Voltage measurement method

Abstract

To provide a voltage measurement method which enables accurate voltage measurement even when a range of changes in a negative voltage is smaller than a range of changes in a positive voltage in absolute terms.SOLUTION: A voltage measurement method is disclosed, comprising: converting a first voltage V1 of a measurement target 10, whose range of changes in a negative voltage is smaller than a range of changes in a positive voltage in absolute terms, into a second voltage V2 using a potential adjustment circuit 20 configured to conduct a negative voltage and convert a positive voltage into a reference potential; and inputting the second voltage to a measurement device 30 to measured the voltage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a voltage measurement method. [Background technology]

[0002] When designing a circuit, the voltage of the circuit during operation may be measured to analyze its operation or to investigate the cause of a malfunction.

[0003] One example of the circuit is an upper arm drive circuit as described in Patent Document 1. The abstract of Patent Document 1 states that "in a power conversion device having a bridge circuit composed of upper and lower arms, an upper arm drive circuit is provided that is capable of stably controlling the upper arm without malfunctioning even when the output of the power conversion device becomes negative potential."

[0004] For example, taking the example of a circuit capable of preventing malfunction due to negative voltages, as described in Patent Document 1, when designing this circuit, there is a demand to measure and analyze this negative voltage in order to investigate the cause of the malfunction and to use the result as a reference for designing circuits that can prevent malfunction due to negative voltages. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-146525 Summary of the Invention [Problem to be solved by the invention]

[0006] Fig. 4 is a circuit diagram for explaining the problems with the conventional voltage measurement method. Fig. 5 is a waveform diagram for explaining the problems with the conventional voltage measurement method. In Fig. 5, the horizontal axis is time, and the vertical axis is, from the top, the signal level of the gate signal SG, the voltage of the first voltage V1 displayed at 50 V / div, and the voltage near the negative voltage of the first voltage V1 displayed at 2 V / div.

[0007] As shown in FIG. 4, assume that the measurement object 10 is a half-bridge circuit 11 connected between a DC power supply E and a reference potential GND, and consider a case in which a first voltage V1, which is the output of the half-bridge circuit 11, is input to a measuring device 30 such as an oscilloscope to measure the voltage.

[0008] In the half-bridge circuit 11, an upper-arm switching element SW1 and a lower-arm switching element SW2 are connected in series, an upper-arm freewheel diode D1 is connected in anti-parallel to the upper-arm switching element SW1, and a lower-arm freewheel diode D2 is connected in anti-parallel to the lower-arm switching element SW2. A load 12 having an inductance L1 is connected between a first node N1, which is the output of the half-bridge circuit 11, and a reference potential GND, and a parasitic inductance L2 is present between the half-bridge circuit 11 and the reference potential GND.

[0009] When an H-level gate signal SG is input to the gate of the upper arm switching element SW1 and the upper arm switching element SW1 is turned on, the current path becomes like the current path i1 when SW1 is on as shown in Figure 4, and the first voltage V1, which is the voltage of the first node N1, becomes a positive voltage of, for example, several hundred volts, which is approximately the same as the power supply voltage E as shown in Figure 5.

[0010] Thereafter, when an L-level gate signal SG is input to the gate of the upper arm switching element SW1 to turn off the upper arm switching element SW1, the current path becomes like the current path i2 when SW1 is off as shown in FIG. 4, and the first voltage V1, which is the voltage of the first node N1, becomes a negative voltage of, for example, negative several volts to negative tens of volts as shown in FIG. 5.

[0011] However, as shown in Fig. 5, the absolute value of the negative voltage of the first voltage V1 is very small compared to the absolute value of the positive voltage, so when the measurement range of the measuring device 30 is set large so that the positive voltage portion can be measured (for example, when the resolution is 50V / div), the behavior of the negative voltage portion cannot be measured accurately. Also, when the measurement range of the measuring device 30 is set small so that the negative voltage portion can be measured (for example, when the resolution is 2V / div), the positive voltage portion falls outside the measurement range, resulting in a problem of range overflow. Furthermore, when the range overflows, the protection circuit of the measuring device 30 is activated, so there is a problem that the negative voltage waveform does not show a normal value due to the influence of the protection circuit of the measuring device 30.

[0012] An object of the present invention is to provide a voltage measurement method capable of measuring voltages with high accuracy even when the negative voltage changes within a range smaller in absolute value than the positive voltage. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems, the voltage measurement method of the present invention is characterized in that a first voltage from a measurement object, which changes within a range in which the absolute value of negative voltages is smaller than that of positive voltages, is converted into a second voltage using a potential adjustment circuit that is conductive when the first voltage is negative and converts the first voltage to a reference potential when the first voltage is positive, and the second voltage is input into a measurement device to measure the voltage. Effect of the Invention

[0014] According to the voltage measuring method of the present invention, the voltage can be measured with high accuracy even when the negative voltage changes within a range smaller in absolute value than the positive voltage. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a functional block diagram for explaining a voltage measuring method according to an embodiment. [Diagram 2]FIG. 4 is a circuit diagram for explaining a voltage measuring method according to the embodiment. [Diagram 3] FIG. 4 is a waveform diagram for explaining a voltage measuring method according to an embodiment. [Figure 4] FIG. 1 is a circuit diagram for explaining a problem with a conventional voltage measurement method. [Diagram 5] 11 is a waveform diagram for explaining a problem with a conventional voltage measurement method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing and each embodiment, the same or similar components are designated by the same reference numerals, and duplicated explanations will be omitted.

