SU621095A1 - Switching apparatus - Google Patents

Description

The invention relates to automation and can be used in switching equipment to control the voltage of a direct current applied to an active-inductive load, such as an electric motor and other devices.

Known switching devices in series-connected transistors with a parallel IJ load connected in parallel with one of them.

The disadvantages of these devices are the presence of through currents that occur during the transition period of switching transistors, and low reliability.

The purpose of the invention is to eliminate through currents and increase reliability.

The goal is achieved by the fact that current sensors, switches and a duration modulator, whose input is connected to the control bus, and the outputs are introduced into the switch containing the series-connected power transistors, diodes and loads connected between the collector and the emitter of one of the power trb resistors.

The keys are connected to the base of the corresponding power transistors, the collector-emitter junction of each of which is shunted by a series-connected diode and current sensor, and the other outputs of the current sensors are connected to other key inputs.

The drawing shows the block diagram of the switch. .

 contains power transistors 1 and 2, which are interconnected in series and the output terminals are connected to a power source. To the collector and the emitter of the transistor 2 is connected to the active-inductive load 3, for example, the measles of the engine. The load is shunted by a chain consisting of a series-connected reverse diode 4 and a current sensor 5. Parallel to the power transistor 1, a circuit is connected, consisting of a series-connected reverse circuit diode 6 and current sensor 7. The first output of the modulator 8 duration is connected via key 9 to the base of the power transistor 1. The second output of the modulator 8

the duration is connected via the switch Yus by the base of the power transistor 2. The control pulses produced by the modulator 8 of the duration on the first and second output are in antiphase. The output of current sensor 5 is connected to the control input of the switch 10. The output of the current sensor 7 is connected to the control input of the switch 9.

The switch works as follows.

When a control signal Uy is applied to the modulator 8 input, its output (9x a pulse of duration proportional to the control signal appears. The control pulses generated at the first and second outputs of the duration modulator 8 are in antiphase and provide alternating switching of power transistors 1 and 2. Consider the motorized mode of operation when the source draws current when the transistor 1 is opened and the load current closes through diode 4 when the transistor 1 closes.

Let transistor 1 open and transistor 2 closed. : Load 3 will be connected to a power source. Reverse diodes 4 and 6 are closed. The output signal from the sensors 5 and 7 is missing. Keys 9 and 1O are open. Therefore, a control pulse passes to the base of transistor 1, and there is no signal at the base of transistor 2. This state of the circuit lasts until the modulator 8 is switched over and at its first output the amplitude of the control pulse becomes zero. Transistor 1 will close and immediately under the action of the EMF of self-induction of load 3, diode 4 will open and current will flow through current sensor 5. The signal from the output of current sensor 5 will close the key 1O and will not permit the supply of a gate pulse from the output of the modulator 8 of duration to the base of transistor 2. Transistor 2 will remain closed during this time interval.

When switching to braking mode, the distribution of currents in the circuit changes. The braking mode starts from the moment when the load current flowing through diode 4 drops to zero during the period in which transistor 1 is closed. With this, the OUTPUT signal of the current sensor 5 becomes zero and the key 10 is opened. The control pulse, which during this period of time comes from the output of the modulator 8 of duration, hits the base of transistor 2 and opens it. Under the action of self-induction EMF, the braking current flows through the transistor 2. Upon subsequent switching, transistor 2 closes and transistor 1 must open. But when the transistor 2 is closed, under the action of the EMF of self-induction of the load 3, the reverse diode 6 opens and at the output of the current sensor 7 a signal that closes the key 9 and does not miss the trigger pulse to the base of the transistor 1, the transistor 1 will remain closed for the entire duration.

switching terval. With the arrival of the next trigger pulse to the base of transistor 2, the latter opens and the dynamic braking current flows through it again. Diode 6 at this moment

is closed, the signal at the output of current sensor 7 becomes zero, key 9 is opened. However, the transistor 1 remains closed, since by this time the triggering pulse at the output of the modulator 8

the duration will become zero.

Thus, as a result of the effect of the signals from the current sensors 5 and 7 on the control inputs of the keys 10 and 9, the power transistors 1, 2 turn on only

in cases where this is required depending on the mode of operation.

The switch eliminates the alternate switching of transistors 1 and 2, due to the presence of additional circuits from current sensors 5, 7, and additional switches 9, 1О. This leads to the elimination of through currents through transistors and increase the reliability of the device.

Claims (1)

1. Konev, Yu.N. Transistor Pulse Device Controls for Electric Motors and Electromagnetic Mechanisms, ed. Energy, 1964, p. 32-33.  -Ik . - V L -0