Introduction
A switch mode power supply (SMPS) is a type of power conversion device commonly used in electronic circuits to efficiently convert electrical energy from one form to another. Unlike traditional linear power supplies, which use bulky transformers and linear regulators, SMPSs employ high-frequency switching techniques to achieve higher efficiency and smaller size.
The fundamental principle of an SMPS involves rapidly switching an input voltage on and off using a transistor or semiconductor switch. This switching action allows the SMPS to regulate the output voltage by controlling the duty cycle of the switch.
By rapidly switching the voltage, an SMPS can effectively step up or step down the input voltage to the desired output level, making it highly versatile for various applications.
Switch mode power supplies offer several advantages, including higher efficiency, reduced weight and size, and better voltage regulation. They are commonly found in a wide range of electronic devices, including computers, televisions, smartphones, and industrial equipment. The efficiency and compact design of SMPSs make them a popular choice for powering electronic devices efficiently while minimizing energy waste.
A
Ambient Operating Humidity
Ambient Operating Humidity specifies the ideal relative humidity range for Switch Mode Power Supplies (SMPS) to operate efficiently. Ensuring no performance degradation or risks. It is typically expressed as a percentage.
The components within an SMPS are sensitive to moisture. High humidity can lead to condensation, causing short circuits or corrosion. Conversely, low humidity can increase the risk of static electricity, which can also damage the components. Hence, maintaining the device within the specified humidity range helps ensure its reliability, safety, and lifespan.
Ambient Operating Temperature
Ambient Operating Temperature denotes the temperature range in Celsius (°C). Where a Switch Mode Power Supply (SMPS) can operate safely and efficiently. This temperature range ensures the components within the SMPS won’t overheat or underperform due to environmental conditions.
High temperatures can lead to overheating and potential damage, while extremely low temperatures can affect the optimal performance of certain components. Therefore, understanding the ambient operating temperature is crucial when installing the SMPS to ensure reliable, efficient operation, and long lifespan.
B
Boost Converter
A Boost Converter is a DC-to-DC power converter that steps up, or increases. the input voltage from its power source while simultaneously reducing the current. This is particularly useful when the load requires a higher voltage than the source provides.
In a typical boost converter, energy is stored in an inductor during one part of the switching cycle. Then transferred to the load during another part, effectively increasing the output voltage. By controlling the duty cycle of the switching frequency, the boost converter. can manage how much energy is transferred, effectively controlling the output voltage.
Buck Converter
A Buck Converter is a DC-to-DC power converter that steps down, or reduces, the input voltage. While increasing the current from its power source to its output load. This is useful when the load requires a lower voltage than the source provides.
Buck converters use a transistor and a diode in conjunction with an inductor and a capacitor to control the conversion process. The duty cycle of the transistor’s switching frequency helps control the output voltage.
Buck-Boost Converter
A Buck-Boost Converter adjusts input voltage by stepping up or stepping down in DC-to-DC power conversion. Making it versatile in a variety of applications. In essence, it’s a combination of a buck converter and a boost converter.
In ‘buck’ mode, it reduces the input voltage, and in ‘boost’ mode, it increases it. The mode of operation is usually controlled automatically based on the difference between the input voltage and the desired output voltage. This is particularly useful in battery-operated systems, where the battery voltage can vary significantly during its discharge cycle.
C
Conducted Emission
Conducted Emissions are a form of electro magnetic interference (EMI) that travel along power lines and inter connecting cables. In the context of an SMPS, conducted emissions are unwanted electrical signals generated by the device itself. Which can propagate out to other devices through power cords, data cables, etc., potentially causing performance issues or even damage.
Regulatory standards, such as those by the Federal Communications Commission (FCC) and the International Electro technical Commission (IEC). Limit the levels of conducted emissions that electronic devices, including power supplies, are allowed to generate.
Cooling Method (Convection/Forced Air/Fan)
In an SMPS, heat is generated as a byproduct of its operation. The cooling method refers to how this heat is dissipated to prevent overheating and ensure reliable operation. Convection cooling is a passive method that relies on natural air circulation.
