RU2796257C1 - Current pulse shaper - Google Patents

Abstract

FIELD: power converter electronics.

SUBSTANCE: invention relates to autonomous voltage inverters and can be used as a power source for three-phase loads with inductance, for example, for asynchronous and synchronous electric motors. The current pulse shaper contains two-input AND logic elements, the output of each of which is connected to the input of the corresponding first output stage, the output of each of which is connected to the gate of the corresponding lower transistor, the second output stages, the output of each of which is connected to the gate of the upper transistor, respectively, the limiter voltage, current sensors, counter diodes, the anode of each of which is connected to the source of the upper or lower transistor, respectively, a threshold device. Six current dampers, six voltage dampers, a blanker, a three-phase bridge and a noise filter connected in series are introduced. The first output of each of the current dampers is connected to the drain of the upper or lower transistors, respectively. The second terminal of the first, third and fifth current dampers is connected to the cathode of the first, third and fifth counter diodes, and the second terminal of the second, fourth and sixth current dampers is connected to the cathode of the second, fourth and sixth counter diodes. Six voltage dampers are connected in series. The first output of the first, third and fifth voltage dampers is connected to the cathode of the first, third and fifth counter diodes and interconnected and connected to the first input of the voltage limiter and to the positive bus of the power source. The second outputs of the second, fourth and sixth voltage dampers are connected to the anodes of the second, fourth and sixth counter diodes, interconnected and connected to the negative bus of the power source and to the second input of the voltage limiter. The output of the noise filter is connected to the input of the threshold device, the output of which is connected to the input of the blanker, the output of which is connected to the first inputs of the two-input AND logic elements, the second inputs of which and the inputs of the second output stages are the inputs of the current pulse shaper. The primary circuit of each current sensor is connected to the first output of the second, fourth and sixth voltage dampers and is one of the outputs of the current pulse shaper, and the secondary circuit of each current sensor is connected to the input of the three-phase bridge, respectively.

EFFECT: limited levels of switching extra currents when switching power transistors, improved electromagnetic compatibility, increased efficiency, performance with given electrical characteristics under the influence of the EF (external factors) with high values of impact characteristics.

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Description

The invention relates to the field of power converter electronics, in particular, to autonomous voltage inverters and can be used as a power source for three-phase loads with inductance, for example, for asynchronous and synchronous electric motors.

An autonomous voltage inverter is known (see patent RU No. 2403667 dated July 27, 2009, published in B.I. 31 on November 10, 2010), which contains a three-phase bridge connected to the input terminals on transistors shunted with counter diodes, the output terminals of which connected to the output terminals of the voltage inverter, three current sensors included in the output terminal circuits of the voltage inverter, transistors are shunted by capacitors and varistors, a three-phase bridge on transistors is shunted by a voltage limiter and a series circuit of two capacitors, the common connection point of which is connected to the ground terminal of the voltage inverter, the voltage inverter is equipped with six series circuits containing a two-input AND circuit and an output stage, the outputs of the output stages are connected to the control electrodes of the transistors, a pulse distributor, the outputs of which are connected to the first inputs of the two-input AND circuits, a master oscillator, the output of which is connected to the input of the pulse distributor, six comparators, the outputs of which are connected to the second inputs of the two-input AND circuits, and the inputs are combined in pairs and connected to the outputs of the current sensors, the outputs of the three-phase bridge are shunted in pairs by additional snubber capacitors.

The disadvantages of the above autonomous voltage inverter is the lack of limiting the levels of switching extra currents when the power transistors are turned on, since the device operates in a quasi-resonant mode, which provides a "soft" switching mode only when the power transistors are turned off.

The above device is the closest in technical essence to the claimed device and therefore selected as a prototype.

The technical problem to be solved is the creation of a current pulse shaper with extended functionality.

The achieved technical result is to ensure the limitation of the levels of switching extra currents when switching power transistors, improve electromagnetic compatibility, increase the efficiency (COP), performance with specified electrical characteristics under the influence of the VF (external factors) with high values of the impact characteristics.

