Electronic circuit breaker and method for operating same

Abstract

An electronic circuit breaker contains a first semiconductor switch which is switched into a current path between a voltage input and a load output and contains a controller which is connected to the control input of the first semiconductor switch. The first semiconductor switch is actuated depending on an actual value of the load current, the actual value is supplied to the controller, and the controller is configured to limit the current of the first semiconductor switch and disconnect same.

Claims

1. An electronic circuit breaker, comprising: a first semiconductor switch being switched in a current path between a voltage input and a load output, said first semiconductor switch having a control input; and a controller connected to said control input of said first semiconductor switch, wherein said first semiconductor switch being actuated in dependence on an actual value of a load current which is fed to said controller, wherein said controller is configured to limit a current of said first semiconductor switch and to switch off said first semiconductor switch, wherein said controller having a processor, a current limiting circuit and a shut-off circuit, on exceeding a maximum value by the actual value, said controller or said processor generating a signal sent to said current limiting circuit and/or to said shut-off circuit for switching off said first semiconductor switch; wherein said current limiting circuit having an input side supplied with the actual value and with a nominal setpoint value, said current limiting circuit having an adjustment element, to which the nominal setpoint value being fed on an input side and said adjustment element outputting a setpoint value on an output side; and said controller having a switch and said adjustment element having a capacitor, which is coupled with said processor by means of said switch or is discharged by means of said switch.

2. The electronic circuit breaker according to claim 1, wherein said first semiconductor switch is actuated in a current-limiting state in dependence on the actual value and on the nominal setpoint value.

3. The electronic circuit breaker according to claim 1, wherein said current limiting circuit has an operational amplifier with a first input connected to said adjustment element for feeding in the setpoint value, and a second input which is fed the actual value.

4. The electronic circuit breaker according to claim 3, wherein said operational amplifier outputs a control signal for actuating said first semiconductor switch.

5. The electronic circuit breaker according to claim 1, wherein said controller, said current limiting circuit and/or said shut-off circuit has a second semiconductor switch, which is connected to said control input of said first semiconductor switch.

6. The electronic circuit breaker according to claim 1, wherein the signal is a switch-off signal.

7. The electronic circuit breaker according to claim 1, wherein said controller supplies the actual value and the nominal setpoint value.

8. The electronic circuit breaker according to claim 4, wherein the control signal represents a difference between the setpoint value and the actual value.

9. A method for operating an electronic circuit breaker having a first semiconductor switch switched between a voltage input and a load output, the method comprises the steps of: recording an actual value of a load current or the load current is recorded as the actual value; switching the first semiconductor switch to a non-conducting state in an event of a short-circuit due to a maximum value being exceeded by the actual value, wherein in the event of the short-circuit the setpoint value of the load current being set to a minimum value and then increased continuously to a nominal setpoint value; and switching the first semiconductor switch to a current-limiting state in an event of an overload due to a setpoint value being exceeded by the actual value.

10. The method according to claim 9, which further comprises: forming a difference between the actual value and the setpoint value; and using the difference as a control signal for actuating the first semiconductor switch in the current-limiting state.

11. The method according to claim 9, wherein the first semiconductor switch actuated in the current-limiting state is switched or actuated into a non-conducting state after expiry of a specified period of time or a specified timer element.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a current-time diagram showing a temporal waveform of an output current (load current) of an electronic circuit breaker in accordance with the prior art when a short circuit occurs;

(2) FIG. 2 is a voltage-time diagram corresponding to FIG. 1, showing a waveform of a supply voltage of a current source in the event of a short circuit in accordance with the prior art;

(3) FIG. 3 is a block diagram of an electronic circuit breaker connected between a voltage input and a load output, a control input of which is connected to a control device, wherein a control device has a shut-off device and a current-limiting device;

(4) FIG. 4 is a block circuit diagram showing the electronic circuit breaker with a controllable semiconductor switch connected into a current path, and a control device provided and configured for controlling the same;

(5) FIG. 5 is a flowchart of the processing sequence of the method for operating the electronic circuit breaker;

(6) FIG. 6 is a current-time diagram of q temporal waveform of an output current (load current) in the current path in which the electronic circuit breaker configured according to the invention is connected, in a short-circuit condition, wherein by means of the electronic circuit breaker according to the invention the load current is first switched to a non-conducting state and then to a current-limiting state;

