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DC Circuit Analysis and Basic Electronic Devices
Published in S. Bobby Rauf, Electrical Engineering for Non-Electrical Engineers, 2021
A Zener diode allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage is above the breakdown voltage. The breakdown voltage is also referred to as the “zener knee voltage,” “zener voltage” or “avalanche point.” Because of this basic characteristic of a Zener diode, it is commonly used to provide a reference voltage for voltage regulators, or to protect other semiconductor devices from momentary voltage pulses or excessive voltage “spikes.” The current response of a Zener diode is shown in Figure 2.5.
Direct Current Power Systems
Published in Stephen W. Fardo, Dale R. Patrick, Electrical Power Systems Technology, 2020
Stephen W. Fardo, Dale R. Patrick
Zener diodes are similar to conventional diodes when they are forward biased. When they are reverse biased, no conduction takes place until a specific value of reverse breakdown voltage (or “zener” voltage) is reached. The zener is designed so that it will operate in the reverse breakdown region of its characteristic curve (see Figure 7-31B). The reverse breakdown voltage is predetermined by the manufacturer. When used as a voltage regulator, the zener diode is reverse biased so that it will operate in the breakdown region. In this region, changes in current through the diode have little effect on the voltage across it. The constant-voltage characteristic of a zener diode makes it desirable for use as a regulating device.
DC Circuit Analysis, Diodes, and Transistors – BJT, MOSFET, and IGBT
Published in S. Bobby Rauf, Electrical Engineering Fundamentals, 2020
A Zener diode allows current to flow in the forward direction in the same manner as an ideal diode but will also permit it to flow in the reverse direction when the voltage is above the breakdown voltage. The breakdown voltage is also referred to as the “Zener knee voltage,” “Zener voltage,” or “avalanche point”. Because of this basic characteristic of a Zener diode, it is commonly used to provide a reference voltage for voltage regulators or to protect other semiconductor devices from momentary voltage pulses or excessive voltage “spikes.” The current response of a Zener diode is shown in Figure 2.7.
Light controlled (super) cascode, LC(S)C, a power device with optical turn-on and -off
Published in EPE Journal, 2020
The leakage currents through T1 and T2 in blocking conditions as well as currents due to their stray capacities during switching must not cause an avalanche of T0 [12]. So a 15 V zener diode DZ0 in parallel to T0 was applied for protection. The blocking voltage across T0 was about 6,5 V (see Figure 11) and therefore lower than the zener voltage of DZ0. However, a small current flows through DZ0 at this voltage. An additional bipolar or Schottky Si-diode in parallel to DZ0 would reduce in reverse conduction mode the Drain-Source-voltage. Also, this would avoid overcurrent in the mentioned zener diode because in reverse conduction of the cascode this zener diode will be in forward operation. However, a zener diode with temperature stabilization by a series diode [13] could not be stressed by a reverse current through T0.
Supercapacitor Module Solely Powering DC–DC Buck Converter for Hand-Held Applications
Published in IETE Journal of Research, 2020
Aditya S. Sengupta, Ajoy K. Chakraborty, Bidyut K. Bhattacharyya
‘Z2’ denotes the Zener diode and R1, R2, R3, R4 are resistances. ‘Ro’ is the output load resistance while ‘Vo’ and ‘Io’ are the output voltage and current respectively. The output of the relaxation oscillator formed using ‘A1’ is bipolar in nature which is fed to the voltage doubler circuit (portion of circuit bordered by solid black lines). The output of this voltage doubler circuit is a dc voltage which has an average value nearly equal to ‘2Vi’ and this voltage is used as the input for the buck converter. Also reference voltage for the PWM should be nearly equal to ‘Vo/2’ which is generated from ‘2Vi’ using a voltage regulator circuit that is composed of op-amp ‘A3’, ‘Z2’, ‘S3’ and resistances ‘R3’ and ‘R4’. In the circuit shown in Figure 3, since the input to the closed loop feed-forward buck converter is doubled, the reference voltage needed for PWM generation should be halved accordingly at the same proportion in order to achieve the desired duty ratio for generating a constant output voltage irrespective of the decay or fluctuations in input voltage. One more advantage of halving the reference voltage in the PWM control circuit instead of input voltage is to reduce power consumption.
Optimization of a microcontroller for the simultaneous logging of temperature and reversed-flow inverse gas chromatography measurements
Published in Instrumentation Science & Technology, 2018
Kosmas Martakidis, Dimitrios Gavril
There are two main ways to improve the microcontroller’s ADC resolution. One is to switch to a lower reference voltage (up to 2.40 V) using an external Zener diode circuit or a dedicated voltage reference-integrated circuit (integrated circuit) for more precision. If there is need to improve the resolution even more, the second way (and the one chosen for this study, c.f. Figure 2) is to amplify the output signal of the detector using a precision operational amplifier (op-amp). The op-amp’s gain applied to the voltage on its noninverting input is programmable by tweaking the values of the external voltage divider circuit’s low-tolerance resistors between the op-amp’s output and inverting input.