RU185925U1 - Reversible transistor bridge - Google Patents

Abstract

The reversible transistor bridge is intended for use as an electrical switching device, namely a device that changes the direction of the current through the load. Conductivity npn transistors connected by emitters and connected to the minus of the constant power supply voltage are used as two of the four transistors of the reverse transistor bridge. The pn-p conductivity transistors connected by emitters and connected to the plus of a constant power supply voltage are used as two other transistors of a reversible transistor bridge. The collectors of transistors of opposite conductivity are combined in pairs, with one pair connected to the first input of the load, and the other pair connected to the second input of the load. The base of the transistors npn conduction through the resistance is connected to the minus of the constant power supply voltage for reliable locking transistors npn conduction. The base of transistors pn-p conduction through the resistance is connected to the plus of the constant power supply voltage for reliable locking transistors pn-p conduction. The bases of transistors of different conductivity opposite the diagonal are connected by means of optocouplers to open the corresponding transistors. The design of the device is greatly simplified by the introduction of chains containing two optocouplers, in the absence of independent isolated DC power supplies in the transistor control system, while increasing reliability while eliminating the risk of short circuit.

Description

The proposed utility model relates to electrical switching devices, and in particular to devices implementing a change in the direction of the current through the load.

A device for performing reverse switching is known, which comprises, as switching elements, mechanical keys coupled to each other through a load and connected to a constant voltage source. The first input of the first key and the first input of the second key of the device are interconnected, and through an inductance are connected to a constant voltage source. The second input of the first key and the first input of the third key are interconnected and connected to the first input of the load. The second input of the second key and the first input of the fourth key are interconnected and connected to the second input of the load. The second input of the third key and the second input of the fourth key are interconnected and connected to a constant voltage source. Mechanical switching occurs by periodic mechanical closing and opening of contact groups to change the polarity of the voltage supplied to the load. Thus, the current in the load flows in the required direction (Rozanov Yu.K. Power Electronics: a textbook for high schools / Yu.K. Rozanov, M.V. Ryabchitsky, A.A. Kvasnyuk. - 2nd ed., Stereotyped. - M .: Publishing House MPEI, 2009. - S. 347, Fig. 7.1.a).

However, the described device has the following disadvantages caused by mechanical closure and opening of the contact group: low reliability, low speed during switching, increased dimensions and the appearance of an electric arc during closing and opening of contacts.

The closest to the proposed model in terms of technical nature and the achieved result (prototype) is a reversible transistor bridge containing four transistors of the same conductivity, namely, n-p-n conductivity, which requires four isolated DC sources to control the base circuit. All transistors are connected to the load. Changing the direction of the current in the load occurs by switching on the corresponding group of transistors. The collectors of the first and third transistors are combined and connected to the plus of the constant power supply voltage and the cathodes of the first and third diodes, respectively. The emitters of the second and fourth transistors are combined and connected to the minus of the constant power supply voltage and to the anodes of the second and fourth diodes, respectively. The emitter of the first transistor and the collector of the fourth transistor are combined and connected to the first input of the load, as well as to the anode of the first diode and the cathode of the fourth diode. The emitter of the third transistor and the collector of the second transistor are combined and connected to the second input of the load, as well as to the anode of the third diode and the cathode of the second diode (Gelman M.V. Conversion technique: training manual / M.V. Gelman, M.M. Dudkin, KA Preobrazhensky. - Chelyabinsk: Publishing Center of SUSU, 2009. - P. 211, Figure 10.12).

However, this device has a complex bulky design due to the need for four independent isolated DC sources in the switching transistor control system and reduced reliability due to a possible increase in the risk of a short circuit between the isolated transistor control power supply sources and the power part of the reverse transistor bridge.

The technical problem that can be solved by implementing the utility model is to create a reversible transistor bridge with a simplified compact design by ensuring the absence of the use of independent isolated DC power supplies in the transistor control system with increased reliability eliminating the risk of short circuit.

The solution to this technical problem is achieved by the fact that in a reverse transistor bridge containing four transistors, two of which are npn conductivity transistors connected by emitters and connected to the negative of the constant power supply voltage, while the transistors are connected to the load, according to the utility model, as two other transistors reverse transistor bridge used transistors pnp conductivity connected by emitters and connected to the plus of a constant power pi ayuschego voltage. In this case, the collectors of the transistors of the opposite conductivity are combined in pairs, with one pair connected to the first input of the load, and the other couple connected to the second input of the load. The base of transistors of n-pn conductivity through resistors is connected to the minus of a constant power supply voltage for reliable locking of transistors of npn conductivity. The base of pnp transistors through resistors is connected to the plus of the constant power supply voltage for reliable locking of pnp transistors. The bases of transistors of different conductivity opposite the diagonal are connected by means of optocouplers to open the corresponding transistors.

The simplification and the corresponding compactness of the structure with its increased reliability are due to the introduction of chains containing two optocouplers, in the absence of the use of four isolated DC sources in the base-emitter circuit.

The proposed utility model is illustrated in the drawing, where in FIG. 1 shows a diagram of a reverse transistor bridge; in FIG. 2 schematically shows the operation of a reversible transistor bridge.

In addition, the following notation is used in the drawing:

- VT1, VT3 - transistors rnp conductivity;

- VT2, VT4 - transistors n-pn conductivity;

- Rl, R2, R3, R4 - resistance;

- Rn is the load resistance;

- VD1, VD2 - optocouplers;

- “-” - minus constant power voltage;

- “+” - plus constant power voltage;

- a straight line with an arrow shows the direction of the current forward in the load;

- a discrete line with an arrow shows the direction of the current backward in the load.

