ELECTRONIC SWITCH AS A DAMPING ELEMENT

Abstract

An electronic switch for connecting units of a power supply system has a semiconductor switch, an actuation circuit and a current/voltage sensor for detecting current flow through the electronic switch. The actuation circuit operates the semiconductor switch, depending on oscillations measured by the current/voltage sensor, in an activated state, a deactivated state or a linear mode. A power supply system having the electronic switch for connecting with the electronic switch two electrical sub-networks and a method for operating the electronic switch are also disclosed. The semiconductor switch is operated at least temporarily in the linear mode for damping oscillations.

Claims

1.-2. (canceled)

13. An electronic switch for connecting two sub-networks of a power supply system, the electronic switch comprising: a semiconductor switch constructed to carry and disconnect a current in two directions, a current sensor for detecting a current flowing through the electronic switch or a voltage sensor, an actuation circuit connected to the semiconductor switch and configured to operate the semiconductor switch, depending on oscillations measured by the current sensor and/or by the voltage sensor, in an activated state, in a deactivated state or in a linear mode, wherein the actuation circuit is further designed as a damping resistor to damp oscillations when operating in the linear mode.

14. The electronic switch of claim 13, wherein a reactive current is reduced in the linear mode.

15. The electronic switch of claim 13, wherein the electronic switch is designed to damp oscillations caused by transient phenomena resulting from a switching action of the electronic switch.

16. The electronic switch of claim 13, wherein the electronic switch is designed to damp oscillations caused by transient phenomena between the sub-networks.

17. A power supply system, comprising: two electrical sub-networks, an electronic switch detachably interconnecting the two electrical sub-networks, wherein the electronic switch comprises a semiconductor switch constructed to carry and disconnect a current in two directions, a current sensor for detecting a current flowing through the electronic switch or a voltage sensor, an actuation circuit connected to the semiconductor switch and configured to operate the semiconductor switch, depending on oscillations measured by the current sensor and/or by the voltage sensor, in an activated state, in a deactivated state or in a linear mode, wherein the actuation circuit is further designed as a damping resistor to damp oscillations when operating in the linear mode.

18. The power supply system of claim 17, wherein the power supply system is embodied as a DC voltage network.

19. The power supply system of claim 17, wherein the actuation circuit is designed to damp oscillations between the two electrical sub-networks caused by transient phenomena between the two sub-networks as a result of switching of the electronic switch.

20. A method for operating an electronic switch configured to connect two sub-networks of a power supply system or for operating a power supply system employing the electronic switch, wherein the electronic switch comprises a semiconductor switch constructed to carry and disconnect a current in two directions, a current sensor for detecting a current flowing through the electronic switch or a voltage sensor, an actuation circuit connected to the semiconductor switch and configured to operate the semiconductor switch in an activated state, in a deactivated state or in a linear mode, the method comprising: operating the semiconductor switch at least temporarily in the linear mode to damp oscillations, and operating the semiconductor switch in the linear mode when the current sensor or the voltage sensor identifies an oscillation having an amplitude that exceeds a predefined limit value.

21. The method of claim 20, wherein the oscillation results from an excitation of a resonance generated by inductive components and capacitive components in the power supply system when the electronic switch is switched on.

22. The method of claim 20, further comprising: to identify the oscillation, dividing the measurement value of the current sensor or of the voltage sensor into a DC component and an AC component, and operating the semiconductor switch in the linear mode when the AC component exceeds a second predefined limit value.

23. The method of claim 22, further comprising operating the semiconductor switch in the activated state once the oscillation has decayed due to damping by the electronic switch.

24. The method of claim 20, wherein the power supply system has an electrical load, the method further comprising operating the electronic switch in the linear mode in response to a change in a target value of the electrical load, in particular in response to an abrupt change in the target value.

25. The method of claim 20, further comprising: emulating a damping resistor when the actuation circuit is operating in the linear mode, and establishing a resistance value of the damping resistor as a function of the measurement value of the current sensor or of the voltage sensor.

