Measuring device and method for measuring electric current
By setting up an addition element, a low-pass filter and an analog-to-digital converter in each channel of the measurement device, adding the signals of the two measurement channels and filtering, the noise signal jump problem caused by high-frequency interference in the prior art is solved, and accurate and stable signal measurement is achieved.
Patent Information
- Application Number
- CN202380070841.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-10-05
- Filing Date
- 2023-09-14
- Publication Date
- 2025-05-13
AI Technical Summary
The prior art is difficult to effectively protect the measurement signal from high-frequency interference, resulting in noise signal jumps in a higher frequency range, affecting the accuracy of the measurement signal.
A measurement device is designed to achieve signal filtering by setting an addition element, a low-pass filter and an analog-to-digital converter in each measurement channel, adding signals from two measurement channels, and converting the signal into a continuous change process through a low-pass filter.
It effectively avoids signal jumps, realizes effective filtering of high-frequency interference of the measurement signal, and ensures the accuracy of the measurement signal.
Smart Images
Figure CN119998668A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a measuring device for measuring a current flowing through an electrical consumer from a center tap between two transistors of a half bridge according to the preamble of claim 1, and a method for measuring a current flowing through an electrical consumer from a center tap between two transistors of a half bridge according to the preamble of claim 5. Background Art
[0002] In order to protect the measuring channels in the electronic circuits from interfering coupling inputs, low-pass filters TPF are usually used, which are usually designed according to Figure 1 A first-order or higher-order RC element is connected in parallel with the shunt SH.
[0003] Figure 1 The prerequisite for the measurement setup shown is that the signal to be measured has a continuous course. This is the case for the current I flowing from the center tap of the half-bridge consisting of the two transistors T1, T2 through the shunt SH, which in this example allows the current I to be measured with the aid of a voltmeter V. The voltmeter V can therefore be protected from high-frequency interference by a low-pass filter TPF. Figure 2 The measurement configuration in does not meet this prerequisite.
[0004] exist Figure 2 In the example of , the voltage drop across the channel resistance of each conducting transistor T1, T2 of the half-bridge is measured and evaluated again with a voltmeter. Figure 2 In the diagram, the combination is shown in simplified form as an ammeter A. Therefore, the current I can only be measured when the corresponding transistors T1 and T2 are turned on. Figure 3 and Figure 4 Here, the two partial current measurement results are shown in Figure 3 shows the variation of the current I flowing through the upper transistor T1 with time t, and Figure 4 The diagram shows the course of the current I flowing through the lower transistor T2 over time t. Since the low-pass filter TPF only displays the average value of the measurement signal above approximately ten times the cut-off frequency, the low-pass filter TPF cannot be used to protect the ammeter A from interference at the measurement input. As a result, the analog-to-digital converters ADC1, ADC2, which are usually used to record the measurement signal, are not protected, resulting in jitters. In other words, noise signals in the higher frequency range (e.g. signal jumps) are modulated into the functional range due to a violation of the Nyquist-Shannon theorem and interpreted as a measurement signal. Summary of the invention
[0005] The object of the present invention is to specify a novel measuring device and a novel method for measuring the current flowing through an electrical consumer from a center tap between two transistors of a half bridge.
[0006] This object is achieved according to the invention by a measuring device having the features of claim 1 and a method having the features of claim 5 .
[0007] Advantageous embodiments of the invention are the subject matter of the dependent claims.
[0008] According to the present invention, a measuring device for measuring a current flowing through an electrical consumer from a center tap between two transistors of a half bridge is provided, wherein the measuring device is configured to measure, for the two transistors, the voltage across the channel resistance of the transistor in a separate measuring channel when the corresponding transistor is turned on. According to the present invention, each measuring channel has an adding element, a low-pass filter and an analog-to-digital converter, so that in each measuring channel, a signal of a corresponding voltage drop can be supplied to the analog-to-digital converter via the adding element and the low-pass filter, wherein the adding element of each measuring channel is configured to add the signal of the corresponding measuring channel to the signal of the corresponding other measuring channel.
[0009] In this way, discontinuous signal profiles are converted into continuous signal profiles in each measuring channel, thereby achieving filterability.
[0010] In one embodiment, the low pass filter is a first order or higher order low pass filter.
[0011] According to one aspect of the invention, a device is proposed which comprises a measurement arrangement as described above and a half-bridge with two transistors and a consumer fed from a center tap between the two transistors.
[0012] In one embodiment, the transistors are designed as field effect transistors, wherein the source of the upper transistor is connected to the drain of the lower transistor.
