The charging circuit current is adjustable between 0 and 5A. The output voltage is pulsed for fast charging. Additionally, an integrated voltage monitor automatically reduces the charging current when the battery voltage reaches 14.4V, allowing only trickle charging to continue.
Triac Charger Circuit Operating Principle
Contents
The regulation section, consisting of diodes D3–D6, fixed voltage regulators IC1 7812 and IC2 7912, and capacitors C1–C6, generates the +12V and –12V supply voltages required by the control electronics.
Current control is based on a phase-controlled structure. The firing angle of the BT138 Triac TC1 is adjusted according to the necessary conditions via the feedback of the control circuit. This process works step-by-step as follows:
The voltage across the reference resistor R1 is directly proportional to the current flowing through it according to Ohm’s law. An average value is obtained from this voltage using the R8/C8 RC group, and this value is applied to the (+) input of OP2 via R9.
OP2 compares this average voltage at its (+) input with the reference voltage adjusted by potentiometer R10 and applied to the (–) input of OP2 via R13. The output of OP2 adjusts itself to reduce the difference between the two inputs to zero.
The actual triggering control is performed in the following section. The T1 transistor, along with resistors R19–R21, capacitors C11–C12, and diode D9, forms a sawtooth wave generator.
This generator starts operating at every zero-crossing of the mains voltage, and its amplitude increases from zero volts towards the negative supply direction. The maximum amplitude of this sawtooth wave is not critically important; what matters is the correct creation of the curved structure that determines the triac’s firing timing.
Triac Charger Circuit Diagram
Triac Charger Printed Circuit Board
Source de.elv.com/p/universelles-ladegeraet-fuer-auto-akkus-P204179/
