SU1275635A1

SU1275635A1 - Device for overload protection of voltage converter

Info

Publication number: SU1275635A1
Application number: SU843807594A
Authority: SU
Inventors: Иван Иванович Филиппов
Original assignee: Предприятие П/Я А-1811
Priority date: 1984-11-01
Filing date: 1984-11-01
Publication date: 1986-12-07

Abstract

Изобретение относитс к электротехнике и может бь1ть использовано в преобразовател х посто нного напр жени , включающих транзисторный 4- инвертор. Целью изобретени вл етс упрощение устройства дл защиты от перегрузок преобразовател напр жени . В инверторе 1, снабженном управл ющим трансформатором 10 тока, ток вторичных обмоток 11 и 12 трансформатора 10 тока пропорционален току в силовых цеп х транзисторов 2 и 3. Падение напр жени на резисторе 13, включенном между общей точкой вторичных обмоток 11 и 12 и общей шиной, также пропорционально току нагрузки 5 и используетс дл приведени в действие защиты. Устройство упрощаетс за счет исключени датчика тока из силовой цепи. 2 ил. (Л иг.1The invention relates to electrical engineering and can be used in constant voltage converters, including transistor 4-inverter. The aim of the invention is to simplify an overvoltage protection device of a voltage converter. In the inverter 1, equipped with a control current transformer 10, the current of the secondary windings 11 and 12 of the current transformer 10 is proportional to the current in the power circuits of transistors 2 and 3. The voltage drop across the resistor 13 connected between the common point of the secondary windings 11 and 12 and the common bus It is also proportional to the load current 5 and is used to activate the protection. The device is simplified by eliminating the current sensor from the main circuit. 2 Il. (L ig.1

Description

Изобретение относится к электротехнике и может быть использовано в преобразователях постоянного напряжения, включающих транзисторный инвертор. 5The invention relates to electrical engineering and can be used in DC voltage converters, including a transistor inverter. 5

Цель изобретения - упрощение устройства для защиты от перегрузок преобразователя напряжения.The purpose of the invention is the simplification of the device for protection against overload of the voltage Converter.

На фиг. 1 приведена схема преобразователя с устройством для защиты; на фиг. 2 - временные диаграммы, поясняющие его работу (индексы при переменных соответствуют номеру элемента на фиг. 1).In FIG. 1 shows a diagram of a converter with a protection device; in FIG. 2 - timing diagrams explaining its operation (indexes with variables correspond to the element number in Fig. 1).

На схеме (фиг. 1) изображен двухтактный инвертор 1, коллекторы силовых транзисторов 2 и 3 которого подключены к первичной обмотке выходного трансформатора 4. Вторичная обмотка трансформатора 4 подключена к нагрузке 5 через выпрямитель 6 и сглаживающий фильтр 7. Первичные обмотки 8 и 9 управляющего трансформатора 10 включены в силовые (эмиттерные) цепи транзисторов 2 и 3 инвертора 1. Две вторичные обмотки 11 и 12 этого трансформатора соединены последовательно и крайними выводами подключены к базам транзисторов 2 и 3, а точка соединения вторичных обмоток 11 и 12 подключена к общей шине питания через резистор 13 и через резистивный делитель 14 - к источнику 15 опорного напряжения. Средняя точка 16 делителя 14 подключена к входу порогового элемента 17, вход которого подключен через делитель 18 к источнику 15 опорного напряжения. Выход порогового элемента 17 подключен к входу блока 19 управления инвертора, второй вход которого подключен к выходу преобразователя. Выход блока 19 управления подключен к предварительному усилителю 20, выход которого подключен к обмотке 21 управления трансформатора 10. Выходом делителя 18 напряжения является точка 22.The diagram (Fig. 1) shows a push-pull inverter 1, the collectors of power transistors 2 and 3 of which are connected to the primary winding of the output transformer 4. The secondary winding of the transformer 4 is connected to the load 5 through a rectifier 6 and a smoothing filter 7. The primary windings 8 and 9 of the control transformer 10 are included in the power (emitter) circuit of transistors 2 and 3 of inverter 1. Two secondary windings 11 and 12 of this transformer are connected in series and extreme leads are connected to the bases of transistors 2 and 3, and the connection point of the secondary windings ok 11 and 12 connected to a common power bus through a resistor 13 and through a resistive divider 14 to a source of 15 reference voltage. The midpoint 16 of the divider 14 is connected to the input of the threshold element 17, the input of which is connected through the divider 18 to the source 15 of the reference voltage. The output of the threshold element 17 is connected to the input of the inverter control unit 19, the second input of which is connected to the output of the converter. The output of the control unit 19 is connected to a pre-amplifier 20, the output of which is connected to the control winding 21 of the transformer 10. The output of the voltage divider 18 is point 22.