[0013] According to one aspect of the present invention, a method for measuring a current flowing through an electrical consumer from a center tap between two transistors of a half bridge is proposed, wherein for the two transistors, when the corresponding transistor is turned on, the voltage across the channel resistance of the transistor is respectively measured in a separate measurement channel. According to the present invention, in each measurement channel, the signal of the corresponding voltage drop is supplied to an analog-to-digital converter via an adding element and a low-pass filter, wherein in the adding element of each measurement channel, the signal of the corresponding measurement channel is added to the signal of the corresponding other measurement channel. In this way, a discontinuous signal change process is converted into a continuous signal change process in each measurement channel, thereby achieving filterability. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Embodiments of the present invention are explained in more detail below based on the accompanying drawings.
[0015] Figure 1 shows a schematic diagram of a half-bridge with a measuring device according to the prior art for measuring the current flowing through the load from the half-bridge,
[0016] Figure 2 shows a schematic diagram of a half-bridge with a further measuring device according to the prior art for measuring the current flowing through the load from the half-bridge,
[0017] Figure 3 shows the course of the current flowing through the upper transistor of a measurement device according to the prior art,
[0018] Figure 4 shows the variation of the current flowing through the lower transistor of the measurement device according to the prior art,
[0019] Figure 5 A schematic diagram of a measuring device for measuring a current flowing through a consumer from a half-bridge according to the present invention is shown,
[0020] Figure 6 Shown according to Figure 5 Schematic diagram of the change process of the current in the lower measurement channel of the measurement device,
[0021] Figure 7 Shown according to Figure 5 Another schematic diagram of the measuring device, and
[0022] Figure 8 Shown according to Figure 5 and Figure 7 Schematic diagram of the current variation process in the upper measurement channel of the measurement device.
[0023] In all the Figures, parts which correspond to one another are provided with the same reference numerals. DETAILED DESCRIPTION
[0024] Figure 1 is a schematic diagram of a half-bridge HB, which comprises two transistors T1, T2, in particular field effect transistors, wherein the source S of the upper transistor T1 is connected to the drain D of the lower transistor T2. In order to measure the current I flowing through the consumer L from the center tap M between the two transistors T1, T2, a measuring device is provided, which has a shunt SH between the consumer L and the center tap M. By measuring the voltage drop across the shunt SH with the aid of a voltmeter V, the current I can be determined knowing the resistance of the shunt SH. In order to protect the measurement channel in the electronic circuit from interfering input coupling, a low-pass filter TPF is usually used, which is mostly designed as a first-order or higher-order RC element. The low-pass filter TPF shown by way of example comprises a series circuit consisting of a resistor R and a capacitor C, which is connected in parallel with the shunt SH and the voltmeter V is connected in parallel with the capacitor C.
[0025] The signal to be measured should have a continuous profile. This is the case for the current I flowing from the center tap M of the half-bridge HB consisting of the two transistors T1, T2 through the shunt SH, which in this example allows the current I to be measured with the aid of a voltmeter V. The voltmeter V can therefore be protected from high-frequency interference by a low-pass filter TPF.
[0026] Figure 2 is a schematic diagram of a half-bridge HB comprising two transistors T1, T2, in particular field effect transistors, wherein the source S of the upper transistor T1 is connected to the drain D of the lower transistor T2. In order to measure the current I flowing through the consumer L from the center tap M between the two transistors T1, T2, an alternative measuring arrangement is provided, in which the voltage drop across the channel resistance of each conducting transistor T1, T2 of the half-bridge is measured and again evaluated with a voltmeter V. Figure 2 In the example, the combination is shown as an ammeter A. Therefore, the current I can only be measured when the corresponding transistor T1, T2 is turned on (for example, when the gate G of the transistor T1, T2 is driven by a pulse width modulated signal). Figure 3 and Figure 4 Here, the two partial current measurement results are shown in Figure 3 shows the variation of the current I flowing through the upper transistor T1 with time t, and Figure 4 The figure shows the variation of the current I flowing through the lower transistor T2 over time t. Since the low-pass filter TPF only displays the average value of the measurement signal above about ten times the cut-off frequency, the low-pass filter is used according to Figure 2 In measuring devices with a high frequency range, the analog-to-digital converter ADC1, ADC2 cannot be used to protect against interference at the measuring input. As a result, the analog-to-digital converters ADC1, ADC2, which are usually used to record the measuring signal, are not protected and jitters occur as a result. In other words, noise signals in the higher frequency range (e.g. signal jumps) are modulated into the functional range due to a violation of the Nyquist-Shannon theorem and interpreted as a measuring signal.
