DE102020205159A1 - Method for providing a direct current output and switching - Google Patents

Abstract

The invention relates to a method for providing an output direct current, in particular in a charger, wherein an input alternating current of the circuit arrangement is increased in amount in an area of low voltage and / or decreased in amount in an area of high voltage.

Description

Technical area

The invention relates to a method for providing an output direct current by means of a circuit, in particular in a charger.

The invention also relates to a corresponding circuit arrangement for providing a constant output direct current from a sinusoidal mains voltage.

State of the art

Although the present invention is generally applicable to provide an output direct current from any variable voltage, the present invention is explained in relation to a public low-voltage distribution network with a sinusoidal network voltage in the form of an alternating voltage of 230 V / 400 V and a frequency of 50 Hz .

Although the present invention can generally be used for any circuit arrangements with different topologies, the present invention is explained in relation to a charger topology - for example for a switched-mode power supply or a charger - which is intended for connection to the public low-voltage distribution network.

When operating the most varied of electronic circuit arrangements, there may be requirements to provide a direct output current from a variable voltage, for example a sinusoidal mains voltage. In this case, an essentially constant output direct current can be preferred because there are limit values for the safe operation of the battery cells, for example for the charging current of a battery.

In an area of low voltage - that is, in the vicinity of a zero crossing of the mains voltage - many topologies are not functional, in particular conventional topologies for switched-mode power supplies. The lower the input voltage, the more difficult it is to operate the topology with soft switching, especially when the input currents are also small. Soft-switching operation is, however, desirable because of the low switching losses and the preferably de-energized or de-energized switching.

This problem occurs in particular with topologies for known switched-mode power supplies that use a power factor correction (PFC stage, PFC = Power Factor Correction / Compensation), since both the input current and the input voltage on the network side are sinusoidal. However, power factor correction circuit arrangements are required in order to be able to comply with limit values for the harmonic content of the mains voltage. The non-sinusoidal current consumption of non-linear loads, for example from topologies for switched-mode power supplies, causes voltage drops at the network impedance, which cause the network voltage profile to deviate from the ideal sinusoidal shape. These harmonics are standardized for many applications and may not exceed certain limit values for connection to the public low-voltage distribution network, for example, see IEC / EN 61000-3-2.

Disclosure of the invention

In one embodiment, the invention provides a method for providing an output direct current by means of a circuit arrangement, in particular in a charger, wherein an input alternating current of the circuit arrangement is increased in amount in an area of low voltage and / or decreased in amount in an area of high voltage.

• - einen Gleichrichter und
• - eine Wandlerstufe,

wobei die Schaltungsanordnung leistungsfaktorkorrekturfrei und zwischenkreiskapazitätenfrei ausgebildet ist. „Zwischenkreiskapazitätenfrei“ bezieht sich insbesondere in den Ansprüchen, vorzugsweise in der Beschreibung darauf, dass die Schaltungsanordnung ohne internen Energiespeicher zur Pufferung einer Leistungswelligkeit einer gleichgerichteten Netzspannung ausgebildet ist. Im öffentlichen Niederspannungs-Verteilnetz mit einer Frequenz von 50 Hz weist die Leistungswelligkeit der gleichgerichteten Netzspannung eine Frequenz von 100 Hz auf.In a further embodiment, the invention provides a circuit arrangement which is designed to provide a constant output direct current, in particular in a charger, the circuit arrangement comprising:

• - a rectifier and
• - a converter stage,

wherein the circuit arrangement is designed to be free of power factor correction and intermediate circuit capacitance. “No intermediate circuit capacitance” refers in particular in the claims, preferably in the description, to the fact that the circuit arrangement is designed without an internal energy store for buffering a power ripple of a rectified mains voltage. In the public low-voltage distribution network with a frequency of 50 Hz, the power ripple of the rectified network voltage has a frequency of 100 Hz.

The term “constant output direct current” relates in particular in the claims, preferably in the description, to the professional understanding of the “output current” and includes - in addition to the technical deviations and fluctuations in the order of a few percent around the nominal value - also over time mostly constant output direct current with occasional interruptions. The decisive factor for a constant output direct current is that the distribution of the output direct current is more uniform over an entire network period and thus an increase in a Root mean square (RMS) of the output direct current is possible with the same maximum value of the output direct current.

