MOSFET Transient Current Diversion Circuit for Ringing Reduction
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Solution Overview
Problem
Conventional semiconductor power devices face ringing oscillations and shooting through issues due to parasitic inductances, leading to efficiency loss and malfunction in switching circuits, with existing solutions failing to effectively address trace inductance-related problems.
Innovation Solution
A current diversion and clamping circuit with a serially connected diode and capacitor is introduced between the drain and source of a low side MOSFET to divert transient currents, reducing ringing oscillations, and this circuit can be integrated into the MOSFET package or implemented externally with components closely mounted to minimize parasitic inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead time control is implemented between high side and low side MOSFET gate signals, then shoot through current is prevented, but ringing oscillations cannot be effectively suppressed
Solution Approach 1:
A resistor is introduced as an intermediary element connected between the drain of the low side MOSFET and the cathode of the freewheeling diode. This resistor acts as a damping element that dissipates the energy causing ringing oscillations without interfering with the dead time control mechanism that prevents shoot through current.
Solution Approach 2:
The circuit parameters are modified by adding a resistor with specific resistance value (typically in the range of 0.1 to 10 ohms) to change the damping characteristics of the circuit. This parameter change transforms the underdamped oscillatory behavior into a critically damped or overdamped behavior, eliminating ringing while maintaining the shoot through prevention function.
2Object-generated harmful factors
If package inductances are minimized, then ringing and shoot through problems are reduced, but trace inductances from poor layout practices cannot be addressed
Solution Approach 1:
The resistor serves as a local intermediary damping element placed within the MOSFET package or immediately adjacent to it. This local solution addresses the ringing problem caused by trace inductances without imposing complex layout requirements on the entire circuit board, as the damping action occurs locally at the source of the oscillation.
Solution Approach 2:
The solution segments the problem by addressing the ringing oscillation issue locally at the MOSFET level rather than requiring global circuit board layout optimization. The resistor is placed specifically at the low side MOSFET drain terminal, creating a localized damping solution that is independent of overall trace routing practices.
3Object-generated harmful factors
If negative bias is applied to low side FET gate drive, then ringing oscillations are reduced, but switching and conduction losses increase and gate drive circuitry becomes more complex
Solution Approach 1:
The resistor acts as a passive intermediary damping element that reduces ringing oscillations without requiring active gate drive modifications. Unlike negative bias that requires complex gate drive circuitry, the resistor provides automatic damping through its dissipative nature, maintaining simplicity in the gate drive system while still eliminating ringing.
Solution Approach 2:
The resistor is a simple, inexpensive, passive component that dissipates the energy causing ringing oscillations. This disposable energy dissipation approach is more cost-effective and simpler than implementing complex active gate drive circuits with negative bias, achieving the same goal with a basic resistive element.
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 significantly reduces the amplitude and duration of ringing oscillations, preventing unintentional switching and improving circuit efficiency by diverting transient energy back to the input power supply, compatible with standard gate driver circuits and reducing production costs.
Implementation Method 1
a transient reverse current diversion circuit connected to the drain of a semiconductor power device for diverting a reverse transient current therethrough whereby the reverse transient current is diverted from passing through a body diode of the semiconductor power device thus reducing a transient ringing oscillation
Implementation Method 2
the reverse transient current diversion circuit includes a capacitor storing electric charges therein for clamping the transient ringing oscillation
Implementation Method 3
the reverse transient current diversion circuit includes a capacitor storing electric charges therein for clamping the transient ringing oscillation
Implementation Method 4
the reverse transient current diversion circuit includes a diode for passing the reverse transient current from the drain
Data Source
AI summary
A switching device includes a high-side MOSFET chip having a first high-side source connected to a low-side drain of a low-side MOSFET chip. The switching device further includes a transient reverse current diversion circuit connected to a drain of the low side MOSFET chip for diverting a reverse transient current therethrough whereby a reverse transient current in turning off the low side MOSFET chip is diverted from passing through a body diode of the low side MOSFET chip reducing a transient ringing oscillation. The reverse transient current diversion circuit includes a diode for conducting the reverse transient current from the drain. The reverse transient current diversion circuit further includes a capacitor connected between the diode and a source of the low side MOSFET chip.