[0027] Figure 5 is a schematic diagram of a measuring device 1 having a Figure 2 The voltage drop across the channel resistance of the upper transistor T1 is the signal of the upper measurement channel OMK of SO and the Figure 2 The lower measurement channel UMK of the signal SU of the voltage drop across the channel resistance of the lower transistor T2. In each measurement channel OMK, UMK, the corresponding voltage drop signal SO, SU is delivered to the analog-to-digital converter ADC1, ADC2 via the adding element AG and the low-pass filter TPF.
[0028] exist Figure 5In the example, the signal SO of the upper measurement channel OMK is added to the lower measurement channel UMK via the adding element AG in an additive manner. Here, the change process of the current I before the low-pass filter TPF is obtained by taking into account the channel resistance, as shown in FIG. Figure 6 Shown schematically.
[0029] Figure 7 is based on Figure 5 Schematic diagram of a measuring device 1, in which the signal SU of the lower measuring channel UMK is added to the upper measuring channel OMK via an adding element AG. Here, the course of the current I before the low-pass filter TPF is obtained taking into account the channel resistance, as shown in Figure 8 Shown schematically.
[0030] Figure 6 and Figure 8 It is clear that signal jumps are avoided by this addition. Figure 6 and Figure 8 , can be filtered in the measuring device with the aid of a low-pass filter TPF.
[0031] If the measurement is continued only within the active time window in each case, ie during the conductive period of the respective transistor T1 , T2 , further required information, such as the current corners, can be evaluated as before.
[0032] Reference numerals list
[0033] 1 Measurement setup
[0034] A Ammeter
[0035] ADC1, ADC2 analog-to-digital converter
[0036] AG Adder
[0037] C Capacitor
[0038] D Drain
[0039] G Gate
[0040] HB Half Bridge
[0041] I Current
[0042] L Electrical consumption
[0043] M Center tap
[0044] OMK upper measuring channel
[0045] R Resistor
[0046] S Source
[0047] SH Shunt
[0048] SO, SU signals
[0049] t time
[0050] T1, T2 transistors
[0051] TPF Low Pass Filter
[0052] UMK lower measuring channel
[0053] V Voltmeter
Claims
1. A measuring device for measuring a current (I) flowing through an electrical consumer (L) from a center tap (M) between two transistors (T1, T2) of a half bridge (HB), wherein the measuring device is configured to measure, for the two transistors (T1, T2), in separate measuring channels (OMK, UMK) the voltage across the channel resistance of each transistor (T1, T2) when the respective transistor (T1, T2) is switched on, It is characterized in that Each measuring channel (OMK, UMK) has an adding element (AG), a low-pass filter (TPF) and an analog-to-digital converter (ADC1, ADC2), so that in each measuring channel (OMK, UMK), the signal (SO, SU) of the corresponding voltage drop can be transmitted to the analog-to-digital converter (ADC1, ADC2) via the adding element (AG) and the low-pass filter (TPF), wherein the adding element (AG) of each measuring channel (OMK, UMK) is configured to add the signal (SO, SU) of the corresponding measuring channel (OMK, UMK) with the signal (SO, SU) of another corresponding measuring channel (OMK, UMK).
2. The measuring device according to claim 1, characterized in that The low pass filter (LPF) is a first order or higher order low pass filter (LPF).
3. A device comprising a measurement arrangement according to claim 1 or 2, characterized in that The device also comprises a half-bridge (HB) having two transistors (T1, T2) and a consumer (L) which is fed from a center tap (M) between the two transistors (T1, T2).
4. The device according to claim 3, characterized in that The transistors (T1, T2) are designed as field effect transistors, wherein the source (S) of the upper transistor (T1) is connected to the drain (D) of the lower transistor (T2).
5. A method for measuring a current (I) flowing through an electrical consumer (L) from a center tap (M) between two transistors (T1, T2) of a half bridge (HB), wherein for the two transistors (T1, T2), when the respective transistor (T1, T2) is switched on, the voltage across the channel resistance of the transistor (T1, T2) is measured in separate measuring channels (OMK, UMK), It is characterized in that In each measuring channel (OMK, UMK), the signal (SO, SU) of the corresponding voltage drop is supplied to the analog-to-digital converter (ADC1, ADC2) via an adding element (AG) and a low-pass filter (TPF), wherein in the adding element (AG) of each measuring channel (OMK, UMK), the signal (SO, SU) of the corresponding measuring channel (OMK, UMK) is added to the signal (SO, SU) of the corresponding other measuring channel (OMK, UMK).