Method and system for evaluating an input voltage of a power supply

Abstract

The invention relates to: a method for evaluating the input voltage of a power supply or a switched-mode power supply, the input voltage having a defined polarity; and a system for performing the method. The input voltage is digitized by means of an analog-to-digital converter by sampling using a predefined sampling rate. The digitized input voltage is fed as an input signal to a filter unit and filtered such that the output signal of the filter unit lags behind the input signal at the input of the filter unit. The input signal and the output signal of the filter unit are compared by means of a comparator unit, and a sequence controller evaluates the comparison result provided by the comparator unit. During an evaluation period which is started by resetting at least a counter unit, the comparison result is continuously evaluated until a further state change is detected after the first state change of the comparison result. The respective evaluation period is ended, and the period duration and / or the frequency of the alternating voltage component of the input voltage are determined on the basis of the current count value of the counter unit.

Description

Field of the Invention

[0001] Generally speaking, the present invention relates to the field of electrical engineering, especially in the fields of power electronics and power electronic circuits. In particular, the present invention relates to a method for evaluating the input voltage of a power supply or a switched-mode power supply, wherein the input voltage has a definite polarity. The present invention also relates to a system for carrying out the method for evaluating the input voltage of a switched-mode power supply. Background Art

[0002] In manufacturing and automation technologies, power supplies or switched-mode power supplies are widely used to supply power to power-consuming devices such as electronic controllers, pumps, valves, sensors, etc. These power-consuming devices are supplied with a suitable and usually pre-defined voltage by the power supply or the switched-mode power supply. For this purpose, the high voltage level on the input side of the switched-mode power supply is usually converted to a pre-defined, lower and usually constant voltage level for these power-consuming devices on the output side of the switched-mode power supply.

[0003] The power supply of the switched-mode power supply is usually realized by using the grid voltage from a single-phase or three-phase power supply network as the supply voltage. In the case of a single-phase or three-phase grid voltage (such as 230V alternating voltage, three-phase alternating voltage) as the supply voltage, the switched-mode power supply usually has an input stage - for example, in the form of a rectifier unit, through which the alternating voltage from the power supply network is converted into a time-varying, mostly pulsating DC voltage, as the input voltage of the switched-mode power supply. That is to say, after the input stage or after the rectifier unit, there is usually an input voltage with a definite polarity (that is, the polarity of the input voltage remains the same or does not change over time), but the amplitude of the input voltage changes over time or fluctuates over time. Then, the power supply or the switched-mode power supply converts this input voltage into a constant output voltage for the power-consuming device, wherein the constancy of the output voltage and / or output current is achieved by regulating the energy flow.

[0004] For a switched-mode power supply, it has become increasingly important to identify grid conditions - such as grid frequency, grid voltage, etc. - and also disturbances in the power supply network (e.g., phase failure, overvoltage pulses or surges, etc. in the case of three-phase supply voltage). For example, since a switched-mode power supply can operate optimally only within a certain range of the input voltage, it is important to know the grid conditions in order to take measures when deviating from the optimal input voltage range. In particular, undervoltage on the input side or undervoltage from the power supply network may cause an increase in the input current, for example due to the constancy of the output voltage of the switched-mode power supply. This may, for example, lead to overheating of the components of the switched-mode power supply or even cause damage. Thus, for safety reasons, the supply voltage or the input voltage is usually monitored, and if necessary, the output of the switched-mode power supply is switched off, for example when it is below a pre-given value. In order to prevent overheating or damage of the switched-mode power supply caused by undervoltage on the input side or undervoltage from the power supply network, it is necessary to continuously and as precisely as possible monitor the input voltage of the switched-mode power supply in order to take measures (such as switching off the output of the switched-mode power supply, etc.) if necessary. Here, in particular, the frequency of the amplitude change over time of the input voltage of the switched-mode power supply or the alternating voltage component of the input voltage of the switched-mode power supply can be determined, as well as the amplitude fluctuations of the input voltage, etc.

[0005] Common variants of frequency and voltage measurement are, for example, Fourier analysis. Fourier analysis is mainly used to decompose a time-varying or periodic signal into a sum of sine functions with different frequencies and amplitudes. If non-sinusoidal oscillations are assumed in Fourier analysis, the harmonics involved can be determined, for example, by Fourier analysis. That is, in the case of a rectified alternating voltage as the input voltage, the alternating voltage component, in particular the frequency of the alternating voltage component, can be determined by Fourier analysis. In addition, disturbances in the grid voltage can also be identified by Fourier analysis, for example. However, in order to evaluate the input voltage of a switched-mode power supply by means of Fourier analysis, for example, a corresponding measuring device or corresponding logic is required, by which the Fourier analysis is carried out. This leads, for example, to additional hardware costs and / or storage requirements for the corresponding computational algorithms.

