DEVICE FOR MEASURING A CURRENT THROUGH A CHOKE AND METHOD FOR OPERATING A DEVICE FOR MEASURING A CURRENT THROUGH A CHOKE

Description

[0001] The invention relates to a device for measuring a current through a choke and a method for operating a device for measuring a current through a choke. Furthermore, the invention relates to a drive train comprising a device, a vehicle comprising a drive train, a computer program, and a machine-readable storage medium. State of the art

[0002] The publications TSANG KM ET AL: "Temperature compensated high efficiency inductor current sensor", SENSORS AND ACTUATORS A: PHYSICAL, ELSEVIER BV, NL, Vol. 154, No. 1, 31 August 2009 (2009-08-31), pages 16-22, XP026498367, ISSN: 0924-4247, CN 104 638 885 B, US 2018 / 340964 A1, KR 2011 0012116 A, LEVIGION M: "Temperature compensation of electrical quantities", TECHNISCHES MESSEN ATM, R.OLDENBOURG VERLAG. MUNICH, DE, Vol. 2119-8, No. 452, September 1, 1973 (1973-09-01), pages 177-180, XP002163913 and JP 2010 011294 A disclose current measurement methods. Current measurement methods are known in which a current in a power electronic system, for example, in a DC-DC converter, can be measured via the voltage drop of, for example, a smoothing choke. No separate shunt resistor is required for this. Such methods are known as "DCR current sensing," where the abbreviation "DCR" stands for "DC resistance" of the choke.Here, the current through the choke is measured indirectly by recording the voltage drop across the choke and continuously integrating it. The measured current is obtained by integrating the voltage. For this purpose, an integrator circuit is used that is tuned to the electrical properties of the choke, for example by means of an RC low-pass filter, e.g. a series connection of a resistor and capacitor in parallel with the choke. For very rapid current changes, the inductive component of the voltage drop across the choke dominates over the voltage drop across the copper resistance of the choke. For direct currents, however, there is no longer any voltage drop across the inductance, so the current can be measured directly across the ohmic copper resistance of the choke. The integrator circuit is dimensioned so that its time constant or cut-off frequency is almost identical to the time constant or cut-off frequency of the choke.The time constant of the integrator circuit corresponds to the product of the ohmic resistance and capacitance of the integrator circuit (R*C). The time constant of the choke corresponds to the quotient of the inductance of the choke divided by the ohmic resistance of the choke (L / Rdc). For identical time constants, the product of the ohmic resistance and capacitance of the integrator circuit corresponds to the quotient of the inductance of the choke divided by the ohmic resistance of the choke (R*C = L / Rdc). This ensures that the overall transfer function is constant across the entire frequency range. The transfer function of the choke is: Rdc + s*L, or that of the RC filter of the integrator circuit: 1 / (1 + s*R*C), with s = jω. Multiplying both functions gives the overall transfer function: .

[0003] If both time constants are equal, then the frequency-dependent part is always 1 and thus: G(s) = Rdc.

[0004] Advantages of this measuring principle over other current sensors, such as a shunt resistor, include lower unit costs, smaller space requirements, and loss-free current measurement. However, measurement accuracy is limited because the copper resistance of the choke has high tolerances due to production requirements and is highly temperature-dependent. Temperature compensation can be achieved using an NTC resistor connected in parallel with the capacitor of the integrator circuit. The temperature-dependent gain of the sensor circuit is varied so that it counteracts the temperature coefficient of the copper resistance of the choke, thus virtually compensating for the temperature influence.

[0005] However, the presented circuit concept does not allow current measurement if it not only fluctuates but also changes direction and flows bidirectionally. The resulting negative voltage measurement signals cannot be processed without additional circuitry. In such cases, it is known to shift the zero point using an injected bias offset voltage in order to expand the measurement range for negative currents and thus consistently output positive voltage measurement signals. However, temperature compensation using an NTC resistor changes the offset voltage depending on the temperature, which means that the current value can no longer be accurately derived from the voltage measurement signal.

