EP0886200A2 - Circuit arrangement for generating a load-independent DC voltage - Google Patents

Abstract

The circuit arrangement includes a first rectifier arrangement (GL1) with an AC voltage connection (EK1, EK2) and two output terminals (AK1, AK2), and a current regulator arrangement (SRA) connected to the output terminals of the first rectifier arrangement. A second rectifier arrangement is connected to two output terminals (AK3, AK4) of the current regulator arrangement, which provides an output voltage (Ua) at two output terminals (AK5, AK6). A voltage measurement arrangement (MA) is connected to the output terminals of the second rectifier arrangement to provide a voltage signal (SS) at its output. A feedback branch includes a regulator arrangement (RA) with an integrator arrangement (IN) for feeding the voltage signal to an input terminal (EK) of the current regulation arrangement. A function generator is arranged in the feedback branch in connection to the regulator arrangement. The function generator provides an output signal (y) from an input signal (x), according to a predetermined function (y=f (x) ), whereby the functions increases at least partially with increasing input signal.

Description

• einer ersten Gleichrichteranordnung mit einem Wechselspannungsanschluß und zwei Ausgangsklemmen;
• einer an die Ausgangsklemmen der ersten Gleichrichteranordnung angeschlossenen, zwei Ausgangsklemmen aufweisenden Stromregelanordnung zur Regelung der Netzstromaufnahme;
• einer an die Ausgangsklemmen der Stromregelanordnung angeschlossenen zweiten Gleichrichteranordnung mit Ausgangsklemmen, an denen eine Ausgangsspannung abgreifbar ist;
• einer an die Ausgangsklemmen der zweiten Gleichrichteranordnung angeschlossenen Spannungsmeßanordnung zum Bereitstellen eines Spannungssignals an einem Ausgang;
• einem Rückkopplungszweig mit einer eine Integrieranordnung aufweisenden Regelanordnung zur Rückkopplung des Spannungssignals an eine Eingangsklemme der Stromregelanordnung.

The present invention relates to a circuit arrangement for generating a load-independent DC voltage with the following features:

• a first rectifier arrangement with an AC voltage connection and two output terminals;
• a current control arrangement connected to the output terminals of the first rectifier arrangement and having two output terminals for regulating the mains current consumption;
• a second rectifier arrangement connected to the output terminals of the current control arrangement and having output terminals from which an output voltage can be tapped;
• a voltage measuring arrangement connected to the output terminals of the second rectifier arrangement for providing a voltage signal at an output;
• a feedback branch with a control arrangement having an integrating arrangement for feedback of the voltage signal to an input terminal of the current control arrangement.

Task of such circuit arrangements, in particular in Switching power supplies are used as output voltage a DC voltage for connectable to the output terminals To provide consumers with the Output voltage their value for load changes within a Prescribable area should maintain.

A load change occurring at the output terminals is required with constant mains voltage, a change in regulated by the current control arrangement, in particular sinusoidal Power consumption. That leaves the power consumption and thus the power consumption is initially the same when the load changes a change in the output voltage. This change will registered by the voltage measuring arrangement and as a voltage signal via the feedback branch to the current control arrangement fed back, depending on the current consumption there readjust from the load change to the output voltage reached the specified value again. For feedback more inevitable, especially when using simpler second rectifier arrangements of fluctuations occurring the output voltage to avoid the given value, is usually one in such circuit arrangements Integration of the voltage signal in the control arrangement of the Feedback branch provided. Usually caused by one large integration time constant become load changes and thus changes in the output voltage are delayed the current control arrangement fed back, the readjustment of the Current change is therefore relatively sluggish.

A change in the current consumption is also in the event of a change the mains voltage, which must then be taken into account in particular is when the circuit arrangement in so-called Wide range power supplies are used, which is a constant Output voltage for input voltages between should deliver approx. 90V and 265V. If the input voltage changes, the mains current consumption initially changes proportionally to the voltage change while moving through the circuit arrangement absorbed and output power changes quadratically depending on the voltage change. Becomes the current consumption is not initially adjusted, so the Output voltage, for example, initially when the mains voltage is reduced from, this change by the voltage measuring arrangement registered and as an integrated voltage signal via the Feedback branch fed back to the current measuring arrangement becomes.

The current consumption is both when the load changes and when Change in the mains voltage until the Output voltage set again to the specified value Has.

