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MFJ-4416B Super Battery Booster
Instruction and Technical Manual
8
THEORY OF OPERATION
Figure 5: MFJ-4416B Block Diagram
Refer to Figure 3 and the schematic Figure 6 for the discussion of the theory of operation.
The input voltage passes through an input filter consisting of L3 and three 4700 uf
capacitors. This helps keep switching transients from appearing on the input line of the
unit. This filtered positive voltage is then fed to the center tap of the primary and the
secondary of the switching toroidal transformer L1. When the unit is disabled this
voltage appears on the output of the unit less the voltage drop across the dual diode D1.
When enabled the secondary voltage of the toroidal transformer is the input voltage plus
the voltage of the transformer primary windings. By doing it this way the transformer
only needs to supply the difference of the output voltage and the battery voltage. This
reduces the power requirements of the transformer and switching FETs. The output is
then rectified by the Dual Diode D1. Output filtering consists of L2 and six 4700 uf
capacitors. This 28,200 uf of output filtering helps ensure the output is clean from
switching transients. The output is protected by a crowbar circuit consisting of a 15 volt
zener diode D7 and the SCR D6. When a voltage higher than 15 volts is sensed, the SCR
is triggered shorting the output to ground to protect your equipment from damage in the
event of a problem. There are 2 inputs for enabling the unit. The first is a simple switch
that turns the unit on and allows it to continuously run. The second is a RF switch
