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Magnetics for the TIDM-02021 11 kW single-stage onboard charger
TIDM-02021 is a Texas Instruments reference design for an 11 kW three-phase bidirectional onboard charger built on a single-stage series resonant dual active bridge, plus a 2.5 kW, 14 V low voltage DC-DC. A single-stage resonant charger asks more of its magnetics than a two-stage one, and the public design guide does not publish their values. This page explains what they have to do and what decides their design.
What the board is
- Three-phase, single-stage series resonant dual active bridge (SS-SRDAB) from the AC grid to the high voltage battery. Single-stage means the AC-DC conversion and the isolation happen in one conversion stage, not that a DC link is present between two of them.
- 175 to 264 V AC per phase, 450 to 850 V battery, 11 kW, 97.5 % peak efficiency.
- Resonant frequency 150 kHz, operating range 80 to 250 kHz, with ZVS and ZCS.
- Grid to vehicle, vehicle to grid and vehicle to load.
- Low voltage DC-DC (LDC) of 2.5 kW with a 14 V output, controlled by the same MCU.
Source: Texas Instruments TIDM-02021 product page and design guide TIDUFF5, checked November 2026. The magnetic component values are in the preliminary design files, which TI releases on request.
The magnetics on the board
| Part | What the design files publish | What decides the design |
|---|---|---|
| Series resonant transformer | Isolation between the grid side and the battery, inside a resonant stage at 150 kHz nominal | Volt-seconds that follow the line voltage, a 450 to 850 V battery window and insulation to the mains |
| Resonant inductor Lr, discrete or in the leakage | 150 kHz resonance with an 80 to 250 kHz operating range | Value and tolerance of Lr, and losses across a 3 to 1 frequency range |
| LDC transformer | 2.5 kW to a 14 V output | Secondary current of about 180 A DC, termination losses, and a turns ratio for the full battery range |
| LDC output inductor | 14 V output | Inductance at about 180 A of DC bias |
| Three-phase EMI chokes | EMI filter block in the system diagram | Common and differential mode attenuation measured on the real charger |
What the public documents do not say
The public design guide does not show the per-phase circuit, so it does not say whether there is one resonant transformer per phase or one shared transformer, whether Lr is a separate inductor or the transformer leakage, or how the LDC is connected. Each of those choices changes the number of magnetics, their power rating and their insulation. We confirm them from your schematic before we design.
Why the magnetics are harder than in a two-stage charger
In a two-stage charger, a PFC stage feeds a stable DC link and the isolated stage sees a constant voltage. In a single-stage charger there is no separate DC link. The voltage applied to the transformer follows the rectified line voltage, so the flux swing and the current change continuously over each mains period. Core loss has to be integrated over the line cycle, not computed at one operating point, and the peak flux at the line peak sets the core size.
The resonant tank adds a second constraint. The resonant frequency depends on the square root of Lr times Cr, so a 10 % error in Lr moves it by about 5 %. Over an 80 to 250 kHz operating range, the AC resistance of the windings and the core loss also change by a large factor, and the design has to hold its temperature at the worst point of that range, not at 150 kHz.
If you change the design
A 400 V only battery, a different resonant frequency or a liquid cold plate instead of air changes the turns ratio, the tank values or the thermal design of every magnetic. A different LDC output voltage, 48 V instead of 14 V, cuts the secondary current by more than three and changes the transformer completely.
What to send us
The reference number, your schematic or the per-phase circuit, battery voltage range, resonant frequency and tank values, LDC output voltage, cooling, isolation standard and the quantities you expect.
We aim to send an engineering answer with a first design proposal inside 24 hours, then 4 to 8 weeks from an agreed design to a prototype, subject to raw material stock. No minimum order quantity.
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