(7) FIG. 7 is a voltage-time diagram corresponding to FIG. 6 showing the waveform of the supply voltage of the current source, wherein the electronic circuit breaker according to the invention is first switched to a non-conducting state and then to a current-limiting state; and

(8) FIG. 8 is a current-time diagram showing temporal waveforms of an output current (load current) in the current path of an electronic circuit breaker configured according to the invention in the event of a short circuit for differently configured adjustment elements of the electrical circuit breaker, wherein following a shutdown of the electronic semiconductor switch the load current is controlled in a current-limiting state such that the load current is continuously increased.

DETAILED DESCRIPTION OF THE INVENTION

(9) Referring now to the figures of the drawings in detail and first, particularly to FIG. 3 thereof, there is shown an electronic circuit breaker 2 with a first semiconductor switch Q3 which is connected in a current path 3 between a voltage input 4 and a load output 6. A control input 8 of the first semiconductor switch Q3 is connected to a control device 10, wherein the control device 10 has a shut-off circuit 12, also referred to as a shut-off device 12, and a current limiting circuit 14, also referred to as a current limiting device 14. The shut-off circuit 12 in this case switches off the first semiconductor switch Q3, implemented as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor, MOS transistor), in particular in the event of a short circuit or when required, wherein the shut-off takes place relatively quickly with respect to a response time of a conventional current limiting circuit.

(10) In addition, for example, the current limiting circuit 14 is produced from comparatively inexpensive components and has a comparatively stable control behavior, in particular of the load current. As is apparent, in particular in FIGS. 6 and 8, due to the relatively rapid switching off of the first semiconductor switch Q3 only comparatively small current peaks occur. The control device 10 thus allows the use of MOSFETS which are only required to handle relatively small current peaks, thereby reducing costs and increasing reliability, for example with regard to the control stability.

(11) In this case, the first semiconductor switch Q3 is switched off (switched to the current-limiting state) as soon as its load current (output current) exceeds a maximum value I.sub.short, in particular representing a short-circuit current. The first semiconductor switch Q3 is then actuated in a current-limiting state, wherein the current limiting circuit 14 limits the load current I.sub.load, in particular its current intensity, in such a way that the load current I.sub.load, in particular its current intensity, is increased gradually (continuously, rising relatively slowly) from a minimum value I.sub.min, in particular zero, to a current intensity up to a nominal setpoint I.sub.set,max (FIG. 6). In FIG. 6 the load current I.sub.load is designated as I.sub.d.

(12) As shown in FIGS. 6 and 7, abnormalities in the supply voltage and therefore, in particular, the input voltage, which is designated in FIG. 7 as Input Voltage, and the current peak when the electronic circuit breaker 2 according to the invention is used, are comparatively small in relation to abnormalities in the supply voltage and the current peak when an electronic circuit breaker in accordance with the prior art is used (FIGS. 1 and 2).

(13) FIG. 4 shows a block circuit diagram of the electronic circuit breaker 2. The load current I.sub.load is recorded by a current sensor H1 connected in the current path 3 and output as an actual value I.sub.actual representing this load current I.sub.load to the control device 10, in particular to a first input (pin) 16 of a control unit μC of the control device 10. The actual value I.sub.actual is in the form of a voltage or a voltage signal. In this case, the current sensor H1 advantageously has a switching speed which is such that relatively rapid changes, for example in the event of a short circuit, are detected (resolved) by means of this recorded current. In the event of a short circuit, the actual value I.sub.actual exceeds the maximum value I.sub.short, which in particular is fed to a second input (pin) 18 of the control unit μC, so that, for example, a disconnection is triggered in the control unit μC and so that the control unit μC, implemented as a microcontroller, outputs a signal Off, for example a voltage, at its first output 20 which preferably remains output (applied) until the signal Off at the output is switched off.

(14) Alternatively, in a variant not shown in detail, the actual value I.sub.actual is fed to a first input of a second operational amplifier implemented as a comparator, and the maximum value I.sub.short is fed to the second input of the second operational amplifier. The output of the second operational amplifier is then connected to an input of the control unit μC. Thus, when the maximum value I.sub.short is exceeded by the actual value I.sub.actual a corresponding (control or voltage) signal is fed to this input of the control unit μC.

