Half-Wave LLC Converter Control to Limit Circulating Current
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Solution Overview
Problem
In half-wave rectifier LLC converters, increasing output current leads to an increase in circulating current, which results in reduced efficiency due to increased losses in the resistive components of the secondary side circuit.
Innovation Solution
The half-wave rectifier LLC converter and control IC implement a control method where the resonant switch is controlled twice during the off period of the main switch, with specific timing adjustments to minimize circulating current. This includes a flyback period where the resonant switch is turned on to allow resonant current flow, and a subsequent period where the resonant switch is turned off during the excitation current charging period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the output current is increased, then the power supply capacity is improved, but the circulating current increases and efficiency decreases
Solution Approach 1:
The patent applies dynamic control by adjusting the resonant switch timing based on operating conditions. The controller dynamically sets the resonant switch on-time to extend into the excitation current charging period when needed, optimizing the balance between power delivery and circulating current minimization across different load conditions.
Solution Approach 2:
The patent changes the timing parameter of the resonant switch control. By adjusting the resonant switch on-time to overlap with the excitation current charging period, the patent modifies the operational parameters to reduce circulating current while maintaining power output capability.
2Power
If the on-time of the main switch is increased to increase output current, then the power delivery is improved, but the amplitude of excitation current increases and operating frequency decreases
Solution Approach 1:
The patent utilizes periodic resonant action by controlling the resonant switch to operate during specific phases of the resonant cycle. The resonant switch is turned on during the flyback period and extends into the excitation current charging period, creating a periodic control pattern that manages excitation current amplitude and maintains operating frequency.
3Stability of the object's composition
If the time to send power to the secondary side remains the same, then the power transmission timing is stable, but the peak value of current flowing through the secondary side increases more than proportionally
Solution Approach 1:
The patent achieves continuous useful action by extending the resonant switch on-time to cover both the flyback period and the excitation current charging period. This continuous conduction mode ensures smooth power transfer to the secondary side, preventing current peaks while maintaining stable power transmission timing.
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 approach effectively prevents the increase in circulating current with increasing output current, thereby improving the efficiency of the power supply by reducing losses in the secondary side circuit.
Implementation Method 1
a transformer including a primary winding and a secondary winding electromagnetically coupled with the primary winding with opposite polarity
Implementation Method 2
the resonant current due to the resonant capacitor and leakage inductance transmits power to the secondary side
Implementation Method 3
a rectifying and smoothing circuit that rectifies and smoothes the voltage of the secondary winding
Data Source
AI summary
A first series circuit includes a main switch and a resonant switch. A second series circuit includes a primary winding and a resonant capacitor. A transformer includes the primary winding and a secondary winding. A controller controls the main switch and the resonant switch. A rectifier smoothing circuit rectifies and smoothes a voltage in the secondary winding. An output voltage detector detects an output voltage of the rectifier smoothing circuit. The controller controls the main switch based on a first drive signal. The controller turns on the resonant switch during a flyback period when an energy stored in the transformer is released from the secondary winding based on the second drive signal, which causes a resonant current to flow. The controller turns off the resonant switch during an excitation current charging period in which the energy stored in the transformer charges the resonant capacitor after the resonant current stops flowing.