科研之友
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摘要
Single-stage boost-LLC ac-dc converters are popularly utilized as the front-end stage of multichannel LED street-lighting drivers. Pulse frequency modulation (PFM) strategy with a duty cycle of 0.5 is commonly utilized in these ac-dc converters. However, PFM has the following drawbacks: 1) high bus voltage limits the ac input voltage range, which makes it only suitable for the input voltage range of 85 similar to 135 V and 2) the maximum bus voltage can reach up to three times of the minimum bus voltage, which increases the difficulty of the LLC design. This paper proposed a hybrid modulation strategy, which consists of a bus voltage control loop using asymmetric pulsewidth modulation and an output voltage control loop using PFM. The stable output voltage and the quasi-constant bus voltage can be simultaneously achieved. Furthermore, by increasing bus voltage ripple and employing the twin-bus configuration, the short-lifetime electrolytic capacitors are eliminated, and the efficiency of the total LED driver can be greatly improved. Therefore, universal-input operation, high efficiency, low cost, and long lifetime are the key innovations of the proposed solution. A universal-input 100-W prototype is built to demonstrate the feature of the proposed solution. The experimental results show that the converter achieves a peak efficiency of 92.5% at the input voltage of 130 V and a high power factor value of above 0.95 over the whole input voltage range. With the proposed modulation strategy, the maximum bus voltage is just 500 V under universal input voltage condition, which is greatly lower than that of the traditional PFM controlled boost-LLC converters.
- 出版日期2018-9
- 单位西南交通大学
