SU1658132A1 - Pulse stabilizer of constant voltage - Google Patents

Abstract

This invention relates to electrical engineering and can be used in secondary power supply sources. The goal is to simplify and increase reliability. The device contains a power switch on transistors 12.13, a current sensor on resistors 15, 16 and transistor 14, an LCD filter 20, a comparator 4, diodes 17.18, a capacitor 19, a source 3 of reference voltage and resistors 5-11. The inclusion of a current sensor between the emitter of transistor 12 and the collector of transistor 13 reduces the voltage across the collector-emitter circuit of transistor 13 when it is open. The output current of the device is also limited by its rather simple circuit. 1 il. c (o

Description

This invention relates to electrical engineering and can be used in secondary power supply sources.

The aim of the invention is to simplify and increase the reliability of a DC voltage pulse stabilizer.

A schematic diagram of a switching voltage regulator is shown in the drawing.

The stabilizer contains pins 1.2 for connecting an unstabilized supply voltage source, a reference voltage source 3, a comparator 4, resistors 5,6,7,8,9,10,11, a power switch including an amplifying and a power transistor 1 / , 13, the current sensor on the transistor 14 and resistors 15,16, diodes 17,18, capacitor 19, LCD LO filter, output pins 21, 22, resistor 23.

The junction point of the emitter of the transistor 14 and the first pin of the resistor 15 is the first power lead of the current sensor. The connection point of resistors 15 and 16 is the second power output of the current sensor. The collector torus of the transistor 14 is an information output of a current sensor.

In a switching voltage regulator, transistors 12 and 13 can be used either field or conventional bipolar. In the first case, their power outputs are the drain and source, and the control output is the gate, in the second case, the power outputs of the transistors are the emitter and collector, and the control (it is the base).

This circuit uses bipolar transistors.

so about

OK

The switching voltage regulator operates as follows.

 Unstabilized voltage from the power supply source leads to pins 1 and 2. This voltage is 5–20 V higher than the output stabilized voltage.

Consider the operation of the stabilizer in the absence of resistor 23, i.e. when its resistance is infinity.

The resistance value of the resistor 7 is chosen to be much lower than the resistance of the resistor 5. Therefore, the voltage at the direct input of the comparator 4 is almost equal to the voltage at the output terminal 21.

The source 3 of the reference voltage produces at its output a stable low-voltage voltage, which is fed to the inverted input of the comparator 4.

When voltage is applied to input pins 1.2 at the first moment of time, the voltage at the output terminal 21 and the direct input of the comparator 4 is zero and at the inverse of the comparator it is equal to the voltage at the open diode 18, therefore, at the output of the comparator 4 there is a zero logic level .

Through the base-emitter junction of the transistor 12, the resistor 9 and the input of the comparator 4 current flows and the transistor 12 is in the open state. The collector current of transistor 12 is the base current of the power transistor 13, so the latter is also open.

As a result, through the resistor 15, the collector-emitter junction of the power transistor 13, the filter choke 20 flows1, which charges the filter capacitor 20 and the voltage at the output terminal 21 and the direct input of the comparator 4 increases. When the output voltage of the stabilizer is equal to the output voltage of the source 3 of the reference voltage, the comparator 4 is triggered and a high voltage appears at its output, which closes the transistor 12. The current through the emitter-collector junction from transistor 12 stops, As a result, the power transistor 13 closes. In this case, the energy accumulated in the choke and the capacitor of the filter 20 begins to be supplied to the load via the output terminals 21 and 22. The voltage on the output terminals 21, 22 starts.

Q

d 5

five

0

40

45

55

fall. When the output voltage of the stabilizer on them becomes less than at the output of the source of the reference voltage, the comparator 4 is activated and a logical zero appears again at its output. Transistors 12 and 13 open and all processes are repeated as described above.

In this case, the diode 18 is closed, since the comparator 4 is triggered by decreasing the voltage at the output terminals 21, 22 by 5-20 mV. And for opening the diode 18, it is necessary that the voltage at the output terminals 21,22 decreases by 300-400 mV.

Thus, a voltage equal to the output voltage of the reference voltage source is maintained on the output viewpoints. The positive feedback of the comparator 4 is performed with the help of the resistor 5. This connection improves the switching processes of the comparator 4 and prevents it from switching to the linear mode or the mode of high-frequency oscillations. The resistance value of the resistor 5 is chosen such that, as a result of an increase in the dead zone of the comparator 4, the ripple amplitude of the output stabilized voltage at the terminals 21, 22 does not exceed the allowable value.

The resistor 15 is low-resistance, its resistance R is chosen such that at rated load current the voltage drop across it is not enough to open the transistor 14, and when the load current reaches the maximum permissible value, the voltage drop across the resistor 15 reaches the switching threshold of the transistor 14, t .

R

K “5 T

ewx. Max

where U j .. is the base-emitter voltage of the transistor 14 in the open state; I .. „Al-i / r maximum allowed

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output current stabilizer.

