DE102017206098A1 - Line filter with ripple protection - Google Patents

Abstract

A network filter (100) for coupling a circuit (109) of an electrical appliance to a supply network is described. In this case, the supply network provides a supply current (200) with a grid frequency. The line filter (100) comprises a start-up and / or fuse resistor (104), which is coupled on a first side to a first supply line (101) of the supply network. In addition, the line filter (100) comprises an X-capacitor (105) which is coupled on a first side to a second side of the start-up and / or fuse resistor (104) and on a second side to a second supply line (102) of the supply network , The line filter (100) further includes a choke (106) having the second side of the starting and / or Sicherungswiderstands (104) with a first contact point and the second supply line (102) having a contact point for the circuit (109) of the electrical Device connects. In addition, the line filter (100) comprises a protection circuit (304) which is set up to at least partially bypass a noise current of the supply current (200) with an interference frequency which is above the network frequency at the startup and / or fuse resistor (104).

Description

The invention relates to a line filter (also referred to as line filter circuit) with a ripple protection for a start-up and / or backup resistor of the line filter.

An electrical device, e.g. a domestic appliance or a household appliance, which is operated with electrical energy from an AC supply network (eg from a 230V or from a 130V network), typically has a line filter, which between the supply network and a circuit of the electrical device (in particular a Rectifier of the electrical device) is arranged. The line filter (or the line filter circuit) typically has the task of limiting electrical interference from the electrical device to the supply network and / or increasing the electromagnetic compatibility of the electrical device against interference from the supply network.

A line filter may have a start-up and / or fuse resistor to limit the flow of current into the electrical device when switching on the electrical device and / or in a short-circuit situation of the electrical device. The startup and / or backup resistor can be charged and possibly damaged in case of disturbances of the supply network, in particular in the case of current ripples of the supply current.

The present document deals with the technical problem to provide a line filter or a line filter circuit with a start-up and / or fuse resistor, the or a cost-effective and reliable protection of the starting and / or backup resistor from interference, especially from high-frequency interference, of the supply network.

The object is solved by the subject matter of the independent patent claim. Advantageous embodiments are defined in particular in the dependent claims, described in the following description or illustrated in the accompanying drawings.

According to one aspect of the invention, a line filter (or a line filter circuit) for an electrical device, in particular for a domestic appliance or for a household appliance, such as for a washing machine, a dishwasher, a tumble dryer, etc., is described. The line filter is configured to couple a circuit (e.g., a control circuit) of the electrical device to a utility network, the utility network providing a supply current at a network frequency. The supply network can be a 230V or a 130V AC mains. The mains frequency can be 50Hz or 60Hz. The circuit may comprise a rectifier, in particular a bridge rectifier. Furthermore, the circuit can have one or more intermediate circuit capacitors, which are charged when the electrical device is switched on from the supply network (and thus via the mains filter).

The line filter includes a start-up and / or fuse resistor coupled on a first side of the start-up and / or fuse resistor to a first supply line (e.g., a phase line) of the utility grid. The starting and / or securing resistor can be designed to limit a current flow, in particular an inrush current, into the circuit (in particular into one or more DC link capacitors) of the electrical device.

In addition, the line filter comprises an X-capacitor, on a first side of the X-capacitor with a second side of the starting and / or backup resistor and on a second side of the X-capacitor with a second supply line (eg with a neutral line) of the supply network is coupled. The X-capacitor can be designed to dampen interference voltage between the leads.

The line filter may further comprise a choke, which connects the second side of the start-up and / or Sicherungswiderstands with a first contact point and the second lead to a second contact point for the circuit of the electrical device. In particular, a first input of the throttle may be coupled to the second side of the starting and / or securing resistor, and a first output of the throttle may be coupled to the first contact point. Furthermore, a second input of the throttle can be coupled to the second supply line and a second output of the throttle can be coupled to the second contact point. Through the throttle currents can be suppressed, which flow in the same direction over the supply lines.

In addition, the line filter comprises a protection circuit which is set up to at least partially bypass a noise current of the supply current to the startup and / or backup resistor. The interference current has an interference frequency, wherein the interference frequency is above the mains frequency. The noise frequency can be e.g. in a frequency range of 100Hz to 1MHz, especially from 50kHz to 1MHz. The parasitic currents can be caused by a current ripple of the supply current.

As a result, the high-frequency interference currents are at least partially passed by the start-up and / or backup resistor, the Load of the starting and / or securing resistor can be reduced.

