RU2267218C1 - Constant voltage transformer - Google Patents

Abstract

FIELD: transforming equipment engineering, can be used as transformer of constant voltage to constant voltage for secondary power systems.

SUBSTANCE: constant voltage transformer has key amplifier, electric power buses of which are connected to primary voltage buses, set-point generator connected by direct and inversed outputs accordingly to first and second inputs of key amplifier, output of which through serially connected throttle and capacitor is connected to middle point of capacity splitter, while in parallel to capacitor primary winding of transformer is connected, secondary winding of which through rectifier and capacity filter is connected to secondary voltage buses. Device additionally has first and second switch-on delay circuits, first and second diodes and second capacity splitter, connected between primary voltage buses and connected by middle point to output of key amplifier, first and second inputs of which through first and second switch-on delay circuits are connected to direct and inverse outputs of set-point generator, while first and second diodes are connected serially via back conductivity between primary voltage buses, and middle point of diodes connection is connected to point of connection of throttle and capacitor. Also provided is circuit of constant voltage transformer, operating for multi-channel load.

EFFECT: increased stability of loading characteristics due to implementation of additional recuperative diodes (diodes, through which process of returning of accumulated energy of power source back into power source occurs), and also better quality characteristics of secondary voltages by means of providing of quasi-resonance trajectory of alteration of output voltage of key amplifier, which is especially important during operation of device for multi-channel load.

2 cl, 6 dwg

Description

The invention relates to a conversion technique and can be used as DC to DC converters 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]. Unlike a wide class of controlled and stabilized sources of secondary power supply, the TPN group combines uncontrolled converters that provide 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). The composition of known devices includes a key power amplifier, the power bus of which is connected to the primary voltage buses, the control inputs are connected to the outputs of the master oscillator, and the outputs are connected to the primary winding of the transformer, the secondary windings of which are connected through the rectifier and output filter to the secondary voltage buses [2, 3].

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 well-known transformer transformers 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 SSCs are stable load characteristics in the conditions of changing the output current over a wide range, however, the highlighted advantage is associated with a loss of stability in starting conditions when working on a capacitive filter, as well as with current overload and short circuit 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 into secondary voltage buses, which worsens the quality characteristics of the output voltages of known SSCs and prevents their use in functional equipment with increased requirements of electromagnetic compatibility (EMC).

The technical solution closest to the one proposed in terms of the essential features is the WBC described in article [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.

TPN - prototype (figure 1) contains a master oscillator 1, a key power amplifier 2, made on key elements 2.1, 2.2, included in a half-bridge circuit, a choke 3, a capacitor 4, a capacitive divider 5, a transformer 6, a rectifier 7 and an output capacitive filter 8.

The advantage of the half-bridge circuit implemented in the TPN prototype is the use of capacitors of a capacitive divider 5 both as a filter by supply voltage and as a separation for transformer 6, which is equivalent to the formation of voltage + E and -E at the output of the voltage factor equal to half the primary voltage power supply E _about .

In the known device (Fig. 1), the power supply lines of the KUM 2 and the capacitive divider 5 are connected in parallel to the primary voltage buses, the control inputs of the KUM 2 are connected to the outputs of the master oscillator, and the output is connected through a series-connected inductor 3 and the primary winding of the transformer 6 to the midpoint of the capacitive divider 5, in turn, the primary winding of the transformer is connected in parallel with the capacitor 4, and the secondary winding is connected in series with the rectifier 7 and the output capacitive filter 8 is connected to the bus secondary voltage.

The work of the TPN prototype is as follows. The master oscillator 1 generates two antiphase impulse signals of the meander type arriving at the control inputs of the key elements 2.1, 2.2 of the KUM 2. As a result, the output of the KUM 2 generates a symmetrical pulse voltage of amplitude E = E _о / 2, which is fed to the input of a resonant filter made on the inductor 3 and capacitor 4. The voltage across capacitor 4 is varied along a smooth path determined by the resonant frequency

where L is the inductance of the inductor 3, C _P is the capacitance of the capacitor 4.

When the voltage on the capacitor 4 rises to the level of U _n · K _T (where K _T is the transformation coefficient of the transformer 6, U _n is the output voltage at the load), the current i _{L of the} inductor 3 closes through the transformer 6, diodes of the rectifier 7 and the output capacitive filter 8 v load. Switching the key elements of KUM 2 provides a change in current i _L , a recharge of the capacitor 4 and the formation of another half-wave voltage at the inputs of the rectifier.

