Drive circuit

Abstract

This invention provides a drive circuit that can calculate the optimal phase adjustment amount by applying current to an external load. [Solution] The drive circuit (600, 700) according to this disclosure includes a control circuit (11, 9) that outputs a first AC signal (V11) and a second AC signal (V12, V2) from an AC signal source (1, 10), a reference voltage generation circuit (3) that has a differential amplifier that generates a first AC voltage (V21) from the first AC signals (V11, V1) and outputs the first AC voltage (V21) to one end of an external load (4), and a second AC The system includes a voltage-to-current conversion circuit (2) that supplies alternating current (I) to an external load from current signals (V12, V2), and a comparator (7) connected to both ends of the external load (4) that compares a first alternating voltage (V21) at one end of the external load with a second alternating voltage (V22) at the other end of the external load, and changes the output voltage (V23) when the first alternating voltage (V21) and the second alternating voltage (V22) are reversed.

Description

Technical Field

[0001] This disclosure relates to a drive circuit.

Background Art

[0002] Patent Document 1 discloses a drive circuit for driving a connected load provided with a phase adjuster. The phase adjuster can perform phase adjustment by monitoring the output voltage (V22) from the voltage-current conversion circuit 2.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The phase adjustment of Patent Document 1 describes a mechanism that can perform adjustment by brute force. However, an efficient phase adjustment method is not considered. Therefore, in the test / evaluation for shipment, it is necessary to perform phase adjustment by brute force. Furthermore, since the load (something having impedance with respect to frequency, for example, a sensor) changes for each device, phase adjustment is required for each device development, and the man-hours for adjustment are extremely large.

[0005] This disclosure has been made to solve such problems, and an object thereof is to provide an apparatus and method capable of efficiently performing phase adjustment. Other problems and novel features will become apparent from the description of this specification and the accompanying drawings.

Means for Solving the Problems

[0006] The drive circuit according to this disclosure includes an AC signal source, a control circuit that outputs a first AC signal and a second AC signal from the AC signal source, and a differential amplifier that generates a first AC voltage of constant amplitude from the first AC signal, and a reference voltage generation circuit that outputs the first AC voltage to one end of an external load, comprising: a first resistor to which a predetermined voltage is applied at one end and whose other end is connected to a first input terminal of the differential amplifier; and a second resistor to which one end is connected to the first input terminal of the differential amplifier and whose other end is connected to an output terminal of the differential amplifier, and receiving the first AC signal at the second input terminal of the differential amplifier, and generating the first AC voltage from the output terminal of the differential amplifier The control circuit comprises a reference voltage generation circuit that outputs a value, a comparator connected to the other end of the external load which supplies an AC current of a constant amplitude from the second AC signal to the external load, and a comparator connected to both ends of the external load which compares the first AC voltage at one end of the external load with the second AC voltage at the other end of the external load and changes the output voltage when the first AC voltage and the second AC voltage are reversed, and the control circuit calculates the amount of phase adjustment of the second AC signal with respect to the first AC signal based on the change in output voltage from the comparator so that the first AC voltage and the second AC voltage are in opposite phase. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a drive circuit, etc., that can find the optimal phase adjustment amount by passing current through an external load. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a circuit diagram showing the configuration of the drive circuit according to Embodiment 1. [Figure 2] Figure 2 is a graph illustrating an example of phase adjustment based on the voltage difference between the reference voltage and the load. [Figure 3] Figure 3 shows the AC waveform before phase adjustment. [Figure 4] Figure 4 shows the AC waveform after phase adjustment. [Figure 5] Figure 5 shows another example of an AC waveform before phase adjustment. [Figure 6] Figure 6 shows another example of an AC waveform after phase adjustment. [Figure 7] Figure 7 is a circuit diagram showing the configuration of the drive circuit according to Embodiment 2. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a circuit diagram showing the configuration of a drive circuit according to Embodiment 1. The drive circuit 600 has a phase adjustment unit 110 that provides a phase adjustment function to the AC voltage signal source 10.

[0010] It is also possible to monitor the amplitude of the voltage V22 at one end of the load 4 and perform phase adjustment from the amplitude of voltage V22 so that voltage V22 and voltage V21 are in opposite phase. In contrast, this disclosure identifies the point in time when voltages V22 and V21 reverse (zero cross) from the voltage difference V22-V21 between the load (e.g., a sensor), and then calculates the amount of phase adjustment so that the voltage difference V22-V21 and voltage V21 are in opposite phase.

