Bi-Directional Switch Substrate Control for Leakage Suppression
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Solution Overview
Problem
Conventional bi-directional switches with a common drain configuration face performance degradation due to substrate voltage instability during the on-state, as the substrate is not effectively held close to ground potential, leading to increased risk of leakage current and reduced long-term reliability.
Innovation Solution
A semiconductor device with a substrate control circuit that includes a discharge circuit and a gate potential control circuit, utilizing diodes with specific forward voltage ratios to stabilize the substrate voltage, ensuring it remains close to 0V during the on-state, thereby reducing leakage current and enhancing long-term reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If back-to-back diodes are integrated with the substrate, then the substrate is protected during off-state, but the substrate voltage drifts negative during on-state due to charge confinement
Solution Approach 1:
The discharge circuit is segmented into two independent transistors (first transistor for first source, second transistor for second source) that operate independently to discharge negative charge from the substrate during on-state, preventing voltage drift while maintaining protection during off-state
Solution Approach 2:
The substrate control circuit acts as an intermediary between the back-to-back diodes and the main bi-directional switch, adding discharge transistors that mediate the substrate voltage by providing a controlled discharge path for negative charge during on-state operation
2Adaptability or versatility
If the substrate is kept floating to allow high voltage at one source, then voltage flexibility is improved, but substrate voltage control deteriorates leading to performance degradation
Solution Approach 1:
The substrate control circuit dynamically adjusts substrate voltage control based on operational state: during off-state, the back-to-back diodes provide passive protection while allowing floating substrate; during on-state, the discharge transistors actively discharge negative charge to maintain substrate near ground potential, providing adaptive voltage control
3Device complexity
If conventional discharge circuits are used without forward voltage control, then circuit simplicity is maintained, but leakage current increases due to insufficient substrate voltage holding
Solution Approach 1:
The invention changes the forward voltage parameter of diodes in the discharge circuit (using diodes with forward voltage Vf1 ≥ 1.1Vf3 or Vf1 ≥ 1.2Vf3 or Vf1 ≥ 1.5Vf3 or Vf1 ≥ 2Vf3) to ensure proper substrate voltage holding during on-state, reducing leakage current while maintaining reasonable circuit complexity
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
The proposed solution effectively stabilizes the substrate voltage, reducing leakage current and improving the long-term reliability of bi-directional switches by providing a discharge path and ensuring the substrate remains close to ground potential during switching operations.
Implementation Method 1
The substrate control circuit comprises a first diode and a second diode, a discharge circuit and a gate potential control circuit. The anode of the first diode and the anode of the second diode are connected to the semiconductor substrate.
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
In an embodiment, a semiconductor device 100, 100' comprises a main bi-directional switch 10 formed on a semiconductor substrate 2) and comprising first and second gates, a first source electrically connected to a first voltage terminal VS1, a second source electrically connected to a second voltage terminal VS2, and a common drain D and a substrate control circuit 11. The substrate control circuit (11) comprises a first diode SD1 and a second diode SD2, a discharge circuit 12 comprising a first transistor QC1 and a second transistor QC2 connected in a common source configuration to the semiconductor substrate 20, and a gate potential control circuit 13 comprising a third diode QD1 and a fourth diode QD2. The first diode SD1 has a forward voltage Vf1 and the third diode QD1 has a forward voltage Vf3, wherein Vf1 ≥ 1.1 Vf4 or Vf1 ≥ 1.2Vf4 or Vf1 ≥ 1.5Vf4 or Vf1 ≥ 2Vf4.