RU1771536C - Device for developing high or low impedance between two output terminals - Google Patents

Abstract

Usage: the invention relates to electronic equipment and can be used in telecommunication systems. SUMMARY OF THE INVENTION - the device contains two identical switching elements, four output terminals, two output terminals of the control unit, three bipolar transistors, four MOS transistors, two capacitors and two diodes, 5 il.

Description

The invention relates to electronic equipment and can be used in telecommunication systems.

The purpose of the invention is to increase reliability by providing voltage control of opposite polarity between the first and second terminals.

In Fig.1 shows a diagram of the proposed device, in Fig. 2 is a diagram of a device with protective equipment, in FIG. 3 - volt-ampere characteristics (CVC) of the proposed device with protective equipment, in FIG. 4 and FIG. 5 - CVC of protective equipment (not to scale).

The device contains two identical switching elements 1 and 2 (only the first is presented in detail).

Depending on the control signal, element 1 can represent either a low or a high impedance between its two output terminals 3 and 4, to which the output terminals 5 and 6 of element 2 are respectively connected, both elements being connected in counter-parallel. This allows you to work with them in

in three different modes: elements 1 and 2 represent a high impedance between their terminals, element 1 represents a low impedance to voltage one polarity at the terminals of the device, while element 2 can also represent this low impedance, but for a different polarity.

The device also contains a control unit, the inputs of which are connected to the output terminals 3.4 and 5.6, and the outputs are one third of the third and fourth quarter of the terminal.

Each switching element is a triple MOS structure consisting essentially of a pnp type transistor 19, which is connected to an npn type transistor 10 so that a thyristor forms between terminals 3 and 4. The manufacture of such an element leads to the appearance of a parasitic thyristor 11 of pnp type, which is connected in parallel with transistors 9 and 10. The combination of transistors 9, 10 and 11 is a thyristor with two control electrodes. Each element 1 and 2 also contains two MOS transistors 12 and 13 of the diffusion type, the first and

cl

with

Xi vj

cl

Cj

about

s

the second power leads of the thyristor are connected to terminals 3 and 4, respectively, the first control electrode of the thyristor is connected to the drain of transistor 12, and the second control electrode is connected to the source of transistor 13, the gates of transistors 12 and 13 are combined and connected to the fourth terminal 8, and the source of the transistor 12 and the drain of transistor 13 are connected to terminal 4 to form a capacitance between terminals 4 and 8.

The control unit contains the third 14 and fourth 15 p-channel type MOS transistors, the sources of each transistor 14 and 15 are connected to terminal 7, the drain of transistor 14 and the gate of transistor 15 are connected to terminal 3 (5), the drain of transistor 15 and the gate of the transistor 14 are connected to terminal 4 (6).

In FIG. 1, dashed capacitances 16 and 17 and diodes 18 and 19 are also shown.

The device of FIG. 2 is a modification of the switching elements 1 and 2 of FIG. 1. Remaining a triple MOS type thyristor, thyristor 20 formed between terminals 3 and 4 is slightly different from the thyristor shown schematically in FIG. 1, in that the transistor 9 is replaced by a p-n-p-type transistor 21, which has two separate collectors connected to the bases of the n-p-n-type transistors 22 and 23, respectively, which replace the transistor 10, and the transistor 11 is not represented. In addition, individual power protection devices are associated with the thyristor 20. The first power limiting means comprises first and second sensing elements, a first decoupling element and a first regulating element, wherein the first sensing element is made on the first 24 resistor, the second sensing element is made on the second 25 and third 26 resistors, which are connected in series, the first decoupling the element is made on the fifth 27 of the n-channel type MOS transistor and ensures that the first power limiting means is turned off only after the thyristor 20 has a high impedance, p The first control element is made on the first 28 n-p-n-transistor and provides a gradual decrease in the current passing through the thyristor 20 with increasing voltage on it.

The second power limiting means comprises a third sensing element, a diode, a second decoupling element and second and third regulating elements, the third sensing element being made on the fourth 29 resistor, the second decoupling element being made on

the sixth 30 MOSFET of the p-channel type and ensures that the second means of limiting power is turned off only after the thyristor 20 is set high

impedance, the second and third regulating elements are made on the second 31 and third 32 n-p-n-transistors, the transistor 31 provides a decrease in the current passing through the thyristor 20 with high speed

0 until then. while the voltage on the thyristor 20 exceeds a predetermined value.

The switching elements 1 and 2 also contain a control element made on a diffusion MOS transistor 33

5 and enabling the first and second power limiting means to turn on and off after the thyristor 20 has set a high impedance.

