Power Converter Low-Load Efficiency Body Diode Rectification
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Solution Overview
Problem
Conventional DC-DC converters experience significant power loss and low efficiency at low loads due to no-load conduction loss, which existing solutions like synchronous rectification at the secondary side cannot fully address.
Innovation Solution
A power converter design that includes a transformer with a primary and secondary side, featuring a first MOSFET, PWM controller, current detection control unit, comparator, and second MOSFET with a body diode, allowing for efficient synchronous rectification at low loads by utilizing the body diode to minimize conduction loss through intelligent control by the comparator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous rectification using a second MOSFET is employed at the secondary side, then conversion efficiency during high load is enhanced, but no-load conduction loss increases resulting in low efficiency at no-load
Solution Approach 1:
The patent implements dynamic switching between two operational modes: synchronous rectification mode (using second MOSFET) for high load conditions, and body diode rectification mode for no-load/low load conditions. The control unit dynamically selects the appropriate mode based on load detection, thereby optimizing efficiency across the entire operating range and eliminating the trade-off between high-load and no-load efficiency.
Solution Approach 2:
The patent changes the operational parameter of the secondary side rectification by switching between two distinct states: active MOSFET conduction for high current applications and passive body diode conduction for low current applications. This parameter change allows the system to adapt to varying load conditions and minimize conduction losses in both scenarios.
2Loss of energy
If current detection is performed at the primary side of the transformer, then no-load conduction loss is reduced, but the solution cannot fully eliminate standby loss without involving the primary side
Solution Approach 1:
The patent introduces a body diode as an intermediary element in the secondary side circuitry. This body diode provides a passive rectification path that automatically conducts during no-load conditions without requiring active control or detection circuitry on the primary side, thereby reducing no-load losses while simplifying the overall control architecture.
Solution Approach 2:
The body diode of the second MOSFET performs self-service rectification during no-load conditions without requiring external control signals or primary side intervention. The diode automatically conducts reverse recovery current and provides freewheeling path, enabling the system to manage no-load conditions autonomously on the secondary side.
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 design effectively reduces low-load conduction loss and improves efficiency by using the body diode for current rectification at the secondary side, optimizing power converter performance across varying load conditions.
Implementation Method 1
The second MOSFET is electrically connected to one end of the second winding and having built therein a body diode. The second MOSFET is electrically connected with the opposite end thereof to the current detection control unit.
Data Source
AI summary
A power converter includes a DC power source, a transformer having a first winding, a first MOSFET and a PWM controller at the primary side and a second winding, a drive control unit, a current detection control unit, a comparator and a second MOSFET at the secondary side. The comparator has its input end electrically connected to the current detection control unit and its output end electrically connected to the drive control unit, which is electrically connected to the second MOSFET for synchronous rectification. The second MOSFET is electrically connected to one end of the second winding, having a body diode built therein. The second winding and the second MOSFET constitute a combination circuit electrically connected to a load that has a capacitor electrically connected thereto in a parallel manner. By means of the aforesaid arrangement, conduction loss at a low load is minimized, thereby improving the efficiency at a low load.