7805 voltage regulator circuit diagram

7805 voltage regulator circuit diagram (I)

Voltage regulator ICs of the LM3 and LM7805 series have 7812 pins and are ideal for use in voltage regulator circuits. If you need higher currents , up to 3A, you must add a complementary transistor T2 to this schematic . In a normal design, if a short circuit occurs, the power dissipation can be very high. This problem can be solved with the voltage regulator design presented below.

This circuit design reduces the maximum current consumption when the output voltage drops when a short circuit occurs through electronics . On this regulator prototype, the maximum current when the output is short-circuited is only 0,5A, so overheating does not occur.

In this DC regulator circuit, T1 is used for current limiting. As soon as the voltage across R2+R3 is above 0,6-0,7V, T1 turns on, which causes the T2 base current to drop to zero. The voltage at which the short circuit protection starts to work is given by the sum of the voltages across R2 and R3. The R3 and R4 resistors form a voltage divider for T2.

7805 voltage regulator circuit diagram (II)

The 7800 series three-terminal voltage regulator integrated circuit is widely used in various electronic and electrical circuits for power supply voltage regulation. Its output voltage is fixed, but if the peripheral circuit is slightly modified, it can become a good continuously adjustable voltage regulator , which is completely feasible for experimental maintenance.

Before making it, you need to know: the 7800 series three-terminal voltage regulators are divided into three series according to the output current, namely the 78L00 series with a maximum output current of 0.1A; the 78M00 series with a maximum output current of 0.5A; and the 7800 series with a maximum output current of 1.5A. The input-output voltage difference of the three-terminal voltage regulator must be greater than 2V. The maximum input voltage of 7805-7818 cannot exceed 35V, and the maximum input voltage of 7820-7824 cannot exceed 40V.

5V-12V continuously adjustable regulated power supply made by 7805

Here, 7805 is used to make a 5V~12V continuously adjustable DC regulated power supply. The values ​​of R1 and R2 in the figure determine the adjustable range of the output voltage. According to the values ​​shown in the figure, the output voltage can be continuously adjusted within the 5~12V regulated range.

The maximum output voltage is limited by the maximum input voltage and the minimum input-output voltage difference of the three-terminal regulator. The maximum input voltage of 7805 is 35V, and the input-output voltage difference must be kept above 2V. Therefore, in this circuit, since the DC input voltage of the regulator is about 15V, the maximum output voltage of this circuit is set to 12V.

7805 voltage regulator circuit diagram (III)

The circuit shown in the figure is a regulated power supply with an output voltage of +5V and an output current of 1.5A. The power transformer b, bridge rectifier circuit D1~D4, smoothing capacitors C1, C3, self-excitation capacitors C2, C3 and fixed three- terminal regulator (7805) are very simple and convenient.

The 220V AC commercial power supply is converted into AC low voltage by the power transformer, and after rectification and smoothing by the bridge rectifier circuit D1~D4 and the smoothing capacitor C1, an unstable DC voltage is formed at both ends of Vin and GND of the fixed three-terminal regulator KIA7805 (this voltage always changes due to fluctuations in the commercial power supply voltage and changes in the load, etc.).

The DC voltage is stabilized by KIA7805 and smoothed by C3, and a DC output voltage with high precision and good stability is generated at the output end of the stabilized power supply. This stabilized power supply can be used as a power supply for TTL circuits and single-chip microcomputer circuits. The three-terminal voltage regulator is a standardized, series-connected universal linear stabilized power supply integrated circuit. It has the characteristics of small size, low cost, good performance, high working reliability, and easy use. It has become a monolithic integrated voltage stabilizer currently used in stabilized power supplies.