LLC Converter Ripple Compensation Using Secondary-Side Waveform Tracking
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Solution Overview
Problem
Conventional power supply apparatuses with LLC resonant converters face issues with double-frequency ripple generation, which can be harmful and lead to system failure, and existing compensation methods are inadequate for handling varying capacitance values, input frequencies, and load changes, especially for constant current loads.
Innovation Solution
A power supply apparatus with a voltage tracking circuit and secondary side controller that detects auxiliary voltage changes to generate a reverse waveform, allowing for optimized ripple compensation independent of input capacitance, frequency, or load changes, effectively suppressing DC link voltage ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolator such as an optical coupler is arranged to transmit input voltage to the controller on the secondary side, then the controller can reconstruct the waveform and adjust the reference voltage to offset the ripple, but the method is not comprehensive and only allows adjustment to a certain extent due to changes in capacitance values and operating temperature conditions
Solution Approach 1:
The patent implements a feedback mechanism where the controller on the secondary side continuously monitors the output voltage ripple and adjusts the reference voltage accordingly. The controller detects the ripple characteristics and dynamically modifies the compensation amount, creating a closed-loop control system that adapts to changing conditions such as capacitance variations, temperature changes, and load variations.
Solution Approach 2:
The patent employs dynamic adjustment of the reference voltage based on real-time detection of ripple characteristics. Instead of using fixed compensation values, the system continuously adapts the compensation amount according to the actual ripple magnitude and frequency, which varies with operating conditions such as input voltage changes, load variations, and temperature fluctuations.
2Reliability
If the controller detects the ripples of the output voltage and creates a reverse waveform to control the ripples, then the ripples can be controlled to a certain extent, but the method is unable to deal with the source and requires combination with current feedback mechanism, and is only suitable for constant resistance loads but unable to handle constant current loads
Solution Approach 1:
The patent introduces an intermediary mechanism in the form of a coupled inductor or transformer that links the primary and secondary sides. This intermediary allows the secondary side controller to influence the primary side operations indirectly, enabling source-level ripple compensation without requiring direct detection or complex current feedback mechanisms. The coupled element transfers the compensation effect from secondary to primary side.
Solution Approach 2:
The patent designs a universal ripple compensation method that can handle both constant resistance loads and constant current loads, as well as different types of ripple sources. The controller adapts its operation based on the load type and ripple characteristics, making the system versatile across different application scenarios without requiring separate compensation mechanisms for each case.
3Device complexity
If a power supply apparatus uses an uncontrolled rectifier bridge to connect with the power grid, then the circuit is simple, but double-frequency ripple is generated at about 100Hz which is harmful to the safe and stable operations of the power supply apparatus
Solution Approach 1:
The patent converts the harmful double-frequency ripple into a useful control signal. Instead of simply filtering out the ripple, the system detects the 100Hz ripple waveform and uses it as a reference to generate a compensating reverse waveform. The harmful ripple becomes the basis for the compensation mechanism, allowing the system to actively counteract it while maintaining the simplicity of the uncontrolled rectifier bridge.
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 solution enables comprehensive ripple compensation, ensuring stable operation across different conditions and load types, including constant current loads, by directly customizing compensation methods based on ripple source magnitude, thereby enhancing the reliability and efficiency of the power supply apparatus.
Implementation Method 1
The voltage tracking circuit is electrically connected to the auxiliary conversion circuit. The voltage tracking circuit detects the auxiliary voltage and issues a detection signal to the secondary side controller according to a result of detecting the auxiliary voltage
Implementation Method 2
According to the detection signal, the secondary side controller tracks a ripple change of the DC link voltage and instantly generates a reverse waveform opposite to a waveform of the DC link voltage
Implementation Method 3
The LLC resonant converter receives the transition DC voltage. In addition, the received transition DC voltage is converted into output DC voltages with different voltage levels in a resonant manner by the LLC resonant converter
Data Source
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AI summary
A power supply apparatus (1) includes a power factor correction circuit (2), an LLC converter (3), an auxiliary conversion circuit (4), a secondary side controller (5) and a voltage tracking circuit (6). The power factor correction circuit (2) is used for converting a DC link voltage into a first voltage. The LLC converter (3) includes a primary side circuit (30) and a secondary side circuit (31), which are coupled with each other. The primary side circuit (30) receives the first voltage. The first voltage is converted into an auxiliary voltage by the auxiliary conversion circuit (4). The voltage tracking circuit (6) detects the auxiliary voltage and issues a detection signal to the secondary side controller (5). The secondary side controller (5) tracks a ripple change of the DC link voltage and instantly generates a reverse waveform opposite to a waveform of the DC link voltage. The secondary side controller (5) controls the operations of the LLC converter (3) according to the reverse waveform.