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Reasons and solutions for abnormal startup of DC/DC power supply

Article Source：Kinri Energy | Author：Kinri Energy | Issuing Time：2024.04.09
Abstract: This article briefly describes the common problems of power failure in switching power supply applications, and analyzes the reasons for their occurrence. At the same time, corresponding verification, prevention, and solution methods are provided to reduce the occurrence of power failure in different applications and improve system reliability.



Introduction

In daily work, hardware design engineers often use DC/DC power supplies, and often encounter problems such as power failure or poor startup, such as:

(1) The input is normal, why is there no output from the power supply?

(2) Why does the external output indicator light flash and the backend device not work after power on?

(3) As soon as the load power increases, the power supply cannot be started, and the load does not exceed the power supply. Why?

This article will sort out the problems of poor startup of DC/DC power supplies, analyze their causes, and provide corresponding solutions.

Common startup abnormalities of DC power supply

Poor power startup generally manifests as two situations: no voltage output and output hiccup;

DC/DC power supply is often used as a secondary power supply, usually placed in a PCB board. When designing and using it, the first concern is whether the power supply can output normally and what its load capacity is; But during testing, we often encounter many problems. Common situations include:

(1) After power on, there is no output;

(2) After power on, the output keeps burping, and the system cannot work;

How should we analyze, confirm, and troubleshoot these issues when we encounter them? Next, we will analyze each problem one by one.

Power supply has no output

Usually, there are several main reasons for the lack of power output:

(1) Supply voltage too high or too low:

Method of judgment: Use a multimeter to directly measure the voltage at both ends of the input terminal, and compare it with the voltage input specifications in the technical manual, such as 9-36V;

Solution: Input voltage range according to the power supply specifications to supply power to the power supply.

(2) Insufficient power supply

Judgment method: Calculate the actual power of the output load and compare it with the power of the front-end power supply;

Solution: Replace with a higher power supply or reduce the load power.

(3) DC/DC power module with CTRL pin, control logic error

Judgment method: Check the control logic of the CTRL pin in the power manual and test the actual status of the CTRL pin;

Solution: Follow the instructions in the power manual to design the CTRL pin and confirm that the control logic is normal.

(4) The peripheral circuit diode devices are reversed, and the DC/DC power output is usually connected to peripheral devices with positive and negative polarity such as electrolytic capacitors and voltage stabilizing diodes; Reverse connections can cause anomalies.

Judgment method: Test the module separately to see if it has output. If the module is normal, add peripheral abnormalities and troubleshoot whether the peripheral components are normal;
Solution: Correct the polarity of the output device and choose the appropriate specifications.

Output Hiccup

Usually, output hiccups are caused by high transient power of the load, exceeding specifications; Or capacitive load exceeding specifications:

(1) Capacity load exceeding specifications

Judgment method: Modules with different output voltages have different specifications for capacitive loads; Check the total capacitance value of the output terminal of the power supply and calculate whether it exceeds the power supply specification range;

Solution: Reduce the capacitance value of the power output terminal to ensure that the total capacitance value of all output terminals is within the range promised by the power supply.

(2) High transient power of loads (such as motors)

Method of judgment: Use an oscilloscope to test the transient load current at the output end and compare it with the overcurrent point of the power supply. If the measured starting current is greater than the overcurrent point, the module cannot start normally;

Solution: It is recommended to choose modules with higher power or perform slow start processing at the load end to limit the starting current.

Summary

This article briefly describes the startup abnormal problems in the application of DC/DC power supplies, and briefly analyzes the causes of the problems. At the same time, corresponding verification, prevention, and solution methods are provided to reduce more problems in the design of power supplies; Kinri Energy serves customers with a professional sales and technical service team, providing pre-sales selection, technical communication during sales, and professional after-sales support, providing customers with one-stop solutions.
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