Thus, when the value of the output current of the stabilizer reaches its maximum permissible value, the transistor 14 opens, while the capacitor 19 is charged to a voltage higher than the voltage at the output terminal 21, and the diode 17 opens. This overvoltage through resistor 6 is applied to the direct input

the comparator 4, as a result, the latter is switched to the single state and the transistors 17, 13 are closed. The current through the resistor 15 is stopped and the transistor 14 is also closed. But the comparator 4 continues to be held in unit state due to the energy stored in the capacitor 19.

The voltage at the output terminals 21, 22 decreases to zero. The diode 18 opens and the voltage at the inverted input of the comparator 4 decreases and becomes equal to the voltage drop across the open diode 18. The capacitor 19 discharges through the diode 17, the resistors 6.7, and also through the resistor 10. The voltage on the capacitor 19, and therefore , and at the direct input of the comparator 4 is reduced. When the voltage at the direct input of the comparator 4 becomes equal to the voltage at the inverse input, i.e. the voltage drop across the open diode 18, the comparator 4 switches to the zero state.

Due to this, transistors 12,13 are opened. Through the resistor 15 and the transition of the collector-emitter of the power transistor 13 begins to flow current. Due to the presence of drossel in the filter 20, this current increases smoothly. 1: The voltage drops across the resistor 15 increases. And if the current at the output of the stabilizer reaches a maximum value, the voltage drop across resistor 15 increases so much that transistor 14 opens again, which charges capacitor 19 and turns off transistors 12 and 13. Then all the processes are repeated as described above. . Thus, the output current of the stabilizer is limited.

The inclusion of a current sensor in the open circuit between the emitter of the transistor 12 and the collector of the transistor 13 reduces the voltage between the collector and the emitter of the power transistor 13 when the latter is in the open state. In this case, the voltage UK3 of the open power transistor 13 is equal to

ike (Ufois + Uiotz and where U j. - base-emitter voltage of transistor 13 in saturation mode; and e saturation voltage of collector-emitter of transistor 1 2 in saturation mode;

. . 20 5

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five

five

0

five

U. is the voltage between the power supply terminals of the current sensor when current flows through it.

When used as a current sensor resistor 15

UAT U 5 I «5 R 5.

where u). - voltage drop across resistor 15;

I, Y - the current flowing through the resistor 15;

R, 5- is the resistance value of the resistor 15.

Since the collector current of the power transistor 13 is approximately equal to the current of its emitter, the current through the resistor 15 is approximately equal to the output current of the stabilizer.

Reducing the voltage on the power transistor 13 when the latter is in the open state reduces the power dissipated on this transistor by an amount of 11dt, which saves the metal from which the heat sink of the power transistor 13 is made (and improves reliability.

If at the output pins 21, 22 of the stabilizer it is necessary to obtain a stabilized voltage greater than the output voltage of the source 3 of the reference voltage, then a resistor 23 is installed. The resistors 23 and 7 form a voltage divider.

At the same time, at the output terminals L 1,22 of the stabilizer, such a pressure will be maintained at which the voltage on the resistor 23 will be equal to the voltage on the output of the source 3 of the reference voltage. In this case, the diode 18 is locked by a potential difference between the output 21 and the output of the source 3 of the reference voltage. The rest of the stabilizer works in the same way as in the absence of a resistor 23.

The resistance values of resistors 8 and 9 are determined by the type of transistor 12 used and the output characteristics of comparator 4. So, if transistor 12 is a field or comparator 4 has a large output resistance, its output can be directly connected to the base or gate of transistor 12. Resistors 8 and 9 may be absent, i.e. the resistance of the resistor 9 is zero. If the direct input of the comparator 4 can suppress the input voltage to the output, then the cathode of the diode 17 can be i connected directly to the direct input of the comparator 4, i.e. resistor 6 can also be excluded.

Simplifying the stabilizer circuit reduces its cost.

Improving the reliability of the stabilizer, achieved by simplifying it, introducing it, is overwhelmed by overloads and reducing power dissipation on the power transistor, reduces the cost of operating the stabilizer and increases its service life.

Claims (1)

Invention Formula A DC voltage regulator containing a power switch, including power and amplifying transistors, an LCD filter whose input is connected to the output of the power switch, and the output connected to the first, output terminal, current sensor, first resistor, voltage source characterized in that, in order to simplify and increase reliability, second and third resistors, two diodes, a capacitor and a comparator are introduced into it, and the output of the reference voltage source  78 connected to the anode of the first diode and the first input of the comparator, the second input of which is connected to the first terminals of the first and second resistors and to the cathode circuit of the second diode, the output of the comparator is connected to the second output of the first resistor and to the control output circuit of the amplifying transistor whose first power output is connected with the first input terminal and with the first power output of the current sensor, the second power output of which is connected to the first power output of the power transistor, the second power output of the amplifying transistor is connected n with the control output of the power transistor, the second power output of which is used as the output of the power switch, the information output of the current sensor is connected to the anode of the second diode and to the first terminals of the capacitor and the third resistor, the second output of the second resistor is connected to the first output terminal, the output of the LCD filter and the cathode of the first diode, the second terminals of the capacitor and the third resistor are connected to the common bus, to the second input and output pins and to the terminals for connecting a common voltage source to the common bus And LCD filter.