LLC Resonant Converter with Segmented Inductance for LED Drivers
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Solution Overview
Problem
Existing LLC resonant converter circuits face challenges in efficiently supplying matched currents to multiple LED strings while minimizing size, weight, and cost, as they require impractically small tolerance in magnetizing inductances and often degrade efficiency due to multiple transformer stages.
Innovation Solution
The design incorporates a separate shunt inductor and/or series resonant inductor that are independent of the transformers, allowing for large magnetizing inductances and minimizing the effect of inductance mismatches, with primary windings coupled in series and secondary windings providing equal currents to output circuits through a single transformer stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If magnetizing inductances of transformers are made small to enable primary-side zero voltage switching, then switching efficiency is improved, but current matching between multiple output loads deteriorates due to impractically small tolerance requirements
Solution Approach 1:
The patent segments the magnetizing inductance function by introducing a separate shunt inductor (Lsh) that is independent of the transformers. This allows the transformer magnetizing inductances to be made small for efficient ZVS operation while the separate shunt inductor provides the necessary inductance for current matching, eliminating the need for impractically small tolerance requirements on transformer magnetizing inductances.
Solution Approach 2:
The patent extracts the shunt inductance function from the transformer magnetizing inductances and implements it as a separate shunt inductor (Lsh) connected to the primary side. This extraction allows the transformer magnetizing inductances to be optimized for ZVS operation without being constrained by current matching requirements, as the separate shunt inductor handles the current balancing function.
2Adaptability or versatility
If multiple transformer stages are used to provide isolated outputs, then galvanic isolation and flexibility are improved, but power processing efficiency deteriorates due to multiple transformation stages
Solution Approach 1:
The patent introduces an intermediary coupled circuit (including the separate shunt inductor Lsh and coupling capacitors) between the primary side and secondary sides of the transformers. This intermediary enables galvanic isolation and flexible output configuration without requiring multiple transformer stages, as it provides the necessary coupling and isolation functions through a single transformer stage combined with the coupled circuit elements.
Solution Approach 2:
The patent makes the single transformer stage universal by combining it with a separately-coupled shunt inductor and coupling circuits that can provide multiple isolated outputs. This multi-functional approach allows the system to achieve the flexibility and isolation capabilities of multiple transformer stages while maintaining the efficiency benefits of a single transformation stage.
3Loss of energy
If a single transformer stage is used to minimize losses, then power processing efficiency is improved, but current matching between multiple outputs deteriorates due to magnetizing inductance tolerance requirements
Solution Approach 1:
The patent segments the inductance function by separating the shunt inductance (Lsh) from the transformer magnetizing inductances. This segmentation allows the transformer magnetizing inductances to be small for efficient ZVS operation while the separate shunt inductor provides the necessary inductance for current matching, eliminating the need for impractically small tolerance requirements on transformer magnetizing inductances.
Solution Approach 2:
The separate shunt inductor (Lsh) acts as an intermediary element that mediates between the primary side and the multiple secondary outputs. It provides the necessary inductance for current matching and balancing without being part of the transformer magnetizing inductances, thereby enabling current matching precision without compromising power processing efficiency through a single transformer stage.
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 configuration enables efficient matching of output currents without requiring precise magnetizing inductance matching, reduces the impact of inductance tolerances, and improves efficiency by processing power through a single transformer stage, resulting in a more compact and cost-effective solution.
Implementation Method 1
an inverter circuit for converting the DC input signal to a square-wave signal
Implementation Method 2
an inductor network coupled to the inverter circuit
Implementation Method 3
each transformer including a primary winding and a secondary winding. The primary windings of the transformers are coupled in series, and the series-coupled primary windings are coupled in parallel with the inductor network
Implementation Method 4
resonant capacitor 15
Data Source
AI summary
In a first aspect, an LLC resonant converter is provided for driving a plurality of output circuits from a DC input signal. The LLC resonant converter includes: (a) an inverter circuit for converting the DC input signal to a square-wave signal; (b) an inductor network coupled to the inverter circuit; and (c) a plurality of transformers, each transformer including a primary winding and a secondary winding. The primary windings of the transformers are coupled in series, and the series-coupled primary windings are coupled in parallel with the inductor network. The secondary winding of each transformer is coupled to and provides a current to a corresponding one of the output circuits. The secondary winding currents are substantially equal, and power is processed by a single transformer between the DC input signal and each output circuit. Numerous other aspects are also provided.