Switching Power Supply Inrush Current Restriction
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Solution Overview
Problem
Switching power supply devices experience unstable output voltage during mode switches due to high inrush currents when transitioning between buck, buck-boost, or boost operations, particularly during engine cranking when input voltage drops significantly.
Innovation Solution
A switching power supply device with a control circuit that compares input voltage to thresholds and performs an inrush current restriction operation by gradually increasing the gate voltage of switching elements, using a soft turning on control to limit high inrush currents during mode switches, thereby stabilizing output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching power supply device switches operation mode between buck and boost operations to stabilize output voltage during input voltage variations, then the output voltage stability is improved, but high inrush current flows to switching elements during mode transition causing output voltage instability
Solution Approach 1:
The control circuit detects the operation mode transition in advance and activates the inrush current restriction operation before the switching element turns on. This preliminary action prevents the harmful inrush current from flowing by preparing the restriction mechanism ahead of time, thus maintaining output voltage stability during mode transitions.
Solution Approach 2:
The control circuit acts as an intermediary between the operation mode switch and the switching element. It monitors the transition state and controls the switching element's turn-on timing and current flow, mediating the harmful effect of inrush current while preserving the beneficial output voltage stabilization function.
2Speed
If the switching element turns on quickly to output input voltage through the inductor during operation switch, then the response speed is improved, but substantially high inrush current flows causing output voltage to become unstable
Solution Approach 1:
The control circuit dynamically adjusts the switching element's turn-on characteristics during mode transitions. By making the turn-on process controllable and adaptive rather than fixed, the system can balance response speed with inrush current restriction, maintaining output voltage stability while still responding quickly to operation mode changes.
Solution Approach 2:
The control circuit changes the operating parameters of the switching element during mode transitions, specifically controlling the gate voltage application and current flow characteristics. This parameter adjustment allows the switching element to turn on with restricted inrush current while maintaining adequate response speed for output voltage stabilization.
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 effectively restricts high inrush currents during mode switches, improving the stability of output voltage across different power control operations, ensuring stable power supply to vehicular devices even during engine cranking.
Implementation Method 1
The control circuit performs an inrush current restriction operation in response to the operation switch in order to restrict a flowing of an inrush current to one of the switching elements
Data Source
AI summary
A switching power supply device includes a switching circuit and a control circuit. The switching circuit includes multiple switching elements, an inductor, and a capacitor. The control circuit compares an input voltage of the switching circuit with a predetermined threshold voltage set for an operation switch, and controls the switching circuit to perform the operation switch between at least two power control operations based on a comparison result. The at least two power control operations includes at least two of a buck operation, a buck-boost operation, or a boost operation. The control circuit further performs an inrush current restriction operation in response to the operation switch in order to restrict a flowing of an inrush current to one of the switching elements, which turns on and outputs the input voltage through the inductor in response to the operation switch.