In order to unify the electrical components of cars and motorcycles, the latter also began to use 12 volts in the on-board network. This has many advantages, since many parts can be purchased simply by going to an auto supply store. But why else is there a niche for six-volt batteries, since they are not used practically anywhere.
Standard voltage is the voltage that is very commonly used in your electronic gadgets. This voltage is 1.5 Volts, 3 Volts, 5 Volts, 9 Volts, 12 Volts, 24 Volts, etc. For example, your antediluvian MP3 player contained one 1.5 Volt battery. The TV remote control already uses two 1.5 Volt batteries connected in series, which means 3 Volts. In the USB connector, the outermost contacts have a potential of 5 Volts. Probably everyone had a Dandy in their childhood? To power Dandy, it was necessary to supply it with a voltage of 9 volts. Well, 12 Volts are used in almost all cars. 24 Volt is already used mainly in industry. Also, for this, relatively speaking, standard series, various consumers of this voltage are “sharpened”: light bulbs, record players, amplifiers, etc...
But, alas, our world is not ideal. Sometimes you just really need to get a voltage that is not from the standard range. For example, 9.6 Volts. Well, neither this way nor that... Yes, the power supply helps us out here. But again, if you use a ready-made power supply, then you will have to carry it along with the electronic trinket. How to solve this issue? So, I will give you three options:
First option
Make a voltage regulator in the electronic trinket circuit according to this scheme (more details here):
Second option
Build a stable source of non-standard voltage using three-terminal voltage stabilizers. Schemes to the studio!
What do we see as a result? We see a voltage stabilizer and a zener diode connected to the middle terminal of the stabilizer. XX are the last two digits written on the stabilizer. There may be numbers 05, 09, 12, 15, 18, 24. There may already be even more than 24. I don’t know, I won’t lie. These last two digits tell us the voltage that the stabilizer will produce according to the classic connection scheme:
Here, the 7805 stabilizer gives us 5 Volts at the output according to this scheme. 7812 will produce 12 Volts, 7815 - 15 Volts. You can read more about stabilizers here.
U of the zener diode is the stabilization voltage on the zener diode. If we take a zener diode with a stabilization voltage of 3 Volts and a voltage regulator 7805, then the output will be 8 Volts. 8 Volts is already a non-standard voltage range ;-). It turns out that by choosing the right stabilizer and the right zener diode, you can easily get a very stable voltage from a non-standard range of voltages ;-).
Let's look at all this with an example. Since I simply measure the voltage at the terminals of the stabilizer, I do not use capacitors. If I were powering the load, then I would also use capacitors. Our guinea pig is the 7805 stabilizer. We supply 9 Volts from the bulldozer to the input of this stabilizer:
Therefore, the output will be 5 Volts, after all, the stabilizer is 7805.
Now we take a zener diode with U stabilization = 2.4 Volts and insert it according to this circuit, you can do it without conductors, after all, we’re just measuring the voltage.
Oops, 7.3 Volts! 5+2.4 Volts. Works! Since my zener diodes are not high-precision (precision), the voltage of the zener diode may differ slightly from the nameplate (voltage declared by the manufacturer). Well, I think it's no problem. 0.1 Volt will not make a difference for us. As I already said, in this way you can select any value out of the ordinary.
Third option
There is also another similar method, but here diodes are used. Maybe you know that the voltage drop across the forward junction of a silicon diode is 0.6-0.7 Volts, and that of a germanium diode is 0.3-0.4 Volts? It is this property of the diode that we will use ;-).
So, let's get the diagram into the studio!
We assemble this structure according to the diagram. The unstabilized input DC voltage also remained 9 Volts. Stabilizer 7805.
So what's the outcome?
Almost 5.7 Volts;-), which was what needed to be proven.
If two diodes are connected in series, then the voltage will drop across each of them, therefore, it will be summed up:
Each silicon diode drops 0.7 Volts, which means 0.7 + 0.7 = 1.4 Volts. Same with germanium. You can connect three or four diodes, then you need to sum the voltages on each. In practice, more than three diodes are not used.
Sources of non-standard constant voltage can be used in completely different circuits that consume a current of less than 1 Ampere. Keep in mind that if your load consumes a little more than half an Ampere, then the elements must meet these requirements. You will need to take a more powerful diode than the one in my photo.
www.ruselectronic.com
Most often, radio devices require a stable voltage to function, independent of changes in the mains supply and load current. To solve these problems, compensation and parametric stabilization devices are used.
Its operating principle is based on the properties of semiconductor devices. The current-voltage characteristic of a semiconductor - a zener diode is shown in the graph.
