Showing papers by "Jee-Hoon Jung published in 2008"

Novel techniques of the reduction of standby power consumption for multiple output converters

Abstract: Recently, the reduction of a standby power consumption is significantly issued in the electronic and electrical industry for the conservation of environment. In the case of a switched mode power supply (SMPS), it is demanded high efficiency at extremely low load conditions by consumers. However, it is very different from high efficiency techniques at full load conditions. In addition, many SMPSs are designed as a multi-output circuit for various loads because of the cost down. This circuit is difficult to implement both the high efficiency and good cross regulation performance, simultaneously. In this paper, novel secondary side post regulator (SSPR), current mode control method, and power sequence control technique are proposed to reduce standby power consumption and to improve the cross regulation performance of the multi-output SMPSs which consist of a single or multiple converter. The proposed methods are analyzed by their operational principles and optimal designs verified by experimental results with 110 W and 270 W SMPSs.

Soft switching and optimal resonance conditions of APWM HB flyback converter for high efficiency under high output current

Abstract: The soft switching and optimal resonance conditions of the asymmetrical pulse-width modulated (APWM) half-bridge (HB) flyback converter for high efficiency under high output current are proposed. This converter can operate under high efficiency by using soft switching techniques such as the zero-voltage switching (ZVS) of primary power switches and the zero-current switching (ZCS) of output rectifiers. Under high output current condition, however, the converter satisfied with the ZCS of output rectifiers does not always have higher efficiency than no ZCS cases. The ZCS condition grows the rms value of the output rectifier current to finish its resonance operation transferring power from the primary side to the secondary. This high rms current increases the conduction loss of the transformerpsilas secondary wire and output rectifier, especially the synchronous rectifier (SR). Therefore, the resonance should be considered by several factors such as the conduction loss of the output rectifier and its reverse recovery loss. Experimental results using a 300 W APWM HB converter are obtained to verify the suggested efficiency-optimal conditions by demonstrating the efficiency data of the converter under load variations.

Switching power source apparatus and control method thereof

Abstract: A switching power source apparatus includes a storage unit to store energy obtained from input power supplied to the storage unit, and to output at least of the stored energy as output power; a first switch; a second switch connected in series with the first switch, the series connection of the first switch and the second switch being connected to the storage unit; and a voltage clamp unit to clamp a level of a voltage applied across the series connection of the first switch and the second switch to a predetermined voltage or less. The first switch is turned on while the second switch is still turned off, and then the second switch is turned on after the first switch has been turned on to supply the input power to the storage unit from the series connection of the first switch and the second switch.

Switching mode power supply apparatus having passive clamp circuit

Abstract: A switching mode power supply apparatus includes a transformer, a main switch to adjust power supplied to a primary coil of the transformer, a passive clamp circuit to suppress a voltage stress of the main switch, and a control circuit to disable a clamping operation of the passive clamp circuit in a standby mode of the switching mode power supply apparatus. Power is not consumed in the passive clamp circuit in a standby mode so that power consumed in the standby mode can be remarkably reduced.