Resonant Hybrid Flyback Converter With Primary-Side LED Current Estimation
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Solution Overview
Problem
Resonant hybrid flyback converters face challenges in efficiently regulating load current while avoiding expensive signal transfers across safety extra low voltage (SELV) barriers.
Innovation Solution
A resonant hybrid flyback converter is designed with a control circuit that senses resonant and magnetizing currents through primary-side inductance using dedicated sensing circuits, allowing for estimation and regulation of light source current without direct sensing across the SELV barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct sensing across SELV barrier is used for load current regulation, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary approach by sensing primary-side currents (resonant current via shunt resistance and magnetizing current via integration circuit) instead of directly sensing secondary-side load current. These primary-side measurements serve as proxies to estimate the load current, eliminating the need for expensive isolated signal transfer while maintaining adequate measurement precision for regulation purposes.
Solution Approach 2:
The patent creates a copy of the load current information by measuring related primary-side currents and estimating the load current from these measurements. Instead of directly measuring the actual load current across the SELV barrier, the system creates an estimated copy using primary-side sensing circuits, which is sufficient for control purposes and avoids the complexity of direct sensing.
2Measurement precision
If direct sensing across SELV barrier is implemented, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive isolated sensing components with cheaper primary-side sensing circuits. The shunt resistance and integration circuit are simple, low-cost components that can be implemented without expensive isolation barriers, significantly reducing manufacturing cost while providing sufficient measurement capability for load current regulation.
3Device complexity
If primary-side current sensing is used, then device complexity is reduced, but measurement precision may deteriorate
Solution Approach 1:
The patent implements a feedback mechanism where the estimated load current derived from primary-side sensing is fed back to the control circuit for regulation. The control circuit uses this feedback to adjust the resonant tank circuit operation, ensuring that despite the indirect measurement approach, the actual load current is accurately regulated to the desired setpoint, thereby maintaining effective measurement precision.
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 efficient regulation of light source current while eliminating the need for expensive signal transfers across the SELV barrier, thereby improving cost-effectiveness and operational efficiency.
Implementation Method 1
The resonant tank circuit may, for example, comprise a transformer's main inductance and leakage inductance (or a separate resonance choke) and a resonance capacitance in series
Implementation Method 2
a transformer, comprising a primary-side inductance and a secondary-side inductance
Data Source
Figure 1
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AI summary
Disclosed is a resonant hybrid flyback converter (1) for a light source (2). The converter (1) comprises a transformer (101, 102), comprising a primary-side inductance (101, Lp) and a secondary-side inductance (102, Ls). The converter (1) further comprises a high-side switch (103) and a low-side switch (104), connected in series between an input electric potential and a primary-side ground electric potential of the converter (1). The converter (1) further comprises a resonant tank circuit (101, 105), connected in series between a common electric potential of the switches (103, 104) and the primary-side ground electric potential. The resonant tank circuit (101, 105) comprises the primary-side inductance (101, Lp). The converter (1) further comprises a first sensing circuit (110-113); a second sensing circuit (120-125); and a control circuit (130). The control circuit (130) is configured to sense, via the first sensing circuit (110-113), a first voltage (140) being indicative of a resonant current (141, Ires) through the primary-side inductance (101, Lp). The control circuit (130) is further configured to sense, via the second sensing circuit (120-125), a second voltage (142) being indicative of a magnetizing current (143, Imag) through the primary-side inductance (101, Lp). The control circuit (130) is further configured to estimate a current (146, ILEDest) through the light source (2) in accordance with the first voltage (140) and the second voltage (142). The control circuit (130) is further configured to regulate the current (148, ILED) through the light source (2) in accordance with a setpoint value (147, ILEDref) and the estimated current (146, ILEDest) through the light source (2). This avoids a sensing of the current (148, ILED) through the light source (2) and an associated signal transfer across a SELV barrier of the converter (1).