The relay is connected to the diode
The relay coil is an inductor that has the effect of preventing current changes. Especially when the coil from the current into no current, because the self-inductance will produce a reverse electromotive force. Relay coil at both ends of the role of the diode, is to suppress the reverse electromotive force. When the reflected voltage is generated, you can through this diode, the current discharge, protect the circuit to run properly, without damage.
Since the coil of the relay is the original of the inductive current, the coil will generate self-induced electromotive force when the current flows through the coil. According to Faraday's law, the magnitude of the self-inductance electromotive force is proportional to the rate of change of the current through the coil (coil flux change rate). So when the power off instantaneous current rate of change is very large, the coil will produce higher than the power supply voltage several times the self-inductance electromotive force and superposition with the power supply voltage (self-inductance electromotive force can be determined according to Leng's law). If the relay coil ends without diodes, such a high voltage on the circuit will damage the circuit on the transistor and other original devices. So we are connected at both ends of the coil and connected to the diode, and the power of the coil generated by the self-induced electromotive force polarity to meet the two positive conduction conduction to form a continuous flow, the self-induced current discharge to protect the circuit Transistor and other original devices. This is the role of relay diode.
Relay diode function: the diode called "freewheeling diode" due to the role of the circuit in the role of the role of continuous flow, the general choice of fast recovery diode or Schottky diode as a "freewheeling diode", it is in the circuit Generally used to protect the components from the induced voltage breakdown or burnout, in parallel with the way to generate the induced electromotive force of the two ends of the device, and with the formation of the loop, so that the resulting high electromotive force in the circuit to continue the current consumption, The components in the protective circuit are not damaged
Related information:
Freewheeling diodes are often used with energy storage components to prevent voltage and current changes, providing access. The inductor can pass through it to provide continuous current to the load, so as to avoid the load current mutation, play a smooth current role. In the switching power supply, you can see a diode and resistor connected together constitute the freewheeling circuit. This circuit is connected in parallel with the transformer primary side. When the switch off, the freewheeling circuit can release the transformer coil stored in the energy to prevent the induced voltage is too high, breakdown switch. The general choice of fast recovery diodes or Schottky diodes can be used to generate the reverse potential of the coil through the current consumption of the form, we can see "freewheeling diode" is not a substantial component, it is only in the circuit To the role known as "continued flow".
effect:
Relay connected diode refers to the relay freewheeling diode, which is generally used in the circuit to protect the components are not induced breakdown or burnout, in parallel with the way to generate the induction electromotive force components at both ends, and with the formation of the loop, so that The resulting high electromotive force is consumed by the circuit in a continuous current mode, thereby functioning as a component in the protective circuit that is not damaged.
