RU2016481C1 - Method of control over multichannel stabilized pulse d c / d c converter and device for its realization - Google Patents

Abstract

FIELD: radio engineering. SUBSTANCE: in agreement with method input or output power is measured in converter with choke-storage and load proportional to measured power is formed in output channel presented by separate rectifier and filter. Power key is controlled by monitoring of voltage across this load. Power is measured by measurement of charge and discharge currents of choke-storage of current transformer. Formation of controlled load is carried out by rectification of secondary current of current transformer feeding it through transistor current generator to output of monitored channel. Generation of load in monitored channel proportional to average load of converter over all channels ensures minimization of deviations of output voltages from rated values with arbitrary changes of loads. EFFECT: improved operational stability. 4 cl, 4 dwg

Description

 The invention relates to electrical engineering and is intended for use in multi-channel key transistor DC-DC converters, made according to the scheme with a throttle-drive (with the reverse inclusion of diodes).

 The conversion of the input power to the energy of the magnetic field in the storage throttle with the subsequent release of this energy to the secondary circuit is widely used for small and medium power. In this case, one of the output voltages is controlled and, by its deviation from the task, the parameters (duration, frequency) of the switching pulses of the key controlling the charge of the throttle-drive are changed. In the general case (without the use of special measures), the voltage rise at unloaded sources can reach 30-40 or more percent. The reasons for the instability of the output voltages are basically two: the presence of the leakage inductance of the primary winding of the drive choke, which accumulates additional energy, which leads to voltage spikes during the discharge of the choke, as well as the "non-ideal" filter capacitors containing (stray) stray inductances and resistances, leading to a very significant surge of voltage at the time of circuit closure of the inductor (transformer) to discharge into the load.

 Known multichannel DC-voltage converter of the specified type, which, in addition to traditional circuit elements with a throttle-accumulator, also contains a node for limiting the slew rate of the voltage on the power switch and a multi-winding power transformer with rectifiers and filters in the output circuits of the secondary windings, connected by the primary winding in parallel to the storage choke . The power key of this converter is controlled by the deviation of one of the output voltages from a given value.

 In this converter, the stabilizing effect is achieved by reducing the negative effect of the leakage inductance of the storage inductor on the stability of the output voltages generated by the power transformer, the leakage inductance of which is much less than that of the inductor. However, the destabilizing factor due to the imperfection of the output capacitors remains, since it is not taken into account when controlling for one secondary voltage - stabilization is provided only on the controlled channel.

Known multichannel converter, made according to the scheme with a throttle-accumulator for a given ratio between the filter capacitor capacity, the number of turns of the secondary winding and the load current in each channel (C _i ω _i / I _i = const). The control of the output voltages in this converter is carried out by changing the frequency (and / or duration) of the power key control pulses by the deviation of one of the operating voltages from the set value.

 In this case, the stabilizing effect is also insufficient for all but the controlled channels, since the condition setting the ratio of the parameters works only at fixed loads. In the general case, when acceptable stability of the output voltages is required for arbitrarily varying loads, the provided equality is not fulfilled even with proportional loads, since the time constants of the output channels vary with load changes, and the feedback circuit time constant is a winding 12 with its rectifier and filter - remains constant.

 The stabilization method implemented in the known converter is taken as a prototype of the proposed method as the closest in nature to the problem being solved and the effect achieved.

 The purpose of the invention is to improve the stability of the output voltage of the Converter with an arbitrary change in load.

 The goal is achieved in that according to the method of controlling a multi-channel stabilized pulsed DC-DC converter, containing in each channel a capacitive filter connected to the output of the corresponding channel and connected through the rectifier to the corresponding winding of the multi-winding inductive element, which consists in controlling the output voltage of one of channels, compare it with the reference voltage and change the parameters of the power switch control pulses p eobrazovatelya further measured input or output power of the inverter and the load change proportionally to the output circuit controlled channel.

 The proposed method for controlling converters is determined by the following sequence of actions.

 In the process of operation of the converter, its power is continuously measured, and a load on one of the windings of the inductive element is formed in proportion to the measured power. It can be a primary winding, a separate secondary winding or a winding in one of the output circuits of the converter. The output voltage in the loaded channel is controlled by comparing it with a predetermined value, and the duty cycle (frequency, duration) of the pulses controlling the power switch of the converter is changed by deviation.

 In fact, a load proportional to the average load of the converter is formed on the controlled channel, and the time constant of the channel filter is also determined by the average load of the converter.

