Vehicular Compressor Power Input Circuit for Two-Stage Inrush Limiting
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Solution Overview
Problem
Conventional power input circuits for inverter-integrated electric compressors experience excessive inrush current when a DC power source is turned on, leading to peak current values exceeding predetermined limits, particularly during the charging of smoothing capacitors.
Innovation Solution
A power input circuit with a filter circuit, subsequent-stage and preceding-stage inrush current limiting circuits, and switch circuits that adjust the voltage of power switching elements' control electrodes to control and limit inrush current, utilizing current detection resistors, current limiting control elements, and capacitors to manage current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter circuit with smoothing capacitor is added to suppress noise, then noise suppression capability is improved, but excessive inrush current is generated when the DC power source is turned on
Solution Approach 1:
The power input circuit is divided into two stages: a first power switching element (Q4) for controlling current from the DC power source to the filter circuit, and a second power switching element (Q2) for controlling current from the filter circuit to the load. Each stage has its own inrush current limiting circuit, allowing independent control of inrush current at each stage while maintaining noise suppression functionality.
Solution Approach 2:
The inrush current limiting circuits are activated before the main power switching elements are fully turned on. The control circuits for the inrush current limiting circuits start charging the smoothing capacitor through controlled current paths before the main power switches are activated, preventing excessive inrush current while still allowing the capacitor to charge for noise suppression.
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 circuit effectively suppresses excessive inrush current, prevents peak current values from exceeding limits, and reduces current vibration phenomena, ensuring smooth current operation and protection of components.
Implementation Method 1
a current detection resistor that detects current with voltage generated at both ends by inrush current
Implementation Method 2
a capacitance element connected between the control electrode and one of the main electrodes of each of the current limiting control elements
Data Source
AI summary
Provided is a power input circuit capable of limiting excessive inrush current generated when a DC power source is turned on and a smoothing capacitor is charged. The power input circuit includes an EMC filter circuit 7 having a smoothing capacitor 12, a subsequent-stage power switching element Q2, a switch circuit 23 that turns on/off the power switching element Q2, a subsequent-stage inrush current limiting circuit 9 that limits inrush current by adjusting the voltage of a control electrode of the power switching element Q2, a preceding-stage power switching element Q4 that conducts/blocks a conduction path between the EMC filter circuit 7 and a battery 2, and a preceding-stage inrush current limiting circuit 10 that limits inrush current when the battery 2 is turned on by adjusting the voltage of the gate of the power switching element Q4.