The current consumption is regulated in the current regulating arrangement using a control loop that has a rated Mains voltage signal is supplied, the current consumption proportional to this signal. Usually the rated mains voltage signal is generated by multiplying one at the input terminal of the current control arrangement control signal present with a direct from the line voltage dependent line voltage signal.

If, for example, the same load is applied to the output terminals Output voltage and thus the output power be maintained if the mains voltage is halved, so it is necessary to double the original power consumption, d. H. the mains voltage signal is by the factor rate four to achieve a current draw that twice the original power consumption. The control signal present at the input terminal of the current control arrangement is thus quadratic dependent on the mains voltage, the smaller the mains voltage, the greater the signal is.

Same load changes at the output terminals of the current control arrangement cause equal voltage changes in the output signal, while a signal change at the input terminal is required, which depends on the mains voltage. A change of the signal present at the input terminal must be proportional to the load change, d. H. the control signal must halve if, for example, the load is halved. Since the Signal swing of the voltage signal depends only on the load Signal swing of the at the input terminal of the current control arrangement control signal is dependent on the mains voltage readjustment of the output voltage is required same load change at the output for different times different mains voltages. So the for nine times the adjustment takes the time required when reducing the input voltage by a third with the same load change.

In order to avoid this problem, a known one is used Circuit arrangement when forming the evaluated mains voltage signal the root mean square of the mains voltage taken into account, the averaging using a multi-pole Low pass filter takes place, which is very expensive.

In another known circuit arrangement is a changeover switch provided an additional evaluation of the mains voltage signal in a ratio of 1: 4, this Evaluation only for two different input voltages, usually 120V and 240V is exact.

The aim of the present invention is to provide a circuit arrangement to generate a load-independent DC voltage for To make available, with a readjustment of the output voltage regardless of the load and at least approximately regardless of the mains voltage.

einen der Regelanordnung in dem Rückkopplungszweig nachgeschalteten Funktionsgenerator, der ein von einem Eingangssignal gemäß einer Funktion y=f(x) abhängiges Ausgangssignal erzeugt, wobei die Ableitung der Funktion f(x) von dem Eingangssignal abhängig ist und wobei die Ableitung wenigstens abschnittsweise mit wachsendem Eingangssignal zunimmt.

This goal is achieved by a circuit arrangement mentioned at the outset, which has the following additional feature:

one of the control arrangement in the feedback branch downstream of the function generator, the one of an input signal according to a function y = f (x) dependent output signal is generated, the derivative of the function f (x) being dependent on the input signal and the derivative increasing at least in sections with an increasing input signal.

The output signal of the function generator, which is fed to the current control arrangement at its input terminal for evaluating the mains voltage signal, is in accordance with y = f (x) depending on a signal supplied by the integration arrangement, which in turn depends on the voltage signal. Due to the increasing slope of the function f (x) at least in sections, the same changes in the input signal result in absolute changes, the greater the changes in the output signal, the greater the value of the output signal. Changes in the voltage signal when the load connected to the output terminals of the circuit arrangements changes, thus have an effect on this signal present on the input terminal depending on the value of the signal applied to the input terminal. The control signals present at the input terminal for different line voltages are still quadratically dependent on the respective line voltage, but these signals are changed with the same load change due to the function generator depending on their absolute value. The influence of the mains voltage, on which the value of the control signal depends, on the period of time required to readjust the current consumption is thus considerably reduced.

The function generator is advantageously selected such that it at least approximately corresponds to the output signal y = c.a bx generated from the input signal. The output signal of the function generator, which is fed to the current control arrangement at its input terminal for evaluating the mains voltage signal, is thus exponentially dependent on the signal supplied by the integration arrangement, which in turn depends on the voltage signal. Changes in the voltage signal when the load connected to the output terminals of the circuit arrangements changes have an exponential effect on the control signal applied to the input terminal. The control signals applied to the input terminal for different line voltages are quadratic dependent on the respective line voltage, however, these signals are changed with the same load change due to the function generator with exponential transfer function proportional to its absolute value. In this embodiment, the regulation of the mains current consumption takes place independently of the load and the mains voltage.

Depending on the load range to be regulated, there is the possibility of rationalizing the exponential function in the required section y = f (x) = x n , with n preferably greater than 2, or by any other polynomial function.

The circuit arrangement is preferably designed so that the base a to which the input signal of the function generator is set in the exponent, the Euler number e is. Such function generators with an exponential to the base e Transmission behavior is simple to realize using a diode or a transistor.

