The half bridge converter is similar to the push pull converter, but a centre tapped primary is not required. The reversal of the magnetic field is achieved by reversing the direction of the primary winding current flow. This type of converter is found in high power applications.
For the half bridge converter, the output voltage Vout equals the average of the waveform applied to the LC filter
Vout = (Vin/2) x (n2/n1) x f x (Ton,q1 + Ton,q2)
whereVout=Output Voltage - Volts
Vin=Input Voltage - Volts
n2=0.5 x secondary turns
n1=primary turns
f = operating frequency - Hertz
Ton,q1 = Q1 conduction time - Seconds
Ton,q2 = Q2 conduction time - Seconds
Note that Ton,q1 = Ton,q2 and that Q1 and Q2 are never conducting at the same time.
The control circuit of a half bridge converter is similar to that of a push-pull converter
Source : http://www.hills2.u-net.com/electron/smps.htm
