Capacitor-zener diode rectifier

Encyclopedia of radio electronics and electrical engineering / Voltage converters, rectifiers, inverters

 Comments on the article

Transformerless low-power network power supplies with a quenching capacitor are widely used primarily due to the simplicity of their design, despite a serious drawback (the presence of a galvanic connection between the power supply output and the network).

The article proposes to improve the traditional bridge rectifier of such a block by replacing two diodes with zener diodes. This allows you to reduce the number of semiconductor devices, as well as use zener diodes not only to stabilize the voltage, but also to rectify it.

Low power network power supplies with a quenching capacitor are used in modern electronic radio equipment. The KVS power supply unit surpasses the traditional transformer and pulse units with a transformerless input in terms of simplicity of design and the used element base, as well as in terms of maintainability. And yet, no matter how simple the KVS power supply, its design needs to be improved without reducing the existing advantages. On the contrary, you can additionally obtain a number of useful operational properties.

The input part of the power supply contains a ballast capacitor C1 and a bridge rectifier made of diodes VD1, VD2 and zener diodes VD3, VD4 (Fig. 2a). The oscillogram of the output voltage of a diode-zener diode rectifier is shown in Fig. 2b (when the output voltage exceeds the stabilization voltage of the zener diode; otherwise, it works like a normal diode). From the beginning of the positive half-cycle of the current through the capacitor C1 until the moment t₁ Zener diode VD3 and diode VD2 are open, and Zener diode VD4 and diode VD1 are closed. In the time interval t₁...t₃ Zener diode VD3 and diode VD2 remain open, and a stabilization current pulse passes through the opened Zener diode VD4. The voltage at the zener diode VD4 is equal to its stabilization voltage U_Art.

The stabilization pulse current, which is through for a diode-zener diode rectifier, bypasses the load that is connected to the output of the bridge. At time t₂ the stabilization current reaches its maximum, and at the moment t₃ equals zero. Until the end of the positive half-cycle, the zener diode VD3 and the diode VD2 remain open. At time t₄ the positive half-cycle ends and the negative half-cycle begins, from the beginning of which until the moment t₅ already the zener diode VD4 and the diode VD1 are open, and the zener diode VD3 and the diode VD2 are closed. In the time interval t₅...t₇ Zener diode VD4 and diode VD1 continue to remain open, and through the Zener diode VD3 at voltage U_Art passes through the stabilization current pulse, maximum at the moment t₆. Starting from t₇ before the completion of the negative half-cycle, the zener diode VD4 and the diode VD1 remain open.

On this, the cycle of operation of the diode-zener diode rectifier is completed and the considered process is repeated during the next electrical period in the network.

Thus, a rectified current passes through the zener diodes VD3, VD4 from the anode to the cathode, and in the opposite direction - a pulsed stabilization current. In time intervals t₁...t₃ and t₅...t₇ the instantaneous value of the stabilization voltage changes by no more than a few percent. The value of the alternating current at the input of the bridge VD1-VD4 in the first approximation is equal to the ratio of the mains voltage to the capacitance of the ballast capacitor C1.

The operation of a diode-zener diode rectifier without a ballast element (Capacitor), which limits the value of the through current, is impossible. In functional terms, they are inseparable and form a single whole - a capacitor-zener diode rectifier (KSTV).

To limit the inrush current through the diodes and zener diodes of the bridge at the time of connection to the network, a current-limiting resistor with a resistance of several tens of ohms should be connected in series with the ballast capacitor, and to discharge the capacitor after disconnecting from the network, in parallel, a resistor with a resistance of hundreds of kΩ.

Scatter of U values_Art of the same type of zener diodes is approximately 10%, which leads to an additional ripple of the output voltage with the frequency of the supply network. The amplitude of the ripple voltage is proportional to the difference in the values ​​of U_Art zener diodes VD3, VD4.

For the purpose of experimental verification, a batch of eight D814B zener diodes was randomly selected, the stabilization voltage of which is given in Table 1.

Table 1

The results of the experiment are given in table. 2, testify to the advantage of KSTV over CVs in terms of the level of output voltage ripples at comparable values ​​of the load current.

Table 2

The reason for this lies in the fact that in the KSTV filter capacitor charged to the voltage value U_Art, discharges in the time interval t₃...t₅ only through the load. In the FAC, the capacitor during this period is discharged through a load connected in parallel and a zener diode having a low differential resistance. A decrease in the amplitude of the ripple voltage at the output of the KSTV with a decrease in the load current has a positive effect on the quality of the powered equipment. For example, the background level of the supply voltage at the output of sound reproducing equipment decreases during sound pauses.

Influence of inequality of U values_Art Zener diodes VD3, VD4 on the amplitude of the output voltage ripple are illustrated by the values ​​in brackets from Table 2, which are obtained by replacing Zener diode No. 7 (VD3) with No. 1 (see Table 1). Since the stabilization voltage values ​​\u0.6b\u7bof zener diode specimens differ by XNUMX V (about XNUMX% of U_Art), the amplitude of the output voltage ripple increased, but remained less than that of the CVS at low load currents. At the maximum current in the ripple voltage, along with a frequency of 100 Hz, a component of 50 Hz appeared. As the load current decreases, the ripple amplitude also decreases, the proportion of the component with a frequency of 50 Hz increases, and the frequency of 100 Hz decreases. Under load no more than 10% of the nominal component of 100 Hz is absent, the voltage ripple frequency is -50 Hz.

