SU855897A1 - Stabilized dc converter - Google Patents

Description

(54) STABILIZED DC CONVERTER

The invention relates to power converter technology and can be used in laser power supplies. Constant voltage istoshics are known which can be used to power lasers consisting of a single-cycle conversion. a DC voltage coupler whose transistor switch is controlled by a relay amplifier connected to the feedback circuit for load 1. The disadvantage of such sources is their relatively low reliability and large amplitude of output voltage ripples due to different switching times of parallel-connected transistors. DC sources are also known in which reliability is built up by dividing the power section into a series of inverters of the same type loaded via autonomous smoothing chokes into a multi-winding transformer, the secondary winding of which is connected to the load 2 via a rectifier and filter. is their complexity, relatively low efficiency and large mass and weight dimensions due to the presence of a multiwinding transformer, an additional rectifier and a general control circuit. The closest in technical essence to the present invention is a pulsed 1 DC bus regulator containing at least two converter cells connected in parallel to the input and output terminals, the control inputs of which are connected to the control unit 3. The disadvantage of such a device is relatively low efficiency and the possibility of current overloads of individual cells, which reduces the reliability of the entire device, as well as a large amplitude of output voltage and current ripple. The purpose of the invention is to increase efficiency and reliability, reducing the amplitude of the ripple of the load current of the stabilized converter. The goal is achieved by the fact that in a stabilized DC / DC converter the control unit is implemented as a control element of each cell and a common control consisting of a load current sensor connected to one of the inputs of the comparison circuit, the other input is connected to the reference source. voltage, and the output through a voltage limiter connected to one of the inputs of the control elements, each of which is made in the form of a relay regulator connected by another input to the measuring resistor Oru and output - through the power amplifier to the control input of the converter cell.

In addition, a comparator with positive feedback is entered into the control element of at least one converter cell, the output is connected to the power assistant and the input is entered with a time delay chain, and a threshold element is inserted into the general control element whose input is connected to the output comparison circuits and output with all time delay chains.

The drawing shows a schematic diagram of a stabilized DC converter of gas lasers.

The source contains a series of transistor converter cells 11-5, made in a single-ended direct converter circuit, each of which contains an input fuse 2, an input capacitor 3, a transistor 4, an LDC filter 5, 6, 7, an output fuse 8. Each converter cell contains control element, including relay controller 9, the input connected to the measuring resistor 10, and the output to the power amplifier And, the output of which is connected to the base of the transistor 4. At least one of the converter cells contains A time delay circuit 12 and a comparator 13 covered by positive feedback 14 A common control includes a load current sensor 15, a comparable circuit 16, a limiter 17 a voltage w and a threshold element 18. The input pins of all converter cells are connected to the supply voltage source E, and output pins to the consumer 19, in the circuit of which the load current sensor 15 is included. The comparator 13, covered by feedback 14, in N cells 1, is connected by its output to an amplifier 11 of power, and the input to an output of a chain 12 by a time delay. The output of the current 15 is connected to one of the inputs of the comparison circuit 16 connected to another by its input and the source of the reference voltage U, and the output through the voltage limiter 17 to the input of the relay regulator 9 of each converter cell, in addition, the output of the comparison circuit 16 through

threshold element 18 is connected to the input line 12 of the delay of those converter cells in which they are located.

The Converter operates as follows.

P {W input power supply E, all converter cells start to operate in the stabilization mode of their own output current, the level of which is set by the output voltage taken from the output of the capacitor (voltage generator 17). Since the load current does not have time to rise immediately to the nominal value, voltage Ui6 at the output of the comparison circuit 6 is maximum IT.

In order to avoid current overloads of the converter cells li and Hz during start-up, the maximum voltage supplied to the control inputs of the control elements is limited by the limiter 17 introduced for this purpose. As the current increases, the current sensor 15 increases and Ujg is reduced down to the level at which the load current is set to a nominal value. The output current of each cell is determined only by the magnitude of the control voltage Uc supplied to one of the inputs of the relay regulator 9. Since the voltage is common

for all controls, the current load of all the converter cells is the same. If one of the cells fails, it is disconnected from the common circuit by burning out fuses 2 or 8, depending on the type of failure. When the input fuse is burned out, the remaining cells cannot be overloaded in principle, and when the output fuse is burned out, each of the working cells can be loaded to the value determined by the maximum control voltage U. The limiter 17 is selected taking into account that and does not exceed the permissible value. After the fuse of the failing cell has been burned out, the load current

re-set at nominal level. In this case, the current load of working cells increases by an amount equal to

N

that when N 5-10 compositionN (N - 1)

Claims (3)