[0006] Therefore, there is a need for alternative measuring circuits. Disclosure of the invention

[0007] A device is provided for measuring a current through a choke of a voltage converter comprising an integrator circuit, an amplifier circuit, and an NTC resistor. A load current flows through the choke of the voltage converter. The choke is connected on the output side to an output terminal of the voltage converter. The integrator circuit is arranged in parallel with the choke. The integrator circuit comprises a series circuit of an integrator resistor and an integrator capacitor. The integrator capacitor is also connected to the output terminal of the voltage converter. A center tap between the integrator resistor and the integrator capacitor serves as the output of the integrator circuit. An integrator output signal is present at this output of the integrator circuit. The amplifier circuit comprises an inverting and a non-inverting amplifier input terminal and an amplifier output terminal.An amplifier input signal dependent on the integrator output signal is applied to the non-inverting amplifier input terminal. A voltage signal characterizing the current through the choke is applied to the amplifier output terminal of the amplifier circuit. The NTC resistor is arranged in the feedback path of the amplifier circuit between the inverting amplifier input terminal and the amplifier output terminal.

[0008] A device is provided for measuring a, preferably bidirectional, current through a choke, which is preferably designed as a smoothing choke on the secondary side at the output of a voltage converter. The device comprises an integrator circuit and a, preferably active, amplifier circuit. An integrator output signal is present at the output of the integrator circuit. An amplifier input signal is supplied to the non-inverting amplifier input terminal as a function of the integrator output signal; for this purpose, the output of the integrator circuit is preferably electrically connected, preferably directly connected, to the non-inverting amplifier input terminal. The NTC resistor is arranged in the feedback path of the amplifier circuit between the inverting amplifier input terminal and the amplifier output terminal.

[0009] Advantageously, a device is provided in which the NTC resistor is arranged independently of any potential offset voltage, enabling an unbiased measurement of bidirectional currents. Since the NTC resistor is decoupled from potential zero-point offset generation, interference caused by the NTC resistor is avoided. An extension of the measurement circuit for a DCR current measurement for bidirectional currents is provided without the use of a bipolar supply voltage, while maintaining temperature compensation by means of the NTC resistor and active amplifier circuit.

[0010] In another embodiment of the invention, the amplifier circuit comprises an operational amplifier.

[0011] The amplifier circuit comprises an operational amplifier, which preferably operates as a non-inverting operational amplifier. Advantageously, a possibility is created to provide an efficient amplifier circuit that enables economical implementation of the device. Preferably, an additional active amplifier circuit comprising an operational amplifier is used, wherein the amplifier stage is also used to amplify the desired signal, in particular the integrator output signal, in order to achieve improved resolution of the desired signal. The amplification of the desired signal is preferably applied when the copper resistance of the choke coil is very small compared to the measured current.

[0012] The device according to the invention comprises a reference voltage source with a positive source terminal and a negative source terminal. A first offset voltage is coupled to the output of the integrator circuit by means of the reference voltage source. For this purpose, the negative source terminal is connected to the output terminal of the voltage converter, and the positive source terminal is connected to the output of the integrator circuit via a coupling resistor.

[0013] A reference voltage source couples a first offset voltage to the output of the integrator circuit. Consequently, the potential of the integrator output signal is raised. This allows the circuit to be used for currents flowing in the opposite direction. Advantageously, a device is provided with which bidirectional currents can be determined.

[0014] Preferably, the zero point offset, the first offset voltage, is generated at the output of the integrator circuit by means of the reference voltage source, which is coupled into the signal path, the integrator output signal, via the coupling resistor.

[0015] In another embodiment of the invention, a second offset voltage is coupled into the feedback path at the inverting amplifier input terminal of the amplifier circuit by means of the reference voltage source. Preferably, the negative source terminal is connected to the output terminal of the voltage converter, and the positive source terminal is connected to the output terminal of the voltage converter via a voltage divider having a first, second, and third voltage divider resistor. Furthermore, a tap between the second and third voltage divider resistors is preferably connected to the inverting amplifier input terminal.

[0016] Using the reference voltage source, a second offset voltage is coupled to the inverting amplifier input terminal of the amplifier circuit. This advantageously results in the possibility, preferably by dimensioning the voltage divider resistors, of setting the second offset voltage at the inverting input of the operational amplifier to be identical to the voltage at the non-inverting input, even when no current flows through the choke. Preferably, the second offset voltage remains the same even with increasing currents through the choke.

[0017] The amplifier circuit or operational amplifier preferably operates as a non-inverting amplifier. If the NTC resistor changes as a function of temperature, the linear gain of the circuit also changes, since the NTC resistor changes the divider factor in the feedback path. To ensure that a third offset voltage at the output of the amplifier circuit remains constant regardless of temperature, the reference voltage source is also fed into the feedback path of the amplifier circuit. The preferably three voltage divider resistors form a voltage divider. By appropriately dimensioning the resistors, the second offset voltage at the inverting input of the amplifier circuit is set to be almost identical to the voltage at the non-inverting input. If the current to be measured through the choke increases from 0 A to higher values, only the voltage increase due to the current change is amplified.Preferably, the first, second and third offset voltages remain the same when no current flows through the choke.