The protection circuit may include a protection capacitor arranged in parallel with the start-up and / or fuse resistor. The protective capacitor and the X-capacitor can form a capacitive voltage divider, by which a voltage drop across the starting and / or securing resistor can be limited or reduced. For example, the protection capacitor may have a capacitance of 200nF or more. By providing a protection capacitor, the load of the starting and / or securing resistor can be reduced in an efficient manner.

The protection circuit may be configured such that heating of the start-up and / or fuse resistance by a remaining portion of the parasitic current flowing through the start-up and / or fuse resistor is equal to or less than a heating threshold. The heating threshold may e.g. be at 200 ° C. The dimensioning of the protection circuit can be carried out as a function of the impedance of the starting and / or backup resistor, as a function of the impedance of the X-capacitor and in dependence of the impedance of the throttle.

The line filter may further include a first Y capacitor disposed between the first output of the choke and / or between the first contact portion of the circuit and the ground of the electrical device. In addition, the line filter may comprise a second Y-capacitor, which is arranged between the mass of the electrical device and the second output of the choke and / or the second contact part of the circuit. Thus, interference voltages that occur on the supply lines to ground, can be compensated.

It should be noted that all aspects of the network filter described in this document can be combined in a variety of ways. In particular, the features of the claims can be combined in a variety of ways.

• 1 ein Schaltbild eines beispielhaften Netzfilters bzw. einer beispielhaften Netzfilterschaltung;
• 2 den zeitlichen Verlauf eines beispielhaften Netzstroms; und
• 3 ein Schaltbild eines beispielhaften Netzfilters mit einer Schutzschaltung.

Furthermore, the invention will be described with reference to embodiments illustrated in the accompanying drawings. Show

• 1 a circuit diagram of an exemplary network filter and an exemplary network filter circuit;
• 2 the time course of an exemplary network power; and
• 3 a circuit diagram of an exemplary network filter with a protection circuit.

As set forth above, the present document is concerned with the provision of a reliable mains filter for an electrical device. In this context shows 1 an exemplary network filter 100 , via the supply or supply lines 101 . 102 . 103 with a supply network, in particular with an AC (Alternating Current) supply network, can be connected. The supply lines include, for example, a phase line 101 , a neutral line 102 and a protective line 103 , where the protective line 103 typically connected to the ground of the electrical device.

The net filter 100 includes, for example, an X-capacitor 105 , which can be used to interference voltages between the leads 101 . 102 (ie between the phase and outer line 101 and the neutral line 102 ) to dampen. A first contact or a first side of the X-capacitor 105 is for this purpose with a first supply line 101 (eg the phase line) and a second contact or a second side of the X-capacitor 105 is with a second supply line 102 (eg the neutral line) connected.

Furthermore, the network filter 100 a throttle 106 , in particular a current-compensated throttle, having, with the throttle 106 Common mode interference currents or "common mode" currents, ie currents flowing in the same direction on the supply lines 101 . 102 flow, can be suppressed. In addition, the net filter can 100 Y capacitors 107 . 108 which are used to generate interference voltages in the same phase on the supply lines 101 . 102 to earth or earth to suppress. The net filter 100 is then the output side via contact parts with a circuit 109 of the electrical device, eg coupled to a rectifier.

The circuit 109 of the electrical device typically includes one or more DC link capacitors that are charged upon startup of the electrical device, thereby causing a relatively high inrush current. Furthermore, there may be a short circuit in the circuit 109 of an electrical device, which in turn causes relatively high currents through the line filter 100 can be effected. The net filter 100 may for this purpose a start-up and / or backup resistor 104 have, in a current path of a supply line 101 . 102 (eg the phase line 101 ) is arranged. Due to the starting and / or fuse resistance 104 can the flow of current in the line filter 100 and / or in the circuit 109 be limited.

The supply current provided by the utility grid may have relatively high ripples. Such ripples can be caused, for example, by disturbances of other components connected to the supply network (eg by switching power supplies). For example, solar power can be fed via switched inverter in the supply network, the injected current has a relatively high ripple. 2 shows the time course of an exemplary supply current 200 , Also shows 2 the current ripple 201 of the supply current 200 , The current ripple 201 typically has a ripple frequency (eg in the range of 70-80kHz) that is substantially above the line frequency (eg 50Hz or 60Hz) of the supply current 200 lies. In particular, the interference frequency by the factor 100 . 1000 or more above the mains frequency.

