WO2013030156A2

WO2013030156A2 - Domestic appliance having an electrical circuit assembly having a stand-by mode and an operating mode, and method for operating a circuit assembly of a domestic appliance

Info

Publication number: WO2013030156A2
Application number: PCT/EP2012/066610
Authority: WO
Inventors: Lubos Hajduk; Anton Chomic; Robert Elko
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH
Priority date: 2011-08-31
Filing date: 2012-08-27
Publication date: 2013-03-07
Also published as: DE102011081877A1; WO2013030156A3

Abstract

The invention relates to a domestic appliance, comprising an electrical circuit assembly (1), which can be switched between an operating mode and a stand-by mode and which comprises: a circuit input (2) having a first and a second input connection (3, 4), between which an alternating voltage (UN) can be applied; a mains filter (5); a rectifier (9) for rectifying the alternating voltage (UN); a smoothing capacitor (29) for smoothing the rectified alternating voltage (UN) so that a primary direct voltage (UP) is present at the smoothing capacitor (29); a switched-mode power supply (10), which is coupled to the smoothing capacitor (29) and which taps the primary direct voltage (UP) at the smoothing capacitor (29) and provides a secondary voltage (US') from the tapped primary direct voltage (UP), with which secondary voltage an electrical load (11, 14) of the domestic appliance can be supplied, wherein the switched-mode power supply (10) has a transformer (32) having a primary winding (33), which is coupled to the smoothing capacitor (29), and having a secondary winding (34), at which the secondary voltage (US') for the electrical load (11, 14) can be tapped, wherein the switched-mode power supply (10) also has a switching device (35) connected in series with the primary winding (33) for controlling a current flow through the primary winding (33), and wherein the circuit assembly (1) has means (12) for reducing the amplitude of the primary direct voltage (UP) in the stand-by mode so that the amplitude of the primary direct voltage (UP) is lower in the stand-by mode than in the operating mode, wherein the means (12) for reducing the amplitude have a passive current-limiting element (12) that is different from the mains filter (5) and that is connected in series with the switched-mode power supply (10), the current-limiting element being designed to limit the amperage of a charging current flowing through the smoothing capacitor (29), wherein an electrical switch (13) is connected in parallel with the current-limiting element (12), by means of which electrical switch the current-limiting element (12) can be bridged in the operating mode.

Description

Domestic appliance with an electrical circuit arrangement with a standby mode and an operating mode and method for operating a circuit arrangement of a

household appliance

The invention relates to a household appliance with an electrical circuit arrangement which can be switched between an operating mode and a standby mode. The circuit arrangement has a circuit input which has a first and a second input connection, between which an alternating voltage

(Mains voltage) can be created. The circuit also includes a line filter coupled to the circuit input. It also includes a rectifier downstream of the line filter, which rectifier for rectifying

AC voltage is formed. A rectifier downstream

Smoothing capacitor is used for smoothing the rectified AC voltage, so that applied to the smoothing capacitor, a primary DC voltage. The

Circuitry also includes a coupled to the smoothing capacitor switching power supply, which picks up the primary DC voltage on the smoothing capacitor and is adapted to a tapped from the primary DC voltage

Secondary voltage changed with respect to the primary DC voltage

Provide amplitude with which an electrical load of the household appliance can be supplied. The switching power supply has a transformer, which a

Primary winding, which is coupled to the smoothing capacitor, and a

Secondary winding comprises, at which the secondary voltage can be tapped for the electrical load. The switching power supply also has a switched with the primary winding in series switching device, which is used to control a

Current flow is formed by the primary winding. The circuit arrangement has means for reducing the amplitude of the primary DC voltage in the standby mode, so that the amplitude of the primary DC voltage in the standby mode is lower than in the operating mode. The invention also relates to a method for operating such a circuit arrangement of a household appliance. It is state of the art that a home appliance can be switched between a normal mode and a standby mode. The standby mode is also referred to as a standby mode. In such a standby mode, electrical energy is to be saved. Therefore, most of the home appliance's electrical appliances are turned off in standby mode; only a standby control unit can be activated, which can switch the household appliance back into the operating mode. For example, the standby controller may

Receive control signals from an operating device of the household appliance and then switch the household appliance in the operating mode or activate when the user makes a corresponding input to the operating device.

