EV Power Control Relay Layout for Capacitor Pre-Charging
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Solution Overview
Problem
Existing power control devices for electric vehicles require a large number of relays, leading to increased body size, which is undesirable.
Innovation Solution
A power control device with a simplified configuration using five relays, including a system main relay, auxiliary relay, and pre-charge relay, to pre-charge capacitors while minimizing relay usage, allowing direct connection between the high-voltage battery and DCDC converters, and enabling simultaneous pre-charging of multiple capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of relays are used in the power control device, then the pre-charging function and system control are achieved, but the body size increases
Solution Approach 1:
The patent combines multiple relay functions into integrated control circuits. The first and second relays in the system main relay are controlled by a unified control signal from the control unit, merging control logic. The auxiliary relay integrates the pre-charging control function with the main relay structure, reducing the total relay count while maintaining pre-charging capability through coordinated switching of the fifth relay based on voltage detection.
Solution Approach 2:
The system main relay and auxiliary relay are designed to perform multiple functions. The system main relay not only controls the main power connection but also enables pre-charging through its auxiliary relay component. The control unit universally manages both relays using a single control signal, making the relay system multi-functional and reducing overall component count.
2Volume of stationary object
If the relay count is minimized to reduce body size, then space utilization is improved, but the complexity of relay configuration and control increases
Solution Approach 1:
The control unit acts as an intermediary that manages the complex coordination between relays. It generates control signals that automatically manage the switching sequences of the first, second, and fifth relays, abstracting the complexity from the hardware configuration. The voltage detection unit serves as an intermediary sensor that monitors capacitor voltage and provides feedback to the control unit, enabling automatic pre-charging control without complex manual configuration.
Solution Approach 2:
The patent implements feedback control through the voltage detection unit that continuously monitors the voltage across the capacitor connected to the auxiliary relay. When the detected voltage reaches a predetermined threshold, the control unit automatically turns off the fifth relay, stopping the pre-charging process. This feedback mechanism simplifies the control logic by using automatic voltage-based decision-making rather than complex timing or manual control sequences.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces the overall size of the power control device by minimizing relay count and allows efficient pre-charging of capacitors, thereby optimizing space utilization.
Implementation Method 1
a smoothing capacitor provided, provided between the system main relay and the inverter, and connected to the first power line and the second power line
Implementation Method 2
a pre-charge relay, which is a fifth relay provided between a high-voltage end of the second DCDC converter and the smoothing capacitor
Data Source
AI summary
A power control includes: an inverter for converting power from the high-voltage battery and outputting to the motor; a first DCDC converter for stepping down the power from the high-voltage battery and outputting to the auxiliary load; a second DCDC converter connected in parallel with the to the first DCDC converter; first and second power lines connecting positive and negative electrode terminals, respectively, of the high-voltage battery and the inverter; first and second relays in the first and second power lines, respectively; a smoothing capacitor, between the system main relay and the inverter, and connected to the first and second power lines; third and fourth relays, between the positive and negative electrode terminals, respectively, of the high-voltage battery and the second DCDC converter; and a fifth relay between a high-voltage end of the second DCDC converter and the smoothing capacitor.