What is the purpose of a diode? What characteristic of a diode makes it a component used in most electronic devices?
Introduction to Diode
Among the devices used in power electronics, the diode is the simplest. Diode is a semiconductor device, it only allows current to pass through it when forward biased. Diode consists of 2 pins: Anode and Cathode, current can only flow through it in one direction from Anode to cathode.
+ When the voltage VAK > 0, the diode is forward biased, so it conducts.
+ When the voltage VAK < 0, the diode is reverse biased so it does not conduct.
The voltage drop across the diode is about 0.7V, so in the field of power electronics, when the diode conducts, it acts as a closed switch. When the diode is not conducting it acts as an open switch. With this characteristic of the diode, it has many applications in life.
2. What is the purpose of a diode
Diodes are components that appear in most electronic devices. Such as television, computer, phone, charger, power supplied, welding machine, printer…
The main purpose of a diode is to be used in rectifier circuits, to convert AC voltage into DC voltage. In addition, the diode is also used to protect against power reverse, fly back diode, voltage drop circuit, signal transmission.
2.1 Rectifier circuit
Diodes are used in rectifier circuits
Rectification is the main purpose of the diode, the characteristic of the diode is that it only allows current to flow in one direction. We design a rectifier circuit as shown in the figure. AC input voltage (Vin) has a sine waveform. The voltage after rectification will be DC voltage (output voltage is always positive).
The output voltage can be used to power DC equipment. Or this DC voltage is then converted to AC voltage which can be changed frequency (inverter).
2.2 Reverse power protection
Reverse power protection circuit using diode
In DC voltage applications, diodes can be used for reverse power protection. This is very important, because some components do not allow negative voltage to be applied to it. By connecting the diode to the positive terminal of the DC source as shown above.
+ When the power source is connected in the correct direction, the current passes through the diode, the circuit works normally.
+ When reversing the polarity of the power source, the diode does not allow current to flow through, the circuit is open.
2.3 Voltage reduction circuit
Voltage reducing circuit
The voltage drop on each diode is from 0.5 – 0.7V, we can connect the diodes in series to create a voltage-reducing circuit with a small capacity. As shown above, the IC uses a 3.3V supply, so we connect 3 diodes in series to reduce it from 5V to 3.3V.
2.4 Light emitting diode
In addition to the function of emitting light, the light-emitting diode (LED) is also used to transmit control signals such as in optocouplers or remote controls.
Diode used inside optocoupler
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