|
Half Bridge Converter
| Half Bridge
Converter, is basically two forward converters, where one
of them has an inverted PWM polarity, that means that when one
driver is modulating positively the other one is modulating
negatively, in this way transformer can be utilized in both flux
directions, while forward is used just one direction of the
transformer magnetic flux |
| Fig 1 show the basic circuit, C1 and
C2 form a voltage divider by two in order to utilize both polarities
of magnetic flux of the transformer |
| Diodes D1 and D2 rectifier the
forwarded energy from MOSFETS. |
| R3
sense the voltage output and it is compared with voltage reference
Vref. photo isolated transistor then feedback the PWM signal
required to regulate the voltage according to the value of Diode
Zener Vref. + Photo diode Vf (Vf = voltage forward of photo diode) |
| The
size of the inductor and capacitor determinate the switching
frequency and the power output |
Advantages/Applications:
It
is used for:
Providing
high output power and efficient designs
Optimizing
transformer utilization
Can
be used in current mode PWM control
Disadvantages
It
requires 2 60Hz bulk caps
Power
circuit has 2 pole
MOSFET
selection
Vds
> 1.1 Vin(max)
Ids(max)
> 2.0 Po/(n*Vin(min) * Dmax)
Diode
Selection
Ifmax
>= Io(max), If(avg)=0.5Io(max)
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