PUMBAA power supply for electric vehicles PPS550

Highly integrated electrical integration

Automotive grade design, ASIL compatible

Support V2L, V2G, V2V and other multi-scene requirements

Smaller and lighter design, stable technical performance and high efficiency

Liquid-cooled cooling method, fast heat dissipation, dustproof and low noise

Multiple protection functions such as EMC, voltage resistance, insulation, vibration and electrical protection

Allocation and control of high-voltage devices of the whole vehicle through the whole vehicle control unit to ensure the safety performance of each system

● Powerful hardware configuration
The main components adopt automotive components to improve product reliability;

● Efficient operation
Controller efficiency can be up to 98%, high power density, applications more flexible;

● Reliable protective design
The overall protection level is high and the working temperature range is wide, thus it can better adapt to all kinds of harsh application environment.

Introduction: When you plug an electric vehicle (EV) into a charging pile, how does alternating current (AC) transform into the direct current (DC) required by the battery? The "unsung hero" behind this critical conversion process is the EV On-Board Charger (OBC). As the "bridge" connecting external charging infrastructure and the battery, the performance of the OBC directly determines charging efficiency, driving safety, and range. This article will fully decode the technical mysteries of this "charging core" by exploring its definition, functions, working principles, and technological trends.

I. OBC Definition: The EV's "Charging Translator"

OBC (On-Board Charger), literally "on-board charger," is a core component in an EV's electric drive system responsible for converting AC to DC. At its essence, it is a "dedicated power converter" that processes AC (e.g., 220V home chargers or 380V commercial fast chargers) output by charging piles into the high-voltage DC (e.g., 400V/800V) required by the battery through rectification, filtering, and voltage transformation. It also dynamically adjusts charging parameters based on battery conditions (e.g., State of Charge (SOC), temperature) to ensure safe and efficient charging.

In simple terms, the OBC acts like a "translator":

​·Input: AC from external charging piles;

​·IProcessing: Converts AC to high-voltage DC via power electronics;

​·IOutput: Stable DC tailored to the battery’s charging needs, enabling "precise charging."

（AC charging）

II. Core Functions of OBC: Dual Safeguards for Charging Efficiency and Safety

The OBC’s functions can be summarized as "three core capabilities + two supporting systems," covering the entire charging process from start to finish (see Figure 1).

2.1 Function 1: Power Conversion—"Precise Translation" from AC to DC

The OBC’s primary task is converting AC to DC, involving three steps: rectification → filtering → voltage transformation.

​·IRectification: Converts AC (e.g., 220V/50Hz) into pulsating DC (with significant harmonics) using a diode rectifier bridge.

​·IFiltering: Removes harmonics via inductors (L) and capacitors (C) to output smooth DC (ripple ≤5%).

​·IVoltage Transformation: Adjusts voltage via a DC-DC converter (e.g., LLC resonant topology) to match the charging requirements of individual battery cells (e.g., 4.2V/cell).

​Technical Detail: Take Tesla Model 3’s OBC as an example. Using SiC MOSFET + LLC resonant topology, it converts 380V AC to 400V DC with a conversion efficiency of up to 97% (compared to 85%-90% for traditional silicon-based IGBT solutions).

2.2 Function 2: Charging Control—"Intelligent Manager" for Dynamic Adjustment

The OBC dynamically adjusts charging current and voltage based on battery conditions (SOC, temperature) and user needs (fast/slow charging) to prevent overcharging, overheating, or undercharging. Its control logic includes:

​Constant Current (CC) Charging: At low SOC (<20%), a high constant current (e.g., 100A) is applied for rapid charging.

​Constant Voltage (CV) Charging: As SOC approaches full (>80%), current is reduced (e.g., 20A) to maintain a constant voltage (e.g., 4.2V/cell).

​Temperature Compensation: Charging current is reduced at high temperatures (>45°C) to avoid thermal runaway; at low temperatures (<-10°C), the battery is preheated before charging to improve efficiency.

2.3 Function 3: Safety Protection—"Guardian" of the Charging Process

The OBC is equipped with multiple protection mechanisms to ensure safety:

​·IOvervoltage/Undervoltage Protection: Automatically cuts output if input voltage exceeds 480V (commercial fast charging) or drops below 90V (home chargers).

​·IOvercurrent Protection: Triggers a fuse (1500A fast-acting) if charging current exceeds the rated value (e.g., 200A).

​·IShort-Circuit Protection: Disconnects power within 1ms if an output short circuit is detected (current spikes 10x).

​·IInsulation Monitoring: Continuously checks the insulation resistance of the high-voltage circuit (must be ≥100MΩ) to prevent leakage risks.

（DC charging)

III. OBC Working Principle: Four-Step Conversion from AC to DC

The OBC’s working principle can be simplified into a closed-loop process: ​Input → Rectification → Filtering → Voltage Transformation → Output.

3.1 Input: Receiving External AC

The OBC connects to charging piles via charging interfaces (e.g., CCS, GB/T) to receive AC. Voltage and frequency vary by region (e.g., 220V/50Hz for Chinese homes, 230V/50Hz for European homes, 380V/50Hz for commercial fast chargers).

