RU2156997C1 - Method for controlling saturation of transistor gate - Google Patents

Abstract

FIELD: power transistor gates using bipolar transistors. SUBSTANCE: method involves application and regulation of current from power supply units of power circuit and control circuit of transistor gate. Simultaneously with application of direct current to control circuit, method involves regulated application of alternating current to control circuit using minimal possible amplitude to provide reliable detection of this constituent in background noise. Then, method involves measurement of total alternating current constituents in control circuit and power circuit of transistor gate, and comparison of their ratio to reference value, which is equal to ratio of voltage levels of power supply units in power circuit and control circuit. Saturation mode is detected by result. This results in on-line monitoring of shift of working mode of transistor gate in gate or active mode outside of point, which is defined as boundary between gate and active modes, so that even short-term exit of power transistor gate within active mode out of saturation is detected. EFFECT: increased functional capabilities. 1 dwg

Description

 The invention relates to measuring equipment and is intended to control the saturation of the transistor switch - the main element in the development of high-performance power non-contact protective and switching equipment. The proposed solution can also be used when studying and taking into account the influence of various influencing factors, for example, radiation from outer space, on equipment containing transistors operating in the key mode.

 Known methods for controlling the saturation mode of the transistor switch, which include supplying currents from the corresponding power sources to the power circuit and the control circuit of the transistor switch, changing the current in the power circuit so that the transistor is in key mode and goes into active mode, and a sharp increase in the drop key voltages judge the boundary between the key mode and the active mode. This method is widely described in the literature, in relevant textbooks and teaching aids, for example: O.A. Kossov "Power amplifiers on transistors in switching mode" Energy, M., 1971 on pp. 31-32.

 The disadvantage of this method is the use of an indirect parameter (the value of the voltage drop across the transistor key) to control the saturation mode of the transistor switch. Using an indirect parameter does not allow for high accuracy control. It should be noted that the key mode of operation of transistors is the main mode of operation of transistors in protective switching equipment. Information on ensuring the saturation mode of the transistor switch, as well as confirmation of the implementation of this mode in a wide range of temperatures, supply voltages, exposure to penetrating radiation, etc. extremely necessary for developers of equipment and quality control of products.

 Information of this nature often needs to be obtained experimentally, especially when confirming the reserves on the performance of electronic equipment in extreme conditions during various tests.

 A method for monitoring the saturation mode of a transistor switch, based on the supply and regulation of currents from power sources of the power circuit and the control circuit of the transistor switch, measuring currents in the power circuit and control circuit, measuring voltages in the power circuit and control circuit, determining the ratio of currents and comparing the result with reference value avoids this drawback. The reference value each time is the result of a previous measurement. As a result, the method allows successive approximations to determine the control point when the sum of the power dissipated in the power circuit and the control circuit of the transistor switch reaches a minimum. This method, adopted by the authors as a prototype, allows you to control the gain of the transistor in the key mode, the ratio of the control current to the load current and, accordingly, control the saturation mode of the transistor switch. A description of the method is given and described in detail in the collection "Electronic Engineering in Automation" 15, ed. Yu.I. Koneva, M., Energy, 1984 in an article by G.M. Vedeneeva et al. "Transistor current transfer coefficient in saturation mode". The method allows to determine the ratio of the control current and the load current of the transistor switch, in which the saturation mode of the transistor switch is provided. Due to the fact that the control is carried out taking into account a number of parameters that make it possible to directly judge the saturation mode of the transistor switch, the method proposed in the article is significantly more accurate, since it is not influenced by factors such as changes in the characteristics of power transistors, ambient temperature, etc. .

 The disadvantage of this control method is its low efficiency, since it is necessary to measure currents and voltages in the power circuit and in the control circuit of the transistor, to determine the power dissipated in these circuits, the total power dissipated on the key. Comparison of the obtained value with the reference value, which is the result of the previous measurement, which also requires the memorization operation, and the current in the input circuit of the transistor is regulated to the level when the power dissipated by the transistor is at a minimum value, is performed repeatedly, which leads to a low efficiency of the method. It should also be noted that when monitoring the saturation mode of a transistor switch as part of automatic systems, where the control current is generated automatically, according to an internal algorithm, using this method becomes difficult or even impossible. The method is convenient for laboratory research and experiments, but when monitoring the saturation mode of the transistor switch in the factory, where high performance is required, the method is not applicable.

