Bootstrapped PMOS Switch Circuit for Constant Gate-Source Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing transistor switch embodiments face challenges in delivering optimal control signals to PMOS transistors, leading to unpredictable on-resistance and performance degradation due to varying gate-to-source voltages when static control signals are used.
Innovation Solution
A bootstrapped switch circuit that provides predetermined constant gate-to-source voltages to PMOS transistors, independent of the input signal, using a voltage-controlled voltage source to maintain consistent voltage levels for turning the transistors on and off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If static control signal voltages are used to turn PMOS transistors on and off, then the control is simple, but the gate-to-source voltage varies during operation causing unpredictable on-resistance and performance degradation
Solution Approach 1:
The patent applies dynamics by transitioning from static control signal voltages to dynamic bootstrapped control signals. The bootstrapped circuit generates time-varying control signals that actively track and compensate for the varying source voltages during switch operation, ensuring the gate-to-source voltage remains constant despite signal transitions. This dynamic approach maintains predictable on-resistance and optimal switch performance throughout the operating cycle.
Solution Approach 2:
The patent changes the control parameter from fixed static voltages to dynamically adjusted voltages generated by the bootstrapped circuit. By modifying the control signal parameters to include active feedback and voltage tracking, the system maintains constant gate-to-source voltage differential, thereby stabilizing the on-resistance and eliminating performance degradation associated with static control signals.
2Device complexity
If the gate voltage is static, then the control circuit is simple, but the varying gate-to-source voltage generates varying on-resistance degrading switch performance
Solution Approach 1:
The patent introduces a bootstrapped circuit as an intermediary between the control signal source and the PMOS transistor gates. This intermediary circuit actively generates the appropriate control voltages by tracking the source voltage and maintaining the required gate-to-source differential. The bootstrapped circuit serves as a mediator that translates simple control inputs into the complex time-varying voltages needed to maintain stable on-resistance, thereby decoupling control simplicity from performance reliability.
3Ease of manufacture
If PMOS transistors are used with back gate connected to source, then the device structure is standard, but body diodes conduct and require series arrangement to prevent conduction
Solution Approach 1:
The patent converts the potentially harmful effect of body diodes into a beneficial feature by using the inherent diode structure to simplify the circuit topology. Instead of requiring series transistor arrangements to block body diode conduction, the design accepts the body diodes and configures the bootstrapped control signals to utilize their natural conduction characteristics, thereby eliminating the need for complex series arrangements while maintaining standard PMOS device structure.
Data Source
AI summary
A bootstrapped switch circuit can include a switch transistor, having a drain configured as an input terminal to receive an input signal, and a voltage-controlled voltage source, configured to provide predetermined constant voltages between a gate and a source of the switch transistor in response to a control signal received at a control terminal. The predetermined constant voltages can include a first predetermined constant voltage to turn on the switch transistor and pass the input signal to the source and a second predetermined constant voltage to turn off the switch transistor. The first and second predetermined constant voltages can be independent of the magnitude of a signal passed to the source of the switch transistor based on the input signal at the drain.