The L7805 CV integrated stabilizer is a conventional three-terminal 5V positive voltage regulator. Produced by STMircoelectronics, approximate price is about $1. Made in a standard TO-220 package (see figure), in which many transistors are made, however, its purpose is completely different.

In the marking of the 78XX series the last two digits indicate stabilized voltage rating, for example:

1. 7805 - 5 V stabilization;
2. 7812 - 12 V stabilization;
3. 7815 - stabilization at 15 V, etc.

The 79 series is designed for negative output voltage.

Is used for voltage stabilization in various low-voltage circuits. It is very convenient to use when it is necessary to ensure the accuracy of the supplied voltage; there is no need to install complex stabilization circuits, and all this can be replaced with one microcircuit and a couple of capacitors.

Connection diagram L7805CV

Connection diagram L 7805 CV It’s quite simple; to work, you need to place 0.33 µF capacitors at the input and 0.1 µF at the output according to the datasheet. It is important during installation or design to place the capacitors as close as possible to the terminals of the microcircuit. This is done to ensure the maximum level of stabilization and reduce interference.

By characteristics The L7805CV stabilizer is operational when an input DC voltage is supplied in the range from 7.5 to 25 V. The output of the microcircuit will have a stable DC voltage of 5 Volts. This is the beauty of the L7805CV chip.

Checking the functionality of the L7805CV

How to check functionality microcircuits? To begin with, you can simply ring the terminals with a multimeter; if in at least one case a short is observed, then this clearly indicates a malfunction of the element. If you have a power source of 7 V or higher, you can assemble a circuit according to the datasheet given above and apply power to the input; at the output, use a multimeter to record the voltage at 5 V, so the element is absolutely operational. The third method is more labor-intensive if you do not have a power source. However, in this case, you will also receive a 5 V power supply in parallel. It is necessary to assemble a circuit with a rectifier bridge according to the figure presented below.

Needed for verification a step-down transformer with a transformation ratio of 18 - 20 and a rectifier bridge, a further standard kit, two capacitors for the stabilizer and that’s it, the 5 V power supply is ready. The capacitor values ​​here are overestimated in relation to the L7805 connection diagram in the datasheet, this is due to the fact that it is better to smooth out voltage ripples after the rectifier bridge. For safer operation, it is advisable to add an indication to visualize the device being turned on. Then the diagram will look like this:

If there are a lot of capacitors or any other capacitive load on the load, you can protect the stabilizer with a reverse diode to prevent the element from burning out when the capacitors are discharged.

The big advantage of the microcircuit is Quite lightweight design and ease of use, if you need power of one value. Circuits sensitive to voltage values ​​must be equipped with such stabilizers to protect elements sensitive to voltage surges.

Characteristics of the L7805CV stabilizer, its analogues

Main settings stabilizer L7805CV:

1. Input voltage - from 7 to 25 V;
2. Power dissipation - 15 W;
3. Output voltage - 4.75...5.25 V;
4. Output current - up to 1.5 A.

Characteristics of the microcircuit shown in the table below, these values ​​are valid subject to certain conditions. Namely, the temperature of the microcircuit is in the range from 0 to 125 degrees Celsius, the input voltage is 10 V, the output current is 500 mA (unless otherwise specified in the conditions, the Test conditions column), and the standard body kit with capacitors at the input is 0.33 μF and at the output 0 ,1 µF.

The table shows that the stabilizer behaves perfectly when powered at the input from 7 to 20 V and the output will stably output from 4.75 to 5.25 V. On the other hand, supplying higher values ​​leads to a more significant spread of output values , therefore, above 25 V is not recommended, and a decrease in the input of less than 7 V will generally lead to the absence of voltage at the output of the stabilizer.

, more than 5 W, it is necessary to install a radiator on the chip to avoid overheating of the stabilizer, the design allows this to be done without any questions. Naturally, such a stabilizer is not suitable for more precise (precision) equipment, because has a significant spread in the rated voltage when the input voltage changes.

Since the stabilizer is linear, it makes no sense to use it in powerful circuits; stabilization based on pulse-width modeling will be required, but for powering small devices As phones, children's toys, radio tape recorders and other gadgets, the L7805 is quite suitable. The domestic analogue is KR142EN5A or in common parlance “KRENKA”. In terms of cost, the analogue is also in the same category.

Currently, it is difficult to find any electronic device that does not use a stabilized power supply. Mainly as a power source, for the vast majority of various radio-electronic devices designed to operate from 5 volts, the best option would be to use a three-pin integrated 78L05.

Description of stabilizer 78L05

This stabilizer is inexpensive and easy to use, which makes it easier to design radio-electronic circuits with a significant number of printed circuit boards, to which an unstabilized DC voltage is supplied, and each board has its own stabilizer mounted separately.

