Resonant Converter Current Detection via Sensing Transformer
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Solution Overview
Problem
Existing resonance converter systems for lighting devices, such as those using LLC resonant converters, face inaccuracies in detecting the current delivered to lamps due to indirect measurement methods, which can lead to inefficiencies and inaccuracies in controlling the operating device.
Innovation Solution
An operating device with a resonance converter, a measuring circuit featuring a transformer and a bridge rectifier with controllable switches, and a control device that precisely detects the current delivered to the lamp by rectifying the secondary winding current, allowing for exact determination and control of the current, while maintaining galvanic isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an auxiliary winding of the transformer is used to indirectly measure the current delivered to the lamp, then galvanic isolation between the mains voltage side and the lamp is maintained, but the current detection accuracy deteriorates
Solution Approach 1:
The patent introduces a dedicated current sensing transformer as an intermediary device specifically for accurate current measurement. This separate sensing transformer with primary winding in series with the lamp and secondary winding connected to the rectifier circuit provides precise current detection without compromising the galvanic isolation provided by the main power transformer. The intermediary sensing transformer allows direct measurement of lamp current while the main transformer maintains isolation.
2Device complexity
If the bridge rectifier is controlled based on control signals of the half-bridge circuit switches, then the rectification process is simplified, but current components are cut off due to dead time between control signals, deteriorating measurement precision
Solution Approach 1:
The patent employs feedback control where the bridge rectifier switches are controlled based on the actual detected voltage polarity at the half-bridge output node. The control circuit continuously monitors the voltage at this node and uses this feedback information to determine when to switch the rectifier diodes, ensuring they conduct during the entire duration when current is actually flowing. This feedback mechanism eliminates the dead time problem inherent in open-loop control based on switch control signals.
Solution Approach 2:
The rectifier control is made dynamic by continuously adapting the rectifier switch timing based on the real-time voltage state at the half-bridge output. Instead of using fixed timing based on switch control signals, the system dynamically adjusts the rectifier operation to match the actual current flow conditions, ensuring complete rectification of all current components regardless of switching transitions.
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 solution enables precise detection and control of the current delivered to lamps, improving energy efficiency and accuracy by eliminating dead time-related errors in current measurement and rectification.
Implementation Method 1
At least one primary winding of the transformer detects the current delivered by the secondary winding of the transformer
Implementation Method 2
Resonant converters with a series or parallel resonant circuit are often used in control gear to enable energy-efficient operation with low switching losses
Implementation Method 3
the bridge rectifier rectifies the current delivered by the secondary winding of the transformer
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
According to the present invention, an operating device (1) for operating light sources (4) comprises a resonant converter (6) for providing a voltage and a current for operating the light source (4), a measuring circuit (7) for detecting the current supplied by the resonant converter (6) to the light source (4), and a control device (8) for controlling the resonant converter (6) based on the detected current. The resonant converter (6) consists of at least a half-bridge circuit, a resonant circuit coupled to the half-bridge circuit, and a transformer coupled to the resonant circuit.The measuring circuit (7) comprises a transformer and a rectifier with at least one controllable switch, wherein at least one primary winding of the transformer detects the current supplied by the secondary winding of the transformer, the rectifier rectifies the current supplied by the secondary winding of the transformer, and the controllable switch is controlled on the basis of a signal detected between the two switches of the half-bridge circuit.