The advantage of the TPN prototype is the formation of a trapezoidal (quasi-sinusoidal) voltage on the primary winding of the transformer, which leads to improved EMC characteristics. However, the change in voltage at the output of the CMC is pulsed in nature, the rate of change in voltage, as in the known devices [1-3], reaches 1000 V / μs. Accordingly, in the TPN prototype, the conductive transfer of pulsed RF interference to the secondary voltage buses is observed, which is a disadvantage of the TPN.

The advantage of the prototype device [4] in comparison with the known TPN [1-3] is also the stable operation in current overload and short circuit modes. Indeed, the presence of a choke 3 at the output of the KUM provides a limitation of the output current, the amplitude of which in the short circuit mode does not exceed the value

where ω _n = 2πf _n is the switching frequency of the KUM, L is the inductance of the inductor 3, E ₀ is the supply voltage.

Thus, without current overload, starting conditions can be ensured and the device operates on a load with a resistance less than the rated one up to and including a short circuit.

However, the TPN prototype has low stability of load characteristics. With increasing load resistance, the output voltage increases. In the mode close to idling in the elements of the resonant circuit (inductor 3, capacitor 4) and the key elements of KUM 2, an uncontrolled increase in current is observed, leading to failure of amplification devices.

When used in multi-channel power supply systems, the low stability of the output voltages of the TPN-prototype can lead to the dependence of the secondary voltages of individual consumers on the load of other consumers, which is unacceptable and limits the scope of TPN.

The objective of the present invention is to increase the stability of the load characteristics of the WBC while improving the quality characteristics of the output secondary voltages.

To solve the problem in the well-known TPN containing a key amplifier, the power bus of which is connected to the inputs of the first capacitive divider and to the primary voltage buses, a master oscillator connected by a direct and inverse output, respectively, to the first and second input of the key amplifier, the output of which is through a series-connected inductor and the capacitor is connected to the midpoint of the capacitive divider, and in parallel with the capacitor is connected the primary winding of the transformer, the secondary winding of which is A rectifier and a capacitive filter are connected to the secondary voltage rails, new features are introduced, namely the first and second switching delay circuit, the first and second diodes and the second capacitive divider connected between the primary voltage rails and connected by the midpoint to the output of the key amplifier, the first and second whose inputs through the first and second switching delay circuits are connected to the direct and inverse output of the master oscillator, while the first and second diodes are connected in series with the reverse conductivity of the bus and the primary voltage, and the average point of connection of diodes connected to the throttle point connection and a capacitor.

For a multi-channel load, where a number of secondary voltage groups are formed for several individual consumers, n additional chokes and n additional capacitors, n additional capacitive dividers and n additional transformers, each of which contains one primary and k secondary windings, are introduced into the declared FCL N = kn additional rectifiers and N additional capacitive filters, and n additional chokes and capacitors are connected between the output of the key amplifier and the midpoints s corresponding to n additional capacitive dividers, the inputs of which are connected to the buses of the primary voltage. In turn, the primary windings of n additional transformers are connected in parallel with the corresponding n additional capacitors, a k of the secondary windings of each of n additional transformers are connected through the corresponding series-connected additional rectifiers and capacitive filters to the buses N of the secondary output voltages.

The technical results from the use of the invention are to increase the stability of the load characteristics due to the use of additional regenerative diodes (through which the process of closing the inductor self-induction current to the capacitive filter is carried out, which ensures the return of the excess energy of the resonant filter), as well as improving the quality characteristics of the secondary voltages by providing a quasi-resonant change path the output voltage of the key amplifier, which is especially important when working on a multi-channel transformer total load.

The invention is illustrated in figures 1-5, where figure 1 shows the structural diagram of the WBC prototype, figure 2 is a structural diagram of the proposed WBC, figure 3 is a structural diagram of the WBC for multi-channel load, figure 4 is a timing diagram signals explaining the principle of operation of the claimed technical solution, Fig.5 is a spectrogram of the noise of the amplifiers, brought to their inputs, when the equipment is powered from the TPN prototype (Fig.5a) and from the proposed TPN (Fig.5b).

The proposed WBC (Fig. 2) contains a master oscillator 1, a key power amplifier 2, made on two key elements 2.1, 2.2, a choke 3, a capacitor 4, a first capacitive divider 5, a transformer 6, a rectifier 7, a capacitive filter 8, and also circuits 9, 10 turn-on delays performed on RD circuits, a second capacitive divider 11, and regenerative diodes 12, 13.

