Voltage Regulator Soft-Start Circuit Using Capacitor Charging
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Solution Overview
Problem
Conventional voltage regulators with soft-start circuits experience increased inrush current due to stepwise voltage increases, which can be mitigated but result in larger circuit areas, compromising efficiency.
Innovation Solution
A voltage regulator with a soft-start circuit incorporating a constant current circuit, a capacitor, and switch circuits to gradually raise the reference voltage, reducing inrush current and maintaining stability post-start-up, while a cascode circuit enhances noise and ripple resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the reference voltage is increased in a stepwise manner with fewer stages, then the soft-start circuit area is reduced, but the inrush current increases
Solution Approach 1:
The patent changes the voltage increase pattern from stepwise to continuous by using a capacitor that charges smoothly over time. The reference voltage increases continuously rather than in discrete steps, which suppresses inrush current while maintaining a compact circuit design with fewer resistor stages.
2Object-generated harmful factors
If the number of resistor stages is increased to reduce voltage increase per step, then the inrush current is suppressed, but the soft-start circuit area increases
Solution Approach 1:
The patent transitions from a discrete stepwise voltage increase (resistor-based) to a continuous charging process (capacitor-based). This phase transition in the voltage ramp mechanism allows for smooth inrush current suppression without requiring multiple resistor stages, thus reducing circuit area.
Solution Approach 2:
The patent replaces the mechanical/resistive stepwise voltage division system with an electrodynamic capacitor charging system. The capacitor naturally provides smooth voltage ramping through its charging characteristic, eliminating the need for multiple resistor stages and reducing overall circuit complexity and area.
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 allows for a compact soft-start circuit that gently raises the reference voltage, effectively suppressing inrush currents and improving stability and noise resistance, thereby optimizing voltage regulation.
Implementation Method 1
a capacitor (Css) connected to an output terminal of the reference voltage circuit (52). When a start-up signal is input, the capacitor (Css) is charged through the reference voltage circuit (52), so that a reference voltage (Vss) rises gently with time.
Implementation Method 2
a constant current circuit (51); a reference voltage circuit (52) driven by a current of the constant current circuit (51)
Data Source
AI summary
Provided is a voltage regulator including a soft-start circuit having a small area and capable of suppressing an inrush current by causing a reference voltage circuit to rise gently with time. In the soft-start circuit, a capacitor is connected to an output of a reference voltage circuit driven by a constant current of a constant current circuit, and hence the soft-start circuit can raise a reference voltage gently to prevent an inrush current with a small area. After the end of a soft-start period, the constant current circuit is disconnected, and the reference voltage circuit is driven by a power source. Thus, the operation becomes stable.