Switching Variable Resistance Unit for Inrush Current Limiting
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Solution Overview
Problem
DC-DC converters in devices like mobile communication terminals experience unstable supply voltage due to high inrush currents during initial operations, which can shorten battery life and affect adjacent circuits.
Innovation Solution
A semiconductor integrated circuit with a switching variable resistance unit that adjusts resistance values based on switching current needs, using PMOS and NMOS transistors to generate variable amplitude pulses and control current flow, thereby limiting inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a voltage doubler circuit is used in a DC-DC converter, then voltage conversion capability is improved, but supply voltage becomes unstable due to high inrush current during initial operation
Solution Approach 1:
The patent applies preliminary action by generating a variable amplitude pulse before the main switching operation to progressively limit the inrush current. The pulse generating unit creates a pulse with amplitude that increases over time, allowing the switching variable resistance unit to gradually reduce its resistance value. This preliminary current limiting action prevents the sudden voltage drop that would otherwise occur during initial operation of the voltage doubler circuit, thereby maintaining supply voltage stability while enabling voltage conversion capability.
2Stability of the object's composition
If a high resistance value is used to limit inrush current, then supply voltage stability is improved, but switching current capability is reduced
Solution Approach 1:
The patent applies dynamics by implementing a switching variable resistance unit whose resistance value changes dynamically over time. The unit transitions from a high resistance state during initial operation to a low resistance state during normal operation. The variable amplitude pulse controls this transition, starting with a high amplitude that limits current to protect voltage stability, then progressively reducing the amplitude to allow higher switching currents. This dynamic resistance adjustment resolves the contradiction between maintaining voltage stability and enabling sufficient switching current capability.
Solution Approach 2:
The patent applies parameter changes by varying the resistance value of the switching variable resistance unit as a function of time. The resistance parameter is adjusted from a high initial value to a low steady-state value through control of the switching transistor's gate voltage. The variable amplitude pulse modulates the gate voltage, causing the resistance to decrease progressively. This parameter change enables the circuit to achieve both voltage stability during startup and adequate switching current capability during operation.
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 reduces inrush currents, stabilizing the supply voltage and extending battery life while minimizing the impact on adjacent circuits.
Implementation Method 1
a PMOS transistor having a source terminal that is coupled to the supply voltage input terminal and a gate terminal that receives the variable amplitude pulse
Implementation Method 2
the variable amplitude pulse of the pulse generating unit progressively increases during the period of time
Data Source
AI summary
A semiconductor integrated circuit having a switching variable resistance device with combined functions of a switching device and a variable resistance device is provided. The semiconductor integrated circuit includes a supply voltage input terminal that receives a supply voltage, a pulse generating unit that receives an input pulse and generates a variable amplitude pulse in response to the input pulse during a period of time, and a switching variable resistance unit that controls a current flowing into the supply voltage input terminal in response to the variable amplitude pulse, thereby limiting an inrush current and thus substantially reducing an temporary unstable effect on the supply voltage, which may be supplied from a power source.