[0018] In another embodiment of the invention, a serial resistor is arranged in series with the NTC resistor and a parallel resistor is arranged in parallel with the series circuit of serial resistor and NTC resistor in the feedback path of the amplifier circuit between the inverting amplifier input terminal and the amplifier output terminal.

[0019] A resistor is connected in series with the NTC resistor, and a resistor is connected in parallel with the series circuit of the resistor and the NTC resistor. These three resistors are arranged in the feedback path of the amplifier circuit between the inverting amplifier input terminal and the amplifier output terminal. A circuit arrangement for linearizing the NTC resistor over temperature is advantageous. Without this circuit arrangement, the resistor behaves nonlinearly over temperature.

[0020] Preferably, a series resistor is connected to the NTC resistor, and a parallel resistor is connected to the series connection of the series resistor and the NTC resistor to linearize the NTC resistor over temperature, since the NTC resistor behaves nonlinearly over temperature. The series resistor serves to prevent the total impedance of the NTC resistor, the series resistor, and the parallel resistor from becoming too low at high temperatures. The parallel resistor, on the other hand, serves to prevent the total impedance of the NTC resistor, the series resistor, and the parallel resistor from becoming too high at low temperatures.

[0021] In another embodiment of the invention, a first filter capacitor is arranged in parallel to the NTC resistor.

[0022] Advantageously, a circuit arrangement is provided that adjusts the gain in a frequency-selective manner. The first filter capacitor, connected in parallel with the NTC resistor, shorts the NTC resistor at higher frequencies, so that it no longer functions above a specific or determinable cutoff frequency.

[0023] In another embodiment of the invention, a second filter capacitor is arranged in parallel with the first voltage divider resistor or the second voltage divider resistor.

[0024] Advantageously, a circuit arrangement is provided that adjusts the gain in a frequency-selective manner. The second filter capacitor, connected in parallel with the first or second voltage divider resistor, short-circuits the first or second voltage divider resistor at higher frequencies, so that above a specific or determinable cutoff frequency, the first or second voltage divider resistor no longer functions, and only one of the two voltage divider resistors is active. Thus, the NTC resistor preferably acts in a frequency-selective manner only at low frequencies below a specific or determinable cutoff frequency, preferably the cutoff frequency of the choke, which results from the quotient of its inductance and the copper resistance.

[0025] Preferably, an amplifier circuit is provided which enables the measuring range for bidirectional currents and at the same time the temperature compensation by means of an NTC resistor, wherein the NTC resistor is not connected to the output of the integrator circuit, but is arranged in the feedback path of the amplifier circuit.

[0026] Furthermore, the time constants of the choke and the integrator circuit are preferably kept as constant as possible over the temperature in order to keep the amplification factor of the device for measuring the current through a choke, i.e. the sensor circuit, constant over the frequency range. If this were not the case, the device for measuring the current through a choke could generate a measurement error in the event of rapid current changes or, conversely, measure the current too slowly in the case of short-circuit monitoring. Since the NTC resistor in this circuit is no longer connected to the output of the integrator circuit, the amplification factor is frequency-selectively adjusted using the first and second filter capacitors so that it remains constant both over the temperature and over the frequency range. The first filter capacitor short-circuits the NTC resistor at higher frequencies, so that it is no longer effective above a certain cut-off frequency.no longer contributes to the overall gain. The second filter capacitor eliminates the effect of the first voltage divider resistor for higher frequencies, so that only the second voltage divider resistor contributes to the overall gain. This allows the amplifier to be set so that the NTC resistor acts frequency-selectively only in a specific frequency range, preferably toward low frequencies, preferably only at low frequencies below a specific or determinable cutoff frequency, preferably the cutoff frequency of the choke, which results from the quotient of its inductance and copper resistance.

[0027] Preferably, the zero-point offset generation is decoupled from the NTC resistor, thus enabling bidirectional current measurement. The first, second, and third offset voltages are not affected by temperature, and a constant overall transfer function is maintained across frequency.

[0028] The invention further relates to a voltage converter with a described device. The voltage converter is designed as an inverter, a DC-DC converter, or a charger.

