TIDUF18A October 2022 – February 2024
To understand tank design, first the gains for both battery-charging mode and reverse-power-flow mode must be analyzed with First Harmonic Analysis (FHA) using first harmonic approximation. The simplified diagram of the resonant tank is given in Figure 2-4.
The nomenclature for Figure 2-4 is as follows:
Vprim (TTPLPFC_VBUS) | Voltage input at primary side |
Lrp | Primary side resonant inductor |
Crp | Primary side resonant capacitor |
NCLLLC | Turns ratio of the transformer |
Lm | Magnetizing inductor |
Vsec | Voltage output at secondary side |
Lrs | Secondary side resonant inductor |
Crs | Secondary side resonant capacitor |
RL | Effective load seen with FHA on the secondary output |
Note here the effective RL is accounted for as where RL_dc is the DC resistive load at the output.
Referring to secondary side quantities on the primary side,
Using KCL and KVL, the gain equation can be written as Equation 1.
Similarly, for the reverse power flow, the circuit can be simplified as shown in Figure 2-6, and the gain can be written as Equation 2.
Equation 1 and Equation 2 are used in the following section to study the voltage gain based on the parameters selected for the design.