RU2583761C1 - Dc voltage transformer - Google Patents

Abstract

FIELD: instrument engineering.

SUBSTANCE: invention can be used as converter of constant voltage for secondary power systems. Proposed stabilizer-constant-voltage transformer (CVT) differs from technical analogues and CVT prototype product by ensuring stability of output voltage at voltage supply fluctuations. Proposed stabilized constant voltage transformer also includes signal winding of transformer, an additional rectifier, capacitor filter, amplifier of difference signal, and driving generator controlled by frequency and control input is connected to amplifier output difference signal, the first input is connected to bus of reference voltage, and the second input is connected via a capacitive filter and an additional rectifier to signal winding of transformer.

EFFECT: technical result of invention consists in stabilization of output voltage securing against the effect of destabilising factors associated with change of load and voltage supply.

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Description

The invention relates to a conversion technique and can be used as a DC to DC converter for secondary power systems.

Known transformers of constant voltage (CT), designed to convert a constant voltage of the primary network into a constant voltage of one or more sources of the secondary network [1]. TPN provides galvanic isolation and transformer coordination of primary and secondary voltages.

The basis of the SSC implementation is an inverter that converts the primary DC voltage to alternating voltage, which is transformed to the required values and rectified, forming sources with specified secondary voltages.

Known SPSs can use inverters with external excitation made according to push-pull [2] or half-bridge [3] circuits of transistor key power amplifiers (KUM).

Using a key operating mode and a high switching frequency (tens and hundreds of kHz) of KUM transistors can increase the conversion efficiency and significantly reduce the weight and dimensions of the known transformer substations compared to power transformers of industrial frequency (50 Hz). The external control of KUM transistors made according to well-known schemes [2, 3] is carried out from the master oscillator by antiphase square wave signals. As a result, a symmetrical pulse voltage is formed on the primary and secondary windings of the transformer, which ensures the formation of secondary voltages with the minimum dimensions of the output filters.

The advantages of the well-known high voltage transformers are stable load characteristics under conditions of changes in the output current over a wide range.

At the same time, the highlighted advantage is associated with the loss of stability of operation in starting conditions when working on a capacitive filter, as well as with current overload and short circuit of the load. Another disadvantage of the known devices is the increased level of high-frequency (HF) interference associated with the pulse formation of the fronts of the output voltage and the interruption of the current paths. In KUM elements with a typical power of 100 to 1000 W, loaded directly on the output transformer, there is a change in potentials with a speed of more than 1000 V / μs when the current changes by more than 100 A / μs. Such pulsed processes lead to conductive and inductive RF interference penetrating the secondary voltage buses, which degrades the quality characteristics of the output voltages of the known SSCs and prevents their use in functional equipment with increased requirements of electromagnetic compatibility (EMC).

The technical solution closest to the proposed solution in terms of the essential features is the WBC described in RF patent No. 2267218 [4]. In the TPN prototype, the disadvantages of the known devices are eliminated by introducing a resonant circuit containing a inductor connected at the output of the KUM and a capacitor connected in parallel with the primary winding of the transformer. Thus, a resonant type inverter is implemented in the CTL, which provides improved EMC characteristics and stability in the current overload and short circuit mode. The composition of the known device includes a key power amplifier, the power bus of which is connected to the primary voltage buses, a master oscillator connected by direct and inverse outputs to the first and second inputs of the key power amplifier, the outputs of which are connected to a choke and a capacitor connected in series, and a primary is connected in parallel to the capacitor transformer winding, the secondary winding of which is connected through the rectifier and the output filter to the secondary voltage buses, the first and second diodes are connected by reverse conductivity in series between the primary voltage buses, and the midpoint of the diode connection is connected to the connection point of the inductor and capacitor [4]. The block diagram of the prototype device is shown in FIG. 1, and in FIG. 2 shows the timing diagrams.

TPN prototype (Fig. 1) contains a master oscillator. 1, key power amplifier 2, inductor 3, capacitor 4, transformer 5, rectifier 6, output filter 7, first and second regenerative diodes 8, 9.

The advantage of the circuit implemented in the TPN prototype is the use of regenerative diodes 8, 9 in conjunction with a choke 3 and a capacitor 4 to increase the stability of the converter when the load parameters change over a wide range under the conditions of implementation of “soft” current and voltage switching paths.

The work of the TPN prototype is as follows.

