The auxiliary converter is the power source of the vehicular electronic system, the failure of which may cause inestimable economic loss. As the most age-affected component in the converter, the online health monitoring for output aluminum electrolytic capacitor (AEC) is of great significance. Throughout the full-life period of AEC, the capacitance ( $C$ ) will fall and the equivalent series resistance (ESR) will rise. This article proposes an online proactive health monitoring method for output capacitors of a 1-kW vehicular auxiliary converter. The operating mechanism of the two-level Boost-LLC converter is analyzed and the ESR calculation model is derived in detail. A novel ripple measurement approach and a peak current calculation method are proposed. Both ripple measurement and current approximation are confirmed to be practical and applicable. Finally, the online health monitoring platform is built. The experimental results can show the effectiveness of this method. The monitored ESR can indicate the healthy degree for the output capacitors in the auxiliary converter. The influences of switching frequency and ambient temperature are verified to express the superiority of the online monitoring scheme.

Automotive auxiliary converter empowers the electronic system, the failure of which will affect the system performance. As a critical component in the feedback loop of the converter, real-time health monitoring for optocoupler is of great importance. The degraded optocoupler mainly shows a falling current transfer ratio (CTR). This article proposes an online proactive CTR monitoring method for optocoupler via voltage measurement of critical nodes. The monitored CTR can indicate the health condition of the optocoupler. First, the principle of a boost- LLC converter is analyzed in detail. Then, the influences of degraded CTR on the feedback loop are derived. An online proactive CTR monitoring scheme is introduced. The realization of voltage measurement, signal filtering, wireless communication, and time synchronization are in two independent embedded systems. CTR will be calculated in the local server and be stored in the local database. The proposed method can monitor CTR for both unaged and aged optocouplers. Effects of switching frequency and ambient temperature are also incorporated for online CTR monitoring. Experimental results validate the superiority of this online proactive monitoring method. The method could be extended and further evaluate the health condition of the overall automotive auxiliary converter.

As the core of electronic system, the switched-mode power supply (SMPS) will lead to serious accidents and catastrophes if it suddenly fails. According to the related research, the monitoring of ripple can acquire the health degree of SMPS indirectly. To realize low-cost, high-precision, and automatic ripple measurement, this paper proposes a new ripple voltage (peak-to-peak value) measuring scheme, utilizing a DAC and two high-speed comparators. Within this scheme, the DC component of SMPS output is blocked by a high-pass filter (HPF). Then, the filtered signal and the reference voltage from a DAC together compose the input of a high-speed comparator. Finally, output pulses of the comparator are captured by a microcontroller unit (MCU), which readjusts the output of the DAC by calculation, and this process is repeated until the DAC output is exactly equal to the peak (or valley) value of ripple. Moreover, in order to accelerate the measurement process, a peak estimation method is specially designed to calculate the output ripple peak (or valley) value of buck topology through merely two measurements. Then the binary search method is utilized to obtain a more exact value on the basis of estimative results. Additionally, an analysis of the measurement error of this ripple measurement system is executed, which shows that the theoretical error is less than 0.5% where the ripple value is larger than 500 mV. Furthermore, appropriate components are selected, and a prototype is manufactured to verify the validity of the proposed theory.