Forced air cooling uses fans or blowers to move air over components, providing better cooling than natural convection alone. The choice of cooling method depends on factors like the power supply’s design, power level, and the intended application’s ambient conditions.
Current (Input)
Input Current is the amount of electric current that an SMPS draws from its power source during operation. It’s typically measured in amps (A). The input current requirement for an SMPS depends on its design and efficiency. The power it needs to deliver to its load.
The high input current can lead to increased heat generation and may require special considerations for wiring and safety. Understanding the input current requirement is important for designing and implementing safe and efficient power systems.
D
DC Input
DC Input refers to the Direct Current voltage that a Switch Mode Power Supply (SMPS) takes in from its power source. The SMPS Power Supplies then converts this DC input into a different voltage level, according to the requirements of the device it powers.
The DC input is specified in volts (V) and can come from various sources like batteries or other power supplies. Understanding the DC input requirement is crucial to ensure compatibility with the power source.
Degree of Protection
The Degree of Protection refers to the SMPS’s resistance to foreign objects (like dust) and water. Usually represented by an IP (Ingress Protection) code, such as IP20, the first digit signifies protection against solids and liquids. The higher the numbers, the better the protection. This information is essential when installing the SMPS in environments that may expose it to dust or water.
Dielectric Strength
Dielectric Strength is a measure of a material’s ability to withstand high voltage without breaking down or experiencing electrical discharge. In an SMPS, it refers to the maximum voltage that the insulation can withstand before it fails. This is a critical safety parameter that prevents short circuits or electric shocks. It’s typically measured in volts per unit of thickness.
Duty Cycle
In SMPS, Duty Cycle indicates the active portion of a full cycle, commonly expressed as a percentage. In the context of a switching power supply.
it signifies the duration in which a switching transistor is ON compared to the total time. Controlling the duty cycle is vital to regulate output voltage in switching power supplies and achieving desired levels.
E
Efficiency
Efficiency in a Switched Mode Power Supply (SMPS) represents the percentage of input power that is efficiently converted into output power.
Measuring the effectiveness of the power conversion process in minimizing energy losses. It is usually expressed as a percentage. The higher the efficiency, the less power is wasted as heat, making the SMPS more energy-saving and reliable.
Higher efficiency can also reduce the need for extensive cooling mechanisms. Factors like switching frequency, type of components used, and circuit design can influence the efficiency of an SMPS.
EMI (Electromagnetic Interference)
EMI is a phenomenon where electro magnetic waves from one electronic device interfere with the operation of another nearby device. In an SMPS, EMI can be produced during the rapid switching of the power semi conductors. EMI can be mitigated using techniques like proper shielding, grounding, and filtering. Regulatory standards limit the levels of EMI that electronic devices, including SMPSs, can generate.
EMS (Electromagnetic Susceptibility)
EMS is about electronic devices working properly in an electromagnetic environment without causing disruptive interference to other devices. In simpler terms, it’s about how well the device can handle external EMI without malfunctioning. Various tests are conducted to ensure an SMPS meets required EMS standards.
External Fuse
An external fuse in an SMPS safeguards the power supply and the connected system from overcurrent situations. The fuse in an SMPS blows if the current exceeds a limit, protecting the system from damage.
Select a user-replaceable external fuse for the power supply unit with appropriate ratings as per the manufacturer’s specifications.
F
Feedback Loop
The feedback loop in an SMPS maintains the output voltage or current at the desired level. The feedback loop in an SMPS senses the output parameter, compares it with a reference value. And adjusts the control signal to the power switch accordingly.
The feedback loop in an SMPS corrects deviations from the desired value caused by load or input changes. This ensures a stable and accurate output from the SMPS.
Flyback Converter
A flyback converter is a type of SMPS topology that is often used for low to medium power applications. It operates by storing energy from the input in a magnetic field during the first half of the switching cycle. And then transferring this energy to the output during the second half of the cycle (when the switch is OFF).
Flyback converters are popular due to their simplicity and the ability to provide multiple output voltages with isolation from the input.
Forward Converter
A forward converter is another SMPS topology used for medium to high power applications. Forward converters transfer energy directly to the output without storing it, unlike flyback converters.