Furthermore, a first is provided for the function generator Subtract circuit downstream, which is a constant signal subtracted from the output signal of the function generator. When the circuit arrangement is idle, i. H. Removing the Load at their output terminals, the current must be in the current control arrangement neglecting losses in the circuit arrangement be reduced to zero. This requires a signal zero at the input terminal of the current control arrangement. An output signal is zero with a function generator, which has an exponential transmission behavior, cannot be realized as this is theoretically an input signal minus infinity. By subtracting one constant signal from the output signal of the function generator is a zero value at the input terminal of the current control arrangement with a finite input signal from the function generator reachable.

The current control arrangement preferably assigns one in parallel whose input terminals are switched circuit breakers, one Pulse width modulator, a second voltage measuring arrangement, a Current measuring arrangement, a second subtracting arrangement as well a multiplier arrangement. The circuit breaker will depending on an output signal of the pulse width modulator open or closed with an entrance to the Pulse width modulator via the second subtracting arrangement Differential signal is supplied, which is the difference of a signal supplied by the current measuring arrangement and one product signal supplied by the multiplier arrangement. The product signal is generated by means of the multiplier arrangement from an output signal of the second voltage measuring arrangement, that corresponds to the mains voltage signal, and that at the Input terminal of the current control arrangement applied control signal educated. Such a current control arrangement causes one in the presence of a sinusoidal mains voltage essentially sinusoidal mains current consumption, the amplitude of the Mains current consumption by evaluating the mains voltage signal can be varied.

The invention further relates to a use of the invention Circuit arrangement in a switching power supply.

Figur 1

eine erfindungsgemäße Schaltungsanordnung nach einem ersten Ausführungsbeispiel,

Figur 2

eine erfindungsgemäße Schaltungsanordnung nach einem zweiten Ausführungsbeispiel,

Figur 3

beispielhafte Realisierung eines Funktionsgenerators mit exponentiellem Übertragungsverhalten.

The invention is explained in more detail below using exemplary embodiments with reference to circuit diagrams. Show it:

Figure 1

an inventive circuit arrangement according to a first embodiment,

Figure 2

an inventive circuit arrangement according to a second embodiment,

Figure 3

exemplary implementation of a function generator with exponential transmission behavior.

Fig. 1 shows a first embodiment of a circuit arrangement according to the invention. A first rectifier arrangement GL1 having a bridge rectifier BG is shown with an AC voltage connection EK1, EK2 and output terminals AK1, AK2, to which a current control arrangement SRA is connected. The current control arrangement has an input terminal EK3 for applying a control signal RS supplied by a feedback branch RZ. The current control arrangement SRA also has output terminals AK3, AK4, to which a second rectifier arrangement GL2 is connected. An output voltage U _{a can be} tapped off at output terminals AK5, AK6 of the second rectifier arrangement GL2 and is to be kept constant independently of a load R _L that can be connected to the output terminals AK5, AK6.

A first voltage measuring arrangement MA1 is further connected to the output terminals AK5, AK6 of the second rectifier arrangement GL2 and supplies _a voltage signal SS dependent on the output voltage U _a to a control arrangement RA in the feedback branch RZ. The control arrangement RA is followed by a function generator in the feedback branch RZ which, in the exemplary embodiment shown, corresponds to an output signal y as a function of an input signal x y = c.a bx delivers. In the example shown, this output signal y is fed directly to the input terminal EK3 of the current control arrangement SRA as a control signal RS.

The current control arrangement SRA shown has a second voltage measuring arrangement, which is designed as a resistor R _S , which is connected to an output terminal AK1 of the first rectifier arrangement GL1, and from which a mains voltage signal NS can be tapped. Due to the bridge rectifier BG, this mains voltage signal NS depends on the magnitude of the mains voltage U _N. After this mains voltage signal NS has been multiplied in a multiplier MUL by the control signal RS, a current signal SI supplied by a current measuring arrangement SMA is subtracted from the evaluated mains voltage signal BNS resulting from the evaluation of the mains voltage signal NS by the control signal RS. In the example shown, the current measuring arrangement SMA has a current sensing resistor R _F , on which a voltage drop is produced by means of a current I flowing into or out of the current regulating arrangement SRA, which drop is determined by means of an operational amplifier OPV and is supplied as a current signal SI to a third subtracting arrangement SUB3 . An output signal of the third subtraction arrangement SUB3 is present at an input of a pulse width modulator PWM, at whose output control signals AS are present, by means of which a circuit breaker LS connected between the output terminals AK3, AK4 of the current control arrangement SRA is opened or closed. When the circuit breaker LS is closed, the current I flows in the current control arrangement via an inductance L and the circuit breaker; the inductance L takes up energy. When the circuit breaker LS is open, the inductance L delivers energy in the form of current via a diode D to a capacitance C of the second rectifier arrangement GL2. The control signals AS of the pulse width modulator PWM are such that the switch LS is closed the longer the larger a signal present at the input of the pulse width modulator PWM.