According to the values ​​from Table 2, the internal resistance of the power supplies was calculated: KVS - 7 Ohm, KSTV (C1= 0.5 µF) - 10 Ohm, KSTV (C1=1 µF) - 5 Ohm. Approximately the same values ​​of internal resistance are typical for a battery composed of six fresh galvanic cells 316 or partially discharged galvanic cells of a larger capacity.

When using powerful zener diodes (D815A ... D817GP) that have a mounting stud on the case, they can be installed on a common radiator if the letter P is present in their type designation. Otherwise, diodes and zener diodes must be swapped.

The galvanic connection of the network with the output of the power supply, and hence with the powered equipment, creates a real danger of electric shock. This should be remembered when designing and setting up blocks with a capacitor-zener diode rectifier. Prevention of electrical injury is possible through the use of double insulation, as well as a high-speed automatic protective shutdown device [4,5].

Literature

1. Sergeev B. Study of the possibility of using capacitor IWEP. - Electrosvyaz, 1994, No. 6, pp. 25-27.
2. Sergeev B. Limiting possibilities of using capacitor sources of secondary power supply. - Electrosvyaz, 1996, No. 2, pp. 38-40.
3. Biryukov S. Calculation of a network power supply with a quenching capacitor. - Radio, 1997, No. 5, pp. 48-50.
4. Vodyanitsky Yu. Protects the machine. - Model designer, 1994, No. 10, p.14,15.

Author: Kuznetsov A.; Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Voltage converters, rectifiers, inverters.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

The existence of an entropy rule for quantum entanglement has been proven 09.05.2024

Quantum mechanics continues to amaze us with its mysterious phenomena and unexpected discoveries. Recently, Bartosz Regula from the RIKEN Center for Quantum Computing and Ludovico Lamy from the University of Amsterdam presented a new discovery that concerns quantum entanglement and its relation to entropy. Quantum entanglement plays an important role in modern quantum information science and technology. However, the complexity of its structure makes understanding and managing it challenging. Regulus and Lamy's discovery shows that quantum entanglement follows an entropy rule similar to that for classical systems. This discovery opens new perspectives in the field of quantum information science and technology, deepening our understanding of quantum entanglement and its connection to thermodynamics. The results of the study indicate the possibility of reversibility of entanglement transformations, which could greatly simplify their use in various quantum technologies. Opening a new rule ... >>

Mini air conditioner Sony Reon Pocket 5 09.05.2024

Summer is a time for relaxation and travel, but often the heat can turn this time into an unbearable torment. Meet a new product from Sony - the Reon Pocket 5 mini-air conditioner, which promises to make summer more comfortable for its users. Sony has introduced a unique device - the Reon Pocket 5 mini-conditioner, which provides body cooling on hot days. With it, users can enjoy coolness anytime, anywhere by simply wearing it around their neck. This mini air conditioner is equipped with automatic adjustment of operating modes, as well as temperature and humidity sensors. Thanks to innovative technologies, Reon Pocket 5 adjusts its operation depending on the user's activity and environmental conditions. Users can easily adjust the temperature using a dedicated mobile app connected via Bluetooth. Additionally, specially designed T-shirts and shorts are available for convenience, to which a mini air conditioner can be attached. The device can oh ... >>

Energy from space for Starship 08.05.2024

Producing solar energy in space is becoming more feasible with the advent of new technologies and the development of space programs. The head of the startup Virtus Solis shared his vision of using SpaceX's Starship to create orbital power plants capable of powering the Earth. Startup Virtus Solis has unveiled an ambitious project to create orbital power plants using SpaceX's Starship. This idea could significantly change the field of solar energy production, making it more accessible and cheaper. The core of the startup's plan is to reduce the cost of launching satellites into space using Starship. This technological breakthrough is expected to make solar energy production in space more competitive with traditional energy sources. Virtual Solis plans to build large photovoltaic panels in orbit, using Starship to deliver the necessary equipment. However, one of the key challenges ... >>

Random news from the Archive New Model Spectrum Analyzer 17.04.2005 B&K PRECISION introduced the Model 2658 spectrum analyzer, which has a frequency range up to 8,5 GHz and fits in the hand. The features of the device include: power measurement in the main and side channels, measurement of electric and magnetic fields, measurement by markers, search for maxima, auto-tuning, printout of screen data, etc.

Other interesting news:

▪ Boots with spring studs

▪ Virus-eating bacteria discovered

▪ First 4K display for smartphones

▪ Rope battery winch

▪ The inhabitants of Pompeii sorted garbage for reuse

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Low frequency amplifiers. Article selection

▪ article Fate plays a man. Popular expression

▪ article Does a giraffe have a voice? Detailed answer

▪ article Performing work in the display class. Standard instruction on labor protection

▪ article Silent antenna tuning. Encyclopedia of radio electronics and electrical engineering

▪ article Cable lines up to 220 kV. General requirements. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024