[0006] Another possibility for performing frequency and voltage measurements at the input voltage of a switched-mode power supply is, for example, a time measurement between two predefined or fixed points of the input voltage. Subsequently, based on the duration between these two predefined points of the input voltage, for example, the frequency of the time-varying amplitude of the input voltage of the switched-mode power supply can be derived. However, for this purpose, it is necessary to: measure the duration between the predefined points, for example, by means of an additional measuring device; and the corresponding points of the input voltage can be predefined accordingly. That is to say, in order to define fixed measuring points, a more approximate time-varying process of the input voltage should be known, otherwise the derivation of the frequency may be very inaccurate or incorrect.

[0007] Furthermore, from the applicant's hitherto unpublished European patent application No. 19205873.3, for example, a circuit device and a method are known by which the input voltage of a power supply can be evaluated. Here, two output signals are derived by means of an analog circuit device based on the supply voltage of the power supply or the switched-mode power supply, and based on these two output signals, a measured value (for example, an average value) of the supply voltage and the voltage type (for example, a DC voltage or an alternating voltage) of the supply voltage can be derived. However, this circuit device and especially the associated method have the following disadvantages: this circuit device and method can mainly be applied to the evaluation of the supply voltage of a single-phase power supply. In addition, the evaluation of the supply voltage or the input voltage of the switched-mode power supply requires additional circuit devices and thus incurs additional costs. In addition, only the voltage type of the supply voltage of the switched-mode power supply can be derived by means of this circuit device or the associated method. That is to say, this method only identifies whether the supply voltage is a DC voltage or a single-phase alternating voltage, and the frequency of this supply voltage can only be roughly estimated. The precise evaluation of the input voltage of the switched-mode power supply, especially the rectified three-phase supply voltage, cannot be achieved by means of this circuit device or the associated method. Summary of the Invention

[0008] Therefore, the object underlying the present invention is to describe a method and a system for evaluating the input voltage of a switched-mode power supply, which method and system can achieve a precise evaluation of an input voltage with a distinct polarity and a time-varying amplitude in a simple and cost-effective manner at low cost.

[0009] This object is solved by a method of the type mentioned at the beginning and by a system for performing this method. Advantageous embodiments of the present invention are described below.

[0010] According to the present invention, the solution to this task is achieved by a method for evaluating the input voltage of a power supply or a switched-mode power supply. Here, the input voltage to be evaluated has a definite polarity. That is to say, although the input voltage of the switched-mode power supply varies with time in terms of its amplitude, the polarity remains the same or does not change over time - such as in the case of a DC voltage fluctuating over time or a rectified single-phase or three-phase alternating voltage or a so-called pulsating DC voltage. The input voltage is sampled or digitized by means of sampling using a pre-given sampling rate. Here, the period duration of the sampling rate or the sampling clock is significantly shorter than the period duration of the expected frequency of the alternating voltage component or the ripple of the input voltage, or the frequency of the sampling clock is significantly higher than the expected frequency of the alternating voltage component or the ripple of the input voltage to be evaluated. Then, the digitized input voltage is fed as an input signal to a filter unit and filtered by the filter unit, such that the output signal of the filter unit lags behind the input signal of the filter unit. This means that: the sampled values of the digitized input voltage on which the output signal of the filter unit is based are earlier in time than the sampled values of the digitized input voltage on which the input signal of the filter unit is based. That is to say, the filter unit causes at least a time delay between the input signal and the output signal, for example due to its design. Then, the input signal and the output signal of the filter unit are compared by means of a comparator unit. Then, the comparison result provided by the comparator unit as an output signal is evaluated. Here, during the evaluation period starting with the reset of the counter unit, the comparison result provided by the comparator unit is continuously evaluated until a further state change of the comparison result is found after the first state change of the comparison result. That is to say, the evaluation of the comparison result continues until a further change in the value or state at the output of the comparator unit is found after the first change in the value or state at the output of the comparator unit. Then, the corresponding evaluation period is ended, and then the period duration and / or the frequency of the alternating voltage component of the input voltage are determined based on the current count value of the counter unit.

[0011] The main aspects of the present invention are as follows: The component cost and / or storage requirements are low for implementation. For example, for implementing the method according to the present invention, existing hardware such as the control and / or regulation unit of a switched-mode power supply can be used very simply. In addition, with this method, the frequency of the alternating voltage component of the input voltage of the switched-mode power supply can be determined in a very simple manner, so that high-level conclusions can be drawn regarding, for example, interference, phase failure, etc. of the supply voltage of the switched-mode power supply and corresponding measures can be taken. In addition, the method can in particular adapt the input signal or digitized voltage at the input of the filter unit and the output signal of the filter unit, which are compared for frequency determination, almost automatically to the time variation of the input voltage, because the filter unit is designed such that the output signal of the filter unit lags behind the input signal of the filter unit. That is to say, due to filtering, the output signal of the filter unit has at least a time delay with respect to the digitized input voltage that forms the input signal of the filter unit. In addition, the method can be used in a large input voltage range because no predefined threshold, for example, is required for evaluation, but the method can automatically and dynamically adapt to different input voltage ranges of the switched-mode power supply.