[0029] Advantageously, a special voltage transformer is provided with a device for measuring a current through a choke.

[0030] The invention further relates to a drive train of a vehicle with a voltage converter. Such a drive train with a voltage converter and a described device serves, for example, to drive an electric vehicle. The device provides an efficient means of measuring a current through a choke.

[0031] The invention further relates to a vehicle having a described drive train. Advantageously, a vehicle is thus provided that includes a device for efficiently measuring a current through a choke.

[0032] Furthermore, the invention relates to a method for operating a device comprising the steps of: determining the current through a choke of a voltage converter and controlling the voltage converter as a function of the determined current.

[0033] Advantageously, a method for efficient measurement of a current through a choke is provided.

[0034] Furthermore, the invention relates to a computer program which comprises instructions which, when executed by a computer, cause the computer to carry out the steps of the method described so far.

[0035] Furthermore, the invention relates to a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method described so far.

[0036] It is understood that the features, properties and advantages of the device apply or are applicable accordingly to the method or the drive train and the vehicle and vice versa.

[0037] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings. Short description of the drawing

[0038] In the following, the invention will be explained in more detail with reference to some figures, which show: Figure 1 a schematic representation of a voltage converter with a choke. Figure 2a schematic representation of a device for measuring a current through a choke of a voltage transformer. Figure 3 a schematic diagram showing the uncompensated course of the total transfer function over frequency at different temperatures. Figure 4 a schematic diagram showing the compensated course of the total transfer function over frequency at different temperatures. Figure 5 a schematic diagram showing the uncompensated course of the total transfer function over frequency at different temperatures without filter capacitors. Figure 6 a schematic diagram showing the partially compensated course of the total transfer function over the frequency at different temperatures with the first filter capacitor. Figure 7a schematic diagram showing the compensated course of the total transfer function over frequency at different temperatures with the first and second filter capacitor. Figure 8 a schematically illustrated method for operating the device. Figure 9 a schematic representation of a vehicle with a powertrain and a voltage converter. Embodiments of the invention

[0039] The Figure 1 shows a schematic representation of a voltage converter 100 with a choke 130. The voltage converter 100 is preferably designed as an inverter, a DC-DC converter or a charger. Figure 1It is illustrated by way of example as a DC-DC converter. This comprises a primary circuit 110 and a secondary circuit 120, which are galvanically isolated from each other by means of a transformer. The secondary circuit 120 comprises a choke 130 at the output, preferably a smoothing choke, which is connected on the output side of the voltage converter 100 to the output terminal 105 of the voltage converter 100. A current, or the load current, of the voltage converter 100 flows through this choke 130 during operation of the voltage converter 100 when electrical energy is transported from the primary circuit 110 to the secondary circuit 120 or vice versa. Furthermore, the Figure 1a device 200 for measuring a current through the choke 130 of the voltage converter 100. The device comprises an integrator circuit 140 connected in parallel to the choke 130. Furthermore, the device 200 comprises an amplifier circuit. The integrator output signal of the integrator circuit 140 is further processed by an amplifier circuit, or by the illustrated operational amplifier 150. A voltage signal characterizing the current through the choke 130 is present at the amplifier output terminal 156 of the amplifier circuit.