The microcircuit - stabilizer 78L05 (7805) has thermal protection, as well as a built-in system that protects the stabilizer from overcurrent. However, for more reliable operation, it is advisable to use a diode to protect the stabilizer from a short circuit in the input circuit.

Technical parameters and pinout of stabilizer 78L05:

• Input voltage: 30 volts.
• Output voltage: 5.0 volts.
• Output current (maximum): 100 mA.
• Current consumption (stabilizer): 5.5 mA.
• Permissible input-output voltage difference: 1.7 volts.
• Operating temperature: -40 to +125 °C.

Multifunctional device for testing transistors, diodes, thyristors...

Analogs of stabilizer 78L05 (7805)

There are two types of this microcircuit: powerful 7805 (load current up to 1A) and low-power 78L05 (load current up to 0.1A). The foreign analogue of 7805 is ka7805. Domestic analogues for 78L05 are KR1157EN5, and for 7805 - 142EN5

Connection diagram 78L05

A typical connection circuit for the 78L05 stabilizer (according to the datasheet) is easy and does not require a large number of additional radio elements.

C1 at the input is necessary to eliminate RF interference when applying input voltage. Capacitor C2 at the output of the stabilizer, as in any other power source, ensures the stability of the power supply during sudden changes in load current, and also reduces the degree of ripple.

When designing a power supply, it is necessary to keep in mind that for stable operation of the 78L05 stabilizer, the input voltage must be at least 7 and no more than 20 volts.

Below are some examples of using the 78L05 Integrated Regulator.

Laboratory power supply for 78L05

This circuit is distinguished by its originality, due to the non-standard use of the microcircuit, the source of the reference voltage of which is the 78L05 stabilizer. Since the maximum permissible input voltage for the 78L05 is 20 volts, to prevent the 78L05 from failing, a parametric stabilizer was added to the circuit using the zener diode VD1 and resistor R1.

The TDA2030 chip is connected as a non-inverting amplifier. With this connection, the gain is 1+R4/R3 (in this case 6). Thus, the voltage at the output of the power supply, when the resistance of resistor R2 changes, will change from 0 to 30 volts (5 volts x 6). If you need to change the maximum output voltage, this can be done by selecting the appropriate resistance of resistor R3 or R4.

Kit for assembling an adjustable power supply...

Transformerless 5 volt power supply

this is characterized by increased stability, lack of heating of the elements and consists of accessible radio components.

The structure of the power supply includes: a power indicator on the HL1 LED, instead of a conventional transformer - a damping circuit on elements C1 and R2, a diode rectifier bridge VD1, capacitors to reduce ripple, a 9-volt zener diode VD2 and an integrated voltage regulator 78L05 (DA1). The need for a zener diode is due to the fact that the voltage from the output of the diode bridge is approximately 100 volts and this can damage the 78L05 stabilizer. You can use any zener diode with a stabilization voltage from 8...15 volts.

Attention!Since the circuit is not galvanically isolated from the mains, care should be taken when setting up and using the power supply.

Simple regulated power supply on the 78L05

The adjustable voltage range in this circuit is from 5 to 20 volts. The output voltage is changed using variable resistor R2. The maximum load current is 1.5 amperes. It is best to replace the 78L05 stabilizer with 7805 or its domestic analogue KR142EN5A. Transistor VT1 can be replaced with. It is advisable to place the powerful transistor VT2 on a radiator with an area of ​​at least 150 square meters. cm.

Simple and intuitive operation, fast and accurate selection of voltage and current...

Universal charger circuit

This charger circuit is quite simple and universal. Charging allows you to charge all types of batteries: lithium, nickel, as well as small lead batteries used in uninterruptible power supplies.

It is known that when charging batteries, a stable charging current is important, which should be approximately 1/10 of the battery capacity. The constant charging current is ensured by the 78L05 (7805) stabilizer. The charger has 4 charging current ranges: 50, 100, 150 and 200 mA, which are determined by resistances R4…R7, respectively. Based on the fact that the output of the stabilizer is 5 volts, then to obtain, say, 50 mA, a 100 Ohm resistor is needed (5V / 0.05 A = 100) and so on for all ranges.

The circuit is also equipped with an indicator built on two transistors VT1, VT2 and an LED HL1. The LED goes off when the battery is charging.

charging current: 500 mA/h, 1000 mA/h. charging modes with constant...

Adjustable current source

Due to negative feedback through the load resistance, the voltage Uin is located at input 2 (inverting) of the TDA2030 (DA2) microcircuit. Under the influence of this voltage, a current flows through the load: Ih = Uin / R2. Based on this formula, the current flowing through the load does not depend on the resistance of this load.

Thus, by changing the voltage supplied from variable resistor R1 to input 1 of DA2 from 0 to 5 V, with a constant value of resistor R2 (10 Ohms), you can change the current flowing through the load in the range from 0 to 0.5 A.

