In-rush Current Controller for Semiconductor Switches
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Solution Overview
Problem
Existing semiconductor switch control technologies face challenges in accurately managing the slew rate and in-rush current during the turn-on period, leading to inefficiencies and variations across different switch sizes.
Innovation Solution
An in-rush current controller is introduced, comprising an amplifier, reference current source, feedback capacitor, and auxiliary feedback capacitor, which controls the switch control current to manage the slew rate and in-rush current by sourcing or sinking current to the switch control port, using a differential amplifier for robustness and a class-A amplifier to buffer differently sized switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional switch control is used, then the switch can be turned on, but the slew rate and in-rush current cannot be accurately controlled
Solution Approach 1:
The patent implements feedback control by sensing the output voltage at the output node and feeding it back to the amplifier control port. The feedback capacitor couples the output node to the amplifier control port, creating a feedback loop that automatically adjusts the switch control current based on the actual output voltage, thereby achieving accurate slew rate and in-rush current control.
Solution Approach 2:
The patent introduces an amplifier as an intermediary device between the control signal and the switch control port. The amplifier converts small control currents into larger switch control currents, providing precise control while isolating the control circuit from the power switch. This intermediary approach enables accurate control without requiring complex direct control circuitry.
2Speed
If high in-rush current is allowed during turn-on, then fast switching is achieved, but peak currents become excessive and harmful
Solution Approach 1:
The feedback capacitor continuously monitors the output voltage during the turn-on transition and adjusts the amplifier control current accordingly. As the output voltage changes during switching, the feedback mechanism dynamically controls the charging current to the switch gate, ensuring fast switching while preventing excessive peak currents that could damage the circuit.
Solution Approach 2:
The control circuit dynamically adjusts the switch control current during the turn-on period rather than using a fixed current. The amplifier modulates the current based on real-time feedback from the output voltage, enabling the system to optimize the balance between switching speed and peak current limitation throughout the switching transition.
3Measurement precision
If the control circuit is made highly accurate, then slew rate and in-rush current are precisely controlled, but the circuit becomes sensitive to noise and supply variations
Solution Approach 1:
The feedback loop enables the control circuit to self-correct for noise and supply voltage variations. By continuously monitoring the actual output voltage and comparing it with the desired trajectory, the circuit automatically compensates for disturbances, making the precise control robust against noise and supply variations without requiring additional complex filtering or protection circuits.
4Adaptability or versatility
If a single control circuit is designed, then it works for one switch size, but it cannot accommodate differently sized switches
Solution Approach 1:
The amplifier-based control circuit with feedback is designed to be universal and can accommodate switches of different sizes. The feedback mechanism automatically adapts to the specific characteristics of whichever switch is connected, and the amplifier provides sufficient drive capability for various gate capacitances, maintaining control accuracy across different switch sizes without requiring circuit redesign.
Data Source
AI summary
An in-rush current controller to turn-on a semiconductor output switch is described. The output switch is arranged in series with an output capacitor. The switch comprises a switch control port for controlling an output current and an output voltage. The controller comprises an amplifier to source or sink a switch control current to or from the switch control port, wherein the switch control current is dependent on an amplifier control current at an amplifier control port. The controller comprises a reference current source to provide a reference current at the amplifier control port, subject to a control signal indicating that the output switch is to be turned on. Furthermore, the controller comprises a feedback capacitor to provide a feedback current at the amplifier control port in dependence of a variation of the output voltage.