To achieve a technical result in a current pulse shaper containing two-input "AND" logic elements, the output of each of which is connected to the input of the corresponding first output stage, the output of each of which is connected to the gate of the corresponding lower transistor, the second output stages, the output of each of which is connected to the gate of the upper transistor, respectively, voltage limiter, current sensors, counter diodes, the anode of each of which is connected to the source of the upper or lower transistor, respectively, the threshold device, the new is that the first, second, third, fourth, fifth, sixth current dampers are additionally introduced , the first output of each of which is connected to the drain of the upper or lower transistors, respectively, the second output of the first, third and fifth current dampers is connected to the cathode of the first, third and fifth oncoming diodes, and the second output of the second, fourth and sixth current dampers is connected to the cathode of the second, fourth and sixth counter diodes, the first, second, third, fourth, fifth, sixth voltage dampers, the first and second, third and fourth, fifth and sixth of which are connected in series, the first output of the first, third and fifth voltage dampers is connected to the cathode of the first, third and fifth counter diodes and are interconnected and connected to the first input of the voltage limiter and to the positive bus of the power source, the second terminals of the second, fourth and sixth voltage dampers are connected to the anodes of the second, fourth and sixth counter diodes, interconnected and connected to the negative bus of the power supply and to the second input of the voltage limiter, a blanker (blank node), a series-connected three-phase bridge and a noise filter, the output of which is connected to the input of a threshold device, the output of which is connected to the input of the blanker, the output of which is connected to the first inputs of two-input logic elements "AND", the second inputs of which and the inputs of the second output stages are the inputs of the current pulse shaper, the primary circuit of each current sensor is connected to the first: the output of the second, fourth and sixth voltage dampers and is one of the outputs of the current pulse shaper, and the secondary circuit of each current sensor is connected with the input of a three-phase bridge, respectively.

The figure shows a circuit of the current pulse shaper.

The current pulse shaper contains the first 1, the second 2, the third 3 two-input logic elements "AND", the output 1 of the element is connected to the input of the first output stage 6, the output 2 of the element is connected to the input of the first output stage 8, the output 3 of the element is connected to the input of the first output stage 10. The output of each stage 6, 8, 10 is connected to the gate of transistors 13, 15 and 17, the second output stages 5, 7, 9, the output of each of which is connected to the gate of transistors 12, 14 and 16. Voltage limiter 36, current sensors 37, 38, 39, counter diodes 24, 25, 26, 27, 28, 29, the anode 24, 26, 28 of the diodes is connected to the source of 12, 14 and 16 transistors, and the anode 25, 27, 29 diodes is connected to the source of 13, 15 and 17 transistors. The threshold device 11, the first 18, the second 19, the third 20, the fourth 21, the fifth 22 and the sixth 23 current dampers, the first output 18, 20, 22 of the current dampers is connected to the drain 12, 14 and 16 of the transistors, and the first output 19, 21 and 23 current dampers are connected to drain 13, 15 and 17 transistors. The second output 18, 20 and 22 of the current dampers is connected to the cathode 24, 26 and 28 counter diodes, and the second output 19, 21 and 23 of the current dampers is connected to the cathode 25, 27 and 29 counter diodes. First 30, second 31, third 32, fourth 33, fifth 34 and sixth 35 voltage dampers, while 30 and 31, 32 and 33, 34 and 35 are connected in series. The first output 30, 32 and 34 of the voltage dampers is connected to the cathode 24, 26 and 28 counter diodes, interconnected and connected to the first input of the voltage limiter 36 and to the positive power bus, and the second output 31, 33 and 35 of the voltage dampers is connected to the anode 25, 27 and 29 counter diodes are interconnected and connected to the second input of the voltage limiter 36 and to the negative power bus. Blanker 4, series-connected three-phase bridge 40 and noise filter 41, the output of which is connected to the input of the threshold device 11, the output of which is connected to the input of the blanker 4, the output of which is connected to the first inputs of the two-input logic elements "AND" 1, 2, 3, the second inputs which and the inputs of the output stages 5, 7 and 9 are the inputs of the current pulse shaper, the primary circuit of the current sensors 37, 38 and 39 is connected to the first output 31, 33 and 35 of the voltage dampers and is one of the outputs of the current pulse shaper, and the secondary circuit of the current sensors 37, 38 and 39 is connected to the input of the three-phase bridge 40.

