Measuring equipment for voltage measurement

Abstract

The present invention relates to a measuring device (110) for measuring an AC input voltage (103). The measuring device (110) includes a first voltage divider (211) configured to couple a first terminal of the input voltage (103) to a first terminal of at least one measuring resistor (215), such that a scaled voltage (202) exists as a scaled version of the input voltage (103) across the measuring resistor (215). Furthermore, the measuring device (110) includes a bias unit (213) configured to shift the scaled voltage (202) by means of a biased DC voltage (203) to provide an offset voltage (204) that does not have a polarity reversal.

Description

Technical Field

[0001] The present invention relates to a device, and more particularly to a circuit apparatus for measuring voltage, especially AC voltage. Background Technology

[0002] Household appliances, such as washing machines or dishwashers, typically have mains connections, especially switching power supplies, which allow them to connect to an AC power grid. The mains voltage supplied by the power grid can fluctuate with respect to voltage levels and / or frequency. Such fluctuations can lead to overvoltage conditions and / or power consumption fluctuations in the household appliances, and thus, if necessary, damage to their operation. Summary of the Invention

[0003] The technical problem this document aims to solve is to enable reliable and stable operation of household appliances even under fluctuating supply voltage.

[0004] This technical problem is solved by the subject matter of the independent claims. Advantageous embodiments are defined in particular in the dependent claims, described in the following description, or illustrated in the drawings.

[0005] According to one aspect of the invention, a measuring device for measuring AC (alternating current) input voltage is described. The measuring device can particularly be configured to provide a measuring signal for the AC input voltage, which can be reliably and efficiently read by a microprocessor in a safe ultra-low voltage (SELV) environment. For example, the AC input voltage can be a 230V supply voltage.

[0006] The measuring device includes a first voltage divider configured to couple a first terminal of the input voltage, such as a neutral conductor or a phase conductor, to a first terminal of at least one measuring resistor. The at least one measuring resistor may, if necessary, comprise a network of one or more dividing resistors.

[0007] The measuring device may further include a second voltage divider configured to couple the second pole of the input voltage (e.g., in a manner complementary to the first voltage divider), the phase conductor, or the neutral conductor to the second pole of the measuring resistance.

[0008] By using a first voltage divider and, if necessary, a second voltage divider, a scaled voltage (skalierteSpannung) can be generated as a scaled version of the input voltage across the measuring resistor. Here, the input voltage can, for example, have an amplitude of 100V or greater. On the other hand, the scaled voltage can have an amplitude of 50V or less. Over time, the scaled voltage can correspond to the input voltage, however, with a reduced amplitude compared to the input voltage. The scaled voltage can be a voltage relative to ground or earth.

[0009] The first and / or second voltage dividers may each have a first resistor and a second resistor arranged in series with each other. If necessary, each voltage divider may have two or more (series-connected) resistors. Here, the first and / or second resistors may each have a resistance value of 500 kOhm or greater, especially 1 MOhm or greater. In other words, the first and / or second resistors may each have high resistance values ​​to meet one or more SELV requirements, especially SELV requirements for protective impedance. Therefore, scaling of the input voltage can be achieved in an efficient and reliable manner.

[0010] The first and / or second voltage divider can be configured to cause current separation between the input voltage and the scaled voltage. Alternatively or additionally, the first and / or second voltage divider can be configured to cause SELV separation between the input voltage and the scaled voltage. In particular, current separation and / or SELV separation can be caused by a resistor connected in series with the voltage divider. Here, the resistance value can be sufficiently high (e.g., 500 kOhm or greater), and the resulting current is sufficiently small to cause current separation and / or SELV separation. The resistor can therefore be used as a protective impedance. This enables particularly safe voltage measurements.

[0011] The measuring device further includes a bias unit configured to shift and scale the voltage by biasing a DC voltage, thereby providing an offset, particularly an increased, voltage (as a measurement signal of the input voltage). The offset voltage is designed to be polarity-free. In other words, the offset voltage is designed to be either positive (≥0V) or negative (≤0V) at all times. Therefore, the offset voltage can be transmitted to the microprocessor as a measurement signal of the input voltage in an efficient and reliable manner.