∫ $\genfrac{}{}{0ex}{}{\text{T}}{\text{o}}$ i_jdt≈ 0,
что практически всегда обеспечивается выбором конденсаторов фильтров достаточно большой емкости. В этом случае при идеальных конденсаторах (индуктивности L_cj и сопротивления R_cj равны нулю), при идеальном дросселе ( (M_jk=

, что соответствует индуктивностям рассеяния L_pacj, равным нулю), и пренебрегая падением напряжения на выпрямительном диоде, имеем
e_j = K ω_j = U_cj, (1) где e_j - ЭДС j-й обмотки;
ω_j - число витков j-й обмотки;
К - коэффициент пропорциональности;
U_cj- напряжение на конденсаторе C_j.The essence of the proposed method is shown on the example of a real case when the magnitude of the voltage change across the filter capacitor over a period can be neglected
ΔU _Cj =

∫ $\genfrac{}{}{0ex}{}{\text{T}}{\text{o}}$ i _j dt≈ 0,
which is almost always ensured by the selection of filter capacitors of a sufficiently large capacity. In this case, with ideal capacitors (inductances L _cj and resistances R _cj equal to zero), with an ideal inductor ((M _jk =

, which corresponds to the scattering inductances L _pacj , equal to zero), and neglecting the voltage drop across the rectifier diode, we have
e _j = K ω _j = U _cj , (1) where e _j is the EMF of the jth winding;
ω _j is the number of turns of the jth winding;
K is the coefficient of proportionality;
U _cj is the voltage across the capacitor C _j .

+ L_Cj

, (3)
а U_выхj представлено выражением
U_выхj=L_Cj

+ R_Cj(i_j-i_Hj)+U_Cj, (4) где i_j - ток j-й обмотки;
i_нj - ток нагрузки j-го канала.The voltages at all output capacitors U _{cj are} proportional to the number of turns ω _{j of the} corresponding windings, and
U _ojj = U _cj . (2)
With real capacitors and a real inductive element having scattering inductances L _pacj , we can approximately write
e _j = Kω _j = L _rasj

+ L _Cj

, (3)
and U _ojj is represented by the expression
U _outj = L _Cj

+ R _Cj (i _j -i _Hj ) + U _Cj , (4) where i _j is the current of the jth winding;
i _нj - load current of the j-th channel.

+ R_Cj(i_j-i_Hj)=0,
поэтому величина
L_расj

+ L_Cj

+R_Cj(i_j-i_Hj) (5)
представляет мгновенное значение превышения напряжения на обмотках ω_j над напряжениями конденсаторов U_cj, т.е. над средними значениями выходных напряжений U_выхj.The average value of the component
L _cj

+ R _Cj (i _j -i _Hj ) = 0,
therefore the quantity
L _raj

+ L _Cj

+ R _Cj (i _j -i _Hj ) (5)
represents the instantaneous value of the excess voltage across the windings ω _j over the capacitor voltages U _cj , i.e. over the average values of the output voltages U _ojj .

, стремится к нулю при нагрузке соответствующего канала, стремящейся к нулю.As can be seen from expression (5), this excess is determined both by the parameters L _pacj , L _cj , R _cj , and the variables - i _j , i _нj and

tends to zero when the load of the corresponding channel tends to zero.

The voltage at an unloaded source tends to the maximum:
U _cj = K ω _j ,
moreover, this maximum value can very significantly (by tens of percent) exceed the average stresses at rated loads, determined from expression (4).

= const (6)
При таком выборе конденсаторов (при условии, что они одного типа) обеспечивается и приблизительная пропорциональность величины L_cj и R_cj
L_Cj ~ R_Cj~

(7)
Но выражение (6) должно относиться ко всем каналам, в том числе и к каналу с обмоткой обратной связи. Если же нагрузки преобразователя изменяются (пусть даже пропорционально), то выражение (6), удовлетворяя выходным каналам преобразователя, перестает стыковаться с каналом обратной связи, нагрузка которого неизменна. В этом случае напряжения на всех выходах остаются действительно пропорциональными, но перестают быть постоянными.It is impossible to eliminate the influence of the components determined by the parameters L _p , L _c , R _c , but you can try to make these effects approximately equal, which is achieved (partially) in the prototype by choosing capacitors C in accordance with the expression

= const (6)
With this choice of capacitors (provided that they are of the same type), an approximate proportionality of the values of L _cj and R _{cj is} provided
L _Cj ~ R _Cj ~

(7)
But expression (6) should apply to all channels, including the channel with feedback winding. If the loads of the converter change (even proportionally), then expression (6), satisfying the output channels of the converter, ceases to dock with the feedback channel, the load of which is unchanged. In this case, the voltages at all outputs remain truly proportional, but cease to be constant.

