Impulse current limiter for incandescent autolamps. Inrush current limiter when an incandescent lamp is turned on. Circuit with manual adjustment
Current limiter - a device designed to prevent a possible increase in current in the circuit above a predetermined value. The simplest limiter is an ordinary fuse. Structurally, the fuse is a fusible link enclosed in an insulator - a housing. If, for one reason or another, the current consumed by the load increases in the circuit, the fusible link burns out, and the load is no longer powered.
Types of limiters
With all the advantages of using a fuse, it has one serious drawback - low performance which makes it impossible to use in some cases. The disadvantages include the disposability of the fuse - if it blows, you will have to look for and install a fuse exactly the same as the blown one.
Electronic limiters
Much more advanced than the fuses mentioned above are electronic limiters. Conventionally, such devices can be divided into two types:
- recovering automatically after the elimination of the malfunction;
- manually restored. For example: in the circuit of the limiter there is a button, pressing which leads to its restart.
Separately, it is worth mentioning the so-called passive protection devices. Such devices are designed for light and / or sound signaling of situations when the permissible current in the load is exceeded. Most of these schemes alarms are used in conjunction with electronic limiters.
The simplest field effect transistor circuit
The simplest solution when it is necessary to limit the direct current in the load is to use a FET circuit. The schematic diagram of this device is shown in Fig. 1:
Rice. 1 - FET circuit
The load current when using the circuit shown in Fig. 1 cannot be greater than the initial drain current of the applied transistor. Therefore, the limiting range directly depends on the type of transistor. For example, when using the domestic transistor KP302, the limitation will be 30-50 mA.
The main disadvantage of the scheme described above is the difficulty of changing the limit limits. In more advanced devices, to eliminate this drawback, an additional element is used that performs the functions of a sensor. As a rule, such a sensor is a powerful resistor that is connected in series with the load. At the moment when the voltage drop across the resistor reaches a certain value, the current will automatically be limited. A diagram of such a device is shown in Figure 2.
Rice. 2 - Scheme on bipolar transistors
As you can see, the circuit is based on two bipolar transistors of the structure n - p - n. A resistor R 3 with a resistance of 3.6 ohms is used as a sensor.
The principle of operation of the device is as follows: the voltage from the source is supplied to the resistor R 1, and through it to the base of the transistor VT 1. The transistor opens, and most of the voltage from the source is supplied to the output of the device. In this case, the transistor VT 2 is in the closed state. At the moment when the voltage drop on the sensor (resistor R 3) reaches the opening threshold of the transistor VT 2, it will open, and the transistor VT 1, on the contrary, will start to close, thereby limiting the current at the output of the device. LED HL 1 is an indicator of the limiter operation.
The response threshold depends on the resistance of the resistor R 3 and the opening voltage of the transistor VT 2. For the described circuit, the limit threshold is: 0.7 V / 3.6 Ohm = 0.19 A.
Circuit with manual adjustment
In some cases, a device is required with the ability to manually change the current limit value in the load, for example, when it comes to the need to charge car batteries. The scheme of the adjustable device is shown in Figure 3.
Rice. 3 - Scheme with current limit adjustment
Device Specifications:
- input voltage - up to 40 V;
- output voltage - up to 32 V;
- current limiting range - 0.01 ... 3 A.
The main feature of the circuit is the ability to both change the magnitude of the current limit in the load, and the ability to adjust the output voltage. The current limit is set by a variable resistor R 5, and the output voltage is set by a variable resistor R 6. The current limit range is determined by the resistance of the current sensor - resistor R2.
When designing such a device, it is worth remembering that quite a lot of power is allocated to VT 4, therefore, in order to eliminate the possibility of overheating of the element and failure, it must be installed on a radiator. Also note that the variable resistors R 5 and R 6 must have a linear adjustment dependence for more convenient use of the device. Possible analogues of used parts:
- Transistors KT815 - VD139;
- Transistor KT814 - VD140;
- Transistor KT803 - 2N5067.
