High-Side Drive Circuit with Level Shifting for Stable Gate Voltage
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Solution Overview
Problem
Conventional drive circuits with internal floating power supplies face instability in driving voltage for high-side transistors due to parasitic capacitance, leading to destabilization of the gate driving voltage and unstable high-side output signals.
Innovation Solution
The drive circuit incorporates a first and second level shift circuit, a pre-driver, and a high-side transistor, utilizing a timing adjustment circuit and internal power supply circuit to generate and stabilize the gate signal, ensuring the high-side transistor operates stably with a lower power supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transistor size is increased to improve power feed performance of the source follower circuit, then the power feed performance is improved, but the drain-to-source current changes due to parasitic capacitance causing destabilization of gate driving voltage
Solution Approach 1:
The drive circuit is divided into multiple functional blocks: source follower circuit for power feeding, level shift circuit for voltage level adjustment, and pre-driver circuit for gate signal generation. Each block operates independently with defined interfaces, allowing the transistor size in the source follower to be increased for power performance without affecting the stability of the gate driving voltage generated by the pre-driver circuit.
Solution Approach 2:
The level shift circuit acts as an intermediary between the source follower circuit and the pre-driver circuit. It receives the driving voltage from the source follower, adjusts its level, and provides it to the pre-driver, thereby isolating the parasitic capacitance effects in the source follower from the gate driving voltage generation process.
2Object-affected harmful factors
If a conventional source follower circuit is used to curb noise influence, then noise influence is reduced, but the high-side transistor cannot stably output high-side output signal due to gate voltage destabilization
Solution Approach 1:
The circuit is segmented into noise-filtering source follower block and signal-generation pre-driver block. The source follower specifically handles power feeding with noise curbing, while the pre-driver handles gate signal generation with stability assurance, eliminating the conflict between noise reduction and signal stability.
Solution Approach 2:
The level shift circuit performs preliminary voltage level adjustment on the driving voltage before it reaches the pre-driver circuit. This preliminary action ensures that the pre-driver receives a stable, properly-leveled voltage, enabling it to generate stable gate driving signals regardless of variations in the source follower output.
3Ease of operation
If the driving voltage for gate is destabilized, then the gate can respond to source follower output, but the high-side transistor cannot stably output high-side output signal for driving load device
Solution Approach 1:
The drive circuit separates the gate response function (handled by level shift circuit) from the high-side output stability function (handled by pre-driver circuit). This segmentation allows the gate to respond flexibly to voltage changes while the pre-driver ensures stable gate signal generation for reliable high-side output.
Data Source
AI summary
A drive circuit includes a first level shift circuit, a second level shift circuit, a pre-driver, and a high-side transistor. The first level shift circuit outputs a first switch signal. The second level shift circuit outputs a second switch signal. The pre-driver includes a first switch portion configured to perform switching in accordance with the first switch signal and a second switch portion configured to output a gate signal in accordance with the second switch signal. The high-side transistor outputs a high-side output signal to an output terminal with a second power supply voltage which is fed in accordance with the gate signal.