[0012] It is also advantageous that, for determining the average value of the input voltage, the sum value of the digitized input voltage summed up during the corresponding evaluation period and the current count value at the end of the corresponding evaluation period are used. Based on the sum value determined during the corresponding evaluation period, the average value of the input voltage can be calculated very simply by dividing the sum value by the current count value queried from the counter unit at the end of the corresponding evaluation period. For this sum value, the sampled values of the digitized input voltage are summed up within the sampling period using the sampling rate.

[0013] It is also advantageous that during the corresponding evaluation period, the minimum value and the maximum value of the digitized input voltage are detected. Based on the minimum value and the maximum value detected during the corresponding evaluation period, it can be very simply ascertained whether a supposed valid signal is, for example, noise. For a meaningful evaluation of the input voltage, for example, it is important that the difference between the minimum value and the maximum value of the corresponding evaluation period exceeds a predefined minimum value so that an undisturbed evaluation can be performed.

[0014] Ideally, the input voltage is reduced to a voltage range suitable for signal processing before sampling. In the case where the switched-mode power supply is powered, for example, by a single-phase or three-phase mains voltage, the rectified input voltage can be in the range of approximately 550 volts. To achieve an input voltage range that can be processed, for example, by an analog-to-digital converter and / or a microcontroller, it is reasonable to reduce the input voltage to a voltage range of approximately 3 volts for signal processing.

[0015] An advantageous implementation variant of the invention provides that the comparator unit uses hysteresis when comparing the input signal of the filter unit with the output signal of the filter unit. By using hysteresis when comparing the input signal of the filter unit with the output signal, the anti-interference safety is improved in a very simple manner. Due to this hysteresis, for example, false measurements caused by possible signal noise can be very easily prevented.

[0016] It is also advantageous that the evaluation of the comparison result of the comparator unit is ended when a pre-given maximum count value of the counter unit is reached. If, for example, no first and / or further state change is found during the evaluation period when evaluating the comparison result of the comparator unit, the evaluation of these comparison results can be very simply ended by reaching or exceeding the pre-given count value of the counter unit, for example by means of a so-called timeout. Then, the counter unit can be reset, for example, for a new evaluation period. By the counter unit reaching or exceeding the pre-given count value, it can also be ascertained, for example, that the input voltage of the switched-mode power supply is a DC voltage that hardly changes. For example, a count value is selected as the pre-given count value, and the period duration corresponding to this count value is significantly longer than the period duration of the lowest expected frequency of the alternating component of the input voltage to be evaluated.

[0017] It is also advantageous that noise suppression and / or noise reduction are performed after the digitization of the input voltage or after the sampling of the input voltage. Thereby, for example, the undesired noise in the digitized signal of the input voltage or in the digitized input voltage is reduced or prevented, and thereby an improved and more accurate evaluation result is achieved.

[0018] The solution to this task is also achieved by a system for evaluating the input voltage of a switched-mode power supply, where the input voltage has a pre-given polarity. Here, the system for performing the method according to the invention at least has the following functional units:

[0019] - An analog-digital converter for digitizing the input voltage, where the input voltage is sampled using a pre-given sampling rate;

[0020] - At least one filter unit for filtering the digitized input voltage, where the filter unit is designed such that the output signal of the filter unit lags behind the input signal of the filter unit;

[0021] - A comparator unit for comparing the input signal of the filter unit with the output signal of the filter unit;

[0022] - A counter unit for measuring the respective evaluation period, which can be reset at the start of the respective evaluation period;

[0023] - A flow sequence controller, which is implemented as a state machine and configured to:

[0024] o Start a corresponding evaluation period by at least resetting a counter unit.

[0025] o Continuously evaluate the comparison results provided by a comparator unit as output signals until a further state change of these comparison results is detected after the first state change of these comparison results.

[0026] o End the corresponding evaluation period after a further output state change of the comparator unit and query at least one current count value of the counter unit to determine the period duration and / or frequency of the alternating voltage component of the input voltage; and - A timer unit, which pre-gives the time control and the sampling rate of an analog-to-digital converter via a clock signal.

[0027] The advantage of the proposed system is that the system can be implemented for a switching mode power supply very simply and without high costs (such as additional components, storage requirements). Thereby, with this system, the input voltage of the switching mode power supply, especially the frequency of the alternating voltage component, can be evaluated in a simple manner. In this way, disturbances in the supply voltage of the switching mode power supply, such as a phase failure in the case of a three-phase supply voltage, can be quickly and simply identified. Thereby, for example, measures can be taken quickly and, for example, the operator can be informed of the disturbance.

[0028] It is also advantageous to provide an integrator unit for summing the digitized input voltage during the corresponding evaluation period, wherein the integrator unit can be reset at the start of the corresponding evaluation period. With the help of the integrator unit, the sampled values of the digitized input voltage can be very simply summed during the evaluation period, for example, within the sampling clock. Then, at the end of the evaluation period, the sum value of the integrator unit can be queried by the flow sequence controller, and based on this, for example, the average value of the input voltage of the switching mode power supply can be determined using the count value at the end of the evaluation period. Knowing the average value of the input voltage has the following advantages: It can be identified whether the switching mode power supply is operating within the optimal voltage range, for example, or whether there are deviations and corresponding measures must be taken.