Instead of a conclusion
It cannot be argued that one or another method of limiting the current is better or worse. Each has its own advantages and disadvantages. Moreover, the use of each is advisable or completely unacceptable in a particular case. For example, the use of a fuse in the output circuit of a switching power supply is mostly impractical, since the fuse as a protection element has insufficient speed. In simpler terms, the fuse can burn out after the power elements of the power supply become unusable due to overload.
In general, the choice in favor of one or another limiter should be made taking into account the circuitry, and sometimes design features of the input voltage source and load features.
It would seem nonsense. Lamp resistance is measured in whole ohms, and battery resistance is tenths and hundredths of an ohm. Serial connection should lead to voltage redistribution: the lamp is 12 volts, the battery is 2 volts - and the battery will not be charged. But many of the people are not smart enough to predict the real outcome.
An incandescent (and halogen) lamp works like a barretter, having a variable internal resistance, depending on the heating (current flowing and voltage falling on it), which in turn changes the voltage drop across the lamp. As a result, the lamp maintains a relatively constant current in the circuit, limits this current, protects the circuit from short circuit - and having a low resistance, it very weakly steals the voltage from the load, even allowing the battery to be charged (possibly slower).
The greater the power of the lamp, the more current it will allow to pass. If you add to this the possibility of installing several lamps in parallel, you can adjust both the current strength of the entire circuit and the resistance of the bundle of lamps. And the more lamps - the more economical the circuit, because. the total resistance of the lamps is less, and they shine less. Similarly, when comparing the glow of 21W and 55W lamps: 55W glows much dimmer, despite the larger flowing current. And with the degree of battery charge, the light is getting dimmer, and then it will completely disappear - a kind of battery charge indicator: "a little left." None of the lamps caused blinding when looking at it.
(added 03/21/2016) The battery is not fully charged. When the current reached the minimum value of 1.1A, the battery stopped charging (while the current of 1.1A continues to flow, miracles). Total on the battery was 11.8V. This means that you need to add another transistor to the circuit, which, at a voltage of 12V on the battery, turned off the lamp and supplied current directly.
There is a dependence on the resistance of the lamp: the more powerful the lamp, the lower the resistance and the lower the voltage drop across it. I'll have to try with a 100W lamp later. And more time to charge: suddenly the process just increased 1.5 times in time.
(added 03/25/2016) The battery is charged to the end (theoretical empirical calculation), but: the charge time is so long (several days / weeks) that the addition from the 21st day can be considered true.
(added 03/26/2016) Wait for the check on the UPS battery. Finally finished off the car battery: she lived with a dead jar - and now the plates have fallen down. Perhaps the test current of 15A, which was started for 1 minute, is to blame for this. Maybe because of the crumbling plates, the "charging" did not end for a long time: the shorted plates successfully conducted a current of 1.1A - again, no miracles: just a lack of knowledge.
(added 03/27/2016) Everyone who has tried the method of charging the battery through a light bulb, unanimously says that it just coincided with the battery in terms of death: the lamp does not harm the battery. This is logical: it does not increase the current strength, but limits it; It doesn't raise the voltage, it lowers it. Moreover, lowering the voltage makes it possible to charge with non-standard power sources, the voltage of which is selected depending on the power of the lamp (the lower the power, the greater the excess voltage can be allowed). The correct calculation even allows you to charge the battery using a charger from a 19V laptop. In my case, when the battery stopped accepting a charge (and wasted energy on closed plates and electrolyte seething), there were 12.7V at the battery terminals at 14.4V on the power source, which means that the 21W lamp took 1.7V.
As a result, using a conventional power adapter and a light bulb, you can create a full-fledged charger for the battery. But this is a reason to check in practice: there are a lot of adapters at home, a lot of lamps. The main thing: during the test, do not miss the increase in voltage at the battery terminals above 14.4V if the lamp is not selected correctly.
