Half-Bridge High-Side Drive Using Composite Current Mirrors
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Solution Overview
Problem
High voltage half bridge circuits face issues with common mode voltage transients, which can lead to erroneous control and potential transistor destruction due to high current spikes, and existing protection circuits slow down the switching rate.
Innovation Solution
A high side control circuit using composite current mirror circuits and comparators to manage the bootstrap voltage node, reducing the impact of common mode voltage transients without limiting the switching speed, by ensuring sufficient differential currents for accurate voltage signal resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional protection circuit is used to protect against common mode voltage transients, then the reliability of the half bridge circuit is improved, but the switching speed is reduced
Solution Approach 1:
The patent extracts and eliminates the conventional protection circuit that was causing switching delays. Instead of using traditional protection mechanisms that slow down switching, the invention uses a bootstrap capacitor coupled to the output node and composite current mirror circuits that inherently reject common mode transients without introducing delay, thus removing the harmful protection circuit element while maintaining reliability
Solution Approach 2:
The patent introduces a bootstrap capacitor as an intermediary element coupled between the output node and the control circuit. This capacitor serves as a mediator that provides stable reference voltages to the composite current mirror circuits, enabling them to distinguish between common mode transients and actual control signals, thereby maintaining fast switching while protecting against transient errors
2Reliability
If the control circuit is made more complex to handle common mode transients, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The patent makes the control circuit elements serve multiple functions. The composite current mirror circuits not only perform their traditional current mirroring function but also inherently reject common mode transients through their differential configuration. The bootstrap capacitor simultaneously provides voltage reference and transient filtering. This multi-functionality achieves reliable transient protection without adding separate protection circuitry
Solution Approach 2:
The patent changes the operational parameters of the control circuit by using differential voltage comparisons in the composite current mirror circuits. Instead of comparing voltages to fixed ground references, the circuits compare differential voltages that are immune to common mode shifts. This parameter change enables the same control circuit to handle both normal operation and transient conditions without increasing 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 solution effectively reduces or eliminates the effect of common mode voltage transients, ensuring proper control of the half bridge circuit while maintaining high switching speed.
Implementation Method 1
a bootstrap capacitor coupled between a bootstrap voltage node and an output node of the N-type transistor
Implementation Method 2
a first composite current mirror circuit having an input coupled to the bootstrap voltage node and a second composite current mirror circuit having an input coupled to the bootstrap voltage node
Data Source
AI summary
A level shift circuit is configured to control a high side transistor of a half bridge circuit. The level shift circuit has composite current mirrors and other circuits that reduce the effect of transient voltages that are produced as the half bridge circuit is switched.