Bootstrap Bias Voltage Generator for N-Channel Linear Regulator
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Solution Overview
Problem
Traditional P-Channel linear regulators face difficulties in supporting lower input voltages due to insufficient gate turn-on voltage, making them less effective in modern electronic systems with lower core supply voltages and increased complexity, while n-channel transistor-based regulators require a sufficient bias voltage that can be challenging to provide, especially when the input voltage is lower than the output voltage.
Innovation Solution
A bias voltage generator is integrated into the DC-to-DC switched-mode voltage converter using bootstrap circuitry, which re-uses existing components to generate a bias voltage for the n-channel linear regulator, ensuring sufficient gate drive voltage is provided, even in low input voltage scenarios, by coupling a bias diode and capacitor to the intermediate node of the bootstrap circuit, allowing for efficient operation without an additional power source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional P-Channel linear regulators are used, then high power supply rejection ratio and low output noise performance are achieved, but insufficient gate turn-on voltage occurs at lower input voltages
Solution Approach 1:
The patent inverts the traditional approach by using an n-channel transistor instead of a P-Channel transistor as the pass element in the linear regulator. This inversion allows the regulator to operate with lower input voltages while maintaining high PSRR and low output noise performance, as n-channel transistors have lower threshold voltages suitable for low-voltage applications.
Solution Approach 2:
The patent changes the electrical parameters of the regulator by switching from P-Channel to n-channel transistor technology, which fundamentally alters the voltage requirements and operating characteristics. This parameter change enables the regulator to function effectively at lower input voltages where traditional P-Channel regulators fail due to insufficient gate turn-on voltage.
2Ease of operation
If n-channel transistor-based regulators are used, then sufficient operation at lower input voltages is achieved, but bias voltage generation becomes challenging when input voltage is lower than output voltage
Solution Approach 1:
The patent merges the bias voltage generation function with the existing DC-to-DC switched-mode voltage converter by integrating a bias voltage generator into the converter circuit. This integration allows the bias voltage to be generated from the switching nodes of the DC-to-DC converter, eliminating the need for separate bias supply circuitry and reducing overall system complexity.
Solution Approach 2:
The DC-to-DC switched-mode voltage converter serves a dual purpose: it not only provides the main power conversion function but also generates the bias voltage required by the n-channel linear regulator through its internal switching nodes. This self-service approach allows the converter to support the regulator's bias requirements without external assistance.
3Ease of operation
If external bias supply is added to n-channel linear regulator, then sufficient gate drive voltage is provided, but system complexity and component count increase
Solution Approach 1:
The DC-to-DC switched-mode voltage converter is designed to perform multiple functions: primary power conversion and bias voltage generation for the linear regulator. By making the converter universal and multi-functional, the patent eliminates the need for separate bias supply components, thereby reducing system complexity while ensuring adequate gate drive voltage for the n-channel regulator.
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 solution enables efficient operation of n-channel linear regulators in low voltage applications by providing a bias voltage that is higher than the input voltage, reducing the need for external bias supplies and improving power supply rejection ratio (PSRR) and noise characteristics, while maintaining system efficiency and simplicity.
Implementation Method 1
A bias voltage generator is integrated into the DC-to-DC switched-mode voltage converter using bootstrap circuitry
Implementation Method 2
coupling a bias diode and capacitor to the intermediate node of the bootstrap circuit
Data Source
AI summary
Apparatus and methods for a bias supply circuit to support power supply including a switched-mode voltage converter cascaded with an n-channel-based linear regulator are provided. In an example, a cascaded power supply system can include a switched-mode DC-to-DC power converter, including an input voltage node, a first stage output voltage node, and a bootstrapped floating bias voltage node, and a linear regulator circuit. The linear regulator circuit can include an n-channel field-effect transistor (NFET) pass transistor, including a drain terminal coupled to the first stage output voltage node, a gate terminal, and a source terminal configured to provide a second-stage output voltage, and a gate driver circuit, including a driver output coupled to the gate terminal of the NFET pass transistor, and a high side supply node configured to receive a bias voltage generated from the bootstrapped floating bias voltage node.