Soft Commutation Isolated DC-DC Converters pp 219-243 | Cite as

# Full-Bridge ZVS-PWM Converter with Inductive Output Filter

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## Abstract

In this chapter, the Full-Bridge Zero-Voltage-Switching Pulse-Width-Modulated (FB-ZVS-PWM) dc-dc converter with inductive output filter is studied. The chapter presents and describes the principle of operation of the power converter topology, the modulation strategy and the relevant waveforms. A quantitative analysis is provided, focused on obtaining the static gain and output characteristics. Subsequently, the commutation is analyzed and the main equations necessary for designing the commutation parameters are derived. Also included are numerical examples to illustrate the theoretical analysis, proposed exercises with solutions and numerical simulations.

## Keywords

Output Filter Inductor Relevant Waveforms Soft Commutation Commutation Capacitors Commutation Time Interval## 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

- ZVS
Zero voltage switching

- ϕ
Angle between the leading leg and the lagging leg

- q
Static gain

- D
Duty cycle

- D
_{ef} Effective duty cycle

- f
_{s} Switching frequency

- T
_{s} Switching period

- t
_{d} Dead time

- n
Transformer turns ratio

- \( {\text{I}}^{\prime}_{\text{o}} \)
Output DC current referred to the transformer primary side

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

- i
_{o} Output current

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

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

- S
_{1}and S_{3} Switches in the leading leg

- S
_{2}and S_{4} Switches in the lagging leg

- 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)

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

_{1}= C_{2}= C_{3}= C_{4}- v
_{C1}, v_{C2}, v_{C3}and v_{C4} Capacitors voltage

- v
_{C} Equivalent capacitors voltage

- L
_{c} Transformer leakage inductance or an additional inductor, if necessary

- i
_{Lc} Inductor current

- ω
_{o} Resonant frequency

- z
Characteristic impedance

- ∆ and β
State plane angles

- v
_{ab} Full bridge ac voltage, between points “a” and “b”

- v
_{cb} Inductor voltage, between points “c” and “b”

- v
_{ac} Voltage at the ac side of the rectifier, between points “a” and “c”

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

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

- i
_{D1}, i_{D2}, i_{D3}and i_{D4} Current in the diodes

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

- ∆T
Time interval which v

_{ab}= ±V_{i}- ∆t
_{1} Time interval of the first step of operation in CCM

- ∆t
_{2} Time interval of the second step of operation in CCM

- ∆t
_{3} Time interval of the third step of operation in CCM

- ∆t
_{4} Time interval of the fourth step of operation in CCM

- ∆t
_{5} Time interval of the fifth step of operation in CCM

- ∆t
_{6} Time interval of the six step of operation in CCM

- ∆t
_{7} Time interval of the seventh step of operation in CCM

- ∆t
_{8} Time interval of the eighth step of operation in CCM

- I
_{S13 RMS}\( \left( {\overline{{{\text{I}}_{{{\text{S}}13\,{\text{RMS}}}} }} } \right) \) Switches S

_{1}and S_{3}RMS current and its normalized value- I
_{S24 RMS}\( \left( {\overline{{{\text{I}}_{{{\text{S}}24\,{\text{RMS}}}} }} } \right) \) Switches S

_{2}and S_{4}RMS current in CCM and its normalized value- I
_{D13}\( \left( {\overline{{{\text{I}}_{{{\text{D}}13}} }} } \right) \) Diodes D

_{1}and D_{3}average current and its normalized value- I
_{D24}\( \left( {\overline{{{\text{I}}_{{{\text{D}}24}} }} } \right) \) Diodes D

_{2}and D_{4}average current and its normalized value