The opto-coupler is usually used for isolated resonant converter to feedback the secondary-side output information. However, the characteristics of the opto-coupler are easily affected by the operating conditions, which will cause higher standby power loss. In this article, a novel primary-side controlled isolated half-bridge resonant converter with output voltage and current estimation for LLC and series resonant converter (SRC) operations is presented. The output voltage is estimated by sampling the auxiliary winding voltage when the output diode current flows to zero, the output current is estimated by integrating the resonant current until the transformer decoupled. The operating principles of the half-bridge resonant converter and the design criteria of the key component parameters are addressed and analyzed. Also, the methods for estimating output voltage and output current are discussed in detail. Finally, an experimental prototype with rated power 100 W half-bridge resonant converter for input voltage 280-342 V and output voltage 24 V is built with microcontroller to validate the proposed primary-side regulation technique. Experimental results show the output voltage and current can be controlled with the error less than 1% and 8%, respectively. The highest efficiency of the system is 95.2%.
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