Device for measuring the current through a choke and method for operating a device for measuring the current through a choke

Abstract

A device (200) for measuring a current through a choke (130) of a voltage converter (100), the device comprising an integrating circuit (140), an amplifier circuit and an NTC resistor (160). The amplifier circuit comprises inverting and non-inverting amplifier input connection terminals (152, 154) and an amplifier output connection terminal (156). An amplifier input signal dependent on an integrator output signal is supplied to the non-inverting amplifier input connection terminal (154). A voltage signal representing the current through the choke (130) is supplied to the amplifier output connection terminal (156) of the amplifier circuit. The NTC resistor (160) is arranged in a feedback path of the amplifier circuit between the inverting amplifier input connection terminal (152) and the amplifier output connection terminal (156).

Description

Technical Field

[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. The invention also relates to a drive train having the device, a vehicle having the drive train, and a computer program and a machine-readable storage medium. Background Art

[0002] Current measurement methods are well known, in which the current in a power electronic system, for example in a DC voltage converter, can be measured by, for example, a voltage drop across a smoothing choke. A separate shunt resistor is not required for this. This method is known as "DCR Current Sensing", where the abbreviation "DCR" stands for the "DC resistance" of the choke. In this case, the current passing through the choke is measured indirectly, in that the voltage drop at the choke is detected and continuously integrated. The measured current is obtained by integrating the voltage. For this purpose, an integrating circuit is used, which is matched to the electrical characteristics of the choke, for example, by means of an RC low pass, for example, a series circuit consisting of a resistor and a capacitor connected in parallel with the choke. In the case of very fast current changes, the inductive component of the voltage drop of the choke is dominant relative to the voltage drop at the copper resistance of the choke. For direct current, there is no longer a voltage drop on the inductor, so that the current can be measured directly through the ohmic copper resistance of the choke. The parameters of the integrating circuit are determined so that the time constant of the integrating circuit or the angular frequency of the integrating circuit is almost identical to the time constant or the angular frequency of the choke. The time constant of the integrating circuit corresponds to the product of the ohmic resistance and the capacitance of the integrating 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). Therefore, for the same time constant, the product of the ohmic resistance and the capacitance of the integrating 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 total transfer function is constant over the entire frequency range. The transfer function of the choke is: Rdc + s*L, or the transfer function of the RC filter of the integrating circuit is: 1 / (1 + s*R*C), where s = jω. If the two functions are multiplied, the total transfer function is obtained:

[0003]

[0004] If both time constants are identical, the frequency-dependent component is always 1 and therefore applies: G(s) = Rdc.

[0005] The advantages of this measuring principle over other current sensors, such as shunt resistors, are lower unit costs, less space requirements and loss-free current measurement. However, the measuring accuracy is limited because the copper resistance of the choke has high tolerances due to manufacturing and is highly temperature-dependent. Temperature compensation can be performed with the aid of an NTC resistor connected in parallel with the capacitor of the integration circuit. The temperature-dependent gain factor of the sensor circuit is changed so that it cancels out the temperature coefficient of the copper resistance of the choke and thus nearly compensates for temperature influences.

[0006] However, the proposed circuit design cannot measure currents when the current not only fluctuates, but also changes direction and flows in both directions. The resulting negative voltage measurement signal cannot be processed without further circuit technology expenditure. It is known that in this case, the zero point is moved by means of an injected bias offset voltage in order to thereby expand the measurement range of negative currents and thus always output a positive voltage measurement signal. However, temperature compensation by means of an NTC resistor changes the offset voltage in a temperature-dependent manner, so that the current value can no longer be accurately derived from the voltage measurement signal.

[0007] Therefore, an alternative measurement circuit is needed. Summary of the invention

[0008] A device for measuring the current through the choke of a voltage converter is provided, the device having an integration circuit, an amplifier circuit and an NTC resistor. The load current flows through the choke of the voltage converter. The choke is connected to the output connection of the voltage converter on the output side. The integration circuit is arranged in parallel with the choke. The integration circuit includes a series circuit consisting of an integration resistor and an integration capacitor. The integration capacitor is also connected to the output connection of the voltage converter. The middle tap between the integration resistor and the integration capacitor is designed as the output of the integration circuit. The integrator output signal is attached to the output of the integration circuit. The amplifier circuit includes an inverting and a non-inverting amplifier input connection and an amplifier output connection. An amplifier input signal depending on the inverting amplifier output signal is transmitted to the non-inverting amplifier input connection. A voltage signal representing the current through the choke is attached to the amplifier output connection of the amplifier circuit. The NTC resistor is arranged in the feedback path of the amplifier circuit between the inverting amplifier input connection and the amplifier output connection.