The reverse transistor bridge contains two transistors of n-pn conductivity, the emitters of which are combined and connected to the minus of the constant power supply voltage and two transistors of pnp conductivity, the emitters of which are combined and connected to the plus of the constant power supply voltage. The collectors of the transistors of the opposite conductivity are combined in pairs, with one pair of transistors of the opposite conductivity connected to the first input of the load, and the other pair of transistors of the opposite conductivity connected to the second input of the load. The base of transistors of n-pn conductivity through resistors is connected to the minus of a constant power supply voltage for reliable locking of transistors of npn conductivity. The base of the transistors pnp conductivity through the resistance connected to the plus of the power supply voltage for reliable locking transistors pnp conductivity. Bases of diagonally opposite transistors of different conductivity are connected via optocouplers to open the corresponding transistors.

An example of a reverse transistor bridge is shown in figure 1. The reverse transistor bridge contains four transistors: transistor 1 (VT1) pnp conductivity and transistor 2 (VT3) pnp conductivity, connected by emitters and connected to the plus of the constant power supply voltage transistor 3 (VT2) npn conductivity and transistor 4 (VT4) npn conductivity connected by emitters and connected to the negative of the constant power supply voltage.

The base of the transistor 3 (VT2) n-pn conductivity and the base of the transistor 4 (VT4) n-pn conductivity through resistance 5 (R2) and resistance 6 (R4) are respectively connected to the minus of the constant power supply voltage for reliable locking of transistors n pn conductivity. The base of the transistor 1 (VT1) conductivity rnp and the base of the transistor 2 (VT3) conductivity rn p through resistance 7 (R1) and resistance 8 (R3) are respectively connected to the plus of the constant power supply voltage for reliable locking of the transistors p -n-p conductivity.

The bases located opposite the diagonal of the transistor 3 (VT2) n-pn conductivity and the transistor 2 (VT3) pnp conductivity are connected through an optocouple 9 (VD1). The bases located opposite the diagonal of the transistor 4 (VT4) n-pn conductivity and the transistor 1 (VT1) p-np conductivity are connected through an optocouple 10 (VD2).

The collectors of transistor 2 (VT3) pnp conductivity and transistor 4 (VT4) npn conductivity are combined and connected to the first input 11 of the load 12 (Rn). The collectors of transistor 1 (VT1) pnp conductivity and transistor 3 (VT2) npn conductivity are combined and connected to the second output 13 of the load 12 (Rn).

The reverse transistor bridge is as follows.

For the current to pass through the load resistance in the forward direction indicated by the solid arrow in FIG. 1, at time t1 (FIG. 2), a signal is supplied to the optocoupler 9 (VD1). Current begins to flow along the path: plus a constant power supply voltage, emitter of transistor 2 (VT3), base of transistor 2 (VT3), optocoupler 9 (VD1), base of transistor 3 (VT2), emitter of transistor 3 (VT2), minus constant power supply voltage, which leads to the opening of transistors 3 (VT2), 2 (VT3). Since transistors 3 (VT2) and 2 (VT3) are open, the current flows in the following direction through load 12 (Rn): plus a constant power supply voltage, emitter of transistor 2 (VT3), collector of transistor 2 (VT3), load 12 (Rn ), the emitter of transistor 3 (VT2), the collector of transistor 3 (VT2), minus the constant power supply voltage. At time t2, the control signal to the optocoupler 9 (VD1) ceases to be applied and transistors 3 (VT2) and 2 (VT3) are closed. To pass the current backward through the load 12 (Rn), indicated by the dashed arrow (Fig. 1), at time t3 a signal is applied to the optocoupler 10 (VD2). Current begins to flow along the path: plus a constant power supply voltage, emitter of transistor 1 (VT1), base of transistor 1 (VT1), optocoupler 10 (VD2), base of transistor 4 (VT4), emitter of transistor 4 (VT4), minus constant power supply voltage, which leads to the opening of transistors 1 (VT1), 4 (VT4). Since transistors 1 (VT1) and 4 (VT4) are open, the current flows along the following path: plus a constant power supply voltage, emitter of transistor 1 (VT1), collector of transistor 1 (VT1), input 11 of load 12 (Rn), load 12 (Rn), emitter of transistor 4 (VT4), collector of transistor 4 (VT4), minus DC power supply voltage. At time t4, the control signal to the optocoupler 10 (VD2) ceases to be applied, and transistors 1 (VT1) and 4 (VT4) are closed.

Thus, the proposed reversible transistor bridge has an advantage over the reversed transistor bridge, selected as a prototype, which consists in simplifying and ensuring appropriate design compactness by replacing four isolated power sources in the base-emitter circuit with chains containing optocouplers, eliminating the risk of a possible short circuit power circuit and control system circuit.

Claims (1)

A reversible transistor bridge containing four transistors, two of which are npn conductivity transistors connected by emitters and connected to the negative of the constant power supply voltage, while the transistors are connected to the load, characterized in that transistors are used as the other two transistors of the reverse transistor bridge rnp conductivity, connected by emitters and connected to the plus of the constant power supply voltage, while the collectors of transistors are opposite The conductivity is combined in pairs, with one pair connected to the first input of the load, and the other pair connected to the second input of the load, the base of the transistors npn conductivity through resistors connected to the minus of the constant power supply voltage for reliable locking of transistors of npn conductivity, the base of transistors pn p-conduction through resistors are connected to the plus of the constant power supply voltage for reliable locking of p-p-p conduction transistors, and the bases are located opposite to the diagonal whether transistors of different conductivity are connected via optocouplers to open the corresponding transistors.

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