[0011] The optimal phase adjustment amount can be calculated using either the voltage V22 or the voltage difference V22-V21. When using the voltage V22, the phase of the voltage V22 changes depending on the setting of the phase adjuster (phase adjustment amount), so when finding the optimal phase adjustment amount, information on the phase adjustment amount as well as the voltage V22 is required.

[0012] On the other hand, when using the voltage difference V22-V21, the phase of the voltage difference V22-V21 is uniquely determined by the phase of the current output by the voltage-current conversion circuit and the impedance of the load, and therefore does not depend on the settings of the phase adjuster. In other words, the optimal phase adjustment amount can be found using only the information obtained from the voltage difference V22-V21. From the above, adjusting the phase from the voltage difference V22-V21 makes it possible to calculate the phase purely without being influenced by other factors due to the characteristics of the circuit configuration.

[0013] Therefore, in this disclosure, the comparator 7 monitors the voltage difference V22-V21 across the load 4, identifies the point in time when voltages V22 and V21 reverse, and calculates a phase adjustment amount such that the voltage difference V22-V21 and voltage V21 are in opposite phase. The control circuit 11 adjusts the phase of the AC voltage signal V11 relative to the AC voltage signal V12 based on this phase adjustment amount.

[0014] The drive circuit 600 according to Embodiment 1 will be described in detail below. The AC voltage signal source 10 outputs an AC voltage signal V11 (also referred to as the first AC voltage signal) to the reference voltage generation circuit 3 and an AC voltage signal V12 (also referred to as the second AC voltage signal) to the voltage-current conversion circuit 2. The AC voltage signal V11 is a voltage with the shape of a sinusoidal curve with a constant amplitude. The AC voltage signal V12 is a voltage with the shape of a sinusoidal curve with a constant amplitude. One terminal T1 of the AC voltage signal source 10 is connected to the non-inverting (positive-phase) input terminal indicated by a plus sign of the reference voltage generation circuit 3. The other terminal T2 of the AC voltage signal source 10 is connected to the non-inverting (positive-phase) input terminal indicated by a plus sign of the voltage-current conversion circuit 2. Here, the voltage output from terminal T1 is referred to as the AC voltage signal V11, and the voltage output from terminal T2 is referred to as the AC voltage signal V12.

[0015] The voltage-current conversion circuit 2 is a circuit that outputs a current signal (i.e., an in-phase current signal) to the load 4 that is proportional to the input AC voltage signal V12. The positive-phase input terminal of the voltage-current conversion circuit 2 is connected to terminal T2 of the AC voltage signal source 10. A DC power supply 5 that outputs a DC voltage V1 (also called a predetermined voltage) of magnitude VDD / 2 is inserted between the negative-phase input terminal of the voltage-current conversion circuit 2 and ground. The negative-phase input terminal of the voltage-current conversion circuit 2 is connected to the high-voltage side terminal of the DC power supply 5. The output terminal of the voltage-current conversion circuit 2 is connected to one end of the load 4. Since the voltage-current conversion circuit 2 outputs a current signal that is in phase with the AC signal V12, the output voltage V22 (also called a second AC voltage) of the voltage-current conversion circuit 2 is in phase with the AC voltage signal V12. The voltage-current conversion circuit 2 receives power by being inserted between the power supply voltage VDD and ground.

[0016] The reference voltage generation circuit 3 generates a reference voltage V21 (also referred to as the first AC voltage) to supply current to the load 4. In this example, the reference voltage generation circuit 3 is configured as a non-inverting amplifier. The AC voltage signal V11 from the AC voltage signal source 10 is input to the positive-sequence input terminal of the reference voltage generation circuit 3. A DC power supply 5 that outputs a DC voltage V1 (also referred to as a predetermined voltage) of magnitude VDD / 2 and a resistor R1 are inserted between the negative-sequence input terminal and ground of the reference voltage generation circuit 3. The DC voltage V1 is input to the negative-sequence input terminal of the reference voltage generation circuit 3. In addition, a resistor R2 is inserted between the negative-sequence input terminal and the output terminal of the reference voltage generation circuit 3. The output terminal of the reference voltage generation circuit 3 is connected to the other end of the load 4. The reference voltage generation circuit 3 receives power by being inserted between the power supply voltage VDD and ground.

[0017] In this example, an AC voltage signal V12 is input to the non-inverting input terminal of the voltage-current conversion circuit 2, and a DC voltage V1 is input to the inverting input terminal. A DC voltage V1 is input to the non-inverting input terminal of the reference voltage generation circuit 3, and an AC voltage signal V11 is input to the inverting input terminal. As a result, when the load 4 is a resistor or the like and the voltage phase of V22 does not change, and the AC voltage signal V12 and the AC voltage signal V11 are phase-adjusted to be in opposite phases, the reference voltage V21 output by the reference voltage generation circuit 3 becomes an AC voltage in the opposite phase to the output voltage V22 of the voltage-current conversion circuit 2.

