SU1429260A1 - Bridge-type d.c. voltage converter - Google Patents

Abstract

The invention relates to electrical engineering and can be used in high-power power sources and in a converter of electrical power re- sources with increased supply voltage. The goal is to increase reliability by reducing overloads of semiconductor switches. The device contains semiconductor switches 1-4, made of series-connected control SL

Description

. 14

I jero of transistor 5 and N connected in parallel through fuses 6.1-: 6.N high-voltage transistors 7.1- 7.N, control unit 31. The primary winding of the power transformer 26 is connected to the terminal voltage of the converter and the middle one The unit is connected via a current limiting resistor 27 with a connection point in series.

included thyristors 22 and 23. If one of the high-voltage transistors fails, the converter keys are closed, one of the thyristors 22 (23) is opened, and the thyristor shunting the control transistor of the emergency key to form a circuit; 1l burnout of the corresponding fuse. After burnout, the safety device is restored with 3 or more

one

; The invention relates to electrical engineering and can be used in high-power power sources and in inverter drives with increased voltage.

The purpose of the invention is reliability. by reducing overloading conductor keys.

Fig. 1 shows an electrical circuit of the converter; Fig 2 is a diagram of the control unit; FIG. 3 shows time diagrams of voltages on elements of a control node with an index corresponding to the number of this element.

The constant voltage bridge converter (Fig. 1) contains semiconductor switches 1-4, each of which consists of series. connected high-frequency control transistor 5 and N connected in parallel through the fuses 6,1 6.N high-voltage transistors 7.1-7.N. The basic terminals of the high-voltage transistors 7,1-7.N through diode-resistive chains 8,1-8.N are connected to one terminal of the capacitor 9, the second terminal of which is connected to the e1-pin of the control transistor 5, the base output of the control transistor 5 through the resistor 10 is connected to the control output of the key, which is also connected via diode 11 and the current-limiting resistors 12,1 12. 12.N the basic conclusions of high-voltage transistors 7.1-7.N. A thyristor 15 is connected in parallel to the control transistor 5 through the first winding 13 of the current transformer 14. Parallel to the capacitor 9 are connected in series the Zener diode 16 and the resis

torus 17, while the junction point of the Zener diode 16 and the resistor 17 is connected to the control input of the thyristor 15.,

Through the choke 18, shunted, diode 19J connected to the input terminals 20 and 21 are connected in series thyristors 22 and 23., to the control inputs of which are connected the second windings 24 and 25 of the current transformer 14. The primary winding of the power transformer 26 is connected by an average lead through a current-limiting resistor 27 with a thyristor connection point 22 and 23, and the outermost leads are connected to the diagonal of the alternating current of the bridge converter. The emitting elements of the optocoupler 28 and 29 are connected in anti-parallel and through an additional resistor 30 are connected to the parallel-limiting resistor 27

The control unit 31 (FIG. 2) contains a logical element 3 OR 32, the inputs of which are connected to the photodiodes of optocouplers 28 and 29 and through a matching circuit 33 with the third windings 34 and 35

transformer 14 current. The output of the logic element 3 OR 32 is connected to the first g input and through the delay element 36 to the second input of the logic element 2 1SH 37, the output connected to the R input of the trigger 38. The input of the trigger 38 is given a signal of the logical unit and the C input through the logical the element 39 is connected to the output of the master oscillator 40. The counting input of the trigger 41 is connected to the output of the logic element 2 42, the inputs of which are connected to the inputs of the master oscillator 40 and the trigger 38. The control inputs of the keys 1–4 are connected

a cut of the circuit 43 and YES is an alias to the outputs of the logic elements 2I 45 and 46, the inputs of which are connected to the outputs of the flip-flops 38 and 41.

The converter works in the following way.

In the normal mode of operation, when all transistors in the keys. 1–4 are normal, alternating switching of the diagonally opposite keys 1, 4 and 2 is alternately performed. The switching of calls in normal mode is scored as follows. With a positive polarity of the control signal relative to the emitter of the transistor 5, the control current flows through the first series circuit: diode 11 - resistors 12.1-12.N - base-emitter junctions of high-voltage transistors 7.1-7.N - collector-emitter junction of control transistor 5 and on the second series circuit: resistor I) - the base-emitter junction of the control transistor 5, maintains the control transistor 5 and the high-voltage transistors 7.1-7.N in the full state. The load current flows through the fuses 6.1-6. N, high covoltransistor 7.1-7.N and control transistor 5..

