However, these converters operate with nique is deemed desirable since it implements zero-voltage sinusoidal current through the power switch es which results switching ZVS for all semiconductor devices without in- in high peak and rms currents for the power transistors and creasing voltagekurrent stresses [4], [5 ].
This technique min- high voltage stresses on the rectifier diodes. They are particularly suited for high-powerhgh- ing losses. In the following section, the ZCT-PWM boost Basically, ZVS eliminates the capacitive turn-on loss, and converter is used as an example to illustrate the principle of reduces the turn-off switching loss by slowing down the operation.
This technique can be effective The converter differs current overlap by forcing the switch current to zero before from a conventional PWM boost converter by the introduction the switch voltage rises.
This resonant branch is active only during Several ZCS techniques were reported [7]-[13]. It is well- a short switching-transition time to create the ZCS condition known that the conventional resonant converters, such as for the main switch.
In the analysis, the boost inductor, L f , the parallel-resonant converter, series-resonant converter, and is assumed to be large enough to be considered as a current LCC-type converters, can achieve ZCS for power transis- source, Ii. In steady-state, five operating stages exist within tors when operated below the resonant frequency.
Constant- one switching cycle refer to Fig. It can be seen that to achieve zero-current turn-off for the transistor, has to be greater than I ,. In steady-state operation as explained later , the resonant inductor current at TIis always equal to I,. Thus the time delay between these two gate-drive turn-off signals, t d 2 , determines the peak voltage of C,: 3 if v;ak 5 v,. In a practical design, T d 2 can be selected at around 0.
Equivalent circuits for five topological stages. This operating stage energy stored in the resonant tank remains constant over the is identical to the transistor-off stage of the PWM boost entire switching cycle.
This can be clearly seen from the above converter. During each topological stage shown in Fig. Meanwhile, C, and Lr or the current through it is zero, so there is no energy transfer form a half-cycle resonance through S and the anti- between the resonant elements and other parts of the circuit.
C, voltage. The energy stored in the resonant tank, which is self-adjusted e TA-T,: Operation of the circuit is identical to that of in accordance with line and load conditions, can be given by the transistor-on period of the PWM boost converter. At TO,S1 is turned on again, and the switching cycle is 7 repeated.
HUA er al. Equation 7 reveals that regardless of the line and load changes, the energy stored in the resonant tank will always be adaptively adjusted so that it is only slightly higher than what is needed for creating the ZCS condition. For high-voltage applications such as power-factor cor- rection PFC where the boost diode suffers from a severe TO reverse-recovery problem, an additional inductor or a sat- T4 urable inductor in series with the rectifier diode or the main switch is usually used to suppress the reverse-recovery problem.
At transistor turn-off, this inductor invokes a high- voltage spike on the transistor due to high d i l d t across the inductor. To suppress this voltage spike, a large dissipative snubber is frequently used. For a ZCT boost converter with the same additional inductor, however, this voltage spike is much reduced due to controlled d i l d t across the inductor at Fig.
State-plane trajectory of the resonant tank. As a result, a much smaller snubber can be used to absorb this ringing. Similarly, for isolated topologies, the ZCT technique can significantly reduce the transistor turn-off voltage spike caused by leakage inductance of the transformer. An additional topological stage occurs when the circuit offsets the From the circuit topological point of view, every resonant- type converter including the conventional resonant, quasi- This circulating energy increases as input current increases resonant, and multi-resonant converters can be viewed as a when line voltage decreases or load current increases.
In variation of its PWM counterpart. By incorporating certain a practical circuit, since the resonant transition time is very type of resonant network, it creates a resonance to achieve short with respect to the switching cycle, the resonant induc- ZVS or ZCS. For different resonant converters, of course, the tance is very small compared to boost inductance. Therefore, type of resonant network employed is different.
Soft-switching is achieved by utilizing or load condition change. In this case, there will be an additional resonant capacitors, which are usually in parallel with the topological stage inserted between mode b and mode c in semiconductor devices. Due to the fact that these resonant Fig. During this operating stage, the elements are placed in the main power path, the resultant resonant branch transports energy to the load.
Therefore the resonant converters are always subjected to inherent problems. Second, since all the power flows shown in Fig. It can be seen that the boost inductor through the resonant inductor, substantial circulating energy will pump some energy into the resonant branch during this is always created, which significantly increases conduction operating stage.
Therefore, the energy stored in the resonant losses. In addition, the energy stored in the resonant inductor branch will increase until it reaches the balance point given strongly depends on the line voltage and load current.
There- by 7. This is why most resonant converters technique implements zero-current turn-off for the power are unable to maintain soft-switching for a wide line and load transistor without penalizing the voltage stresses of both range. Although the To alleviate the above-mentioned limitations, it is necessary main switch current waveform exhibits a resonant peaking, to remove the resonant element s from the main power path.
The use of the shunt resonant network enables the circuit to operate at much higher switching frequencies. The features Fig. When switching transition is over, the circuit simply reverts back to the familiar PWM operating mode. In this way, minimal circulating energy, wide line and load ranges for ZCS, the converter can achieve soft-switching while preserving the constant-frequency operation. In fact, the above-suggested concept of using a shunt resonant network has been adopted in the ZVT-PWM converters [4].
The mented in perhaps a number of different ways. One should circuit is regulated at V output with a V input keep it in mind that it is desirable to minimize the circulating range. The circuit diagram of the experimental converter is energy and circuit complexity.
Furthermore, it also is desirable shown in Fig. In this study, a new snubber cell is developed in order to increase the power density and the efficiency in pulsewidth modulation PWM converters and to decrease the EMI noise.
The developed snubber … Expand. Also, … Expand. View 4 excerpts, cites background. In this study, boost converter with a new active snubber cell is proposed. Also, the auxiliary switch turns on with ZCS … Expand. View 1 excerpt, cites background. In this paper, a novel active snubber cell which is used in a boost type DC-DC converter is proposed. The proposed snubber cell provides zero voltage transition ZVT and zero current transition … Expand.
The proposed improved design guidelines are … Expand. This paper introduces a study of a new boost converter with an active snubber cell which is developed to overcome most of the drawbacks of conventional zero-voltage transition ZVT and zero-current … Expand.
View 3 excerpts, cites background. Novel zero-voltage-transition PWM converters. PESC '92 Record. A class of zero voltage transition ZVT power converters is proposed in which both the transistor and the rectifier operate with zero voltage switching and are subjected to minimum voltage and … Expand. View 1 excerpt, references methods. Novel zero-current-transition PWM converters. The new family of converters implements zero-current turn-off for power transistor s without … Expand.
A soft-switching active snubber is proposed to reduce the turn-off losses of the insulated gate bipolar transistor IGBT in a buck power converter. The soft-switching snubber provides zero-voltage … Expand. A soft switching active snubber is proposed to reduce the turn-off losses of the IGBT in a current-mode controlled buck power converter. The soft switching snubber provides zero-voltage switching for … Expand. A novel zero-voltage switched PWM boost converter.
View 3 excerpts, references methods and background. A zero-voltage switched PWM boost converter with an energy feedforward auxiliary circuit. PESC Record. A zero-voltage switched ZVS PWM boost converter with an energy feedforward auxiliary circuit is proposed in this paper. Soft-switching techniques in PWM converters.
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