In the case of sinusoidal mains voltage U _N or sinusoidal mains voltage signal NS, the current control arrangement SRA shown results in a sinusoidal mains current consumption I _N or a sinusoidal current I. The amplitude of the current I is proportional to the amplitude of the rated mains voltage signal BNS supplied by the multiplier arrangement MUL. Halving the mains voltage U _N thus halves the mains current consumption or reduces the power delivered to the load R _L by a factor of 4. If the mains voltage U _N is halved, the original output power is maintained and the output voltage U _{a is maintained} at a predeterminable value, a doubling of the mains current consumption compared to the original mains current consumption is required. The control signal applied to the input terminal EK3 of the current control arrangement SRA must therefore be increased by a factor of 4 compared to the original value. This is as follows:

When the mains voltage U _{N is} reduced, the mains current consumption or the current I flowing in the current control arrangement SRA is reduced proportionally. If the control signal RS does not change at first, the power delivered to the load R _L drops, so that the output voltage U _A also drops. A voltage signal SS formed by the output voltage by means of a first and second resistor R1, R2 in the first voltage measuring arrangement MA1 is subtracted from a reference signal U ₁ in the control arrangement RA of the feedback branch RZ and subsequently integrated in an integrating arrangement IN. If the output voltage U _A drops due to a reduction in the output power, the voltage signal SS also drops and an output signal supplied by the second subtracting arrangement SUB2 rises, so that an output signal supplied by the integrating arrangement IN also increases. The function generator FG connected downstream of the integrating arrangement IN uses this output signal as the input signal x and uses it to generate an output signal y which is exponentially dependent thereon and which is fed directly to the current regulating arrangement SRA in the example shown as a regulating signal. The control signal RS and thus the current I flowing in the current control arrangement SRA increases until the output voltage U _a again reaches a predetermined value at which the voltage signal SS corresponds to the reference signal U ₁ , so that the control signal RS is no longer increased . When the mains voltage U _N increases, the control signal RS decreases accordingly.

In the same way, the current consumption or the current I flowing in the current control arrangement SRA is readjusted if the load R _L changes while the mains voltage U _N remains the same. If the control signal RS initially remains constant, the power consumed or output remains constant and the output voltage U _A changes. The control signal RS is then readjusted in the manner described until the output voltage U _A again reaches a predetermined value.

As already mentioned, the control signal RS is quadratic dependent on the mains voltage U _N , while the same load changes independently of the mains voltage U _N initially cause the same changes in the output voltage U _A. Thus, the same load changes also cause the same changes in the output signal supplied by the integrating arrangement IN, while this requires changes in the control signal RS which are dependent on the input voltage U _N. Due to the exponential behavior of the function generator FG, linear changes in the input signal x have a proportional effect on changes in the output signal y. This can be illustrated by the following equation, after which y = c.a bx is. If the input signal x changes by the value Δx, the new output signal y1 results in: y1 = c.a bx a bΔx .

The change in the output signal is therefore independent of its absolute value and only dependent on the change in the input signal x. This results in readjustment of the output voltage U _A with exponential transmission behavior of the function generator and change in the line voltage U _N or change in the load R _L independently of the line voltage.

A desired exponential function can preferably be carried out by a polynomial function in for the input signals x and the Output signals approximate relevant functional areas will.

FIG. 2 shows a further embodiment of a circuit arrangement according to the invention, in which the function generator FG is followed by a third subtractor arrangement SUB3, which subtracts a constant signal U ₂ from the output signal y of the function generator FG. In this way, a control signal zero can be achieved for finite input signals x, which is required when the circuit arrangement is idle.

3 shows an example of a circuit for a function generator FG with exponential transmission behavior. The function generator FG has a transistor T which is connected to a base electrode B with reference potential M, to an emitter electrode E to an input terminal EK and to a collector electrode C via a resistor R to an output terminal AK. Between the collector electrode C and the output terminal AK there is an operational amplifier OPV, which is connected with one input to the collector electrode C and with another input with reference potential M. In this circuit, a voltage U _{2 present} between the output terminal AK and the reference potential results exponentially to the base e from a voltage U _{1 present} between the input terminal EK and the reference potential.

