Pre-Charging Circuit for Intermediate Capacitor with Constant Power Dissipation
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Solution Overview
Problem
Existing battery systems face challenges in efficiently charging intermediate circuit capacitors due to high initial current flow, leading to prolonged switch-on times and increased power losses, which necessitate larger and more expensive resistors or constant current sources causing inefficient power usage.
Innovation Solution
A method and circuit arrangement that utilize a current source with an adjustment circuit to maintain constant power loss throughout the charging process by monitoring voltage and adjusting current, employing a zener diode and resistor combination or transistor dividing circuit to regulate the current source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a pre-charge resistor is used to charge the intermediate circuit capacitor, then the initial current is limited, but the charging time is prolonged and power losses increase
Solution Approach 1:
The patent applies a dynamic current control strategy where the current through the pre-charge resistor is continuously adjusted during the charging process. The control unit increases the current as the capacitor voltage approaches the target voltage, transforming the static resistance approach into a dynamic process that maintains optimal power transfer throughout charging, thereby reducing total charging time while managing peak currents
Solution Approach 2:
The invention changes the operating parameters of the pre-charge resistor by dynamically adjusting its effective resistance through current control. By varying the current parameter over time based on capacitor voltage feedback, the system optimizes the trade-off between current limiting and charging speed, achieving faster charging without excessive power losses
2Productivity
If a constant current source is used to charge the intermediate circuit capacitor, then the charging gradient is constant, but power losses are high due to high initial voltage
Solution Approach 1:
The patent implements a feedback control mechanism where the voltage across the intermediate circuit capacitor is continuously monitored and used to adjust the current from the pre-charge unit. This closed-loop control ensures that current is increased only when appropriate, matching power delivery to actual charging needs and minimizing energy losses while maintaining high charging rates
Solution Approach 2:
The system transitions from a static constant current approach to a dynamic current profile that adapts to the charging state. By making the current parameter time-dependent and voltage-dependent, the system achieves optimal productivity throughout the charging process while reducing overall power losses compared to maintaining constant high current
3Loss of time
If the pre-charge resistor value is reduced to shorten charging time, then power losses in the resistor increase, requiring larger and more expensive components
Solution Approach 1:
The invention changes the effective resistance parameter dynamically during operation rather than using a fixed low resistance value. By controlling the current through the resistor as a variable parameter that increases with capacitor voltage, the system achieves fast charging without the continuous high power losses that would require oversized, expensive resistor components
Solution Approach 2:
The patent transforms the static resistor design problem into a dynamic control problem. Instead of selecting a resistor value that must handle peak power continuously, the system dynamically adjusts current to achieve similar charging speed with much lower average power dissipation, allowing the use of smaller, more cost-effective components
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
This approach shortens the pre-charging duration, ensures constant power dissipation, and allows for cost-effective and reliable construction by maintaining a consistent power loss, optimizing the charging process and reducing the need for oversized components.
Implementation Method 1
the current is adjusted so that a constant power loss is generated in the current source during the entire charging process
Implementation Method 2
employing a zener diode and resistor combination or transistor dividing circuit to regulate the current source
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A method for charging an intermediate circuit capacitor in a precharging unit is described. In this case, the intermediate circuit capacitor is charged via a current source, the current of which is adjusted in such a manner that a constant power loss is produced in the current source during the entire charging operation. The invention also proposes a circuit arrangement having a battery (1) which is connected to a current source (2) which is connected to an intermediate circuit capacitor (4) via a switch (3). An adjusting circuit (5) is arranged in parallel with the current source (2) and can be used to adjust the current for charging the intermediate circuit capacitor (4) in such a manner that a constant power loss is produced in the current source (2) during the entire charging operation.