Failure Analysis Report for 12V 10A DC-DC Converter

Recently, a customer reached out to us regarding an issue they encountered with a batch of DC-DC converter modules they had purchased from their previous supplier.

The product is used in an outdoor system powered by a 14.6V lithium iron phosphate (LiFePO₄) battery. The input voltage, supplied through a solar charge controller, fluctuates between 11.5V and 14.6V. The DC/DC module is directly connected to the controller’s output and is primarily used to power a 12V / 2A fan.

After several weeks of use, they experienced frequent fuse failures (20A fuse at the input side), despite no changes being made to the product design. According to them, such issues had never occurred before. They asked us to help analyze the possible causes.

Possible causes of failure

From Xelite's technical team's perspective, we believe the issue is likely related to a batch problem in the DC-DC converters. Possible reasons include:

A. Raw Material Issues
– For example: using incorrect or low-quality components.
B. Production Process Issues
– For example: solder ball short circuits. The solder balls moved around the solder joints or within PCB gaps, potentially bridging two pins or circuit traces, which affected the normal operation of the product. Or there may be cold solder joints, or vacuum pockets caused by improper potting

If the root cause is not related to the quality of the converter itself, external factors could also lead to Voltage Regulator failure. These may include:

A. Input Overvoltage
– This could be caused by lightning strikes or an unstable power source supplying higher-than-rated voltage.

B. Output Overcurrent Due to Load Behavior
– This may happen if the output load draws excessive current, for example from a  fan motor.
If the fan is blocked or stalls, the locked-rotor current can be 5–12 times the normal operating current, reaching up to 15A–36A.

To confirm, an oscilloscope with a current probe should be used to monitor both the power supply and the load device in real-time.

In addition, the customer mentioned that during power-up or controller startup, a high inrush current may occur, potentially leading to fuse failure — even though the load remains stable and relatively low at around 2A.

Using anti-inrush current fuse, rated at 30A and input electrolytic capacitor--680μF could solve this problem.

The customer also raised concerns about possible reverse current or transient abnormal phenomena occurring inside the DC-DC module.

However, in scenarios where the output-side load (e.g., a fan) suddenly stops, reverse current may be induced. This can be effectively eliminated by an output-side reverse diode, as shown in the schematic diagram below.

Transient abnormal phenomena to be addressed through professional power supply design.

The customer also suspects that transient oscillations or abnormal current may occur on the input side during the switching process of the solar controller, although there is no conclusive evidence yet.
This issue can be investigated by using an oscilloscope and current probe to monitor the voltage and current waveforms of the solar controller during operation.

The customer's new requirements

After analyzing the possible causes of the DC-DC converter failures, the customer proposed new design requirements. The product must maintain reliable performance under harsh environmental conditions, including high ambient temperatures (e.g., 55°C), significant input voltage fluctuations, and extended continuous operation.

In response, Xelite has developed a DC-DC converter sample that has successfully passed the temperature rise test. It can operate continuously under a 5A load in an 80°C environment, or an 8A load in a 55°C environment.

With an input voltage range of 9.5V to 36V, and the converter operates stably within this range.

2. High Inrush Current Withstand Capability. The converter should tolerate high inrush current, or ideally integrate soft start, NTC, or active inrush suppression circuitry.

Xelite uses a 30A high inrush current withstand fuse to protect against power-on surges.

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3. No Reverse Current or Interference During Operation. The converter must not produce reverse current or generate interference toward the battery or controller.

Tests have confirmed that the Xelite DC/DC converter exhibits no reverse current or interference current

Customized solutions tailored to customer needs

Based on a thorough understanding of the customer's requirements, Xelite ultimately developed a customized DC-DC converter to meet customer's specific application needs.

Xelite 9–36V to 12V 10A 120W DC-DC Converter — Key Features

1. Reverse Polarity Protection on Input
– The converter will not be damaged if the input polarity is accidentally reversed.
(Note: Some competing products lack this protection.)

2.30A Inrush Protection Fuse on Input
– Fuse will not blow during power-up or shutdown.
(Note: Some products do not include input fusing.)

3.High Thermal Endurance
– Capable of continuous operation at 5A under 80°C or 8A under 55°C ambient temperature.

4.Reverse Diode on Output
– Provides a safe discharge path for inductive loads (e.g., motors or fans) when shut down.

5.Stable Output Voltage
– Regulated 12.0V to 13.0V, with no negative tolerance.

6. High-Thermal Conductivity Potting Compound
– Uses UL-certified organic silicone with thermal conductivity ≥0.8 W/m·K, rated for -60°C to 200°C.
(Note: Many competitors use epoxy resin with only ~0.3 W/m·K and max temperature ~100°C.)

7. Double Potting Process
– First, 1 cm of potting is applied to the empty housing. Then, the PCBA is installed and fully potted. This ensures all heat-generating components are thermally bonded for optimal heat dissipation.

8. Short-Circuit Protection
– The output is protected from short circuits. The converter will recover automatically once the short is cleared.

9. Overtemperature Protection
– Internal protection triggers at 110°C, with automatic recovery upon cooling.

10.High Conversion Efficiency
– Achieves up to 93% efficiency under rated conditions.

At Xelite, we are committed to delivering fully customized power solutions to meet the evolving needs of our ODM and OEM clients.

Our team has successfully developed a wide range of programmable intelligent power supplies, PCBA control boards, DC-DC converter and power modules tailored to specific customer requirements.

Let's talk about how we can support your next project.

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