A household appliance with a circuit arrangement of the type mentioned is known for example from the document EP 0 873 651 B1. This known

Circuit arrangement includes a switching power supply having a primary winding and two secondary windings. Parallel to the primary winding is a

Smoothing capacitor connected to which a DC primary voltage is provided, by means of a rectifier, which rectifies an AC voltage of the electric power network. In order to save electrical energy in standby mode, the circuit arrangement includes a device which generates the primary DC voltage from the AC voltage in standby mode. The device is designed such that the amplitude of the primary DC voltage at the smoothing capacitor in standby mode is lower than in the operating mode. The device may be formed by the X capacitors of a network filter. Alternatively, the device may include a transistor, so that the device according to the principle of

Phase control is working.

The circuit arrangement according to document EP 0 873 651 B1 has the disadvantage that the device for reducing the amplitude of the primary DC voltage is relatively complicated and has a multiplicity of components which are required for reducing the amplitude of the primary DC voltage. This circuit thus claimed on the one hand relatively much space; On the other hand, it is also relatively expensive, because active components - such as transistors - must be used. The device for reducing the amplitude of the primary DC voltage is therefore also unsuitable, integrated into existing circuit arrangements especially in those already existing

Circuit arrangements that have little space.

It is an object of the invention to provide a solution, as in a household appliance of the type mentioned the means for reducing the amplitude of

Primary DC voltage in standby mode very simple, reliable and

can be built cost-saving, so that these funds can be integrated into existing or existing circuit arrangements of household appliances. This object is achieved by a household appliance and by a

Method solved with the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description and the figures. An inventive household appliance comprises an electrical circuit arrangement which between an operating mode - corresponds to an operating mode of the

Domestic appliance - and a standby mode - corresponds to a standby mode of the home appliance - can be switched. The circuit arrangement comprises a circuit input having a first and a second input terminal, between which an AC voltage can be applied. The circuit input is a line filter (so-called EMC filter, electromagnetic compatibility) coupled. The line filter is followed by a rectifier for rectifying the AC voltage. The rectifier in turn is followed by a smoothing capacitor, which is designed to smooth the rectified AC voltage, so that on the

Smoothing capacitor is applied a primary DC voltage. The smoothing capacitor is a switching power supply coupled to the smoothing capacitor

Takes primary DC and tapped from the tapped primary DC voltage, a secondary voltage with respect to the primary DC voltage

Provides amplitude with which an electrical load of the household appliance can be supplied. The smoothing capacitor can also be integrated in the switched-mode power supply. The switching power supply has a transformer. The transformer includes a primary winding coupled to the smoothing capacitor, as well as a secondary winding to which the secondary voltage for the electrical load can be tapped. The switching power supply also has a switching device connected in series with the primary winding, which switching device is designed to control a current flow through the primary winding. The circuit also includes means for reducing the amplitude of the primary DC voltage in standby mode so that the amplitude of the DC primary voltage in standby mode is lower than in the operating mode. The means for reducing the amplitude have a different from the line filter and in series with the switching power supply switched current limiting element, which is designed to limit the current strength of a current flowing through the smoothing capacitor charging current. There is also provided an electrical switch which is connected in parallel to the current limiting element and by means of which the

Current limiting element is bridged in operating mode.

Thus, the effect of the invention is achieved in that the means for reducing the amplitude of a passive component - especially only a single

Component - includes a passive current limiting element connected in series with the switching power supply and limits the current flow to the smoothing capacitor in the standby mode to a value greater than zero, so that the smoothing capacitor is charged slower in standby mode than in the operating mode. In the operating mode, the current limiting element is bridged by means of the switch. In standby mode thus electrical energy is saved, because the electrical power, which is consumed by the switching power supply or the smoothing capacitor, is by the

Current limiting element limited. The electrical power consumed by the smoothing capacitor is thus lower in the standby mode than in the operating mode.

Compared to the prior art, the household appliance according to the invention has the advantage that the means for reducing the amplitude are particularly simple and thus space-saving and cost-reduced, so that these means without much

Expenditure can be integrated into existing circuit arrangements of household appliances. It suffices namely only a passive current limiting element and an electrical switch, which for bridging the

Current limiting element is used.

