China
Africa
Explore chapters and articles related to this topic
High-Frequency Quαsi-Resonαnt and Resonant Converters
Published in Yim-Shu Lee, Computer-Aided Analysis and Design of Switch-Mode Power Supplies, 2017
High-frequency converters can be designed to have low weight and small size because, at high frequencies, the transformers, inductors, and capacitors used have low weight and small size. Square-wave converters work well up to about 200 kHz [52]. When the frequency is pushed higher, however, a number of problems can occur. The main problems include the following: Since the switching loss of transistors and diodes is proportional to the switching frequency, a higher frequency will result in a heavier switching loss and a lower conversion efficiency.Since the hysteresis loss of inductors and transformers is proportional to the frequency, and the eddy-current loss is proportional to the square of frequency, such losses can become intolerable at high frequencies. The skin effect at high frequencies also results in additional copper loss.The effect of leakage inductance in transformers can become very serious at a high switching frequency because of the fast rate of change of current (di/dt), which results in large voltage spikes. Snubber circuits with heavy loss may have to be used to overcome this problem. In addition, semiconductor devices with a higher voltage rating may be required. It is generally true that semiconductor devices with a higher voltage rating would have a larger on-state resistance and therefore a larger conduction loss.
Common-Mode Components
Published in Richard Lee Ozenbaugh, Timothy M. Pullen, EMI Filter Design, 2017
Richard Lee Ozenbaugh, Timothy M. Pullen
Some filter manufacturers have designed common-mode inductors that also function partially as differential-mode inductors. As before, this is done with very wide winding spacings that generate the leakage inductance needed to provide this differential inductance. Some flux of one coil fails to cut some of the other windings, creating this leakage inductance. Another way this is accomplished is by using pot cores. These use a split bobbin so that some of the flux in one half of the bobbin fails to cut the other half. This has been expanded toward using two separate bobbins that fit in the core with additional room to place a washer between the two bobbins. This washer is cut, or split, if it is a conductor to avoid the washer acting as a shorted turn. The material of the washer has little to do with the differential inductance created. It is the separation of the two windings that causes the leakage inductance. If the spacer is Mylar, the washer does not have to be cut. The leakage inductance is easy to measure with an inductance bridge. Shunt one winding of the common-mode inductor, and read the inductance of the other winding. If all the flux lines cross or cut the other turns, the reading is zero. This is truly impossible to accomplish because the turns cannot all be so tightly coupled. The difference is the leakage inductance measured by the inductance bridge. Another way is to measure both legs together, opposing, and the inductance bridge will read the leakage inductance. Some people suggest that the leakage inductance is due to flux leakage in air and not the core, so it cannot saturate. This is true to some degree, but it saturates a minor amount because not all of the flux is in the air.
Winding Capacitance and Leakage Inductance
Published in Colonel Wm. T. McLyman, Transformer and Inductor Design Handbook, 2017
Leakage inductance is actually distributed throughout the windings of a transformer because of the flux set-up by the primary winding, which does not link the secondary, thus giving rise to leakage inductance in each winding without contributing to the mutual flux, as shown in Figure 17-4.
Power Management Using One Cycle Control Strategy for Triple Input Single Output Fly Back DC–DC Converter
Published in Electric Power Components and Systems, 2022
P. Hema Rani, K. Manikanta, Saly George, S. Ashok
Leakage inductance represents the flux generated by the primary but not coupled to the secondary and vice-versa, which is modeled as a series inductor Lp – l as shown in Figure 12. The energy stored in magnetizing inductance is transferable from primary to secondary when switch Q4 is off but energy stored in leakage inductance is not transferable. Due to the non-ideal coupling between the primary and secondary windings when the primary side switch is turned OFF some energy is trapped in the leakage inductance of the winding which causes voltage spikes across the main switch during turn OFF. As power rating increases the magnitude of voltage spikes increases and requires high voltage rated switches. The energy associated with the leakage flux needs to be dissipated in an external circuit (known as snubber). To reduce leakage inductance, voltage clamping circuit is used. The voltage clamping circuit consists of a fast recovery diode in series with a parallel combination of a snubber capacitor and a resistor. The energy stored in the inductance is dissipated through parallel capacitor and resistance before the next cycle starts. The fly back converter with voltage clamping circuit is as shown in Figure 12.
GMPPT Algorithm Based Maximum Power Tracking under Dynamic Weather Conditions Employing Krill-Herd Technique
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Babu Natarajan, Namani Rakesh, Senthilkumar Subramaniam, Malavya Udugula, Sanjeevikumar Padmanaban
The isolated DC–DC converters also give high gain in voltage by selecting proper turns ratios for the high-frequency transformer (Lakshmi and Hemamalini 2018). However, the overall weight and size of the converter increase because of the transformer. Further, the leakage inductance in the transformer cause extra stress in voltage and additional losses in the switches (Babaei et al. 2018). The interleaved DC–DC converter can address all these problems like low voltage gain, stress on switches, bulky size, current ripple, thermal distribution, and leakage inductance. Compared with the conventional boost converter, the reliability of the IBC is more (Thiyagarajan, Kumar, and Nandini 2014) and its small-signal model also shows that it gives better performance (Barry et al., 2018).
Fault-Tolerant Modular Switched-Capacitor DC-DC Converter (MSCC) for Fuel Cells
Published in Electric Power Components and Systems, 2023
Xiangping Chen, Zhengzhao He, Dong Wang, Wenping Cao
The third technique is the use of magnetic coupling. It utilizes a high-frequency transformer to generate the output voltage which is proportional to the turns ratio of the transformer windings [27, 28], as shown in Figure 4. Regulating the turns ratio of the transformer is straightforward but this is restricted by the leakage inductance. Moreover, a very high leakage inductance can also give rise to the voltage drop and power losses.