Silergy (China)

Recently, multilevel converters with gallium nitride (GaN) devices have shown marvelous advantages for power factor correction (PFC) conversion to meet the increasingly higher efficiency and power density requirements. In the traditional design process for the multilevel PFC converter, it is necessary to separately optimize the devices of the corresponding breakdown voltage under different level number, which causes difficulty to the overall optimization of the entire system. In this paper, a unified minimum loss model for GaN switches regardless of voltage levels is proposed to optimize the efficiency based on device’s new figure-of-merit (NFoM) (NFoM = COSS(ER) RDS(on)). With the help of this unified minimum loss model, it simplifies the efficiency optimizing methodology according to the NFoMs of GaN devices for multilevel PFC converter. According to the methodology, a 2 kW cascaded H-bridge (CHB) PFC prototype is constructed to verify the design methodology, achieving over 99% efficiency with power density over 1000 W/in3 .

BackgroundPru p 1 is a major allergen in peach and nectarine, and the different content in varieties may affect the degree of allergic reactions. This study aimed to quantify Pru p 1 levels in representative peach varieties and select hypoallergenic Pru p 1 varieties.MethodsTo obtain monoclonal and polyclonal antibodies, mice and rabbits, respectively, were immunized with recombinant Pru p 1.01 and Pru p 1.02. The Pru p 1 levels in fruits from 83 representative peach varieties was quantified by sandwich enzyme‐linked immunosorbent assay (sELISA). nPru p 1 was obtained through specific monoclonal antibody affinity purification and confirmed by Western blot and mass spectrometry. The variable Pru p 1 content of selected varieties was evaluated by Western blot and the expression level of encoding Pru p 1 genes by quantitative polymerase chain reaction.ResultsA sELISA method with monoclonal and polyclonal antibodies was built for quantifying Pru p 1 levels in peach. Pru p 1 was mainly concentrated in the peel (0.20–73.44 μg/g, fresh weight), being very low in the pulp (0.05–9.62 μg/g) and not detected in wild peach. For the 78 peach and nectarine varieties, Pru p 1 content varied widely from 0.12 to 6.45 μg/g in whole fruit. We verified that natural Pru p 1 is composed of 1.01 and 1.02 isoallergens, and the Pru p 1 expression level and Pru p 1 band intensity in the immunoblots were in agreement with protein quantity determined by ELISA for some tested varieties. In some cases, the reduced levels of Pru p 1 did not coincide with low Pru p 3 in the same variety in whole fruit, while some ancient wild peach and nectarines contained low levels of both allergens, and late‐ripening yellow flesh varieties were usually highly allergenic.ConclusionPru p 1 content is generally low in peach compared to Pru p 3. Several hypoallergenic Pru p 1 and Pru p 3 varieties, “Zi Xue Tao,” “Wu Yue Xian,” and “May Fire,” were identified, which could be useful in trials for peach allergy patients.

Conventional half bridge class-D audio amplifier (HB-CDAA) systems typically suffer from serious bus-voltage pumping. Such a bus-voltage pumping increases the device stress and deteriorates the total harmonic distortion and noise (THD+N) of HB-CDAA. To reduce the bus-voltage pumping of HB-CDAA system, large electrolytic capacitors are usually required at the input of downstream HB-CDAA, which seriously affects the power density of HB-CDAA system. In this article, an electrolytic capacitor-free HB-CDAA system without bus-voltage pumping is proposed, which consists of a front-end bipolar-symmetric-outputs (BSO) bidirectional dc-dc converter and a downstream HB-CDAA. By providing a bidirectional current flowing path in the front-end dc-dc converter, the bus-voltage pumping of the HB-CDAA system is eliminated without using large electrolytic capacitors. Zero voltage switching (ZVS) of all switches in the front-end BSO dc-dc converter can be achieved over the full audio load range. Compared with the HB-CDAA system with a unidirectional front-end dc-dc converter, the proposed audio amplifier system benefits from high power density, low-output voltage THD+N, and voltage stress of switches. The bus-voltage pumping problem is identified, the operation of the proposed HB-CDAA system is analyzed, and the design parameters of the converter are derived to ensure ZVS of all switches. Experimental results with a 40-W prototype of the proposed audio amplifier system are presented to verify the design.