During turn-on, the zener diode's properties are similar to those of a simple silicon-based diode. If the zener diode is turned on in the opposite direction, the electric current will initially increase slowly, but when a certain voltage value is reached, breakdown occurs. This is a mode where a small voltage increase creates a large zener diode current. The breakdown voltage is called stabilization voltage. To avoid failure of the zener diode, the current flow is limited by resistance. When the zener diode current fluctuates from the lowest to the highest value, the voltage does not change.
The diagram shows a voltage divider, which consists of a ballast resistor and a zener diode. A load is connected in parallel to it. When the supply voltage changes, the resistor current also changes. The zener diode takes over the changes: the current changes, but the voltage remains constant. When you change the load resistor, the current will change, but the voltage will remain constant.
The device discussed earlier is very simple in design, but makes it possible to connect power to the device with a current that does not exceed the maximum current of the zener diode. As a result, voltage stabilizing devices are used, which are called compensation devices. They consist of two types: parallel and serial.
The device is named according to the method of connection to the adjustment element. Compensating stabilizers of the sequential type are usually used. His diagram:
The control element is a transistor connected in series with the load. The output voltage is equal to the difference between the values of the zener diode and the emitter, which is several fractions of a volt, therefore it is considered that the output voltage is equal to the stabilizing voltage.
The considered devices of both types have disadvantages: it is impossible to obtain the exact value of the output voltage and make adjustments during operation. If it is necessary to create the possibility of regulation, then a compensatory type stabilizer is manufactured according to the following scheme:
In this device, regulation is carried out by a transistor. The main voltage is supplied by a zener diode. If the output voltage increases, the base of the transistor becomes negative in contrast to the emitter, the transistor will open by a larger amount and the current will increase. As a result, the negative voltage at the collector will become lower, as well as at the transistor. The second transistor will close, its resistance will increase, and the terminal voltage will increase. This leads to a decrease in the output voltage and a return to its previous value.
When the output voltage decreases, similar processes occur. You can adjust the exact output voltage using a tuning resistor.
Such devices in the integrated version have increased characteristics of parameters and properties that differ from similar semiconductor devices. They also have increased reliability, small dimensions and weight, as well as low cost.
The adjustment element acts as a variable resistance connected in series with the load. When the voltage fluctuates, the resistance of the adjustment element changes so that compensation for such fluctuations occurs. The control element is influenced by feedback, which contains a control element, a main voltage source and a voltage meter. This meter is a potentiometer from which part of the output voltage comes.
The feedback adjusts the output voltage used for the load, the output voltage of the potentiometer becomes equal to the main voltage. Voltage fluctuations from the main one creates some voltage drop at the regulation. As a result, the output voltage can be adjusted within certain limits by the measuring element. If the stabilizer is planned to be manufactured for a certain voltage value, then the measuring element is created inside the microcircuit with temperature compensation. If there is a large output voltage range, the measuring element is performed behind the microcircuit.
If we compare the circuits of stabilizers, then a device of a sequential type has increased efficiency at partial load. A parallel type device consumes constant power from the source and supplies it to the control element and the load. Parallel stabilizers are recommended for use with constant loads at full load. The parallel stabilizer does not create a danger in the event of a short circuit, the sequential type does not create a danger during idle. At a constant load, both devices create high efficiency.
Innovative variants of sequential stabilizer circuits are made on a 3-pin microcircuit. Due to the fact that there are only three outputs, they are easier to use in practical applications, since they displace other types of stabilizers in the range of 0.1-3 amperes.
You may not use containers C1 and C2, but they allow you to optimize the properties of the stabilizer. Capacity C1 is used to create system stability, capacitance C2 is needed for the reason that a sudden increase in load cannot be tracked by the stabilizer. In this case, the current is supported by capacitance C2. In practice, 7900 series microcircuits from Motorola are often used, which stabilize a positive voltage value, and 7900 – a value with a minus sign.
The microcircuit looks like:
To increase reliability and create cooling, the stabilizer is mounted on a radiator.
In the 1st picture there is a circuit based on the 2SC1061 transistor.
The output of the device receives 12 volts; the output voltage depends directly on the voltage of the zener diode. The maximum permissible current is 1 ampere.
When using a 2N 3055 transistor, the maximum permissible output current can be increased to 2 amperes. In the 2nd figure there is a circuit of a stabilizer based on a 2N 3055 transistor; the output voltage, as in Figure 1, depends on the voltage of the zener diode.