26. The method of claim 20, wherein when the electronic switch is switched on, the semiconductor switch changes in a first step from the deactivated state to the linear mode and in a second step from the linear mode to the activated state.

Description

[0030] The invention is described and explained in greater detail below on the basis of the exemplary embodiments illustrated in the figures, in which:

[0031] FIG. 1 shows an electronic switch,

[0032] FIG. 2 shows a power supply system with an electronic switch, and

[0033] FIG. 3 to FIG. 6 show a time characteristic during activation of the electronic switch.

[0034] FIG. 1 shows an electronic switch 1. This has a semiconductor switch 2 which with its two semiconductors can carry and disconnect a current in both directions. The semiconductor switch 2 with its semiconductors is controlled by an actuation circuit 3. This actuation circuit 3 enables the semiconductor switch 2 and thus the semiconductor arranged therein to be transferred to an activated state, a deactivated state and a linear mode. The activated state is called the conductive state, closed state or ON state. The deactivated state is also called the nonconductive state, open state or OFF state. The linear mode is also called operation in the linear range or operation in the amplification range. In this case the semiconductor switch 2 may be, but does not have to be, transferred into linear mode by the actuation circuit 3, as a function of a measured value, for example as a function of a measurement value of a current transformer 4, in order to prevent and reduce excessive currents or to damp oscillations. In this case the evaluation of the measurement value of the current transformer 4 can be carried out in the actuation circuit 3 or in a higher-level regulator and/or controller (not shown here).

[0035] FIG. 2 shows a power supply system 10, in which two sub-networks 16 of the electronic switch 1 are detachably interconnected. It is sufficient here to arrange an electronic switch in only one of the two conductors, in order to interrupt an exchange of power between the two sub-networks 16. One of the sub-networks 16 here has a power source 11 and a second of the sub-networks 16 has an electrical load 12. A further electrical load 12, for example a motor 15, is connected to the power source 11 via two other electronic switches 1. The power supply system 10 is here embodied as a DC voltage network. To support the voltage a backup capacitor 14 can be arranged here between the two conductors of the DC voltage network. In addition, further backup capacitors 14 can be arranged in a distributed manner in the power supply system. To measure currents a further current sensor 41 can as well be arranged in the power supply system 10 outside the electronic switch 1, additionally or alternatively to a current sensor 4 in the electronic switch 1. Both electronic switches 1 can influence the current measured by the further current sensor 41, since said current flows at least in part or proportionately through said electronic switch 1.

[0036] Both of these current sensors 4, 41 can be used jointly or only one of these current sensors 4, 41 can be used for the regulation or control of the electronic switch 1. For this reason no further distinction is made between the current sensor 4 and the further current sensor 41, but they are each both referred to as current sensor 4, 41. In addition it is also possible to operate the electronic switch 1 and/or the power supply system 10 without a sensor.

[0037] The electrical loads 12 are, in a first example, a motor 15 and, in a second example, a power converter 17. The motor 15 is connected to the DC voltage network directly via the electronic switch 1, i.e. without a further actuator. Hence when the electronic switch 1 is activated, high starting currents are to be expected. The behavior is similar with the power converter 17. Thanks to the intermediate circuit capacitor 13 at the input of the power converter 17, high charging currents are also to be expected here when the corresponding electronic switch 1 is activated. Both the starting currents and the charging currents can be reduced by operating the semiconductor switch 2 of the corresponding electronic switch 1 at least temporarily in linear mode.

[0038] The magnitudes shown in FIG. 2 of the system voltage U.sub.system, the voltage U.sub.1 and the current i.sub.1 will be described in greater detail below. To this end a time characteristic of the voltage U.sub.1 is specified in FIG. 3 and a time characteristic of the current i.sub.1 in FIG. 4, as could arise for example during connection of the power converter 17 to the power source 11 by the controller/regulator. These show the basic function of the electronic switch 1. In principle this behavior can also be transferred to other loads 12, such as the motor 15 for example.

