LLC Converter Rectifier Turn-Off via Primary Current Sensing
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Solution Overview
Problem
Existing methods for controlling the turn-off operation of rectifying switching elements in LLC voltage converters result in switching losses due to premature turn-off before the secondary current reaches zero, and introduce power losses from current measurement.
Innovation Solution
A LLC voltage converter system that includes a transformer, a controller, and a current sensor to measure the primary current and determine when the secondary current is substantially zero, allowing for precise control of the rectifying switching elements to achieve zero current switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If existing methods are used to control the turn-off operation of rectifying switching elements, then the switching elements can be turned off, but switching losses occur due to premature turn-off before secondary current reaches zero
Solution Approach 1:
The patent uses the primary current as an intermediary parameter to indirectly determine the secondary current status. By measuring the primary current through the transformer's input winding and comparing it against a predetermined threshold, the system can accurately determine when the secondary current reaches zero without directly measuring the secondary current, thus avoiding premature turn-off and reducing switching losses
Solution Approach 2:
The controller continuously monitors the primary current and uses this feedback to dynamically control the turn-off timing of the rectifying switching elements. When the primary current falls below the threshold, the controller triggers the turn-off operation, ensuring synchronization with the actual zero-current moment and preventing energy losses
2Measurement precision
If direct current measurement is used to determine zero secondary current, then accurate timing can be achieved, but power losses from current measurement increase
Solution Approach 1:
The patent measures the primary current through the transformer's input winding as an intermediary to infer the secondary current status. This indirect measurement approach maintains high timing accuracy for zero current detection while significantly reducing the power losses associated with direct secondary current measurement, as the primary current measurement requires less power
Solution Approach 2:
The patent replaces direct electrical measurement of secondary current with an indirect measurement system that uses primary current sensing. This substitution reduces the measurement burden and associated power losses while maintaining the necessary measurement precision for accurate zero-current detection
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 proposed solution reduces switching losses and power losses associated with current measurement, improving the efficiency of the LLC voltage converter by ensuring accurate determination of zero secondary current.
Implementation Method 1
The resonant capacitance Cr and the resonant inductance Lr resonate at approximately the switching frequency of the alternating voltage so as to apply a voltage across the magnetising inductance Lm of the input winding of the transformer 1300
Implementation Method 2
The magnetising inductance Lm of the input winding of the transformer 1300 is magnetically coupled to an output winding 1301 of the transformer 1300. Therefore, a voltage across the magnetising inductance Lm of the input winding of the transformer 1300 induces a voltage across the output winding 1301 of the transformer 1300
Data Source
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AI summary
A LLC voltage converter (2000) for converting a DC input voltage to a DC output voltage. The LLC voltage converter (2000) includes: a transformer (2300) having an input winding and an output winding (2301), a controller (2500) and a current sensor (2204). The current sensor (2204) measures a primary current through the input winding of the transformer (2300) and provides a measurement of the primary current to the controller (2500). The controller (2500) determines when a secondary current, through the output winding (2301) of the transformer (2300), is substantially zero based on the measurement of the primary current and a maximum value of the primary current.