In this case, terminal 3 is connected to the emitter of transistor 21 (first power output of thyristor 20), and terminal 4 is connected to the emitter of transistor 22 (second power output of thyristor 20) and through resistor 24 to the emitter of transistor 23. Base of transistor 22 (second control the thyristor’s electrode 20) is connected to the collector of the transistor 31, the emitter of which is connected to terminal 4. Terminal 3 is connected to the base of the transistor 31 through a cascade connection of the diode 34. the collector-emitter junction of the transistor 32 and the resistor 29. the cathode of the diode 34 is connected to the emitter of the transistor 23 (optional thyristor output 20) through a series-connected resistor 25. transition

5, the drain-source of the transistor 27 and the resistor 26. The connection point of the resistor 26 and the source of the transistor 27 is connected to the base of the transistor 28, the collector of which is connected to the base of the transistor 23 (the first control terminal of the thyristor 20), and the emitter to terminal 4 The cathode of the diode 34 is also connected to the drain of the transistor 30, the source of which is connected to the base of the transistor 32, which is connected to the detector output terminal

5 35, the gates of the transistors 27 and 30 are connected to the drain of the transistor 33, the source of which is connected to terminal 8, and the gate to terminal 4.

The device operates as follows.

0 Assuming that the capacitor 16 is positively charged at its terminals connected to both gates of the transistors 12 and 13 with respect to terminal 4, and so on. on the other hand, the voltage at terminal 3 is

5 more positive than the voltage at terminal 4, transistor 12 becomes conductive, which leads to the appearance of current from terminal 3 to terminal 4 through transistor 9 due to the short circuit of transistor 12 through its drain-source channel to the base of transistor 9. s which is connected to this drain, the emitter of transistor 9 being connected to terminal 3. The consequence of this conductivity of transistor 9 is to pump current into the base of transistor 10, which is directly connected to the collector of transistor 9 as follows. that transistor 10 begins to pump current into the base of transistor 9, which is directly connected to the collector of transistor 10, the emitter of which is directly connected to terminal 4. Moreover, due to this cumulative effect, both transistors 9 and 10 enter saturation mode, creating a low impedance between terminals 3 and 4. The pnp-type transistor 11, as well as the transistor 9, and the bases and emitters of the transistors 9 and 11 are respectively interconnected, while the collector of the transistor .11 is connected to the terminal 4, also becomes conductive, but at the same time there is a parasitic electric An element that does not affect the basic operation of the device.

The switching element 1, which creates a small resistance between the terminals 4 and 3, can be switched back to high impedance mode using a negative charge on the capacitor 16, and the negative potential at the gates of the transistors 12 and 13 relative to the terminal 4 creates the conditions for the operation of the p-channel MOS transistor 13. While the drain of the p-channel MOS transistor 12 is connected to the base of the transistor 9 and the source of the transistor 13 is connected to the collector of the transistor 9 so that the current from the collector of the transistor 9 flows to the transistor 13, so that the base transient current torus 10 becomes insufficient to maintain conduction of transistor 10 which, through the cumulative effect is blocked as the transistors 9 and 11 and the combination of transistors 9, 10 becomes nonconductive.

The switching element 2 operates like the element 1. but only under the control of a positive or negative charge on the capacitor 17, in particular on the terminal 8 with respect to the terminal 6. But these operations of the element 2 are carried out when the polarity on the terminal b is positive with respect to polarity at terminal 5.

Capacities 16 and 17 can be caused by stray capacitors, in particular those that occur on the gates of transistors 12 and 13 for capacitance 16. Capacities 16, like 17, can be charged in a given polarity using a separate control unit connected to terminals 7 and 8.

 It turns out on transistors 14 and 15 that if, for example, the potential at terminal 3 is higher than the potential at terminal 4, then the potential at terminal 7 cannot be within this range, and transistors 14 and 15 are conductive and respectively blocked, which expressed in that. what's the terminal

7 practically (0.7 V) is connected to terminal 4. Spurious diodes 18 and 19 between the source and drain of transistors 14 and 15, as shown in FIG. 1, are biased so that they play a similar role, allowing

0 terminal 7 equals potential with terminal 4. when this latter is less positive than the potential at terminal 3.

Of course, due to the symmetry of the control unit 5 made up of transistors 14 and 15, when the potential at terminal 4 is higher than the potential at terminal 3. The modes are inverted following the conductivity of transistor 14 of diode 18, terminal 7 is almost connected to terminal 5, so it is capacity 17 that is really connected to terminals 7 and 8.

