What is Peak Inverse Voltage & Its Working
- May 25, 2022
We know that there are different types of materials that carry electricity namely Cu, Al, Ge, Si, etc. These materials are called semiconductors which are used in several electronic devices. These semiconductor materials are good conductors for electricity & they include good conductivity. These materials have a slight prohibited gap of 1eV & electrons transfer from one band to another band like valance to conduction. The formation of PN junction diode can be done using the fabrication method of two materials like P-type and N-type. This diode can be made with Silicon material so known as a Silicon diode. This article discusses an overview of a peak inverse voltage (PIV).
What is Peak Inverse Voltage?
When the PN junction diode resists the utmost value of the reverse voltage without harming itself is called it’s PIV (Peak Inverse Voltage). The rating of PIV can vary based on the manufacturer. But, if the voltage across the PN-junction in reverse biased condition enhances beyond this specific value, then the junction will get broken.
It can also be defined as when a diode resists the highest voltage in the condition of reverse-bias before gets damage. In the above figure, a PN junction is used as a rectifier and the main function of this is to convert AC to DC. So, during the negative half cycle, care must be taken because the highest value of AC voltage must be below the rated value of the PIV of the diode.
What is the Importance of Peak Inverse Voltage?
The term PIV stands for “Peak Inverse Voltage” and it is the utmost voltage that appears across the PN-junction diode once it is non-conducting. When the diode is connected in reverse biased then it doesn’t conduct which means PIV is the utmost voltage across the terminals of the diode once it is connected in a circuit in reverse biased.
Every diode has a specific PIV value based on the manufacturers. The voltage in reverse bias must beat this PIV otherwise the diode will damage. Usually, the highest-rated PIV of Si (Silicon) diode is more as compared to Ge (Germanium) diode. The max peak voltage that a diode can resist within the reverse nonconducting region is known as PIV. So, up to this max voltage, the diode can block the conduction of current within the opposite direction because the diode is a unidirectional device.
If the voltage of the diode is higher than PIV which is applied across the PN junction diode, then it travels throughout an avalanche breakdown. So, the potential barrier will damage & a high impulse current will supply throughout the opposite direction. This high current can damage the diode as well as the device. So the voltage should be higher PIV so that de devices can be protected.
For peak inverse voltage calculation, the following circuit can be considered. The calculation of PIV for the Si diode can be done in the reverse bias of the diode. In the following circuit, there are two diodes namely D1 & D2. Here the diode ‘D2’ is connected in reverse bias so the transformer’s secondary windings’ complete voltage will be dropped across it.
Here, the voltage drop across the D1 diode is assumed to be zero. The D1 diode is connected in forwarding bias whereas the D2 is connected in reverse bias. Thus, the PIV is the crest value of the reverse voltage where the diode is connected to the transformer’s secondary winding. In the circuit, let the points A & B are –Esm & +Esm for the GND terminal. The voltage drop across the D1 can be neglected.
Therefore, the crest value for the reverse voltage across the D2 diode is ‘2Esm’
The PIV of diode is 2Esm = π E at DC | Idc =0
Here, Esm is the maximum value of the AC voltage across the half of the secondary winding of the transformer.
If the voltage drop across the diode is assumed like 0.7V then the peak inverse voltage of the reverse-biased diode can be given as,
PIV = 2Esm – 0.7
The peak inverse voltage of the diode formula which is mentioned above is used because simply one diode can conduct at a time.
PIV in Half Wave Rectifier
To get a basic idea of peak inverse voltage, we have to focus on the voltage that appears across the terminals of the semiconductor diode once it is reverse biased. Here, the diode is replaced with an open switch which is shown below.
From the above circuit, we can observe that the voltage which appears across the terminal of the diode when it is connected in reverse bias, is equivalent to “VmSinωt” that is -Ve half cycle of the AC supply voltage. Here, this is in sinusoidal form.
When the crest value of the sinusoidal AC supply is ‘Vm’, the highest voltage across the diode is reversed bias can also equivalent to ‘Vm’. So, the PIV of the semiconductor diode in HWR (half-wave rectifier) is equivalent to the crest value of the voltage supply.
PIV in Bridge Rectifier
The circuit diagram of the full-wave bridge rectifier is shown below. In this circuit, the two diodes are shorted. Since throughout the +ve half cycle of the voltage supply, the two diodes which are opposite diagonally can conducts so they are shorted. We can observe that the voltage across reaming two diodes can be equivalent to voltage supply & they are reversed biased.
Thus, the voltage which is utmost reversed biased across every non-conducting diode can be equivalent to the crest value of voltage supply voltage. Therefore the PIV of the diode within the bridge rectifier can be equivalent to the crest value of the voltage supply.
Therefore, the PIV of the diode in rectifiers like a half-wave, bridge & center-tapped FWR is Vm, correspondingly where ‘Vm’ is the crest value of voltage supply.
Thus, this is all about an overview of peak inverse voltage or PIV for semiconductor diode, bridge rectifier, and half-wave rectifier. Here is a question for you, what is the rating of PIV for the rectifier circuit?