AUTOMATIC PROTECTION OF ELECTRONIC CIRCUITS

Electronic devices based on microprocessors and integrated circuits are less sensitive to the parameters of the supply voltage. To ensure the safe operation of these devices use voltage regulators with protection. In many power supplies is reduced to cut power to the circuit if a short circuit in it or a sudden increase in load current. Such, for example, the popular voltage stabilizers КР142ЕН5.

“Minus” of such stabilizers is that they too are inert in the protection mode: triggered (stop the power supply to the circuit) going through the 200 — 500 MS and strongly depends on the nature of current change in the load on an abrupt increase in the current simple knots stabilizers react, and they tend to be smooth. Inertia protection is enabled within 200 MS can cost the owner dearly. In the literature published protective circuitry, responsive to the change in load current 100 not faster (nanoseconds), this is a very good indicator. However, they contain many elements and complicated for novice radio Amateurs. The author developed a more simple protection, triggered even with a smooth change of load.

 

To repeat the proposed scheme can any Amateur radio operator. The node contains only one microspore КМП201УП1А does not require any configuration and adapts to any power source with a common negative wire. I recommend to embed the node in every home a power source for electronic works, and especially in those voltage sources that provide expensive components of electronic devices. Powered device DC stabilized voltage 4… 6 V, in “normal” standby mode consumes from the power source current of 0.8 mA. Through the normally closed contacts of the relay K1 is energized from the power supply unit (PSU) is supplied to the protected electronic circuit.

While the voltage at the circuit’s input does not exceed the divider resistor R1 limit at pin 6 microbore voltage close to zero. As soon as the set limit is exceeded with the output 6 to the control electrode of the thyristor VS1 is voltage 2/3 of the Un. The thyristor opens and remains open until circuit is not powered, or not broken his chain anode or cathode. Relay is enabled, thus the power supply to protect the circuit terminated. This voltage drop is, and is perceived by node protection. The sensing node can also be used in other cases when an urgent response is required to increase the voltage across the resistor R1 is several mV. For example, using the node as the control scheme for the ULF, get the amplifier with acoustics is automatically activated when a signal appears at the input. For this application low-power relays should be connected directly between the DA1 terminal 6 and ground. For switching the load to use the contacts on the circuit (box on the diagram shown by the dotted line). Input sensitivity is adjustable R1.

 

 

Schematic diagram of the node protection

 

The thyristor VS1 can be replaced КУ101Б. Any relay K1 low power, triggered by voltage 3…4 V. For this purpose a convenient reed relays. If there is no such, you can make yourself. On a low-power reed switch with normally open contacts in bulk wound 200 turns of transformer wire PEL with a diameter of 0,1 mm. This coil is a homemade relay coil and switch contacts — normal contacts of the reed switch. This relay is actuated at low voltage supply 2 4…and consumes up to 50 mA. Therefore, it is designed to work in pulsed mode and to replace the K1 in our scheme is well suited. Fixed resistors type MLT-0,5. Capacitors C2, C3 type, KM or similar. Electrolytic capacitor C1 type C50-6. Chain shown in the diagram by the dotted line, checks the site, and forced on defense. To disable short-term protection is necessary to break the power circuit of this diagram by pressing the button S1. Now the device is once again testing the input voltage and is ready to enable protection.

 

A. KASHKAROV, St. Petersburg