[0039] With this time characteristic the electronic switch 1 should be activated so that the electrical load 12 is connected to the power source 11. Regardless of whether the electrical load 12 is a power converter 17 or a motor 15 to be connected directly to the DC voltage network, high currents in the form of charging currents or starting currents are to be expected for the moment of activation. Hence the semiconductor switch 2 of the electronic switch 1 is transferred at time t.sub.1 by the actuation circuit 3 into linear mode. This can be recognized in that the voltage U.sub.1 does not change abruptly to U.sub.system. In this mode the entire system voltage U.sub.system is not passed on to the electrical load 12, but some of it drops across the electronic switch 1. The lower voltage U.sub.1 then applied at the input of the electrical load 12 results in a reduced current i.sub.1, which is illustrated in FIG. 4. Thanks to this linear mode it is possible to limit the current below a permissible value i.sub.max or to regulate it to the value i.sub.max. At the time t.sub.2 these charging currents or starting currents are decayed, since the intermediate circuit capacitor 13 is charged up or the motor 15 is started. Thus at the time t.sub.2 or thereafter the semiconductor switch 2 can be transferred to the activated state, in which no significant electrical losses occur in the electronic switch 1. As of a further time t.sub.3 the electrical load goes into operation and draws power. This can be recognized by the rise in current there.

[0040] The electrical losses occurring in the period between t.sub.1 and t.sub.2 are only of short duration, such that they only briefly heat the electronic switch 1. Hence cooling can usually be dispensed with. Should cooling nevertheless be necessary, it can be easily implemented, usually without a fan, with an air cooling element because of the relatively small power loss.

[0041] FIG. 5 and FIG. 6 show an example of the damping of an oscillation which arises as a result of a switching action of the electronic switch 1. At the time t.sub.3 the electronic switch 1 is activated. The current i.sub.1 through the switch 1 builds up quickly. At the same time transient phenomena occur between the sub-networks 16, which are apparent in an oscillating portion, i.e. in an oscillation, of the current i.sub.1. This is identified by the current sensor 4 and/or voltage sensor and the semiconductor switch 2 of the electronic switch 1 is operated in linear mode, such that because of the voltage drop across the electronic switch 1 only a reduced voltage u.sub.1 is present at the output. The electronic switch 1 thus acts as a damping resistor in the power supply system 10, such that the oscillation declines. At a time t4 the oscillation has decayed because of the damping by the electronic switch 1, such that the semiconductor switch 2 can again be operated with low loss in the activated state. Because of the characteristic of the semiconductor it is possible to respond quickly to oscillations that occur. This enables them to be eliminated before high amplitudes are reached. Thus the power loss for the damping is also comparatively low. In this case these advantages can easily be used by exploiting the linear mode of the semiconductor switch.

[0042] To summarize, the invention relates to an electronic switch having a semiconductor switch with an actuation circuit. To improve the electronic switch it is proposed for the actuation circuit to be embodied to operate the semiconductor switch in an activated state, in a deactivated state or in linear mode. The invention further relates to a power supply system having an electronic switch of this kind, at least one power source and at least one electrical load. The invention furthermore relates to a method for operating an electronic switch of this kind or a power supply system of this kind, wherein the semiconductor switch of the electronic switch is operated at least temporarily in linear mode.

[0043] In other words the invention relates in summary to an electronic switch, wherein the electronic switch has a semiconductor switch with an actuation circuit. In order to improve the electronic switch it is proposed that the electronic switch further has a current sensor for detecting a current flowing through the electronic switch and/or a voltage sensor and the actuation circuit is designed to operate the semiconductor switch as a function of oscillations, which are measured by means of the current sensor and/or of the voltage sensor, in an activated state, in a deactivated state or in linear mode. The invention further relates to a power supply system having an electronic switch of this kind and two electrical sub-networks, wherein the two electrical sub-networks can be interconnected by means of the electronic switch. The invention further relates to a method for operating an electronic switch of this kind or a power supply system of this kind, wherein the semiconductor switch of the electronic switch is operated at least temporarily in linear mode for damping oscillations.