This results in better efficiency, especially at high power levels. Forward converters are more complex due to the additional reset winding and freewheeling diode required in the circuit.
Frequency
In the context of an SMPS, frequency often refers to the switching frequency of the power switch or transistor. This is the rate at which the power switch turns on and off during the operation of the power supply.
The switching frequency in an SMPS determines transformer size, filter requirements, and impacts efficiency. Higher frequencies typically allow for smaller components but may lead to increased losses and thus lower efficiency.
Full-Bridge Converter
A full-bridge converter is a type of SMPS topology often used in high power applications, typically above 500W. The name “full-bridge” comes from the configuration of four transistors in a “bridge” formation on the input side.
This converter achieves higher efficiency by reversing current flow through the transformer primary, optimizing magnetic core utilization. However, full-bridge converters are relatively complex and require sophisticated control techniques to ensure proper operation and performance.
H
Half-Bridge Converter
A half-bridge converter is a type of SMPS topology that is commonly used in medium to high power applications. It is named so because it uses two switches on the input side, creating a ‘half-bridge’. These switches operate alternately to produce a bipolar voltage across the transformer primary, thereby driving current through it in both directions.
Half-bridge converters are efficient but demand complex control and balanced voltage division at the input.
Harmonic Current Emissions
Harmonic current emissions are multiples of the power system’s fundamental frequency (50 or 60 Hz). In an SMPS, harmonic current emissions result from non-linear characteristics and rapid switching of power semiconductors.
Excessive harmonic current can lead to issues like device interference, increased power line losses, and voltage waveform distortion. Therefore, there are regulatory standards, like EN61000-3-2, that limit the allowable harmonic current emissions from electronic devices.
Hold Time
In an SMPS, hold time is the minimum duration that the power supply can maintain its output within specifications after an input power loss or interruption. It’s measured in milliseconds (ms) and is a critical parameter in scenarios where reliable power supply is crucial.
Hold time in an SMPS is influenced by factors like output capacitor energy storage capacity and load current.
I
Input Variation Influence
Input variation influence refers to how input power supply variations affect SMPS output parameters. These variations can be due to changes in the input voltage or frequency.
Typically, a well-designed SMPS has mechanisms to cope with these changes and maintain a stable output. It is usually expressed as a percentage change in the output voltage or current for a specified range of input variation. A lower value indicates better regulation of the power supply.
Input Voltage
The input voltage of an SMPS is the power source voltage that is converted into a regulated output voltage. SMPS input voltage can come from mains supply (110VAC or 220VAC) or a DC source.
SMPS are often designed to operate over a wide range of input voltages. The actual input voltage range that an SMPS can handle is specified by the manufacturer.
Inrush Current
Inrush current is the peak, instantaneous input current drawn by an electrical device at the initial turn-on. For an SMPS, this can be significantly larger than the normal operating current, due to the charging of the input capacitors.
Inrush current, which can cause component damage, is often limited using measures like inrush current limiters (ICLs) or soft-start circuits. The typical inrush current value for an SMPS is provided in its technical specification.
Insulation Resistance
Insulation resistance measures how well an electrical component, like a wire or cable, can prevent current flow. Higher insulation resistance means better insulation quality and less risk of current leakage. It’s important for safety and assessing insulation integrity.
Internal Fuse
An internal fuse is a safety device built into an electrical or electronic component. It protects against excessive current or short circuits by breaking the circuit when a fault occurs. It prevents damage and fire hazards.
Once blown, the fuse is non-replaceable, so the component may need replacement. Internal fuses ensure the safety of electrical systems by limiting current flow and safeguarding valuable components.
L
Leakage Current
Leakage current is the small electric current that flows through insulation or component surfaces when they should be in an off state. It can occur due to imperfections in the insulation or unintended pathways for current to flow.
Leakage current, measured in µA, is critical to manage in sensitive electronics and medical devices to avoid malfunctions and electrical shock hazards.
Line Regulation
Line regulation is a measure of how well a power supply maintains its output voltage when the input voltage fluctuates.
Output voltage regulation measures the power supply’s ability to maintain a stable output voltage despite variations in the input voltage.