 The technical result of the present invention is to increase the efficiency of the control process.

 The specified technical result is achieved by the fact that in the method of controlling the saturation mode of the transistor switch, based on the supply and regulation of currents from power sources of the power circuit and the control circuit of the transistor switch, determining the ratio of currents and comparing the result with a reference value, in contrast to the known circuit control, along with the supply of direct current, produce controlled supply of alternating current with an amplitude not exceeding the level of direct current, measure the ratio of the variable components of current in the control circuit and the power circuit in the controlled current range of the transistor switch of the main circuit is compared with a reference value, equal to the ratio of sources of voltage in the power supply and control circuits, and the result obtained by judging the security saturation regime.

 The drawing shows an electrical diagram of the installation that implements the proposed method. For comparison with the prototype, a setup diagram is also provided for manual measurements.

In the drawing are indicated:
1 - power supply control circuit,
2 - diode,
3 - controller (resistor), providing current control in the control circuit of the transistor switch,
4 - transistor,
5 - sensor sum of the currents of the power circuit and the control circuit,
6 - electric load of the transistor switch,
7 - ammeter for measuring the current consumed from source 7 in the load circuit,
8 - power supply circuit
9 - capacitor
10 - resistor
11 - variable resistor,
12 - source of alternating voltage with high output resistance,
13 - AC sensor in the control circuit,
14 - capacitor
15 is a capacitor
16 - operational amplifier (comparator),
17 - voltmeter.

 The transistor switch consists of the following elements connected in series along the control circuit: power supply of control circuit 1, diode 2, regulator 3 (variable resistor), which provides current control in the control circuit of the transistor switch, power transistor 4 and current sensor in power circuit 5. In the drawing these elements are circled by a dotted line.

 The power circuit of the transistor switch (transistor 4 and current sensor 5) is included in the load current circuit, where the following are connected in series: load of the transistor switch 6, ammeter 7, power supply of the power circuit 8.

 The AC voltage generating circuit is assembled on a series-connected: current sensor 13, alternating voltage generator 12, resistors 10 and 11 connected in parallel, a capacitor 9. The output of the AC sensor of the control circuit 13 through a capacitor 15 is connected to one input of the operational amplifier, and the output of the current sum sensor the power circuit and the control circuit is connected to another input of the operational amplifier 16. The output of the operational amplifier 16 through a voltmeter 17 is connected to the output of the generator 12.

 The scheme shown in the drawing, in order to simplify it, does not contain a number of secondary elements that are not related to explaining the principles of the method, for example, operational amplifier power supplies, various elements that correct the operation of the operational amplifier, various filters in the power supply circuits. Elements necessary for ensuring the stable operation of the comparator on an operational amplifier, and their connection schemes are given in the corresponding reference literature on the types of microcircuits used.

 Monitoring the saturation mode of the transistor switch is as follows. From the voltage source 1 with a voltage value of E1, a current is supplied to the control circuit of transistor 4 through a diode 2 and a regulator (variable resistor 3). The current value is regulated by a resistor 3. (The control current value is determined by the internal circuit of the transistor switch and is regulated by the internal control algorithms of the transistor switch In the drawing, the control current regulator is shown schematically in the form of an adjustable resistance 3. The operator who performs the control does not interfere with the formation of the control current. d from the power source of the power circuit 8 with a voltage value of E2, during the flow of which the saturation mode of the transistor switch is controlled, is set by choosing the value of the resistor 6 and is controlled by ammeter 7. Resistor 5 is a current sensor in the power circuit of the transistor switch.

 The source of alternating voltage 12 provides the supply to the control circuit of the transistor switch of an alternating current 100 times or less than the amount of current consumed from source 1. It should be noted that, for example, an increase in the amplitude of oscillations of alternating current more than the amplitude supplied to the control circuit of direct current from source 1 can cause the transistor switch to lock at some points in time, which leads not only to the impossibility of monitoring, but also to disrupt the normal operation of the transistor switch. In addition, the increase in the amplitude of the current consumed from the AC voltage source 12, leads to a corresponding increase in power consumption from this source, the appearance of a high level of interference in the load circuit of the transistor switch. The lower limit of the amplitude of the supplied alternating current is determined by the noise level of the transistor, against which it is still possible to reliably isolate the variable component.

