Comparative Analysis of OBC System Circuits of Tesla Model 3 and M7

Hello everyone, today's topic is an in-depth analysis of the circuit structure of the electric vehicle OBC (On-board Charger) system.

I will take Tesla Model 3 and QM7 as examples to explain their OBC circuit design in detail, especially the working principle of PFC circuit and DC-DC conversion circuit .

Whether you are an electric vehicle enthusiast or someone who works in technology, today's content will help you better understand the complexity of the OBC system and its application in different models.

Before explaining the specific models, let's take a look at the core components of OBC. Whether it is Tesla Model 3 or Q7, their OBC systems have some common components:

AC input interface: accepts AC power from an external power source (home or charging station).

EMC filter: eliminates electromagnetic interference in the current and ensures current stability.

PFC (Power Factor Correction) circuit: corrects the power factor, reduces reactive power, and improves energy utilization efficiency.

DC-DC Converter: Converts AC power into DC power, suitable for battery charging.

Control circuit: responsible for managing and monitoring the voltage, current and temperature during the charging process to ensure safety and efficiency.

Next, we will take Tesla Model 3 and M7 as examples to discuss their OBC system designs respectively.

Power specification: The OBC power of Tesla Model 3 is 11 kW (three-phase) or 7.2 kW (single-phase) , which is mainly used in fast charging scenarios.

Tesla's OBC system uses a highly efficient PFC circuit design. The core function of the PFC circuit is to improve the power factor and synchronize the current and voltage of the AC power to reduce reactive power and improve overall energy utilization. In the Model 3's OBC, the PFC circuit can increase the power factor to close to 1, thereby ensuring more efficient use of grid resources.

The AC power input from the power grid first passes through the EMC filter to eliminate electromagnetic interference and ensure current stability. Then the power factor is corrected through the PFC circuit, and the current and voltage phases are synchronized before being input into the DC-DC converter. At this stage, the PFC circuit not only improves the charging efficiency, but also reduces the burden on the power grid, especially when using three-phase AC power, which can effectively reduce grid interference and energy loss.

Tesla Model 3 uses a soft-switching DC-DC converter, a design that reduces switching losses and improves power conversion efficiency. The DC-DC converter converts the corrected AC power into stable DC power and transmits it to the battery for charging.

软开关技术： 软开关DC-DC技术通过减少电压和电流的瞬态变化来减少开关过程中的能量损耗。 相比传统的硬开关设计，软开关能够显著降低热量产生，提升高功率下的转换效率。 这对于特斯拉Model 3来说尤为重要，因为其支持三相11 kW的高功率充电，需要更高效的电能转换。

The Model 3's OBC system is highly integrated, and all modules are managed uniformly through Tesla's software system. The control circuit can intelligently manage the entire charging process, including monitoring and automatic adjustment of voltage, current, and temperature, to ensure safety and efficiency in various charging scenarios.

The OBC system of the Wenjie M7 supports a charging power of up to 11 kW, is compatible with three-phase AC power, has a bidirectional charging function, and supports V2L (Vehicle to Load) function.

PFC (Power Factor Correction) Circuit Analysis: The PFC circuit design of the Wenjie M7 is also very efficient, similar to the PFC circuit of the Tesla Model 3, but its bidirectional function is a highlight. The OBC system of the Wenjie M7 not only supports the input of current (i.e. charging the battery), but also can output power in reverse in inverter mode to power external devices.

When charging the battery, the PFC circuit optimizes the use of power to ensure that the power utilization rate is maximized during the charging process. When reverse power is supplied, the PFC circuit also participates in current regulation, converting DC power into AC power that meets the needs of external devices. This design enables the M7 to not only charge the battery, but also provide emergency power for household appliances or other electric devices when necessary.

The QNEX M7 uses a bidirectional DC-DC converter, which allows it to not only convert external AC power into DC power that can be used by the battery, but also convert the DC power in the battery into AC power that can be used by external devices.

Features of the bidirectional design : In normal charging mode, the DC-DC converter works similarly to the unidirectional OBC, converting the AC power after PFC processing into DC power for charging. In inverter mode, the DC-DC converter can invert the DC power in the battery into AC power and power other devices through an external interface. This bidirectional design is very practical for outdoor camping or power outage emergencies, reflecting the practicality of the M7 in multiple scenarios.

The OBC control system of the Wenjie M7 is not only responsible for conventional charging management, but also needs to deal with the complexity of bidirectional energy flow. The system can intelligently identify the current power demand and automatically switch between charging and inverter modes. Through the control circuit, the OBC system can ensure that the current, voltage and temperature are within the safe range during bidirectional charging and discharging.

Comparison of OBC systems between Tesla Model 3 and QM7

The PFC circuits of both are designed to improve the efficiency of power utilization, but the PFC circuit of the M7 can also work effectively in discharge mode due to its bidirectional design. In contrast, the PFC circuit of the Tesla Model 3 is more focused on unidirectional efficient charging.

Tesla Model 3 uses a unidirectional DC-DC converter, which focuses on efficiently converting AC power into DC power, while the Wenjie M7 uses a bidirectional DC-DC converter, which can achieve bidirectional energy flow and power external devices. Therefore, the Wenjie M7 is more flexible in application scenarios and can provide V2L functions, while the Tesla Model 3's OBC system is more optimized in charging efficiency and power conversion.

Tesla Model 3's OBC system is mainly aimed at fast charging needs, especially in public charging stations in cities or high-power charging environments at home, where charging efficiency and speed are its core advantages. The OBC system of the M7 can not only charge the vehicle quickly, but also provide power for external devices. The application scenarios are more diverse, especially suitable for outdoor activities or users who need mobile power.

In summary, the OBC systems of Tesla Model 3 and QM7 have their own unique designs:

Tesla Model 3: It uses a highly efficient PFC circuit and soft-switching DC-DC converter, focusing on unidirectional and efficient charging, suitable for high-performance electric vehicles that require fast charging.

Wenjie M7: It has a bidirectional OBC design and supports V2L function. The PFC and DC-DC circuits can handle bidirectional current flow, making the application scenarios more flexible, especially suitable for users who need to power external devices.

Through today's explanation, everyone should have a deeper understanding of the OBC system circuit design of Tesla Model 3 and M7. If you have more questions or are interested in the OBC design of other models, we can discuss more details in the following time. Thank you!