A power supply with good line regulation will deliver a stable output voltage even when the input voltage varies. Line regulation, expressed in percentage or millivolts (mV), ensures consistent and reliable performance of electronic devices.
Load Regulation
Load regulation measures the ability of a power supply to maintain a stable output voltage despite changes in the load current. It quantifies how well the power supply can respond to varying load conditions without significant voltage fluctuations.
Load regulation, in percentage or millivolts (mV), is crucial to consider in applications with varying load currents. A power supply with good load regulation will provide a consistent and stable output voltage regardless of changes in the load.
Load Variation Influence
Load variation influence refers to how changes in the electrical load connected to a device or system affect its performance. Different devices or systems may exhibit varying responses when the load changes.
Some devices may experience changes in voltage, frequency, or other parameters, affecting their operation or accuracy. Consider load variation influence to ensure equipment can handle expected load changes and maintain desired performance.
Load/No-Load Operation
Load/no-load operation refers to the behavior of a device or system under different load conditions. Load operation: device with load. No-load operation: device without load.
Some devices may behave differently in terms of energy consumption, efficiency, or stability when operating with or without a load. Understanding load/no-load operation characteristics is vital for energy optimization, functionality, and avoiding power inefficiencies.
M
Mean Time Between Failures (MTBF)
Mean Time Between Failures (MTBF) is a measure used to estimate the reliability of a device or system. It represents the average time elapsed between one failure and the next. MTBF is typically expressed in hours and is used to assess the expected longevity and reliability of a product. A higher MTBF value indicates a longer expected time before the occurrence of failures, implying greater reliability.
MTBF is an important consideration in industries where reliability and uptime are critical, such as manufacturing, telecommunications, and aerospace. Load/no-load operation understanding supports maintenance scheduling, failure prediction, and informed reliability decisions. MTBF does not guarantee precise device lifespan, as failures can occur randomly due to various factors.
N
Noise
Noise refers to undesired electrical signals or disturbances that can disrupt the proper functioning of electronic devices or systems. It can manifest as random fluctuations, electrical interference, or unwanted signals introduced into a circuit or transmission.
Noise can cause errors, distortions, or disruptions in signal quality, affecting the performance or accuracy of electronic devices. Noise can be reduced through techniques like shielding, filtering, grounding, and careful circuit design for reliable operation.
O
Output Indicator
An output indicator shows the status of a device or system’s output. It can be visual or audible, informing the user if it’s active, inactive, within range, or abnormal.
Output indicators come in different forms like LEDs, digital displays, alarms, or status indicators, depending on the application.
Output Voltage
Output voltage is the electrical potential difference or level of the signal/power from a device or system’s output. It represents the voltage magnitude of the electrical signal generated or provided by the device.
The output voltage can be steady and fixed, or it may vary depending on the device’s functionality. Output voltage is crucial for compatibility and proper operation when connecting devices together. Output voltage is typically measured in volts (V) and is specified by the device manufacturer or system designer.
Overload Protection
Overload protection prevents damage to devices/systems from excessive current or power. It works by automatically interrupting or limiting the flow of current when the load exceeds the specified limit. This can occur due to short circuits, excessive current draw, or other abnormal conditions.
Overload protection mechanisms can include fuses, circuit breakers, or protective devices that sense the current and react accordingly. Overload protection safeguards equipment, prevents overheating, and reduces the risk of fires or damage.
Overvoltage Protection
Overvoltage protection prevents excessive voltage levels in electrical devices or systems. It ensures that excessive voltage surges or spikes do not damage or disrupt the operation of sensitive electronics.
Overvoltage protection devices like surge protectors detect and divert excessive voltage. Overvoltage guard against voltage transients caused by lightning or power surges. Overvoltage protection safeguards devices, preventing damage and ensuring reliable operation.
P
Parallel Operation
Parallel operation connects multiple devices/components to perform a shared function or increase capacity. It involves linking generators, power supplies, or inverters to combine outputs or boost power capacity.
Parallel operation allows for redundancy, improved reliability, and increased load-sharing among the connected devices. It enables the system to handle higher power demands, provide backup support, or distribute the load evenly across multiple sources.