 Coarse regulation of the magnitude of the alternating current supplied to the control circuit of the transistor switch is carried out in parallel by connected resistors 10 and 11. Further regulation of the variable component of the control current during the monitoring is carried out by regulator 3. The control law, which is executed by regulator 3, in this case, does not have significant values, since it will affect both the variable and the constant component of the control current.

 In the most general case, the role of the control current regulator 3 in the transistor key can be performed by various types of current regulators that perform the function of regulating the control current by the load current in the power circuit of the transistor switch, for example, by the voltage drop across the power electrodes of the transistor switch or based on a different principle. Monitoring of the saturation mode of the transistor switch is reduced to confirming that the necessary saturation of the latter is provided in the entire required range of load currents of the transistor switch.

 Thus, in the control circuit, in addition to supplying direct current, an adjustable supply of alternating current is produced with an amplitude not exceeding the level of direct current.

 The operational amplifier 16 compares the alternating voltage components induced by the currents in the control circuit and the power circuit on the resistors 13 and 5. The capacitors 14 and 15 serve as a filter for the alternating voltage components.

 The resistor 6 provide the installation of the required load current, at which it is necessary to control the saturation mode of the transistor switch. In the general case, a load rheostat can be used as resistor 6, which allows changing the load current within specified limits, which ensures monitoring not only at a fixed load of the transistor switch, as in the case of using a constant wire resistor, but also in the entire range of permissible current loads transistor key.

 Monitoring the saturation mode of the transistor switch is as follows. The power circuit of the transistor switch through the load 6, the ammeter 7 is connected to a voltage source 8 in accordance with the drawing. In the control circuit of the transistor switch produce an alternating current with an amplitude less than the amplitude of the direct current. Initial adjustment of the amplitude of the alternating current is carried out by potentiometer 11 and a constant resistor 10. In this case, the currents from two sources are mixed: voltage source 1 and alternating voltage source 12. Further regulation of the current in the control circuit is carried out by the internal current regulator of the transistor switch. An increase or decrease in the DC component of the current leads, respectively, to synchronous regulation and the variable component of the current.

 The alternating components of the currents in the control circuit and the power circuit of the transistor switch cause corresponding voltage drops on the current sensors 5 and 13. Capacitors 14 and 15 filter the variable components of the voltages that are fed to the inputs of the operational amplifier 16 of the current detectors.

 The moment of transition through the optimum saturation point is controlled by a voltmeter 17, which occurs when the ratio of the alternating current components in the power circuit and the control circuit is equal to the ratio of the voltage of the power sources. In this case, if the magnitude of the alternating voltage incident on the current sensor in the power circuit 5 is greater than the magnitude of the alternating voltage incident on the current sensor in the control circuit 13, then the output voltage of the operational amplifier 16 will have the same phase as the voltage of the generator 12. Therefore , the voltage indicated by the voltmeter 17 will have a minimum value close to zero. If the magnitude of the alternating voltage incident on the current sensor in the power circuit 5 is less than the magnitude of the alternating voltage incident on the current sensor in the control circuit 13, then the output voltage of the operational amplifier 16 will have a phase opposite to that of the voltage of the generator 12. Therefore, the voltage indicated by the voltmeter 17 will have a maximum value. With the amplitude of the generator voltage in the range 0 - 10 V and the output voltage of the operational amplifier ± 10 V, the voltmeter readings will be 0 and 20 V, respectively, which is sufficient for reliable reading of the readings.

 By changing the resistor 6 current in the load circuit and controlling the readings of the voltmeter 17, it is possible to control the saturation mode of the transistor switch in the entire allowable load range.