Two-input circuits "AND" 1, 2, 3 provide the transmission of external control signals to the output stages 6, 8, 10, and also match the signals of the blanker 4 with them in voltage. Two-input circuits 1, 2, 3 can be implemented on high-speed digital logic elements "2I", providing the same minimum delay of transmitted signals.

The output stages 5-10 are designed to amplify external input signals in order to control the power transistors 12-17. They can be implemented on control chips (drivers) with power MOSFETs (metal-oxide semiconductor).

Power transistors 12-17 are designed to switch the external supply voltage in order to form the output signals U, V, W. They can be implemented on powerful transistors with field and current control: DMOS (two-diffusion MOS) and IGBT (insulated gate bipolar transistor).

Current dampers 18-23 are designed to optimize the process of switching power transistors 12-17 at the time of their inclusion. They can be implemented as core inductors based on magnetic circuits with a rectangular hysteresis loop. Due to the rectangular shape of the hysteresis loop, current snubbers achieve a very large inductance at the moments of zero crossing of the current flowing through them, i.e. the formation of the switching trajectory of power transistors is carried out in the “zero currents” mode, which provides effective damping of rapid current changes.

Nodes 24-29 and 36 provide shunting of the circuits of the current pulse shaper (FIT) when the polarity and level of the supply voltage are changed, created by a dynamic load, limiting the overvoltage levels on the power transistors 12-17, and also dissipate additional energy created by changes in currents on the linear inductances of the tires power supply and installation when switching power transistors. Nodes 24-29 can be implemented on high-current high-voltage fast diodes, and node 36 (voltage limiter) on a powerful zener diode.

Voltage dampers 30-35 are designed to optimize the switching process by power transistors at the moment they are turned off. They can be implemented on RC circuits consisting of a resistor and a film capacitor connected in series. Voltage dampers 30-35 provide effective damping of the voltage rise rate by forming the switching path of power transistors in the "zero voltage" mode.

Current sensors 37-39 are designed to convert the currents flowing through them into voltage. They can be implemented both on current transformers and on magnetoresistive current sensors.

Three-phase bridge 40 is designed to rectify and sum the output voltages from the current sensors 37-39. It can be implemented on pulse diodes, the inputs of which are connected to current sensors, and the outputs are connected together,

Filter 41 is an RC circuit for filtering impulse noise that occurs during the operation of power transistors 12-17, preventing false operation of the current protection unit (nodes 4, 11, 40, 41).

The threshold device 11 is a voltage comparator that compares the input signal from the noise filter 41 with a reference voltage (not shown in the diagram).

Blanker 4 is a single vibrator that generates a signal to prohibit the operation of power transistors 12-17, which is fed to two-input circuits 1-3.

The reference voltage source, threshold device 11 and blanker 4 can be implemented on the basis of a PWM controller chip.

An increase in the reliability of operation is ensured by the implementation in the FIT of the resonant mode of operation of power transistors due to the introduction of current dampers, i.e. it operates with complete “soft” switching both when turned on (zero current mode) and when power transistors are turned off (zero voltage mode). The conditions for the resonant mode of operation of power transistors are provided by choosing the desired ratio between the values of the capacitances of voltage dampers (30-35) and

inductances of current dampers (18-23), which in the circuits of power transistors (12-17) form series and parallel oscillatory circuits, between which the balance of reactive energy exchange is maintained. This exchange energy is embodied in a sinusoidal form of currents and voltages of the FIT field/conductor elements.

An increase in the efficiency of the device is provided by reducing the dynamic power losses at the moments of switching on and off the power transistors, which is ensured by the implementation of the full mode of their "soft" switching.

Improving the electromagnetic compatibility of the PIT is provided by switching at the moment of zero current, which reduces the value of the derivative of the current rise and, consequently, the level of interference created by differential currents at the moment the power transistors are turned on.

FIT works as follows.

From the external module, low-current pulse control signals are fed to the output stages 5-10. These external pulse signals are sent directly to nodes 5, 7, 9, and to nodes 6, 8, 10 - through the first inputs of two-input circuits 1, 2, 3. From the outputs of nodes 1, 2, 3, these external pulse signals are transmitted to the output stages 6, 8, 10 only if the current protection unit (nodes 4, 11.40, 41) receives an enable signal to the second inputs of nodes 1, 2, 3.