Power Factor
Power factor is a measure of how effectively electrical power is being utilized in a system. It represents the ratio of real power (measured in watts) to apparent power (measured in volt-amperes). A high power factor means efficient power usage, while a low power factor indicates inefficiency or reactive power consumption.
Power factor is affected by the loads connected, especially those with inductive or capacitive characteristics. Power factor correction techniques can optimize power usage by minimizing reactive power.
Power Good Signal
The power good signal confirms stable power delivery from the PSU to components. It indicates that the output voltage has stabilized within acceptable limits after startup or power disruptions.
It is typically a digital signal that transitions from low to high once the power supply reaches the appropriate voltage levels. The power good signal ensures system stability and enables components to function properly and avoid damage caused by inadequate power supply.
Power Ratings
Power ratings refer to the specifications that indicate the maximum power capacity or output capability of an electrical or electronic device. It represents the amount of power the device can handle or deliver without exceeding its design limits.
Power ratings are typically given in watts (W) and are essential for ensuring safe and reliable operation of the device. It helps users determine if the device is suitable for their power requirements and prevents overloading or damaging the device.
Pulse Frequency Modulation (PFM)
Pulse Frequency Modulation is a modulation technique used in electronic systems to vary the frequency of pulses in a signal. It involves changing the frequency of pulses while keeping the pulse width constant.
PFM is commonly used in applications such as power supplies and switching regulators to control the output voltage or current. By adjusting the pulse frequency, PFM allows for efficient power conversion and regulation, minimizing energy losses and improving overall system performance.
Pulse Width Modulation (PWM)
Pulse Width Modulation is a modulation technique that involves varying the width of pulses in a signal. It is commonly used to control the power or speed of devices such as motors, LEDs, or audio amplifiers.
By adjusting the width of the pulses, PWM can effectively regulate the average power or intensity of the output. It achieves this by rapidly switching the output between fully on and fully off states. It creating a square wave with varying duty cycle. PWM offers precise control over power delivery, allowing for smooth and accurate adjustment of device operation.
R
Radiated Emission
Radiated emission refers to the unintentional electromagnetic energy or signals that are emitted or radiated from an electronic device or system. These emissions can interfere with the operation of other nearby electronic devices or cause electromagnetic interference (EMI) in the surrounding environment.
Devices are tested for radiated emissions and may need shielding or filtering to comply with regulations and minimize interference.
Rated Output Current
Rated output current is the maximum safe current a power supply/device can deliver under normal conditions.
It ensures that the device can handle the load’s current requirements without damage or exceeding its capacity. Considering the rated output current is crucial for selecting a compatible power supply/device and preventing overloading.
Rated Output Voltage
Rated output voltage is the specified voltage a power supply/device delivers under normal conditions.
It should match load requirements for compatibility and safe operation. Using a different output voltage can lead to improper functioning or device damage.
Remote On/Off
Remote On/Off enables power supplies/devices to be remotely turned on or off.
It allows control of the power state from a distance, which is beneficial when manual access is limited or inconvenient.
Remote Sensing
Remote sensing is a technique used in power supplies to compensate for voltage drop across long output cables. Voltage is measured at the load and adjusted to maintain the desired voltage.
This compensates for losses and variations caused by cable resistance, ensuring accurate and stable voltage delivery.
Ripple & Noise
Ripple and noise refer to unwanted fluctuations or disturbances in the output voltage of a power supply. Ripple represents low-frequency variations, typically at the power line frequency or its harmonics. While noise refers to high-frequency disturbances caused by switching components or external electromagnetic interference.
Minimizing ripple and noise is important in sensitive electronic applications to ensure stable and clean power supply. It preventing potential malfunctions or interference with the proper operation of electronic circuits.
Ripple at 20 MHz
Ripple at 20 MHz measures voltage fluctuations at a frequency of 20 MHz. It’s important for circuits with high-frequency signals or sensitive components.
This ripple can affect circuit performance and reliability. Specifying it reveals the power supply’s ability to deliver clean power and reduce interference at higher frequencies.
S
Safety Standards
Safety standards are a set of guidelines and regulations established to ensure the safety and reliability of products and systems.