The multi-channel SSC for multi-channel load, shown in Fig. 3, contains a master oscillator 1, turn-on delay circuits 9, 10, a key power amplifier 2, a first capacitive divider 5, a second capacitive divider 11, and also n + 1 channels of quasi-resonant transformer-rectifier devices , each channel i (where i = 1 ... n + 1) contains a inductor 3i, a capacitor 4i, diodes 12i, 13i and a transformer 6i with one primary and k secondary windings, as well as k rectifiers 7.il..7.ik and k capacitive filters 8.ik

The proposed SCC scheme provides the formation of n + 1 groups of k secondary voltages U.i.l ... U.i.k with high stability under conditions of load changes over a wide range.

The work of the proposed WBC is as follows. The master oscillator 1 generates two antiphase pulsed signals that, through the on-delay circuits 9, 10, are supplied to the inputs of the controlled key elements 2.1, 2.2. Schemes 9, 10 are performed on RD-circuits (Fig. 2), providing a smooth increase in the front of control voltages U ₁ , U ₂ at the inputs of key elements 2.1, 2.2 and their quick shutdown when forming a pulse decline. Thus, in the proposed WBC, a turn-on delay τ ₃ is realized, during which the key elements 2.1, 2.2 are simultaneously in the closed state. In this case, the trajectory of the change in V of the output voltage of the KUM 2 is formed by recharging the capacitors of the divider 11 with the current of the inductor 3. Then, the inductor current changes direction and the capacitor 4 is recharged to voltage E, at which the regenerative diodes 12 or 13 open. At the same time, the voltage amplitude on the primary winding remains unchanged for load resistance in the range of R _n > R ₀ from the nominal value to idle. Accordingly, the constancy of the rectified secondary voltage is maintained.

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

The boundary mode of operation at maximum output power is provided when the equality R _n = R ₀ . In this case, all the energy stored in the inductor 3 during the recharging of the capacitor 4 is transferred to the load minus the energy sufficient to recharge the capacitors of the divider 11.

For each half-cycle of the device, you can select the time t ₁ , t ₂ , t ₃ , t ₄ , t ₅ (figure 4) and the corresponding time intervals that determine the operation of the circuit,

Δt _1.2 is the time interval for the recharge of the total capacity With _{about the} capacitors of the second capacitive divider 11;

Δt _2.3 - conduction time of reverse diodes of key elements 2.1 or 2.2;

Δt _3.4 is the time interval for the recharge of the capacitance C _{p of the} capacitor 4;

Δt _4.5 - current flow time through transistors of key elements 2.1 or 2.2.

The formation of a quasi-resonant switching trajectory is possible under two conditions. Firstly, the inductance energy L of the inductor 3 at the time the conductive key element is turned off and corresponding to the maximum I _m output current of the CMC must be sufficient to change the voltage across the capacitance C _о by 2E

Secondly, the delay time τ ₃ should be sufficient to recharge the capacitance C _o and not exceed the conductivity time of the reverse diodes of the key elements 2.1, 2.2

Δt _1.2 ≤τ ₃ ≤Δt _1.2 + Δt _2.3

Under these conditions, the rate of change of the output voltage KUM 2 does not exceed the value

The recharge time of the capacitor 4 in the proposed device, corresponding to a quasi-harmonic change in voltage U _s (Fig. 4), is

где

Where

The maximum amplitude i _L (Fig. 4) of the output current of the KUM 2 in the nominal mode corresponding to the maximum output current i _{M of the} rectifier is determined by the expression

где

Where

When choosing the circuit parameters from the conditions for obtaining the characteristic frequency ω _o = (2-3) ω _p for the switching frequency ω _p = 2π / T (T is the switching period) equal to ω _p = (0.3-0.5) ωp, provides a change in the amplitude of the output current of KUM 2 by no more than 20-30% in a wide range of load changes from short circuit mode to idle mode (XX).

For the load range from R _n to XX in the proposed device provides a constant secondary voltage, the value of which is determined by the primary voltage E _and the transformation ratio of the transformer 6 U _n = K _τ E.

In turn, the use of on-delay circuits 9, 10 in combination with the inclusion of a capacitive divider 11 makes it possible to ensure smooth trajectories of voltage changes in all elements of the circuit. This achieves the practical elimination of conductive RF interference, penetrating the secondary voltage busbars through the passage capacitance of the electromagnetic elements and stray volumetric capacitance of the supporting structure of the device.

The analysis of the proposed device confirms the solution to the problem of increasing the stability of the load characteristics of the transformer substation while improving the quality indicators of the output secondary voltages by introducing a new set of essential features.