(added 03/29/2016) It turns out that halogen lamps are quite fragile. I don’t know how, but the 55W lamp was damaged when pressed on the metal casing. Moreover, there are no visual signs of damage - and the current in the lamp flowed around the spiral. I know that you can’t touch quartz glass with your hands - however, the lamps did not burn out and did not fail in other ways: either the voltage is lower than the rated voltage, or the current, or the burning time.
(added 03/30/2016) Successfully charging the UPS battery through a 21W incandescent lamp. I can’t check on a car battery, because. there is no serviceable one - but the battery of the UPS is also acidic.
Table of lamp power and current limitation:
- 100W, halogen. For car battery: current<3.6А, для АКБ ИБП: <3.2А - для ИБП не годится,
- 55W, halogen. For car battery:<3А, для АКБ ИБП <2.9А - для ИБП не годится;
- 21W, incandescent. For car battery:<1.2-1.7А, АКБ ИБП: <1А - для авто не годится;
- 10W, incandescent. For UPS battery<0.3А - годится для маленьких аккумуляторов?
- 5W, incandescent. For UPS battery<0.2А - годится для маленьких аккумуляторов?
The data is based on a 5-year-old Bosch S4 019 battery and an APC 7Ah UPS battery, discharged to 6.6V. A choice was made in favor of 100W for the car battery and 21W for the UPS battery.
LED lamps are not suitable for this purpose.
(added 04/12/2016) The lamp gives gigantic possibilities. Redone
The device, assembled according to the scheme shown in Fig. 1, delays the supply of full mains voltage to the lamp by approximately 0.2 s - the duration of charging the capacitor installed in it. This is quite enough to effectively limit the inrush current through the cold coil of the lamp. The residual voltage drop across the limiter is about 5 V.
Initially, several copies of the limiter were assembled using MLT-0.5 resistors, a KT940A transistor, a KD105B diode, and a KU208G simistor. In the future, I switched to small parts, the types of which are indicated in the diagram, and lower power resistors, including those intended for surface mounting. This version of the limiter can be mounted on the printed circuit board shown in fig. 2.
With an EL1 lamp power of more than 100 W, the MAC97 triac must be replaced with a more powerful VT137 or VTA12-600. If such a thyristor is provided with a heat sink, and instead of the MJE13001 transistor, an MJE13003 is installed, the permissible load power will reach 2 kW. Capacitor C1 can be increased to 470 microfarads.
All manufactured limiters have been working flawlessly for more than three years.
Publication date: 08.08.2009
Readers' opinions
- Dmitry / 19.05.2014 - 10:16
Does anyone know the address of the author of this scheme ??? Here he would ask what details to put for powerful lamps ??? And then I also collected in the end - flickering and loss of power !!! [email protected] - satwalker / 13.02.2013 - 19:45
Instead of one MJE13001, we take 2 pcs. and from them we build a Darlington transistor. Tested with BTA06-600. You can reduce R4 to (47-22) kOhm. - Rafi / 02.10.2012 - 06:54
Very valid, pithy, succnict, and on point. WD. - Eugene / 08.09.2010 - 12:06
In this circuit, the triac opens only on the positive half-wave. Hence the flickering and dip in brightness. How not to change the values of the elements - you will not get rid of this chronicle. In addition, there is practically no pulse on the triac UE, and they (triacs) like it to be short and with steep fronts. And there is almost no smell of fronts here and this is determined by the voltage and opening speed of the transistor's number-em transition. The simistor does not live long under such conditions. The scheme is only 50% working, the idea is there, but it is developed at an embryonic level. - RonW / 01.11.2009 - 21:37
In my opinion, the problem is in the low transmission coefficient of the transistor - the MJE13001 has it at the level of 10-40 (I measured 20). With a large R4, there is not enough collector current to open the thyristor (for example, BT134). For more powerful ones, it can be even worse. KT940 has h>25 (I measured 60-70). Either use KT940 or reduce R4. - Vitaly / 12.10.2009 - 20:33