3.2 Rectification: Converting AC to Pulsating DC

A diode rectifier bridge (e.g., three-phase full-bridge rectifier) converts AC to pulsating DC (with irregular waveforms and significant harmonics). For example, 380V three-phase AC becomes ~513V pulsating DC after rectification (V_DC = 1.35 × line voltage).

3.3 Filtering: Eliminating Harmonics for Smooth DC

An LC filter (inductor + capacitor) removes high-frequency harmonics (e.g., 10kHz–1MHz) from pulsating DC, outputting smooth DC with ripple ≤5% (e.g., 510V).

3.4 Voltage Transformation: Adjusting Voltage to Match Battery Needs

A DC-DC converter (e.g., LLC resonant topology, phase-shifted full-bridge topology) steps the smooth DC up or down to the battery’s required voltage (e.g., 400V/800V). For instance:

·Tesla Model 3’s OBC steps down 510V DC to 400V to charge its 400V battery system.

·Porsche Taycan’s OBC supports 800V high voltage, directly charging its 800V battery.

3.5 Output: Stable Power Supply with Dynamic Adjustment

The final DC is transmitted to the battery via a high-voltage bus. Meanwhile, the OBC continuously monitors the battery’s status via the Battery Management System (BMS) and dynamically adjusts output current/voltage (e.g., 100A during fast charging, 20A during slow charging).

(EV charging pile/电动汽车充电桩)

IV. Technological Evolution of OBC: From "Inefficient" to "Ultra-Fast Charging" Revolution

Early OBCs, limited by silicon-based devices (e.g., IGBTs), had efficiencies of only 85%-90% and did not support fast charging (power ≤7.2kW). With the adoption of wide-bandgap devices (e.g., SiC MOSFETs) and high-frequency topologies, OBC performance has achieved "leapfrog improvements":

4.1 Efficiency Improvement: From 85% to Over 97%

SiC MOSFETs have 50% lower conduction losses and higher switching frequencies (up to 100kHz) than silicon IGBTs, pushing OBC efficiency beyond 97% (e.g., Tesla Model 3’s OBC achieves 97.5% efficiency).

4.2 Power Upgrade: From 7.2kW to Over 350kW+

High-frequency topologies (e.g., LLC resonance) reduce the size of magnetic components, enabling higher power. Examples include: [Specific examples omitted for brevity]

4.3 Volume and Cost Optimization: Integrated Design

Through "chip-level integration" (e.g., integrating OBC with DC-DC converters into a single module), OBC volume is reduced by 30% and cost by 20% (e.g., BYD Han EV’s OBC occupies just 0.05m³).

 (On-Board Charger working scenario)

V. Future Trends: OBC’s "Intelligentization" and "Integration"

As EVs evolve into "intelligent mobility terminals," OBC functions and performance will continue to upgrade. Three key trends merit attention:

(On-Board Charger frame)

VI:Integration: "Multi-Domain Fusion" Unified Design

6.1 Traditional OBCs are standalone components (bulky and costly). Future OBCs will achieve integration through:

​·OBC + DC-DC Integration: Merging the on-board charger with a DC-DC converter into a single module (e.g., Tesla Model 3’s "two-in-one" charging module), reducing volume by 30% and cost by 20%.

​·OBC + BMS Integration: Embedding battery status monitoring (e.g., SOC, temperature) to reduce communication latency with the BMS (from 100ms to 10ms).

6.2 High Efficiency: Popularization of 800V High-Voltage Platforms and Wide-Bandgap Devices

800V high-voltage platforms (e.g., Porsche Taycan, XPeng G9) will become mainstream, requiring OBCs to support higher voltages (800V–1000V). Meanwhile, wide-bandgap devices (SiC/GaN) will push efficiency beyond 98% (e.g., Huawei DriveONE OBC achieves a peak efficiency of 98.5%).

6.3 Intelligence: Co-Evolution with Autonomous Driving

OBCs will deeply integrate with Autonomous Driving Systems (ADS) to enable "predictive charging":

​·Road Condition Prediction: Using ADS navigation data (e.g., a fast charger 3km ahead) to preheat the battery (improving charging efficiency).

​·Load Coordination: Dynamically adjusting charging power based on autonomous driving needs (e.g., temporarily reducing current to prioritize motor power during overtaking).

​·OTA Upgrades: Updating OBC control algorithms via cloud (e.g., optimizing fast-charging strategies) to continuously enhance performance.

Conclusion

The EV OBC is the "core hub" connecting external charging to the battery. Its technological breakthroughs directly determine charging efficiency, driving safety, and range. From early "inefficient converters" to today’s "ultra-fast charging smart terminals," the evolution of the OBC has not only accelerated EV adoption but also become a key enabler of energy-efficient utilization under the "dual carbon" goals.

In the future, with the deep integration of integration, high-efficiency, and intelligent technologies, the OBC will further unlock the potential of EVs, making "charging as fast as refueling" a reality.