Select a non-polar capacitor for 400-600 volts, the output current strength depends on its capacity. Resistor with resistance from 75 to 150 kilo-ohms. After the diode bridge, the voltage is about 100 volts, it needs to be reduced. For these purposes, a domestic Zener diode series D814D was used.
After the zener diode, we already get a voltage of 9 volts, you can also use literally any zener diodes of 6-15 volts. At the output, a typical 5-volt microcircuit stabilizer was used, the entire main load lies on it, so the stabilizer should be screwed onto a small heat sink, preferably spreading thermal grease in advance.
Polar capacitors are designed to suppress and filter network interference. The device works very stably, but has only one drawback - a small output current. The current can be increased by selecting a capacitor and a resistor in the quenching circuit. Printed - in the archive.
The device is now actively used for low-power structures. The output current is large enough to charge a mobile phone, power LEDs and small incandescent lamps. Video with experiments and measurements is given below:
However, note that due to the absence of a network transformer, there is a risk of phase shock, therefore all current-carrying elements of the power supply unit and the device that is connected to it must be carefully isolated! The author of the article is AKA (Arthur).
Discuss the article TRANSFORMER-FREE PSU ON 5V
Zener diode
A zener diode is also a diode, but is designed to maintain a constant voltage in the power supply circuits of electronic equipment. Silicon zener diodes of wide application are similar in design and principle of operation to planar rectifier diodes. Its peculiarity is that in the forward direction it works like a regular diode, but in the reverse it breaks down at some voltage, for example, 3.3 volts. Similar to a steam boiler restriction valve that opens when pressure rises and relieves excess steam. Zener diodes are used when they want to get a voltage of a given value, regardless of the input voltage. This may be, for example, a reference value with respect to which the input signal is compared. They can cut the input signal to the desired value or use it as a protection. In my circuits, I often put a Zener diode at a voltage of 5.5 volts on the controller's power supply, so that if something happens, if the voltage jumps sharply, this Zener diode will drain the excess through itself.
Voltage is applied to the zener diode in reverse polarity, that is, a minus “-” will be applied to the zener diode anode. With such a Zener diode, a reverse current flows through it ( I arr) from the rectifier. The voltage from the output of the rectifier can vary, the reverse current will also change, and the voltage at the zener diode and at the load will remain unchanged, that is, stable. The following figure shows the current-voltage characteristic of the zener diode.
The zener diode operates on the reverse branch of the I – V characteristic (current – \u200b\u200bvoltage characteristic), as shown in the figure. The main parameters of the zener diode include U st. (stabilization voltage) and I st. (stabilization current). These data are indicated in the passport for a specific type of zener diode. Moreover, the values \u200b\u200bof the maximum and minimum currents are taken into account only when calculating stabilizers with predicted large changes in voltage.
Zener diodes
Many, many years ago, such a word as a zener diode did not exist at all. Especially in household equipment. Let's try to imagine a bulky tube receiver in the mid-twentieth century. Many sacrificed them to their own curiosity, when dad and mom bought something new, and “Record” or “Neman” were torn to pieces.
The power supply unit for the lamp receiver was extremely simple: a powerful cube of a power transformer, which usually had only two secondary windings, a diode bridge or a selenium rectifier, two electrolytic capacitors and a two-watt resistor between them.
The first winding fed the glow of all the receiver lamps with alternating current and voltage 6.3V (volts), and about 240V came to the primitive rectifier to power the anodes of the lamps. There was no talk of any voltage stabilization. Based on the fact that the reception of radio stations was conducted on long, medium and short waves with a very narrow band and terrible quality, the presence or absence of stabilization of the supply voltage did not affect this quality at all, and there could simply not be a decent frequency auto-tuning on that element base.
At that time, stabilizers were used only in military receivers and transmitters, of course also tube ones. For instance: SG1P - gas discharge stabilizer, finger-type. This continued until transistors appeared. And then it turned out that the circuits made on transistors are very sensitive to fluctuations in the supply voltage, and an ordinary simple rectifier can no longer be dispensed with. Using the physical principle embodied in gas-discharge devices, a semiconductor zener diode, less commonly called a Zener diode, was created.