The pulse signals amplified by nodes 5-10 are then amplified by power transistors 12-17 by switching the power supply of the positive "+" and negative "-" poles of the source, forming high-current bipolar pulse signals (U, V, W) at the PIT outputs. In the switching processes (moments of switching on and off) of power transistors 12-17, current dampers 18-23 and voltage dampers 30-35 are jointly involved, creating a resonant mode of operation of power transistors.

The node 36 connected to the power supply provides voltage limitation at the set level.

The output pulse currents of the signals U, V, W. flowing in the first windings of the current transformers 37-39, induce currents in the second windings proportional to the signals U, V, W. The current transformers 37-39 provide galvanic isolation of the inputs of the three-phase bridge 40 from the output pulse signals U. V, W, and convert the current flowing through them into a voltage proportional to the current. The outputs (second windings) of the transformers are loaded with resistors (not shown in the diagram) to prevent saturation of the current transformer cores. By changing the ratings of the load resistors of the current transformers, you can change the response threshold of the protective unit.

The signals from the outputs of the current sensors 37-39 are fed to the inputs of the three-phase bridge 40. The signals at the outputs of the current sensors can be bipolar, and the diode bridges convert bipolar signals to unipolar, i.e. allocate modules of signal values at their inputs. The combined outputs of three diode bridges ensure the selection of the maximum signal coming from the current sensors. The signal at the output of the three-phase bridge 40 is less than the signals from the current sensors 37-39 by the value of the drop voltage on the two diodes of the bridge, and this voltage has a negative temperature dependence, which provides "automatic" adjustment of the protection unit response threshold from temperature changes, i.e. the independence of the operation of the protective block from temperature changes is ensured.

The signal from the output of the three-phase bridge 40, passing through the filter 41, is cleared of induced interference, and is fed to the input of the threshold device - comparator 11. The threshold device 11 compares the signal at its input with the reference voltage. When the input signal exceeds the threshold (reference) voltage, the comparator "triggers" and outputs a signal to the blanker 4, which generates a signal that enters the two-input circuits 1, 2, 3 and prohibits their operation, thereby limiting the output currents of power transistors 12-17 and preventing their failure.

A prototype FIT was made, which confirmed its performance.

Claims (1)

A current pulse shaper containing two-input "AND" logic elements, the output of each of which is connected to the input of the corresponding first output stage, the output of each of which is connected to the gate of the corresponding lower transistor, the second output stages, the output of each of which is connected to the gate of the upper transistor, respectively, voltage limiter, current sensors, counter diodes, the anode of each of which is connected to the source of the upper or lower transistor, respectively, a threshold device, characterized in that the first, second, third, fourth, fifth, sixth current dampers are additionally introduced, the first output of each of which connected to the drain of the upper or lower transistors, respectively, the second terminal of the first, third and fifth current dampers is connected to the cathode of the first, third and fifth counter diodes, and the second terminal of the second, fourth and sixth current dampers is connected to the cathode of the second, fourth and sixth counter diodes, the first, second, third, fourth, fifth, sixth voltage dampers, the first and second, third and fourth, fifth and sixth of which are connected in series, the first output of the first, third and fifth voltage dampers is connected to the cathode of the first, third and fifth counter diodes and are interconnected and connected to the first input of the voltage limiter and to the positive power supply bus, the second outputs of the second, fourth and sixth voltage dampers are connected to the anodes of the second, fourth and sixth counter diodes, interconnected and connected to the negative power supply bus and to the second input of the voltage limiter, a blanker, a three-phase bridge and a noise filter connected in series, the output of which is connected to the input of a threshold device, the output of which is connected to the input of the blanker, the output of which is connected to the first inputs of the two-input AND logic elements, the second inputs of which and the inputs of the second output stages are the inputs of the current pulse shaper, the primary circuit of each current sensor is connected to the first output of the second, fourth and sixth voltage dampers and is one of the outputs of the current pulse shaper, and the secondary circuit of each current sensor is connected to the input of the three-phase bridge, respectively.

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