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Discrete Power Components
Silicon (Si), Silicon Carbide (SiC), and Gallium Nitride (GaN) Semiconductors
Transistors
Diodes
Thyristors
Power Management Integrated Circuits (PMICs)
Linear Voltage Regulators
Switching Voltage Regulators
Power Supplies
Isolated Power Supply
Non-Isolated Power Supply
Limits on Isolated Power Supplies
What form factors do power supplies come in?
Off-Board Power Supplies
Board Mount Power Supplies
Power Bricks
Thermal Management in Power
Fans
Heat Sinks
Thermal Interface Materials (TIM)
Products
Power Solutions and Technologies
Power is divided into 3 product categories:
- Discrete Power Components: Referring to components that can be used with PMICs, or individually to create specifically tailored solutions. Getting down to this level provides the greatest flexibility but also commonly the greatest amount of development and expertise is required.
- Power Management Integrated Circuit (PMIC): Referring to a wide range of Application-Specific ICs or ASICs. They generally take more planning (and often additional discrete components) to create a full solution than using a power supply.
- Power Supplies: Referring to a device which transforms power, often stepping up or down a voltage. There is not as much customization at this level and leaves the power solution to more of a black box.
There's also an overarching theme of Thermal Management.
Discrete Power Components
Discrete power components are the individual devices that can be put together to play the same role as a PMIC or power supply. Semiconductor discrete components for power include transistors, diodes, and thyristors. Whereas passive components for power include resistors, capacitors, and inductors.
Silicon (Si), Silicon Carbide (SiC), and Gallium Nitride (GaN) Semiconductors
Traditional Semiconductor:
- Silicon (Si) – With many decades of large-scale production and process improvement, Si based components can be created with comparatively low defect ratios resulting in less expensive products.
Wide Band Gap (WBG) Semiconductors:
- Gallium Nitride (GaN) – GaN components can typically handle higher switching frequencies.
- Silicon Carbide (SiC) – SiC components can typically handle higher operating voltages, higher temperatures, and higher power.
Frequency and power ranges best suited for devices
Photo Credit: GaN: Pushing the limits of power density & efficiency
Transistors
Discrete semiconductor devices that amplify or switch power signals. Transistors are typically three terminal devices.
Transistors Product Selection Guide
- FETs, MOSFETs – Field-Effect Transistor (FET) is a transistor that operates off field-effect to control current flowing through the drain and source. Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET) is a four terminal FET that is widely used in switched mode power supplies.
- IGBTs – Insulated Gate Bipolar Transistors (IGBTs) are four-layer semiconductor devices (PNPN) that can handle high currents and used mainly for switching.
- HEMTs – High-electron-mobility transistor (HEMT) is a FET that incorporates different band gap materials.
Diodes
Diodes are usually semiconductors, there goal being to allow current in only one direction.
- Rectifier Diode – Used often to convert an AC wave form into a unipolar waveform. A single rectifier diode maybe used in a half-wave rectifier, where as a bridge rectifier can be used in full-wave rectification.
- Zener Diode – Zener diodes are created to gracefully operate in a forward and reverse current direction. The reverse direction of current is enabled when Zener voltage is reached.
Thyristors
Thyristors are four-layer semiconductor devices (PNPN) that act as a switch that only let current flow when a pulse is applied to its gate.
Power Management Integrated Circuits (PMICs)
PMIC, or Power Management Integrated Circuits, refer to a wide range of Application-Specific ICs or ASICs. These devices are intended to be either be bread boarded in a prototyping phase or soldered to a PCB in a production phase. They generally take more planning (and often additional discrete components) to create a full solution than using a power supply.
What is the difference between linear and switching regulators? View Answer
Linear and Switching Regulators are DC-DC Converters that get commonly used to stabilize output voltage supplied to the load.
Linear Regulators are often a starting point for a school project, as they are generally cheaper and easier to use. Linear Regulators create a constant output voltage by using a series of transistors, and the excess voltage gets dissipated as heat. The downside is that the dissipated heat is wasted energy, and if there's too much heat dissipated in this way, it can destroy the regulator.
Switching Voltage regulators can more efficiently stabilize the voltage output and waste less energy in the process. Switching Voltage regulators can be a good investment if you have a project that is consistently powered, or if you're looking for something more robust.
Linear Voltage Regulators
Linear Voltage Regulators are DC-DC Converters that can output a stable output voltage. Linear Voltage Regulators need to account for the power loss it can introduce and the resulting heat dissipation. It can be advantageous over a switching regulator in some cases due to its small footprint, high accuracy, and low output noise. Generally, more suitable for low current applications due to efficiency and power dissipation concerns.
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Low Dropout (LDO) Linear Regulator – can have the input voltage close to the output voltage which reduces the amount of power loss.
An example of an LDO
An example of an LDO
Switching Voltage Regulators
Switching voltage regulators take the input signal and quickly turn it on and off to create a stable output voltage. There is generally less power loss in a switching regulator. Also, there are a wider range of input to output voltages that can be covered by a switching regulator.