The term “input alternating current” is to be understood in the broadest sense and relates in particular in the claims, preferably in the description, to a variable input current which does not necessarily have a sinusoidal profile. In other words, the “alternating input current” can also have other shapes in addition to the sinusoidal shape.

In particular in the claims and preferably in the description, the range of low voltage in terms of magnitude and the range of high voltage in terms of magnitude are to be understood in relation to the voltage curve over the entire network period.

The areas of low voltage in terms of magnitude can be defined in such a way that the voltage in these areas is lower in magnitude than an effective value of the voltage. Correspondingly, the areas of high voltage in terms of magnitude can be defined in such a way that the voltage in these areas is higher in magnitude than the rms value of the voltage. Furthermore, areas of low voltage can be defined in such a way that the voltage in these areas is less than 50% of an amplitude of the voltage, preferably less than 25% of the amplitude of the voltage and in particular less than 10% of the amplitude of the voltage. Correspondingly, the areas of high voltage in terms of magnitude can be defined such that the voltage in these areas is higher in magnitude than 50% of an amplitude of the voltage, preferably higher than 75% of the amplitude of the voltage and in particular higher than 90% of the amplitude of the voltage.

In particular, it applies here that the AC input current of the circuit arrangement is increased in magnitude the greater the magnitude of the lower the voltage in the area of the magnitude of the lower voltage. Conversely, the AC input current of the circuit arrangement is reduced the greater the amount, the higher the amount of the voltage in the area of high voltage.

One of the advantages achieved with this is that new single-stage topologies that would not work with a sinusoidal AC input current can be used. For example, flyback circuit arrangements would not be functional below a minimum input voltage. By introducing a blanking interval with an input current of 0 amperes in the range of low line-side voltages, it is possible to use circuit arrangements that are free of power factor correction and intermediate circuit capacitance without application-specific limit values, for example for charging currents, being exceeded or undershot. For example, active clamp flyback circuit arrangements can be used. These new single-stage topologies can be dimensioned with lower power peaks and implemented using smaller passive components. This enables significant cost savings and advantages in terms of installation space and compactness, which is a frequently asked requirement, particularly in the case of topologies for switched-mode power supplies. In other words, a constant output direct current can be achieved without the power ripple of the rectified mains voltage having to be buffered in an intermediate circuit. An intermediate circuit can in particular comprise an intermediate circuit capacitance. Another advantage achieved with this is that the efficiency of the topology increases, since soft-switching operation is possible over a larger area.

By adapting the shape or the course of the input alternating current as a function of the mains voltage, the output direct current is manipulated in a targeted manner. In other words, there is a direct application-specific added value through the manipulation of the input alternating current.

Further features, advantages and further embodiments of the invention are described below or become apparent as a result.

According to a further advantageous development, the input alternating current is kept proportional to a reciprocal value of the voltage. One of the advantages achieved with this is that the output direct current is better, i.e. more evenly, distributed over the entire network period and there is no curve of the output direct current in a squared sinusoidal shape.

According to a further advantageous development, the output direct current is kept constant. In other words, the output direct current is distributed more evenly over the entire network period. One of the advantages achieved in this way is that the application-specific minimum required output direct current, preferably according to its effective value, can be maintained over a larger range. In other words, an increase in the rms value is possible with the same maximum value of the output direct current.

und $$p_{out}=U_{out}{I}_{out}$$

mit
u_in die Eingangswechselspannung der Schaltungsanordnung ist, iin der Eingangswechselstrom der Schaltungsanordnung ist, Uout die Ausgangsgleichspannung der Schaltungsanordnung ist und lout der Ausgangsgleichstrom der Schaltungsanordnung ist.The input power of the circuit _{arrangement p in} must be equal to the output power pout of the circuit arrangement, where $$p_{in}=u_{in}{i}_{in}$$

and $$p_{Out}=U_{Out}{\mathrm{I.}}_{Out}$$

with
u _{in is} the AC input voltage of the circuit arrangement, iin is the AC input current of the circuit arrangement, Uout is the DC output voltage of the circuit arrangement and lout is the DC output current of the circuit arrangement.

und aufgelöst nach dem gewünschten konstanten Ausgangsgleichstrom: $$i_{in}=\frac{U_{out}{I}_{out}}{u_{in}}$$

Hence: $$u_{in}{i}_{in}=U_{Out}{\mathrm{I.}}_{Out}$$

and resolved according to the desired constant output direct current: $$i_{in}=\frac{U_{Out}{\mathrm{I.}}_{Out}}{u_{in}}$$

Since u _{in can be specified on the} network side and is regularly known, the optimal value for iin can always be calculated so that U _out I _out is essentially constant. Since U _out I _{out should be} essentially constant, the input alternating current iin is optimally in purely mathematical terms proportional to a reciprocal value of the voltage u _in .

