Bidirectional MOSFET Switch Circuit With Body Bias Leakage Control

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Solution Overview

Problem

Conventional bidirectional power switch circuits face challenges in reducing ON resistance and OFF state subthreshold leakage currents, especially in high voltage applications, where high W/L aspect ratio MOSFETs increase layout area, gate capacitance, and switching time, while also requiring lower leakage currents for precision applications.

Innovation Solution

The implementation of sourcing and sinking switchable current sources at the Gate, Body, and Source terminals of bidirectional power switch devices, combined with resistors, to dynamically control voltage drops and reduce ON resistance and OFF state leakage currents, using a configuration that includes multiple switchable current sources and resistors to manage the operation of MOSFETs in both ON and OFF states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If high W/L aspect ratio MOSFETs are used to lower ON resistance and provide higher current capability, then current capability is improved, but layout area increases and OFF leakage current increases

Engineering Contradiction:

Improvecurrent capabilityVSAvoidlayout area

Core Design Contradiction:

PowerVSArea of stationary object

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the body terminal voltage of the MOSFETs using switchable current sources. By changing the body voltage parameter, the threshold voltage of the MOSFET is modulated, enabling low ON resistance without requiring high W/L aspect ratios, thus reducing layout area while maintaining current capability.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If high W/L aspect ratio MOSFETs are used to lower ON resistance, then ON resistance is reduced, but OFF state subthreshold leakage current increases

Engineering Contradiction:

ImproveON resistanceVSAvoidOFF state leakage current

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The patent uses parameter changes by dynamically controlling the body terminal voltage through switchable current sources. In the ON state, the body voltage is adjusted to lower the threshold voltage and reduce ON resistance. In the OFF state, the body voltage is adjusted to increase the threshold voltage and suppress subthreshold leakage current, thus resolving the contradiction between low ON resistance and low OFF leakage.

Inventive Principle:

Principle #35Parameter changes

3Power

If high W/L aspect ratio MOSFETs are used to provide higher current capability, then current capability is improved, but switching speed decreases due to increased gate capacitance

Engineering Contradiction:

Improvecurrent capabilityVSAvoidswitching speed

Core Design Contradiction:

PowerVSSpeed

Solution Approach 1:

The patent applies parameter changes by using switchable current sources to dynamically adjust the body terminal voltage. This allows the MOSFET to achieve high current capability with moderate W/L aspect ratios, thereby reducing gate capacitance and improving switching speed while maintaining the required current capability.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If larger area MOSFETs are used for high voltage applications, then voltage blocking capability is improved, but layout area increases and integration becomes more difficult

Engineering Contradiction:

Improvevoltage blocking capabilityVSAvoidlayout area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent uses parameter changes by dynamically controlling the body terminal voltage of the MOSFETs. This allows high voltage blocking capability to be achieved with smaller area devices by modulating the threshold voltage through body biasing, thus reducing layout area and improving integration for high voltage applications.

Inventive Principle:

Principle #35Parameter changes

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 reduces the overall area and power consumption of bidirectional power switch circuits, enhances switching speed, and maintains low OFF state leakage currents, making them more suitable for high voltage applications without the need for additional circuit blocks like charge pumps or amplifiers, thus improving integration and performance.

Implementation Method 1

In the OFF state, the switchable current sources are operated to apply a reverse bias voltage across the first and second source to body diodes

Methodology Applied

Scientific EffectReverse bias:

Implementation Method 2

In the ON state, the switchable current sources are operated to apply a forward bias voltage across the first and second source to body diodes

Methodology Applied

Scientific EffectForward bias:

Data Source

PatentEP4380052A1Bidirectional power switch circuit

Publication Date: 2024.06.05 NXP USA INC

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Figure 3a~3b

AI summary

The disclosure relates to improvements in bidirectional power switch circuits. Example embodiments include a bidirectional power switch, BPS, circuit (200) comprising: first and second terminals (203, 204); first and second MOSFETs (201, 202, 501, 502) connected in series between the first and second terminals (203, 204) and comprising respective first and second source to body diodes (Dsb, Dsb1, Dsb2); first and second power supply rails (VDD, VEE); first, second, third, fourth and fifth switchable current sources (IDD1-3, SD1-3, IEE1-2, SE1-2); first and second resistors (Rbs, Rgs); and a BPS switching controller (206) configured to control operation of the BPS circuit (200) between a BPS ON state in which the first and second terminals (203, 204) are connected and a BPS OFF state in which the first and second terminals (203, 204) are disconnected.