Diode Bypass Control Circuit for MOSFET Off-Cycle Heat Reduction
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Solution Overview
Problem
Large currents flowing through body diodes or flyback diodes in power devices lead to heat generation and can cause circuit logic confusion, preventing proper operation.
Innovation Solution
A control circuit with a main module, diode-current sensing module, and driving module forms a negative feedback loop to reduce the current through the main diode to a preset value by turning on the main switching transistor during its off cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large currents flow through body diodes or flyback diodes during the off cycle of main switching transistors, then the diodes can conduct the current, but heat generation occurs and circuit logic may be confused
Solution Approach 1:
The patent employs a feedback mechanism where the voltage across the main diode is sensed and fed back to control the gate voltage of the main switching transistor. The error amplifier compares the sensed voltage with a reference voltage and adjusts the gate voltage accordingly, creating a closed-loop control system that automatically regulates the current distribution between the diode and transistor, thereby reducing heat generation while maintaining reliable circuit operation.
Solution Approach 2:
The patent changes the operating parameters of the main switching transistor by dynamically adjusting its gate voltage based on the current flowing through the parallel diode. By modifying the gate voltage parameter in response to diode current conditions, the transistor's conductivity is adjusted to分流 the current and reduce the thermal load on the diode, effectively managing heat generation during off cycles.
2Reliability
If large currents flow through body diodes or flyback diodes, then the diodes can protect the MOSFETs, but the circuit control is lost due to excessive currents through the substrate
Solution Approach 1:
The feedback control mechanism senses the voltage across the main diode and uses it to regulate the gate voltage of the main switching transistor. This closed-loop control prevents excessive current from flowing through the diode and substrate, thereby maintaining circuit control and logic integrity while still providing MOSFET protection through coordinated operation of the transistor and diode.
Solution Approach 2:
The main switching transistor acts as an intermediary element that shares the current burden with the main diode. By introducing the transistor as a parallel path with controllable conductivity, the system can divert excess current away from the diode and substrate, preventing current-induced control issues while maintaining protective functionality.
Data Source
AI summary
A control circuit for bypassing a diode current and a control method are provided; the control circuit includes a main module, a diode-current sensing module, a driving module; the diode-current sensing module is for sensing a current flowing through a main diode to generate a sensing current; the driving module is for generating a driving current proportional to the sensing current to drive a main switching transistor to be turned on; the main module, the diode-current sensing module, the driving module form a negative feedback loop to reduce the current flowing through the main diode to a preset value. The present disclosure solves problems in the related art, such as heat generation caused by large currents flowing through a body diode or flyback diode when the main switching transistor is in an off cycle, and the control circuit being out of control due to large currents introduced into a substrate.