Under a household appliance is in the present case understood a device which, for

Housekeeping is used. This may for example be a large household appliance, such as a washing machine, a tumble dryer, a Dishwasher, a cooking appliance, an extractor hood or a refrigerator, such as a refrigerator, a freezer or a fridge-freezer. But this can also be a small household appliance, such as a coffee machine or a food processor. In principle, the current limiting element may be an ohmic resistor. However, it proves to be particularly advantageous if the current limiting element is a current limiting capacitor. By the current limiting capacitor and the smoothing capacitor, a capacitive voltage divider can be formed, which ensures the reduction of the amplitude of the primary DC voltage in standby mode. This capacitive voltage divider thus contains on the one hand the current limiting capacitor and on the other hand also already existing in the household appliance anyway

Smoothing capacitor. With only a current limiting capacitor, which is connected in series with the switching power supply, thus the same effect as in the prior art can be achieved with a variety of components.

The means for reducing the amplitude preferably include only a single component. Waiving further components, these means can therefore only the current limiting element - in particular the

Current limiting capacitor - have. These funds are then particularly compact and cost-effective. As a result, even existing circuit arrangements of household appliances can be upgraded with such a current limiting element, without having to be reconfigured in a complex manner.

The circuit arrangement can be designed so that only the current limiting element can be bridged with the electrical switch. It is therefore unnecessary bridging other components with the associated

Disadvantages in terms of cost and installation space.

The switching device may comprise a Zener diode whose cathode is connected to the

Primary winding and the anode are coupled to a reference potential (ground). An electric current flows through the primary winding when the amplitude of the primary DC voltage dropping across the smoothing capacitor reaches one of the

Breaking voltage of the Zener diode dependent threshold exceeds. These Embodiment is particularly simple to implement, and it is unnecessary, if necessary, the use of an additional transistor, as used in the prior art for controlling the flow of current through the primary winding. It is sufficient to use a zener diode which connects the primary winding to the reference potential when the amplitude of the voltage applied to the smoothing capacitor

Primary DC voltage exceeds a predetermined threshold, which is dependent on the breakdown voltage of the Zener diode.

It proves to be particularly advantageous if a parallel to the Zener diode

is provided and different from the smoothing capacitor capacitor, which is dimensioned smaller compared to the smoothing capacitor. Then, the zener diode causes the current flow through the primary winding, if one at this

Capacitor voltage applied exceeds the breakdown voltage of the Zener diode. In this way, it is possible to generate a rectangular or alternating current flow through the primary winding, so that the energy of the

Primary winding can be transmitted to the secondary winding. Namely, when the amplitude of the capacitor connected in parallel with the zener diode reaches the breakdown voltage of the zener diode, the zener diode is turned on so that electric current flows through the primary winding. The parallel to the Zener diode switched

Capacitor is then discharged, and the zener diode locks again. Because the

Smoothing capacitor is significantly larger than the parallel connected to the Zener diode capacitor and is designed for operation at higher voltages, the small capacitor is charged again with electrical energy, and the zener diode is turned on again. This switching process is repeated until the smoothing capacitor is discharged and the amplitude of the primary DC voltage again reaches a minimum.

The current limiting element may be dimensioned such that in the standby mode, a charging process of the smoothing capacitor lasts longer than its discharging process effected by the switching device. After a switching operation of the switching device then the current flow through the primary winding is blocked until the

Smoothing capacitor is recharged and the amplitude of the primary DC voltage again reaches the threshold. Between the switching operations of the switching device thus takes place in each case a charging of the smoothing capacitor. Unlike in the Operating mode in which the smoothing capacitor bypassing the

Current limiting element can always be charged continuously and the switching device can continuously cause the flow of current through the primary coil, electrical energy is saved in standby mode, therefore, because the switching device is only temporarily turned on. In particular, the current-limiting element can be dimensioned such that just an electrical charging current can flow through the smoothing capacitor, which causes slow charging of the battery

Smoothing capacitor causes electrical energy. On the one hand, therefore, in the

Standby state electrical energy can be transferred from the primary side to the secondary side; On the other hand, the energy consumption in standby mode is particularly low.

With regard to the arrangement of the current limiting element, it proves to be advantageous if this is arranged between the line filter on the one hand and the rectifier on the other. Thus, the power consumption of all the current limiting element downstream components is reduced to a minimum in standby mode.

