Common mode choke coils are a noise reduction measure for high-frequency noise in automotive equipment

The automotive market is expanding applications such as ADAS, autonomous driving, V2X, and in-vehicle information systems. Since such applications have to process huge amounts of information, the processing speed of internal processing signals is also increasing in order to perform processing. On the other hand, as the number of components increases and the mounting density increases, components are required to be miniaturized. In addition, with the expansion of wireless communication applications that can perform high-speed information communication, it is required to deal with higher-frequency noise.

Common mode choke coils are effective in reducing noise radiated from power lines. In the past, the main noise reduction target for power lines of automotive equipment was the frequencies in the AM and FM bands, so large components were used to deal with low-frequency noise. However, with the rapid development of automotive equipment, high-frequency noise reduction measures above the AM and FM bands are required.

In response to this trend, Murata Manufacturing has commercialized the DLW32PH122XK2 common mode choke coil for power lines, which is suitable for high-frequency noise suppression. This article introduces the noise suppression effect of the DLW32PH122XK2.

Radiated noise reduction effect of common mode choke coils

In the measurement system described below, the noise radiated from the EUT using the power cable as an antenna was measured, and the effect of reducing noise using a common mode choke coil was clarified.

【Measurement system】

・Compliant with the international vehicle noise control standard CISPR25

The EUT in this measurement generated noise in the range of 200MHz-800MHz, but by inserting the DLW32PH122KX2, the noise in this range was significantly reduced.

Noise evaluation results (vertically polarized wave, AVE detection)

Noise reduction effect of common mode choke coil BCI test

The BCI test is a test for verifying the resistance to noise from the outside.

If external noise enters, it may cause the EUT to malfunction. If the noise immunity is poor, even small noise can cause malfunction. This test verifies the degree of improvement that can be achieved by inserting the DLW32PH122XK2.

【Measurement system】

・Measurements were performed using the BCI test substitution method specified in ISO11452-4, the international vehicle noise control standard.

In the EUT measured this time, after the injection of 360 to 400 MHz noise, the DC/DC converter switching stopped and the output voltage malfunctioned to 0 V. By inserting the DLW32PH122KX2, the noise in this range was significantly reduced, and the noise tolerance to malfunctions was improved.

Summarize

In the past, AM/FM band noise reduction measures were sufficient for automotive equipment. However, in recent years, with the continuous advancement of automotive equipment, there is a demand to eliminate noise of several hundred MHz.

Compared with conventional common mode choke coils for power lines, the DLW32PH112XK2 common mode choke coil has superior high-frequency noise reduction performance and can handle noise of several hundred MHz.