In the 3rd picture - an adapter for a car - the battery voltage in the car is 12 V. To create a voltage of a lower value, the following circuit is used.
ostabilizatore.ru
I recently repeated one good charger circuit for a 6V battery. A large number of such batteries have appeared on sale, and if there are chargers for them, they are the simplest - a diode bridge, a resistor, a capacitor and an LED for indication. Since 12-volt automobile ones are mainly required. Of all the schemes that are on the Internet, I settled on this one. It works stably and is no worse than other industrial circuits. The output voltage is stable - 6.8V, current 0.45 A, the end of charging is visible on the LED - the red LED goes out when the battery is fully charged. I didn’t install a relay, there is no need for it, the starter works like a clock if the parts are in good working order. Charger for 6V batteries - diagram
To reduce the degree of heating in the charger, two 15 Ohm resistors with a power of 2 W are used, connected in parallel. Charging circuit board
This device uses imported oxide capacitors. Take relays with an operating voltage of 12 V. Diodes 1N4007 (VD1 - VD5) are interchangeable with any that can withstand a current at least twice the charging one. Instead of the KR142EN12A chip, you can use LM317. It must be placed on a heat sink, the area of which depends on the charging current.
The network transformer must provide an alternating voltage of 15-18 V on the secondary winding with a load current of 0.5 A. All parts, with the exception of the network transformer, microcircuit and LEDs, are mounted on a printed circuit board made of single-sided foil fiberglass with dimensions of 55x60 mm.
A properly assembled device requires minimal adjustment. With the battery disconnected, power is supplied and, by selecting resistor R6, the output voltage is set to 6.75 V. To check the operation of the current limiting unit, instead of the batteries, a 2 W resistor with a resistance of approximately 10 0 m is briefly connected and the current flowing through it is measured. It should not exceed 0.45 A. At this point, the setting can be considered completed.
I placed all the filling of the charger in a plastic case of suitable sizes, and placed LEDs, a power button, a fuse and 6-volt battery connection terminals on the front panel. Assembly and testing - Nikolay K. |
This is also useful to look at:
el-shema.ru
Initial data: a gearmotor with an operating voltage of 5 Volts at a current of 1 A and an ESP-8266 microcontroller with a change-sensitive operating supply voltage of 3.3 Volts and a peak current of up to 600 milliamps. All this must be taken into account and powered from one rechargeable 18650 lithium-ion battery with a voltage of 2.8 -4.2 Volts.
We assemble the circuit below: a lithium-ion 18650 battery with a voltage of 2K.8 -4.2 Volts without an internal charger circuit -> we attach a module on the TP4056 chip designed for charging lithium-ion batteries with the function of limiting battery discharge to 2.8 Volts and protection from a short circuit (do not forget that this module starts when the battery is on and a short-term power supply of 5 Volts is supplied to the input of the module from a USB charger, this allows you not to use the power switch, the discharge current in standby mode is not very large and if the entire device is not used for a long time, it switches itself off when the battery voltage drops below 2.8 Volts)
To the TP4056 module we connect a module on the MT3608 chip - a step-up DC-DC (direct to direct current) stabilizer and voltage converter from 2.8 -4.2 Volt battery to a stable 5 Volt 2 Ampere - power supply for the gearmotor.
In parallel to the output of the MT3608 module, we connect a step-down DC-DC stabilizer-converter on the MP1584 EN chip, designed to provide a stable power supply of 3.3 Volts 1 Ampere to the ESP8266 microprocessor.
Stable operation of the ESP8266 is highly dependent on the stability of the supply voltage. Before connecting DC-DC stabilizer-converter modules in series, do not forget to adjust the required voltage with variable resistances, place the capacitor in parallel with the terminals of the gear motor so that it does not create high-frequency interference with the operation of the ESP8266 microprocessor.
As we can see from the multimeter readings, when connecting the gear motor, the supply voltage of the ESP8266 microcontroller HAS NOT CHANGED!
Why do you need a VOLTAGE STABILIZER. How to use voltage stabilizers Introduction to zener diodes, calculation of a parametric stabilizer; use of integral stabilizers; design of a simple zener diode tester and more.
| Name | RT9013 |  Richtek technology |
| Description | Stabilizer-converter for load with a current consumption of 500mA, with a low voltage drop, low level of intrinsic noise, ultra-fast, with current output and short circuit protection, CMOS LDO. | |
| RT9013 PDF Technical datasheet (datasheet): | ||
*Description MP1584EN
**Can be purchased at Your Cee store
*Can be purchased at Your Cee store
| Name | MC34063A |  Wing Shing International Group |
| Description | DC-DC controlled converter | |
| MC34063A Data Sheet PDF (datasheet): | ||
| Name |  |
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| Description | 4A, 400kHz, input voltage 5~32V / output voltage 5~35V, DC/DC switched boost converter | |||
| XL6009 Data Sheet PDF (datasheet): | ||||
|
||||
http://dwiglo.ru/mp2307dn-PDF.html
Chinese stabilizers for homemade ones. Part 1.