Standards establish minimum requirements for product design, construction, and performance to mitigate hazards and risks.
Compliance with safety standards is important to protect users, prevent accidents, and ensure product quality and reliability.
Series Operation
Series operation refers to connecting multiple components or devices in a series circuit configuration. In this configuration, the components are connected one after another, forming a continuous path for current flow.
In series operation, each component carries the same current and the total voltage is the sum of individual voltages. It’s used when components share current or when the desired output is the sum of individual component outputs.
Shock Resistance
Shock resistance refers to the ability of a device or material to withstand mechanical shocks or impacts without damage or malfunction. In the context of electronic components or devices, such as limit switches or power supplies, shock resistance ensures. That the device can withstand vibrations, jolts, or impacts that may occur during transportation, installation, or normal operation. Robust construction, secure mounting, and shock-absorbing mechanisms enhance shock resistance for reliable operation in demanding environments.
Soft Start
Soft start is a feature implemented in electronic devices to gradually increase the power or voltage during the device’s startup. It helps to prevent sudden surges or spikes in current, which can put stress on the device and the connected circuitry. By gradually ramping up the power, soft start reduces the impact on components and improves overall system stability.
Start-Up Time
Start-up time is the duration from off/standby to fully operational state, including power-on, component initialization, signal stabilization, and readiness for normal operation.
Start-up time varies based on device complexity and design. It’s crucial for applications requiring fast start or where delays affect system performance.
Storage Temperature
Storage temperature is the safe temperature range for storing electronic devices without impacting functionality or causing damage. It specifies the minimum and maximum temperature limits for storage, beyond which the device may experience degradation, reduced lifespan, or failure.
Adhering to the specified storage temperature range is essential to maintain the device’s performance and reliability over time. Particularly during periods when it is not in use or during transportation or storage before installation.
Switch Mode Power Supply
A switch mode power supply (SMPS) is an electronic circuit that efficiently converts electrical power from one form to another. It uses a high-frequency switching technique to regulate the output voltage or current. SMPSs are popular in devices like computers, TVs, and phone chargers for their compact size and high efficiency.
T
Temperature Variation Influence
Temperature variation influence refers to the effect of temperature changes on the performance and behaviour of electronic components or systems. Temperature can impact the electrical characteristics of components, such as resistance, capacitance, and conductivity, leading to variations in their behavior.
It is important to consider temperature effects during the design and operation of electronic devices to ensure reliable and accurate performance. Temperature control is crucial to prevent component damage and maintain optimal operation in the face of extreme temperature variations.
V
Vibration Resistance
Vibration resistance refers to the ability of a device or component to withstand and operate effectively in the presence of vibrations. Important in applications with mechanical vibrations, like industrial machinery or automotive systems.
A higher vibration resistance rating ensures that the device can endure vibrations without experiencing performance degradation or failure.
Voltage Adjustment Range
Voltage adjustment range specifies the range of voltages over which a device or component can be adjusted or varied. It allows users to customize the output voltage according to their specific requirements.
A wider voltage adjustment range offers flexibility and versatility in applications, allowing precise voltage tuning for different input conditions. This feature is commonly found in power supplies, voltage regulators, and other electronic devices where voltage control is necessary.
Conclusion
In conclusion, switch mode power supplies (SMPS) have revolutionized the field of power conversion in electronic devices. Their ability to efficiently convert electrical energy through high-frequency switching techniques offers numerous advantages over traditional linear power supplies.
SMPSs provide higher efficiency, which translates to reduced energy consumption and less heat dissipation. This makes them ideal for applications where power efficiency is critical, such as in portable electronic devices or energy-conscious industries. Additionally, their compact size and lightweight design make them well-suited for modern electronic devices that emphasize portability and sleekness.
The versatility of SMPSs allows for flexible voltage regulation, enabling them to adapt to different input and output voltage requirements. This adaptability makes SMPSs suitable for a wide range of applications, from small electronic gadgets to large-scale industrial systems.
Overall, switch mode power supplies have become an integral component in modern electronics, providing efficient, reliable, and compact power conversion solutions. Their continuous development and refinement contribute to the advancement of technology and the quest for more energy-efficient devices.