Buck-Boost Power Converter Control for Diode Reverse Recovery
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Solution Overview
Problem
Existing buck-boost topology power conversion systems experience significant reverse recovery losses in diodes, especially when dealing with large loads, leading to inductor and switch element damage, and a high requirement for circuit components to withstand voltage spikes during lightning strikes.
Innovation Solution
Incorporating a unidirectional conduction circuit that is controlled by a controller to form a closed loop with the inductive element before the switch element is turned on, reducing reverse recovery losses by completing diode recovery before switch activation and improving voltage withstand capability by configuring the circuit as a low or high impedance as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a buck-boost topology is used to reduce cost and design complexity, then device complexity is reduced, but reverse recovery loss increases significantly
Solution Approach 1:
The patent applies preliminary action by forcing the diode to conduct in advance before the main switch turns on. A control circuit generates a preliminary control signal that activates the diode during a predetermined time interval before the switch's turn-on moment, allowing the diode to complete reverse recovery before the switch closes, thereby eliminating reverse recovery loss while maintaining the simple buck-boost topology
2Loss of energy
If the diode is replaced with a field effect transistor for synchronous rectification, then reverse recovery loss is reduced, but device complexity and turn-off loss increase
Solution Approach 1:
The patent uses a conventional diode with finite reverse recovery characteristics instead of replacing it with a more complex field effect transistor. By managing the diode's natural reverse recovery behavior through preliminary conduction control, the solution avoids the increased device complexity and turn-off losses associated with synchronous rectification transistors
3Reliability
If the circuit components are designed to withstand high voltage spikes during lightning strikes, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by controlling the diode to conduct in advance before voltage spikes occur. This preliminary conduction prepares the circuit in a safer state, reducing the magnitude of voltage spikes that reach other components during lightning strikes, thereby improving reliability without requiring all components to be rated for extreme voltage conditions
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 solution effectively reduces reverse recovery losses and enhances the voltage withstand capability of the power conversion circuit, preventing damage from voltage spikes and improving efficiency, particularly in buck-boost topology circuits.
Implementation Method 1
When Q1 is turned on, an input voltage Vin of a power supply enables an inductor L to store energy. When Q1 is turned off, the inductor L releases energy through a diode D1
Implementation Method 2
the inductor L releases energy through a diode D1
Implementation Method 3
complete reverse recovery of the first diode before the first switch element is turned on
Data Source
AI summary
Embodiments of the present disclosure disclose a power converter and a related system. The power converter includes a controller and a power conversion circuit. The power conversion circuit is configured to convert an input power of an input power supply into an output power of a load, where the input power supply is an external power supply connected to the power converter. The controller is configured to control on/off of the first switch element, to implement connection/disconnection between the input power supply and the inductive element; and control the unidirectional conduction circuit to be turned on before the first switch element is turned on in the power conversion cycle.