с учетом весовых коэффициентов, что обеспечивает минимизацию ошибки (минимизацию отклонений U_выхjотносительно номинала) и стабилизацию выходных напряжений по всем каналам.In the proposed method, condition (6) is fulfilled for the measurement channel by the average value

taking into account weighting factors, which ensures minimization of error (minimization of deviations of U _ojj relative to the nominal value) and stabilization of output voltages across all channels.

 A control device for a multichannel transistor DC-DC converter with a drive choke and filter capacitors in the output circuits, comprising a converter power switch control unit and a comparison unit connected to the filter capacitor of one of the output channels by a measuring input. The structural study of the nodes of the control unit and the comparison node in this device provides proportional control of the current of the power switch base and increased voltage stability at all outputs by reducing the influence of the stray inductance of the accumulator choke.

 The disadvantage of this device is that at randomly varying loads, changes in the output voltages are not controlled and not taken into account, which affects the stability of the output voltages.

 The purpose of the invention is to improve the stability of the output voltage of the Converter with an arbitrary change in its loads.

 The goal is achieved by the fact that in the device for controlling a multi-channel stabilized pulsed DC-DC converter equipped with a multi-winding inductive element and on each channel a capacitive filter connected to the output of the corresponding channel and through the rectifier connected to the corresponding output winding of the multi-winding inductive element, the input winding of which is connected to the power circuit of the power managed key containing the comparison node, the input of which is designed to be connected connected to the output of one of the channels, and the output is connected to the input of the control pulse generation unit, the output of which is intended to be connected to the control input of the power switch, an adjustable load unit and a current transformer are introduced, at least one of the primary windings of which is designed for series connection with one from the windings of a multi-winding inductive element, and the secondary winding is connected to the control input of the adjustable load unit, the power input of which is connected to the input of the comparison unit.

 In addition, a resistor is introduced into the device, designed to be connected in series with the input of the comparison node.

 The current transformer can be multi-winding, with each of its primary windings designed to be connected in series with the corresponding output winding of the multi-winding inductive element of the converter and made with a number of turns proportional to the number of turns of this winding.

 An adjustable load node can be made in the form of a transistor of at least one diode, a resistor, and a capacitor, the emitter of the transistor connected to the first output of the control input and through a diode circuit connected to the base of the transistor connected to the second terminals of the control and power inputs and through a capacitor connected to transistor collector, through a resistor connected to the first output of the power input.

 In FIG. 1, 2 and 3 show a diagram of a control device for various options for including the model of the total load in the power circuit of the converters of the specified type; figure 4 - diagram of the implementation of the adjustable load.

 The control device comprises a control pulse generation unit 1, a comparison unit 2 connected to its control input, a rectifier 3, a capacitor 4, the outputs of which are connected to an adjustable load unit 5, controlled by the current from the output of the current transformer 6, which measures the power of the converter.

 The connection of the node 5 of the adjustable load with the rectifier 3-4 can be direct or performed through the compounding resistor 7.

 The control device in Figs. 1 and 2 is shown as part of a DC-voltage converter with a multi-winding inductive element 8 connected through a power controlled key 9 to the supply inputs, a node 10 for limiting the slew rate of the voltage on the key, and rectifier diodes 11 with filter capacitors 12 in the output circuits.

 Elements 3-6 form a model of the total load connected in the diagram of figure 1 to a separate winding of the inductive element 8, as well as to the primary circuit of the inductive element 8 (figure 2).

 In the diagram of FIG. 1, the transformer 6 has one primary winding, which is included in the circuit of the power controlled key 9.

 In figure 2, the current transformer 6 has several primary windings included in the output circuit between the diodes 11 and the capacitors 12. The number of turns in each of the windings of the transformer 6 included in the output circuit is proportional to the number of turns in the winding of the inductive element 8 of this circuit.

 In Fig. 3, the control device is shown as part of the converter, also made according to the circuit with a throttle-accumulator, the power part of which, in addition to the traditional elements of such a circuit, contains a multi-winding output power transformer 13 connected by the primary winding directly and through the diode 14 to the terminals of the inductive element 8 .

 The primary winding of the current transformer 6 in this converter is included in the primary circuit of the transformer 13.