[0029] Ideally, a detector unit is also provided for detecting the peak value of the digitized input voltage during the corresponding evaluation period, wherein the detector unit can be reset at the start of the corresponding evaluation period. With this detector unit, the minimum and maximum values of the input voltage during the corresponding evaluation period can be determined in a simple manner, and for example, the minimum value and the maximum value can be queried and evaluated by the flow sequence controller at the end of the evaluation period.

[0030] Suitably, a voltage divider is arranged on the input side of the analog-to-digital converter, through which the input voltage can be reduced to a voltage range suitable for signal processing. Through corresponding parameter design, the rectified input voltage of a switched-mode power supply powered by a single-phase or three-phase mains voltage can reach, for example, the following voltage level, which can be used for signal processing by, for example, electronic hardware (such as programmable logic, microcontroller).

[0031] A special implementation variant of the system according to the invention provides that another filter unit is provided, which is arranged between the output of the analog-to-digital converter and the input of the filter unit. Ideally, this filter unit is used to filter the digitized input voltage in order to, for example, reduce unwanted noise and thereby make the evaluation of the input voltage more accurate. The filter unit can, for example, be implemented as a first-order low-pass filter and can, for example, have a filter time constant that is greater than or equal to the sampling rate of the analog-to-digital converter.

[0032] Ideally, the system is implemented by means of a microcontroller or programmable logic. Here, for example, a microcontroller that already exists for controlling or regulating the switched-mode power supply can be used for the system. Here, for example, the analog-to-digital converter can be integrated into the microcontroller. However, alternatively, there is also the possibility that the analog-to-digital converter is implemented as a separate component that provides the sampled input voltage in the form of a sequence of sampled values. Description of the Drawings

[0033] Subsequently, the invention is explained exemplarily with reference to the accompanying drawings. Herein:

[0034] Figure 1 A realization variant of a system for evaluating the input voltage of a switched-mode power supply is shown schematically and exemplarily;

[0035] Figure 2a schematically shows an exemplary flow of a method for evaluating the input voltage of a switched-mode power supply;

[0036] Figure 2b schematically shows an exemplary flow of the evaluation of the comparison result of a comparator unit;

[0037] Figure 3 Another realization variant of a system for evaluating the input voltage of a switched-mode power supply is shown schematically and exemplarily. Detailed Description of the Invention

[0038] Figure 1 Schematically shows the input voltage U for evaluating a switched-mode power supply rectExemplary implementation variants of the system, where the system has functional units that can be implemented as hardware and / or software units, and where the functional units of the system implemented as software units can be implemented, for example, in a microcontroller. Alternatively, the system can be implemented at least by means of programmable logic.

[0039] Here, the switched-mode power supply is supplied, for example, by a supply voltage U N . The supply voltage U N can be, for example, a single-phase or three-phase mains voltage from the power supply network. The supply voltage U N is fed to the input stage GL of the switched-mode power supply, where the input stage GL can be designed, for example, as a 2-pulse or 6-pulse rectifier unit GL depending on the supply voltage U N . By means of the rectifier unit GL, the supply voltage UN is rectified and the input voltage U rect of the switched-mode power supply is generated. The input voltage U rect relative to the reference potential MP (for example 0 volts) has a defined or distinct polarity. That is to say, this polarity does not change during the time-varying course of the input voltage U rect . However, the amplitude of the input voltage U rect has a time-varying component - for example due to the so-called ripple, which is formed, for example, due to the rectification of the supply voltage U N by the rectifier unit GL.

[0040] Subsequently, the input voltage U rect of the switched-mode power supply is fed to a voltage divider, which consists, for example, of resistors R1 and R2. The voltage divider brings the input voltage U N which varies, for example, in the range of approximately 550 volts when the supply or mains voltage U rect is, for example, 400 volts, into a voltage range (for example approximately 3 to 4 volts) that can be used or processed in a signal-technical manner for carrying out the method according to the invention. By means of the voltage divider or the ratio of the resistors R1 and R2, the input voltage U rect is reduced to an input voltage U r having a signal-processable magnitude (for example 3.3 volts).

[0041] The reduced input voltage U r is fed to an analog-to-digital converter AD, which performs the digitization or sampling of the reduced input voltage U r . The analog-to-digital converter AD can be implemented, for example, as a separate component or integrated into a microcontroller, which carries out the method according to the invention. Furthermore, for the correct operation of the analog-to-digital converter AD, for example, it may be necessary, for the sake of simplicity not shown in Figure 1The capacitor shown in the figure is connected to the input of an analog - to - digital converter AD. Here, the capacitor should be selected such that the signal form of the input voltage U r is affected as little as possible. The analog - to - digital converter AD uses a sampling rate or sampling frequency to sample the analog input voltage U r . Then, the analog - to - digital converter AD provides the sampled or digitized input voltage U r_dig , for example, in the form of a time series of sampled values.