The master oscillator 1 generates two antiphase pulsed signals, which are fed to the control inputs of the CMC 2. If necessary, to exclude through currents through the key elements of the CMC 2, a delay of the front of the output pulse signals can be implemented in the master oscillator 1. Thus, the delay T _{3 of the} switch-on is realized, during which the key elements of the CMC 2 are simultaneously in the closed state. In this case, the path of the change in the input voltage KUM 2 (Fig. 2) is formed by recharging its own output capacitance and the current of the inductor 3. Then, the inductor current i _L changes direction and the capacitor 4 is recharged to voltage V, at which the regenerative diode 8 or 9 opens. this, the amplitude of the voltage on the primary winding remains virtually unchanged for the load resistance in the range R _H > R ₀ from the nominal value to idle. Accordingly, in this range, the relative constancy of the rectified secondary voltage is maintained under conditions of a change in the output current i _{B of the} rectifier.

In the case of overload when the load resistance R _H decreases from the nominal value R ₀ to a short circuit, the output voltage decreases from the condition of maintaining the maximum amplitude of the output current.

However, TPN-prototype does not provide stabilization of the output voltage when changing the magnitude of the primary voltage. Since the output voltage is determined by the magnitude of the primary voltage E (taking into account the ratio of the turns of the transformer), all changes in the magnitude of the voltage of the primary power supply lead to a proportional change in the output voltage. A change in the magnitude of the load parameters also leads to a change in the magnitude of the output voltage with instability by the load characteristic of the prototype device of the order of 10%.

The objective of the present invention is to increase the stability of the output voltage of the ESRD under destabilizing factors associated with changes in the load and voltage.

To solve this problem, in a known FCN containing a key amplifier, the power bus of which is connected to the primary voltage buses, a master oscillator connected by direct and inverse outputs respectively to the first and second inputs of the key amplifier, the output of which is connected in series to the inductor and capacitor, and in parallel the primary winding of the transformer is connected to the capacitor, the secondary winding of which is connected through the rectifier and the output filter to the buses of the secondary output about the voltage, as well as the first and second diodes connected by reverse conductivity in series between the primary voltage buses, and the middle point of the diode connection is connected to the connection point of the inductor and capacitor, new features are introduced into the proposed stabilized DC voltage transformer, namely, the signal winding of the transformer, additional rectifier, capacitive filter, differential signal amplifier, and the master oscillator is frequency-controlled and connected to the control input by the output a differential signal amplifier, the first input of which is connected to the reference voltage bus, and the second input is connected through a capacitive filter and an additional rectifier to the signal winding of the transformer.

The technical result from the use of the invention is the stabilization of the output voltage from the influence of destabilizing factors associated with changes in the load and voltage.

The invention is illustrated in FIG. 3 and FIG. 4, where in FIG. 3 shows the structural claimed TPN, in FIG. 4 timing diagrams of signals explaining its principle of operation.

The proposed WBC (Fig. 3) contains a controlled master oscillator (UGG) 1 with a control input, key power amplifier 2, inductor 3, capacitor 4, transformer 5 with primary 5.1, secondary 5.2 and additional signal winding 5.3, rectifier 6, output filter 7 , regenerative diodes 8, 9, an additional rectifier 10, a capacitive filter 11, a difference signal amplifier 12.

The work of the proposed WBC is as follows.

The controlled master oscillator 1 generates two antiphase pulse signals supplied to the control inputs of KUM2. In UZG1, a delay of the edges of the out-of-phase pulsed signals is implemented for a time T _s , during which the KUM2 transistors are simultaneously in the closed state. In this case, the path of the change in the output voltage KUM 2 is formed by recharging its own output capacitance with the current of the inductor 3. Taking into account T _{s the} current of the inductor i _L , the voltage on the primary winding 5.1 of the transformer 5 V and the output current of the rectifier 6 i _B for a given supply voltage E ₀ will have the view shown in FIG. 4. From the drawing it can be seen that with constant delay times T _s and the trajectory of the change in V of the output voltage, the constant component of the rectified voltage V ₀ will depend on the conversion frequency. Moreover, with an increase in the switching frequency, a decrease in the output voltage can be achieved. This property is used to stabilize the output DC voltage in the proposed WBC. To do this, the voltage of the signal winding 5.3 of the output transformer 5 is supplied to an additional rectifier 10 and a capacitive filter 11. From the output of the filter, a constant feedback voltage U _{oc is} supplied to the difference signal amplifier 12, to the other input of which a reference voltage U _op is supplied. The difference signal U _p = U _о -U _{oc is} supplied to the control input of the master oscillator 1, which, under its influence, changes the operating frequency and, accordingly, the output voltage so that the difference signal tends to a zero value. Thus, the output DC voltage is stabilized under the influence of various destabilizing factors both when the supply voltage changes and when the load changes.

