Bidirectional CMOS Switch with Diode Bridge for High Voltage Control
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Solution Overview
Problem
CMOS switches face challenges in operating beyond the range of supply and ground potentials, prone to parasitic diode conduction, and require external components like charge pumps and level shifters for high voltage applications.
Innovation Solution
A bidirectional integrated CMOS switch using a NMOS/PMOS pair, diode bridge, and control circuitry on a Silicon-on-Insulator (SOI) chip, eliminating parasitic diodes and enabling operation with arbitrary terminal voltages using standard low-voltage logic, without charge pumps or external devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If standard CMOS switches are used for high voltage applications, then switching capability is provided, but parasitic diode conduction occurs and gate voltage control becomes complex requiring external components
Solution Approach 1:
The invention separates the high voltage switching function from the low voltage control function by introducing level shifter circuits that translate low voltage logic signals into appropriate high voltage gate control signals. This segmentation allows the CMOS switch to handle high voltages while being controlled by standard low voltage logic, eliminating the need for complex external gate drive circuits.
Solution Approach 2:
The invention introduces level shifter circuits as intermediary components between the low voltage control logic and the high voltage switch terminals. These level shifters act as mediators that convert control signals to the appropriate voltage levels needed for gate control, simplifying the overall system architecture while maintaining proper switching operation.
2Adaptability or versatility
If CMOS switches operate beyond supply rail voltages, then voltage range is extended, but parasitic diode conduction causes unwanted current flow
Solution Approach 1:
The invention prevents parasitic diode conduction by ensuring proper body terminal voltage control through level shifters. The level shifters maintain the body terminal at the appropriate potential relative to the source and drain, preventing the formation of forward-biased parasitic diodes even when switch terminals operate beyond supply rails. This preliminary prevention eliminates unwanted current paths before they can occur.
Solution Approach 2:
The invention changes the voltage parameters of the body terminal through level shifter circuits, maintaining it at a controlled potential independent of the high voltage swing at the switch terminals. This parameter control ensures that the voltage differences across parasitic diodes remain reverse-biased, preventing conduction while allowing the main channel to operate at extended voltage ranges.
3Ease of operation
If external components like charge pumps and level shifters are used, then high voltage gate control is achieved, but device integration and cost increase
Solution Approach 1:
The invention merges the level shifter functionality directly into the CMOS switch structure, integrating the voltage translation circuits within the same device package. This integration eliminates the need for separate external charge pumps and level shifter components, reducing system complexity while maintaining the ability to control high voltage switches with low voltage logic signals.
Solution Approach 2:
The invention creates a universal CMOS switch structure that can operate across multiple voltage domains by integrating multi-functional level shifter circuits. These integrated circuits provide both signal buffering and voltage level translation in a single unit, allowing the switch to be controlled by standard logic levels while handling high voltage signals, thereby reducing the need for multiple specialized external components.
4Ease of manufacture
If body diodes are present in CMOS devices, then standard manufacturing is used, but current flows through body instead of channel causing latch-up or failure
Solution Approach 1:
The invention changes the voltage parameters applied to the body terminal through integrated level shifters, maintaining it at a controlled potential that keeps parasitic diodes reverse-biased. This parameter control prevents current diversion through the body region, eliminating latch-up conditions and improving reliability while maintaining standard CMOS manufacturing processes.
Solution Approach 2:
The level shifter circuits act as intermediary voltage control elements that isolate the body terminal from high voltage transients at the switch terminals. By mediating the voltage at the body terminal, these circuits prevent forward biasing of parasitic diodes, thereby preventing harmful current flow through the body while allowing the main channel to conduct properly.
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
Enables efficient bidirectional switching of high voltage loads at arbitrary voltages, preventing parasitic diode conduction and integrating seamlessly with other CMOS circuitry, reducing costs and failure rates.
Implementation Method 1
Diodes D0, D1, D2 and D3 form a diode bridge which causes current to flow through the switch in only one direction, from Node C to Node D, regardless of the polarity of the voltages on terminals A and B
Implementation Method 2
CMOS circuits use a combination of p-channel (PMOS) and n-channel (NMOS) metal oxide semiconductor field effect transistors (MOSFETs) to implement logic gates and switches. The composition of a PMOS transistor creates low resistance between its source and drain contacts when a low gate voltage is applied and high resistance when a high gate voltage is applied
Data Source
AI summary
A bidirectional integrated CMOS switch is provided which is capable of switching voltages beyond the range of the supply and ground potentials. The switch is composed of NMOS and PMOS transistors as the switch conductor path, a diode bridge, and control circuitry to turn the switch on and off by means of low voltage logic, regardless of the voltages on the switch terminals. The device and method of the invention enables the switching of high voltage loads operating at arbitrary or floating voltages relative to the low voltage power supply and ground, and provides on/off control of the switch with ordinary low voltage logic levels. The invention provides bidirectional switching without conducting through the parasitic body diodes of the CMOS devices.