(15) The first output 20 is connected via a fourth semiconductor switch Q4 to a second semiconductor switch Q2 and in parallel to a switch S1 of an adjustment element 22. The adjustment element 22 in this case has a capacitor C2, which in a first switch position of the switch S1 is connected via a resistor R9 to a second output 24 of the control unit μC outputting the nominal setpoint value I.sub.set,max, and in a second switch position of the switch S2 via a resistor R10 to a reference potential.

(16) In addition, a voltage input V.sub.gate is connected via the resistors R7 and R3 to the control input 8 (the gate) of the first semiconductor switch Q3. By means of a voltage applied to this voltage input V.sub.gate and the electrical resistors R7 and R3, the operating point of the first semiconductor switch Q3 is adjusted.

(17) By means of a diode D1, which is connected in a current path which runs between the gate (control input 8) and the source of the first semiconductor switch Q3, the voltage between the gate and source of the first semiconductor switch Q3 is limited. By means of the resistor R12 connected in parallel to the diode D1 the gate of the first semiconductor switch Q3 is discharged when no voltage is present in the circuit.

(18) As a result of the signal Off, the second semiconductor switch Q2 is switched to the conducting state, its output 26 is coupled to the control input 8 of the first semiconductor switch Q3 so that as a result, the control input 8, implemented as a gate, of the first semiconductor switch Q3 is discharged. The load current I.sub.load is disconnected by means of the first semiconductor switch Q3. This process is realized within a relatively short period, typically 1-10 μs (FIG. 6). In addition, in particular at the same time, the signal is output to a switch S1. This switch is therefore connected in such a way that the capacitor C2 is discharged via the resistor R10.

(19) In summary, the first semiconductor switch Q3 is actuated by means of the second semiconductor switch Q2. The resistors R3, R5, R7, R11 and R12 here are used to adjust the magnitude of the voltage applied to the control input 8 of the first semiconductor switch Q3.

(20) In accordance with an alternative design of the electronic circuit breaker 2, this additionally has a current path between the voltage input V.sub.gate and the control input (the base) of the second semiconductor switch Q2. A resistor R13 is connected into this current path. This current path is illustrated in FIG. 4 by a dash-dotted line. When the signal Off is output, the fourth semiconductor switch Q4 is switched in such a way, in particular into the conducting state, that the first semiconductor switch Q3 is switched to the off state. In particular, the fourth semiconductor switch Q4 is switched to the conducting state so that the voltage applied to the control input 8 of the first semiconductor switch Q3 is correspondingly reduced.

(21) After a prescribed time period, which is preferably designed such that the capacitor C2 just completely (fully) discharges, i.e. it corresponds to a discharge time of the capacitor C2 via the resistor R10, the signal Off is switched off, so that the switch S1 is in the first switch position again and the capacitor C2 is consequently charged via the resistor R9.

(22) The adjustment element 22 is connected to a first input 28 of an operational amplifier OP1 and outputs a setpoint value I.sub.set, which is represented by means of the voltage applied to the capacitor C2, to this first input 28. The actual value I.sub.actual is fed to a, in particular inverting, second input 30 of the operational amplifier.

(23) By means of the operational amplifier OP1 a difference between actual value I.sub.actual and setpoint value I.sub.set is thus formed. This difference is output from the operational amplifier OP1 as control signal D. By means of a third semiconductor switch Q1 and the resistors R4 and R8 an amplifier is formed for the (voltage) signal D output by the operational amplifier OP1. The amplitude (the magnitude) of the signal D is thereby modified or adjusted (amplified) to an amplitude suitable for operating the second semiconductor switch Q2 and thus for actuating the first semiconductor switch Q3.

(24) As the capacitor C2 is charged via an electrical resistor R10 the setpoint value I.sub.set fed to the first input 28 changes according to the state of charge of the capacitor C2. This causes a corresponding, in particular gradual, change in the signal D. The second semiconductor switch Q2 is thus actuated in such a way, in particular to a gradually less conductive (non-conducting) state, that the first semiconductor switch Q3 is gradually (continuously) switched to the conducting state. In this way, the load current I.sub.load gradually increases until the actual value I.sub.actual fed to the first input 16 of the control unit pC corresponds to the nominal setpoint value I.sub.set,max. As shown in FIG. 8, this allows the period of time in which load current I.sub.load increases to be determined (specified) by means of a suitable choice of the resistance value (size of the resistance) of the electrical resistor R9 and the capacitance of the capacitor C2, in other words by an appropriate design of the adjustment element 22. In this figure the load current is designated by I.sub.d.