[0009] A device is provided for measuring a current, preferably a 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 an amplifier circuit, preferably an active amplifier circuit. The integrator output signal is attached to the output of the integrator circuit. An amplifier input signal, which depends on the integrator output signal, is supplied to the in-phase amplifier input connection, preferably for this purpose the output of the integrator circuit is electrically connected, preferably directly connected, to the in-phase amplifier input connection. An NTC resistor is arranged in the feedback path of the amplifier circuit between the inverting amplifier input connection and the amplifier output connection.

[0010] Advantageously, a device is provided in which an NTC resistor is arranged independently of a possible offset voltage and enables undistorted measurement of bidirectional currents. Since the NTC resistor is decoupled from potential zero offset generation, damage caused by the NTC resistor is avoided. An expansion of the measuring circuit is provided in the case of DCR current measurement for bidirectional currents while maintaining temperature compensation by means of an NTC resistor and an active amplifier circuit without using a bipolar supply voltage.

[0011] In another design solution of the present invention, the amplifier circuit includes an operational amplifier.

[0012] The amplifier circuit comprises an operational amplifier, which preferably operates as a non-inverting operational amplifier. Advantageously, a possibility is provided to provide an efficient amplifier circuit, which enables an economical realization of the device. Preferably, an additional active amplifier circuit is used by means of an operational amplifier, wherein the amplifier stage is also used to amplify the useful signal, in particular the integrator output signal, in order to thereby achieve an improved resolution of the useful signal. Preferably, the amplification of the useful signal is applied when the copper resistance of the choke coil is very small compared to the measured current.

[0013] In another embodiment of the present invention, the device comprises a reference voltage source having a positive source connection and a negative source connection. By means of the reference voltage source, a first offset voltage is coupled into the output of the integration circuit. Preferably, for this purpose, the negative source connection is connected to the output connection of the voltage converter, and the positive source connection is connected to the output of the integration circuit via a coupling resistor.

[0014] By means of a reference voltage source, a first offset voltage is coupled in at the output of the integrator circuit. As a result, the potential of the integrator output signal is increased. This enables the circuit to be used also for currents flowing in the opposite direction. Advantageously, a device is provided which can be used to determine bidirectional currents.

[0015] Preferably, a zero offset, ie a first offset voltage, is generated at the output of the integrator circuit by means of a reference voltage source and is coupled into the signal path as an integrator output signal via a coupling resistor.

[0016] In another embodiment of the present invention, a second offset voltage is coupled into a feedback path at an inverting amplifier input connection of the amplifier circuit by means of a reference voltage source. Preferably, the negative source connection is connected to an output connection of a voltage converter, and the positive source connection is connected to the output connection of the voltage converter via a voltage divider having a first, second and third voltage divider resistor. In addition, preferably, a tap between the second and third voltage divider resistors is connected to the inverting amplifier input connection.

[0017] The second offset voltage is coupled to the inverting amplifier input connection of the amplifier circuit by means of a reference voltage source. Advantageously, preferably by means of parameterization of the voltage divider resistor, it is possible to set 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 identical even when the current through the choke increases.

[0018] Preferably, the amplifier circuit or operational amplifier works as a non-inverting amplifier. If the NTC resistor changes in a temperature-dependent manner, the linear gain factor of the circuit also changes at the same time, because the NTC resistor changes the voltage divider factor in the feedback path. In order to keep the third offset voltage at the output of the amplifier circuit constant regardless of temperature, a reference voltage source is also fed into the feedback path of the amplifier circuit. Here, these voltage divider resistors, preferably three voltage divider resistors, form a voltage divider. By determining the appropriate parameters of the resistors, the second offset voltage at the inverting input of the amplifier circuit is set to be almost the same as the voltage at the non-inverting input. If the current through the choke to be measured increases from 0A to a higher value, only the voltage increase caused by the current change will be amplified. Preferably, when no current flows through the choke, the first, second and third offset voltages remain the same.