Chinese stabilizers for homemade ones. Part 2.
Chinese stabilizers for homemade ones. Part 3.
mirrobo.ru
For some electrical circuits and circuits, a conventional power supply that does not have stabilization is quite sufficient. Current sources of this type usually consist of a step-down transformer, a diode bridge rectifier, and a filter capacitor. The output voltage of the power supply depends on the number of turns of the secondary winding on the step-down transformer. But as you know, the mains voltage of 220 volts is unstable. It can fluctuate within certain limits (200-235 volts). Consequently, the output voltage on the transformer will also “float” (instead of say 12 volts it will be 10-14, or so).
Electrical engineering that is not particularly sensitive to small changes in the DC supply voltage can make do with such a simple power supply. But more sensitive electronics no longer tolerate this; it can even fail as a result. So there is a need for an additional constant output voltage stabilization circuit. In this article I present an electrical circuit of a fairly simple DC voltage stabilizer, which has a zener diode and a transistor. It is the zener diode that acts as a reference element that determines and stabilizes the output voltage of the power supply.
Now let's move on to a direct analysis of the electrical circuit of a simple DC voltage stabilizer. So, for example, we have a step-down transformer with an AC output voltage of 12 volts. We apply this same 12 volts to the input of our circuit, namely to the diode bridge and filter capacitor. The diode rectifier VD1 makes constant (but intermittent) current from alternating current. Its diodes must be designed for the maximum current (with a small margin of about 25%) that the power supply can produce. Well, their voltage (reverse) should not be lower than the output voltage.
Filter capacitor C1 smooths out these voltage surges, making the DC voltage waveform smoother (though not ideal). Its capacity should be from 1000 µF to 10,000 µF. The voltage is also greater than the output. Please note that there is such an effect - the alternating voltage after the diode bridge and the electrolyte filter capacitor increases by about 18%. Therefore, in the end we will get at the output not 12 volts, but somewhere around 14.5.
Now comes the DC voltage stabilizer part. The main functional element here is the zener diode itself. Let me remind you that zener diodes have the ability, within certain limits, to stably maintain a certain constant voltage (stabilization voltage) when turned back on. When a voltage is applied to the zener diode from 0 to the stabilization voltage, it will simply increase (at the ends of the zener diode). Having reached the stabilization level, the voltage will remain unchanged (with a slight increase), and the strength of the current flowing through it will begin to increase.
In our circuit of a simple stabilizer, which should produce 12 volts at the output, the zener diode VD2 is designed for a voltage of 12.6 (let’s put the zener diode at 13 volts, this corresponds to D814D). Why 12.6 volts? Because 0.6 volts will be deposited at the emitter-base transistor junction. And the output will be exactly 12 volts. Well, since we set the zener diode to 13 volts, the output of the power supply will be somewhere around 12.4 V.
Zener diode VD2 (which creates the DC reference voltage) needs a current limiter that will protect it from excessive overheating. In the diagram, this role is played by resistor R1. As you can see, it is connected in series with the zener diode VD2. Another filter capacitor, electrolyte C2, is parallel to the zener diode. Its task is also to smooth out excess voltage ripples. You can do without it, but it will still be better with it!
Next in the diagram we see bipolar transistor VT1, which is connected according to a common collector circuit. Let me remind you that connection circuits for bipolar transistors of the common collector type (this is also called an emitter follower) are characterized by the fact that they significantly increase the current strength, but there is no voltage gain (even it is slightly less than the input voltage, exactly by the same 0.6 volts ). Therefore, at the output of the transistor we receive the constant voltage that is available at its input (namely, the voltage of the reference zener diode, equal to 13 volts). And since the emitter junction leaves 0.6 volts on itself, then the output of the transistor will no longer be 13, but 12.4 volts.
As you should know, in order for a transistor to start opening (passing controlled currents through itself along the collector-emitter circuit), it needs a resistor to create a bias. This task is performed by the same resistor R1. By changing its rating (within certain limits), you can change the current strength at the output of the transistor, and therefore at the output of our stabilized power supply. For those who want to experiment with this, I advise you to replace R1 with a tuning resistance with a nominal value of about 47 kilo-ohms. By adjusting it, see how the current strength at the output of the power supply changes.