The output voltage U _n is determined by the value of the rectifier current i _{B cf} averaged over the switching period at a given load resistance.

U _n = i _{B cf.R n} .

- резонансная частота элементов 3 и 4) может быть обеспечена характеристика регулирования выходного тока выпрямителя от нуля до номинального значения i_вн в условиях изменения напряжения электропитания в 1,5 раза. Глубина обратной связи в предлагаемом устройстве достигает 30 дБ, что позволяет уменьшить изменение выходного напряжения до 3-5% в условиях повышения напряжения электропитания на 50% и уменьшении выходного тока i_{в ср} в 10 раз. В результате в предлагаемом ТПН достигается стабилизация нагрузочных характеристик выходного напряжения в 3-4 раза лучше, чем в ТПН-прототипе при сохранении мягких траекторий переключения контуров токов и потенциалов импульсных напряжений, а также условия ограничения тока выходного тока в режимах перегрузки.Providing changes in the frequency ω of the output signals of a controlled master oscillator in the range ω = 0.6 ÷ 1.5ω _p (where $${\omega }_p=\mathrm{one}/\sqrt{LC}$$

- the resonant frequency of the elements 3 and 4) can be provided with the characteristic of regulation of the output current of the rectifier from zero to the nominal value i _vn under conditions of a change in the supply voltage by 1.5 times. Feedback depth is 30 dB in the proposed device, which allows to reduce the output voltage up to 3-5% in a voltage increase power to 50% and a decrease _in the output current i _Wed 10 times. As a result, stabilization of the load characteristics of the output voltage is achieved 3-4 times better in the proposed TPN than in the TPN prototype while maintaining soft switching paths of the current circuits and potentials of pulsed voltages, as well as the conditions for limiting the output current current in overload conditions.

When the supply voltage changes, the proposed stabilized TPN compares favorably with technical analogues and the TPN prototype by ensuring the stability of the output voltage. So, if in the known TPN, when the supply voltage changes by 50%, the output voltage changes in a similar way, then in the proposed device, the change in the output voltage under these conditions does not exceed 5%.

Developed and manufactured prototypes of stabilized WPS with an output power of 20 ÷ 100 W, the test results of which confirmed the indicated advantages of the claimed technical solution, which allows recommending its implementation in secondary power supply systems.

INFORMATION SOURCES

1. R. Severne, G. Bloom. "Pulse DC-DC converters for secondary power supply systems" - M .: Energoatomizdat, 1988 - 294 p.

2. Copyright certificate of the USSR No. 1603511, MKI N02M 7/538. Push-pull transistor converter / V.A. Alexandrov et al., Publ. in BI No. 40 dated 10.30.90

3. USSR author's certificate No. 1628191, MKI N03K 5/02. Push-pull converter / V.A. Alexandrov et al., Publ. in BI No. 6 of 02.15.91

4. RF patent No. 2267218, MKI H02M 3/337. DC voltage transformer / V.A. Alexandrov et al., Publ. BI №36 12/27/2005

Claims (1)

A DC voltage transformer containing a key amplifier, the power bus of which is connected to the primary voltage buses, a master generator connected by direct and inverse outputs to the inputs of the key amplifier, the output of which is connected in series to the inductor and capacitor, and the transformer primary winding is connected in parallel with the capacitor, the secondary winding which through the rectifier and the output filter is connected to the buses of the secondary output voltage, as well as the first and second diode s, connected by reverse conductivity in series between the primary voltage buses, and the middle point of the diode connection is connected to the connection point of the inductor and capacitor, characterized in that it includes a signal transformer winding, an additional rectifier, a capacitive filter, a differential signal amplifier, and a master oscillator controlled by frequency and connected by a control input to the output of a difference signal amplifier, the first input of which is connected to the voltage reference bus, and the second input is connected to A capacitive filter and an additional rectifier to the signal winding of the transformer.

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