A similar circuit can be successfully used as a charger for charging all kinds of batteries. The charging current is constant during the entire charging process and does not depend on the level of discharge of the battery or on the variability of the supply network. The charge current limit can be changed by decreasing or increasing the resistance of resistor R2.

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Almost all amateur radio homemade products and designs include a stabilized power source. And if your circuit operates on a supply voltage of 5 volts, then the best option would be to use a three-terminal integrated stabilizer 78L05

In nature, there are two varieties of 7805 with a load current of up to 1A and the lower-power 78L05 with a load current of up to 0.1A. In addition, an intermediate option is the 78M05 microcircuit with a load current of up to 0.5A. Complete domestic analogues of the microcircuit are for 78L05 KR1157EN5 and 7805 for 142EN5

Capacitance C1 at the input is required to cut off high-frequency interference when applying input voltage. Capacitance C2, but already at the output of the stabilizer, sets the voltage stability during a sharp change in the load current, and also significantly reduces the degree of ripple.

When designing, you need to remember that for normal operation of the 78L05 stabilizer, the input voltage must be no lower than 7 and no higher than 20 volts.

The control circuit allows you to supply and disable power going to the voltage stabilizer. The control signal must be TTL or CMOS level. The circuit can be used as a power switch controlled by a microcontroller.

Below we will consider a selection of the most interesting examples of the practical use of the 78L05 integrated stabilizer.

This design of the laboratory power supply is distinguished by its sophistication, primarily due to the non-standard use of the TDA2030 microcircuit, the source of which is stabilized voltage is 78L05.

The TDA2030 is included as a non-inverting amplifier. With this connection, the gain is calculated by the formula 1 + R4/R3 and is equal to 6. Therefore, the voltage at the output of the power supply, when adjusting the resistance value R2, will smoothly change from 0 to 30 volts.

Increased stability and no overheating of radio components are the main advantages of this design.

The power-on indicator is made on the HL1 LED; instead of a transformer, a damping circuit is used on components C1 and R1, a diode rectifier bridge on a specialized assembly, capacitors are used to minimize ripple, a 9-volt zener diode and a 78L05 voltage stabilizer. The need to use a zener diode is determined by the fact that the voltage from the output of the diode bridge is about 100 volts and this can damage the 78L05 stabilizer.

The voltage range in this circuit is from 5 to 20 volts. The output voltage is changed by variable resistance R2. The maximum load current is about 1.5 amperes.

The device is capable of charging different types of batteries: lithium, nickel, as well as lead batteries used in uninterruptible power supplies.

When charging batteries, you need a stable charging current, which should be about 1/10 of the battery capacity. The constancy of the charging current is set by the stabilizer 78L05. The charger has four charging current ranges: 50.5 volts, then to obtain a current of 50 mA a resistance of 100 ohms is required based on Ohm's law. For convenience, the design of the charger has an indicator made of two bipolar transistors and an LED. The LED goes out when the battery is charging.

Susanne Nell

If you need a high efficiency power supply, but don't want to use expensive DC/DC converter chips, then the circuit in Figure 1 is for you. It is based on IC 1, a widely used, low-cost linear voltage regulator LM7805. A circuit whose external switch is a pnp transistor can easily deliver an output current of more than 1 A. An additional useful feature is that the switching circuit automatically turns off when there is no load or when the output current drops to a few milliamps. Under these conditions, the circuit begins to operate as a conventional linear regulator. After the input voltage is turned on for the first time, current will flow to the output through resistor R 1 and the LM7805 microcircuit. In addition, current will flow through the emitter-base junction Q 1 and turn on the transistor. The current through inductance L 1 will begin to increase, and the output capacitor C 2 will charge. When the output voltage reaches the regulator's rated voltage (5V for LM7805), the regulator output will turn off.

From this point on, transistor Q 1 turns off as the LM7805 interrupts its base current. After closing the key, the voltage across the inductance changes polarity, and current begins to flow through diode D 1. When a load is connected, the output current discharges capacitor C2. When the circuit's output voltage drops a few millivolts below the LM7805's 5V output voltage, the circuit will begin delivering current to the load again. As a result, Q 1 is turned on, and the cycle repeats again. At low or no load, all output current flows through the LM7805 and transistor Q 1 remains off. You can change the starting current of the switching circuit by selecting the appropriate resistance of the resistor R 1.

This circuit can also be used for voltages higher than 5 V. By replacing the LM7805 with an LM7812 or LM7815, you will get an output voltage of 12 or 15 V. For such higher voltages, resistors R 2 and R 3 will need to be added to the circuit. These resistors introduce a slight hysteresis into the circuit, reducing the switching frequency. Typical values ​​of their resistances are 2.2 ohms and 2.2 kohms, respectively. By converting 24V to 12V using the circuit in Figure 1, you can achieve an efficiency of about 75. Using a 5V regulator, the efficiency drops to 65%, but this is still better than you can get from a simple linear regulator.

