DC-DC modules are increasingly used in industries such as communication, industrial automation, power control, rail transportation, mining, and military. Modular design can effectively simplify customers’ circuit designs, improve system reliability, and maintenance efficiency. So, how can we enhance the reliability of power systems based on DC-DC modules? This article provides a brief analysis and discussion on this topic.

DC-DC isolated module power supplies are mainly used in distributed power systems to achieve isolation, reduce noise, voltage conversion, voltage stabilization, and protection functions.

Use Mature Power Topologies

For power module design, it’s best to choose mature power topologies. For instance, for 1W to 2W regulated input DC-DC power modules, the Royer circuit is preferred, while wide input series often select Flyback topology, and some use Forward topology.

High Efficiency Across Full Load Range

High efficiency means lower power loss and lower temperature rise, which can effectively improve reliability. In practical applications, power supplies are often designed with a certain degree of derating, especially today when the power consumption of load ICs is decreasing. Therefore, high efficiency across the full load range is a crucial parameter for the reliability of power systems, but it is often overlooked by power supply manufacturers. Many manufacturers aim to attract customers with high full-load efficiency in technical manuals but achieve lower efficiency under 5% to 50% load conditions.

Extreme Temperature Characteristics

The geographical areas where power modules are used can vary widely, from tropical heat to the severe cold of Russian winters. Therefore, the working temperature range for DC-DC modules must meet a minimum requirement of -40℃ to 85℃, with some achieving even better, such as Jinshengyang’s regulated R2 series 1W to 2W modules working at -40℃ to 105℃. For applications like automotive BMS and high-voltage bus monitoring, the working temperature must be -40℃ to 125℃, with Jinshengyang’s CF0505XT-1WR2 modules achieving a working temperature of up to 125℃.

Extreme temperature testing is the most effective method to verify the reliability of power modules, including high-temperature aging, high and low-temperature operational performance testing, high-low temperature cycling shock tests, and long-term high-temperature high-humidity testing. Regular power supply development will undergo the above tests. Therefore, whether such testing equipment is available is also a criterion for judging whether a power supply manufacturer is a counterfeit.

High Isolation, Low Isolation Capacitance

Medical products require extremely low leakage currents, while power electronic products need to minimize parasitic capacitance between the primary and secondary sides. These two industries share a common requirement for high isolation voltage and low isolation capacitance to reduce common-mode interference in systems. For applications in the medical or power electronics fields, it is advisable to select power modules with isolation capacitance below 10pF for 1W to 2W DC-DC, and below 150pF for wide voltage products.

EMC Characteristics

EMC performance is essential for the normal and safe operation of electronic systems. Currently, the electronic industry has high requirements for the EMC performance of products, and customers often complain about system resets and early failures due to poor EMC handling. Therefore, excellent EMC characteristics are a core competitive advantage of power modules.

Reliability of Power System Application Design

While the reliability of the power supply itself is important, due to the complexity of the working environment of power systems, even the most reliable power supply can fail without reliable system application design. Below are several common methods and considerations for power system application design.

Redundant Design Techniques

In high-reliability scenarios, the power module must ensure that the system does not lose power even if it fails. In such cases, a redundant power supply method can be employed to enhance system reliability. Figure 3 illustrates a common redundant design scheme. When one power module fails, another module can continue to supply power.

In the figure, D1 and D2 are recommended to use low-dropout Schottky diodes to avoid diode voltage drop affecting the downstream system’s operation. Additionally, the diode’s voltage rating must be higher than the output voltage. This method will generate additional ripple noise, requiring external capacitors to reduce ripple or add filtering circuits.

Derating Design

It is well known that derating design can effectively extend the working life of power supplies. However, when the load is too light, the power supply may not operate at its optimal state. For example, Jinshengyang DC-DC module power supplies are recommended to be used within a load range of 30% to 80%, where performance is best across all aspects.

Reasonable Peripheral Protection Design

Power module applications span many industries, and the environmental requirements vary widely. Due to their general-purpose design, DC-DC module power supplies can only meet common requirements. Therefore, when customers’ application environments are demanding, appropriate peripheral circuits must be added to enhance the reliability of the power supply.

Heat Dissipation Design

Approximately 15% of industrial-grade power module failures are due to poor heat dissipation. Power modules are evolving towards miniaturization and integration, but in many applications, power supplies operate continuously in enclosed environments. If heat cannot dissipate, internal components may fail due to excessive thermal stress. Common heat dissipation methods include natural air cooling, heat sinks, and enhanced forced air cooling fans. Below are some experience-sharing points for thermal design:

Convection Ventilation for Power Modules

For power modules relying on natural convection and thermal radiation for cooling, the surrounding environment must allow for good airflow, and there should be no large components blocking the airflow.

Placement of Heating Components

If the system has multiple heat sources, such as several power modules, they should be placed as far apart as possible to avoid thermal radiation transfer causing overheating.

Reasonable PCB Design

The PCB provides a means for heat dissipation, so it is essential to consider heat dissipation pathways during design. For instance, increasing the copper area of the main circuit and reducing component density on the PCB can improve the heat dissipation area and pathways. For example, power modules should be placed vertically to allow heat to dissipate quickly; if the DC-DC module is placed at the bottom of the PCB, the upward heat dissipation will be blocked by the PCB, causing heat buildup.

Larger Package Size and Heat Dissipation Area

For power supplies of the same power rating, if possible, choose larger package sizes and heat sinks with larger heat dissipation areas, or use thermal adhesive to connect the power module casing to the chassis. This way, the power module will have a larger heat dissipation area, dissipating heat faster, resulting in lower internal temperatures and naturally higher reliability.

Compatibility Design, Safety Regulation Design

Input wiring for the power supply should be kept as straight as possible to avoid forming loop antennas that attract external radiation interference. Additionally, the input and output wires must maintain appropriate spacing according to UL60950 safety regulations to avoid dielectric breakdown. Furthermore, no wiring is allowed under the power supply base, especially signal lines and electromagnetic lines from power transformers, which can interfere with signals.

Another aspect designers need to pay attention to is ensuring that the primary and secondary power supplies, as well as the power supply and system operating frequency, are offset to avoid mutual system compatibility issues.