Graphic image of a zener diode on concepts.
The principle of the zener diode.
First of all, we should not forget that the zener diode works only in DC circuits. Voltage is applied to the zener diode in reverse polarity, that is, a minus “-” will be applied to the zener diode anode. With such a Zener diode, a reverse current flows through it ( I arr) from the rectifier. The voltage from the output of the rectifier can vary, the reverse current will also change, and the voltage at the zener diode and at the load will remain unchanged, that is, stable. The following figure shows the current-voltage characteristic of the zener diode.
The zener diode operates on the reverse branch of the I – V characteristic (current – \u200b\u200bvoltage characteristic), as shown in the figure. The main parameters of the zener diode include U st. (stabilization voltage) and I st. (stabilization current). These data are indicated in the passport for a specific type of zener diode. Moreover, the values \u200b\u200bof the maximum and minimum currents are taken into account only when calculating stabilizers with predicted large changes in voltage.
The main parameters of the zener diodes.
In order to choose the right zener diode, it is necessary to understand the markings of semiconductor devices. Previously, all types of diodes, including zener diodes, were denoted by the letter “D” and a number that determines what kind of device it is. Here is an example of the very popular Zener diode D814 (A, B, C, D). The letter indicated stabilization voltage.
Near the passport data of a modern zener diode ( 2C147A ), which was used in stabilizers to power circuits on the popular series of K155 and K133 chips made by TTL technology and having a supply voltage of 5V.
To understand the markings and the main parameters of modern domestic semiconductor devices, you need to know a little legend. They look as follows: the number 1 or the letter G is germanium, the number 2 or the letter K is silicon, the number 3 or the letter A is gallium arsenide. This is the first sign. D - diode, T - transistor, C - zener diode, L - LED. This is the second sign. The third sign is a group of numbers indicating the scope of the device. Hence: GT 313 (1T 313) - a high-frequency germanium transistor, 2C147 - a silicon zener diode with a nominal stabilization voltage of 4.7 volts, AL307 - a gallium arsenide LED.
Here is a diagram of a simple but reliable voltage regulator.
Between the collector of a powerful transistor and the case, voltage is supplied from the rectifier and equal to 12 - 15 volts. We remove the 9V stabilized voltage from the emitter of the transistor, since as a Zener diode VD1 we use a reliable element D814B (see table). Resistor R1 - 1kOhm, transistor KT819 providing current up to 10 amperes.
The transistor must be placed on the heat sink. The only drawback of this circuit is the inability to adjust the output voltage. In more complex circuits, a tuning resistor is of course available. In all laboratory and home amateur radio power sources, it is possible to adjust the output voltage from 0 to 20 - 25 volts.
Integrated Stabilizers.
The development of integrated microelectronics and the emergence of multifunctional circuits of medium and high degree of integration, of course, touched upon the problems associated with voltage stabilization. The domestic industry tensed up and launched the K142 series on the market of radio-electronic components, which was made up of integrated voltage stabilizers. The full name of the product was KR142EN5A, but since the case was small and the name was not removed entirely, they began to write KREN5A or B, and in the conversation they were called simply “crinkles”.
The series itself was quite large. The output voltage varied depending on the letter. For example, KREN3 produced 3 to 30 volts of stabilized voltage with the ability to adjust, and KREN15 was a fifteen-volt bipolar power source.
Connecting K142 Series Integrated Stabilizers was extremely simple. Two smoothing capacitors and the stabilizer itself. Take a look at the diagram.
If there is a need to obtain another stabilized voltage, then proceed as follows: suppose we use a KREN5A microcircuit for 5V, and we need a different voltage. Then a zener diode is placed between the second terminal and the case in such a way that adding the stabilization voltage of the microcircuit, and the zener diode, we would get the desired voltage. If we add the KS191 zener diode to V \u003d 9.1 + 5V microcircuits, then at the output we get 14.1 volts.