Details
During electric energy conversion, power devices, transformers, resistors, diodes and other electronic components inside power supplies continuously generate heat loss. If accumulated heat cannot be dissipated timely within the unit, component temperature will exceed rated limits, accelerating the aging of capacitors, breakdown of power transistors and failure of insulating layers. This drastically shortens the service life of power supplies, and in severe cases, directly triggers short circuits, fire hazards and other safety risks.
Based on heat transfer media, physical heat exchange principles and structural design, mainstream heat dissipation solutions for power supplies are categorized into four types: natural air cooling, forced air cooling, pure conduction cooling and liquid cooling. Multiple composite heat dissipation schemes are derived accordingly. Each method differs greatly in applicable power ranges, application scenarios and environmental adaptability. A detailed elaboration is provided as follows.
1. Natural Air Cooling
Natural air cooling is the simplest passive heat dissipation solution with the longest application history. It operates without moving parts such as fans or water pumps, and completes heat exchange relying on two fundamental physical mechanisms: thermal radiation and natural air convection. Heat-generating components including MOSFETs and rectifier bridges are attached to aluminum or copper heat sinks via solid conduction. The surface temperature of heat sinks is higher than ambient air, which causes hot air to rise naturally while cold air flows in through gaps at the bottom and side walls of the unit, forming unpowered circulating airflow to carry away heat. Meanwhile, the heat sink surface dissipates heat to surrounding space via infrared radiation.
Advantages
Natural air-cooled power supplies contain no moving mechanical parts, delivering zero operational noise. They eliminate failures caused by fan dust accumulation, bearing wear and wire disconnection, ensuring extremely high long-term operational stability and maintenance-free performance. The peripheral control circuit is simplified without temperature-controlled speed regulation circuits, cutting manufacturing costs significantly. Structural sealing modification can be implemented easily; equipped with sealing rubber rings on enclosures, the power supply can reach IP54 or IP67 dustproof and waterproof ratings, suitable for harsh working conditions with dust, humidity and mild corrosive substances.
Disadvantages
This solution suffers from extremely low heat dissipation efficiency, whose capacity fully depends on the surface area of heat sinks and ambient ventilation conditions. It is only compatible with low-power power supplies with low loss, generally ranging from 1W to 200W, such as mobile phone chargers, small monitoring adapters, weak-current switching power supplies for corridor facilities and built-in power supplies for miniature instruments. When deployed in sealed cabinets, high-temperature workshops or non-ventilated enclosures, trapped heat cannot circulate freely, forcing the power supply to derate by 30% to 50% of rated output power; otherwise, overheat protection shutdown will occur instantly. To improve heat dissipation performance, manufacturers often enlarge heat sink dimensions and increase fin density, which directly expands the overall size and weight of power supplies and fails to meet miniaturization and lightweight design requirements of terminal equipment.
2. Forced Air Cooling
Forced air cooling represents the most widely adopted active heat dissipation solution for industrial power supplies, high-power switching power supplies, server power supplies and charging pile power supplies. Its core assembly consists of metallic heat sinks, cooling fans and temperature control circuits. Heat-generating components are tightly bonded to heat sinks via thermal grease and thermal pads to transfer heat rapidly to fins. Cooling fans actively draw in cold ambient air and force airflow through dense fin gaps to remove accumulated heat on heat sinks at high velocity, with hot air exhausted through outlets at the rear of power supplies. The convective heat exchange efficiency reaches 3 to 8 times that of natural air cooling.
Classified by fan control logic, forced air cooling is divided into constant-speed fan cooling and temperature-controlled variable-speed fan cooling.
Constant-speed fan cooling features minimal circuit design: fans run at full speed whenever the power supply is energized to maintain constant heat dissipation capacity with low cost, widely applied in entry-level high-power power supplies. Nevertheless, fans operate at maximum rotational speed regardless of load level and ambient temperature, generating harsh noise under no-load or low-temperature conditions and accelerating continuous bearing wear to shorten overall service life.
Temperature-controlled variable-speed fans integrate NTC thermistor temperature measurement circuits to collect real-time internal temperature data of power supplies. Fans rotate at low speed under low temperature and light load to reduce noise, and gradually boost rotational speed once temperature exceeds threshold values, running at full capacity under full load and high temperature. This design balances heat dissipation performance, noise level and fan service life, serving as the standard configuration for mid-to-high-end industrial power supplies.
Forced air cooling covers power ranges from 200W to 10kW, applicable to industrial control equipment, CNC machine tools, communication base stations and high-power LED drive power supplies. Its primary drawbacks lie in the fan as a consumable component: long-term operation leads to blocked air ducts from dust accumulation, abnormal bearing noise and aged broken fan blades. Regular air duct cleaning is mandatory for heavily dusty industrial sites. Air intake and exhaust openings must be reserved on the enclosure, making high-level sealing impossible with poor waterproof and dustproof performance; such units cannot be directly deployed in outdoor rainy or heavily dusty environments. Continuous fan operation generates persistent noise, rendering it unsuitable for laboratories, household medical equipment and other scenarios with strict mute requirements. At present, most manufacturers adopt optimized composite design by adding copper heat-conducting sheets at the bottom of heat sinks to assist heat conduction and raise the upper limit of air cooling capacity.
3. Pure Conduction Cooling (Enclosure Thermal Conduction Cooling)
Also known as sealed duct-free thermal conduction cooling, pure conduction cooling takes solid metal as the core heat transfer medium with negligible reliance on air convection, specially developed for fully sealed dustproof and waterproof power supplies. It is widely adopted in outdoor security power supplies, street lamp drivers, sealed vehicle-mounted power supplies and underground explosion-proof power supplies. The design eliminates exposed heat sink fins and ventilation slits; heat-generating power components are closely fitted to the aluminum alloy metal enclosure of power supplies through high-thermal-conductivity thermal pads and copper studs. Heat generated by components is directly conducted to the entire enclosure, which exchanges heat slowly with external ambient air via its large surface area. Some products are equipped with flat external cooling ribs on enclosures to expand thermal contact area.
