Dynamic Current Limit Circuit for Transient Load Spikes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fixed current limits in power supply chips are inadequate for applications requiring varying current levels, such as GPRS and WiFi modules, leading to potential system failures due to excessive stress or costly capacitance requirements for transient currents.
Innovation Solution
A current limit control circuit with an output current sampling module, voltage comparators, a logic control module, and a capacitor charging/discharging module that dynamically adjusts output current based on threshold voltages to manage high and low current outputs, ensuring safe and stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a fixed current limit is configured to be high to provide transient current for signal transmission, then the transient current requirement is met, but the chip and peripheral devices are subject to great stress during normal operation
Solution Approach 1:
The patent implements a dynamic current limit control circuit that adjusts the current limit threshold in real-time based on operational state. The circuit includes a comparator that compares a reference voltage with a feedback voltage representing the actual current, and a control module that dynamically modifies the current limit threshold accordingly. This allows the system to provide high transient current when needed while automatically reducing the current limit during normal operation to protect the chip and peripheral devices.
2Reliability
If a fixed current limit is configured to be low to ensure chip safety, then the chip is protected from stress, but the power supply cannot provide sufficient transient current for signal transmission
Solution Approach 1:
The dynamic current limit control circuit continuously monitors the operational state through voltage comparison and adjusts the current limit threshold in real-time. When transient current is required (detected through voltage threshold comparison), the circuit automatically raises the current limit to allow high current output. During normal operation, it maintains a lower current limit to ensure chip safety, thus resolving the contradiction between protection and performance.
3Duration of action of moving object
If a large output capacitance is used to provide transient current for several seconds, then the transient current duration is extended, but the system's loop stability design becomes extremely challenging
Solution Approach 1:
The patent changes the control parameter from fixed current limit to dynamically adjustable current limit threshold. By modifying the current limit parameter in real-time based on operational state detection, the system can provide extended transient current duration without requiring excessive output capacitance. This parameter change approach simplifies the loop stability design while achieving the desired transient current characteristics.
Data Source
AI summary
A current limit control circuit and a switched-mode power supply chip incorporating the current limit control circuit are disclosed. The current limit control circuit includes an output current sampling module, a first voltage comparator module, a hysteresis comparator module, a logic control module, a capacitor charging/discharging module and a current limit control module. The capacitor charging/discharging module is configured to charge/discharge a capacitor and thus change its output voltage, and the hysteresis comparator module is configured to produce a current limit control signal which allows the switched-mode power supply to output a high current for a specified period of time. Upon elapse of the period, the power transistor is controlled to cause a low current to be output. This ensures that the demand of a load for a transient current is satisfied while ensuring safe and stable operation of the chip for a long time.