[0012] The bias unit may include an operational amplifier having a first input terminal, particularly a positive input terminal, for a bias DC voltage, and a second input terminal, particularly a negative input terminal, for a scaled voltage. Therefore, a shift, particularly an increase, in the scaled voltage can be caused in a particularly effective and reliable manner.

[0013] The measuring device may include a comparator unit configured to compare an offset voltage with a reference voltage to generate a comparator signal, particularly a rectangular comparator signal, whose edges indicate the zero-crossing point of the input voltage or a specific phase or phase angle of the input voltage. Here, the reference voltage may correspond to a bias DC voltage (especially when identifying the zero-crossing point, zero phase, or zero phase angle). Typically, the phase or phase angle of the input voltage can be determined by adjusting the reference voltage, and this phase or phase angle should be identified by the measuring device.

[0014] The comparator unit may include an operational amplifier having a first input terminal, particularly a positive input terminal, for a reference voltage and a second input terminal, particularly a negative input terminal, for an offset voltage. Therefore, the zero-crossing point of the input voltage can be shown in an efficient and reliable manner (within the SELV range).

[0015] The measuring device may include an analog-to-digital converter (ADC) configured to process the offset voltage and / or comparator signal into digital signals for processing in a microprocessor. The ADC may be part of the microprocessor. Therefore, information about the input voltage can be processed efficiently and reliably. In particular, the magnitude of the input voltage can be determined based on the digitized offset voltage (via the microprocessor), and / or one or more zero-crossings of the input voltage can be identified. This can be done efficiently and safely within the SELV range.

[0016] According to another aspect, a household appliance (e.g., a washing machine, dishwasher, oven, stove, kitchen appliance, vacuum cleaner, dryer, refrigerator, etc.) is described, which includes the measuring device described in this document. The household appliance may in particular include a power outlet for connecting the household appliance to an AC supply voltage. The measuring device may be configured to generate a voltage offset based on the AC supply voltage.

[0017] Household appliances may further include a control unit configured to operate the appliance based on a voltage offset, particularly the magnitude of the voltage offset. For example, power control or regulation of the appliance can be performed based on the magnitude of the voltage offset. Therefore, particularly safe and reliable operation of the household appliance can be achieved.

[0018] It should be noted that any aspect of the measuring device described in this document can be combined with each other in various ways. In particular, the features of the claims can be combined with each other in various ways. Attached Figure Description

[0019] Furthermore, the present invention is described in detail with reference to embodiments shown in the accompanying drawings. Herein:

[0020] Figure 1 A block diagram of an exemplary household appliance is shown;

[0021] Figure 2 A block diagram of an exemplary measuring device for voltage measurement is shown; and

[0022] Figure 3 An exemplary voltage trend over time is shown. Detailed Implementation

[0023] As stated at the beginning, this document relates to ensuring the stable and reliable operation of household appliances in an efficient manner, even under conditions of fluctuating supply voltage. Under this relationship, Figure 1 An exemplary household appliance 100, such as a washing machine, is shown, having a mains connection 102, and in particular a switching power supply, through which the appliance 100 can be connected to an alternating current supply voltage 103. The appliance 100 includes a measuring device 110 configured to detect one or more measuring signals associated with the supply voltage 103. These one or more measuring signals can be evaluated by a control unit 101 of the appliance 100 (e.g., via a microprocessor), particularly to adapt the operation of the appliance 100 to the current characteristics, such as amplitude and / or frequency, of the supply or mains voltage 103. Therefore, stable and reliable operation of the appliance 100 can be achieved even in the event of fluctuations in the supply voltage 103.