[0019] In another embodiment of the invention, a series resistor connected in series with the NTC resistor and a parallel resistor connected in parallel with the series circuit formed by the series resistor and the NTC resistor are arranged in a feedback path of the amplifier circuit between the inverting amplifier input terminal and the amplifier output terminal.

[0020] A series resistor of the NTC resistor and a parallel resistor connected in parallel with the series circuit formed by the series resistor and the NTC resistor are arranged. The three resistors are arranged in the feedback path of the amplifier circuit between the inverting amplifier input connection and the amplifier output connection. Advantageously, a circuit arrangement is provided for linearizing the NTC resistor with temperature. Without this circuit arrangement, the NTC resistor would exhibit nonlinearity with temperature.

[0021] Preferably, the series resistor of the NTC resistor and the parallel resistor connected in parallel with the series circuit consisting of the series resistor and the NTC resistor are used for linearization of the NTC resistor with temperature, because the NTC resistor exhibits nonlinearity with temperature. The series resistor has the effect of preventing the total impedance of the NTC resistor, the series resistor and the parallel resistor from becoming too small at high temperatures. And the parallel resistor has the effect of preventing the total impedance of the NTC resistor, the series resistor and the parallel resistor from becoming too high ohmic at low temperatures.

[0022] In another embodiment of the present invention, the first filter capacitor is arranged in parallel with the NTC resistor.

[0023] Advantageously, a circuit arrangement is provided which sets the gain factor in a frequency-selective manner. A first filter capacitor connected in parallel with the NTC resistor short-circuits the NTC resistor towards higher frequencies, so that the NTC resistor is no longer effective above a certain or determinable angular frequency.

[0024] In another design solution of the present invention, the second filter capacitor is arranged in parallel with the first voltage dividing resistor or the second voltage dividing resistor.

[0025] Advantageously, a circuit arrangement is provided which sets the gain factor in a frequency-selective manner. A second filter capacitor connected in parallel with the first or second voltage-dividing resistor shorts the first or second voltage-dividing resistor towards higher frequencies, so that the first or second voltage-dividing resistor no longer functions from a specific or determinable angular frequency and only one of the two voltage-dividing resistors still functions. Thus, preferably, the NTC resistor functions in a frequency-selective manner only at low frequencies below a specific or determinable angular frequency, preferably the angular frequency of the choke, which results from the quotient of the inductance of the choke and the copper resistance.

[0026] Preferably, an amplifier circuit is provided which enables a measuring range for bidirectional currents and at the same time enables 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 a feedback path of the amplifier circuit.

[0027] In addition, preferably, the time constant of the choke and the integration circuit is kept as constant as possible with temperature so that the amplification factor of the device for measuring the current through the choke, that is, the sensor circuit, remains constant within the frequency range. If this is not the case, the device for measuring the current through the choke may produce measurement errors in the case of rapid changes in current or conversely measure the current too slowly in the case of short-circuit monitoring. Since the NTC resistor in the circuit is no longer connected to the output of the integration circuit, the amplification factor is set in a frequency-selective manner with the aid of the first and second filter capacitors so that the amplification factor remains constant not only with temperature but also across the frequency range. The first filter capacitor short-circuits the NTC resistor toward higher frequencies so that the NTC resistor no longer functions or contributes to the overall amplification from a specific angular frequency. With the second filter capacitor, the effect of the first voltage divider resistor on higher frequencies is blocked so that only the second voltage divider resistor then contributes to the overall amplification. Thus, the amplifier can be set in such a way that the NTC resistor acts in a frequency-selective manner only within a specific frequency range, preferably towards low frequencies, preferably only at low frequencies below a specific or determinable angular frequency, preferably the angular frequency of the choke, which results from the quotient of the inductance of the choke and the copper resistance.

[0028] Therefore, the zero offset generation is preferably decoupled from the NTC resistor and thus enables bidirectional current measurement. In this case, the first, second and third offset voltages are not affected by temperature and also maintain a constant overall transfer function across frequency.

[0029] The invention also relates to a voltage converter having the described device. For this purpose, the voltage converter is designed as an inverter, a DC voltage converter or a charging device.

[0030] Advantageously, a special voltage converter is provided which has a device for measuring the current through the inductor.

