Inductive Load Driver Clamping for Fast Current Decay Under PWM
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Solution Overview
Problem
Existing inductive load drivers face challenges in managing energy decay during transition phases, particularly in high-demand applications, without exceeding the absolute maximum rating (AMR) of gate driver components, which can lead to potential damage and reduced system reliability.
Innovation Solution
A load driver with a semi-active recirculation driver and active or passive clamping circuits that manage energy decay through pulse width modulation (PWM) modes, enabling fast decay by creating low or high impedance recirculation paths, and active or passive clamping configurations to safely dissipate energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a standard diode is used for energy decay, then the circuit is simple, but the energy decay is not sufficiently rapid
Solution Approach 1:
The patent implements dynamic switching between different recirculation path configurations (low impedance during PWM off-times, high impedance during fast decay mode) to adapt the energy decay rate to operational requirements. This allows the system to achieve rapid energy decay when needed while maintaining circuit simplicity through controlled impedance transformation rather than complex additional components.
Solution Approach 2:
The patent changes the impedance parameter of the recirculation path dynamically - using low impedance during PWM off-times for controlled decay and high impedance during fast decay mode for rapid energy dissipation. This parameter transformation allows the same circuit topology to provide different decay rates without adding significant complexity.
2Speed
If clamping voltage is increased to -24V or lower for rapid energy dissipation, then energy decay is faster, but gate driver pin absolute maximum rating is exceeded
Solution Approach 1:
The patent introduces a recirculation path with controllable impedance as an intermediary between the inductive load and ground. This intermediary structure allows energy to be dissipated through controlled paths that limit voltage spikes, preventing gate driver pin voltage from exceeding absolute maximum ratings while still achieving effective energy decay. The semi-active recirculation driver acts as a mediator that controls current flow to protect sensitive components.
Solution Approach 2:
The patent implements protective recirculation paths that are activated beforehand to cushion against potential voltage spikes. By providing predetermined energy dissipation paths with controlled impedance, the system prevents excessive voltage from reaching the gate driver pins, cushioning them against damage before it can occur.
3Speed
If fast decay mode is implemented with active clamping, then energy dissipation is rapid, but circuit complexity increases
Solution Approach 1:
The patent designs the semi-active recirculation driver to perform multiple functions: it provides low impedance recirculation during PWM off-times, switches to high impedance during fast decay mode, and works with both active and passive clamping configurations. This multi-functionality allows rapid energy dissipation without requiring separate dedicated circuits for each function, reducing overall system complexity.
Solution Approach 2:
The patent merges the recirculation driver functionality with the clamping circuit functionality into a unified structure. The semi-active recirculation driver is integrated to work with both active and passive clamping configurations, combining energy dissipation and component protection functions in a single coordinated system rather than requiring separate independent circuits.
Data Source
AI summary
A load driver includes an active clamping circuit coupled between gate and source terminals of a power stage. The active clamping circuit serves to either pass through a gate drive voltage (provided by a gate driver) to the power stage in a PWM mode or to actively clamp the voltage between gate and source terminals of the power stage to enable fast decay recirculation in fast decay mode (when the load driver is configured for active clamping). A semi-active recirculation driver is coupled between ground and the output of the power stage. The semi-active recirculation driver serves to either provide a low impedance recirculation path in the PWM mode or to passively clamp the output voltage to provide for a fast decay recirculation path in fast decay mode (when the load driver is configured for passive clamping).