Well, at the output of the simple DC voltage stabilizer circuit there is another small filter capacitor, electrolyte C3, which smoothes out ripples at the output of the stabilized power supply. Load resistor R2 is soldered in parallel to it. It closes the emitter of transistor VT1 to the minus of the circuit. As you can see, the scheme is quite simple. Contains a minimum of components. It provides a completely stable voltage at its output. To power many electrical equipment, this stabilized power supply will be quite enough. This transistor is designed for a maximum current of 8 amperes. Therefore, such a current requires a radiator that will remove excess heat from the transistor.
P.S. If we add a variable resistor with a nominal value of 10 kilo-ohms in parallel with the zener diode (we connect the middle terminal to the base of the transistor), then in the end we will get an adjustable power supply. On it you can smoothly change the output voltage from 0 to maximum (zener diode voltage minus the same 0.6 volts). I think such a scheme will already be in more demand.
electrohobby.ru
A 5-12 volt DC-DC boost converter is easiest to assemble using the LM2577, which provides 12V output using a 5V input signal and a maximum load current of 800 mA. M\C LM2577 is a boost forward pulse converter. It is available in three different output voltage versions: 12V, 15V and adjustable. Here is the detailed documentation.
The circuitry on it requires a minimum number of external components, and such regulators are cost-effective and easy to use. Other features include a built-in oscillator at a fixed frequency of 52 kHz that does not require any external components, a soft start mode to reduce inrush current, and a current control mode to improve input voltage tolerance and output variable load.
An adjustable microcircuit LM2577-adj is used here. To obtain other output voltages, you need to change the value of the feedback resistor R2 and R3. The output voltage is calculated using the formula:
V Out = 1.23V (1+R2/R3)
In general, LM2577 is inexpensive, the inductor in this circuit is unified - 100 μH and the maximum current is 1 A. Thanks to the pulsed operation, no large radiators are required for cooling - so this converter circuit can be safely recommended for repetition. It is especially useful in cases where you need to get 12 volts from the USB output.
Another version of a similar device, but based on the MC34063A chip - see this article.
elwo.ru
If we connect a diode and resistor in series with a constant voltage source such that the diode is forward biased (as shown in figure below (a)), the voltage drop across the diode will remain fairly constant over a wide range of power supply voltages.
According to Shockley's diode equation, the current through a forward-biased PN junction is proportional to e raised to the power of the forward voltage drop. Since this is an exponential function, the current rises quite quickly with a moderate increase in voltage drop. Another way to look at this is to say that the voltage dropped across a forward biased diode changes little with large changes in the current flowing through the diode. In the circuit shown in figure below (a), the current is limited by the voltage of the power supply, the series resistor and the voltage drop across the diode, which we know is not much different from 0.7 volts. If the power supply voltage is increased, the voltage drop across the resistor will increase by almost the same amount, but the voltage drop across the diode will increase very little. Conversely, decreasing the power supply voltage will result in an almost equal decrease in the voltage drop across the resistor and a small decrease in the voltage drop across the diode. In short, we could summarize this behavior by saying that the diode stabilizes the voltage drop at about 0.7 volts.
Voltage control is a very useful property of a diode. Let us assume that we have assembled some kind of circuit that does not allow changes in the voltage of the power supply, but which must be powered from a battery of galvanic cells, the voltage of which varies throughout its entire service life. We could build a circuit as shown in the figure and connect the circuit that requires a regulated voltage to the diode, where it will receive a constant 0.7 volts.
This will certainly work, but most practical circuits of any type require a supply voltage greater than 0.7 volts to operate properly. One way to increase the level of our stabilized voltage would be to connect several diodes in series, since the voltage drop across each individual diode of 0.7 volts will increase the final value by that amount. For example, if we had ten diodes in series, the regulated voltage would be ten times 0.7 volts, that is, 7 volts (Figure below (b)).
Forward bias of Si diodes: (a) single diode, 0.7V, (b) 10 diodes in series, 7.0V.
Until the voltage drops below 7 volts, the 10-diode "stack" will drop approximately 7 volts.
If larger regulated voltages are required, we can either use more diodes in series (not the most elegant way, in my opinion), or try a completely different approach. We know that the forward voltage of a diode is fairly constant over a wide range of conditions, as is the reverse breakdown voltage, which is typically much greater than the forward voltage. If we reverse the polarity of the diode in our single diode regulator circuit and increase the power supply voltage to the point where the diode "breakdown" occurs (the diode can no longer withstand the reverse bias voltage applied to it), the diode will stabilize the voltage in a similar manner at that breakdown point. not allowing it to increase further as shown in the picture below.
