Gate Drive Circuit That Bypasses Body Diode Reverse Recovery
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Solution Overview
Problem
Conventional power devices, such as superjunction MOS transistors, suffer from excessively high reverse recovery currents due to their parasitic body diodes, leading to high power consumption and potential burnout, and existing solutions like heavy metal doping and radiation technologies are costly and unreliable.
Innovation Solution
A gate drive circuit is designed to redirect freewheeling current through a conductive channel instead of the freewheeling diode, using a high-voltage LDMOS transistor and a diode in series with a voltage detection circuit and OR gate to manage the on-state voltage drop, reducing the reverse recovery current and mitigating overshoot voltage issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a parasitic body diode is used to provide current freewheeling function, then the power device is protected from reverse electromotive force breakdown, but the reverse recovery current becomes extremely high causing power consumption and potential burnout
Solution Approach 1:
The patent introduces an N-channel superjunction MOS transistor as an intermediary device between the parasitic body diode and the main circuit. This MOS transistor acts as a mediator that provides an alternative low-loss current path during freewheeling operation, reducing the reverse recovery current while maintaining the protective function against reverse electromotive force breakdown.
Solution Approach 2:
The patent changes the electrical parameters of the power device by integrating a superjunction structure that modifies the on-resistance and breakdown voltage characteristics. The superjunction MOS transistor provides a lower on-resistance path for freewheeling current, thereby reducing power losses during reverse recovery while maintaining adequate breakdown protection.
2Loss of energy
If heavy metal doping or radiation technology is used to reduce reverse recovery current, then the reverse recovery charge is reduced, but the manufacturing cost increases and reliability decreases
Solution Approach 1:
The patent employs a superjunction MOS transistor that can be manufactured using standard semiconductor fabrication processes without requiring expensive heavy metal doping or radiation treatments. This approach uses conventional, cost-effective manufacturing methods to achieve the desired reduction in reverse recovery charge while maintaining device reliability.
3Power
If the p-n junction area is increased to provide freewheeling function, then the current handling capability is improved, but the reverse recovery charge increases significantly
Solution Approach 1:
The patent changes the physical and electrical parameters by replacing the conventional large-area p-n junction with a superjunction MOS transistor structure. This structural parameter change enables the device to achieve adequate current handling capability through the MOS channel while dramatically reducing the reverse recovery charge associated with large p-n junction areas.
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 approach significantly reduces the reverse recovery current of power devices while avoiding the high costs and reliability concerns of existing methods, maintaining low power consumption and enhancing device performance.
Implementation Method 1
a voltage detection circuit, an input terminal of the voltage detection circuit being connected to the current output terminal of the switch transistor, and the voltage detection circuit outputting a detection value after detecting an on-state voltage drop of the switch transistor
Data Source
AI summary
The present invention discloses a gate drive circuit for reducing a reverse recovery current of a power device, and belongs to the field of basic electronic circuit technologies. The gate drive circuit includes a high-voltage LDMOS transistor, a diode forming a freewheeling path when the diode is turned on or a low-voltage MOS transistor in anti-parallel connection with a body diode, and a voltage detection circuit. When the power device is turned off, a freewheeling current produced by an inductive load flows through a freewheeling diode, the voltage detection circuit detects that the freewheeling diode is turned on, and an output signal is processed by a control circuit, to cause the drive circuit to output a high level, so that channels of the power device and the high-voltage LDMOS transistor are turned on, the freewheeling current flows through the conductive channels, almost not through the freewheeling diode, and there is no reverse recovery current in the freewheeling diode at this time, thereby reducing the reverse recovery current of the power device.