According to a further advantageous development, the constant output direct current is briefly interrupted at least once. The term “briefly interrupted” relates in particular in the claims, preferably in the description, to such interruptions which are of a shorter duration than the times of the constant output direct current. Such short interruptions are harmless for a number of applications, for example with some chargers and battery cells. One of the advantages achieved in this way is that the circuit arrangement can efficiently fulfill its functionality even without power factor correction and intermediate circuit capacitance, which brings significant advantages in terms of cost savings and compactness. The functionality of these omitted components can in this case, for example, be taken over by a converter stage designed as a DC voltage converter.

According to a further advantageous development, the constant output direct current is only briefly interrupted in areas of zero crossings of the voltage. One of the advantages achieved with this is that the minimum required output direct current, preferably according to its effective value, as well as the maximum value of the output direct current approximate, and it becomes possible to comply with the application-specific maximum currents - for example charging currents of a battery cell - even with a high required effective value for the output direct current .

According to a further advantageous development, a harmonic content of the input alternating current is continuously and / or repeatedly compared with a predetermined limit value. The predetermined limit value can be set in a standard, for example. One of the advantages achieved with this is that it can be determined during operation whether the harmonic content of the input alternating current satisfies the specified limit value.

According to an advantageous development, the harmonic content of the input alternating current is adapted when the predetermined limit value is exceeded or not reached. One of the advantages achieved with this is that, through permanent comparison with the limit values, operation that conforms to the standard can be guaranteed. In other words, the harmonic content contained in the adapted current form of the input alternating current remains within limit values defined in a standard. An example of such a standard is IEC / EN 61000-3-2.

According to an advantageous development of the circuit arrangement, the rectifier is a passive rectifier. One of the advantages achieved in this way is that the circuit arrangement becomes more cost-effective overall. Alternatively, the rectifier can be designed as an active rectifier. The advantage of this is that even more economical operation is possible.

Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures on the basis of the drawings.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination, but also in other combinations or on their own, without departing from the scope of the present invention.

Preferred designs and embodiments of the invention are shown in the drawings and are explained in more detail in the following description, with the same reference symbols referring to the same or similar or functionally identical components or elements.

Figure list

• 1 zwei Graphen, in welchen jeweils für den Eingangsstrom und für den Ausgangsstrom der Verlauf von Spannung und Strom dargestellt ist;
• 2 eine Darstellung einer bekannten Schaltungsanordnung sowie entsprechende Stromverläufe;
• 3 eine Darstellung einer Schaltungsanordnung gemäß einer Ausführungsform der vorliegenden Erfindung sowie entsprechende Stromverläufe; und
• 4 eine Darstellung der Schaltungsanordnung der 3 sowie entsprechende Stromverläufe bei Anwendung eines Verfahrens gemäß einer Ausführungsform der vorliegenden Erfindung.

It shows in schematic form

• 1 two graphs in which the voltage and current curves are shown for the input current and for the output current;
• 2 a representation of a known circuit arrangement and corresponding current curves;
• 3 a representation of a circuit arrangement according to an embodiment of the present invention and corresponding current profiles; and
• 4th an illustration of the circuit arrangement of 3 and corresponding current profiles when using a method according to an embodiment of the present invention.

Embodiments of the invention

1 shows two graphs 1 , 2 , in which the relationship between voltage and current is shown for an input current as well as for an output current.

In the graph above 1 the 1 is a curve of a sinusoidal line voltage 3 shown (solid line). Regarding an input alternating current 4th (dotted line) of a circuit arrangement, a sinusoidal current form is therefore also set in principle. However, the current can be in areas 5 , 6th low voltage does not flow and is zero there.

In the graph below 2 the 1 is a constant DC output voltage 7th shown. Becomes the sinusoidal mains voltage 3 by means of a circuit arrangement (in 1 not shown), especially in a charger, into a constant DC output voltage 7th converted, in particular to charge a battery, results in a known manner for an output direct current 8th a curve in a squared sinusoidal form.