Устройство работает следующим образом.The device operates as follows.

В нормальном режиме работы потенциал на выходе делителя 14 (потенциал точки 16) выше потенциала на выходе делителя 14 (потенциал точки 22 на всем интервале полупериода - Т/2 выходного напряжения инвертора 1, потенциал на выходе порогового элемента 17 соответствует сигналу 1 и не оказывает влияния на работу преобразователя . С появлением в момент времени t маломощного сигнала IJL на обмотках трансформатора 10 приоткрывается транзистор 3 (2), и по нему начинает протекать ток, под действием положительной обратной связи между обмотками 9 и 12 (8 и 11) происходит лавинообразный процесс открывания и насыщения транзистора 3 (2). По вто10 ричной обмотке 12 (11) и в базовой цепи транзистора 3 (2) протекает ток пропорциональный току в коллекторной цепи. Следовательно, падение напряжег ния на резисторе 13 в интервале вре15 мени также пропорционально току коллектора транзистора 3 (2). В момент времени транзистором предварительного усилителя 20 закорачивается управляющая обмотка 21, и на об20 мотках трансформатора 10 формируется.In normal operation, the potential at the output of the divider 14 (potential of point 16) is higher than the potential at the output of divider 14 (potential of point 22 over the entire half-period interval - T / 2 of the output voltage of inverter 1, the potential at the output of threshold element 17 corresponds to signal 1 and does not affect With the appearance of a low-power signal IJL at the time t of the transformer 10, the transistor 3 (2) opens, and a current begins to flow through it, under the influence of positive feedback between the windings 9 and 12 (8 and 11), It is an avalanche-like process of opening and saturation of the transistor 3 (2). A current proportional to the current in the collector circuit flows through the secondary winding 12 (11) and in the base circuit of the transistor 3 (2) .Therefore, the voltage drop across the resistor 13 in the time interval also proportional to the collector current of the transistor 3 (2) .At a time instant, the control winding 21 is shorted by the transistor of the pre-amplifier 20, and is formed on the windings of the transformer 10.

нулевая пауза. Под действием напряжения заряда базы транзистора 3 (2) происходит рассасывание его неосновных носителей на интервале времени 25 t_e~t током, определяемым величиной сопротивления резистора 13. По окончании процесса рассасывания, неосновных носителей на интервале времени t^-t^ закрыты оба транзистора 2 и 3.zero pause. Under the action of the charge voltage of the base of transistor 3 (2), its minority carriers are absorbed in the time interval 25 t _e ~ t by the current determined by the resistance value of resistor 13. At the end of the resorption process, minority carriers in the time interval t ^ -t ^ are closed both transistors 2 and 3.

В момент времени открывается транзистор 2 (3), и описанный процесс повторяется.At the time, the transistor 2 (3) opens, and the described process is repeated.

При перегрузках либо коротких замыканиях происходит возрастание тока, 35 проходящего через транзисторы инвертора 1. Пропорционально увеличивается и падение напряжения на резисторе 13 на интервалах проводимости транзисторов инвертора 1 и уменьшается потенциал точки 16. В момент времени t_g , когда, ток, протекающий через транзистор 3 (2), достигает значения уставки, потенциал точки 16 становится равным потенциалу пточки 45 22, и происходит срабатывание порогового элемента 17. Появившийся нулевой сигнал на выходе порогового элемента 17, воздействуя на блок 19 управления, снимает отпирающий сигнал ⁵⁰ с входа проводящего транзистора 3 (2) инвертора 1 до конца полупериода. По истечении времени рассасывания t_pctc проводящий транзистор 3 (2) инвертора 1 запирается, и ток в на55 грузке спадает до конца полупериода.During overloads or short circuits, an increase in the current passing through the transistors of the inverter 1 occurs. The voltage drop across the resistor 13 increases proportionally, and the potential of the point 16 decreases at the conduction intervals of the inverter 1. At the time t _g , when the current flowing through the transistor 3 (2), reaches the setpoint value, the potential of point 16 becomes equal to the potential of the point 45 22, and the threshold element 17 is triggered. A zero signal appears at the output of the threshold element 17, acting on and the control unit 19, removes the unlocking signal ⁵⁰ from the input of the conductive transistor 3 (2) of the inverter 1 to the end of the half-cycle. After the absorption time t _{pctc expires, the} conducting transistor 3 (2) of the inverter 1 is turned off, and the current in the load55 drops to the end of the half-cycle.

