The speaker in the given audio is discussing the concept of soft switching in the context of a dual active bridge (DAB), a type of DC-DC converter. The speaker introduces the concept of soft switching, which aims to reduce or eliminate triangular switching losses in a DAB.
Soft switching can be achieved either through control methods or through specific arrangements of electronic devices, referred to as topologies. The speaker elaborates on two distinct types of soft switching: zero current switching (ZCS) and zero voltage switching (ZVS).
In a DAB, the voltages and currents of the switches are defined by the input and output voltages and the inductor current. The speaker demonstrates how to achieve soft switching by manipulating the voltages and currents at the zero-crossing points of the current waveform in the DAB.
The speaker also explains that to achieve ZVS for turn-on, the switches must be turned off at the zero-crossing points, allowing the diodes in the bridge to turn on, which in turn forces the voltage across the FET to be at the forward voltage (VF) of the diode. This reduces the switching loss on turn-on.
For ZCS, the switches need to be turned on at the zero-crossing points to achieve zero current switching. This prevents the use of phase shift modulation to control the output voltage, as the phase shift is used to control zero current switching instead.
In conclusion, the speaker highlights the importance of understanding voltages and currents in a DAB to achieve soft switching. The switches must be carefully controlled at the zero-crossing points to achieve ZVS for turn-on and ZCS.
1. The speaker introduces the topic of soft switching in the context of Dual Active Bridge (DAB), a type of DC-DC converter.
2. Soft switching refers to the reduction or elimination of triangular switching losses in a converter.
3. The speaker explains that soft switching can be achieved through either control or topologies.
4. The two main types of soft switching are zero current switching (ZCS) and zero voltage switching (ZVS).
5. The speaker describes the process of zero current switching in a DAB, explaining that the switches in the DAB are switched at zero current points to minimize switching loss.
6. The speaker also discusses the concept of dead time, the time period when no switches are on, which is necessary for ZVS.
7. The speaker explains that the length of dead time is dependent on the current in the inductor and the output current.
8. The speaker highlights that achieving zero current switching requires precise timing or automatic adjustment of these timings as the converter operates.