High Efficiency, High Density, Switched Capacitor Converter for High Power Applications The power density of a dc-to-dc converter is generally limited by bulky magnetic components, especially in applications where the input and output voltages are relatively high. Inductor/transformer size can be reduced by increasing the switching frequency, but this reduces converter efficiency because of switching-related losses. It is better to eliminate the magnetics altogether with an inductorless switched capacitor converter (charge pump) topology. Charge pumps can increase power density as much as 10× over a conventional converter without sacrificing efficiency. Instead of an inductor, a flying capacitor stores and transfers the energy from input to output. Despite the advantages of charge pump designs, switched capacitor converters are traditionally limited to low power applications, due to the challenges presented in startup, protection, gate drive, and regulation. The is a fixed ratio, high voltage, high power switched capacitor controller that yields small and cost-effective solutions for high power, nonisolated intermediate bus applications with fault protection. Estimated solution size features 5 mm maximum height. High Efficiency Since there is no inductor used in the circuit, all four MOSFETs are soft switched, greatly reducing switching-related losses. The converter can achieve high efficiency as shown in Figure 3, where the peak efficiency is 99.3% and the full load efficiency is 98.4%. Convert between different units of electric capacitance. Information: The SI Derived Unit for electric capacitance is the farad, it's symbol is F. The thermograph in Figure 4 shows a balanced thermal design with a hot spot temperature about 82.3°C in an ambient environment of 23°C and no forced airflow. Thermal test at 48 V input, 24 V output at 20 A, and 200 kHz switching frequency. Prebalance Prevents Inrush Currents In addition to impressive efficiency and thermal performance, the LTC7820 includes a proprietary prebalance method to minimize inrush current in voltage divider applications. The LTC7820 controller detects the V LOW_SENSE pin voltage before switching and compares it with the V HIGH_SENSE/2 internally. If the voltage at the V LOW_SENSE pin is much lower than V HIGH_SENSE/2, a current source injects 93 mA of current at the V LOW pin to pull V LOW up. ![]() If the voltage at V LOW_SENSE is much higher than V HIGH_SENSE/2, another current source sinks 50 mA from V LOW to pull it down. If the voltage at V LOW_SENSE is near V HIGH_SENSE/2, that is, within the preprogrammed window, both current sources are disabled and the LTC7820 starts switching. Figure 5 shows the enormous input inrush current that occurs at start-up without precharging—more than enough to damage the MOSFETs and capacitors. In contrast, no excessive inrush current is observed after the prebalance method is applied, as shown in Figure 6. Load regulation. Protection Features The LTC7820 includes protection features to ensure high converter reliability. Overcurrent protection is enabled through a sensing resistor on the high voltage side. Internal Controll and sugesstions to improve the weakness Sejauh ini internal control sistem penggajian CV Angkasa Raya bisa dikatakan tidak memiliki kelemahan dan terbukti efektif karena perusahaan ini masih berskala kecil dengan jumlah karyawan yang tidak terlalu banyak sehingga mudah untuk dihandle. • Suggestions to Improve The Weaknesses Jadi sebaiknya perusahaan mulai mencatat aset tetapnya untuk dimasukkan ke buku besar dan financial report lainnya. DFD Kelemahan dan Saran • Internal Control Weaknesses Karena tidak ada pencatatan terhadap aset tetap perusahaan jadi tidak mengetahui berapa nilai aset tetap yang mereka miliki sehingga mengurangi angka aset di neraca. Donlot exlcel untuk input penjualan dan persediaan sederhana. Salinan dari berbagai cek tersebut akan dikembalikan kebagian utang usaha sebagai bukti kewajiban yang telah dibayar dan akun utang usaha akan diperbaharui untuk menyingkirkan kewajiban tersebut. A precision rail-to-rail comparator monitors the differential voltage between the I SENSE+ pin and the I SENSE– pin, which are Kelvin connected to a sensing resistor. When the voltage at I SENSE+ is 50 mV higher than the I SENSE–, an overcurrent fault is triggered, the FAULT pin is pulled down to ground, and the LTC7820 stops switching and starts retry mode based on the timer pin setup. Further protection is available through the OV/UV window comparator. In normal operation, the voltage at V LOW_SENSE should approach half of V HIGH_SENSE. A window comparator monitors V LOW_SENSE and compares it to V HIGH_SENSE/2. The hysteresis window voltage can be programmed and is equal to the voltage at the HYS_PRGM pin. With a 100 kΩ resistor on the HYS_PRGM pin, the V HIGH_SENSE/2 voltage must be within a (V LOW_SENSE ±1 V) window during start-up and normal operation. Otherwise a fault is triggered and the LTC7820 stops switching.
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