В начале следующего полупериода появляется отпирающий сигнал на управляющем входе другого транзистора ин1275635 вертора 1, и если перегрузка сохраняется, происходит повторное срабатывание порогового элемента.At the beginning of the next half-cycle, a turn-on signal appears on the control input of another transistor in1275635 of vertor 1, and if the overload persists, the threshold element re-operates.

Таким образом, производится ограничение тока проходящего через транзисторы инвертора 1 на максимально допустимом уровне.Thus, the current passing through the transistors of the inverter 1 is limited to the maximum permissible level.

Claims

The invention relates to electrical engineering and can be used in constant-voltage converters including a transistor inverter. The purpose of the invention is to simplify an overvoltage protection device of a voltage converter. FIG. 1 is a diagram of a converter with a device for protection; in fig. 2 - timing diagrams explaining his work (indexes for variables correspond to the element number in Fig. 1). The diagram (fig. 1) shows a 2n push-pull inverter 1, the collectors of power transistors 2 and 3 of which are connected to the primary winding of the output transformer 4. The secondary winding of transformer 4 is connected to the load 5 via rectifier 6 and a smoothing filter 7. Primary windings 8 and 9 of the control transformer 10 are included in the power circuits (emitter circuits of transistors 2 and 3 of inverter 1, the two secondary windings 11 and 12 of this transformer are connected in series with the outermost leads connected to the bases of transistors 2 and 3, and The windings 11 and 12 are connected to the common power bus through a resistor 13 and through a resistive divider 14 to the voltage source 15. The midpoint 1 of the divider 14 is connected to the input of the threshold element 17, the cat (which is connected via the divider 18 to the source 15 of the reference voltage. The output of the threshold element 17 is connected to the input of the inverter control unit 19, the second input of which is connected to the output of the converter. The output of the control unit 19 is connected to the pre-amplifier 20, the output of which is connected to the control winding 21 of the transformer 1 0. The output of voltage divider 18 is point 22. The device operates as follows. In normal operation, the potential at the output of the divider 14 (potential of point 16) is higher than the potential at the output of divider 14 (the potential of point 22 in the entire half-period is T / 2 of the output voltage of inverter 1, the potential at the output of the threshold element 17 corresponds to signal 1 and does not The appearance of a powerful signal U. at the time t on the windings of the transformer 10 opens the transistor 3 (2), and current begins to flow through it, under the action of positive feedback between the windings 9 and 12 (8 and 10 proi There is an avalanche-like process of opening and saturation of transistor 3 (2). A current proportional to the current in the collector circuit flows through the secondary winding 12 (11) and the base circuit of transistor 3 (2). Therefore, the voltage drop across the resistor 13 in the time interval is also proportional to the collector current of the transistor 3 (2). At the time point of the t-transistor of the preamplifier 20, the control winding 21 is shorted, and a zero pause is formed on the windings of the transformer 10. Under the action of the charging voltage of the base of the transistor 3 (2), its minority carriers are resorbed over the time interval .j by the SURFACE determined by the resistance value of resistor 13. After the pc1 absorption process is over. minor carriers in the time interval t, -t both transistors 2 and 3 are closed. At time t, transistor 2 (3) opens and the described process repeats. In case of overloads or short circuits, there is an increase in the current passing through the transistors of the inverter 1. The voltage across the resistor 13 is increased proportionally by the interval: the conductivity of the inverters 1 transistors and the potential of the point 16 decreases. At the time t, when the current flowing through the transistor 3 (2) reaches the value of the set point, the potential of the point 16 becomes equal to the potential of that 22, and the threshold element 17 triggers. The zero signal at the output of the threshold element 17 is activated, affecting the control unit 19 removes the unlocking signal from the input of the conducting transistor 3 (2) of the inverter 1 to the end of the half period. After the absorption time elapses, the conductive transistor 3 (2) of inverter 1 closes and the current in the load drops to the end of the half period. At the beginning of the next half-period, a unlocking signal appears at the control input of the other transistor of the inverter 1, and if the overload persists, the threshold element is triggered again. Thus, the current of the inverter 1 passing through the transistors is limited at the maximum allowable level. Claims An overvoltage protection device for a voltage converter including a push-pull transistor inverter with a control current transformer, the two primary windings of which are included in the power circuits of the corresponding inverter transistors, two secondary windings are connected in series and connected between the bases of the inverter transistors, and an inverter control unit containing a voltage source, the worm is the first resistive voltage divider connected to the first input of the threshold element, the output The purpose of which is to connect to the input of the inverter control unit, characterized in that, in order to simplify the device, a second resistive voltage divider and a resistor connected between the common power bus of the inverter and combined with the outputs of the secondary windings of the control current transformer are connected to one from the extreme terminals of the second resistive voltage divider, the other extreme pin connected to the source of the reference voltage, and the other pin to the second input of the threshold element.