[0042] The sampling rate or clock for sampling the reduced input voltage U r is provided by the output signal or clock signal CLK of a clock generator unit or a timer unit TI. Thereby, the timer unit TI undertakes the time control of the analog - to - digital converter AD through its output signal or through the clock signal CLK, but also undertakes the time control of other functional units of the system according to the invention. That is to say, the corresponding output signals of these functional units are always available at the corresponding outputs of the functional units at the clock CLK of the timer unit TI. The frequency of the clock signal CLK can be freely selected (for example, 10 kHz). However, since the clock signal CLK also constitutes the sampling rate of the analog - to - digital converter AD, it should be noted that: the sampling rate or sampling frequency and thus the clock signal CLK are significantly higher than the expected frequency of the alternating voltage component or ripple of the input voltage U rect or the reduced input voltage U r . Thereby, the period duration of the sampling frequency (for example, 100 μs) is also significantly shorter than the period duration of the ripple superimposed on the input voltage U rect of the switched - mode power supply or the reduced input voltage U r .

[0043] Now, the digitized input voltage U r_dig is led to a filter unit PT. The filter unit PT is implemented, for example, as a first - order digital low - pass filter unit, which has a gain P (for example, P = 1) and a time constant T. Here, the filtering time constant T is, for example, at least greater than or equal to the period duration of the sampling rate CLK or the period duration of the clock signal CLK. The filtering time constant T can be, for example, 4 times the period duration of the sampling rate or the clock signal CLK or, ideally, 16 times. Thereby, the filter unit PT has a filtering effect and a transit time for the filtered output signal U r_pt , whereby, for example, the output signal U r_pt of the filter unit PT lags behind or at least has a time delay with respect to the input signal U r_dig of the filter unit PT. That is to say, the digitized input voltage U on which the output signal U r_pt of the filter unit PT is basedr_dig The sampled value is temporally prior to the digitized input voltage U r_dig The following sampled value, in the case of the same clock signal CLK of the timer unit TI or at the same clock edge of the clock signal CLK, serves as the input signal U of the filter unit PT r_dig Exists at the input of the filter unit PT

[0044] Subsequently, the input signal U of the filter unit PT r_dig And the output signal U of the filter unit PT r_pt Are fed to the comparator unit COMP. Depending on whether the input signal U of the filter unit PT r_dig Is greater than or less than the output signal U of the filter unit PT r_pt , the comparison result AW at the output of the comparator unit COMP can assume different values or states. Here, for example, when the input signal U of the filter unit PT r_dig Is less than the output signal U of the filter unit PT r_pt , the comparison result AW can assume a first value or state. If the input signal U of the filter unit PT r_dig Is greater than the output signal U of the filter unit PT r_pt , then, for example, the comparison result AW at the output of the comparator unit COMP assumes a second value or state

[0045] Regarding these two signals U of the filter unit PT r_dig , U r_pt The comparison of which signal is larger or smaller can be performed by the comparator unit COMP, for example, without hysteresis H or with hysteresis H. In the case of using hysteresis H, for example, possible signal noise can be reduced or false measurements can be prevented. Here, the hysteresis H can be added to or subtracted from the input signal U of the filter unit PT r_dig And the output signal U r_pt Or from this input signal and this output signal. Thereby, feedforward or positive feedback is achieved, which makes the comparison result AW of the comparator unit COMP more stable

[0046] The comparison result AW of the comparator unit COMP is forwarded as the corresponding current value or state at the output of the comparator unit COMP to the flow sequence controller AS. The flow sequence controller controls the process of evaluating the input voltage U rect Or the reduced input voltage U r , and thereby can determine the duration of the corresponding evaluation period and accordingly determine the input voltage U rect Or U rThe frequency of the superimposed alternating voltage component or ripple. To this end, the flow sequence controller is designed, for example, as a state machine or a so-called StateMachine, which can be transformed from the current first state to a new second state when the comparison result AW at the output of the comparator unit COMP changes for the first time or the value or state at the output of the comparator unit COMP changes for the first time. When the comparison result AW at the output of the comparator unit COMP changes again, the flow sequence controller AS can be transformed from the second state to the first state via the third state or the calculation state and the reset step. The detailed process of evaluating the comparison result AW of the comparator unit COMP by the flow sequence controller AS is shown by way of example in FIG. 2b and described in more detail by way of example based on the figure.

[0047] The signals of the counter unit CO, the integrator unit INT and the detector unit DET are also provided to the flow sequence controller AS and it can reset them, for example, by means of a reset signal r at the beginning of a corresponding evaluation period.

[0048] Here, the counter unit CO counts the pulses of the clock signal CLK of the timer unit TI. The counter unit CO can be started by the flow sequence controller AS at the beginning of the corresponding evaluation period with the help of the reset signal r. At the end of the corresponding evaluation period, the counter unit CO provides the count value CO_W or the counter reading CO_W to the flow sequence controller AS, from which the duration of the corresponding evaluation period can be derived. Then, the counter unit CO can be reset again with the help of the reset signal r of the flow sequence controller AS for a new evaluation period.

