بهبود مدار الكتريكي مبدلهاي ZVZCS تمام پل از نوع PWM

چكيده انگليسي :

Improved Zero Voltage and Zero Current Switching FullBridge PWM Converter Mohsen Packnezhad m packnezhad@ec iut ac ir 2010 03 16 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc language Persian Supervisor H Farzanehfard hosein@cc iut ac ir J Ghaisari ghaisari@cc iut ac ir Abstract Certainly an important part of every electronic equipment is the power supply There are two types of power supplies linear power supplies and the switch mode power supplies Linear power supplies have high conducting loss which results in low efficiency Therefore application of linear power supplies is usually limited to low power cases which is cost effective to implement In the switching power supplies conducting losses are low and frequencies 2 HH which results in reduced size of magnetic elements such as transformers and output filter this type of power supplies can be used for medium and high power applications too They operate in high inductors Many circuit topologies are introduced for switching power supplies For high power applications Full Bridge FB converter has received considerable attention Usually FB converters are controlled using PWM Pulse Width Modulation or PS PWM Phase Shift PWM techniques The PWM controllers typically operate under hard switching and the PS PWM controller operates under soft switching condition Soft switching can be achieved by either ZVS zero voltage switching or ZCS zero current switching In the ZVS FB PWM converters switches operate under zero voltage Zero voltage at turn on switching instances is achieved by using the transformer leakage inductor to discharge the output capacitance of switches thus body diode of switches will conduct before turn on instant Zero voltage switching at turn off instant is achieved by applying snubber capacitors for switches ZVS FB PWM is implemented without any extra components So it is very attractive for high frequency applications where power MOSFETs are used as the power switches However these converters have several disadvantages They operate with large circulating current during the freewheeling period which increases the conduction losses Also the ZVS range of leading and lagging legs are different The ZVS range of lagging leg switches is not wide enough unless the leakage inductance is large This would cause duty cycle loss and severe secondary parasitic ringing Also in this converter IGBTs are not usually applied for the lagging leg switches because of tailing current losses If the lagging switches can operate under ZCS turn off conditions the leakage inductor can be minimized So the transfer of power is maximized and the effective duty cycle can be increased In the ZVZCS FB PWM converters the basic topology is the same as ZVS FB PWM converters with the auxiliary components or an auxiliary circuit being added to minimize freewheeling interval The switching mechanism of leading leg is the same but the lagging leg switches operate under ZCS conditions The negative voltage is applied to the leakage inductance of transformer during the freewheeling interval and the primary current is reduced to zero So the switch current becomes zero before the gate signal forces the switch to turn off In recent years many ZVZCS FB PWM converters are proposed which the primary current is reset in different ways by auxiliary circuits In one of these converters the active clamp is applied as the auxiliary circuit The primary current is reset by an active clamp in the secondary side In this converter high clamp capacitor voltage is applied to the leakage inductor and thus the primary current is reset in a minimum time Also the severe secondary parasitic ringing is absorbed by clamp capacitor and the rectifier voltage is clamped The hard switching operation of the clamp switch is the main drawback of this converter Since this switch operates at twice the converter switching frequency the efficiency of the converter decre

پاكنژاد، محسن

بهبود مدار الكتريكي مبدلهاي ZVZCS تمام پل از نوع PWM

منابع تغذيه سوئيچينگ , سوئيچينگ نرم , مبدلهاي تمام پل تحت ولتاژ صفر , جريان صفر مدار كلمپ اكتيو , مدار كلمپ پسيو