[0018] In other embodiments, the reference voltage generation circuit 3 may be configured as an inverting amplifier, and an AC signal in the same phase as the AC voltage signal V12 may be input to the input terminal of the reference voltage generation circuit 3. Further, if the reference voltage generation circuit 3 can output a reference voltage in the opposite phase to the output voltage of the voltage-current conversion circuit 2, it can be configured in other ways.

[0019] The AC voltage signal source 10 includes a control circuit 11, digital-to-analog converters (DACs) 12 and 13, and low-pass filters (LPFs) 14 and 15. The control circuit 11 includes a phase adjustment unit 110.

[0020] The control circuit 11 outputs digital signals for controlling the operations of the DACs 12 and 13. The patterns of the digital signals to the DACs 12 and 13 are stored in the control circuit 11 as an array. The DACs 12 and 13 output an AC voltage by converting the input digital signals into analog signals. The high-frequency components of the AC voltage output from the DAC 12 are removed by the LPF 14 and output as the AC signal V12 from the terminal T2. The high-frequency components of the AC voltage output from the DAC 13 are removed by the LPF 15 and output as the AC signal V11 from the terminal T1.

[0021] For example, the control circuit 11 can delay the phase of the AC voltage signal V11 compared to the AC voltage signal V12 by delaying the digital signal supplied to the DAC 13 compared to the digital signal supplied to the DAC 12 using the phase adjustment unit 110. Alternatively, the control circuit 11 can advance the phase of the AC voltage signal V11 compared to the AC voltage signal V12 by advancing the digital signal supplied to the DAC 13 compared to the digital signal supplied to the DAC 12 using the phase adjustment unit 110.

[0022] Furthermore, the AC voltage signal source 10 can be applied to drive circuits according to other embodiments other than the drive circuit 600.

[0023] Comparator 7 is installed across load 4 and compares the voltages across the load. When voltages V22 and V21 reverse (zero cross), it can change the pulsed output voltage V23 from high (H) to low (L) or from low (L) to high (H). Comparator 7 outputs this output voltage V23 to the control circuit 11 of AC voltage signal source 10. Comparator 7 receives power by being inserted between the power supply voltage VDD and ground.

[0024] When the control circuit 11 receives a signal indicating a change in the output voltage V23 of the comparator 7, it records the sequence number of the digital signal to be input to the DAC 12. From the sequence number of the digital signal for the DAC 12 recorded by the control circuit 11, it calculates the sequence number (i.e., the phase adjustment amount) to delay or advance the digital signal to be input to the DAC 13.

[0025] Figure 2 is a graph illustrating an example of phase adjustment based on the voltage difference between the reference voltage and the load. The horizontal axis of the graph corresponds to time, and specifically shows the sequence number (Nth) of the digital signal input by the control circuit 11 to the DAC 12.

[0026] The control circuit 11 controls the phase adjustment so that the reference voltage V21 is in opposite phase to the output voltage V22. As shown in Figure 2, the optimal phase adjustment is when voltage V22 and voltage V21 are in opposite phase. This means that the optimal phase adjustment is when the voltage difference V22-V21 and voltage V21 are in opposite phase.

[0027] To explain this mathematically, if we define V22 = Asin2πft (where A is the amplitude and is a positive value), then when V21 is in opposite phase, V21 = Bsin(2πft-180°) = -Bsin2πft (where B is the amplitude and is a positive value). In this case, V22-V21 becomes V22-V21 = Asin2πft-(-Bsin2πft) = (A+B)sin2πft. V22-V21 is in opposite phase to V21 and in phase with V22. In other words, if V22 and V21 are in opposite phase, then V22-V21 and V21 will also be in opposite phase. Therefore, adjusting V22-V21 to be in opposite phase to V21 has the same effect as adjusting V22 to be in opposite phase to V21.

[0028] Refer to Figures 3 to 6 to explain an example of calculating the phase adjustment amount. One period of the AC amplitude consists of a 72-step DAC array. Figure 3 shows the AC waveform before phase adjustment. In the AC waveform of V21 shown in Figure 3, 'a' represents the phase of V21 relative to V12 and is a known value (this can be any value (see Figure 5), and in this example, V21 lags V12 by 36 steps).