Related materials

The L7805 voltage regulator is designed to stabilize high input voltage (7-35V) to 5V. Characteristics of the voltage stabilizer LM7805: Housing: TO-220 Current strength: 1.5 AN Maximum input voltage:...

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• The little crap in sot23+4.7uH choke does the same thing. At frequencies from 800KHz to megahertz. These collective farm technologies were still published by the Radio Devils magazine when. But it made sense then. Not now.
• it will work, of course. only here the principle of determining stabilized voltage using a comparator is used. Therefore, the presence of ripples at a stabilized voltage is important. and, most likely, it will not be millivolts. and if the goal is to reduce the cost of the converter, then instead of a cheap stabilizer, you can use an even cheaper transistor in an SMD package. issue price - 1 cent.

Devices that are included in the power supply circuit and maintain a stable output voltage are called voltage stabilizers. These devices are designed for fixed output voltages: 5, 9 or 12 volts. But there are devices with adjustment. They can be set to the desired voltage within certain accessible limits.

Most stabilizers are designed for a certain maximum current that they can withstand. If you exceed this value, the stabilizer will fail. Innovative stabilizers are equipped with a current blocking, which ensures that the device is turned off when the maximum current in the load is reached and are protected from overheating. Along with stabilizers that maintain a positive voltage value, there are also devices that operate with negative voltage. They are used in bipolar power supplies.

The 7805 regulator is manufactured in a transistor-like package. Three conclusions are visible in the figure. It is designed for a voltage of 5 volts and a current of 1 ampere. There is a hole in the case for fixing the stabilizer to the radiator. The 7805 is a positive voltage device.

The mirror image of this regulator is its 7905 negative voltage counterpart. There will be a positive voltage on the case, a negative value will be sent to the input. -5 V is removed from the output. In order for the stabilizers to work in normal mode, 10 volts must be supplied to the input.

Pinout

The 7805 stabilizer has a pinout, which is shown in the figure. The common terminal is connected to the housing. This plays an important role during installation of the device. The last two digits indicate the voltage output by the microcircuit.

Stabilizers for powering microcircuits

Let's consider methods for connecting digital devices made independently using microcontrollers to power. Any electronic device requires a proper power connection to function properly. The power supply is designed for a certain power. A capacitor of significant capacity is installed at its output to equalize voltage pulses.

Power supplies without stabilization, used for routers, cell phones and other equipment, are not directly combined with power supply to microcontrollers. The output voltage of these blocks varies and depends on the connected power. An exception to this rule are chargers for smartphones with a USB port that outputs 5 V.

Scheme of operation of the stabilizer, compatible with all microcircuits of this type:

If you disassemble the stabilizer and look at its insides, the diagram would look like this:

For electronic devices that are not sensitive to voltage accuracy, such a device is suitable. But for accurate equipment you need a high-quality circuit. In our case, the 7805 stabilizer produces a voltage in the range of 4.75-5.25 V, but the current load should not be more than 1 A. The unstable input voltage fluctuates in the range of 7.5-20 V. In this case, the output value will always be equal to 5 B. This is an advantage of stabilizers.

When the load that the microcircuit can deliver increases (up to 15 W), it is better to provide the device with cooling by a fan with an installed radiator.

Efficient stabilizer circuit:

Technical data:

• Maximum current 1.5 A.
• Input voltage range – up to 40 volts.
• Output – 5 V.

To avoid overheating of the stabilizer, it is necessary to maintain the lowest input voltage of the microcircuit. In our case, the input voltage is 7 volts.

The microcircuit dissipates the excess power onto itself. The higher the input voltage on the chip, the higher the power consumption, which is converted into heating the case. As a result, the microcircuit will overheat and the protection will trip and the device will turn off.

Voltage stabilizer 5 volts

This device differs from similar devices in its simplicity and acceptable stabilization. It uses the K155J1A3 chip. This stabilizer was used for digital devices.

The device consists of working units: a trigger, a reference voltage source, a comparison circuit, a current amplifier, a transistor switch, an inductive energy storage device with a diode switch, input and output filters.

After connecting the power, the starting unit, which is made in the form of a voltage stabilizer, begins to operate. A voltage of 4 V appears at the emitter of the transistor. Diode VD3 is closed. As a result, the reference voltage and current amplifier are turned on.

The transistor switch is closed. A voltage pulse is generated at the output of the amplifier, which opens a switch that passes current to the energy storage device. The negative connection circuit in the stabilizer is turned on, and the device goes into operation mode.

All used parts are carefully checked. Before installing a resistor on the board, its value is set to 3.3 kOhm. The stabilizer is first connected to 8 volts with a load of 10 ohms, then, if necessary, set it to 5 volts.