[0040] Figure 2 shows a device 200 for measuring a current through a choke 130 of a voltage converter 100. The Figure 1shows the output terminal 105 of the voltage converter 100 and the choke 130 connected to it, which are represented in the sense of an equivalent circuit diagram as an ohmic DC choke resistor 132 and as the inductance 134 of the choke 130. The device comprises the integrator circuit 140 connected in parallel to the choke 130. The device 200 further comprises an amplifier circuit and an NTC resistor 160. A load current of the voltage converter 100 flows through the choke 130. The integrator circuit 140 comprises a series circuit of an integrator resistor 142 and an integrator capacitor 144. The integrator capacitor 144 is also connected to the output terminal 105 of the voltage converter 100. A center tap is formed between the integrator resistor 142 and the integrator capacitor 144 as the output of the integrator circuit 140. An integrator output signal is present at this output of the integrator circuit 140.The amplifier circuit comprises an inverting and a non-inverting amplifier input terminal 152, 154 and an amplifier output terminal 156. An amplifier input signal dependent on the integrator output signal is supplied to the non-inverting amplifier input terminal 154. A voltage signal characterizing the current through the choke 130 is present at the amplifier output terminal 156 of the amplifier circuit. The NTC resistor 160 is arranged in the feedback path of the amplifier circuit between the inverting amplifier input terminal 152 and the amplifier output terminal 156. The amplifier circuit preferably comprises an operational amplifier 150, which preferably operates as a non-inverting operational amplifier. The device 200 comprises a reference voltage source 170 with a positive source terminal 172 and a negative source terminal 174.By means of the reference voltage source 170, a first offset voltage is coupled to the output of the integrator circuit 140. The negative source terminal 174 is connected to the output terminal 105 of the voltage converter 100. The positive source terminal 172 is connected to the output of the integrator circuit 140 via a coupling resistor 176. Preferably, a second offset voltage is further coupled into the feedback path at the inverting amplifier input terminal 152 of the amplifier circuit by means of the reference voltage source 170. Preferably, the positive source terminal 172 is connected to the output terminal 105 of the voltage converter 100 via a voltage divider comprising a first, second, and third voltage divider resistors 177, 178, 179. Preferably, a tap between the second and third voltage divider resistors 178, 179 is connected to the inverting amplifier input terminal 152.Preferably, in the feedback path of the amplifier circuit between the inverting amplifier input terminal 152 and the amplifier output terminal 156, a series resistor 162 is arranged in series with the NTC resistor 160, and a parallel resistor 164 is arranged in parallel with the series circuit of the series resistor 162 and the NTC resistor 160. Further preferably, a first filter capacitor 166 is arranged in parallel with the NTC resistor 160 and / or a second filter capacitor 168 is arranged in parallel with the first voltage divider resistor 177.

[0041] A possible supply concept for the device is as follows: According to Figure 2, the reference potential of the amplifier circuit or operational amplifier 150 is equal to the voltage after the choke at output terminal 105, preferably at the output of a switched-mode power supply or a DC-DC converter. Preferably, a supply voltage greater than the voltage at output terminal 105 is required to power the amplifier circuit. Preferably, a charge pump or the generation of a so-called high-side auxiliary voltage would be used. The voltage signal at amplifier output terminal 156 is preferably transferred to ground potential by means of another circuit, for example, a high-side measuring amplifier or a current mirror.

[0042] Alternatively, the integrator output signal is preferably transferred to the ground reference potential of the voltage converter via a differential amplifier or a bidirectional high-side current sense amplifier, for further processing, preferably by feeding it to the non-inverting amplifier input terminal 154 as an amplifier input signal depending on the integrator output signal. The reference potential for the reference voltage source and the amplifier circuit is the ground reference potential of the voltage converter.

[0043] The Figure 3 shows a schematic diagram showing the uncompensated course of the total transfer function in mV (per A) versus frequency at different temperatures (T1, T2, T3, T4). For low frequencies, a wide spread of the total transfer function can be observed at different temperatures (T1, T2, T3, T4).

[0044] The Figure 4shows a schematic diagram showing the compensated course of the total transfer function in mV (per A) over frequency at different temperatures (T1, T2, T3, T4) by means of the series resistor 162 in series with the NTC resistor 160 and the parallel resistor 164 in parallel with the series connection of the series resistor 162 and the NTC resistor 160 in the feedback path. In comparison to the Figure 3 the fan-out of the overall transfer function for low frequencies at different temperatures is significantly reduced.

[0045] The Figure 5 shows a schematic diagram illustrating the uncompensated course of the overall transfer function in mV (per A) versus frequency at various temperatures (T1, T2, T3, T4) without filter capacitors. A wide fanning out or spreading of the overall transfer function can be observed over a wide frequency range at different temperatures (T1, T2, T3, T4).

[0046] The Figure 6 shows a schematic diagram showing the course of the total transfer function in mV (per A) over frequency at different temperatures (T1, T2, T3, T4) partially compensated by the first filter capacitor. In comparison to the Figure 5 The dispersion of the overall transfer function is significantly reduced over a wide frequency range at different temperatures (T1, T2, T3, T4). The first filter capacitor eliminates the effect of the NTC resistor above a certain frequency.

[0047] The Figure 7 shows a schematic diagram showing the overall transfer function in mV (per A) versus frequency at different temperatures (T1, T2, T3, T4) compensated by the first and second filter capacitors. In comparison to the Figure 6A plateau elevation of the overall transfer function can be observed over a wide frequency range at different temperatures (T1, T2, T3, T4). The gain at higher frequencies can be specified by dimensioning the second filter capacitor.