[0029] In Figure 3, the b in the AC waveform of V22-V21 represents the time when the sine wave is zero, indicating the timing when V23 changes from high to low relative to V12 (i.e., the timing when V22 and V21 reverse direction). For example, let's say b is 27 steps. V22-V21 is leading V12 by half a period of 36 steps - 27 steps = 9 steps.

[0030] Therefore, by making a equal to b (a=b), V22-V21 and V21 can be made out of phase. The control circuit 11 should delay the digital signal (V21) input to DAC13 by 36 steps (out of phase) - 9 steps = 27 steps relative to the digital signal (V12) input to DAC12. In other words, the control circuit 11 should delay the digital signal (V21) input to DAC13 by the number of steps (27 steps) of the DAC array at the timing when V23 changes from H to L. Figure 4 shows the AC waveform after phase adjustment. In Figure 4, the phase of V21 relative to V12 is delayed by 27 steps from Figure 3. As a result, a=b, and it can be seen that V22 and V21 are out of phase, and V22-V21 and V21 are also out of phase.

[0031] In the example described above, the phase adjustment amount is calculated at the initial H→L timing, but it may also be calculated at the L→H timing. Furthermore, to stabilize the waveform, the phase adjustment amount may be calculated at an arbitrary number of switching timings (e.g., the 10th time). In other embodiments, the phase adjustment amount may be calculated for multiple switching timings (H→L, L→H), and these calculations may be averaged to obtain the final phase adjustment amount.

[0032] Figure 5 shows another example of the AC waveform before phase adjustment. The output voltage of the voltage-current conversion circuit 2 (i.e., V22) cannot be greater than the power supply voltage and cannot be less than ground (0V). If the phase adjustment is insufficient, the voltage-current conversion circuit 2 may not be able to supply the intended AC current signal, and the voltage of V22 may clip, resulting in a non-sine wave. However, as shown in Figure 5, even if the voltage of V22 clips and the AC waveform is no longer a sine wave, phase adjustment is possible as long as it does not affect the waveform near the reversal (zero-crossing) of V22 and V21. Figure 6 shows another example of the AC waveform after phase adjustment. In Figure 6, a=b, and V22 and V21 are in opposite phase, and V22-V21 and V21 are in opposite phase. From the above, it can be said that before phase adjustment, the phase of V21 relative to V12 can be any value.

[0033] Figure 7 is a circuit diagram showing the configuration of the drive circuit according to Embodiment 2. The drive circuit 700 has a configuration in which the resistors R1 and R2 of the reference voltage generation circuit 3 in the drive circuit 600 shown in Figure 1 are replaced with variable resistors VR1 and VR2, respectively, and a control circuit 9 is added. The control circuit 9 is composed of, for example, a digital circuit and can control the resistance values ​​of the variable resistors VR1 and VR2. The control circuit 9 controls not only the resistance values ​​of the variable resistors VR1 and VR2, but also the phase adjustment amount of the phase adjuster 6.

[0034] In other embodiments, one or both of the first resistor R1 and the second resistor R2 may be variable resistors. The control circuit 9 may control the resistance values ​​of one or both of the first resistor R1 and the second resistor R2.

[0035] AC voltage signal source 1 outputs an AC voltage signal. One terminal T2 of AC voltage signal source 1 is connected to the positive-phase input terminal of voltage-current conversion circuit 2, and the other terminal T1 is connected to DC power supply 5. A DC power supply 5 that outputs a DC voltage V1 (also called a predetermined voltage) of magnitude VDD / 2 is inserted between terminal T1 of AC voltage signal source 1 and ground. The high-voltage side terminal of DC power supply 5 is connected to terminal T1 of AC voltage signal source 1, and the low-voltage side terminal is connected to ground. Here, the voltage output from terminal T1 is referred to as DC voltage V1, and the voltage output from terminal T2 is referred to as AC signal V2. The AC signal after phase adjustment is referred to as V11. In addition, counter 23 is connected to AC voltage signal source 1 and control circuit 9.

[0036] The control circuit 9 can instruct the AC voltage signal source 1 and the counter 23 to start and stop operation. A comparator 7 connected to both ends of the load 4 can compare the voltages across the load 4. The comparator 7 changes the output voltage V23 from H to L or L to H when V22 and V21 reverse direction (zero cross). The control circuit 9 measures the timing of the AC signal using the counter 23. The control circuit 9 receives the timing of the change in the output voltage V23 (from H to L) from the comparator 7 and latches and acquires the value of the counter 23. The control circuit 9 sets the phase adjuster 6 so that the voltage signal V21 is delayed by the value of the counter. This allows the phase to be adjusted so that V22-V21 and V21 are in opposite phase.