At the secondary winding of the transformer, the secondary voltage can be tapped. The secondary winding may also be followed by a rectifier - such as a diode -, and parallel to the secondary winding, a capacitor may be connected, which smoothes the secondary voltage, so that at this capacitor

Secondary DC voltage can be tapped. The electrical load can be supplied with this smoothed secondary DC voltage.

Such a consumer may be, for example, said electrical switch, which serves to bridge the current limiting element. The secondary voltage can therefore be used to close the electrical switch and thereby to switch the circuit arrangement from the standby mode to the operating mode. The household appliance can thus always be reliably and effectively switched to the operating mode.

Additionally or alternatively, such an electrical load can also be a standby control unit, which is supplied with the secondary voltage in standby mode. This standby control unit can monitor in standby mode whether operator signals present, due to which the electrical switch is closed and the household appliance to be switched to the operating mode.

An inventive method is designed for operating a circuit arrangement of a household appliance, which is switched between an operating mode and a standby mode. It will be an AC electrical voltage on one

Circuit input of the circuit arrangement created. The alternating voltage is rectified by means of a rectifier connected downstream of a line filter. The rectified AC voltage is smoothed by means of a rectifier downstream smoothing capacitor, so that on the smoothing capacitor

Primary DC voltage applied. The primary DC voltage is at the

Smoothing capacitor tapped by a switching power supply, which from the tapped primary DC voltage, a secondary voltage with respect to the

Primary DC voltage provides changed amplitude with which an electrical load of the household appliance is supplied. The switched-mode power supply comprises a transformer having a primary winding which is coupled to the smoothing capacitor and a secondary winding to which the secondary voltage for the electrical load is tapped. The switching power supply further comprises a switching device connected in series with the primary winding, which controls a current flow through the primary winding. The circuit arrangement also includes means which reduce the amplitude of the primary DC voltage in standby mode so that the amplitude of the primary DC voltage in the standby mode is lower than in the standby mode

Operating mode is. The means for reducing the amplitude comprise a different from the line filter and connected in series to the switching power supply

Current limiting element, which measures the current through the

Smoothing capacitor flowing charging current limited, wherein by means of an electrical switch, the current limiting element is bridged in the operating mode.

The preferred embodiments presented with reference to the household appliance according to the invention and their advantages apply correspondingly to the method according to the invention.

Further features of the invention will become apparent from the claims, the figures and the description of the figures. All the features mentioned above in the description and Feature combinations as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures are not only in the respectively indicated combination but also in others

Combinations or used alone.

The invention will now be described with reference to individual preferred embodiments, as well as with reference to the accompanying drawings.

Show it:

1 is a schematic representation of a circuit arrangement of a

Household appliance according to an embodiment of the invention;

FIG. 2 is a schematic representation of the circuit arrangement according to FIG. 1, wherein components of a switched-mode power supply are shown in detail; FIG.

3 shows a schematic illustration of a switching device of the switched-mode power supply;

and

4a to 4c show a time course of a primary DC voltage, a temporal

Course of a falling at a Zener diode electrical voltage and a time course of a secondary DC voltage.

A circuit arrangement 1 shown in FIG. 1 is used to operate a

Household appliance (not shown). The circuit 1 - like the household appliance - can be switched back and forth between an operating mode and a standby mode.

The standby mode represents a power saving mode in which electrical energy is saved.

The circuit arrangement 1 comprises a circuit input 2 with a first input terminal 3 and a second input terminal 4, between which an electrical AC voltage UN (mains voltage) is applied when the circuit input connected to an electrical power grid. With the circuit input 2, a line filter 5 is connected, which is an EMC filter (electromagnetic compatibility). This mains filter 5 includes a coil 6 connected to the first input terminal 3, and a parallel circuit comprising a capacitor 7 and a capacitor

Ohmic resistance 8.