In this case, a separate control unit can automatically close or open elements 1 or 2 depending on the polarity of the voltage applied between terminals 3 (4) on the one hand and 4 (3) on the other.

Thyristor 20 turns on and off

0 using MOS transistors corresponding to transistors 12 and 13, controlled from terminal 8. The switching elements 1 and 2 contain power protection devices, which can also control the thyristor 20,

5 Thyristor 20 is associated with two separate power protection devices. The first means of power protection contains elements 34, 25,27,28.26 and 24, the second contains elements 34,30,32,29 and 31, and in particular limits

0 current through the thyristor 20, when the voltage on the element 1 exceeds a predetermined value. It should be noted that in the following description of the operation of protective equipment it is assumed that the voltage at the terminal

5 3 is positive with respect to the voltage at terminal 4, so that the diode 34 is biased forward. The same operation is valid for element 2 in the case where the voltage at terminal 5 is positive with respect to the voltage at terminal 6.

The first and second protection means are introduced and taken out of operation by MOSFETs 27 and 30 of the n-channel type, which

5 are themselves controlled by the diffusion MOS transistor 33. When the thyristor 20 is in the ON position, the positive control voltage of the order of +20 V applied to terminal 8 is transmitted to the gates of the transistors 27 and 30 through the stray

the diode of the transistor 33. As a result, the transistors 27 and 30 are conductive, and the protective equipment is turned on. To turn off the thyristor 20, the control voltage at terminal 8 decreases from its positive value of the order of +20 V to a negative value of the order of -20 V. With this voltage drop, the thyristor 20 turns off when the voltage at terminal 8 reaches -3 V while the protective devices remain in operation, even if the parasitic diode of the diffusion MOS transistor 33 is locked. Indeed, M-channel type MOS transistors are still conductive due to the positive voltage held by the gate capacitance. When the voltage at terminal 8 reaches a value of about -8 V, the transistor 33 becomes conductive, so that this negative control voltage is applied to the gates of the transistors 27 and 30 and locks them. Then the protective equipment is out of work. The transistor 33 is connected to the gate capacitance of the transistors 27 and 30, thereby causing a delay circuit, which disables the protection means some time after the thyristor 20 is closed. Thus, the device protection remains in operation while the thyristor 20 is in the state nii on

When the thyristor is in the ON state, no current flows through the second power protector. But the voltage on element 1 will not exceed a value approximately equal to the voltage drop across three diodes. These three diodes are diode 34, the base-emitter junction of the transistor 32, and the base-emitter junction of the transistor 31. It should be noted that the current flowing through the second power protection means is so small that the voltage drop across the resistor 29 can be neglected. and the voltage drop at the drain-source junctions of the conducting transistor 30 can also be neglected, since it is proportional to the base current of the transistor 32 which is still locked. When the voltage at element 1 increases, transistor 31 becomes conducting it. The collector current flows from the base of transistor 22 to terminal 4. As soon as the base current of transistor 22 decreases, its collector current and, therefore, the base current of transistor 21 also decreases. As a result, the part 21 (22) of the thyristor 20 is turned off, while its part 21 (23) can remain in the ON state. During this operation, the main current in the transistor is limited

a resistor 29 and a transistor 32, which itself is controlled by a transistor 30.

When considering only part 21 (23) of thyristor 20, it is necessary to take into account

The I – V characteristic of the switching element 1 shown in FIG. 3, where part 36 is the normal I – V characteristic of the bias thyristor 20. As you can see, the voltage rises to the maximum voltage On equal to the voltage drop across three diodes (± 2.1 V) and corresponding to the maximum current of the backbone (32 Ohms). It follows that the transistor 31 becomes active at a maximum voltage Uo corresponding to a current of 1 volts.

5 so that the thyristor 20 is turned off and follows part 37 of the current-voltage characteristic. The current in the thyristor 20. and therefore in the switching element 1, essentially becomes equal to zero, whatever the voltage on this element, so

0 that in this case, the I – V characteristic almost coincides with the axis of voltages for voltages exceeding UD. It should be noted that this I – V characteristic is valid for thyristor 20. as well as for switching element 1.

5 The load line 38 of the switching element 1 is determined by two points corresponding to the maximum current IL (7 Ohms) in the load when the latter is short-circuited and the maximum voltage UL (70 V) when the load is open. This line intersects part 36 of the I – V characteristic of the switching element 1 at a stable operating point 39.