Reference list

GL1

first rectifier arrangement

SRA

Current control arrangement

GL2

second rectifier arrangement

MA1

first voltage measuring arrangement

RZ

Feedback branch

RA

Control arrangement

EK1, EK2

AC connection

AK1 - AK6

Output terminals

BG

Bridge Rectifiers

R1, R2, RS

Resistances

RF

Current sensing resistance

L

Inductance

C.

capacity

D

diode

LS

Circuit breaker

SMA

Current measuring arrangement

OPV

Operational amplifier

SUB1-SUB3

Subtracting orders

U _N

Mains voltage

U _a

Output voltage

U ₁ , U ₂

Reference signals

FG

Function generator

PWM

Pulse width modulator

R _L

load

EK3

Current control assembly input terminal

NS

Mains voltage signal

RS

Control signal

AS

Control signal

SS

Voltage signal

I.

Current in the current control arrangement

x

Input signal from the function generator

y

Output signal of the function generator

IN

Integration arrangement

SI

Current signal

MUL

Multiplier arrangement

Claims (10)

Circuit arrangement for generating a load-independent DC voltage with the following features: a first rectifier arrangement (GL1) with an AC voltage connection (EK1, EK2) and two output terminals (AK1, AK2); a current control arrangement (SRA) connected to the output terminals (AK1, AK2) of the first rectifier arrangement (GL1) and having two output terminals (AK3, AK4) for regulating the mains current consumption; a second rectifier arrangement (GL2) connected to the output terminals (AK3, AK4) of the current control arrangement (SRA) with output terminals (AK5, AK6), at which an output voltage (U _a ) can be tapped; a voltage measuring arrangement (MA) connected to the output terminals of the second rectifier arrangement for providing a voltage signal (SS) at an output; a feedback branch (RZ) with a control arrangement (RA) having an integrating arrangement (IN) for feeding back the voltage signal (SS) to an input terminal (EK) of the current control arrangement (SRA); characterized by the following additional characteristic: one of the control arrangement (RA) in the feedback branch downstream of the function generator (FG), which one of an input signal (x) according to a function y = f (x) dependent output signal (y) is generated, the derivative of the function f (x) being dependent on the input signal (x) and the derivative increasing at least in sections with an increasing input signal (x). Circuit arrangement according to claim 1, characterized in that the function generator (FG) at least approximately according to the output signal (y) y = f (x) = c.a bx or y = f (x) = cx n , where a, b, c and n are constants. Circuit arrangement, according to claim 2, characterized in that a is Euler's number e. Circuit arrangement, according to claim 2, characterized in that n> 2. Circuit arrangement according to one of the preceding claims, characterized in that the function generator (FG) a first subtraction circuit (SUB1) for subtracting one connected constant signal from the output signal (y) is. Circuit arrangement according to one of the preceding claims, characterized in that the function generator (FG) has a diode or a transistor. Circuit arrangement according to one of the preceding claims, characterized in that the integrating arrangement (IN) a second subtraction arrangement (SUB2) in the control arrangement (RA) is connected upstream, which the voltage signal (SS) from subtracted from a reference signal. Circuit arrangement according to one of the preceding claims, characterized in that the current control arrangement (SRA) one connected in parallel to their output terminals (AK3, AK4) Circuit breaker (LS), a pulse width modulator (PWM), a second voltage measuring arrangement, a current measuring arrangement (SMA), a third subtraction arrangement (SUB3) as well has a multiplier arrangement (MUL), the circuit breaker (LS) depending on an output signal of the Pulse width modulator (PWM) is open or closed and one input of the pulse width modulator (PWM) via the third subtracting arrangement (SUB3) fed a difference signal is the difference between one of the current measuring arrangement (SMA) supplied signal and one from the multiplier (MUL) delivered product signal, where the product signal by means of the multiplier arrangement (MUL) from an output signal of the second voltage measuring arrangement, and one at the input terminal (EK3) of the current control arrangement (SRA) signal is formed. Circuit arrangement according to one of the preceding claims, characterized in that the first rectifier arrangement (GL1) has a bridge rectifier. Use of a circuit arrangement according to one of the preceding Claims in a switching power supply.

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