Some power supplies for phones with Caller ID has one drawback - when a discharged battery is not going on her trip. Thus normal operation of the stabilizer block power is not possible due to low voltage at its input. Phone periodically turned on and off, which can lead to unwanted consequences. Offers a very simple power supply, devoid this drawback, namely, at a voltage reduction on battery below 6.5 (the minimum voltage at which the regulator is operable) occurs it disconnects. Diagram of the device shown in the figure.
When AC power is included in the network, triggered relay K1, which is the sensor of discharge of the battery (used hysteresis relay). Through the resistor R2, the charging current flows 5 10... mA. With the loss of voltage opens the diode VD2 and power flows battery GB1. If the voltage across it falls below 6.5, the relay is released and the contacts K1.1 turn off the battery.
The battery consists of six series-connected elements D-0.55. A fully charged battery provides the phone for hours, which is quite enough during short-term outages.
Relays used stamps RES-64A (passport RS4.569.724).
Establishing device is reduced to the selection resistor R1, which is set voltage release relay K1, and selection resistor R2 is they set the charging current of the battery GB1.
To maintain battery GB1 charged sufficient current of about 200 μa. The specified current 5...10 mA can cause overcharging of the battery.Publication: N. Bolshakov, rf.atnn.ru