PRC-BC4-MS 4-1
Chapter 4: Technical Description
This chapter provides a detailed description of the circuitry that the PRC-BC4
uses to charge BB-LA6 batteries.
4.1 Input Power
The PRC-BC4 derives input power for either an AC (110 or 220 VAC) or DC
(20 to 30 VDC) power source. Both power sources are switched using the front
panel POWER switch.
4.1.1 AC Power Supply
The internal AC power supply uses a standard, monolithic full-wave diode
bridge as the rectifier. The power transformer uses a split primary coil
configurable for a 110 or 220 VAC power source. The phase line is switched
and fused.
Capacitors C14, C15 and C16 form the AC filter circuit that limits ripple to
about 2 Vpp at the full rated output. Switch S5 is a normally-closed thermostat
that opens at approximately 167° F (75° C). The thermostat switch is wired in
series with DC fuse F2 so that if the chassis temperature exceeds the 167° F set
point, the PRC-BC4 temporarily turns off.
The Display board includes transient-absorbing diode D13, that provides
protection against large spikes. If D13 detects a transient greater than 32 VDC,
it goes into short mode, pulling the raw DC supply line to ground, which causes
the fuse to blow.
4.1.2 DC Power Supply
The PRC-BC4 can operate from a 20 to 30 VDC DC power source. The DC
power line is also filtered with capacitors C14, C15 and C16. Diode D5
provides reverse-current protection so that current does not flow to the DC
input connector when the PRC-BC4 is using an AC power source.
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