[0049] The integrator unit INT converts the digitized input voltage U r_dig At the end of the corresponding evaluation period, the integrator unit INT can provide the digital input voltage U to the flow sequence controller AS. r_dig The sum of the values ​​U r_sum The flow sequence controller AS can, for example, deduce the input voltage U from the sum value. rect The integrator unit INT can likewise be reset at the beginning of each new evaluation period using the reset signal r. The integrator unit INT is also time-controlled by means of the clock signal CLK of the timer unit TI.

[0050] During the corresponding evaluation period, the detector unit DET detects the digitized input voltage U r_dig The maximum value U r_max and the digitized input voltage U r_dig The minimum value of U r_minAt the end of the respective evaluation period, these values U are provided to the flow sequence controller AS. r_max and U r_min The detector unit DET can equally be reset at the start of each new evaluation period by means of the reset signal r. In addition, the detector unit DET is also time-controlled by means of the clock signal CLK of the timer unit TI.

[0051] Figure 2a schematically and exemplarily shows the flow of a method for evaluating the input voltage U of a switched-mode power supply. rect Here, the input voltage U rect has a definite or defined polarity, but an amplitude that varies over time. Before the first step 101 of the method, the input voltage U rect can be brought to a voltage range suitable for signal processing by means of, for example, a microcontroller by means of a voltage divider R1, R2. The input voltage U of the switched-mode power supply rect is, for example, reduced to the input voltage U r .

[0052] In the first step 101 or in the digitization step 101, the reduced input voltage U r is converted by an analog-to-digital converter AD into a digitized input voltage U r_dig . For this purpose, the input voltage U r is sampled using, for example, a sampling rate or sampling frequency pre-given by the clock signal CLK of the timer unit TI. Subsequently, the sampled or digitized input voltage U r_dig is provided at the output of the analog-to-digital converter AD, for example, in the form of a time series of sampling values.

[0053] Subsequently, in the filtering step 102, the digitized input voltage U r_dig is fed to the filter unit PT for filtering. Here, the filter unit PT is designed such that the output signal U r_pt of the filter unit PT has at least a time delay with respect to the input signal formed by the digitized input voltage U r_dig . That is to say, the output signal U r_pt of the filter unit PT lags behind the input signal U r_dig of the filter unit PT, and the sampling values of the digitized input voltage U r_dig on which this output signal is based are earlier in time than the sampling values of the digitized input voltage U r_dig which are present at the input of the filter unit PT as the input signal in the case of the same clock signal CLK of the timer unit TI.

[0054] The input signal U r_dig and the output signal U of the filter unit PTr_pt are fed to comparator unit COMP and compared with each other in comparison step 103. Depending on whether the input signal U of filter unit PT r_dig or the output signal U r_pt is greater, the comparison result AW at the output of comparator unit COMP can assume different values or states, for example. The comparison result AW determined in comparison step 103 is then forwarded to stream order controller AS.

[0055] Subsequently, in evaluation step 104, stream order controller AS evaluates the comparison result AW provided by comparator unit COMP. To evaluate the comparison result AW continuously provided by comparator unit COMP, stream order controller AS is designed, for example, as a state machine or a so-called State Machine.

[0056] The flow of the evaluation by stream order controller AS of the comparison result provided by comparator unit COMP is schematically and exemplarily shown in FIG. 2b.

[0057] To start the evaluation period, stream order controller AS resets counter unit CO to an initial value (e.g., value 0) in reset step 1041 by means of reset signal r. Counter unit CO counts the pulses of the clock signal CLK of timer unit TI during the respective evaluation period. Additionally, integrator unit INT and detector unit DET can also be reset to their respective initial values (e.g., value 0), and thereby the summation of the digitized input voltage U r_dig can be started during the respective evaluation period and the minimum and maximum values U r_dig of the digitized input voltage U r_min 、U r_max can be started during the respective evaluation period. Subsequently, stream order controller AS changes, for example, to the first state after reset step 1041, for example.

[0058] In a first check step 1042, stream order controller checks whether there is a first state change in the comparison result AW continuously provided by comparator unit COMP. That is, stream order controller AS evaluates whether the value or state at the output of comparator unit COMP changes. As long as comparator unit COMP provides an unchanged comparison result AW (e.g., the input signal U of filter unit PT r_dig remains less than the output signal U r_pt or the input signal U of filter unit PT r_dig remains greater than the output signal U r_pt ) and thereby the current value or state at the output of comparator unit COMP remains unchanged, stream order controller AS also remains in the first state and continues to execute the first check step 1042.

[0059] However, if it is found in the first checking step 1042 that the value or state at the output of the comparator unit COMP changes for the first time, the flow sequence controller AS changes from the first state to the second state and changes from the first checking step 1042 to the second checking step 1043. That is to say, if, for example, due to the input signal U of the filter unit PT r_dig becomes greater than the output signal U r_pt or due to the input signal U of the filter unit PT r_dig becomes less than the output signal U r_pt so that the comparison result AW at the output of the comparator unit COMP changes, the current state of the flow sequence controller AS also changes from the first state to the second state.

