Power Test Encyclopedia (1): Extreme Test

1. Module output current limit test

The module output current limit test is the maximum current that can be output after the test module is released at the output current limit (PFC's overcurrent protection is also released). The purpose of the test is to verify whether the module's current limit design is appropriate. Whether the device selection is appropriate. If the input current limit value of the module is too small, it indicates that the output current of the module is not enough; if the output current limit value of the module is designed too large, it indicates that the output current margin of the module is too high, and the cost of the module can also be reduced.

Test Methods:

Release the output current limit of the module, and gradually increase the output current of the module according to 5% of the rated output current. Each current value is kept for 10 minutes until the module is damaged (or the output fuse is broken), and the output current when the module is damaged is recorded. The value is the output current limit of the module. In order to prevent the module from accumulating damage during the test, after each test point is completed, the module must be cooled to the cold state before the test. The current limit of the test is 120% of the rated current of the module (that is, after more than 120%, no test is required).

judgement standard:

The current limit of the module must meet 110%, pass, and the test results are used as the basis for the module design (reference data). Otherwise it is not qualified.

2. Static high voltage input

Test instruction:

In the static high voltage, the PFC circuit realizes overvoltage protection. This test is mainly to evaluate the reliability of the power module under static high voltage conditions.

Test Methods:

A. According to the specification, adjust the module input voltage to the maximum static withstand voltage and run for 1 hour.

B. Starting from the maximum static withstand voltage point, increase the input voltage upwards at a rate of 10V/10min until the module is damaged. The input voltage value when the recording module is damaged is the highest static limit input voltage of the module. Record device damage and analyze the cause.

judgement standard:

In the above case A, the primary power module does not appear damaged or other abnormal phenomenon, and is qualified; otherwise it is unqualified. Under the B condition, the highest static input voltage of the module is recorded. As the data reference of the module, the test results under the B condition are only used as a reference, and are not used as a criterion for judging whether it is qualified.

3 temperature rise limit test

Test instruction:

The temperature rise limit test refers to the highest ambient temperature that causes the module to be damaged in the event of failure of the module over temperature protection. The purpose of the test is to investigate the maximum ambient temperature that the module can withstand, thereby providing a reference for the design of the module.

Test Methods:

Remove the temperature protection device of the module, and then place the module in the thermostat. The input voltage of the module is the lowest voltage, the output is the maximum power point, and the temperature of the temperature protection relay of the monitoring module starts from the highest ambient temperature of the module. The 5oC/30min speed gradually increases the ambient temperature until the module is damaged.

Recorded content:

When the recording module is damaged, the temperature rise of each internal key component, analyze the fault point; record the damage at the temperature limit (run time, temperature, damage device, etc.) as a reference for the data.

judgement standard:

The upper limit of the working temperature defined in the specification, the over-temperature protection of the power module shield, the long-time full-load working module is not damaged, qualified; otherwise it is unqualified.

This test result can be used as a reference for the die design. The criterion for judging is to see the maximum temperature of the module damage and the distance of the module relay to the temperature (or software protection point) of the protection. If the difference between the two is negative, it means the temperature relay. The protection function (or software protection function) has no effect. If the difference between the two is 6~10oC, it means that the module's thermal margin is too small. If the difference between the two is greater than 40 degrees, the margin is too large.

4 EFT immunity test

Test instruction:

Test the highest EFT immunity indicator that the power supply can withstand to confirm its margin. The ability of the test product to resist cumulative failures due to grid EFT due to equipment such as high frequency furnaces.

Test Methods:

A. The EFT immunity open circuit voltage is set to a specified level voltage +500V, and the impact immunity test is performed.

B. Repeat step A with 500V as a step voltage level. Each voltage level test is tested according to the standard EFT test method, and the test level voltage value of the power supply performance degradation and damage is recorded (the highest voltage tested is the EFT immunity device). Maximum voltage).

C. Confirm the damaged part of the power supply and analyze the reason.

judgement standard:

The EFT limit value is greater than 5% of the specifications, and is qualified; otherwise it is unqualified.

5 Temperature shock strengthening test

Test instruction:

Verify the high and low temperature impact limits that the product can withstand during storage and transportation.

(1) Check the electrical and mechanical properties (appearance and internal structure) according to the relevant specifications before the test to ensure that the electrical and mechanical properties of the test samples before the temperature impact test are normal.

(2) The sample is not energized during the test and no function monitoring is performed.

(3) After the test, check whether the mechanical properties (appearance and internal structure) are normal by visual inspection and other means. At the same time, the electrical performance test according to the "Communication Power Module Basic Performance Test Specification" should meet the requirements.

Test Methods:

The method of temperature-enhanced impact test is shown in the following figure:

HT: high temperature box temperature, take 80 degrees

LT low temperature box temperature, take -45 degrees

Ncyc: number of cycles, take 20T

Dt: the residence time of the sample in the holding section, take 45~60min

Ct: switching time between high and low temperature (determined by the impact box, no need to choose)

Schedule - Temperature shock strengthening test conditions:

Sample type High temperature box temperature HT Low temperature box temperature LT Holding time Dt Conversion time Ct Cycle number Ncyc

Surface mount component made of plate 130 -70 30min ≤5min 50T

Ordinary component made plate 100 -55 30min ≤5min 50T

The whole machine 80 -45 45 ~ 65min ≤ 5min 20T

Description:

If the finished board has both surface-mount components and common components, it is performed as required by ordinary components. 2

2 The holding time of the whole machine is selected between 45 and 65 minutes according to the volume of the sample. The volume is short and the volume is long.

Temperature shock test steps:

(1) Check the mechanical properties (appearance and internal structure) and electrical properties of the test samples before the test to ensure the mechanical and electrical properties of the samples are normal.

(2) Reasonably arrange the sample in the temperature shock box, and there should be enough space between the sample and the temperature wall to facilitate air circulation.

(3) Select the temperature shock test conditions according to the above table.

(4) Select the temperature impact test from the high temperature, press the start button to start the temperature impact test.

(5) The test is automatically stopped after the set number of cycles.

(6) After the end of the test, the sample was taken out from the temperature shock box and recovered at normal temperature until the sample temperature reached a stable level.

(7) Observe the sample after the test for mechanical damage (such as surface warpage, cracking, loose parts, falling off, etc.) and check for electrical properties.

(8) If the above-mentioned mechanical damage occurs in the sample or the electrical performance index does not meet the relevant specifications, the sample is considered to be damaged, and the test record sheet is filled in detail.

(9) Analyze the weak links of the test exposure and propose improvement measures.

(10) Repair or improve the sample. If there is no damage, increase the temperature impact level. Continue to test the board under the temperature and impact test conditions and make the board grade or surface-mount component to the board level until the sample is damaged. .

judgement standard:

The appearance of the prototype, mechanical and electrical properties are normal and qualified; otherwise it is unqualified.

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