The conducted experimental studies revealed the advantages of the claimed technical solution of the WBC in comparison with analogues and prototype. In the prototype device, when the load changes in the range from the nominal value R _n = R _o to R _n = 10 R _{0, the} secondary voltage changes more than twice, and the amplitude of the RF pulsation reaches 1%. In the proposed device under the same conditions, the change in the secondary voltage does not exceed 10% with a sweep of RF pulsations of less than 0.2%. Moreover, the proposed device provides stable operation in current overload and short circuit modes.

The indicated advantages of the CTN circuit can be effectively used in multichannel secondary power supply systems, which provide the formation of secondary voltages for various consumer groups with different operating modes.

The advantage of the circuit of figure 3 is the lack of influence of current overload modes, possible in one of the n groups of output voltages, on the formation of other groups of secondary voltages. This characteristic of multi-channel WBC is a prerequisite for its use in multifunction devices with a large number of consumer groups. The set of newly introduced blocks and connections provides a solution to the problem of expanding the functionality of the proposed WBC with improved EMC and increasing the stability of load characteristics.

To test the technical advantages of the proposed device in comparison with the well-known TPN, experimental samples of multichannel IVEP (secondary power supply sources) were made according to well-known schemes [1-3] and according to the proposed scheme (figure 3).

The experimental samples were used to power the receiving equipment of hydroacoustic broadband systems with a frequency band from hundreds of Hz to tens of kHz. Investigations were made of the intrinsic noise brought to the input of the receiving amplifiers when the equipment was powered from various types of external power sources. The measurement results of spectrograms for two power options are presented in figa, b. Analysis of the measurement results shows that the intrinsic noise of the receiving equipment during power supply from the proposed WBC (Fig.5b) is significantly (more than 20 dB) less than when powered from known WBC. In the noise spectrum (Fig.5b) there are practically no (less than 0.1 μV) components of the switching frequencies (50-60 kHz), and the components in the working frequency band of the receiving equipment do not exceed 0.2 μV. When power is supplied from a known device in the operating frequency band, the noise reaches 10 μV, and the switching frequency components reach 50 μV. Accordingly, the improvement of the EMC characteristics of the proposed technical solution TPN can significantly improve the characteristics of the receiving equipment.

Thus, the testing of the proposed and well-known technical solutions has confirmed the undoubted advantages of the claimed device, which can be proposed for use for power supply of multifunctional equipment with increased requirements for the quality of the secondary voltage supply.

SOURCES OF INFORMATION

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

2. Copyright certificate No. 1603511, MKI N 02 M 7/538. Push-pull transistor converter / V.A.Alexandrov et al., Publ. in BI No. 40 dated 10.30.90

3. Copyright certificate No. 1628191, MKI N 03 K 5/02. Push-pull converter / V.A.Alexandrov et al., Publ. in BI No. 6 of 02.15.91

4. Switching power supplies: development trends / J. Basset. Electronics, 1988, No. 1, pp. 71-77.

Claims (2)

1. A DC voltage converter containing a key amplifier, made on two key elements connected in a half-bridge circuit, the power bus of which is connected to the inputs of the capacitive divider and to the primary voltage buses, the master oscillator, the output of the key amplifier through a series-connected inductor and capacitor is connected to the middle point of the first capacitive divider, and in parallel with the capacitor is connected the primary winding of the transformer, the secondary winding of which is through the rectifier and capacitor the remaining filter is connected to the secondary voltage buses, characterized in that the first and second switching delay circuits, the first and second diodes and the second capacitive divider are connected between the primary voltage buses and connected by a midpoint to the output of the key amplifier, the first and second inputs of which are through the first and the second switching delay circuit are connected to the direct and inverse output of the master oscillator, while the first and second diodes are connected in series with reverse conductivity between the primary voltage buses And average point of connection of diodes connected to the throttle point connection and a capacitor. 2. The converter according to claim 1, characterized in that n additional chokes and n additional capacitors, n additional capacitive dividers and n additional transformers are introduced, each of which contains one primary and k secondary windings, as well as N = kn additional rectifiers and N additional capacitive filters, and n additional chokes and capacitors are connected between the output of the key amplifier and the midpoints of the corresponding n additional capacitive dividers, the inputs of which are connected to the buses of the primary conjugation, the primary winding n additional transformers are connected in parallel respective n additional capacitor, and k secondary windings of each of the n power converters are connected through respective series-connected rectifiers and additional capacitor filters to tires N of the secondary output voltages.

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