The mains filter 5 is a rectifier 9 downstream, which, for example, a

Bridge rectifier can be. The rectifier 9 is used to rectify the

AC voltage UN, so that at an output of the rectifier 9 a

rectified AC voltage UG is provided. With the output of the

Rectifier 9 is a switching power supply 10 is connected, which provides a secondary DC voltage US from the rectified AC voltage UG. With this

Secondary DC voltage US is an electrical load 1 1 - about a standby control unit - supplied. Between the line filter 5 on the one hand and the rectifier 9 on the other hand is a

Current limiting capacitor 12 is arranged, which is connected in series with the switching power supply 10. The current limiting capacitor 12 constitutes a current limiting element in the sense of the present invention. Parallel to the current limiting capacitor 12, an electrical switch 13 is connected, by means of which the

Current limiting capacitor 12 is bridged, in the operating mode.

The switching of the household appliance from the operating mode to the standby mode thus takes place by opening the switch 13. And vice versa, the switching of the household appliance in the operating mode, ie the activation of the household appliance, by closing the electrical switch 13. The switch 13 can as a Relay with a coil 14 may be formed. The coil 14 may on the one hand be connected to an output 15 of the switched mode power supply 10 to which the secondary DC voltage US is applied; On the other hand, the coil 14 may be coupled via a switching element 16 to a reference potential 17. The switching element 16 may be, for example, an operating element which can be actuated by the user. Additionally or alternatively, the switching element 16 can be automatically actuated by means of the electrical load 1 1 (standby control unit). By closing the switching element 16 is a current flow caused by the coil 14, so that the electric switch 13 is closed and the household appliance is switched to the operating mode.

Between the current limiting capacitor 12 on the one hand and the rectifier 9 on the other hand, a circuit node 18 is arranged. This circuit node 18 is coupled via a first voltage divider 19, which has three resistors 20, 21, 22, to one of the reference potential 17 galvanically isolated reference potential 17 '. A voltage divider node 23 may be coupled to a control unit (μθ). This allows the control unit to measure the voltage applied to the circuit node 18 electrical voltage. Via a second voltage divider 24 with resistors 25, 26, 27, the control unit can detect a frequency of the AC voltage UN. For this purpose, another voltage divider node 28 is connected to the control unit.

In Fig. 2, the circuit arrangement 1 is shown in detail, wherein the sake of clarity, the representation of the second voltage divider 24 has been omitted. Likewise, the representation of the network filter 5 has been omitted.

As is apparent from Fig. 2, the rectifier 9 includes four rectifier diodes and is designed as a bridge rectifier. The rectifier 9, the switching power supply 10 is connected downstream, which is now shown in detail in Fig. 2. The switching power supply 10 includes a smoothing capacitor 29, which is connected downstream of the rectifier 9 and is located between a node 30 and a reference potential 31. Of the

Smoothing capacitor 29 is designed for operation at relatively high voltages, namely at voltages of 400V. The smoothing capacitor 29 is used for smoothing the rectified voltage UG, so that on the smoothing capacitor

Primary DC voltage UP is applied.

The smoothing capacitor 29 may be integrated into the switched-mode power supply 10 or it may be a separate component from the switched mode power supply 10. The switching power supply 10 includes a transformer 32, which has a primary winding 33 on the one hand and a secondary winding 34 on the other hand. In series to

Primary winding 33 is connected to a switching device 35, which is used to control a current flow through the primary winding 33 and thus for controlling the Energy transfer from the primary winding 33 to the secondary winding 34 is formed. About the switching device 35, the primary winding 33 namely with the

Reference potential 31 are connected. The switching device 35 is also coupled via a capacitor 36 to the reference potential 31. On the secondary side, the switching power supply 10 includes a rectifier 37, which is electrically connected to the secondary winding 34 and formed in the embodiment in the form of a single diode. The cathode of this diode is coupled via a capacitor 38 to the secondary-side reference potential 17, so that the capacitor 38 is connected substantially parallel to the secondary winding 34.

At the secondary winding 34 drops a secondary voltage US 'from which a

AC voltage is. This secondary voltage US 'is rectified by means of the rectifier 37 and smoothed by means of the capacitor 38, so that the above-mentioned secondary DC voltage US applied to the capacitor 38, which can be tapped from the electrical load 1 1 and serve to close the electrical switch 13.