Breakdown of a reverse biased Si diode at a voltage of approximately 100 V.
Unfortunately, when regular rectifier diodes "flash", they are usually destroyed. However, it is possible to create a special type of diode that can handle breakdown without complete destruction. This type of diode is called a zener diode, and its symbol is shown in the figure below.
Conventional graphic designation of a zener diode
When forward biased, zener diodes behave the same as standard rectifier diodes: they have a forward voltage drop that follows the "diode equation" of approximately 0.7 volts. In reverse bias mode, they do not conduct current until the applied voltage reaches or exceeds the so-called regulation voltage, at which point the zener diode is capable of conducting significant current and will attempt to limit the voltage dropped across it to the regulation voltage . As long as the power dissipated by this reverse current does not exceed the thermal limits of the zener diode, the zener diode will not be damaged.
Zener diodes are manufactured with stabilization voltages ranging from several volts to hundreds of volts. This regulation voltage varies slightly with temperature and may be within 5 to 10 percent of the manufacturer's specifications. However, this stability and accuracy is usually sufficient for using a zener diode as a voltage regulator in the general power circuit shown in the figure below.
Voltage stabilizer circuit using a zener diode, stabilization voltage = 12.6 V
Please note the zener diode switching direction in the above diagram: the zener diode is reverse biased and this is intentional. If we turned on the zener diode in the "normal" way so that it was forward biased, then it would only drop 0.7 volts, like a regular rectifier diode. If we want to use the reverse breakdown properties of a zener diode, then we must use it in reverse bias mode. As long as the supply voltage remains above the regulation voltage (12.6 volts in this example), the voltage dropped across the zener diode will remain approximately 12.6 volts.
Like any semiconductor device, the zener diode is sensitive to temperature. Too much heat will destroy the zener diode, and since it both lowers voltage and conducts current, it produces heat according to Joule's law (P = IU). Therefore, care must be taken when designing the voltage regulator circuit to ensure that the zener diode's power dissipation rating is not exceeded. It is interesting to note that when zener diodes fail due to high power dissipation, they usually short out rather than open. A diode that fails for the same reason is easy to detect: the voltage drop across it is almost zero, like across a piece of wire.
Let's consider the voltage stabilizer circuit using a zener diode mathematically, determining all voltages, currents and power dissipation. Taking the same circuit as shown earlier, we will perform the calculations assuming that the zener diode voltage is 12.6 volts, the supply voltage is 45 volts, and the series resistor is 1000 ohms (we will assume that the zener diode voltage is exactly 12 .6 volts to avoid having to judge all values as "approximate" in figure (a) below).
If the zener diode voltage is 12.6 volts and the power supply voltage is 45 volts, the voltage drop across the resistor will be 32.4 volts (45 volts – 12.6 volts = 32.4 volts). 32.4 volts dropped into 1000 ohms produces a current of 32.4 mA in the circuit (Figure (b) below).
(a) Zener diode voltage regulator with 1000 ohm resistor. (b) Calculation of voltage and current drops.
Power is calculated by multiplying current by voltage (P=IU), so we can easily calculate the power dissipation for both the resistor and the zener diode:
For this circuit, a zener diode with a nominal power of 0.5 watts and a resistor with a power dissipation of 1.5 or 2 watts would be sufficient.
If excessive power dissipation is harmful, then why not design the circuit with the least amount of dissipation possible? Why not just install a very high resistance resistor, thereby greatly limiting the current and keeping the dissipation figures very low? Let's take the same circuit, for example, with a 100 kOhm resistor instead of a 1 kOhm resistor. Note that both the supply voltage and the zener voltage have not changed:
Voltage stabilizer on a zener diode with a 100 kOhm resistor
At 1/100 of the current we had previously (324 µA, instead of 32.4 mA), both power dissipation values should decrease by a factor of 100:
Seems perfect, doesn't it? Less power dissipation means lower operating temperature for both the zener diode and the resistor, as well as less energy wasted in the system, right? A higher resistance value reduces the power dissipation levels in the circuit, but unfortunately creates another problem. Remember that the purpose of a regulator circuit is to provide a stable voltage to another circuit. In other words, we're ultimately going to power something with 12.6 volts, and that something will have its own current draw. Let's look at our first regulator circuit, this time with a 500 ohm load connected in parallel with the zener diode, in the figure below.
