Secondary power supply for in-car audio equipment - has capacitor pack across battery with discharge resistor and short circuiting switch, controlled by state of charge

摘要

A secondary power supply for audio equipment in vehicles has a capacitor pack (23) between the main positive (16) and negative (19) rails, the terminals (17, 20) being directly adjacent to the pack to avoid resistive loss. The capacitance of the pack is between 0.6 and 1.2 farad, pref. 0.9. The negative rail is earthed to the chassis. The output terminals (21, 22) for the ancillary equipment are block terminals, the negative one being connected to a common earth rail. The positive one has separate fuses for each load circuit, joined at a subsidiary terminal. The capacitor pack is joined to the positive supply by a resistor (27) in parallel to a short circuiting switch (29), activated by control unit (25) according to its state of charge. ADVANTAGE - No long cable paths so no resistive drop.