IT8700P multi-channel electronic load test converter decryption

AC/DC and DC/DC converters are widely used in various industries, such as mobile phones, digital cameras, UPS power supplies, electric vehicles and so on. For manufacturers, the performance, safety and conversion efficiency of converters are all important factors for winning the market. Therefore, every step from R&D to production needs to be tested. DC load is an indispensable tool in these tests. It can not only test the normal working voltage, current and power of the product, but also easily test the product in the state of intermediate value, Dynamic changes and response time, etc. However, when engineers use the load to test the protection function of the product, they will sometimes find that the load cannot be used normally. What is the reason for this?

Today, we will use a high-performance Electronic load product recently upgraded by ITECH, IT8700P multi-input programmable DC electronic load to test a DC/DC component, and decrypt the actual test. IT8700P is an upgraded version of high-performance programmable multi-channel electronic load IT8700, which maintains the original high dynamic test speed of 25KHZ, and has multiple optional modules and powerful main control chassis. To meet the test requirements, the pre-terminal wiring function is optional, and a series of optimization and upgrades have been made to the slope speed, DAC output speed, and CV loop speed, which can better meet the test requirements.

Test instrument: IT8732P (80V/60A/400W) + IT8702P (main control unit)

Test background: The normal working output voltage of DC/DC components is 5V/1A. When the current rises above 2.8A, the product will enter the protection mode of OCP, and will not return to the normal working mode until the abnormal condition is eliminated.

Test Question 1:

1. Von is set to 0.1V, latch is set to off.

2. IT8732P is set to 1A CC mode pull load, the DUT works normally and outputs 5V/1A.

3. When the load current is increased to 3A, the DUT should enter the OCP protection mode. But at this time, it is in the state of oscillation, and the voltage value oscillates from 0V to 4.8V. At this time, if the pulling current of the IT8732P is reduced to 1A, the DUT is in the normal working mode of 5V, 1A.

Problem decryption: The reason for the oscillation is that the voltage of the object to be tested after entering the OCP is pulled by each other. Von is set to 0.1V, latch is set to off. When the DUT enters the OCP, and the voltage value is lower than 0.1V, the load will also discharge the load, and the pull-up current will drop. After the DUT detects that the current is lower than its set value, it will return to normal. After the voltage rises, the load will return to normal. The load will be pulled, and at this time, the object to be tested will enter the OCP protection, and this cycle will cause oscillation. So at this time, as long as we set Von to 0.001V, this phenomenon will no longer occur. Of course, this is also related to the design characteristics of the DUT.

Test Question 2:

1. Von is set to 0.001V, latch is set to off.

2. IT8732P is set to 1A CC mode pull load, the DUT works normally and outputs 5V/1A. The pull-up current is increased to 3A, and the DUT enters the OCP protection mode.

3. The pull-in current returns to 1A, and the DUT does not return to the working mode of 5V/1A. After the IT8732P load discharge must be switched to OFF first, and then the load is switched to ON, the DUT will be in normal working mode again.

Problem decryption: The voltage value of the object to be tested after entering the OCP is about 0.017V, and the current value is about 0.81A. The minimum operating voltage of IT8732P is 0.15V at 6A, which is equivalent to 0.025V at 1A. Therefore, when the pull-in current returns from 3A to 1A, since the voltage value of the DUT is still 0.017V and lower than 0.025V, and the OCP release relationship of the DUT itself is designed, when the Load returns to 1A, the DUT is still If it cannot work normally, the load current must be lower than 0.8A and greater than the minimum working voltage of the load, so that the DUT can resume normal operation.

Test Question 3:

1. Von is set to 0.001V, latch is set to off.

2. When the DUT works normally at 5V/1A, execute the Short function and the voltage drops to about 0V.

3. When the Short function is OFF, the load setting value is restored, and the voltage of the DUT does not return to 5V. After the IT8732P load discharge must be switched to OFF, and then the load is switched to ON, the DUT will be in the normal working mode again.

Problem decryption: After executing the SHORT function, the DUT is about 0.017V/0.81A. When the SHORT function is OFF, it should be restored to 5V/1A, but when the SHORT function is restored, it will return to the set value of 1A pull load, and its value is still higher than 0.81A, so the DUT is still in the unreleased state. state, so when the SHORT function is OFF, its value is still 0.017V for voltage and 0.81A for current. When the load is discharged, the DUT can return to normal.

From the above test, we can see that due to different design characteristics of different DUTs, the relationship between the voltage value and the current value and the performance of the load will conflict slightly after entering the protection, resulting in abnormal test. Therefore, we must understand the specifications, characteristics and limitations of the object to be tested and the test instrument itself when testing, in order to avoid misjudgment and maximize the effectiveness of the test instrument. For example, in the above case, we only need to reduce the load current of IT8732P to below 0.8A after the DUT enters the OCP, so that the DUT is released and then the next test procedure is performed to complete the test.

Itech Electronics has always been committed to the research in the field of related industrial testing with “power electronics” products as the core. Structure design, with the world’s original dynamic power distribution technology, can be applied to multi-channel or single-channel output AC/DC, DC/DC power converters, chargers and other power electronic components performance testing, can also be applied to ATE test system, solar cell, LED, communication test, aerospace and other fields.You can browse the ITECH official websitewww.itechate.comFor more information, or you can directly search “ITECH Electronics” official website to get more product application information.