The X-capacitor 105 represents with respect to the high-frequency current ripple 201 a short-circuit. As a result, a current loop on the start-up and / or backup resistor 104 causes. In other words, the start-up and / or fuse resistance 104 is in relation to the current ripple 201 parallel to the supply lines 101 . 102 arranged so that a noise current on the starting and / or securing resistor 104 flows. This interference current causes ohmic losses and thus heating of the starting and / or fuse resistance 104 , Consequently, the starting and / or securing resistor becomes 104 through the current ripple 201 burdened and possibly damaged.

3 shows a line filter 100 with a protection circuit 304 to protect the starting and / or fuse resistance 104 in front of high-frequency current ripple 201 of the supply current 200 , The protection circuit 304 includes a parallel to the starting and / or backup resistor 104 arranged protective capacitor. The protection capacitor carries a portion of the current through the ripple 201 caused interference current to the starting and / or backup resistor 104 passing, so that the load of the starting and / or fuse resistance 104 is reduced. In this case, the protective capacitor forms a capacitive voltage divider with the X-capacitor 105 ,

The protective capacitor can be dimensioned such that the heating of the starting and / or backup resistor 104 by the remaining portion of the interference current, the on the starting and / or backup resistor 104 flows equal to or less than a predefined heating threshold. In this case, a frequency range of 100Hz to 1MHz can be considered for the interference current. Furthermore, a heating threshold of 200 ° C can be considered.

The disturbance current, via the start-up and / or fuse resistance 104 flows, by looking at the impedance of the starting and / or securing resistor 104 , the impedance of the protection capacitor and the impedance of the remaining network filter 100 (including the following circuit 109 ) are calculated. By adapting the impedance, in particular by adapting the capacitance of the protective capacitor then the interference current through the start-up and / or backup resistor 104 and thus the load of the starting and / or fuse resistance 104 be limited.

By the protection circuit described in this document 304 may be the start-up and / or fuse resistance 104 a network filter 100 in an efficient and reliable way against current ripples 201 to be protected. Thus, failures of an electrical device can be avoided.

The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and the figures are intended to illustrate only the principle of the proposed network filter.

Claims (10)

A line filter (100) for coupling a circuit (109) of an electrical device to a utility network; the utility network providing a supply current (200) at a grid frequency; the net filter (100) comprising - A start-up and / or backup resistor (104) which is coupled on a first side with a first supply line (101) of the supply network; - An X-capacitor (105) which is coupled on a first side with a second side of the start-up and / or Sicherungswiderstands (104) and on a second side with a second supply line (102) of the supply network; - A choke (106) which connects the second side of the starting and / or Sicherungswiderstands (104) with a first contact point and the second supply line (102) with a second contact point for the circuit (109) of the electrical device; and - A protection circuit (304) which is adapted to pass a noise current of the supply current (200) with a noise frequency, which is above the mains frequency, at least partially past the start-up and / or fuse resistor (104). Line filter (100) according to Claim 1 wherein the protection circuit (304) comprises a protection capacitor arranged in parallel with the start-up and / or fuse resistor (104). Line filter (100) according to Claim 2 wherein the protection capacitor and the X-capacitor (105) form a capacitive voltage divider, by which a voltage drop across the start-up and / or fuse resistor (104) is limited. Line filter (100) according to Claim 3 wherein the protection capacitor has a capacitance of 200nF or more. A line filter (100) according to any one of the preceding claims, wherein the protection circuit (304) is designed such that a heating of the start-up and / or fuse resistor (104) by a remaining portion of the interference current, by the start-up and / or fuse resistor ( 104) is equal to or less than a heating threshold. A line filter (100) according to any preceding claim, wherein the protection circuit (304) operates in response to an impedance of the start-up and / or fuse resistor (104), in response to an impedance of the X-capacitor (105) and in response to an impedance the throttle (106) is dimensioned. Line filter (100) according to one of the preceding claims, wherein the starting and / or securing resistor (104) is designed to limit a current flow, in particular an inrush current, into the circuit (109) of the electrical device. Line filter (100) according to one of the preceding claims, wherein the mains frequency is 50 Hz or 60 Hz, and wherein the interference frequency in a frequency range of 100Hz to 1MHz, in particular from 50kHz to 1MHz, is located. Line filter (100) according to one of the preceding claims, wherein the first supply line (101) corresponds to a phase line and the second supply line (102) corresponds to a neutral line. Line filter (100) according to one of the preceding claims, wherein - The line filter (100) comprises a first Y-capacitor (107) which is arranged between a first output of the choke (106) and / or the first contact part of the circuit (109) and a mass of the electrical device; and - The line filter (100) comprises a second Y-capacitor (108) which is arranged between the mass of the electrical device and a second output of the throttle (106) and / or the second contact part of the circuit (109).

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