Some Common Types of DC-DC Switching Regulators
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Buck – Steps down the output voltage. Often used in power supplies and LED drivers.
Source: Texas Instruments
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Boost – Steps up the output voltage. Often used in battery powered devices.
Source: Texas Instruments
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Buck Boost – Can step up or down the voltage. Often used in applications with varying input voltages.
Source: Texas Instruments
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Source: Power Supplies
Power Supplies in this context are used to describe a self-contained device that takes electrical power from a source and converts it to a suitable load power.
What is the difference between isolated and non-isolated power supplies? View Answer
Galvanic isolation means that there are separate electrical and physical paths between the input and output circuits. This electrical isolation is commonly achieved via a transformer or coupled inductors between the input and output circuitry. AC-DC conversion is usually isolated, and isolation becomes more of a variable in DC-DC conversion. The reasons for creating the isolation is usually for safety (reducing the chance of shock to anyone operating near the power supply), or reduction of noise to the output circuit.
Isolated Power Supply
Non-Isolated Power Supply
Limits on Isolated Power Supplies
The isolation voltage (on the data-sheet) is the short-term amount of voltage that can be experienced without breakdown. Working voltage or maximum operating voltage is the continuous maximum voltage that can be applied without breakdown.
What form factors do power supplies come in?
Board mount power supplies are products that are intended to be directly affixed to a Printed Circuit Board (PCB), whereas off-board power supplies are not.
What is the difference between off-board and board mount power supplies? View Answer
Board mount power supplies are products that are integrated directly into the system they power. They are directly affixed to a Printed Circuit Board (PCB). Off-board power supplies are sometimes referred to as external power supplies. An example of an off-board power supply is a wall mount plug. The adapter plugs into the wall and then interfaces to the system via a connector.
Off-Board Power Supplies
Enclosed – The enclosure gives a layer of protection from debris, it increases safety, however this enclosure is likely to trap heat and often requires more cooling.
Open Frame – Open frame does not come with a lid. It runs an increased risk of shock or electrocution (due to exposed components). Open frame supplies generally run a smaller footprint than enclosed power supplies.
Connectors / Plug types for wall adapters
Barrel Connector – commonly used with a wall mounted AC-DC converter for items like laptop computers and printers
IEC 320-C14 – commonly used with computer monitors or self-power speakers
IEC 320-C8 (figure-8) – commonly used in office equipment and printers
NEMA 1-15P (Type A) – common outlet type found in the United States
CEE 7/16 or Type C (Europlug) – common outlet found in Europe
Universal Serial Bus (USB) – commonly found on computers
Board Mount Power Supplies
Board mount power supplies, are intended to be affixed to a Printed Circuit Board (PCB).
Power Bricks
Learn more about power supply bricks
Thermal Management in Power
Any machine, circuit, switching device, or power converter is less than 100% efficient. This is due to energy loss, which can come from many factors: the slight resistance found in a conductor, switching losses, and even in mechanical vibrations between parts. This energy loss is typically converted into forms that are unable to do useful work: vibrations, sounds, and heat.
As heat from power loss is generated it must be dealt with by the designer or the whole device could experience shorten life span, out of specification performance, or in the worse case it could be a danger to users. Luckily, there are several methods for dealing with waste heat generated by power devices.
Fans
Just like personal fans found in your living space can help keep areas cool by moving air, electronic devices can have fans as well to move air into or out of an enclosure. By either drawing external air into the enclosure or by exhausting heated air from inside, fans allow a large degree of flexibility when designing heat flow and management.
Source: DigiKey
| Pros | Cons |
|---|---|
| Small and compact form factors | Moving parts - has the likelihood to be the first part in a system to fail |
| Can specify air flow | Can require separate power circuits, and increase cost |
| Fan speed can be regulated based on a feedback loop | Can include more complex feedback loops |
Heat Sinks
Heat sinks are a completely passive device that allows for the transfer of heat away from a source into the surrounding environment. Typically, heat sinks are found in direct contact with high power devices such as CPUs, or power bricks that need to be cooled directly.
Source: DigiKey
| Pros | Cons |
|---|---|
| No moving parts, and does not break easily | Heavy and large |
| Can be paired with fans to improve heat transfer | Effectiveness dependent on surrounding temperature |
| Variety of shape, size, and package type | Calculating effective sizing may require more complex math |
Thermal Interface Materials (TIM)
Thermal Interface Materials also known as TIMs, are materials or substance that can be placed between two larger components to improve the thermal transfer between them, such as a power supply and an external heat sink. TIMs are typically either a thin sheet of material or spreadable paste which can be applied or spread over the device to help increase the thermal conductivity between two items.
Source: DigiKey
| Pros | Cons |
|---|---|
| For sheets: solid material sheets can be cut to size and shape | Can be expensive |
| For dispensable: able to be spread and apply onto nearly any surface | Typically has a shelf life or use by date |
| Greatly improve thermal conductively by removing air gaps between dissimilar materials | Most do not provide mechanical strength or connections without adhesives |
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