When unwanted abnormal signals are applied to the load, they are added to the normal signals, so that the load line moves along the I – V curve of FIG. 3. Such abnormal signals can have a different origin, for example,

0 there may be surges due to the inclusion of illumination or the voltage of the main power supply accidentally hit the load. Then the operating point moves along part 36 of the current-voltage characteristic. When these unwanted abnormal signals become very large, the load line 38 can move so that the operating point reaches the upper end of the I – V characteristic portion 36. Then this operating point becomes unstable and moves to

0 higher voltages until the thyristor 20 turns off (part 37). However, the maximum voltage DM on the switching element 2 is limited to 250 V by an overvoltage protection circuit 5, so that the operating point is located at the point UM on the voltage axis.

When the abnormal signals disappear, the load line 38 shifts back to the position indicated in FIG. 3, and the operating point moves from UM (250 V) to UL (70

B, where the portion of the I – V characteristic of the thyristor 20, which coincides with the voltage axis, crosses the load line 38. Thus, the operating point becomes stable under UL voltage and, since then the second power protection means becomes active again, it is not possible to turn on the thyristor 20. For it to turn on again, part 37 and part of the I – V characteristic of switching element 1. coinciding with the voltage axis should not cross the load line 38 so that there should not be a stable UL operating point between the UM and the normal operating point 39. The solution is to use the first power protection device.

If we consider only this part of the power protection, when the switching element 1 is in the ON state, the current flows from terminal 3 to terminal 4 not only through the thyristor 20, but also through the diode 34, resistor 25, the drain-source transition of the MOS transistor 27 and resistors 26 and 24 connected in series. As long as the voltage between terminals 3 and 4 is relatively small, so that the voltage drop created by the currents on the resistors 24 and 26. connected in series, is less than the saturation voltage 1) at the base-emitter junction of the transistor 28, the latter remains locked. Then, the current flowing through the thyristor 20 changes depending on the voltage measured on the switching element in accordance with the current-voltage characteristic part 40 shown in FIG. 4. In accordance with the values of the resistors, the current I flowing through the thyristor 20 is much larger than the current flowing through the first protective device. Consequently, current 1 can be considered as current flowing through switching element 1, and the current-voltage characteristic in FIG. 4 is valid for thyristor 20, as well as for switching element 1. When the voltage between terminals 3 and 4 is so large that the voltage drop created on the resistors 24 and 26 by the indicated currents becomes larger than the UBE on transistor 28, the latter becomes a wire thereby creating a shunt transition to terminal 3 for the collector current through the transistor 21. Thus, the base current of the transistor 23 is reduced, resulting in an increase in the impedance of the thyristor 20, so that the current I flowing through it changes depending on the voltagevoltage as shown by the current-voltage characteristic part 41 in Fig. 4. This change is a function of the power dissipated on the thyristor 20, because the voltage drop created on the switching element 1, not only depends on the current, because the resistor 24 is connected

in series with the thyristor 20, but also depends on the voltage, since the additional current, which is a function of the voltage, flows through the resistor 24 with

resistors 25 and 26. Without resistors 25 and 26, current 1 will remain constant and equal to maximum current 12, as shown by the current-voltage characteristic part 42 in FIG. 4. In this case, the power dissipated in the switching element 1,

may become redundant as part 42 crosses the maximum power dissipation line 43 of cell 1. Based on this, the I – V characteristic part 41 should not cross the load line 38. On the other hand, since the minimum power dissipated from the switching element 1 occurs at the operating point of this element, i.e. at the point of intersection of the IVC portion 40 and the load line 38, the IVC portion 41 should

be chosen as close as possible in the load line 38 in order to obtain the minimum power dissipation in the switching element 1. Therefore, the slope of the I – V characteristic part 41 is chosen similar to the slope of the line 38

load. This slope is a function of the ratio R25 / R26. Indeed, when the transistor 28 begins to conduct, its loss of UBE saturation at the base-emitter junction can be determined as follows

expression:

(U - R24 l) / (R24 + R-26 + R25) (UBE - R24 0 / (R24 + R26).

where U and I are the voltage on the switching element 1 and the current flowing through it. it

expression immediately leads to I R24 -R25

(R2A + R26 + R25) - (R24 + R26) in accordance with

resistance values, 6 Ohms, R29

-500 Ohm, kOhm, kOhm, maybe:

an assumption is made that R25

 R26 R24, then the final expression is I R24 R25 UBE R25 - U R26, so

l () - (l / R24).

From this expression it follows that the current

depends on voltage U (R26 / R2s).

