In industrial automation equipment, the energy loss of a typical switching power supply can reach 10%-15% of the total input power. However, precisely designed DC-DC converters can reduce this figure to only 2%-3%, converting more electrical energy into useful work.
01 Switching Loss: The Invisible "Assassin"
Switching loss is one of the main sources of efficiency loss in DC-DC converters. Every time the power switch transistor turns on or off, it undergoes a transition process where voltage and current overlap.
The switch transistor takes time to switch from "off" to "on," and during this time, the voltage decreases while the current increases. The power loss generated during this transition is called switching loss.
Switching frequency is a key parameter affecting switching loss. As the switching frequency increases from 100kHz to 1MHz, the switching loss can increase by 3-5 times. Although high frequency allows the use of smaller magnetic components and capacitors, reducing the size of the converter, it also directly increases switching loss.
Modern DC-DC converters use soft switching technology to significantly reduce this loss. This technology arranges the switching transistors to switch when the voltage or current is zero, theoretically reducing switching loss to zero. Resonant converters and quasi-resonant converters are designed based on this principle.
02 Conduction Loss: Energy "Toll Booths" on the Current Path
Conduction loss is the loss generated by the resistance of the components within the converter as current flows through them. Unlike switching loss, conduction loss exists in almost every stage of energy conversion.
Power switch transistors (such as MOSFETs) have on-resistance in the conducting state, which is the main source of conduction loss. For low-voltage, high-current applications, even a small on-resistance can lead to significant power loss.
In addition, the DC resistance and skin effect of magnetic components (inductors and transformers) also generate losses. The resistance of PCB traces and the contact resistance of connectors are also components of conduction loss.
Effective methods to reduce conduction loss include selecting power switch transistors with low on-resistance, using multi-strand twisted wire to wind inductors to reduce the skin effect, and designing wider PCB traces to reduce line resistance.
03 Drive Loss and Static Loss: Energy Consumption of the Control Circuit
Drive loss refers to the energy required to drive the power switching transistors, which is ultimately converted into heat. Each change in switching state requires charging and discharging the gate capacitance of the power switching transistor.
Gate charge is a key parameter affecting drive loss. The larger the gate charge, the higher the drive loss. The gate drive voltage also affects drive loss; higher drive voltages typically lead to greater drive loss.
Static loss refers to the energy consumed by the converter's control circuit itself, including the energy consumed by all circuit components that do not directly participate in power conversion, such as the reference voltage source, error amplifier, and protection circuits.
This loss is particularly noticeable under light load or no-load conditions. Modern DC-DC converters use intermittent operation or burst mode to reduce static loss at light loads, reducing energy consumption by periodically shutting down parts of the control circuit.
04 Magnetic Component Losses: Invisible Energy Dissipation
Magnetic component losses (inductors and transformers) mainly include core loss and winding loss. At high switching frequencies, these losses can account for a significant proportion of the total losses.
Core loss mainly consists of hysteresis loss and eddy current loss, which are directly affected by the core material, switching frequency, and magnetic flux swing. High-frequency applications typically choose ferrite or metal powder core materials to reduce core loss.
Winding loss includes DC resistance loss and high-frequency losses caused by the skin effect and proximity effect. The skin effect causes high-frequency current to flow mainly on the surface of the conductor, effectively reducing the conductor's cross-sectional area.
To reduce winding loss, high-frequency applications often use multi-strand twisted wire or flat copper foil as windings to increase the effective current flow area at high frequencies. Winding interleaving techniques in transformer design can also effectively reduce losses caused by the proximity effect.
05 Topology and Control Strategy: System-Level Efficiency Improvement
The converter topology is a systemic factor affecting efficiency. Different topologies are suitable for different input and output voltage ranges and power levels. Common topologies include buck, boost, flyback, forward, push-pull, half-bridge, and full-bridge. Buck converters are most efficient when the input and output voltage ratio is close, while flyback converters are suitable for isolated and multi-output applications.
Synchronous rectification technology replaces traditional rectifier diodes with low on-resistance MOSFETs, significantly reducing the losses caused by the forward voltage drop of traditional diodes. This technology is particularly important for converters with low voltage and high current outputs.
Multiphase interleaved parallel technology connects multiple converter units in parallel and operates them out of phase. This not only distributes the current and reduces the stress on individual power switching transistors but also significantly reduces input and output current ripple.
Particularly impressive is this technology’s performance in high-current applications: it “flattens” the efficiency curve, sustaining high efficiency across a wide load range. When the load fluctuates between 30% and 80%, the efficiency drop usually does not exceed 2 percentage points.
In summary, by optimizing switching technology, reducing conduction and magnetic component losses, improving driving and control strategies, and combining these with efficient topological structures, modern DC-DC converters can significantly reduce energy losses to 2%–3%. This further improves the energy efficiency of industrial automation equipment.
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