Eugene, decided to torment this scheme a little more. I used BT137 and MJE13003, I reduced the resistors R2, R3, R4 by 10 times, I took the capacitor at 2200 microfarads, R1 at 1 kOhm. The flickering decreased noticeably, but the resistors began to burn (or rather, part of it, since the pair had 1 watt changes). Can you advise... - Vitaly / 01.10.2009 - 19:01
If you close the collector-emitter, the lamp does not flicker, but I still tried to reduce the ratings: I halved R2 and R4 - I checked in all combinations, and R1 also took both 1 and 3 kOhm. I checked it on two different triacs and even tried to swap conclusions 1 and 2 - I don’t know if it’s possible to do this, but nothing burned out. I have no idea what else to try. - Eugene / 30.09.2009 - 15:32
And if you close the collector-emitter of the transistor, does the lamp flicker? If yes, try to reduce the resistor R4. Somewhere by half. You can try to reduce and R2. - Vitaly / 26.09.2009 - 14:46
I tried to assemble a circuit for a chandelier (about 400 watts) - I used BT137 and BTA12-600, and transistors MJE13003, BUT11AX, BUH515, BU2508DF, 2SC2482 and with all the same song - the lamp flares up to full but noticeably strong flicker !! I tried to reduce R1 to 1 kOhm, the conder took from 220 to 1500 microfarads. I also tried with these MAC97 transistors - there is no flickering only if you take kt940a - and then it does not flicker with any of the sevenstors, but the power is obviously not enough for 400W. Maybe it's possible to use some kind of Soviet transistor but more powerful? For example, kt812a or kt828a - the size will suit me, since the board will be hidden right in the chandelier. What do you think? - Vitaly / 25.09.2009 - 18:23
assembled a circuit using kt940a and mac97 - already 3 pieces and they all work great !!! Tomorrow I will buy new transistors, otherwise these turned out to be dead (I took from the ballast of a burned-out energy-saving lamp, at the same time I found out that they are constantly burning :)))) and I will try with powerful triacs. - Eugene / 18.09.2009 - 20:07
Your triac does not open in the second half-wave of mains voltage. Try to close the collector-emitter with a jumper and turn it on. If everything is assembled correctly, then the lamp will immediately light up at full heat. If not, then check the connection of the triac. Try reducing R1 to 1 kΩ. (eufs()email.ua) - Vitaly / 09.09.2009 - 18:08
Picked up this pattern today. I used BT137, 13003, 470 microfarad conder. There is a terrible flickering of a 100-watt lamp and a clear decrease in the brightness of the glow. Maybe something is wrong??? I'm just a layman by and large in all this, but on such simple schemes I'm trying to learn something and do something useful.
LAMP CURRENT LIMITER
Until now, there are people proving the effect of usingenergy savinglamps. We will now examine the truth or falsity of this statement.
We consider: the price of a good incandescent lamp (LN) is $ 0.4,energy-saving lamp (EL) - 4$. The service life of both is the same, about six months.
per day, savings from use(EL) is about 0.3 kW, for six months 0.3x180 = 60 kW. At the price of 1 kWh - 0.03$, the semi-annual effect will be 0.03x60 = 2$. Subtract this amount from the price(EL) and as a result we have 0.4$ per LN, against 2.0 $ per EL. Comments are superfluous.
To further enhance the superiorityincandescent lamps over energy-saving ones, we will make a simple circuit to limit the inrush current through the filament when turned onincandescent lamps.
The circuit of the lamp current limiter is taken from radio 8-2009 and is so simple that you can not poison the board, but cut it out with a cutter. Board size 20x25 mm. The principle of operation of the circuit is based on a smooth, within half a second, voltage supply to the lamp. In addition, as a result, not all 220 V are supplied, but about 200 V - which further increases the service life of the LN.
The most expensive itemlamp current limitertriac - costs $ 0.3, I think everyone has the rest of the details.
The KT940 transistor can be torn out of the color module of a non-working Soviet 3USCT TV - there are 6 of them. We will replace the triac with TS106-8. Capacitor 200 - 1000 microfarads at 10 V.
Finished board lamp current limiterwrapped with something insulating,