[0031] The invention also relates to a drive train for a vehicle, which has a voltage converter. Such a drive train with a voltage converter and the described device is used, for example, for driving an electric vehicle. With the aid of the device, an efficient possibility for measuring the current through the choke is provided.

[0032] The invention also relates to a vehicle having a drive train as described. Advantageously, a vehicle is therefore provided which comprises a device for efficiently measuring the current through a choke.

[0033] The invention also relates to a method for operating a device, the method comprising the following steps: determining a current through an inductor of a voltage converter; and controlling the voltage converter as a function of the determined current.

[0034] Advantageously, a method for efficiently measuring current through a choke is provided.

[0035] The invention also relates to a computer program comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method described thus far.

[0036] The invention also 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.

[0037] It is readily understood that the features, characteristics and advantages of the apparatus can be correspondingly applied or adapted to the method or the powertrain and the vehicle, and vice versa.

[0038] Further features and advantages of embodiments of the invention emerge from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In the following, the invention shall be explained in more detail with reference to several drawings, for which:

[0040] Figure 1 shows a schematic diagram of a voltage converter with a choke;

[0041] Figure 2 A schematic diagram showing a device for measuring the current through a choke of a voltage converter;

[0042] Figure 3 shows a schematic diagram showing the uncompensated variation of the total transfer function with frequency at different temperatures;

[0043] Figure 4 shows a schematic diagram showing the compensated variation of the total transfer function with frequency at different temperatures;

[0044] Figure 5 shows a schematic diagram showing the uncompensated variation of the total transfer function with frequency at different temperatures without a filter capacitor;

[0045] Figure 6 A schematic diagram is shown which shows the partial compensation course of the total transfer function with the frequency at different temperatures in the presence of a first filter capacitor;

[0046] Figure 7shows a schematic diagram showing the compensated course of the total transfer function with frequency at different temperatures with the first and second filter capacitors;

[0047] Figure 8 A schematically presented method for operating the device is shown;

[0048] Fig. 9 A schematically presented vehicle with a powertrain and a voltage converter is shown. DETAILED DESCRIPTION

[0049] Figure 1 1 shows a schematic diagram of a voltage converter 100 with a choke 130. Preferably, the voltage converter 100 is designed as an inverter, a DC voltage converter or a charging device. Figure 1 , the voltage converter is presented as a DC voltage converter by way of example. The voltage converter 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, preferably a smoothing choke, at the output end, which is connected to the output connection 105 of the voltage converter 100 on the output side of the voltage converter 100. During operation of the voltage converter 100, when electrical energy is transferred from the primary circuit 110 to the secondary circuit 120 or vice versa from the secondary circuit to the primary circuit, a current or a load current of the voltage converter 100 flows through the choke 130. Figure 1 Also shown is a device 200 for measuring the current through the choke 130 of the voltage converter 100. The device comprises an integrator circuit 140 connected in parallel with the choke 130. The device 200 also comprises an amplifier circuit. The integrator output signal of the integrator circuit 140 is further processed by means of the amplifier circuit or by means of the operational amplifier 150 shown. The voltage signal representing the current through the choke 130 is applied to the amplifier output terminal 156 of the amplifier circuit.

