Switched-Capacitor MOSFET Gate Control for Stable Regulator Output
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Solution Overview
Problem
Conventional voltage regulator circuits face challenges in maintaining a stable output voltage while minimizing quiescent current when supplying loads that experience large amplitude current spikes, as solutions like large capacitance filtering or increased quiescent current are not feasible in integrated circuit applications due to area and power consumption concerns.
Innovation Solution
Incorporating switched capacitor circuits coupled to the gate terminal of a MOSFET device in the voltage regulator circuit, which selectively charge capacitors and impose voltage drops on the control voltage in response to control signals, allowing for efficient handling of transient current spikes without increasing quiescent current or occupying excessive integrated circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large capacitance filtering capacitor is coupled between the output node and ground to smooth the regulated output voltage, then the output voltage stability is improved, but the integrated circuit area occupied increases significantly
Solution Approach 1:
The patent introduces switched capacitor circuits as intermediary elements between the error amplifier output and the MOSFET gate. These switched capacitors (C1, C2) act as mediators that store and release charge to counteract current spikes, thereby stabilizing the output voltage without requiring a large filtering capacitor at the output node. The switched capacitors are controlled by clock signals to charge during low current periods and discharge during high current spike periods.
2Reliability
If the output stage of the error amplifier is biased with a larger quiescent current, then the ability to handle transient current spikes is improved, but the power consumption increases
Solution Approach 1:
The patent employs periodic switching action through clock signals (CLK1, CLK2) that control the switched capacitor circuits. The capacitors are charged and discharged in periodic cycles synchronized with the load current variations. During current spike events, the capacitors discharge to provide additional current; during normal operation, they are recharged. This periodic action enables the regulator to handle transient spikes without maintaining a continuously high quiescent current.
Solution Approach 2:
The switched capacitor circuits perform preliminary action by pre-charging capacitors C1 and C2 during normal operating conditions before current spikes occur. The capacitors are maintained at ready states through periodic charging from the error amplifier output, so that when current spikes occur, the pre-charged capacitors can immediately discharge to compensate, rather than waiting for the error amplifier to respond to the voltage droop.
3Stability of the object's composition
If the MOSFET device sources additional current during current spikes, then the output voltage stability is improved, but the control circuit complexity increases
Solution Approach 1:
The patent utilizes feedback through the error amplifier that continuously monitors the output voltage and compares it against a reference voltage. When current spikes cause voltage droop, the feedback mechanism detects this change and adjusts the control voltage to the MOSFET gate accordingly. The switched capacitor circuits are integrated into this feedback loop, where the error amplifier's output drives both the MOSFET gate and the switched capacitors, creating a coordinated response that stabilizes the output voltage.
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
This approach effectively stabilizes the output voltage while minimizing power consumption and area usage, making it suitable for integrated circuits by allowing the MOSFET device to source additional current during spikes without the need for large filtering capacitors or increased quiescent current.
Implementation Method 1
a first switched capacitor circuit coupled to the gate terminal and configured to selectively charge a first capacitor with a first current and impose a first voltage drop on the control voltage
Data Source
AI summary
A voltage regulator receives a reference voltage and generates a regulated voltage using a MOSFET having a gate terminal configured to receive a control voltage. A charge pump receives the regulated voltage and generates a charge pump voltage in response to an enable signal and a clock signal generated in response to the enable signal. The voltage regulator further includes a first switched capacitor circuit coupled to the gate terminal and configured to selectively charge a first capacitor with a first current and impose a first voltage drop on the control voltage in response to assertion of the enable signal. The voltage regulator also includes a second switched capacitor circuit coupled to the gate terminal and configured to selectively charge a second capacitor with a second current and impose a second voltage drop on the control voltage in response to one logic state of the clock signal.