[0024] Figure 2 A circuit diagram of an exemplary measuring device 110 is shown. The measuring device 110 includes one or more voltage dividers 211, 212 at its input terminals 221, 222, configured to reduce the voltage level of the supply voltage 103 to a low voltage level, for example, less than 50V. Specifically, the measuring device 110 may include a first input node 221 (which may be connected, for example, to the neutral conductor of the supply voltage 103) and a second input node 222, which may be connected, for example, to the phase conductor of the supply voltage 103 (or vice versa). The first input node 221 may be connected to the first voltage divider 211 and / or the second input node 222 may be connected to the second voltage divider 212. The resistors of the voltage dividers 211, 222 may each have an ohmic resistance of 1 MOhm (within this range).

[0025] Furthermore, at least a first voltage divider 211 or at least a second voltage divider 212 may be coupled to at least one measuring resistor 215 to provide a scaled voltage 202 within the SELV range. Specifically, the two voltage dividers 211, 212 may be connected to different ends or poles of at least one measuring resistor 215 or a network of measuring resistors 215, in which the scaled voltage 202 drops to a low voltage level. The scaled voltage 202 may represent a scaled copy of the supply voltage 103. The scaled voltage 202 may here be a voltage relative to ground or earth. Figure 3 The period of the supply voltage 103 with a voltage amplitude 301 in the high voltage range is shown. Furthermore, Figure 3 The corresponding period of the scaled voltage 202 with voltage amplitude 302 in the low voltage range is shown.

[0026] Figure 2The measuring device 110 shown can achieve current separation of the supply voltage 103 (to the left of the vertical dashed line) and the scaling voltage 202 (to the right of the vertical dashed line) by using voltage dividers 211 and 212. The portion of the measuring device 110 arranged to the right of the vertical dashed line can be in the SELV (Safety Extra Low Voltage) range.

[0027] The scaling voltage 202 can be conducted to the input of the bias unit 213, particularly the negative input. The bias unit 213 can be configured to shift the scaling voltage 202 by an amplitude of a bias DC voltage 203 to provide an offset, particularly elevated voltage 204. The bias DC voltage 203 can be located at the other input of the bias unit 213, particularly the positive input. The bias unit 213 may include an operational amplifier. Figure 3 The scaling voltage 202, i.e., the increased or offset voltage 204, is shown to shift the bias DC voltage 203.

[0028] The increased voltage 204 can represent a scaled and shifted version of the supply voltage 103, without sign transformation, and for example, has only positive voltage values. The increased voltage 204 can be read and evaluated efficiently and reliably via, for example, a microprocessor, or an analog-to-digital converter of the control unit 101 of the household appliance 100. The digitized increased voltage 204 can then be evaluated by the control unit 101, for example, to determine the magnitude of the supply voltage 103 and / or to detect the zero-crossing points of the supply voltage 103.

[0029] The measuring device 110 may further include a comparison unit 214, particularly a comparator, configured to compare the increased voltage 204 with a reference DC voltage 205 in order to detect one or more zero-crossing points of the supply voltage 103 (by means of circuit elements). A comparator signal 206 with an edge can then be output at the output of the comparison unit 214, such as... Figure 3 As shown, each edge indicates the zero-crossing point of the supply voltage 103.

[0030] Therefore, a measuring device 110 is described, which causes current separation of the input voltage 103 based on resistance (especially based on protective impedance). The transformed or scaled voltage 202 derived from the input voltage 103 can be processed using an operational amplifier 213. The scaled AC voltage signal 202 can be amplified, in particular, by means of a bias DC voltage 203, to provide an amplified voltage signal 204, which has no negative value and can therefore be reliably and accurately read by a microprocessor.

[0031] Furthermore, the zero-crossing point of the input voltage 103 can be detected on the elevated voltage signal 204, which has already been current-separated, and processed into a rectangular signal 206 by the comparator 214, which can be transmitted to the microprocessor.

[0032] The measuring device 110 described in this document, and in particular the described circuitry, can simultaneously perform multiple functions, such as voltage measurement, providing a safe SELV signal on the analog-to-digital converter (ADC), and zero-crossing measurement (or phase measurement or phase angle measurement). Here, the measuring device 100 can be effectively adapted to different applications by adapting the bias DC voltage 203 and / or the reference voltage 205.

