Integrated High Side Gate Driver Structure for Class D Amplifiers
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Solution Overview
Problem
Integrated class D audio amplifiers face challenges in providing a stable high side positive supply voltage to the gate driver of high side LDMOS transistors without external capacitors, which increases component and assembly costs, especially in high-volume consumer applications.
Innovation Solution
A novel high side gate driver structure with a double junction isolated well structure and a floating voltage regulator, which relocates parasitic well capacitance from the high side positive supply voltage port to the high side negative supply voltage port, eliminating the need for external bootstrap capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external bootstrap capacitors are used to stabilize the high side positive supply voltage, then the gate-source voltage accuracy and stability is improved, but the component cost and assembly cost increase
Solution Approach 1:
The patent extracts and eliminates the external bootstrap capacitor from the system by relocating the parasitic well capacitance to serve the stabilization function. The double junction isolated well structure removes the need for external components by utilizing the inherent parasitic capacitance of the semiconductor structure itself, thereby reducing component count and assembly complexity while maintaining voltage stability.
Solution Approach 2:
The patent implements self-service by having the parasitic well capacitance automatically perform the voltage stabilization function that previously required external capacitors. The double junction isolated well structure generates its own stabilizing effect through its inherent parasitic capacitance, eliminating the need for separate external stabilization components.
2Measurement precision
If external bootstrap capacitors are used for each high side gate driver, then the gate drive voltage accuracy is improved, but the assembly cost and production complexity increase
Solution Approach 1:
The patent merges the voltage stabilization function with the gate driver structure itself by integrating the double junction isolated well design. This consolidation eliminates the need for separate external capacitors for each gate driver, reducing assembly steps and manufacturing complexity while maintaining precise gate drive voltage control through the inherent parasitic capacitance of the integrated structure.
3Ease of operation
If traditional well structure is used, then the gate driver can be implemented, but parasitic well capacitance degrades the high side positive supply voltage stability
Solution Approach 1:
The patent converts the harmful parasitic well capacitance into a beneficial element by relocating it to the high side negative supply voltage port. The double junction isolated well structure transforms what was previously a destabilizing factor into a useful capacitance that helps stabilize the high side positive supply voltage, eliminating the need for external bootstrap capacitors.
Solution Approach 2:
The patent applies inversion by connecting the parasitic well capacitance to the high side negative supply voltage port instead of the high side positive supply voltage port. This reverse connection approach changes the harmful effect into a beneficial one, where the parasitic capacitance now contributes to voltage stability rather than degradation.
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 solution allows for accurate and stable driving of high side LDMOS transistors without external capacitors, reducing costs and size while maintaining the integrity of the gate driver, thus enhancing the efficiency and cost-effectiveness of class D amplifier output stages.
Implementation Method 1
The present high side gate driver structure eliminates parasitic well structure to semiconductor substrate capacitance at the high side positive DC supply voltage of the high side gate driver which allows elimination of the above- discussed traditional external bootstrap capacitor.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
The present invention relates to an integrated high side gate driver structure for driving a power transistor. The high side gate driver structure (411) comprises a semiconductor substrate comprising a first polarity semiconductor material in which a first well diffusion (426, 430) comprising a second polarity semiconductor material is formed. A peripheral outer wall (430) of the first well diffusion is abutted to the semiconductor substrate. A second well diffusion (427, 429), comprising first polarity semiconductor material, is arranged inside the first well diffusion such that an outer peripheral wall (429) of the second well diffusion is abutted to an inner peripheral wall (430) of the first well diffusion. The integrated high side gate driver structure further comprises a gate driver comprising a high side positive supply voltage port, a high side negative supply voltage port, a driver input and a driver output, wherein the gate driver comprises a transistor driver arranged in the second well diffusion (429) such that a control terminal of the transistor driver and an output terminal of the transistor driver is coupled to the driver input and the driver output, respectively; the integrated high side gate driver structure also comprises a first electrical connection between the first well diffusion and the high side negative supply voltage port and a second electrical connection between the second well diffusion and the high side negative supply voltage port.