SU788301A1 - Stabilized dc voltage converter - Google Patents

Description

; 54) STABILIZED CONSTANT VOLTAGE CONVERTER

one

The invention relates to electrical engineering and can be used in secondary power sources. It is especially advisable to use it in cases where high quality indicators are required from the source for the output DC voltage, which has either a very small or very high value compared to the power supply voltage.

A stabilized DC voltage converter is known, which contains a pulse voltage regulator, an LC filter, the choke of which has a main and auxiliary windings wound bypass. The same terminals of both windings are connected together and connected to the output of the converter. The control unit is connected to the output through an additional winding of the choke. The use of an additional winding of the throttles in the feedback circuit allows us to achieve stable operation of the converter with filter parameters that ensure high quality indicators of the device as a whole. I.

The disadvantage of this converter is, for example, xeni, which limits its inhalation to about-.

The area of application is the presence of galvanic communication in the power circuit between the input and output and low weight and mass parameters.

Also known is a stabilized DC converter containing an input filter, key units of a pulse controller, and

10 an inverter with a transformer, an output rectifier, LC filters at the output of the pulse controller and the indicated rectifier, a control unit connected by a key block of the pulse controller 15 and the output of the converter. In this converter, galvanic isolation along the power circuit is provided by an inverter transformer 2.

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However, the known DC / DC converter contains two series-connected LC filters, so it has low stability. Frequently, a feed to a feedback voltage control unit from the filter output of the pulse controller is used to obtain stable operation. But with such a regulation, the stabilization accuracy is reduced.

30 Closest to the proposed stabilized DC voltage converter, contains a stability chain, which includes the additional winding of the throttle of the smoothing filter of the output rectifier, wound with a main capacitor and connected to it through a capacitor and a resistor that connects the input of the control unit to the converter output . In this case, one smoothing of the filter filter is excluded from the variable-control loop by the variable component, and for certain parameters of the filter of the pulse regulator and the load current it is possible to achieve the full stop operation of the J3 converter. However, the presence of parasitic parameters in the inverter transformer, especially the leakage inductance between the primary and output windings reaching the highest value with very small and very large transformation ratios, leads to an additional phase shift and makes correction more difficult. Therefore, the converter remains critical to the change of the load current and the choice of parameters of the damping filters and is prone to self-assembly. The purpose of the invention is to increase the stable operation of the converter regardless of the parameters of the smoothing filters and the inverter transformer. This goal is achieved by the fact that in a stabilized DC / DC converter containing key regulator blocks with an LC filter and an inverter with an output transformer, the power rectifier is equipped with an output LC filter, the choke of which has an additional winding, a magnet but connected to the main unit control, connected between the key block of the pulse regulator and the converter output and connected at the input to the converter output by means of a resistance chain containing the specified additional winding, section capacitor capacitor and resistor, inverter transformer, equipped with additional windings, one of which. magnetically associated with the primary, and the other with the secondary. The terminals of these windings are connected to the inputs of the inserted rectifiers, loaded on the ballast resistors, and the outputs of the rectifiers are connected in series and counter and via a coupling capacitor are connected to the terminals of the resistor for increasing stability. The first pin of the additional resistor is connected to the second pin of the additional winding of the output filter drossel, and the second through the additional winding of the regulator filter throttle, magnetically connected with the main one, to the input of the control unit. The proposed connection of the control unit to the output of the converter makes it possible to regulate by the constant component - directly by the output voltage, and by the variable - by the voltage from the input of the regulator filter. Due to the exclusion from the control loop of the variable component of the oscillatory links of the two smoothing filters and the parasitic parameters of the transformer, the converter remains stable with changes in the load current and filter parameters over a wide range. FIG. 1 shows a simplified DC voltage converter circuit; in fig. 2 - time diagrams of voltages. The voltage from the power source 1 is supplied to the key block 2 of the pulse controller. The smoothing filter of the pulse regulator contains a choke 3 with a main 4 and an additional 5 windings and a capacitor 6. An inverter unit 7 with an output transformer 8 is connected to the output of this filter. The primary winding 9 of the transformer is magnetically connected to the additional 10, and the secondary 11 with the additional 12. The transformer is connected to a power rectifier 13, the output of which is connected to an LC smoothing filter. The choke 14 of this filter has a main winding 15 and a magnetically coupled additional winding 16, and the capacitor 17 is connected to the output pins 18 and 19 of the converter. Additional windings 10 and 12 of transformer 3 are connected to rectifying-: m, respectively, on diodes 20-23 and 24-27, loaded on ballast resistors 28 and 29 / Consistently and counter-connected rectifier outputs are connected to resistor 31 via coupling capacitor 30. control unit 32) is connected to the key unit of the pulse controller 2 and controls the operation of its transistors. The input of the control unit through the winding 5, the resistor 31 and the winding 16 is connected to the output terminal 18 of the converter. The principle of operation of the DC / DC converter is illustrated by the timing diagrams shown in FIG. 2. After the dc converter is connected to the power source 1, the transistors of the key unit 2 of the pulse controller work with the frequency and duty cycle specified by the control unit 32. The voltage pulses from its output Uj (Fig. 2) are fed to the input by a live filter on the choke 3 and the capacitor 6. The smoothed and filtered voltage equal to the average value 1) is converted by the inverter 7 into an alternating rectangular voltage U which is applied to primary winding 9 of the transformer 8.

Normally, the operation of the pulse controller and the inverter is synchronized. FIG. 2, the operating frequencies of the inverter and the pulse controller are chosen equal, but the ratio between them can be any, since this does not matter in principle.