[0060] Next, in the second checking step 1043, it is rechecked whether the comparison result AW continuously provided by the comparator unit COMP changes again. As long as the flow sequence controller AS does not find a change in the value or state at the output of the comparator unit COMP based on the provided comparison result AW, the flow sequence controller AS remains in the second state and continues to execute the second checking step 1043. That is to say, as long as, for example, the input signal U of the filter unit PT r_dig remains greater than the output signal U of the filter unit PT r_pt or the input signal U of the filter unit PT r_dig remains less than the output signal U r_pt , the output controller AS remains in the second state and waits for the comparison result AW to change again.

[0061] If in the second checking step 1043, due to, for example, the input signal U of the filter unit PT r_dig becomes less than the output signal U of the filter unit PT again r_pt or due to the input signal U of the filter unit PT r_dig becomes greater than the output signal U again r_pt so that a second or further change in the comparison result AW of the comparator unit COMP is found, the flow sequence controller changes to the third state or to the calculation state, and then the calculation step 1044 is executed in this third state or this calculation state.

[0062] Next, in the calculation step 1044, the corresponding evaluation period is ended, and the flow sequence controller AS queries, for example, the current count value CO_W of the counter unit CO. In addition, the current sum value U of the integrator unit INT r_sum as well as the minimum value U of the digitized input voltage U ascertained by the detector unit DET during the corresponding evaluation period r_dig can also be usedr_min and the maximum value U r_max is transmitted to the sequence controller AS.

[0063] Furthermore, in calculation step 1044, based on the count value CO_W queried for the corresponding evaluation period, the frequency of the clock signal CLK, and the digitized input voltage U r_dig transmitted for the corresponding evaluation period, the sum value U r_sum of which, the frequency of the alternating voltage component and the average value of the input voltage U rect can be derived. To determine the frequency of the alternating voltage component of the input voltage U rect , for example, the frequency of the clock signal CLK is divided by the count value CO_W determined for the corresponding evaluation period. To determine the average value of the input voltage U rect , for example, the digitized input voltage U r_dig determined within the corresponding evaluation period and the sum value U r_sum thereof can be divided by the count value CO_W determined for the corresponding evaluation period.

[0064] After calculation step 1044, reset step 1041 is executed again. Here, the counter unit CO, the integrator unit INT, and the detector unit DET can be reset by the sequence controller AS again to the corresponding initial values by means of the reset signal r for the next evaluation period. With reset step 1041, the next evaluation period is started and the sequence controller is again in the first state in order to again evaluate, for example, the next comparison result AW of the comparator unit COMP by means of the first and second check steps 1042, 1043.

[0065] If, for example, no change in the comparison result AW of the comparator unit COMP is detected during the first check step 1042 and / or during the second check step 1043, the method can be ended when the value of the counter unit CO reaches or exceeds a pre-given count value. That is, the ongoing evaluation period is ended or interrupted when the pre-given count value is reached or exceeded. Here, for example, the sequence controller AS can again be placed in the first state and the counter unit CO, the integrator unit INT, and the detector unit DET can be reset to the corresponding pre-given initial values.

[0066] Figure 3 shows another implementation variant of a system for evaluating the input voltage U rect of a switched-mode power supply, with which the method according to the invention can be carried out. Here, the input voltage U rect of the switched-mode power supply is again reduced by means of a voltage divider R1, R2 to an input voltage U r with a signal-processable magnitude (for example 3.3 volts). The reduced input voltage U ris fed again to an analog - to - digital converter AD, which digitizes the reduced input voltage U using a sampling signal or a clock signal CLK of a timer unit TI. r The digitized input voltage U r_dig - different from the implementation variant shown in Figure 1 - is first led to another filter unit PT1, which is connected on the input side to the analog - to - digital converter AD. On the output side, the filter unit PT is connected to this other filter unit PT1, where now the output signal U r_pt1 of this other filter unit PT1 forms the input signal of the filter unit PT. This other filter unit PT1 is mainly used to suppress or reduce noise in the digitized input voltage U r_dig . This other filter unit PT1 can for example also be implemented as a first - order low - pass filter and has a gain P (e.g., P = 1). This other filter unit PT1 also has a filtering time constant T, which is for example greater than or equal to the period duration of the sampling rate CLK or the period duration of the clock signal CLK.

[0067] Then, the output signal U r_pt1 of this other filter unit PT1, which now forms the input signal of the filter unit PT, and the output signal U r_pt of the filter unit PT are fed to a comparator unit COMP for comparison. Then, these two signals U r_pt1 , U r_pt can be compared with each other again, with or without hysteresis H.

[0068] Then, the comparator unit COMP provides the comparison result AW again to a sequence controller AS, which then controls the evaluation of these comparison results again - as described with reference to Figure 2b. The implementation variant shown in Figure 3 also has a counter unit CO, an integrator unit INT, and a detector unit DET, which can also be time - controlled by a timing signal CLK of the timer unit TI and are reset by the sequence controller AS via a reset signal r. However, in the implementation variant shown in Figure 3 , the digitized input voltage U r_pt1 filtered by this other filter unit PT1 is fed as an input signal to the integrator unit INT and the detector unit DET in order to obtain improved output values U r_sum , U r_min , U r_max at the end of the respective evaluation period.