When the polarity of the control signal changes, the transistor 5 closes, disconnecting the emitters of the high voltage transistors 7.1-7.N. Due to the fact that high-voltage transistors are more inertial than low-voltage high-frequency control transistor 5, they remain in the on-state. The load current begins to flow through the base-collector junctions of high-voltage transistors 7.1-7.N, diodes .cords 8.1-8.N, capacitor 9. As a result, the discharge current from the collector and base layers of high-voltage transistors - 7.1-7.N tori with their base-emitter transitions off, i.e. High voltage transistors are closed in a common base circuit. At the end of the dissipation process, the high voltage transistors 7.1-7.N are locked, the charge of the capacitor 9 is stopped.

With the appearance of a triggering voltage pulse, the control transistor 5 and the high voltage transistors 7.1-7., N are opened and the capacitor 9 is discharging

15

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There are four resistors of the chains 8. 1-8.K, base-cutter transitions are high: 7.1-7, N, and transistors of the transistor. 5. High-voltage transistors are forced to turn on, accumulated in the capacitor 9 in the range of charge carrier dissipation.

In normal operation, up to time point t (fig. 3), at the output of the trigger 38, the signatures correspond to a logical unit distributing the output pulses of the master oscillator 40 to the input of the trigger 41 and the output signals of the trigger 41 to the inputs 43 and 44 of galvanic isolation.

Failure of high-voltage transistors usually occurs when they are turned on when dynamic losses are maximal, or when they are closed due to electrical breakdown. At the same time, the failure of high-voltage transistors by short-circuiting its transitions is the most dangerous.

Suppose that at time t, when the keys are open. and 3, the transistor 7.1 fails in the switch 1. The following current flow circuit is formed: the first input terminal 20 - choke 18 - fuse 6.1 - short-circuited collector-base junction, transistor 7.1-- chain diode 8.1 - capacitor 9 - open key 2 - the second input terminal 21. The current ramp up is limited by the choke 18. The capacitor 9 is charged,. at the same time, the voltage at the junction of the colq lector-emitter-control transistor 5 can exceed the voltage on the capacitor 9 only by the voltage of the avalanche breakdown of the base-emitter junction of the high-voltage

with transit g-era 7.1.

When the voltage across the capacitor 9 of the threshold value is exceeded, the Zener diode 16 is broken and the thyristor 15 is opened. The current through the pre-fuse 6.1 closes the circuit: the first input output 20 - choke 18 - fuse 6, {- short-circuited transistor 7.1 - winding 13 of the transformer 14 current 14 - thyristor 15 - public key 2 - second input pin 21.

When current flows through the winding 13 of the current transformer 14, windings 24,25,34 and 35 appear on it.

five

This leads to the opening of the thyristor .3 and the appearance of a single signal at the input of the logic element 31-ShI 32. At the output of the element ZILI 32, a unit also appears, which leads to the appearance of a single at the R input of the trigger 38, at the output which is set to O. A zero signal at the input of logic element 2I | A2 leads to a zero signal at the input of trigger 41 and the trigger 41 remains in the IB state corresponding to the on position of the keys 2 and 3. Since the inputs of logical elements 2 and 45: and 46 a zero signal appears, on; their outputs are also O, that leads to the closure of the key whose 2 and zo

i The current through the fuse 6.1 is shorted along the circuit: the first input output j20 - choke 1B - fuse 6.1 short-circuited transistor 7.1 - winding 13 of current transformer 14 - thyristor 15 - left primary transformer section of power transformer 26 - resistor 27 - thyristor 23 - the second. input terminal 21. The direction of the current through the semi-winding of the power transformer 26 is shown by an arrow. Due to the voltage drop across the current limiting resistor 27, current flows through the LED of the optocoupler 28, resulting in the input 1 of the logic element 31 and 32 being kept 1 for the time of the fuse 6 to blow ,one,

After the fuse 6,1, which is tens to hundreds of conversion periods, is blown, at the time ti, the current in the circuit is stopped, it also stops in the LED of the optocoupler 28, the input and output of the logical element ZRSHI 32 are set to O. With a delay, the necessary for reliable hinge of the thyristors 15 and 23 and determined by the element 36, in the MOMBiiT time tj, the output of the logic element 2 OR 37 is also set to O.

