Current Limit Boost Converter Stability
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Solution Overview
Problem
Current boost converter current limit circuits are prone to variations due to resistance changes, impacting stability and power delivery, especially during over-current conditions, and often require separate feedback loops that can disable slope compensation.
Innovation Solution
A current-mode feedback control circuit is implemented in the boost converter, which compares the boosted voltage to a reference voltage, controls the switch based on this comparison, and sets the supply voltage of the amplifier based on a current limit, reducing dependence on resistance variations and maintaining stability through integrated over-current protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional current limit circuits are used in boost converters, then the circuit can operate with simple structure, but the current limit settings are prone to variations due to resistance changes, impacting stability and power delivery
Solution Approach 1:
The patent changes the parameter used for current limit sensing from voltage-based (prone to resistance variations) to current-mode sensing. By using current mirrors and transconductance amplifiers, the system directly senses and controls current, eliminating the impact of resistance variations on current limit accuracy, thus improving reliability without requiring complex additional components
Solution Approach 2:
The patent replaces traditional voltage-based current sensing (analogous to mechanical measurement) with direct current-mode feedback using transconductance amplifiers and current mirrors. This substitution eliminates the intermediate voltage conversion step that is susceptible to resistance variations, providing more direct and accurate current control
2Reliability
If separate feedback loops are added for over-current protection, then current limit control can be improved, but slope compensation may be disabled and device complexity increases
Solution Approach 1:
The patent merges the over-current protection function with the existing voltage feedback loop by using the same transconductance amplifier and feedback network. The current limit is enforced through the supply voltage control of the amplifier rather than through a separate current sensing loop, combining multiple functions into a single integrated control path that maintains slope compensation
Solution Approach 2:
The transconductance amplifier and feedback network serve multiple functions simultaneously: voltage regulation, over-current protection, and slope compensation. By making the protection circuit multi-functional rather than dedicated to a single purpose, the system achieves reliable over-current protection without requiring additional separate feedback loops
3Power
If amplifier supply voltage is increased to handle higher power, then power delivery capability is improved, but voltage overshoot increases during transient conditions
Solution Approach 1:
The patent uses negative feedback through the transconductance amplifier to regulate the amplifier's supply voltage. When over-current conditions are detected, the feedback mechanism automatically reduces the supply voltage to the amplifier, which in turn reduces the voltage overshoot while maintaining the current limit. This dynamic feedback control allows the system to deliver high power when needed while preventing voltage overshoot during transients
Data Source
AI summary
Certain aspects of the present disclosure generally relate to a boost converter. The boost converter generally includes an inductor coupled to a first node, a first switch coupled between the first node and a reference node for the boost converter, and a feedback control circuit. The feedback control circuit may include a first input coupled to the first node, a second input coupled to a terminal of the first switch, and an output coupled to a control input of the first switch. The feedback control circuit may include a first amplifier having a first input coupled to the first input of the feedback control circuit and a second input coupled to a first reference voltage source. The feedback control circuit may also include a second amplifier having a first input coupled to a second reference voltage source and an output coupled to a power supply node of the first amplifier.