In Fig. 3 is a schematic diagram of the switching device 35 is shown, wherein the

Functioning of the circuit 1 will be explained in more detail. In Fig. 3 has been dispensed with the representation of the primary winding 33 and other components. These

Primary winding 33 is however - as shown in Fig. 2 - connected in series with the switching device 35, namely between a node 39 and the switching device 35. Parallel to the series circuit of the primary winding 33 and the switching device 35, the smoothing capacitor 29 is connected, ie between the Node 39 and the

Reference potential 31. At this smoothing capacitor 29 is applied to the primary DC voltage UP. In series with the switching device 35, the current limiting capacitor 12 is also connected, whose operation will be described in more detail below.

The switching device 35 comprises a Zener diode 40, the cathode of which is connected to a node 41 and whose anode is connected to the reference potential 31. Parallel to the Zener diode 40, that is, between the node 41 and the reference potential 31, the above-mentioned capacitor 36 is connected to which an electrical voltage UK is applied. So the cathode of the zener diode 40 is connected to the primary winding 33 and the Current limiting capacitor 12 coupled while its anode is directly connected to the reference potential 31.

While the smoothing capacitor 29 is designed to operate at high voltages, namely at voltages of about 400V, the capacitor 36 is designed to operate at lower voltages, namely at voltages of about 10V to 16V. The capacitor 36 is thus dimensioned significantly smaller than the smoothing capacitor 29. To separate these two voltage levels from each other, a device 42 is connected between the two nodes 39 and 41, which, for example, as

Voltage regulator or voltage divider or as a resistor with a dynamically variable resistance value can be realized. By using this device 42 is achieved that flows through the capacitor 36, a lower current than through the smoothing capacitor 29, so that due to the different dimensions of the capacitors 29 on the one hand and 36 on the other hand substantially the same or approximately the same charging times of the two capacitors 29, 36 can be achieved ,

In standby mode, the electrical switch 13 (see FIG. 2) is opened so that an electric current flows through the current limiting capacitor 12. Of the

Current limiting capacitor 12 throttles the current and thus reduces the amplitude of the primary DC voltage UP in standby mode. The current limiting capacitor 12 is dimensioned such that the amplitude of the primary DC voltage UP in standby mode can reach a value from a value range of 16V to 20V. As already stated, however, the amplitude of the voltage UK is about 10V to 16V. The current limiting capacitor 12 is thus dimensioned so that in standby mode just by the smoothing capacitor 29, an electric current can flow and thus this smoothing capacitor 29 can charge slowly. The at the

Switching power supply 10 in standby mode delivered electrical power is less than a convertible from the power supply 10 power. This means that the

Charging the smoothing capacitor 29 lasts longer than its discharge due to the energy transfer to the secondary side of the transformer 32. The smoothing capacitor 29 is thus charged slowly, then the transmission of the energy stored in the smoothing capacitor 29 to the secondary side, so that the Smoothing capacitor 29 is discharged, and then the smoothing capacitor 29 is recharged.

In standby mode, the two capacitors, namely the smoothing capacitor 29 and the capacitor 36, are charged. If the amplitude of the primary DC voltage UP reaches a threshold value depending on the breakdown voltage of the zener diode 40 or if the amplitude of the voltage UK exceeds the breakdown voltage of the zener diode 40, the zener diode 40 is turned on so that the primary winding 33 is conductively connected to the reference potential 31. It flows through the primary winding 33, an electric current. The energy is now out of the

Smoothing capacitor 29 transferred to the secondary side of the transformer 32. Because the capacitor 36 is dimensioned much smaller, this capacitor 36 is discharged much faster than the smoothing capacitor 29. The amplitude of the voltage UK thus decreases relatively quickly, so that the zener diode 40 blocks. Then the capacitor 36 is recharged and the amplitude of the voltage UK reaches again

Breakdown voltage of the zener diode 40. The zener diode 40 is again turned on. Such a switching back and forth of the Zener diode 40 takes place until all the energy is transferred from the smoothing capacitor 29 to the secondary side and the smoothing capacitor 29 is thus discharged. Then the

Smoothing capacitor 29 recharged, and the above switching operations start again.