On the falling edge of the pulse generator 40, at time tj, the trigger 38 switches to one, which leads to the interruption of the output signals of the trigger 41 to the inputs of circuits 43 and 44 of galvanic isolation. Trigger 41 is in the pre-emergency position, so that keys 2 and 3 reopen and the current in the primary winding of the power switch is reopened.

transformer 26 has a direction opposite to the current flow, and when it blows out the fuse 6.1. At the output of the logic element 42, clock pulses appear from time t: and the normal operation of the device is restored. Since the duration of the clock pulse is small, the time interval practically corresponds to the half-period and the magnetic circuit of the power transformer from the first pulse enters a steady state,

The converter eliminates the overloading of the transistors of the keys when restoring the operation of the converter - after removing the fuses and improving the power and dynamic characteristics.

Formula of the invention A bridge voltage converter containing semiconductor switches, each of which consists of series-connected N connected in parallel through fuses of high-voltage transistors, control transistor, whose base output is connected via a resistor to the control output of the key, with which connected through a diode and the first current-limiting resistors are basic terminals of high-voltage transistors, two in series, connected thyristors connected to the circuits in one transformer pins, a power transformer, the primary winding of which is connected through the second current limiting resistor to the thyristor connection point, and the extreme leads connected to the AC diagonal of the bridge transformer, current transformer, control unit containing the reference generator, first trigger, o So that, with a view to increasing reliability by reducing the overloads of semiconductor switches, the first and second optocouplers were introduced, the radiating elements of which The enters are counter-parallel and, via an additional resistor, are connected to the second current-limiting resistor, a thyristor connected in parallel to the control transistor through the first

a current transformer winding and a series-connected zener diode and a resistor connected in parallel with a capacitor, one of the terminals of which is connected to the bases of high-voltage transistors through diode-resistive input chains, and the other terminal r is connected to the emitter of the control transistor, and connected to the control electrode of the thyristor, and in the control unit: the first, second and third logic elements 2I, the second trigger, the delay element and logic elements are entered Options ZKPI, 2 or NOT, the inputs of NAND gate ZIPI connected respectively to photodiodes and optocouplers soglasutosch through the circuit - with treti- ivDi windings of the current transformer, and

the output of the ZILI logic element is connected to the first input and through the delay element to the second input of the 2IL element, the output of the second trigger connected to the R input, the D input of which is connected to the source providing the signal of the logical unit, and the C input through the logic element NOT connected to the output of the master oscillator, the counting input of the first trigger is connected to the output of the first logic element 2I, whose inputs are connected to the outputs of the master oscillator and the second trigger, the outputs of the second third logic elements 2I are connected to the control inputs of the converter keys via galvanic isolation circuits, and the inputs are connected to the outputs of the first and second triggers.

FIG. 2

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Claims (1)

Φορ-mule of the invention / A DC-DC bridge converter containing semiconductor switches, each of which consists of N series connected in parallel through fuses of high-voltage transistors, a control transistor, the base terminal of which is connected through a resistor to the control terminal of the switch, which are also connected via a diode and the first current-limiting resistors to the base high-voltage transistor leads, two in series. connected thyristors, connected to the input terminals of the converter, a power transformer, the primary winding of which is connected by a middle terminal through a second current-limiting resistor to the connection point of the thyristors, and connected to the alternating current diagonal of the bridge converter, a current transformer, a control unit containing a master oscillator, the first The trigger, because of the fact that, in order to increase reliability by reducing overloads of semiconductor switches, the first and second opt pairs, the emitting elements of which are connected counter-parallel and are connected in parallel through the second current-limiting resistor through an additional resistor, a thyristor is inserted into each semiconductor key connected in parallel to the control transistor through the first winding of the current transformer, and a zener diode and a resistor connected in series connected in parallel with the introduced capacitor are one of which conclusions through the diode-resistive input circuit is connected to the bases of high-voltage transistors, and the other vyv q 1 is connected to the emitter of the control transistor, while the junction point of the zener diode and the resistor is connected to the thyristor control electrode, and the control node: the first, second and third logic elements 2I, the second trigger, 15 delay element and logic elements ZILI, 2OR are introduced , NOT, while the inputs of the ZILI logic element are connected respectively to the photodiodes of the optocouplers and through the matching circuit to the third 20 windings of the current transformer, and the output of the ZILI logic element is connected to the first input and through the delay element - to the second input of the 2OR element, the output of the second trigger connected to the R-input, the D-input of which is connected to a source providing a signal of a logical unit, and the C-input through a logic element is NOT connected to the output of the master oscillator, the counting input of the first trigger is connected to the output the first logical element 2I, the inputs of which are connected to the outputs of the master oscillator and the second trigger, the outputs of the second and third logical elements 2I are connected to the control inputs of the converter keys through galvanic isolation circuits, and passages are connected to the outputs of the first and second flip-flops.