Battery glow in a tube amplifier. Battery switch with discharge control. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Battery glow in a tube amplifier. Battery switch with discharge control. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Tube Power Amplifiers

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The switch is powered by its own low-power +12...20V power supply. The number of switched batteries is not limited (the diagram shows two batteries; when switching more than 4 batteries, it is advisable to replace bipolar optocouplers with MIS optocouplers of the K293KP series). In the on state, the batteries are galvanically isolated, in the off state they are paralleled to an external charger through equalizing resistors R6. The memory is not shown in the diagram, its combination with the switch is possible, but it is advisable only with a small total battery capacity.

(click to enlarge)

When power is applied to the switch circuit, the R2C2 circuit supplies an unlocking voltage to the T1 gate, the filament relays connect the batteries to the filament circuits. With sufficient voltage on each of the batteries, a series chain of optocouplers shunts C2, holding T1 and filament relays in the open state (optocoupler transistors in saturation, optocouplers output current of at least 3mA). In the opposite case (deep discharge or short circuit - optocouplers current less than 1mA), C2 continues to charge and after 1s T1 closes, the circuit goes into protection mode, indicated by LED D5. The threshold for the comparators (IC2) is set at 5.8...6.0 V. In principle, it is sufficient to have one comparator connected to the battery operating with the highest load current in the circuit. T1 in the open state also supplies power to the time relay R4C4-T2, which delays turning on the anode power supply of the amplifier (40..60s with the indicated ratings). The anode relay is turned off synchronously with the glow relay (with voltage drop on the time-setting capacitance).

Structurally, the circuit consists of a "dirty" and a "clean" part (respectively, the left and right parts of the circuit), the "dirty" part is mounted on a separate board directly next to the power switch. It is possible to shunt the filament outputs with capacitors (both on a "clean" board and directly near the lamps), but this is already the area of \uXNUMXb\uXNUMXbexperiments with sound.

Relay - for the voltage of the primary winding 12V with two switching groups (P1 can be with one closing group). The rating of equalizing resistors (R6) is set based on the voltage drop of 200..300 mV at voltage and charge current in standby mode. The divider rating R7-R9 and R10 are indicated for 6.3V batteries. Transformer TR1 can be 9V, this is enough to drive a 12V relay, while the Zener diode D2 is replaced with a 9V one. Optocouplers - any bipolar (not Darlington) with a transfer coefficient from 1/4 to 2. T1, T2 - any low-voltage N-MDP with a channel resistance of at least 0.5 Ohm.

The current through the protection indicator R2D5, flowing through the relay windings in the protection mode, should not lead to the relay being held in the on position. For guaranteed closing of the relay for a rated voltage of 12V, the voltage drop across the winding should not exceed 2V. The R2 rating is indicated for a total winding resistance of at least 100 ohms and a supply voltage of +15V.

An alternative (not implemented) version with a single battery and built-in memory (IC1, T1) for powering the preamplifier-corrector filaments. The power supply is always on, the circuit is switched to the "charge" mode by briefly opening the normally closed Standby switch, returns to the "on" mode by briefly closing the normally open On / Reset switch.

(click to enlarge)

The charge current is limited by the internal resistance of the power source (TP1...C4). TP1 for 9V, 1A, D9 for 9V, relay for 5V, D8 - Schottky with a small voltage drop per current from 5A, other elements - as in the previous circuit.

Publication: klausmobile.narod.ru

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