Half-Bridge Power Supply Frequency Control
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Solution Overview
Problem
Existing power supply systems for ballasts and inverters face challenges in achieving high power factor, low crest factor, and maintaining constant output while minimizing electromagnetic interference and power loss, especially when frequency varies, leading to inefficient lamp operation and short lifespan.
Innovation Solution
A power supply apparatus using a half-bridge circuit that includes line voltage detection, error amplification, pulse width modulation, and dead time control to vary frequency and pulse width, ensuring constant output and high power factor without additional high-power factor circuits, thereby improving efficiency and extending lamp life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If frequency is raised to achieve high power factor and low crest factor, then power factor is improved, but efficiency of resonance circuit deteriorates and EMI noise increases
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The controller dynamically adjusts the switching frequency of the half-bridge circuit based on operating conditions to maintain optimal resonance characteristics. This resolves the contradiction by allowing frequency to be raised when needed for power factor correction while being lowered when resonance efficiency would deteriorate, thus adapting to different operating states rather than being constrained to a single fixed frequency approach
Solution Approach 2:
The patent changes the parameter of switching frequency from a fixed value to a variable parameter that can be adjusted according to operating conditions. By implementing frequency modulation capability in the half-bridge circuit, the system can optimize the balance between power factor improvement and resonance circuit efficiency, avoiding the permanent trade-off present in fixed-frequency designs
2Ease of manufacture
If frequency is raised to achieve high power factor and low crest factor, then power factor is improved, but electro-magnetic interference noise increases
Solution Approach 1:
The patent uses dynamic frequency adjustment to prevent EMI noise generation. By monitoring operating conditions and adjusting the switching frequency in real-time, the controller avoids operating at frequencies that would generate excessive EMI while still achieving the necessary power factor correction. This dynamic approach allows the system to navigate around EMI-prone frequency regions rather than being stuck at a fixed high frequency that consistently generates noise
3Ease of manufacture
If frequency is raised to achieve high power factor and low crest factor, then power factor is improved, but power loss of switching device increases
Solution Approach 1:
The patent implements parameter changes by making the switching frequency a variable parameter rather than a fixed design value. The controller adjusts the frequency based on load conditions, input voltage, and other operating parameters to minimize switching losses while maintaining power factor correction benefits. This allows the system to operate at lower frequencies when possible to reduce switching device power loss, and only increase frequency when necessary for power factor maintenance
4Ease of manufacture
If frequency is raised to achieve high power factor and low crest factor, then power factor is improved, but energy supplied to filament increases and lamp tube life is shortened
Solution Approach 1:
The patent applies dynamics by dynamically controlling the switching frequency to prevent excessive energy delivery to the lamp filament. The controller monitors lamp operating conditions and adjusts frequency to maintain appropriate power levels, avoiding the continuous high-frequency operation that would overheat and shorten lamp life. This dynamic control ensures power factor improvement without the harmful side effect of accelerated lamp degradation
5Ease of manufacture
If output is controlled by varying only frequency, then power factor is improved, but output control dynamic characteristic is low and feedback circuit setting is difficult
Solution Approach 1:
The patent transitions from one-dimensional control (frequency only) to two-dimensional control by introducing pulse width modulation as an additional control dimension. The half-bridge circuit now controls output power through both frequency variation and pulse width adjustment, providing much finer control resolution and improved dynamic characteristics. This dimensional expansion of the control space allows for sophisticated feedback control that was impossible with frequency-only modulation
Data Source
AI summary
Disclosed is a power supply apparatus using a half-bridge type driving circuit, which is intended for the purpose of the compensation of a power factor, the achievement of a low crest factor and the maintenance of a constant output. The power supply apparatus using a half-bridge circuit for rectifying an AC power source and providing the rectified power source to a load includes a line voltage detecting means for detecting a voltage of an input power source provided to the load, an error amplifying means for comparing the voltage detected from the line voltage detecting means with a reference voltage and outputting a voltage corresponding to a difference therebetween, a pulse width modulating means for outputting a pulse having a variable width corresponding to an output level of the error amplifying means, a dead time controlling means for outputting a first pulse corresponding to a high side and a second pulse corresponding to a low side by the pulse output from the pulse width modulating means, wherein the first and second pulses have different pulse widths and different rising and falling time points, and a driving means for driving the power source supplied to the load as a constant current state by the first and second pulses.