 The site of the adjustable load 5 can be built according to the scheme of the transistor current generator (Fig. 4) and contains a transistor 15, the base-collector junction of which is shunted by a capacitor 16, and the base-emitter junction is diode 17, and a resistor 18 connected to the collector of transistor 15. the emitter junction of the transistor 15 serves as a load control input.

 The device according to the scheme of figure 2 (in the embodiment with the primary windings of the current transformer 6 in the secondary circuits of the inductive element 8 of the Converter) works as follows.

 At each clock cycle of the converter (when the controlled power switch 9 is turned off), current pulses occur in each of these primary windings, the average value of which (the area multiplied by the frequency) is proportional to the currents of the corresponding output channels, and the average value of ampere-turns due to a given condition ( the number of turns of the current transformer winding is proportional to the number of turns of the corresponding power winding, i.e. the output voltage) is proportional to the power of the channels. Therefore, the total secondary current of the current transformer 6 is proportional to the total output power. This current through the emitter-collector junction of the transistor 15 of the controlled load node 5 in negative polarity enters its capacitor 16, creating a voltage drop across the resistor 18 and an additional load of the rectifier 3 of the model, proportional to the total load of the converter and independent of the redistribution of power along the output channels. Thus, minimization of deviations of the output voltages from the nominal values is ensured.

 In the converter with a power transformer 13 (Fig. 3), the winding of the current transformer 6 included in its primary circuit measures all the flowing secondary power without dividing by channels.

 In reality, when implementing a device using one of these two structures, channels whose power is small compared to the total power of the converter may not be controlled to simplify. In converters with a multi-winding inductive element, these can be channels into which the windings of the current transformer 6 are not inserted, and for the circuit with a power transformer, there can be channels whose windings are made on a storage throttle.

 The inclusion of one primary winding of the current transformer in the circuit of the power switch (figure 1) leads to a simple solution, but with a limited scope. In this case, the input power of the converter is measured with the assumption of a constant input voltage. However, since the input voltage is generally subject to change, this solution is acceptable with a limited range of input voltage fluctuations.

 Thus, in contrast to the known solutions (and prototype), the proposed solution provides control by a parameter that responds to changes in current loads of the converter. With increasing currents in the loads, the model current increases, with decreasing it decreases, and the controlled winding of the inductive element 8 (transformer 13) with the rectifier and filter is in the same mode (with the same time constant) as all output windings (average) , i.e. with the same percentage voltage drop and with the same ripples, which provides a corresponding increase in the stability of all output voltages.

Claims (5)

 1. A method for controlling a multi-channel stabilized pulse DC-DC converter, containing in each channel a capacitive filter connected to the output of the corresponding channel and connected through the rectifier to the corresponding winding of the multi-winding inductive element, which consists in controlling the output voltage of one of the channels, comparing it with the reference voltage and the result of the comparison change the parameters of the pulses of control of the power switch of the Converter, characterized in that for the purpose of improving the stability of the inverter output voltage at an arbitrary change in its load measured input or output power of the inverter and the load change proportionally to the output circuit controlled channel.  2. A device for controlling a multi-channel stabilized pulsed DC-DC converter equipped with a multi-tagged inductive element and a capacitive filter on each channel connected to the output of the corresponding channel and through a rectifier connected to the corresponding output winding of the multi-winding inductive element, the input winding of which is connected to the power circuit of the power controlled a key containing a comparison node, the input of which is designed to connect to the output of one of the channels catch, and the output is connected to the input of the control pulse generation unit, the output of which is designed to connect to the control input of the power switch, characterized in that, in order to improve the stability of the output voltage of the converter with an arbitrary change in its loads, an adjustable load node and a current transformer are introduced, at least one of the primary windings of which is intended for series connection with one of the windings of a multi-winding inductive element, and the secondary winding is connected to the control the input of the adjustable load unit, the power input of which is connected to the input of the comparison unit.  3. The device according to claim 2, characterized in that the input resistor is designed to be connected in series with the input of the comparison node.  4. The device according to claims 2 and 3, characterized in that the current transformer is multi-winding, each of its primary windings being designed to be connected in series with the corresponding output winding of the multi-winding inductive element of the converter and made with the number of turns proportional to the number of turns of this winding.  5. The device according to paragraphs. 2 to 4, characterized in that the node of the adjustable load is made in the form of a transistor, at least one diode, resistor and capacitor, the emitter of the transistor connected to the first output of the control input and through a diode circuit connected to the base of the transistor connected to the second terminals of the control and power inputs and through a capacitor connected to the collector of the transistor, through a resistor connected to the first output of the power input.

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