LDO Regulator Using Charge Pump for Low Dropout
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Solution Overview
Problem
Conventional linear voltage regulators require a significant voltage difference between input and output, making it difficult to convert voltages like 5 V to 3.3 V, and existing low drop-out (LDO) regulators are large in size.
Innovation Solution
An LDO regulator design incorporating a P-channel field effect transistor, an N-channel field effect transistor, a voltage feedback circuit, and a charge pump, where the charge pump maintains a constant gate-controlled voltage for the N-channel transistor, balancing the output voltage by adjusting the drive voltage of the P-channel transistor, thereby stabilizing the output without increasing transistor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a P-channel MOSFET is used in the LDO regulator to reduce voltage drop and improve efficiency, then the voltage regulation performance is improved, but the transistor size must be increased to achieve a low threshold voltage when driving with low supply voltage
Solution Approach 1:
The patent divides the single P-channel MOSFET into two transistors: a first P-channel MOSFET for voltage regulation and a second N-channel MOSFET for drive voltage supply. This segmentation allows each transistor to be optimized independently, reducing the size requirement of the main regulation transistor while maintaining performance.
Solution Approach 2:
The second N-channel MOSFET acts as an intermediary device that provides the necessary drive voltage to the first P-channel MOSFET. This intermediary transistor enables the main transistor to operate with lower threshold voltage requirements, thereby reducing its size without compromising regulation performance.
2Stability of the object's composition
If conventional linear voltage regulators are used to ensure stable voltage regulation, then the output voltage stability is improved, but the input voltage must be at least 2-3 V higher than the output voltage
Solution Approach 1:
The patent changes the operating parameters of the regulation system by using a P-channel MOSFET with dynamically controlled gate voltage. This allows the voltage drop to be reduced from the conventional 2-3V to just the threshold voltage plus a small overhead, significantly improving energy efficiency while maintaining stable output regulation.
Solution Approach 2:
The operational amplifier provides continuous feedback control to adjust the gate voltage of the P-channel MOSFET, ensuring stable output voltage regulation. This feedback mechanism compensates for variations in input voltage and load conditions, maintaining regulation stability with minimal voltage drop.
3Ease of operation
If the transistor size is increased to reduce threshold voltage for low supply voltage operation, then the drive capability is improved, but the device area and integration density are reduced
Solution Approach 1:
The patent segments the drive function from the regulation function by using a separate second N-channel MOSFET. This allows the first P-channel MOSFET to be smaller since it only needs to provide regulation, while the second transistor provides the necessary drive capability through charge pumping, achieving both goals with reduced total area.
Data Source
AI summary
A low drop-out (LDO) regulator including a first operational amplifier, a first transistor, a second transistor, a voltage feedback circuit and a charge pump is disclosed. Each of the first transistor and the second transistor is coupled between supply voltage and an output voltage. The first operational amplifier outputs a first gate-controlled voltage to turn the first transistor on or off. A second gate-controlled voltage is provided to the second transistor to turn it on or off. The charge pump makes the second gate-controlled voltage equal to the sum of the output voltage, a threshold voltage of the second transistor and a drive voltage of the second transistor. The voltage feedback circuit provides a feedback voltage to the first operational amplifier. The first gate-controlled voltage is positively correlated to the feedback voltage. The first transistor is a P-channel field effect transistor; the second transistor is an N-channel field effect transistor.