[0033] The measuring device 110 described in this document can be used in electronic and / or electrical devices 100 with SELV separation, especially for microprocessors, to provide voltage measurement and / or zero-crossing identification on the SELV side.

[0034] The measuring device 110 described in this document can provide effective voltage and / or zero-crossing measurements with high accuracy and high temperature stability. Furthermore, the described measuring device 110 has a long service life.

[0035] This invention is not limited to the embodiments shown. It should be noted, in particular, that the specification and drawings are intended to illustrate only the principles of the proposed measuring device.

Claims

1. Measuring device (110) for measuring an AC input voltage (103); wherein the measuring device (110) comprises: - a first voltage divider (211) configured for coupling a first pole of the input voltage (103) with a first pole of at least one measuring resistor (215), so that a scaled voltage (202) as a scaled version of the input voltage (103) is present on the measuring resistor (215); and - a biasing unit (213) arranged for shifting the scaled voltage (202) by means of a biasing direct current voltage (203) in order to provide an offset voltage (204) which does not have a polarity change.

2. Measuring device (110) according to claim 1, wherein the measuring device (110) comprises a second voltage divider (212) configured for coupling a second pole of the input voltage (103) with a second pole of the measuring resistor (215).

3. Measuring device (110) according to claim 2, wherein the first and second voltage dividers (211, 212) are configured for causing a galvanic separation between the input voltage (103) and the scaled voltage (202).

4. Measuring device (110) according to claim 2 or 3, wherein the first and second voltage dividers (211, 212) are configured for causing a safety extra-low voltage separation, in short SELV separation, between the input voltage (103) and the scaled voltage (202).

5. Measuring device (110) according to any one of the preceding claims 1 to 3, wherein - the input voltage (103) has an amplitude (301) of 100 V or more; and - the scaled voltage (202) has an amplitude (302) of 50 V or less.

6. Measuring device (110) according to claim 2 or 3, wherein - the first and second voltage dividers (211, 212) have a first resistance and a second resistance, respectively, arranged in series with each other; and - the first resistance and / or the second resistance have a resistance value of 500 kOhm or more, respectively; and / or - the first resistance and / or the second resistance have a high resistance value, respectively, so as to fulfill one or more SELV requirements for a protective impedance.

7. Measuring device (110) according to any one of the preceding claims 1 to 3, wherein the biasing unit (213) comprises an operational amplifier having a first input for the biasing direct current voltage (203) and a second input for the scaled voltage (202).

8. Measuring device (110) according to any one of the preceding claims 1 to 3, wherein the measuring device (110) comprises a comparison unit (214) arranged for comparing the offset voltage (204) with a reference voltage (205) in order to generate a comparator signal (206) which shows a specific phase or a specific phase angle of the input voltage (103), respectively, as an edge.

9. The measuring device (110) according to claim 8, wherein the comparison unit (214) comprises an operational amplifier having a first input for the reference voltage (205) and a second input for the offset voltage (204).

10. The measuring device (110) according to any of the preceding claims 1 to 3, wherein the measuring device (110) comprises an analog-digital converter arranged for processing the offset voltage (204) into a digital signal for processing in a microprocessor.

11. The measuring device (110) according to claim 6, wherein the first resistance and / or the second resistance has a resistance value of 1 MOhm or more, respectively.

12. The measuring device (110) according to claim 8, wherein the comparator signal is a rectangular comparator signal (206).

13. The measuring device (110) according to claim 8, wherein the comparator signal shows zero-crossings, respectively.

14. The measuring device (110) according to claim 9, wherein the first input is a positive input and the second input is a negative input.

15. A household appliance (100) comprising: - a grid connection (102) for connecting the household appliance (100) to an AC supply voltage (103); - a measuring device (110) according to any of the preceding claims, wherein the measuring device (110) is arranged for generating an offset voltage (204) based on the AC supply voltage (103); and - a control unit (101) arranged for operating a function of the household appliance (100) in dependence of the offset voltage (204).

16. The household appliance (100) according to claim 15, wherein the control unit (101) is arranged for operating the function of the household appliance (100) in dependence of an amplitude of the offset voltage (204). ​

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