(25) In addition, a capacitor C1 is connected in a current path between the second input 30 of the operational amplifier OP1 and its output. The capacitor C1 has a capacitance which is suitable for preventing an oscillation of the output signal of the operational amplifier OP1 and hence in the current path 3.

(26) In accordance with FIG. 4, the shut-off circuit 12 contains in summary an electrical resistor R1 and the electrical resistor R10, the fourth semiconductor switch Q4, the switch S1, the control unit μC and, if applicable, the second operational amplifier. In particular, by forming a constant current source with a voltage applied to the current path 3 by means of the electrical resistors R2 to R5 and the electrical resistors R7 to R9, R11 and R12, by means of the capacitors C1 and C2, by means of the operational amplifier OP1, by means of the semiconductor switches Q1, Q2 and Q3, by means of the diode D1, and by means of the current sensor H1, the load current I.sub.load is advantageously regulated, in particular held constant.

(27) In addition, the output signal of the operational amplifier OP1 in the form of control signal D, which is implemented in particular as an output voltage, is fed to a third input 32 of the control unit pC so that by means of this signal the control unit μC determines whether a current limitation of the load current I.sub.load by means of the first semiconductor switch Q3 is still taking place. To prevent thermal damage, in particular of the first semiconductor switch Q3, the first semiconductor switch Q3 is switched to the non-conducting state (switched off) if the current limiting has persisted for a specified duration since the beginning of the current-limiting actuation, in particular without interruption.

(28) In addition a voltage V.sub.load applied to the load (Load) is fed to a fourth input 34 of the control unit μC.

(29) The processing sequence described above of the method for operating the electronic circuit breaker 2 is summarized in the flowchart of FIG. 5. It is also apparent that the first semiconductor switch Q3 is also actuated in the current-limiting state when the nominal setpoint value I.sub.set,max is exceeded by the actual value I.sub.actual, but the maximum value I.sub.short is not exceeded.

(30) In summary, the electronic circuit breaker 2 has a first semiconductor switch Q3, preferably an N-channel MOS transistor, which is connected in a current path 3 between a voltage input 4 and a load output 6. In addition, the electronic circuit breaker 2 has a control device 10 connected to the control input 8 of the first semiconductor switch Q3, wherein the first semiconductor switch Q3 is activated as a function of an actual value I.sub.actual of the load current I.sub.load which is fed to the control device 10. According to one advantageous refinement, the control device 10 has a control unit μC.

(31) In an advantageous design, the electronic circuit breaker also has a current sensor H1, which is preferably connected in the current path 3.

(32) In an advantageous design, the control device 10 has a device and/or a circuit 14 for current limiting, and a device and/or a circuit 12 for switching off or blocking the current of the first semiconductor switch Q3.

(33) In a further advantageous design the first semiconductor switch Q3 is actuated as a function of an actual value I.sub.actual of the load current I.sub.load which is fed to the control device 10, the current-limiting device or circuit 14 and/or the shut-off device or circuit 12.

(34) In accordance with a suitable design of the electronic circuit breaker, in the event of a short circuit and/or if a maximum value I.sub.short is exceeded by the actual value I.sub.actual, the control device 10 or the control unit μC outputs a signal Off, in particular a shut-off signal, to the current-limiting device or circuit 14 and/or preferably to the shut-off device or circuit 12, to disable and/or switch off the first semiconductor switch Q3.

(35) In a further advantageous design of the electronic circuit breaker the actual value I.sub.actual is fed to the input side of the control device 10 or the current-limiting device or circuit 14 and/or a nominal setpoint value I.sub.set,max is fed to the input side of the current-limiting device or circuit 14, in particular by the control unit μC.

(36) In a further advantageous design, as a function of the actual value I.sub.actual and/or the nominal setpoint value I.sub.set,max the first semiconductor switch Q3 is or will be actuated in a current-limiting state.