[0050] Figure 2 A device 200 for measuring a current through an inductor 130 of a voltage converter 100 is shown. Figure 1The output connection 105 of the voltage converter 100 and the choke 130 connected thereto are shown, which is presented as an ohmic DC choke resistor 132 and an inductor 134 of the choke 130 in terms of the equivalent circuit diagram. The device comprises an integrating circuit 140 connected in parallel with the choke 130. The device 200 further comprises an amplifier circuit and an NTC resistor 160. The load current of the voltage converter 100 flows through the choke 130. The integrating circuit 140 comprises a series circuit consisting of an integrating resistor 142 and an integrating capacitor 144. The integrating capacitor 144 is likewise connected to the output connection 105 of the voltage converter 100. A center tap is formed between the integrating resistor 142 and the integrating capacitor 144 as the output of the integrating circuit 140. The integrator output signal is attached to the output of the integrating circuit 140. The amplifier circuit comprises inverting and non-inverting amplifier input connections 152, 154 and an amplifier output connection 156. An amplifier input signal which depends on the integrator output signal is supplied to the non-inverting amplifier input connection 154. A voltage signal which characterizes the current through the choke 130 is attached to the amplifier output connection 156 of the amplifier circuit. The NTC resistor 160 is arranged in the feedback path of the amplifier circuit between the inverting amplifier input connection 152 and the amplifier output connection 156. Preferably, the amplifier circuit comprises an operational amplifier 150 which is preferably designed as a non-inverting operational amplifier. Preferably, the device 200 comprises a reference voltage source 170 which has a positive source connection 172 and a negative source connection 174. By means of the reference voltage source 170, a first offset voltage is coupled in at the output of the integrator circuit 140. Preferably, the negative source connection 174 is connected to the output connection 105 of the voltage converter 100. Preferably, the positive source connection 172 is connected to the output of the integrator circuit 140 via a coupling resistor 176. Furthermore, a second offset voltage is preferably coupled into the feedback path at the inverting amplifier input connection 152 of the amplifier circuit by means of a reference voltage source 170. Preferably, the positive source connection 172 is connected to the output connection 105 of the voltage converter 100 via a voltage divider formed by 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 connection 152. Preferably, a series resistor 162 connected in series with the NTC resistor 160 and a parallel resistor 164 connected in parallel with the series circuit formed by the series resistor 162 and the NTC resistor 160 are arranged in the feedback path of the amplifier circuit between the inverting amplifier input connection 152 and the amplifier output connection 156. It is also preferred that 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.

[0051] The possible power supply designs for this device are as follows: Figure 2 The reference potential of the amplifier circuit or operational amplifier 150 for the voltage after the choke is located at the output connection 105, preferably at the output of the switching power supply or the DC voltage converter. Preferably, a supply voltage is required for powering the amplifier circuit, which supply voltage is greater than the voltage at the output connection 105. Preferably, a charge pump is used or a so-called high-side auxiliary voltage is generated. The voltage signal at the amplifier output connection 156 is preferably transferred to the ground potential by means of another circuit, for example by means of a high-side measuring amplifier or a current mirror.

[0052] 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 measuring amplifier, so that it can then be further processed and preferably supplied as an amplifier input signal dependent on it to a non-inverting amplifier input connection 154. In this case, the reference potential of the reference voltage source and the amplifier circuit is the ground reference potential of the voltage converter.

[0053] Figure 3 A schematic diagram is shown showing the uncompensated variation of the total transfer function in mV (per A) over frequency at different temperatures (T1, T2, T3, T4). For low frequencies, a wide fan-out of the total transfer function at different temperatures (T1, T2, T3, T4) can be observed.

[0054] Figure 4 A schematic diagram is shown which shows the variation of the total transfer function in mV (per A) at different temperatures (T1, T2, T3, T4) over frequency by means of a series resistor 162 connected in series with the NTC resistor 160 in the feedback path and a parallel resistor 164 connected in parallel with the series circuit formed by the series resistor 162 and the NTC resistor 160. Figure 3 , the fan-out of the total transfer function for low frequencies at different temperatures is significantly reduced.

[0055] Figure 5 A schematic diagram is shown which shows the uncompensated variation of the total transfer function in mV (per A) over frequency at different temperatures (T1, T2, T3, T4) without a filter capacitor. Over a large frequency range, a wide fan-out or spread of the total transfer function at different temperatures (T1, T2, T3, T4) can be observed.

[0056] Figure 6A schematic diagram is shown which shows the variation of the total transfer function in mV (per A) at different temperatures (T1, T2, T3, T4) over frequency with partial compensation by means of the first filter capacitor. Figure 5 , the fan-out of the total transfer function over a large frequency range at different temperatures (T1, T2, T3, T4) is significantly reduced. By means of the first filter capacitor, the effect of the NTC resistor is blocked from a certain frequency onwards.

[0057] Figure 7 A schematic diagram is shown which shows the course of the total transfer function in mV (per A) at different temperatures (T1, T2, T3, T4) over frequency, which is compensated by means of the first and second filter capacitors. Figure 6 , an increase in the plateau of the overall transfer function over a large frequency range at different temperatures (T1, T2, T3, T4) can be observed. By means of parameterization of the second filter capacitor, the amplification for higher frequencies can be specified.

