Bidirectional MOSFET Switch Circuit With Dynamic Body Biasing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bidirectional power switch (BPS) circuits face challenges in high precision applications due to high ON resistance, large device size, and increased OFF state leakage current, especially in high voltage domains, which affect switching speed and integration on chips.
Innovation Solution
The proposed BPS circuit employs switchable current sources and resistors to dynamically control the gate, body, and source terminals, creating forward or reverse bias voltages to reduce ON resistance and OFF state subthreshold leakage currents, using P-channel or N-channel MOSFETs in a common source configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high W/L aspect ratio is used to lower the ON resistance and provide higher current capability, then the current capability is improved, but the device size increases and the OFF leakage current increases
Solution Approach 1:
The patent dynamically changes the body terminal voltage parameter to control the threshold voltage of the MOSFET. By adjusting the body bias voltage, the device can operate with lower ON resistance without requiring a permanently high W/L aspect ratio, thus reducing the device size while maintaining current capability.
Solution Approach 2:
The invention introduces dynamic control of the body terminal voltage that can be adjusted based on operating conditions. This dynamic adjustment allows the MOSFET to optimize its performance characteristics (ON resistance, OFF leakage, current capability) in real-time without being constrained by a fixed high W/L aspect ratio.
2Power
If a high W/L aspect ratio is used to lower the ON resistance, then the ON resistance is reduced, but the switching speed decreases
Solution Approach 1:
The patent changes the body terminal voltage parameter dynamically to control threshold voltage. This allows the MOSFET to achieve low ON resistance during conduction while enabling faster switching by adjusting the body bias during transition periods, avoiding the need for a permanently high W/L aspect ratio that would slow switching.
Solution Approach 2:
The body bias circuit prepares the MOSFET for switching transitions by pre-adjusting the body terminal voltage. This preliminary action reduces the threshold voltage before turn-on and increases it before turn-off, enabling faster switching speeds without requiring a high W/L aspect ratio that would increase capacitance and slow switching.
3Power
If a high W/L aspect ratio is used, then the ON resistance is lowered, but the OFF state subthreshold leakage current increases
Solution Approach 1:
The patent dynamically changes the body terminal voltage parameter to control the threshold voltage. During OFF state, the body bias is adjusted to increase the threshold voltage, which exponentially reduces the subthreshold leakage current. This allows the device to achieve low ON resistance during conduction while maintaining very low OFF state leakage without requiring a high W/L aspect ratio.
4Reliability
If larger area HV device switches are used for high voltage applications, then the voltage blocking capability is improved, but the layout area penalty increases and integration becomes more difficult
Solution Approach 1:
The patent uses dynamic body biasing to control the threshold voltage and channel characteristics. This allows the use of smaller area MOSFETs in high voltage applications by optimizing the electric field distribution and channel control through body terminal voltage adjustment, reducing the required layout area while maintaining voltage blocking capability.
Solution Approach 2:
The invention introduces dynamic control of the body terminal voltage to optimize the MOSFET performance for high voltage operation. This dynamic adjustment allows smaller devices to achieve the required voltage blocking capability by controlling the depletion region and threshold voltage, reducing the layout area penalty for HV applications.
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 switch size, lowers power dissipation, and improves switching speed while maintaining low leakage currents, making it suitable for high voltage applications without requiring additional circuit blocks like HV level shifters.
Implementation Method 1
configuring and using sourcing and sinking switchable current sources at Gate, Body and Source Terminals of the BPS device switch along with added resistors to generate the necessary voltage drops to realise the techniques
Implementation Method 2
first and second MOSFETs connected in series between the first and second terminals and comprising respective first and second source to body diodes
Data Source
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.