H-Bridge Driver Reverse Current Protection via Island Merging
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Solution Overview
Problem
In semiconductor devices used for controlling the forward or reverse rotation of electrical equipment, such as motors, there is a risk of large reverse currents flowing through parasitic diodes in H-bridge circuits when the power source is reversed, leading to potential damage.
Innovation Solution
A semiconductor device with a control section and an H-bridge circuit that includes a reverse-connection-time backflow prevention circuit formed over the same island as the control section, using a vertical MOSFET with a low on-resistance to prevent reverse current flow by coupling the parasitic diode's anode to the high potential and cathode to the earth electrode, thereby inhibiting current supply when the battery is reversed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power source is coupled reversely to an H-bridge circuit, then large reverse current flows through parasitic diodes of MOS transistors, but this causes potential damage to the semiconductor device
Solution Approach 1:
The patent applies preliminary anti-action by incorporating a backflow prevention circuit that proactively blocks reverse current before it can damage the H-bridge circuit. The circuit is designed to detect and prevent reverse connection conditions in advance, counteracting the harmful effect before it occurs. This is achieved through a dedicated prevention circuit that monitors and controls current flow direction.
Solution Approach 2:
The backflow prevention circuit acts as an intermediary between the power source and the H-bridge circuit. It mediates the current flow by introducing a control element (such as a MOS transistor with controlled gate potential) that can selectively block or allow current in either direction. This intermediary component protects the H-bridge from reverse current while still permitting normal forward operation.
2Reliability
If a backflow prevention circuit is formed over a separate dedicated island, then reverse current protection is achieved, but device complexity and manufacturing process difficulty increase
Solution Approach 1:
The patent merges the backflow prevention circuit with the control section by forming both over the same third island. This consolidation integrates the protection function into the existing control infrastructure rather than requiring a separate dedicated island. The merging reduces overall device complexity while maintaining the reverse current protection capability, as the prevention circuit shares the island substrate with the control section.
Solution Approach 2:
The third island serves multiple functions by hosting both the control section and the backflow prevention circuit. This multi-functional design eliminates the need for a dedicated single-function island, optimizing the use of semiconductor substrate real estate. The universal island structure reduces manufacturing complexity while providing both control and protection functions.
3Power
If thick wire bonding is used to connect islands, then current carrying capacity increases, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the backflow prevention circuit with the control section on the same island, which eliminates or reduces the need for thick wire bonding between separate islands. By consolidating functions onto a single island, the invention reduces inter-island interconnect requirements while maintaining adequate current carrying capacity through optimized internal routing and transistor design.
Solution Approach 2:
The invention applies local quality by optimizing the current path design within the merged island structure. Instead of relying on thick wire bonding across islands, the current flow is locally managed through optimized transistor arrangements and internal connections within the third island, reducing the need for heavy external interconnects.
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 configuration effectively protects the semiconductor device from reverse current damage by preventing reverse current flow during reverse power source connections, allowing for simple and efficient control of electric current flow in both directions without the need for additional dedicated islands or thick wire bonding.
Implementation Method 1
a reverse-connection-time backflow prevention circuit to prevent electric current flowing in a direction opposite to the direction of an input current from being supplied to the H-bridge circuit
Data Source
AI summary
A semiconductor device includes an H-Bridge driver. The H-Bridge driver includes a first island on which a first power transistor and a second power transistor are mounted; a second island on which a third power transistor and a fourth power transistor are mounted; a third island on which a control circuit and a protection power transistor are mounted, the control circuit being configured to control the first, second, third and fourth power transistors, wherein the third island is allocated between the first island and the second island.