[0048] The Figure 8 shows a schematically illustrated method 400 for operating device 200. Method 400 begins with step 410. In step 420, the current through a choke 130 of a voltage converter 100 is determined. In step 430, the voltage converter 100 is controlled depending on the determined current. The method ends with step 440.

[0049] The Figure 9 shows a schematically illustrated vehicle 290 with a drive train 300 and a voltage converter 100. The voltage converter comprises the device 200, as Figure 2described. Preferably, the electric drive train comprises a battery (not shown) for supplying the drive train, which further preferably comprises an inverter 192 and / or an electric machine 194.

Claims

1. Device (200) for measuring a current through a choke (130) of a voltage converter (100), having an integrator circuit (140), an amplifier circuit and an NTC resistor (160), wherein a load current of the voltage converter (100) flows through the choke (130) and the output side of the choke (130) is connected to an output terminal (105) of the voltage converter (100), wherein the integrator circuit (140) is arranged in parallel with the choke (130) and comprises a series circuit comprising an integrator resistor (142) and an integrator capacitor (144), wherein the integrator capacitor (144) is also connected to the output terminal (105) of the voltage converter (100) and a centre tap between the integrator resistor (142) and the integrator capacitor (144) is designed as the output of the integrator circuit (140) and an integrator output signal is present at this output of the integrator circuit (140), wherein the amplifier circuit comprises an inverting and a non-inverting amplifier input terminal (152, 154) and an amplifier output terminal (156) and a voltage signal characterizing the current through the choke (130) is present at the amplifier output terminal (156) of the amplifier circuit, wherein the NTC resistor (160) is arranged in the feedback path of the amplifier circuit between the inverting amplifier input terminal (152) and the amplifier output terminal (156), characterized in that the non-inverting amplifier input terminal is supplied with an amplifier input signal as a function of the integrator output signal, and the device comprises a reference voltage source (170) having a positive source terminal (172) and a negative source terminal (174), wherein the reference voltage source (170) is used to couple in a first offset voltage at the output of the integrator circuit (140), wherein the negative source terminal (174) is connected to the output terminal (105) of the voltage converter (100), and the positive source terminal (172) is connected to the output of the integrator circuit (140) via a coupling resistor (176).

2. Device (200) according to Claim 1, wherein the amplifier circuit comprises an operational amplifier (150) which preferably operates as a non-inverting operational amplifier.

3. Device (200) according to Claim 2, wherein the reference voltage source (170) is used to couple a second offset voltage into the feedback path at the inverting amplifier input terminal (152) of the amplifier circuit, wherein preferably the negative source terminal (174) is connected to the output terminal (105) of the voltage converter (100), and the positive source terminal (172) is connected to the output terminal (105) of the voltage converter (100) via a voltage divider consisting of a first, second and third voltage divider resistor (177, 178, 179) and a tap between the second and third voltage divider resistors (178, 179) is connected to the inverting amplifier input terminal (152).

4. Device (200) according to one of the preceding claims, wherein in the feedback path of the amplifier circuit between the inverting amplifier input terminal (152) and the amplifier output terminal (156), a series resistor (162) is arranged in series with the NTC resistor (160) and a parallel resistor (164) is arranged in parallel with the series circuit comprising series resistor (162) and NTC resistor (160).

5. Device (200) according to one of the preceding claims, wherein a first filter capacitor (166) is arranged in parallel with the NTC resistor (160).

6. Device (200) according to Claim 3, or according to Claim 4 if dependent on Claim 3, or according to Claim 5 if dependent on Claim 3, wherein a second filter capacitor (168) is arranged in parallel with the first voltage divider resistor (177) or the second voltage divider resistor (178).

7. Voltage converter (100) having a device (200) according to one of Claims 1 to 6, wherein the voltage converter is in the form of an inverter, a DC-DC voltage converter or a charger.

8. Drive train (300) of a vehicle (290) having a voltage converter (100) according to Claim 7.

9. Vehicle (290) having a drive train (300) according to Claim 8.

10. Method (400) for operating a device (200) according to one of Claims 1-9, having the steps of: ascertaining (420) the current through a choke (130) of a voltage converter (100) controlling (430) the voltage converter (100) on the basis of the ascertained current.

11. Computer program comprising commands which, when the program is executed by a computer, cause the latter to perform the method / the steps of the method (400) according to Claim 10.

12. Computer-readable storage medium comprising commands which, when executed by a computer, cause the latter to perform the method / the steps of the method (400) according to Claim 10.