Since the I – V characteristic part 41 is selected as close as possible to the load line 38 with: in order to limit the power dissipation on the switching element 1, the maximum current 2 should be chosen a little more than li, and the maximum voltage Ua should be chosen a little more than UL In this example, HsIOO mA, a IJ2 100 V. However, in

in accordance with the requirements for telecommunication systems, the protection circuit must operate for a current exceeding 300 mA. -If, on the basis of this, i is selected more than 300 mA, part 41 of the I – V characteristic must be shifted up and

a portion may be located above the line to maximize power dissipation. In this case, when the power protection means are turned on, the power dissipated on the element 1 may be so large that the latter fails.

The disadvantages of both power protection devices, considered separately, can be eliminated by combining these two tools, this combination giving the entire IVC of the switching element 1 shown in FIG. 5. On this CVC there is part 36 and partly part 37 related to the second power protection device, as well as part 41 of the CVC related to the first power protection device. From this graph it is clearly seen that the I – V characteristic crosses the load line 38 at a single stable operating point 39 and that the power dissipated on the switching element 1 is reduced to a minimum since part 41 is very close to the load line 38.

Claims (8)

1. A device for creating a high or low impedance between two output terminals, comprising a first switching element and a control unit, the outputs of which are the third and fourth terminals, characterized in that, in order to provide regulation of the voltage of the opposite voltage, a second switching element is introduced , the switching elements are made similarly and are connected counter-parallel, and the control unit is connected between two output terminals, each switching element contains a thyristor with two control electrodes and two diffuse MOS transistors, the first and second thyristor power leads connected to the first and second output terminals, respectively, the first thyristor control electrode connected to the drain of the first MOS transistor, the second control electrode to the source of the second MOS transistor the gates of which are combined and connected to the fourth terminal, and the source of the first and drain of the second MOS transistor are connected to the second output terminal to form a capacitance between the second output terminal and the fourth terminal. 2. Device pop 1, characterized in that the control unit contains the third and fourth MOSFETs of the p-channel type, while the sources of each MOSFET are connected to the third terminal, the drain of the third and the gate of the fourth MOSFET are connected to first output terminal, fourth drain and shutter a third MOSFET is connected to a second output terminal. 3. The device according to claim 1, characterized in that each switching element comprises first power limiting means made on the first and second sensing elements, the first decoupling element and the first regulating element. 0 4. The device according to claim 3, with the proviso that the first sensor is made in the first resistor, the second sensor is made of at least the second and third resistors, which are connected in series, the first the decoupling element is made on the fifth n-channel type MOS transistor and ensures that the first power limiting means is switched off only after the thyristor is installed with a high impedance, the first control element is made on the first npn transistor and provides a gradual decrease in ohod discharged through the thyristor current during raising 5 voltage on it, 5. The device according to claim 1, characterized in that each switching element comprises second power limiting means made on the third 0 sensing element, diode, second decoupling element and second and third control elements. 6. The device according to p. 5, with the exception that the third sensitive element 5 is made on the fourth resistor, the second decoupling element is made on the sixth l-channel type MOS transistor and ensures that the second power limiting means is switched off only after the thyristor is installed with a high impedance, the second and third control elements are made on the second and third p-p -transistors, the second regulating element reduces the current passing through the thyristor 5 at a high speed until the voltage across the thyristor exceeds a predetermined value. 7. The device according to claim t, characterized in that each switching element co0 contains a control element made on a diffusion MOS transistor and enabling the first and second power limiting means to turn on and off after the short-circuit thyristor sets a high impedance. 8. The device according to paragraphs 3-7, characterized in that the first output terminal is connected to the base of the second pnp transistor via a cascade connection of the diode, a collector-emitter junction of the third npn transistor, and of the fourth resistor, the collector of the second pn pn transistor is connected to the second control electrode of the thyristor, and the emitter is connected to the second output terminal, the cathode of the diode is connected to the additional output of the thyristor through the serial connection of the second resistor, the drain-source transition of the fifth MOSFET and the third resistor, an additional output of the thyristor is connected to the second power output of the same thyristor through the first resistor, the connection point of the third resistor and the source of the fifth MOS transistor is connected to the base the first npn transistor, the collector of which is connected to the first thyristor control electrode and the emitter to the second output terminal, the diode cathode is also connected to the drain of the sixth MOS transistor, the source of which is connected to the base of the third npn transistor, which is connected to the detector output terminal , gates of the first and sixth MOS transistors connected to the drain of the diffusion MOS transistor, the source of which is connected to the fourth terminal, and the gate to the second output terminal. about lvs to VLҐм Voltage V FIG. t VLCh Voltage V 8 Figure 5 I2 V Voltage V