Switching Regulator Soft Start Circuit Suppresses In-Rush Current
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Solution Overview
Problem
Conventional soft start circuits for switching regulators either increase circuit complexity or result in high sample variation of in-rush current, particularly affecting small-capacity power supplies like coin-cell batteries, due to excessive in-rush currents during initial driving.
Innovation Solution
A switching regulator with a soft start circuit that includes a peak detector, comparator, and counter to generate a soft start signal based on a system clock, which adjusts a ramp voltage by varying a resistor, allowing for a short initial driving time without increasing circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an analog soft start circuit is used to suppress in-rush current, then the in-rush current is suppressed, but the circuit complexity increases and degree of circuit integration is reduced
Solution Approach 1:
The patent replaces the analog soft start circuit (mechanical/electrical system with physical components like capacitors and current sources) with a digital soft start circuit using a counter, clock signal, and digital logic. This substitution reduces circuit complexity and improves integrability while maintaining the in-rush current suppression function through digital timing control.
Solution Approach 2:
The patent changes the control parameter from analog voltage/current levels to digital time-based control. By using a counter that counts clock cycles, the soft start duration is precisely controlled through parameter N (number of clock cycles), replacing the need for analog component values and reducing sensitivity to component variations.
2Object-affected harmful factors
If an analog soft start circuit is used to suppress in-rush current, then the in-rush current is suppressed, but the sample variation of in-rush current increases
Solution Approach 1:
The digital circuit replaces analog components (capacitors, current sources) that suffer from manufacturing tolerances and temperature drift with digital logic elements (counter, clock generator) that have high precision and stability. This eliminates the sample variation problem inherent in analog circuits.
Solution Approach 2:
The digital soft start circuit uses the system's own clock signal to generate the soft start timing, making it self-contained and independent of external components. The counter automatically generates the precise timing sequence without requiring external calibration or adjustment, ensuring consistent performance across samples.
3Object-affected harmful factors
If a digital soft start circuit is used to suppress in-rush current, then the in-rush current is suppressed, but the turn-on procedure time increases
Solution Approach 1:
The patent implements a dynamic soft start duration that adapts to system conditions. The counter-based timing allows for flexible adjustment of the soft start period (parameter N) to balance between in-rush current suppression and turn-on speed, optimizing the trade-off between protection and responsiveness.
Solution Approach 2:
The soft start circuit uses periodic clock signals to generate precise timing intervals. This periodic action enables accurate control of the soft start duration through the counter, allowing the system to complete the soft start process in a predetermined, optimized time frame rather than using extended conservative timing.
4Object-affected harmful factors
If a digital soft start circuit is used to suppress in-rush current, then the in-rush current is suppressed, but the sample variation of in-rush current becomes higher when the oscillation clock fluctuates
Solution Approach 1:
The patent incorporates a feedback mechanism where the counter monitors the clock signal cycles and automatically adjusts the soft start timing based on the actual clock frequency. This feedback ensures that the soft start duration remains consistent even when clock fluctuations occur, maintaining uniform in-rush current suppression across different operating conditions and samples.
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 suppresses in-rush currents within a short time, reducing circuit complexity and extending the life of small-capacity power supplies by minimizing the initial peak current, while maintaining high integration and reducing the turn-on time of the power supply.
Implementation Method 1
a peak detector configured to receive a clock signal and detect a peak voltage of the clock signal
Implementation Method 2
a comparator configured to generate a soft start signal for controlling a soft start of the switching regulator based on a result of comparing a level of the peak voltage of the clock signal to a preset reference voltage level
Implementation Method 3
a ramp voltage generation unit configured to generate a ramp voltage by adjusting a resistance of a variable resistor based on the soft start signal
Data Source
AI summary
Disclosed herein is a switching regulator with a soft start circuit for suppressing an in-rush current. The switching regulator includes a peak detector configured to receive a clock signal and detect a peak voltage of the clock signal, a comparator configured to generate a soft start signal for controlling a soft start of the switching regulator based on a result of comparing a level of the peak voltage of the clock signal to a preset reference voltage level, a counter configured to switch a state of the soft start signal at a time point when a preset soft start time arrives, and a ramp voltage generation unit configured to generate a ramp voltage by adjusting a resistance of a variable resistor based on the soft start signal.