This mode of operation will now be explained in more detail with reference to FIGS. 4a to 4c. FIG. 4 a shows a profile of the primary direct voltage UP over time t. 4b, however, shows a time profile of the voltage drop across the capacitor 36 UK. Finally, Fig. 4c shows a time course of the secondary DC voltage US. During a time interval T1, the two capacitors 29, 36 are charged with electrical energy, so that the respective amplitudes of the

DC primary voltage UP and the voltage UK increase continuously. At a time T2, the amplitude of the primary DC voltage UP reaches the threshold value M, and the amplitude of the voltage UK reaches the breakdown voltage of the zener diode 40. From time T2, the zener diode 40 thus becomes conductive and causes a

Current flow through the primary winding 33. During a time interval T1 subsequent to the time interval T3, the capacitor 36 is alternately charged and discharged and the Zener diode 40 is alternately switched between the conductive and the off-state. As stated above, the capacitor 36 discharges particularly quickly and can be recharged quickly. During the

Time interval T3 thus drops an alternating voltage at the capacitor 36, so that an alternating current also flows through the primary winding 33, so that the energy from the smoothing capacitor 29 can be transmitted to the secondary side. This switching back and forth of the zener diode 40 lasts until the smoothing capacitor 29 is discharged again or the amplitude of the primary direct voltage UP reaches a minimum W. At this time, the capacitor 38 on the secondary side is already charged - this is charged during the time interval T3. After the expiration of the time interval T3, the capacitors 29 and 36 must be recharged, while the amplitude of the secondary DC voltage US slowly decreases. The switching operations of the zener diode 40 are then repeated after a further time interval T4.

The current limiting capacitor 12 is thus dimensioned so small that the output to the switching power supply 10 electrical power is less than a power requirement of the switching power supply 10. If the household appliance is activated or the

Current limiting capacitor 12 bridged with the switch 13, so is the

Smoothing capacitor 29 continuously charged, so that the transmission of energy to the secondary side can be carried out continuously.

LIST OF REFERENCE NUMBERS

1 circuit arrangement

2 circuit input

3 input connection

4 input connection

5 line filter

6 coil

7 capacitor

8 ohmic resistance

9 rectifier

10 switching power supply

1 1 electrical consumers

12 current limiting capacitor

13 electrical switch

14 coil

15 output

16 switching element

17 reference potential

18 circuit nodes

19 voltage dividers

20, 21, 22 resistors

23 voltage divider node

24 voltage dividers

25, 26, 27 resistors

28 voltage divider node

20 smoothing capacitor

30 knots

31 reference potential

32 transformer

33 primary winding

34 secondary winding

35 switching device

36 capacitor 37 rectifier

38 capacitor

39 knots

40 zener diode

41 knots

42 establishment

M threshold

t time

T1 time interval

T2 time

T3 time interval

T4 time interval

UG rectified AC voltage

UK tension

UN AC voltage

UP primary DC voltage

US secondary DC voltage

US 'secondary voltage

W minimum

Claims

claims

1. Household appliance with an electrical circuit arrangement (1) which can be switched between an operating mode and a standby mode and which comprises:

a circuit input (2) having a first and a second input terminal (3, 4), between which an AC voltage (UN) can be applied,

a line filter (5) coupled to the circuit input (2), a rectifier (9) connected downstream of the line filter (5) for rectifying the alternating voltage (UN),

a smoothing capacitor (29) connected downstream of the rectifier (9) for smoothing the rectified AC voltage (UN) so that a DC primary voltage (UP) is applied to the smoothing capacitor (29), a switching power supply (10) coupled to the smoothing capacitor (29) the smoothing capacitor (29) picks up the primary DC voltage (UP) and is adapted to the tapped

Primary DC voltage (UP) to provide a secondary voltage (US ') with respect to the primary DC voltage (UP) changed amplitude, with which an electrical load (1 1, 14) of the household appliance can be supplied,

wherein the switched-mode power supply (10) comprises a transformer (32) having a primary winding (33) which is coupled to the smoothing capacitor (29) and a secondary winding (34) to which the secondary voltage (US ') for the electrical load (US') 1 1, 14) can be tapped off,

the switching power supply (10) further comprising a switching device (35) connected in series with the primary winding (33) for controlling a current flow through the primary winding (33),

and wherein the circuit arrangement (1) has means (12) for reducing the amplitude of the primary direct voltage (UP) in the standby mode, so that the amplitude of the primary direct voltage (UP) in the standby mode is lower than in the operating mode, characterized in that

the means (12) for reducing the amplitude of the network filter (5) different and in series with the switching power supply (10) connected passive current limiting element (12), which for limiting the

Amount of current flowing through the smoothing capacitor (29) charging current is formed, wherein an electrical switch (13) parallel to

Current limiting element (12) is connected, by means of which the

Current limiting element (12) is bridged in the operating mode.