It is less than W-20% of the nominal load. Thus, in ustroyuschestvo, the defective converter cells are automatically disconnected, the current overload of the operable cells is eliminated, and the consumer current is maintained at a predetermined level even after the failure of one or several cells. The reliability of such a partitioned conversion of 585 l with a constant redundancy of backup converters is the higher, the higher the depth of partitioning, i.e. the higher N. Since the control element of each of the cells is autonomous, the switching times of the power transistors do not coincide with each other, which leads to a decrease in both high-frequency and high-frequency pulsations at the input and output of the converter. This is especially noticeable with a large number of converters, since it is in this case that the most complete compensation of the pulsations of their output currents occurs. Thus, the invention is more reliable than the known one, since it eliminates the overload of individual converter cells due to the redistribution of currents between them, eliminates cell overload during converter start-up and prevents overloading in case of failures and disconnections of faulty converter cells. In the known Converter, as the level of the current to be stabilized decreases, the efficiency of the device decreases, which is observed due to an increase in the relative share of losses to control losses in throttle and dynamic losses in transistors. To ensure constant efficiency of the converter, the device provides for automatic disconnection of excess cells in the case of a decrease in the stabilization level l, since a decrease in the voltage U is accompanied by a decrease in the output voltage of the comparison circuit and, and a control voltage U, which leads to a decrease in the output currents of all the cells. If U | 6 reaches the low trigger level of the threshold device 18, the latter triggers and the voltage at its output becomes negative. After a certain time interval, determined by the delay time t, of the chain 12 in cell 1, the comparator 13 is oversampled, in which the blocking voltage comes from the output of power amplifier 11 to transistor 4. Thus, the cell Y y is turned off (de-energized), and the load current is reduced, which leads to an automatic increase in Uj6 and and. An increase in these voltages leads to an increase in the current loading of the B1 switched cells and the transition of the threshold device 18 to its neutral state. The comparator 13 ate reversal remains in a new state, which maintains the disabled state of the converter after the threshold device 18 goes into the neutral state. With a further decrease in the stabilization level 1, the voltage Uie starts to decrease again until, at a certain value of U Ui6VTvin s, the threshold device 18 triggers. In this case, n-1 cell is turned off if it is like a time delay and comparator The process of disconnecting the extra transducer cells takes place until all the cells containing time delay chains and comparators are de-energized. In order for the cells to be switched off alternately, the delay times of the chains are 12j, 2y, etc. selected different, while t3 (n) 1z (I-1) t3 (n.2j, ETC.) To exclude the uncontrolled cell shutdown mode, the delay time t3 {) must exceed the time interval during which the load current after the moment of excess cell rises to the nominal level. With an increase in the level of stabilization of the load current, the reverse process of alternately connecting cells that are in the disconnected state is observed. Similarly, if a source fails at one of the cells, the voltage Ui6 rises to the upper response level of threshold device 18. The latter is triggered, while the voltage at its output becomes positive and the i-th cell is connected after a delay time tsti). Thus, in the proposed ycTpofirvt e, the number of switched on cells is strictly determined by the value of the load current being stabilized, which increases the efficiency of the converter as a whole. In addition, the transfer of excess cells in the cold standby mode significantly increases the reliability of the source. The chain 12 of the time delay can be made in the form of an RC circuit connected at the input of the comparator 13, which is shunted by counter-parallel-connected diodes. The diodes limit the voltage level on the timing capacitor and significantly increase the linearity of the voltage change across the capacitance at Ui8 Ujj, where Ud is the voltage on the open diode (in the drawing). The proposed device in comparison with the known is characterized by greater reliability, greater efficiency and lower amplitude of the current ripple load. Claim 1. Stabilized DC / DC converter containing at least ve converter cells, connected in series with the input and output terminals, the control inputs of which are connected to the evil of control, which, in order to improve reliability 785 reducing the ripple level of the load current; the control unit is made as a control element of each cell and a common control consisting of a load current sensor connected to one of the inputs of the comparison circuit, the other input of which is connected to the reference voltage source, and the output through the limiter the voltage is connected to one of the control element inputs, each of which is made in the form of a relay controller connected by another input to the measuring resistor and the output through a power amplifier to the control the input of the converter cell. 2. The converter according to claim 1, in connection with the fact that, in order to increase efficiency and reliability, into a control element, at the edge of At one transducer cell, a comparator with positive feedback is inserted, an output connected to a power amplifier and an input is inserted into a time delay chain, and a threshold element is inserted into the common control, the input of which is connected to the output of the reference circuit, and the output with all the chains time delay. Sources of information taken into account in the examination 1. USSR Author's Certificate No. 453681, cl. G 05 F 1/56, 1974. 2. USSR author's certificate number 527701, cl. G 05 F 1/56, 1976, 3. US Patent N 4017745, cl. H 03 K 17/60 1976.