SU1638774A1 - One-step dc-to-dc voltage converter - Google Patents

Abstract

The invention relates to the field of electrical engineering and can be used in secondary power supply sources. The goal is to increase reliability by limiting the voltage across the power transistors. The device contains a power transformer secondary windings 2,3 of which are connected via rectifier 4 and filter 5 with output terminals. The primary winding 6 is connected via an additional power transistor 7 and a high-voltage power switch to the input terminals. The high voltage transistor switch consists of N power transistors, N protective diodes, N-1 additional voltage sources and a low voltage transistor 8. When the unlocking voltage comes from the windings of the transformer 20 of the control 21, the power transistors 9 - 11 and 7 unlock and energy is transmitted to output pins. When a blocking voltage is applied from the base windings of the transformer 20, the low-voltage transistor 8 is locked first and then

Description

power transistors of 9-1 g, with the maximum voltage on the collectors of power transistors

9-11 is limited through protective diodes 12,13 at the required level. 1 hp f-ly, 2 ill.

The invention relates to electrical engineering and can be used in the sources of secondary power supply systems of radio engineering, automation and computer technology.

The purpose of the invention is to increase reliability by limiting the voltage on the power transistors of a single-cycle DC / DC converter.

Fig. 1 shows an electrical circuit of a single-cycle DC / DC converter in Fig. 2 — voltage current diagrams for converter elements.

A single-cycle DC / DC converter contains a power transformer of secondary windings 2,3 of which are connected via rectifier 4 and filter 5 with output terminals, and the primary winding 6 is connected between an additional power transistor 7 and a high-voltage transistor switch, which consists of a low-voltage transistor 8 and, for example, from three power transistors 9, 10 and 11, three protective diodes 12, 13 and 14 and two auxiliary sources 15 and 16. The control transitions of the power transistors are connected to the base windings 17, 18 and 19 of the transformer 20 of the control unit 21 via serial circuits 22, 25 and 24 of resistors and diodes, and the control transitions of the low-voltage 8 and additional power 7 transistors are connected through resistors 25, 26 s side windings 27, 28 of the transformer 20, and the first 29 and second 30 closing diodes are connected between the terminals of the primary winding 6 and the input terminals. To evenly distribute the voltage between the power transistors, resistors 31, 32 and 33 can be introduced into the converter circuit.

A single-ended DC / DC converter works as follows.

To separate the input voltage between the power transistors

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9, 10 and 11 are used auxiliary voltage sources 15, 16 and alternate locking of the transistors. In general, it is necessary to have N-1 auxiliary voltage sources. The voltage at the output of each auxiliary voltage source must be N times less than the supply voltage. Diodes 29 and 30 are closing diodes, they help to recover the energy stored in the scattering inductance of the power transformer 1. The protective diodes 12 and 13 perform two functions: first, these diodes disconnect the auxiliary sources from the power transistors 9 - 11 at the time when the power transistors are open, and prevent the input voltage from closing to the auxiliary voltage sources 15 and 16; secondly, the diodes 12, 13 and, together with them, the diode 14 create a circuit for the flow of the blocking current of the base at the absorption intervals of the power transistors 9-11.

At time t0, the control unit 21 generates a trigger pulse. This signal appears simultaneously on the base windings 17-19 and 27, 28, i.e. at time tQ, all transistors 7-11 are unlocked. In the subsequent open state interval t0 - t, the transistors in this converter are similar to processes in a conventional converter with direct diode switching on. Diodes 12-14 and 29, 30 are closed, the outputs of the auxiliary voltage sources 15, 16 are disconnected from the power transistors. The power from the power source is transmitted to the output terminals of the converter. In addition, a subgrid of capacitors of auxiliary voltage sources 15, 16 takes place through the additional windings of transformer 1.

Switching off the transistors occurs in the following order. At some point, block. 21 controls the polarity of the voltage on the primary winding of the transformer 20, respectively, the polarity of the voltage on the windings 17-19 and 27, 28 changes. After the resorption time has elapsed

locked up

transistor 9 is interrupted by the next interval t - tj.

(34, FIG. 2) at the time of the low voltage transistor 8. This low voltage transistor is selected from the class of high frequency and microwave devices and is locked first.

After turning off the transistor 8 at time t, the emittern power circuit

The collector circuit of this transistor closes along the base circuit through diode 14. The base circuit of transistor 9 carries current (35, FIG. 2), which is equal to the collector current, which leads to a rapid resorption of carriers - at the base and off t.