2. Household appliance according to claim 1, characterized in that the

Current limiting element (12) is a current limiting capacitor, wherein a capacitive voltage divider is formed by the current limiting capacitor and the smoothing capacitor (29).

3. Household appliance according to claim 1 or 2, characterized in that the

Circuit arrangement (1) is designed so that exclusively the

Current limiting element (12) by means of the switch (13) can be bridged.

4. Household appliance according to one of the preceding claims, characterized

characterized in that waiving further components, the means (12) for reducing the amplitude exclusively the current limiting element (12).

5. Household appliance according to one of the preceding claims, characterized

characterized in that the switching device (35) comprises a Zener diode (40) whose cathode is connected to the primary winding (33) and whose anode is connected to a

Reference potential (31) are coupled, so that by the primary winding (33), an electric current flows when the amplitude of the smoothing capacitor (29) falling primary DC voltage (UP) reaches one of the breakdown voltage of the Zener diode (40) dependent threshold (M).

6. Household appliance according to claim 5, characterized by a parallel to the Zener diode (40) connected capacitor (36), which in relation to the

Smoothing capacitor (29) is dimensioned smaller, so that the Zener diode (40) causes the current flow through the primary winding (33) when a voltage applied to this capacitor (36) voltage (UK) exceeds the breakdown voltage of the zener diode (40).

7. Household appliance according to one of the preceding claims, characterized

characterized in that the current limiting element (12) is dimensioned such that in standby mode, a charging of the smoothing capacitor (29) lasts longer than its by the switching device (35) effected discharge, so that after a switching operation of the switching device (35) selbige the current flow through the primary winding (33) blocks until the smoothing capacitor (29) is recharged.

8. Household appliance, characterized in that between the line filter (5) and the rectifier (9), the current limiting element (12) is connected.

9. domestic appliance, characterized in that the electrical switch (13) is an electrical load (1 1, 14), so that the secondary voltage (US ') for closing the electrical switch (13) and thereby to switch the circuit arrangement (1) from standby mode to operating mode.

10. Household appliance, characterized in that with the secondary voltage (US ') a standby control unit (1 1) as an electrical consumer (1 1, 14) can be supplied in standby mode.

1 1. A method for operating a circuit arrangement (1) of a household appliance, which is switched between an operating mode and a standby mode, with the steps:

Applying an AC electrical voltage (UN) to a

Circuit input (2) of the circuit arrangement (1),

Rectification of the alternating voltage (UN) by means of a rectifier (9) connected downstream of a line filter (5), - Smoothing the rectified AC voltage (UN) by means of a

Rectifier (9) downstream smoothing capacitor (29), so that on the smoothing capacitor (29) is applied a Primärgleichspannung (UP), tapping the Primärgleichspannung (UP) on the smoothing capacitor (29) by means of a switching power supply (10), which from the tapped primary DC voltage ( UP) provides a secondary voltage (US ') with a relation to the primary DC voltage (UP) changed amplitude, with which an electrical load (1 1, 14) of the

Household appliance is supplied,

wherein the switching power supply (10) comprises a transformer (32) having a

Primary winding (33) coupled to the smoothing capacitor (29) and having a secondary winding (34) to which the

Secondary voltage (US ') for the electrical load (1 1, 14) is tapped,

wherein the switching power supply (10) further comprises a switching device (35) connected in series with the primary winding (33), which controls a current flow through the primary winding (33),

and wherein the circuit arrangement (1) has means (12) for reducing the amplitude of the primary direct voltage (UP) in the standby mode, so that the amplitude of the primary direct voltage (UP) in the standby mode is lower than in the operating mode,

characterized in that

the means (12) for reducing the amplitude of the line filter (5)

various and in series with the switched mode power supply (10) switched passive current limiting element (12) which limits the current strength of the smoothing capacitor (29) flowing charge current, wherein by means of an electrical switch (13), the current limiting element (12) in

Operating mode is bridged.