[0017] FIG. 1 is a functional block diagram for explaining a voltage measuring method according to an embodiment.

[0018] In the voltage measurement method of the embodiment, a first voltage V1 from a measurement object 10, which varies within a range in which the absolute value of negative voltages is smaller than that of positive voltages, is converted into a second voltage V2 using a potential adjustment circuit 20 that is conductive when the voltage is negative and converts the voltage to a reference potential when the voltage is positive, and the second voltage is input to a measurement device 30 to measure the voltage.

[0019] Fig. 2 is a circuit diagram for explaining a voltage measurement method of the embodiment. Fig. 3 is a waveform diagram for explaining a voltage measurement method of the embodiment. In Fig. 3, the horizontal axis is time, and the vertical axis is, from the top, the signal level of the gate signal SG, the voltage of the first voltage V1 displayed at 50V / div, and the voltage of the second voltage V2 displayed at 2V / div near the negative voltage.

[0020] In this embodiment, as an example, a case will be described in which the measurement target 10 outputting the first voltage V1 is a half-bridge circuit 11. However, the measurement target 10 is not limited to this, and the voltage measurement method of the embodiment may be applied to a circuit with a wide dynamic range in which a negative low voltage occurs after a positive high voltage, such as an AC-DC converter, a half-wave rectifier circuit, or a switching regulator. For example, in a half-wave rectifier circuit, a negative low voltage occurs after a positive high voltage during recovery.

[0021] In this embodiment, as shown in FIG. 2, the measurement object 10 is assumed to be a half-bridge circuit 11 connected between a DC power supply E and a reference potential GND, and a first voltage V1 which is the output of the half-bridge circuit 11 is converted into a second voltage V2 using a potential adjustment circuit 20, and the second voltage V2 is input to a measuring device 30 to measure the voltage.

[0022] The half-bridge circuit 11 has an upper arm switching element SW1 and a lower arm switching element SW2 connected in series, an upper arm freewheel diode D1 connected in inverse parallel to the upper arm switching element SW1, and a lower arm freewheel diode D2 connected in inverse parallel to the lower arm switching element SW2.

[0023] The upper arm switching element SW1 of the half-bridge circuit 11 is connected to a DC power supply E. The DC power supply E is a high-voltage power supply of, for example, several hundred volts.

[0024] The lower arm switching element SW2 of the half-bridge circuit 11 is connected to a reference potential GND. The reference potential GND is, for example, a ground potential, and is set to 0 V in this embodiment.

[0025] The load 12 is connected between a first node N1, which is an output of the half-bridge circuit 11 drawn between the upper arm switching element SW1 and the lower arm switching element SW2, and a reference potential GND. The load 12 has an inductance L1. Although an inductive load is assumed here as the load 12, even a resistive load will have an inductance L1 if it has a parasitic inductance.

[0026] In addition, a parasitic inductance L2 exists between the half-bridge circuit 11 and the reference potential GND.

[0027] The potential adjustment circuit 20 includes a diode D having a cathode connected to an input side to which a first voltage V1 is input and an anode connected to an output side to which a second voltage V2 is output, and a resistor R connected between the anode of the diode D and a reference potential GND. The second voltage V2 at the second node N2 is output and input to the measuring device 30. Note that the configuration of the potential adjustment circuit 20 shown in FIG. 2 is an example, and is not limited to this. In this embodiment, a high-voltage diode capable of withstanding the positive voltage of the first voltage V1, which is a high voltage, is used as the diode D.

[0028] As the measuring device 30, for example, an oscilloscope or the like can be used.

[0029] Here, when an H-level gate signal SG is input to the gate of the upper-arm switching element SW1 to turn it on, an L-level gate signal (not shown) is input to the lower-arm switching element SW2 to turn it off. The current path at this time is the current path i1 when SW1 is on shown in Fig. 2, passing through the upper-arm switching element SW1, the first node N1, and the inductance L1 toward the reference potential GND. The first voltage V1, which is the voltage of the first node N1 at this time, is approximately the same as the power supply voltage E, for example a positive voltage of several hundred volts, as shown in Fig. 3.