After turning off the transistor 9, the emitter circuit of the power transistor 10 is broken. On the subsequent interval tn-t. The current of the primary winding 6 of the power transformer 1 closes through a collector-to-base transistor 10, a diode 13 and an auxiliary source 11. Resorption occurs in transistor 10, and the base current is equal to the collector current (36, Fig.2). In parallel with this, capacitor recharge occurs at the output of auxiliary source 16. In addition, it is important to note that diode 13 not only creates a path for the blocking current, but also connects auxiliary power supply 16 to the transistor switch. Therefore, in interval 3, the base potential of transistor 10 is approximately equal to the output potential of the auxiliary power source 16. Consequently, the voltage of one auxiliary source is applied to the collector of the transistor 9, i.e. one third of the supply voltage.

At time t3, transistor 10 is turned off (38, FIG. 2). In the subsequent interval, the primary current is closed by the collector junction of transistor 11, diode 12 and auxiliary sources 15 and 16. The potential of the output of source 15 is maintained on the basis of transistor 11. Therefore, a pair of closed transistors 9 and 10 is applied to the supply voltage.

After turning off the power transistor 11 (37, 40, FIG. 2), the closing diode 29 opens at time t4.

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three power transistors 9, 10 and 11 are applied to the input voltage (41, Fig.2).

The voltage equalization at the power transistors 9-11, when they are closed, can be performed by known methods. This can be done, for example, by shunting transistors with zener diodes, resistors, etc. In the converter in Fig. 1, resistors 31 to 33 are provided for this. The current of these resistors opens diodes 12, 13 and the collector potential of transistors 9 and 10 is fixed.

The auxiliary power transistor 7 is controlled by the voltage across the winding 27 synchronously with the other transistors. The moment of turning off the transistor 7 (44, Fig.2) is delayed relative to the moment of polarity change of the voltage of the winding 27 by the time of resorption.

The moment of turning off the transistor 7 (44, Fig. 2) need not necessarily be tied to the moment t of locking the power transistor 11. It is acceptable that the auxiliary transistor is turned off both in the interval and after the time t when the bias the transistor 11. In this case, the circulation of the eneogin in the converter is slightly changed. For example, if the auxiliary transistor 7 is turned off after the transistor 11, then after the time t4 and until the transistor 7 is turned off, the current of the primary winding 6 is closed through the diode 29 and the transistor 7.

After all the power transistors (in Fig. 2, time t) are turned off at a certain moment, the circuit goes into a state when both closing diodes 29.30 are open. In the subsequent interval, the energy stored in the dissipation inductance of the primary winding 6 of the power transformer 1 is recovered.

At time t, the current in the primary winding 6 drops to zero. Further, up to time t, the magnetization current of the power transformer 1 (43, Fig. 2) is closed through the winding 3, the rectifier diode 4 and the output capacitor of the filter 5. At this interval t.-t, the core of the power transformer is demagnetized.

The total voltage across the transistors 9-11 (4G, Fig.2) and the voltage across the primary winding b of the power transformer 1 (42, Fig 2) have a characteristic stepped shape due to the alternating switching off of the power transistors

Thus, the advantages of the proposed converter are in increasing the reliability based on limiting the voltage on the power transistors and simplifying the control part of the converter.

Claims (2)

Invention Formula I. Single-ended DC / DC converter containing a power transformer, the secondary winding of which is connected via a rectifier and a filter with output terminals, the first terminal of the primary winding of the power transformer is connected to the first input terminal through the first closing diode and the second input terminal through a high-voltage transistor switch consisting of a low-voltage transistor connected between the second input terminal and a series circuit of N power transistors, the bases of which are connected s through N protective diodes, respectively, with the first N-1 conductors of the auxiliary voltage sources, connected in sequence, with the base of the power transistor connected by the emitter to the low-voltage transistor connected through the protective diode to the second input terminal to the bases of each of The N power transistors are connected to the first terminals of the serial circuits from the resistor and diode, and the low voltage transistor control transition is connected through a resistor to the base winding of the control unit transformer, in order to increase the reliability by limiting the voltage on the power transistors (N + O-to the base winding of the transformer of the control unit, the second closing diode and the auxiliary power transistor wedged between the first input terminal and the second output of the primary winding of the power transformer A transformer connected via a second closing diode to the first output of the outermost N-1 auxiliary voltage sources, the second output of the other extreme one connected to the second input terminal, the N base windings of the control unit transformer respectively connected between the second terminals of the resistors and the diodes and the emitters of N power transistors, and the control transition of the additional power transistor is connected via a resistor to the (N + 1) -and the base winding of the transformer of the control unit, 2. The converter according to claim 1, characterized in that the auxiliary voltage sources are made on the basis of rectifiers, the inputs of which are connected to the additional windings of the power transformer, and the outputs are connected to storage capacitors. 54 35 56 37 58 39 40 45 44 +0 FIG. 2