The biggest difference between a fuel filler flap and a charging flap is their frequency and time of use. While a fuel filler flap is opened and closed maybe once or twice a week on average, it happens on a daily basis with a charging flap. The charger is unplugged at the start of a trip and plugged back in at the end of the day. And if you are on the road a lot or take longer trips, you will also have to open the flap somewhere along the way for recharging.
First impressions count
In this context, another aspect plays a vital role. With an internal combustion engine vehicle, the first contact is always opening the door and getting into the driver’s seat. That is the reason why car manufacturers go to great lengths to make it a positive experience – after all, there is no second chance for a good first impression! This is different with electric cars: In this case, the driver should first disconnect the charging cable before getting into the car, otherwise it is going to be somewhat of a short ride. This obviously turns the charging flap into the vehicle’s calling card. Car manufacturers have recognized this fact and are trying to make the charging experience as positive as possible, especially for high-end vehicles.
First and foremost, it includes ensuring that the charging port meets vehicle safety requirements. To protect users from electric shock, the port must be waterproof.
Firm connections are decisive
In addition, the plug must remain connected during the charging process. After all, there is hardly anything more annoying for electric car drivers than approaching a presumably fully charged vehicle only to find that the plug has become loose or someone else has unplugged it and the car is only partially charged. This makes the locking of the charging plug one of the most important parts of the charging port. Electronics integrated in the actuator control this process and enable the current status to be queried.
However, disconnecting the plug during the charging process is not just annoying for the driver. It can also damage the charging electronics and cause an arc, destroying the connector plug or causing skin burns. Therefore, a functional safety rating of ASIL applies to the charger; the requirements for the application being addressed may vary between a QM product and a product with “ASIL B ready” as a prerequisite.
Key components
All charging ports require at least two electronic components that are not required in vehicles with an internal combustion engine: an actuator for locking and a plug sensor.
The charging plug is securely locked by the movement of a metal pin inside the charging socket via an electric actuator. To control the motors that move such pins, TDK offers various integrated Arm Cortex M3 motor controller ICs through its HVC-4x family. They are capable of controlling DC, BLDC, and stepper motors while connected to a LIN bus (automotive version). Six motor outputs enable the control of up to three independent DC motors, e.g. for locking the plug and the charging flap or for electrically opening the charging flap. Seven general-purpose IO pins can be used to control warning and charging LEDs and to interface with various sensors, such as the sensor that ensures the locking pin is actually inserted into the plug.
This safety check can also be implemented using a Hall effect sensor. To do so, the TDK portfolio includes several 3D position sensors, e.g. Micronas HAC 373x or HAC 3930. They can measure either the rotation of a gear (in combination with a solenoid) or the linear movement of the locking pin (together with an attached solenoid). Both are ASIL B ready according to ISO 26262 and therefore suitable for applications that need to meet ASIL B requirements. Additionally, both sensors support PWM and SENT interfaces for communicating with the integrated electronics. They feature a small leaded transistor package (TO92UF) with integrated protection capacitors, which enables cost-efficient lead frame assembly and thus more compact actuators.
Locking of the charging plug guarantees safe and secure charging and helps protect the electronics.
It almost looks like a fuel filler flap, but there are a few significant differences.
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