EV DC-DC Converters

HV to LV · 12 V · 48 V · X-in-1

An EV has no alternator; the DC-DC converter keeps every controller, brake and airbag powered. If it fails, the car stops even with a full battery.

The HV-to-LV bridge: the 400 to 1,000 V traction pack feeds an isolated DC-DC converter of about 2.5 to 4 kW, which replaces the alternator and supplies a 12 V or 48 V low-voltage bus. Below, the current needed to deliver 3 kW: 250 A at 12 V, 62.5 A at 48 V and 3.75 A at 800 V. Four times the voltage means one quarter the current, so thinner wire and less copper. THE HV-TO-LV BRIDGE Traction pack 400-1,000 V DC Isolated DC-DC 2.5-4 kW replaces alternator LV bus 12 V or 48 V CURRENT TO DELIVER 3 KW OF LOAD 12 V bus 250 A 48 V bus 62.5 A 800 V bus 3.75 A Four times the voltage, one quarter the current: thinner wire, less copper.
Typical rating
2.5-4 kW
LV bus
12 V, moving to 48 V
First volume 48 V EV
Cybertruck
Companies tracked
13, 4 Chinese
Hub
Supply Chain

Finding

The standalone DC-DC converter is disappearing into integrated power units, and the move to 48 V shifts its job from charging a 12 V battery to feeding a full low-voltage network

Chinese OEMs ship the DC-DC converter, onboard charger and high-voltage distribution as one "3-in-1" box (BYD, Huawei, VMAX, Shinry), and Tesla's Cybertruck moved its whole low-voltage system to 48 V in 2023. Both trends cut parts, connectors and copper.

The converter is an isolated DC-DC stage - typically a phase-shifted full bridge or LLC resonant converter with a high-frequency transformer - rated about 2.5 to 4 kW in passenger cars and higher in trucks and buses. Galvanic isolation keeps the traction voltage off the chassis-referenced LV bus. Bidirectional units can also boost LV to HV for pre-charge or jump-start functions.

At 48 V the same power needs one quarter of the current, so harness wire shrinks and losses fall. Tesla, Rivian, GM and Hyundai are moving to 48 V; most of the industry still runs 12 V. Device choice follows voltage: SiC MOSFETs on the 800 V primary side, silicon or GaN on the low-voltage secondary, where GaN shrinks magnetics at high switching frequency. Western and Japanese suppliers include Delta, TDK, Lear, Bosch, Denso, Valeo, LG Magna and Forvia Hella; in China, VMAX, Shinry, Inovance and the OEM captive arms of BYD and Huawei lead.

Technology

Converter technologies

DC-DC converter switch technologies
TechnologyAdoption driversConstraints
SiC primary side800-1,000 V platforms, high efficiency, smaller coolingCost; shared substrate supply with inverters
GaN secondary or full stageCompact magnetics, very high efficiency at low and medium power650 V class rating; early automotive scale
Silicon MOSFET / IGBTLow cost, broad supply on 400 V platformsLarger magnetics and cooling

Roles

What the converter does

DC-DC converter functions
FunctionWhat it doesWhy it matters
LV bus supplyRegulated 12 V or 48 V from the traction packPowers ECUs, ADAS, brakes, steering, lighting, pumps
LV battery chargingMaintains the 12 V lead-acid or lithium batteryWake-up, contactor close and limp-home depend on it
IsolationGalvanic separation of HV and LV domainsElectrical safety; required by ISO 6469-3
Bidirectional transferLV to HV boost for pre-charge or backupRedundancy for safety-critical loads

Directory

DC-DC converter makers

Standalone converters and converters built into charger or power-domain units. Active companies first, then merged, acquired, exited and bankrupt ones; each company appears once per product line.

DC-DC converters: automaker in-house
CompanyProductsHQPlantsTechnologyCustomersStatus
BYD (FinDreams Powertrain)DC-DC inside the 8-in-1 e-driveChinaChinaIn-house SiC and siliconBYD, Denza, Yangwang, Fangchengbaoactive
TeslaPower conversion system: charger and DC-DC in one unit; 48 V LV bus on CybertruckUSUS, ChinaSilicon and SiCTeslaactive
DC-DC converters: suppliers
CompanyProductsHQPlantsTechnologyCustomersStatus
BoschDC-DC converters, 400 V and 800 VGermanyGermany, ChinaSilicon and SiCNot disclosedactive
Delta ElectronicsDC-DC converters and OBCsTaiwanTaiwan, China, ThailandSiC and GaNNot disclosedactive
DensoDC-DC convertersJapanJapanSiliconToyota, Lexusactive
Huawei Digital PowerPower domain module: OBC, DC-DC and power distributionChinaChinaSiC and GaNSeres (AITO), Chery (Luxeed)active
Hyundai MobisIntegrated charging control unit (ICCU): OBC plus low-voltage DC-DCSouth KoreaSouth KoreaSilicon and SiCHyundai, Kia, Genesisactive: ICCU failures drove 2024 recalls of E-GMP models
KostalDC-DC converters and onboard chargersGermanyGermany, ChinaSilicon and SiCNot disclosedactive
LearDC-DC converters in its E-Systems unitUSUS, Mexico, EuropeSiliconNot disclosedactive
Shinry TechnologiesDC-DC converters and onboard chargersChinaChinaSilicon and SiCNot disclosedactive
Toyota IndustriesDC-DC converters and onboard chargersJapanJapanSiliconToyotaactive
ValeoDC-DC converters, 400 V and 800 VFranceFrance, ChinaSilicon and SiCNot disclosedactive
VMAXOBC, DC-DC and 3-in-1 power domain unitsChinaChinaSiCLi Auto, Leapmotor, Chery, Geelyactive

Sources

Sources and scope

Scope
EV DC-DC Converters
Sources
Tesla (Cybertruck 48 V, 2023); ISO 6469-3; supplier disclosures; ElectronsX database
Updated
October 2026