2 shows a known circuit arrangement 9 with a power factor correction 10 , a DC link capacitance 11 and a converter stage 12th .

The converter stage 12th includes a field effect transistor (FET) 13th and a transformer 14th . The converter stage is designed as a DC voltage converter. Will this circuit arrangement 9 with a voltage, for example with a sinusoidal mains voltage 3 as well as sinusoidal mains current 15th operated, there is a constant output direct current 16 .

3 shows a circuit arrangement 17th according to an embodiment of the present invention.

The circuit arrangement 17th is designed to be free of power factor correction and DC link capacitance and has a passive rectifier 18th and a converter stage designed as a DC voltage converter 12th with a field effect transistor (FET) 13th and a transformer 14th on. Will this circuit arrangement 17th with sinusoidal mains voltage 3 as well as sinusoidal mains current 15th operated, this sinusoidal mains voltage is used 3 first through the rectifier 18th into an exclusively positive periodically fluctuating DC voltage 18th rectified. This DC voltage 18th however, remains unsmoothed. After the converter stage 12th This results in the squared sinusoidal shape for the output direct current 8th .

4th shows a circuit arrangement 17th according to 3 .

In contrast to the circuit according to 3 becomes this circuit arrangement 17th in 4th with an input alternating current 20th operated in one area 21 Amount of low line-side voltage is increased in amount and in a range 22nd Amount of high line-side voltage is reduced in amount. This is how this current form becomes the input alternating current 20th first with the rectifier 19th in a rectified form 23 brought. In particular, the shape of the input alternating current 20th proportional to a reciprocal value of the line-side voltage (in 4th not shown). After the converter stage 12th the result is a constant output direct current 24 , the short interruptions 25th having. The brief interruptions 25th each lie in the areas of zero crossings 26th the mains voltage.

• - Anwendungsspezifischer Maximalwert des Ausgangsgleichstromes ist auch ohne internen Zwischenspeicher für die Leistungswelligkeit des Netzes möglich.
• - Leistungsfaktorkorrekturfreie und zwischenkreiskapazitätenfreie Schaltungsanordnungen sind nutzbar.
• - Passive Bauelemente können kleiner dimensioniert werden, Bauraum kann insgesamt reduziert werden.
• - Steigerung des Wirkungsgrades durch Erweiterung des Bereichs, in welchem ein weichschaltender Betrieb möglich ist.

In summary, at least one of the embodiments has at least one of the following advantages:

• - Application-specific maximum value of the output direct current is also possible without an internal buffer for the power ripple of the network.
• - Circuit arrangements without power factor correction and without intermediate circuit capacitance can be used.
• - Passive components can be dimensioned smaller, overall installation space can be reduced.
• - Increase in efficiency by expanding the range in which soft-switching operation is possible.

Although the present invention has been described on the basis of preferred exemplary embodiments, it is not restricted thereto, but rather can be modified in many ways.

Claims (9)

Method for providing an output direct current (24) by means of a circuit arrangement (17), in particular in a charger, wherein an input alternating current (4) of the circuit arrangement (17) is increased in terms of amount in an area (21) and / or in a low voltage area Area (22) is reduced in terms of amount of high voltage in terms of amount. Procedure according to Claim 1 , whereby the input alternating current (4) is kept proportional to a reciprocal value of the voltage. Method according to one of the Claims 1 or 2 , the output direct current (24) being kept constant. Procedure according to Claim 3 , the constant output direct current (24) being briefly interrupted (25) at least once. Procedure according to Claim 4 , wherein the constant output direct current (24) is only briefly interrupted in areas of zero crossings (26) of the voltage. Method according to one of the Claims 1 - 5 , wherein a harmonic content of the input alternating current (4) is continuously and / or repeatedly compared with a predetermined limit value. Procedure according to Claim 6 , whereby the harmonic content of the AC input current is adjusted when the specified limit value is exceeded or not reached. Circuit arrangement (17) for providing a constant output direct current (24), in particular in a charger, comprising: - a rectifier (18) and - a converter stage (12), characterized in that the circuit arrangement (17) is designed to be free of power factor correction and intermediate circuit capacitance . Circuit arrangement according to Claim 8 , wherein the rectifier (18) is a passive rectifier.

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