The voltage form on the output winding of the transformer 8 depends on the ratio of its parasitic parameters. If the attenuation coefficient is greater than one, then it is exponential. FIG. 2, just such an example was chosen as an example, and the voltage Us on the output winding is approximated directly. The resulting voltage, after rectification, is supplied to the smoothing filter, which filters the variable component so that the output voltage of the converter is constant voltage Ugj ,,,.

To increase the stability in the known converter, an additional winding 16 is used, throttle 14, wound bifilly from the main one and connected with it oppositely. Therefore, the voltage Ue- from the output of the winding 16 repeats the form of the voltage. at the input of the output filter and differs from it by the magnitude of the voltage drop across the active resistance of the main winding 15. From the comparison of the voltage diagrams U and the voltage UjL on the primary winding of the transformer it is seen that it is lagging in phase from U2 - This phase shift due to inductance scattered between the primary and output windings, may cause unstable operation of the converter. To eliminate it, the proposed converter uses two additional transformer windings and two rectifiers with several auxiliary elements.

The additional winding 10 of the transformer 8 is magnetically connected with the primary 9 by means of their bifilar winding, therefore the voltage on it coincides in shape with the voltage of ultrasonic on the primary winding. The voltage form Uj at the output of the rectifier connected to the additional winding 10 is shown in FIG. 2

Until this reason, the voltage on the winding 12 coincides in form with the voltage and, and at the output of the rectifier connected to it, the voltage U-j acts. The total voltage Ug on the two oppositely connected rectifiers is unipolar pulses arising at the moments of the voltage dip at the input of the output filter. These pulses can be considered as rectified voltage on the leakage inductance of a transformer.

After the separation by means of a coupling capacitor 30 of a constant component Ug on the auxiliary resistor 31, a voltage Uq is applied, which, when added to the voltage U, creates a voltage t coinciding in phase with the output voltage of the inverter. Thus, the phase shift caused by the parasitic parameters of the transformer and the output filter is eliminated.

To eliminate the phase shift introduced by the pulse controller filter, additional

15 winding 5 drops 3. The voltage across it and repeats the voltage on the main winding 4 with an accuracy to the value of the voltage drop on the ohmic resistance of the winding 4. As a result, the feedback voltage U, equal to the sum of voltages and and, which, as can be seen from the timing diagrams, is in phase with voltage and coming from block 2.

 The exception is almost completely phase shift due to the inertia of all parts of the converter, violates the condition for the occurrence of self-oscillations and the scheme in the dangerous frequency zone becomes stable. In this case, the DC control unit performs regulation directly on the output voltage of the converter.

5 Often, the primary winding 9 of the transformer 8 is connected to the output of the inverter 7 via an isolating capacitor, which prevents the core from magnetizing. Such a connection is also present in half-bridge inverter circuits. It may be that the phase shift introduced by the coupling capacitor is much larger than the phase shift introduced by the parasitic parameters of the transformer. Scheme

5, the converter can be simplified by eliminating the additional winding 12, the resistor 29, and the rectifier on the diodes 24-27.

Such a simplification of the circuit is also advisable in the case when the capacitor 6 of the smoothing filter of the pulse regulator is large enough and the component voltage across it is variable, as well as at the output of the terminal 5, the dielectric diodes 20-23 are absent. ; In most cases, the transformer 8 of the inverter has a transformation ratio n W / W different from one. Under this condition, the number of windings for additional windings of electromagnetic elements should be selected as follows:

W-t6 W W, f W4 If the feedback voltage, with the distance of decreasing its value, si S

From the output voltage divider, the number of turns of all additional windings should be reduced in / as much time.

Negative half-wave feedback voltage U, which appears due to the voltage drop across the active resistances of the electromagnetic elements, transformer scattering inductance, transistors and converter diodes, can become an obstacle to the use of pulse-width modulation at the frequency-frequency axis. phase principle implemented by two generators. The phase shift between them is adjusted depending on the output voltage level by controlling the frequency of the slave generator with a feedback voltage at a stable frequency of the reference generator. To completely eliminate the negative half-wave, without changing the average value of the feedback voltage, it is possible by reducing the number of turns of the additional winding 5 droplets 3.

Additional windings of chokes and transformers are not power and can be wound with a thin wire, so they practically do not change their weight and dimensions. The best results are achieved with an additional biphil winding with an appropriate power winding. However, winding technology can be simplified. So, when winding additional windings of a transformer, one of them can be wound directly onto the core, and the second over all the others.

The structural scheme of the proposed converter is of the sixth order if the transformer is considered a second order link. nosToiviy to achieve stable operation of the converter by known means, subject to adjustment directly at the output voltage, is very difficult and is associated with carrying out time-consuming calculations of corrective links and their subsequent debugging.

The proposed converter is less than these disadvantages, since the order of the system is reduced by means of additional windings connected in a certain way. By supplying an integrating chain to the control unit for smoothing: the feedback pulse voltage, a first order control system can be obtained. Since filters and parasitic pars (transformer meters are turned out to be out of control.

then their parameters can be chosen by any, having finished, for example, the required smoothing of the output voltage. A large margin on the stability of the converter allows the use of a frequency-phase control principle that turns the converter into an astatic system. The wiring diagram of the control unit with the output of the converter, despite the introduction of additional windings and wipers, is simplified, since no complicated corrective links are required.

Claims (3)

1. The patent of England No. 1034206, cl. H 2 F, 1966. 2. Moin B.C., Laptev N.N. Stabilized transistor converters. Energy, 1972, p. 418, rice 11-1. 3. Authors certificate of the USSR 386388, cl. G 05 F 1/20, 1970.