Soft Commutation Isolated DC-DC Converters pp 245-269 | Cite as

# Three-Level Neutral Point Clamped ZVS-PWM Converter

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## Abstract

This chapter studies the Three Level, Zero Voltage Switching, Pulse-Width-Modulated (TL-ZVS-PWM) dc–dc converter, which main attribute is that the maximum voltage across the switches is half of the input voltage. After the introduction of the power converter topology, qualitative analysis and description of operation, along with topological states for each time interval and relevant waveforms are presented. Then, quantitative analysis, focusing on static gain and soft-commutation are discussed. The necessary equations for the design of the parameters involved in the soft-commutation are obtained. Finally, numerical examples to illustrate the theoretical analysis, numerical simulations and proposed exercises with solutions are presented in the text.

## Keywords

Soft Commutation Relevant Waveforms Zero Voltage Switching (ZVS) Commutation Time Interval Transformer Primary Winding## Nomenclature

- V
_{i} Input DC voltage

- V
_{o} Output DC voltage

- P
_{o} Output power

- C
_{o} Output filter capacitor

- L
_{o} Output filter inductor

- R
_{o} Output load resistor

- PWM
Pulse width modulation

- ZVS
Zero voltage switching

- q
Static gain

- D
Duty cycle

- D
_{nom} Nominal duty cycle

- D
_{ef} Effective duty cycle

- ∆D
Duty cycle loss

- f
_{s} Switching frequency

- T
_{s} Switching period

- t
_{d} Dead time

- T
Transformer

- n
Transformer turns ratio

- \( {\text{v}}^{\prime}_{\text{o}} \) (\( {\text{V}}^{\prime}_{\text{o}} \))
Output voltage referred to the transformer primary side and its average value

- i
_{o} Output current

- \( {\text{I}}^{\prime}_{\text{o}} \)\( \left( {\overline{{{\text{I}}_{\text{o}}^{{\prime }} }} } \right) \)
Average output current referred to the primary side and its normalized value

- \( {\text{I}}^{\prime}_{\text{o}} \)
_{crit} Critical average output current referred to the primary side

- S
_{1}, S_{2}, S_{3}and S_{4} Switches

- v
_{g1}, v_{g2}, v_{g3}and v_{g4} Switches S

_{1}, S_{2}, S_{3}and S_{4}drive signals, respectively- D
_{1}, D_{2}, D_{3}and D_{4} Diodes in anti-parallel to the switches (MOSFET—intrinsic diodes)

- D
_{C1}, D_{C2} Clamping diodes

- C = C
_{1}= C_{2}= C_{3}= C_{4} Capacitors in parallel to the switches (MOSFET—intrinsic capacitors)

- L
_{r} Resonant inductor

- C
_{r} Resonant capacitor

- i
_{Lr peak} Resonant inductor peak current

- v
_{Cr peak} Resonant inductor peak voltage

- L
_{c} Commutation inductor (may be the transformer leakage inductance or an additional inductor, if necessary)

- i
_{Lc} Commutation inductor current

- ω
_{o} Resonant frequency

- v
_{C1}, v_{C2}, v_{C3}and v_{C4} Capacitors voltage

- v
_{ab} Ac voltage, between points “a” and “b”

- v
_{S1}, v_{S2}, v_{S3}and v_{S4} Voltage across the switches

- i
_{S1}, i_{S2}, i_{S3}and i_{S4} Current in the switches

- i
_{C1}, i_{C2}, i_{C3}and i_{C4} Current in the capacitors

- ∆T
Time interval in which v

_{ab}= ±V_{i}- ∆t
_{2} Time interval of the first and fourth step of operation in DCM

- ∆t
_{10} Time interval of the first step of operation in CCM (t

_{1}–t_{0})- ∆t
_{21} Time interval of the second step of operation in CCM (t

_{2}–t_{1})- ∆t
_{32} Time interval of the third step of operation in CCM (t

_{3}–t_{2})- ∆t
_{43} Time interval of the fourth step of operation in CCM (t

_{4}–t_{3})- ∆t
_{54} Time interval of the fifth step of operation in CCM (t

_{5}–t_{4})- ∆t
_{65} Time interval of the sixth step of operation in CCM (t

_{6}–t_{5})- ∆t
_{76} Time interval of the seventh step of operation in CCM (t

_{7}–t_{6})- ∆t
_{87} Time interval of the eighth step of operation in CCM (t

_{8}–t_{7})- I
_{S14 RMS}\( \left( {\overline{{{\text{I}}_{{{\text{S}}14\,{\text{RMS}}}} }} } \right) \) Switches S

_{1}and S_{4}RMS current and its normalized value- I
_{S23 RMS}\( \left( {\overline{{{\text{I}}_{{{\text{S}}23\,{\text{RMS}}}} }} } \right) \) Switches S

_{2}and S_{3}RMS current and its normalized value- I
_{D1234}\( \left( {\overline{{{\text{I}}_{{{\text{D}}1 2 3 4}} }} } \right) \) Diodes D

_{1}, D_{2}, D_{3}and D_{4}average current and its normalized value- I
_{DC12}\( \left( {\overline{{{\text{I}}_{\text{DC12}} }} } \right) \) Clamping diodes average current and its normalized value

## Reference

- 1.Pinheiro, J.R., Barbi, I.: The Three-Level ZVS-PWM DC-to-DC converter. IEEE Trans. Power Electron.
**8**(4), 486–492 (1993)CrossRefGoogle Scholar