Core Advantages
The entire unit can be fully sealed without ventilation gaps, easily achieving IP65 to IP68 dustproof and waterproof grades for long-term operation under open-air rain exposure, immersion and heavily dusty chemical workshops. Zero fan design delivers noise-free operation without vulnerable moving parts for maintenance-free service. Explosion-proof reconstruction can be completed with ease, complying with safety specifications for mining, oil and gas hazardous areas. Internal airflow circulation is eliminated, preventing dust and moisture from entering the cavity and drastically reducing failure rates of circuit board corrosion and short circuits.
Heat dissipation efficiency of conduction cooling falls between natural air cooling and forced air cooling, heavily restricted by enclosure material, shell thickness and contact surface with installation equipment. If the power supply is attached to plastic cabinets or heat-insulated walls, heat cannot be conducted outward smoothly and severe heat accumulation occurs. Applicable power ranges are mostly from 5W to 500W. High-power conduction-type power supplies require thickened aluminum alloy enclosures and auxiliary heat conduction through external equipment metal racks. During installation, tight fitting between the enclosure and metal cabinet is mandatory with thermal silicone pads added to lower contact thermal resistance. Its main disadvantage is the remarkably high surface temperature of enclosures, posing scald risks for operators; derated operation is also required under high ambient temperature conditions.
4. Liquid Cooling
Liquid cooling stands as the high-end heat dissipation solution with top-tier efficiency, adopting water, ethylene glycol coolant and insulating fluorinated liquid as heat transfer media to remove heat via liquid circulation. It is subdivided into water cooling and immersion liquid cooling, exclusively applied to ultra-high-power power supplies above kilowatt level, such as energy storage converters, high-power photovoltaic inverters, high-frequency welding power supplies, power supply modules for large server clusters and traction power supplies for rail transit.
Water Cooling
The water cooling system consists of cold plates, circulating water pumps, heat transfer pipelines, external cooling radiators and auxiliary cooling fans. Heat-generating power transistors inside power supplies are fixed on cold plates; coolant flows through microchannels within cold plates to absorb heat from components rapidly. Heated liquid is delivered to external radiators via pipelines and cooled down by auxiliary fans, with chilled liquid circulating back to sustain continuous heat exchange. The thermal conductivity of liquid far surpasses air, enabling liquid cooling to deliver over 10 times the heat dissipation capacity of forced air cooling under equivalent volume. Component temperature rise is strictly controlled to allow long-term full-load operation of power supplies with greatly elevated power density and reduced overall equipment dimensions.
Immersion Liquid Cooling
The entire power supply unit is fully immersed in insulating coolant, with all components in direct contact with liquid to absorb heat uniformly across all surfaces without local hotspots, featuring outstanding heat balance performance. It is mainly deployed in supercomputers and power supply cabins of large energy storage power stations.
Despite premium heat dissipation performance, liquid cooling bears prominent defects: the complete system features complex structure including water pumps, pipelines, sealing joints and liquid replenishing devices, with hardware costs several times higher than conventional air-cooled power supplies. Leakage risks exist as aging pipelines and loose joints may trigger liquid seepage to corrode circuit boards. Periodic coolant replacement and pump maintenance are required, leading to high post-operation costs. Large overall system dimensions demand abundant installation space, making liquid cooling completely unfeasible for small and medium-sized power supplies.
5. Composite Heat Dissipation Schemes
Single heat dissipation methods rarely satisfy multiple simultaneous demands including high power output, high protection rating, low noise and wide temperature range. Most mid-to-high-end industrial power supplies on the market adopt composite heat dissipation design integrating two or more solutions, which represents the mainstream optimization direction of the industry at present:
Conduction + Forced Air Cooling: Internal components conduct heat to metallic heat sinks with temperature-controlled fans for active air blowing, balancing high-power heat dissipation and basic dust resistance, widely adopted for 1kW to 5kW industrial control power supplies.
Enclosure Conduction + Natural Air Cooling: External cooling ribs on sealed waterproof enclosures cooperate with natural air convection, serving as the standard configuration for outdoor street lamp and monitoring power supplies.
Liquid Cooling + Air Cooling: Internal cold plates conduct heat for high-power energy storage power supplies, with external radiators equipped with auxiliary fans to balance heat dissipation efficiency and system volume.
Graphite Film Heat Equalization + Conduction Cooling: High-thermal-conductivity graphite films are installed inside ultra-thin compact power supplies to equalize circuit board temperature, eliminate local hotspots and assist enclosure heat conduction.
Distinct heat dissipation methods possess clear applicable boundaries: natural air cooling or pure conduction cooling is prioritized for low-power, mute and sealed scenarios; temperature-controlled forced air cooling is the primary option for medium-and-high-power indoor equipment; enclosure conduction cooling is adopted for outdoor waterproof and explosion-proof equipment; liquid cooling is selected for ultra-high-power, high-power-density large energy storage and industrial conversion equipment; composite combined heat dissipation schemes are deployed for working conditions with diversified requirements.
During power supply design and model selection, output power, ambient operating temperature, protection grade, noise limitation and maintenance conditions shall be comprehensively evaluated to match appropriate heat dissipation structures. This can control manufacturing costs while guaranteeing long-term stable operation of power supplies and avoiding equipment shutdown and safety accidents caused by overheat damage.