(37) In accordance with a suitable refinement, the control device 10 and/or the current-limiting device or circuit 14 has an adjustment element 22. The nominal setpoint value I.sub.set,max is fed in a suitable manner to the input side of the adjustment element 22 and it outputs a setpoint value I.sub.set at the output.

(38) In a suitable design, the control device 10 or the adjustment element 22 has a capacitor C2. The capacitor C2 is advantageously coupled by means of a switch S1 to the control device 10, in particular to the control unit pC, or is discharged by means of the switch S1.

(39) In another advantageous configuration, the control device 10 or the current-limiting 14 device or circuit 14 has an operational amplifier OP1. Advantageously the adjustment element 22 is connected to a first input 28 of the operational amplifier OP1 to feed in the setpoint value I.sub.set, and the actual value I.sub.actual is fed to a second input of the operational amplifier OP1. By means of the operational amplifier OP1 a control signal D, in particular, a difference between the setpoint value I.sub.set and the actual value I.sub.actual, is advantageously formed to actuate the first semiconductor switch Q3. In addition, in a suitable manner a load voltage V.sub.load is fed to the control device 10 or the control unit μC.

(40) In an advantageous design, the control device 10, the current-limiting device or circuit 14 and/or the shut-off device or circuit 12 has a second semiconductor switch Q2, preferably a pnp bipolar transistor. In an advantageous design the second semiconductor switch Q2 is connected to the control input 8 of the first semiconductor switch Q3. In a further suitable design the output 26 of the second semiconductor switch Q2 preferably forms an output of the current-limiting device or circuit 14 and/or of the shut-off device or circuit 12.

(41) In an appropriate design the drain of the first semiconductor switch Q3 is preferably connected to the voltage input 4, the source is preferably connected to the load output 6 and the gate to the control device 10.

(42) In the method for operating the electronic circuit breaker 2, in one of the above-mentioned variants having a first semiconductor switch Q3 connected between a voltage input 4 and a load output 6, in accordance with the method an actual value I.sub.actual of the load current I.sub.load or said current is recorded as an actual value I.sub.actual, in the event of a short circuit when a maximum value I.sub.short is exceeded by the actual value I.sub.actual the first semiconductor switch Q3 is switched to the non-conducting state, and/or in the event of an overload, on a setpoint I.sub.set being exceeded by the actual value I.sub.actual the first semiconductor switch Q3 is switched to a current-limiting state.

(43) In an advantageous variant of the method, in the event of a short circuit the setpoint value I.sub.set of the load current I.sub.load is set to a minimum value I.sub.min and then increased continuously to a nominal setpoint value (I.sub.set,max). Advantageously, a difference (difference value) is formed from the actual value I.sub.actual and the setpoint I.sub.set. Advantageously the difference (difference value) is used as a control signal D for the current-limiting actuation of the first semiconductor switch Q3. The actuated first semiconductor switch Q3 actuated in the current-limiting state is appropriately switched into a non-conducting state and/or controlled after expiry of a specified period and/or a specified timer element.

(44) The invention is not limited to the exemplary embodiment described above. Instead, other variants of the invention can also be derived from them by the person skilled in the art, without departing from the subject-matter of the invention. In particular, all individual features described in connection with the exemplary embodiments can also be combined together in different ways without departing from the subject matter of the invention.

LIST OF REFERENCE SIGNS

(45) 2 electronic circuit breaker 3 current path 4 voltage input 6 load output 8 control input 10 control device 12 shut-off device 14 current limiting device 16 first input to the control unit 18 second input to the control unit 20 first output of the control unit 22 adjustment element 24 second output of the control unit 26 output of the second semiconductor switch 28 first input of the operational amplifier 30 second input of the operational amplifier 32 third input to the control unit 34 fourth input to the control unit C1 capacitor C2 capacitor D control signal/difference D1 diode H1 current sensor I.sub.actual actual value I.sub.load load current I.sub.min minimum value I.sub.set setpoint value I.sub.set,max nominal setpoint value I.sub.short maximum value μC control unit Off shut-off signal OP1 operational amplifier Q1 third semiconductor switch Q2 second semiconductor switch Q3 first semiconductor switch Q4 fourth semiconductor switch R1 to R13 electrical resistors V.sub.load load voltage V.sub.gate voltage input