Using the proposed method assumes that the boundary of the optimal saturation mode of the transistor switch passes through the point where the power gain for the transistor switch becomes equal to one. If we denote by J _{y ~ the} increment of the control current, and by J _{n ~ the} corresponding increment of the load current caused by J _{y ~} , then the boundary point of the saturation mode of the transistor switch will be determined by the relation E1 • J _{y ~} = E2 • J _{n ~} , which corresponds to the mode where a change in the amount of power consumed by the control circuit leads to an equal increase in power in the load circuit. The shift of the operating point of the transistor switch by increasing the control current leads to the transition of the transistor to the key mode, where an increase in the control current does not cause a noticeable increase in the current in the load circuit. Accordingly, the shift of the operating point of the transistor switch by reducing the control current causes the transistor to go into active mode, where a small change in the control current leads to significant changes in the current in the load circuit.

The comparator made on the operational amplifier 16, allows you to determine the area in which the transistor switch operates (relative to the boundary of the optimal saturation mode of the transistor switch). Setting the comparator (by selecting the ratio of the resistance values of the current sensors 5 and 13) is based on the fact that the comparator is triggered when the ratio of current values:
J _{y ~} / J _{n ~} = E2 / E1, (1)
Denote E2 / E1 = k, then J _{y ~} / J _{n ~} = k.

 Since in this circuit the current sensor 5 is installed in the emitter circuit of the transistor on which the key is made, the alternating voltage on this current sensor is the sum of the voltage drops from the load currents and the control current.

Denote J _{y ~} + J _{n ~} = J _{5 ~} , where J _{5 ~} is the variable component of the current flowing through the current sensor 5. In this case, equation (1) is converted to J _{y ~} / (J _{5 ~} - J _{y ~} ) = k, whence J _{y ~} / J _{5 ~} = k / (k + 1), i.e. in this version of the control circuit, the fulfillment of condition (1) is achieved by setting a comparator that compares the alternating components of the currents flowing through the current sensors 13 and 5 in the ratio k / (k + 1), where k is the ratio of the voltage of the power sources of the power circuit and the control circuit. This setting of the comparator response level can be achieved by selecting the appropriate ratio of the resistance values of the current sensors 13 and 5.

The control result can be determined on the basis of voltmeter 17. If the output voltage of the voltmeter has a low output value over the entire range of load currents of the transistor switch, which is set by adjusting the load resistance, then the saturation degree of the transistor switch is sufficient, since J _{y ~} / J _{n ~} > E2 / E1. The control process can be easily automated, because to detect the fact that the transistor switch is not saturated enough, it is enough to reveal only the presence of a high voltage level at the output of the comparator in the entire range of load currents of the transistor switch or in any part of this range.

 Thus, the proposed method provides a higher efficiency of the control process compared to the prototype, because instead of a large number of operations (measuring the current and voltage of the transistor control circuit, determining the power dissipated in the input circuit of the transistor, measuring the current and voltage in the power circuit of the transistor, determining the power dissipated in the power circuit of the transistor, the addition of the values of these powers and the regulation of the current supplied to the control circuit to the value when the specified sum of powers udet have a minimum value that requires multiple measurements and memorizing the results) using a minimal number of simple operations (flow and adjusting the AC control circuit and comparing the ratio of the variable components of the current in the control circuit and load circuit with a reference value, predetermined). This feature allows you to provide control of power transistor switches in the process of their production in real time, in contrast to the existing method. The simplicity of the method operations and their sequence allows you to automate the control process, providing control of transistor switches in the process of their production.

 In addition, the simplification of the hardware implementation of the method allows to reduce the cost of measuring equipment, reduce the cost of commissioning and maintenance of equipment, requires less qualified personnel.

Claims (1)

 A method for monitoring the saturation mode of a transistor switch, based on the supply and regulation of currents from power sources of the power circuit and the control circuit of the transistor switch, determining the ratio of currents, and comparing the result with a reference value, characterized in that the control circuit, in addition to supplying direct current, produce a controlled supply of alternating current with an amplitude not exceeding the level of direct current; measure the ratio of the alternating components of the currents in the control circuit and the power circuit in roliruemom current range of the transistor switch of the main circuit is compared with a reference value, equal to the ratio of sources of voltage in the power supply and control circuits, and the result obtained by judging the security saturation regime.