[0030] At this time, in the potential adjustment circuit 20, the cathode side of the diode D has a higher potential than the anode side, so the diode D is in a non-conducting state, and the cathode side of the diode D is at the first voltage V1, which is a positive voltage, and the anode side of the diode D is at the reference potential GND via the resistor R. Therefore, as shown in Fig. 3, the second voltage V2 is at 0V, which is the reference potential GND.

[0031] After that, the gate signal SG of the L level is input to the gate of the upper arm switching element SW1, and the upper arm switching element SW1 is turned off. At this time, a loop of a return current is formed, which returns to the inductance L1 via the inductance L1, the parasitic inductance L2, the lower arm return diode D2, and the first node N1, as shown in FIG. 2, when SW1 is off. This return current is a current that flows because the inductance L1 tries to maintain the current that flowed when the upper arm switching element SW1 was on even when the upper arm switching element SW1 is turned off. In addition, a new current flows in the parasitic inductance L2, but since one side of the parasitic inductance L2 is fixed to the reference potential GND, the other side becomes a negative voltage. As a result, the first voltage V1, which is the voltage of the first node N1, becomes a negative voltage of, for example, minus several volts to minus several tens of volts, as shown in FIG. 3.

[0032] At this time, in the potential adjustment circuit 20, the cathode side of diode D has a lower potential than the anode side, so diode D is conductive and current flows via resistor R and diode D as shown in current path i2 when SW1 is off in Fig. 2. The cathode side of diode D is at the first voltage V1, which is a negative voltage, and the anode side of diode D is at the sum of the first voltage V1 and the forward voltage of diode D. Therefore, as shown in Fig. 3, the second voltage V2 is approximately the same as the first voltage V1 (strictly speaking, it is the sum of the first voltage V1 and the forward voltage of diode D).

[0033] Since the absolute value of the negative voltage of the first voltage V1 is very small compared to the absolute value of the positive voltage, when the first voltage V1 is directly input into the measuring device 30 to measure the voltage as in the conventional method, it is necessary to set the measurement range of the measuring device 30 large so that the positive voltage portion can be measured, which poses the problem that the behavior of the negative voltage portion cannot be measured accurately.

[0034] In contrast, according to this embodiment, the potential adjustment circuit 20 converts the first voltage V1 into the second voltage V2, so that the second voltage V2 becomes the reference potential GND when the first voltage V1 is a positive voltage, and becomes approximately the same as the first voltage V1 when the first voltage V1 is a negative voltage, as shown in FIG. 3. Therefore, there is no need to set the measurement range of the measuring device 30 large so that the positive voltage portion can be measured, and the measurement range can be set small when measuring a negative voltage, so that the negative voltage can be measured with high accuracy.

[0035] When measuring a positive voltage, the first voltage V1 may be input to the measuring device 30 and the voltage may be measured.

[0036] Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations described in the embodiments, and various modifications are possible within the scope of the technical concept of the present invention. In addition, some or all of the configurations described in each embodiment may be combined and applied. [Explanation of symbols]

[0037] 10 Measurement Object 11 Half-bridge circuit 12 Load 20 Potential adjustment circuit 30 Measuring Equipment V1 First voltage V2 Second voltage N1 First node N2 Second node D Diode R resistance GND Reference potential SW1 Upper arm switching element SW2 Lower arm switching element D1 Upper arm freewheel diode D2 Lower arm freewheel diode L1 inductance L2 Parasitic inductance E DC power supply i1 Current path when SW1 is on i2 Current path when SW1 is off SG Gate signal

Claims

1. A voltage measurement method comprising: converting a first voltage from an object to be measured, in which the absolute value of the negative voltage varies within a range smaller than that of the positive voltage, into a second voltage using a potential adjustment circuit that is conductive when the first voltage is a negative voltage and converts the first voltage to a reference potential when the first voltage is a positive voltage; and inputting the second voltage into a measurement device to measure the voltage.

2. In claim 1, a potential adjustment circuit that adjusts a voltage from a first voltage to a second voltage and an anode to an input side of the potential adjustment circuit that adjusts a voltage from a second voltage to a first voltage and an output side of the potential adjustment circuit that adjusts a voltage from a second voltage to a first voltage and an output side of the potential adjustment circuit that adjusts a voltage from a second voltage to a first voltage and an output side of the potential adjustment circuit that adjusts a voltage from a second voltage to a first voltage and an output side of the potential adjustment circuit that adjusts a voltage from a second voltage and an anode to a second voltage and an output side of the potential adjustment circuit that adjusts a voltage from ...

3. In claim 1, A voltage measuring method, comprising the steps of: inputting the first voltage to the measuring device and measuring the voltage when the positive voltage is measured.

4. In claim 1, 2. A voltage measuring method, comprising: a measurement target that outputs the first voltage;

5. In claim 1, The voltage measuring method according to claim 1, wherein the object to be measured that outputs the first voltage is any one of an AC-DC converter, a half-wave rectifier circuit, and a switching regulator.

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