Claims

1. A method for evaluating the input voltage (U rect ) of a switched-mode power supply, wherein the input voltage (U rect ) has a pre-given polarity, characterized in that, The input voltage (U rect ) is digitized (101) by sampling using a pre-given sampling rate; the digitized input voltage (U r_dig ) is filtered (102) as an input signal of a filter unit (PT) such that the output signal (U r_pt ) of the filter unit (PT) lags behind the input signal (U r_dig ) of the filter unit (PT); the input signal (U r_dig ) of the filter unit (PT) is compared (103) with the output signal (U r_pt ) of the filter unit (PT) by means of a comparator unit (COMP); and the comparison result (AW) provided by the comparator unit is evaluated (104), wherein during a corresponding evaluation period starting (1041) by resetting a counter unit (CO), the comparison result provided by the comparator unit (COMP) is continuously evaluated until a further state change of the comparison result (AW) is detected (1042, 1043) after a first state change of the comparison result (AW), and wherein then the corresponding evaluation period is ended and the period duration and / or frequency of the alternating voltage component of the input voltage (U rect ) is determined (1044) based on the current count value (CO_W) of the counter unit (CO).

2. The method according to claim 1, characterized in that, In order to determine the mean value of the input voltage (U rect ), the sum value (U r_dig ) of the digitized input voltage (U r_sum ) summed up in the corresponding evaluation period using (1044) and the current count value (CO_W) at the end of the corresponding evaluation period are used.

3. The method according to claim 1 or 2, characterized in that, During a corresponding evaluation period, the minimum value (U r_dig ) and the maximum value (U r_min ) of the digitized input voltage (U r_max ) are detected (1044).

4. The method according to claim 1 or 2, characterized in that, The input voltage (U rect ) is reduced to a voltage range suitable for signal processing before the sampling.

5. The method according to claim 1 or 2, characterized in that The comparator unit (COMP) uses hysteresis (H) (103) when comparing the input signal (U r_dig ) of the filter unit (PT) with the output signal (U r_pt ) of the filter unit (PT).

6. The method according to claim 1 or 2, characterized in that, The evaluation of the comparison result (AW) of the comparator unit (COMP) ends (1042, 1043) when a pre-given maximum count value (CO_W) of the counter unit (CO) is reached.

7. The method according to claim 1 or 2, characterized in that After digitization of the input voltage (U rect ), noise reduction and / or noise suppression is performed.

8. A system for evaluating the input voltage (U rect ) of a switched-mode power supply, wherein the input voltage (U rect ) has a pre-given polarity, characterized in that, The system has at least the following functional units for performing the method according to any one of claims 1 to 7: - Analog - to - Digital Converter (AD) for digitizing the input voltage (U rect ), where the input voltage (U rect ) is sampled using a pre - given sampling rate (CLK); - At least one filter unit (PT) for filtering a digitized input voltage (U r_dig ) serving as an input signal, wherein the filter unit (PT) is designed such that an output signal (U r_pt ) of the filter unit (PT) lags behind an input signal (U r_dig ) of the filter unit (PT); - A comparator unit (COMP) for comparing the input signal (U r_dig ) of the filter unit (PT) with the output signal (U r_pt ) of the filter unit (PT); - A counter unit (CO) for measuring a respective evaluation period, which can be reset at the start of the respective evaluation period; - A flow sequence controller (AS), which is set up to: o Start the respective evaluation period by at least resetting the counter unit (CO), o Continuously evaluate the comparison result (AW) provided by the comparator unit (COMP) until a further state change of the comparison result (AW) is detected after the first state change of the comparison result (AW), o End the respective evaluation period after a further output state change of the comparator unit (COMP) and query at least one current count value (CO_W) of the counter unit (CO) in order to determine the period duration and / or the frequency of the alternating voltage component of the input voltage; and - A timer unit (TI), which pre-gives the time control and the sampling rate (CLK) of the analog-to-digital converter (AD) via a clock signal (CLK).

9. The system according to claim 8, wherein An integrator unit (INT) is also provided for summing the digitized input voltage (U r_dig ) during a respective evaluation period, wherein the integrator unit (INT) can be reset at the start of the respective evaluation period.

10. The system according to claim 8 or 9, characterized in that A detector unit (DET) is also provided for detecting the peak value (U r_dig ) of the digitized input voltage (U r_min , U r_max ) during a respective evaluation period, wherein the detector unit (DET) can be reset at the start of the respective evaluation period.

11. The system according to claim 8 or 9, characterized in that, A voltage divider (R1, R2) is arranged on the input side of the analog-digital converter (AD), and the input voltage (U rect ) can be reduced to a voltage range suitable for signal processing by means of the voltage divider.

12. The system according to claim 8 or 9, wherein Another filter unit (PT1) is also provided, which is arranged between the output of the analog-to-digital converter (AD) and the input of the filter unit (PT).

13. The system according to claim 8 or 9, characterized in that, The system can be implemented by means of a microcontroller or programmable logic.

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