LLC Converter Synchronous Rectifier Control via Primary Current Sensing
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Solution Overview
Problem
Existing LLC converter circuits face challenges in reducing power losses due to impedance introduced on the secondary side for synchronous rectifier control, which also complicates current measurement and control.
Innovation Solution
A controller for an isolated LLC power converter circuit that determines the primary winding current and uses it to generate a control signal for the synchronous rectifier switch on the secondary side, eliminating the need for impedance on the secondary side and reducing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impedance is introduced into the secondary side to measure synchronous rectifier current and determine control signal, then synchronous control can be achieved, but power losses increase due to high output current and measurement errors
Solution Approach 1:
Instead of measuring current on the secondary side (where high current causes measurement errors and power losses), the invention inverts the approach by measuring the primary winding current on the primary side (where current is lower and measurement is more accurate). The control signal for the secondary side switch is then derived from this primary side measurement, eliminating the need for impedance introduction on the secondary side and thereby reducing power losses.
2Ease of operation
If impedance is introduced into the secondary side for current measurement, then control signal can be determined, but measurement errors increase leading to power losses
Solution Approach 1:
The invention uses the primary winding current as an intermediary measurement. Instead of directly measuring the difficult-to-measure secondary side current (which requires impedance introduction and causes errors), the system measures the primary winding current (which is easier to measure accurately) and uses this measurement to derive the control signal, effectively using the primary current as a mediator to solve the measurement problem.
3Measurement precision
If components with high current ratings are used to determine secondary winding current, then accurate measurement is possible, but cost increases
Solution Approach 1:
The invention inverts which current is measured - instead of measuring the high-current secondary winding (which would require expensive high-current rated components), it measures the lower-current primary winding. This inversion allows the use of less expensive, lower-current rated components while still achieving accurate control, thereby reducing manufacturing cost.
Data Source
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AI summary
The present invention provides a controller, a circuit, an aircraft electrical system and a method for controlling an isolated LLC power converter circuit, the circuit comprising an isolated transformer, and a first switch operable as a synchronous rectifier on a secondary side of the transformer. In the first aspect, the controller comprises a current determination module configured to determine a primary winding current on a primary side of the isolated transformer; and a processing module configured to use the determined primary winding current in a processing algorithm to output a first control signal to configure the first switch on the secondary side of the isolated transformer to determine a waveform of a secondary winding current of the isolated transformer.