SCR controller is one of the components of the SCR system, which should pass the test pulse 5b. The features and test requirements of pulse 5b are introduced. Its energy is very large, so passing the test is difficult. Two surge voltage suppression circuits are designed. The first design utilized a surge stopper-LT4356, its work process includes fault timer period, warning period and cooling period. During the cooling period, the SCR controller cannot work normally. So connecting a capacitor in parallel to the output of the surge voltage suppression circuit is used to improving its performance. The second design utilized two pieces of TVS, since the test pulse is continuous, steady state power dissipation must be considered when choose TVS. Finally, it verifies the feasibility of the two design schemes by experiments and leads to a selection criteria for them.

DC-DC buck converter has been more widely used in automotive electronics because of its advantage of high efficiency and small size. However, it is one of the main causes of the conducted emission and radiation noise. The working principle and the mechanism of DC-DC buck converter which generate conducted emission and radiation noise in different frequency were analyzed. Then, two methods were proposed to reduce the low frequency radiated emission. One is weakening the AC current value of the inductor current through increasing the value of the output inductor, the other is reducing the loop area by adding the output filter, and both of the methods were verified by comparative test. Finally, the two schemes were used in designing the On-board controller, and it passed the radiated emissions (ALSE method) according to the international standard CISPR 25-2008.