ZOLL Base Powercharger 4x4, Руководство по обслуживанию

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FUNCTIONAL DESCRIPTION
IV-4
DC Power Bus Circuitry
All four charging compartments share an unregulated 30V DC Power Bus which is
used by each compartment as the power source for its switching power supply control
circuit. This DC bus is created from a 24Vac input which originates from a chassis
mounted transformer and enters the board via 2 pin connector J3. This AC input is
rectified by bridge BR1 and filtered by capacitors C133, C233, C333 and C433. Any
transients from the line which are not eliminated by the filter capacitors are absorbed
by the metal oxide varistor TV1. JP8, R42, R43, R44, and D11 dissipate energy
stored on the caps when AC is turned off. JP8 allows this dissipation circuit to be
disabled.
+12Vdc Supply
U3 with R7 and R8 provide a regulated 12 volts used to operate the alarm. C1
provides RF bypassing. C2 is a voltage filter capacitor. D1 is a reverse current
protection diode. JP7 provides the user with the ability to select where the raw
voltage comes from for the alarm.
Logic Power Supply
A +5V +/- .25V power supply is produced from the +24Vac input (originating from
connector J3) to power the analog and digital circuitry on the board. D4 and D5 along
with C8, R9, and C3 rectify and filter this AC input voltage providing an unregulated
30Vdc input voltage for the fixed +5V output switching regulator U4. U4 along with
D3, L1, C5, C6, C7 and R11 are implemented in a "buck" configuration. D2 provides
a final over voltage protection for the logic supplies. For more details on "buck"
converter operation see Switchmode Power Supply section.
Reference Voltages
A two terminal, 1.235V band gap reference (U9) is used to create all of the reference
voltages that are routed to the charging compartments. U9 is biased by R27 and
buffered by amplifier U8B. C25 is an RF filter capacitor.
A second temperature compensated reference is created from device U9 to set the
constant voltage mode output of each charger compartment. The positive input of
amplifier U8A is referenced to the sum of U9 and the voltage across signal diode D10.
Resistors R25, R26, R28 and potentiometer RV1 set the nominal gain of the amplifier
to a range of 1.48 - 1.72. C24 and C27 provide RF filtering. C23 provides power
supply filtering and bypassing. The voltage developed across the silicon diode varies
inversely to ambient temperature. This diode characteristic causes the reference
circuit to automatically adjust the CV charge voltage down as temperature rises which
is in accordance with the recommendations of the lead-acid battery manufacturer.
Amplifier U6A, along with gain resistors R22 and R23, are used to create a third 3.3V
reference voltage. C18 and C19 provide RF filtering. C20 provides power supply
bypass and filtering. This reference voltage is bussed to an A/D input of each charger
compartment's microprocessor and used to verify the accuracy of the VCC supply
voltage (refer to VCC Test Circuitry Section for more details). This self-test feature
insures that all A/D readings are accurate and not corrupted by a faulty VCC supply
voltage.