Voltage stabilizer on a zener diode with a 1 kOhm resistor in series and a 500 Ohm load
If 12.6 volts are maintained into a 500 ohm load, the load will draw 25.2 mA of current. In order for the "pull down" resistor to reduce the voltage by 32.4 volts (reducing the voltage of the 45 volt power supply to 12.6 volts at the zener diode), it must still conduct 32.4 mA of current. This results in a current of 7.2 mA flowing through the zener diode.
Now let’s look at our “energy-saving” stabilizer circuit with a 100 kOhm step-down resistor, connecting the same 500 Ohm load to it. It is supposed to support 12.6 volts at the load, like the previous circuit. However, as we will see, it cannot complete this task (picture below).
Voltage unstabilizer on a zener diode with a 100 kOhm resistor in series and a 500 Ohm load
With a large pull-down resistor value, the voltage across a 500 ohm load will be about 224 mV, which is much less than the expected value of 12.6 volts! Why is that? If we actually had 12.6 volts across the load, then there would be a current of 25.2 mA, as before. This load current would have to pass through the series pull-down resistor as it did before, but with the new (much larger!) pull-down resistor, the voltage drop across that resistor with the 25.2 mA current flowing through it would be 2,520 volts! Since we obviously don't have that much voltage supplied from the battery, this can't happen.
The situation is easier to understand if we temporarily remove the zener diode from the circuit and analyze the behavior of just the two resistors in the figure below.
Unstabilizer with removed zener diode
Both the 100 kΩ pull-down resistor and the 500 Ω load resistor are in series, providing a total circuit resistance of 100.5 kΩ. With a total voltage of 45 V and a total resistance of 100.5 kOhm, Ohm's law (I=U/R) tells us that the current will be 447.76 µA. Calculating the voltage drop across both resistors (U=IR), we get 44.776 volts and 224 mV, respectively. If at this moment we returned the zener diode, it would also “see” 224 mV across it, being connected in parallel with the load resistance. This is much lower than the breakdown voltage of the zener diode, and therefore it will not be “blowed through” and will not conduct current. In this regard, at low voltage the zener diode will not work even if it is forward biased. At the very least, it must be receiving 12.6 volts to "activate" it.
The analytical technique of removing a zener diode from a circuit and observing the presence or absence of sufficient voltage for it to conduct is valid. Just because a zener diode is included in the circuit does not guarantee that the full voltage of the zener diode will always reach it! Remember that zener diodes work by limiting the voltage to some maximum level; they cannot compensate for the lack of voltage.
Thus, any zener diode stabilizer circuit will work as long as the load resistance is equal to or greater than a certain minimum value. If the load resistance is too low, it will draw too much current, which will result in too much voltage across the pull-down resistor, leaving insufficient voltage across the zener diode to make it conduct current. When a zener diode stops conducting current, it can no longer regulate voltage and the load voltage will be below its regulation point.
However, our regulator circuit with a 100 kOhm pull-down resistor must be suitable for some value of load resistance. To find this appropriate load resistance value, we can use a table to calculate the resistance in a circuit of two resistors in series (without a zener diode), entering the known values for the total voltage and the resistance of the pull-down resistor, and calculating for an expected load voltage of 12.6 volts:
With 45 volts total voltage and 12.6 volts across the load, we should get 32.4 volts across the pull down resistor Rlow:
At 32.4 volts across the pull-down resistor and its resistance is 100 kOhm, the current flowing through it will be 324 µA:
When connected in series, the current flowing through all components is the same:
So if the load resistance is exactly 38.889k ohms, it will be 12.6 volts with or without the zener diode. Any load resistance less than 38.889 kOhms will result in a load voltage of less than 12.6 volts with or without the zener diode. When using a zener diode, the load voltage will be stabilized to 12.6 volts for any load resistance greater than 38.889 kOhms.
With an initial value of 1 kOhm of the step-down resistor, our stabilizer circuit could adequately stabilize the voltage even with a load resistance of up to 500 Ohms. What we see is a trade-off between power dissipation and load resistance tolerance. A higher pull-down resistor gives us less power dissipation by increasing the minimum load resistance value. If we want to stabilize the voltage for low load resistance values, the circuit must be prepared to handle high power dissipation.
Zener diodes regulate voltage by acting as additional loads, drawing more or less current as needed to provide a constant voltage drop across the load. This is analogous to controlling a car's speed by braking rather than changing the throttle position: not only is it wasteful, but the brakes must be designed to handle all of the engine's power when driving conditions don't require it. Despite this fundamental inefficiency, zener diode voltage regulator circuits are widely used due to their simplicity. In high-power applications where inefficiency is unacceptable, other voltage control techniques are used. But even then, small zener circuits are often used to provide a "reference" voltage to drive more efficient circuitry that controls the main power.
