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With the development of portable electronic products, the requirement for chargers is also getting higher. In this paper, a high-accuracy constant output current/constant output voltage (CC/CV) ac–dc flyback converter is proposed and a novel cable compensation method without external capacitor is put forward. The converter adopts primary-side regulation (PSR) scheme, detecting the output voltage through the auxiliary winding, and adjusting switching frequency to achieve output voltage constant in CV mode. Compared to conventional cable compensation module, the proposed circuit applies a method of pre-filtering, averaging, and re-filtering, to obtain the compensation voltage. This method eliminates the need of external capacitor, reducing cost and increasing reliability of the converter. In CC mode, the switching period is adjusted to be fixed multiple of the demagnetization time, thereby realizing the constant current output. The control chip was implemented in NEC 1 μm HVCMOS process, and a 5-V/1-A prototype has been built to verify its feasibility. Experimental results show that the deviations of output voltage and current are within ±0.9% and ±3% under different inputs and loads, while maximum conversion efficiency can reach a level of 78.2%. [ABSTRACT FROM AUTHOR]

This paper proposes a high-precision primary-side regulation constant voltage (CV) and constant current (CC) ac–dc converter. CV output is achieved by adjusting the switching frequency and primary peak voltage simultaneously, for better dynamic adjustment ability. In order to improve CV precision, a cable compensation module is adopted to inject current to pull-down resistor of auxiliary winding divider, compensating the cable voltage loss caused by the output cable resistance. On the other hand, CC output is acquired by maintaining the ratio of switching frequency and output voltage constant. The inductance compensation module regulates further to keep the product of demagnetization time and switching frequency fixed, equalizing the inconsistent output current result from the big tolerance of the transformer primary-side inductance in the same batch. Moreover, an improved demagnetization time detector is proposed, which is beneficial to raise CC precision. The control chip is implemented based on TSMC 0.35-μm 5-V/40-V BCD process, and a 12 V/1 A prototype has been built to prove the proposed control method. In CV mode, the deviation of the output voltage is within ±1.5%, while that of output current is within ±3% in CC mode. [ABSTRACT FROM AUTHOR]