[0058] Figure 8 A schematically presented method 400 for operating the device 200 is shown. The method 400 begins with step 410. In step 420, the current through the inductor 130 of the voltage converter 100 is determined. In step 430, the voltage converter 100 is controlled as a function of the determined current. The method ends with step 440.

[0059] Fig. 9 A schematically presented vehicle 290 is shown with a powertrain 300 and a voltage converter 100. The voltage converter comprises a device 200, as described with reference to Figure 2 Preferably, the electric drive train includes a battery (not shown) for powering the drive train, and the battery also preferably includes the inverter 192 and / or the motor 194 .

Claims

1. A device (200) for measuring a current through a choke (130) of a voltage converter (100), The device comprises an integrating circuit (140), an amplifying circuit and an NTC resistor (160). The load current of the voltage converter (100) flows through the choke (130) and the choke (130) is connected to the output connection (105) of the voltage converter (100) on the output side. wherein the integrating circuit (140) is arranged in parallel with the choke (130) and comprises a series circuit consisting of an integrating resistor (142) and an integrating capacitor (144), wherein the integrating capacitor (144) is also connected to the output connection terminal (105) of the voltage converter (100), and the center tap between the integrating resistor (142) and the integrating capacitor (144) is designed as the output terminal of the integrating circuit (140), and the integrator output signal is attached to the output terminal of the integrating circuit (140), The amplifier circuit comprises inverting and non-inverting amplifier input connection terminals (152, 154) and an amplifier output connection terminal (156), and an amplifier input signal depending on the integrator output signal is supplied to the non-inverting amplifier input connection terminal (154), and a voltage signal representative of the current passing through the choke coil (130) is attached to the amplifier output connection terminal (156) of the amplifier circuit, in, The NTC resistor (160) is arranged in a feedback path of the amplifier circuit between an inverting amplifier input connection terminal (152) and an amplifier output connection terminal (156). The device comprises a reference voltage source (170) having a positive source connection (172) and a negative source connection (174), wherein a first offset voltage is coupled into the output of the integrator circuit (140) by means of the reference voltage source (170), The negative source connection terminal (174) is connected to the output connection terminal (105) of the voltage converter (100), and the positive source connection terminal (172) is connected to the output terminal of the integration circuit (140) via a coupling resistor (176).

2. The device (200) according to claim 1, The amplifying circuit comprises an operational amplifier (150), The operational amplifier operates as a non-inverting operational amplifier.

3. The device (200) according to claim 1 or 2, wherein a second offset voltage is coupled into the feedback path at an inverting amplifier input connection (152) of the amplifier circuit by means of the reference voltage source (170), The negative source connection terminal (174) is connected to the output connection terminal (105) of the voltage converter (100), and the positive source connection terminal (172) is connected to the output connection terminal (105) of the voltage converter (100) via a voltage divider composed of first, second and third voltage divider resistors (177, 178, 179), and the tap between the second and third voltage divider resistors (178, 179) is connected to the inverting amplifier input connection terminal (152).

4. The device (200) according to claim 1 or 2, A series resistor (162) connected in series with the NTC resistor (160) and a parallel resistor (164) connected in parallel with the series circuit formed by the series resistor (162) and the NTC resistor (160) are arranged in a feedback path between the inverting amplifier input connection terminal (152) and the amplifier output connection terminal (156) of the amplifier circuit.

5. The device (200) according to claim 1 or 2, The first filter capacitor (166) is arranged in parallel with the NTC resistor (160).

6. The device (200) according to claim 3, The second filter capacitor (168) is arranged in parallel with the first voltage-dividing resistor (177) or the second voltage-dividing resistor (178).

7. A voltage converter (100) comprising a device (200) according to any one of claims 1 to 6, The voltage converter is designed in this case as an inverter, a DC voltage converter or a charging device.

8. A power train (300) of a vehicle (290), comprising the voltage converter (100) according to claim 7.

9. A vehicle (290) having a powertrain (300) according to claim 8.

10. A method (400) for operating a device (200) according to any one of claims 1 to 6, The method comprises the following steps: determining (420) a current through a choke (130) of a voltage converter (100); The voltage converter (100) is controlled (430) based on the determined current.

11. A computer program product having a computer program, the computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the processes / steps of the method (400) according to claim 10.

12. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to implement the processes / steps of the method (400) according to claim 10.

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