LLC Resonant Power Supply Load Estimation Without Current Sensors
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Solution Overview
Problem
Existing switching power supply apparatuses, such as DC-DC converters, face challenges in downsizing due to the need for accurate load current detection, which often involves components that increase size and efficiency loss, particularly in LLC resonant converters.
Innovation Solution
A switching power supply apparatus that estimates load current using a load current estimator based on the phase difference or time product of resonant inductor and transformer excitation currents, eliminating the need for current sensors and isolated transmission devices, thereby reducing component count and power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sensors and isolated transmission devices are used for accurate load current detection, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The patent extracts the current detection function from the secondary side to the primary side by using the resonant inductor current as a reference. This eliminates the need for current sensors and isolated transmission devices on the secondary side, reducing device complexity while maintaining measurement precision through mathematical calculation of the load current based on primary side measurements.
Solution Approach 2:
The patent introduces a mathematical model as an intermediary between primary side measurements and secondary side load current determination. By using the phase difference or time product relationship between resonant inductor current and transformer excitation current, the system calculates load current without direct measurement, thus avoiding complex sensing hardware.
2Measurement precision
If current sensors and isolated transmission devices are added for accurate load current detection, then measurement precision is improved, but the apparatus size increases
Solution Approach 1:
The patent removes bulky current sensors and isolated transmission devices from the apparatus by transferring the detection function to the primary side. The load current is determined through mathematical calculation using primary side current measurements, eliminating the need for additional volume-consuming components on the secondary side.
3Measurement precision
If current sensors and isolated transmission devices are used for load current detection, then measurement precision is improved, but energy loss increases
Solution Approach 1:
The patent extracts the power loss issue by eliminating current sensors and isolated transmission devices from the secondary side. Since these components are removed, their associated copper losses, core losses, and insulation losses are eliminated, reducing overall energy loss while maintaining accurate load current determination through primary side measurements and mathematical calculation.
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
Enables downsizing, cost reduction, and improved reliability by accurately controlling load current without additional components, allowing for higher switching frequencies and reduced component count.
Implementation Method 1
The inverter circuit includes a first switching device, a second switching device, a resonant inductor, and a resonant capacitor
Implementation Method 2
The transformer includes a primary winding and a secondary winding
Data Source
AI summary
A switching power supply apparatus includes a pair of input terminals, a pair of output terminals, a transformer, an inverter circuit, a rectifying and smoothing circuit, and a controller. The inverter circuit includes first and second switching devices, a resonant inductor, and a resonant capacitor. The controller controls a switching operation of each of the first and second switching devices. The first and second switching devices are coupled in series to each other between a pair of coupling lines. The resonant inductor, the resonant capacitor, and a primary winding are coupled in series to each other in no particular order between a node between the first and second switching devices, and one of the pair of input terminals. The controller controls the switching operation on the basis of a voltage across the resonant capacitor and a voltage across the primary winding.