the nuts and bolts will work well together.
Mobile vs. Mobility: The term ‘mobile’ is regarding mobile technology and devices, which are essentially the ‘nuts and bolts’ that enable mobility. Mobility is an umbrella for mobile and ensures whether or not everything within the nuts and bolts will work well together.
e-Mobility
e-Mobility includes such typical applications include electric vehicles (EV), all types of scooters which are so popular in today’s market, and similar other small vehicles. These devices need battery chargers as well as on-board power converters for device motor drives and any auxiliary equipment.
In order to be successful in replacing gasoline engine vehicles with electric power, a larger network of charging stations and outlets will be needed. An example for faster deployment of charging stations is that there exist only approximately 113,600 charging outlets in the United States today for plug-in electric vehicles along U.S. roadways and 36% of them are in the state of California.
There is a present effort to build much faster chargers to lower existing charging times to under 20 minutes.
In more complex products there is the need to have added features like battery conditioning and bi-directional converters for energy balancing. 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’, will reduce harmonic distortion (for example from 45% to 5%) and significantly improve system power factor performance. Power factor is basically a measure of 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 capable of operating at nominal 44V or 24V three-phase AC input while providing a 28V or 14V capability at either 2.8kW and 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.
Some AC/DC converters in this segment will have modular stand-alone power factor correction ‘front ends’ 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 19“ rack, open frame or chassis formats.
Other key applications, for these types of AC/DC converters, in e-Mobility, are Electric Vehicles and Electric Vehicle charging systems, with the addition of Railway and Transportation as well.
In order to be successful in replacing gasoline engine vehicles with electric power, a larger network of charging stations and outlets will be needed. An example for faster deployment of charging stations is that there exist only approximately 113,600 charging outlets in the United States today for plug-in electric vehicles along U.S. roadways and 36% of them are in the state of California.
There is a present effort to build much faster chargers to lower existing charging times to under 20 minutes.
In more complex products there is the need to have added features like battery conditioning and bi-directional converters for energy balancing. 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’, will reduce harmonic distortion (for example from 45% to 5%) and significantly improve system power factor performance. Power factor is basically a measure of 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 capable of operating at nominal 44V or 24V three-phase AC input while providing a 28V or 14V capability at either 2.8kW and 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.
Some AC/DC converters in this segment will have modular stand-alone power factor correction ‘front ends’ 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 19“ rack, open frame or chassis formats.
Other key applications, for these types of AC/DC converters, in e-Mobility, are Electric Vehicles and Electric Vehicle charging systems, with the addition of Railway and Transportation as well.
Mobility
The term ‘Mobility’ refers to Electric Vehicles (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, fairly extreme environmental requirements, weatherproofing and sealing of AC/DC power solutions, Power Factor Correction (PFC), and power ratings up to and exceeding 20kW.
In this area, battery conditioning and conditioning, bi-directional power converters employed for energy balancing. Power Factor Front Ends are also a part of Mobility.
There are also working platform power designs, for Mobility applications, that may be adapted to customer specifications for new and custom designs.
The key features of AC/DC converters in this sector are ruggedness, long lifetime, high reliability, fairly extreme environmental requirements, weatherproofing and sealing of AC/DC power solutions, Power Factor Correction (PFC), and power ratings up to and exceeding 20kW.
In this area, battery conditioning and conditioning, bi-directional power converters employed for energy balancing. Power Factor Front Ends are also a part of Mobility.
There are also working platform power designs, for Mobility applications, that may be adapted to customer specifications for new and custom designs.
Fakes vs originals
Counterfeit power supply components can wreak havoc in the design arena. These devices can malfunction or not even function at all. If they do function, they can still be a danger to injure people or even cause a fire. These will 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 will be the best route to ensure a fully functional, reliable, and safe end design.
Savvy designers and purchasing people know that acquiring electronic components and power supplies, from trusted distributors, and manufacturers will be the best route to ensure a fully functional, reliable, and safe end 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