Zener diodes are manufactured for the standard voltage ratings listed in the table below. The table "Basic Zener Voltages" lists the basic voltages for 0.5 and 1.3 W components. Watts correspond to the amount of power a component can dissipate without being damaged.
| 0.5 W | ||||||
| 2.4 V | 3.0 V | 3.3 V | 3.6 V | 3.9 V | 4.3 V | 4.7 V |
| 5.1 V | 5.6 V | 6.2 V | 6.8 V | 7.5 V | 8.2 V | 9.1 V |
| 10 V | 11 V | 12 V | 13 V | 15 V | 16 V | 18 V |
| 20 V | 24 V | 27 V | 30 V | |||
| 1.3 W | ||||||
| 4.7 V | 5.1 V | 5.6 V | 6.2 V | 6.8 V | 7.5 V | 8.2 V |
| 9.1 V | 10 V | 11 V | 12 V | 13 V | 15 V | 16 V |
| 18 V | 20 V | 22 V | 24 V | 27 V | 30 V | 33 V |
| 36 V | 39 V | 43 V | 47 V | 51 V | 56 V | 62 V |
| 68 V | 75 V | 100 V | 200 V |
Zener Voltage Limiter: A limiter circuit that cuts off signal peaks at approximately the zener voltage level. The circuit shown in the figure below has two zener diodes connected in series but directed oppositely to each other to symmetrically clamp the signal at approximately the regulation voltage level. The resistor limits the current consumed by the zener diodes to a safe value.
Zener voltage limiter*SPICE 03445.eps D1 4 0 diode D2 4 2 diode R1 2 1 1.0k V1 1 0 SIN(0 20 1k) .model diode d bv=10 .tran 0.001m 2m .end
The zener diode breakdown voltage is set to 10V using the bv=10 diode model parameter in the spice netlist above. This causes the zener diodes to limit the voltage at about 10 V. Back-to-back zener diodes limit both peaks. For the positive half cycle, the upper zener diode is reverse biased, breaking through the zener diode at 10 V. The lower zener diode drops approximately 0.7 V since it is forward biased. Thus, a more accurate cutoff level is 10 + 0.7 = 10.7 V. Similarly, the negative half-cycle cutoff occurs at –10.7 V. The figure below shows the cutoff level slightly greater than ±10 V.
Diagram of operation of a zener diode voltage limiter: input signal v(1) is limited to signal v(2)
Original article.
So, what’s in it? Based on the name, the circuit doesn’t seem to line up very well... Well, in the general case, the feedback - the divider of the output voltage monitor (comparator) - is turned...From the end:
...Or not? It might work, it might not, it depends on the power reserve. What's the key?
What should I do? Change the key to a more powerful one or sculpt a second key in parallel; if IT is a throttle one, change it to a more powerful discharge diode of the drive.
Wherein: The conversion frequency will increase, and perhaps for some nodes it will be prohibitive. Then it’s time to recalculate the storage choke (although there is a reserve of 20% of the total, since it’s not easy on the pocket), well, perhaps with thicker wiring. IMHO, a device for determining the limits of the regime, aka “finger”, is always with you...
What's the point in speculating if no one has seen the diagram yet? Perhaps it is a blocking generator, or an inverter-bridge?
(meant a diagram with a description, although it is possible without) (meant the composition of the transistors/diodes used)
Well, not out of curiosity...
ADDED 12/14/2008 5:04 PM
PS: Here is the diagram from the first link on request in Google pulse stabilizer circuit:
In the general case, I was talking about this kind of scheme. With options: the comparator can be integral, the switch is on a MOSFET, a choke with a gap (by the way, this ring without a gap confuses me... It can easily get enough, anyway). Here: change VD2 to a lower voltage one (3.6 V IMHO will work ), setting the exact Uout using R6... However, the output current is 1 A in no way, so: or putting 6 pieces of KD336 in parallel - it doesn’t make sense, they are ancient ones, there is no performance at all, and as the frequency increases, the voltaic speed rises. Changing the key transistor - MOSFET amperes by 5-10 amps! The conversion frequency for the used parts here is already almost limiting - this means increasing the inductance L1 (and the cross-section of the wire, which means recalculating it on a different magnetic circuit altogether). Well, accordingly, VD1 KY197 - in such modes it’s just a joke... And its performance is not so great... It’s ancient. A modern fast-diode with 10-15 amperes will whine here...
Well, that's about it. Although, this is a diagram from the FIRST link, and there are “...about 23,400 of them.” And if you also ask key stabilizer circuit, then oh-oh-oh!