[0037] This disclosure provides the following drive circuit. That is, the drive circuit (600, 700) includes an AC signal source (1, 10), a control circuit (11, 9) that outputs a first AC signal (V11) and a second AC signal (V12, V2) from the AC signal source, and a reference voltage generation circuit (3) that has a differential amplifier that generates a first AC voltage (V21) of constant amplitude from the first AC signals (V11, V1) and outputs the first AC voltage (V21) to one end of an external load (4), and comprises a first resistor (R1) to which a predetermined voltage is applied at one end and the other end is connected to the first input terminal of the differential amplifier, and a second resistor (R2) to which one end is connected to the first input terminal of the differential amplifier and the other end is connected to the output terminal of the differential amplifier, and the differential The differential amplifier includes a reference voltage generation circuit (3) that receives the first AC signal (V11) at the second input terminal of the dynamic amplifier and outputs the first AC voltage (V21) from the output terminal of the differential amplifier; a voltage-current conversion circuit (2) connected to the other end of the external load (4) that supplies an AC current (I) of constant amplitude from the second AC signals (V12, V2) to the external load; and a comparator (7) connected to both ends of the external load (4) that compares the first AC voltage (V21) at one end of the external load with the second AC voltage (V22) at the other end of the external load and changes the output voltage (V23) when the first AC voltage (V21) and the second AC voltage (V22) are reversed. The control circuit (11,9) calculates the amount of phase adjustment of the second AC signal (V12) relative to the first AC signal (V11) based on the change in the output voltage (V23) from the comparator (7), such that the first AC voltage (V21) and the second AC voltage (V22) are in opposite phase.

[0038] As explained above, according to this disclosure, there is no need to perform phase adjustment multiple times to find the optimal phase adjustment amount. In other words, the phase adjustment amount (optimal setting) can be found by passing current through the external load only once, thus reducing the man-hours required for phase adjustment. Because automatic adjustment is possible, it can also accommodate changes in load characteristics over time. Since the phase adjustment amount is calculated from the point where the voltages V22 and V21 across the load reverse (zero cross), the phase adjustment amount can be calculated even if current is passed through the load with insufficient phase adjustment, resulting in a large voltage amplitude of V22 and clipping to the power supply or ground.

[0039] The present inventors have described in detail above based on embodiments, but The description is not limited to the above-described embodiment, and various modifications may be made without departing from its essence. It goes without saying that it is Noh theater. [Explanation of Symbols]

[0040] 1 AC voltage signal source 2. Voltage-to-current conversion circuit 3. Reference voltage generation circuit 4 load 5 DC power supply 6. Phase Adjuster 7 Comparator 9. Control circuits 10 AC voltage signal source 11 Control circuits 12, 13 Digital-to-Analog Converter (DAC) 14, 15 Low-pass filter (LPF) 23 counters 110 Phase adjustment 600 drive circuit 700 drive circuit

Claims

1. AC signal source and A control circuit that outputs a first AC signal and a second AC signal from the aforementioned AC signal source, A reference voltage generation circuit having a differential amplifier that generates a first AC voltage of constant amplitude from the first AC signal, and outputting the first AC voltage to one end of an external load, A reference voltage generation circuit comprising: a first resistor to which a predetermined voltage is applied at one end and whose other end is connected to the first input terminal of the differential amplifier; and a second resistor to which one end is connected to the first input terminal of the differential amplifier and whose other end is connected to the output terminal of the differential amplifier, wherein the circuit receives the first AC signal at the second input terminal of the differential amplifier and outputs the first AC voltage from the output terminal of the differential amplifier, A voltage-current conversion circuit connected to the other end of the external load supplies a constant amplitude AC current to the external load from the second AC signal, A comparator connected to both ends of the external load, which compares the first AC voltage at one end of the external load with the second AC voltage at the other end of the external load, and changes the output voltage when the first AC voltage and the second AC voltage reverse direction. Equipped with, The control circuit is a drive circuit that calculates the amount of phase adjustment of the second AC signal with respect to the first AC signal based on the change in output voltage from the comparator, such that the first AC voltage and the second AC voltage are in opposite phase.

2. The control circuit stores the digital signal pattern as an array, The AC signal source outputs a first AC signal from the digital signal from the control circuit via a first digital-to-analog converter (DAC) and a first low-pass filter (LPF). The drive circuit according to claim 1, configured to output a second AC signal from a digital signal from the control circuit via a second digital-to-analog converter (DAC) and a second low-pass filter (LPF).

3. A phase adjuster, inserted between the AC signal source and the voltage-current conversion circuit, or between the AC signal source and the reference voltage generation circuit, for adjusting the phase of the AC signal, A counter connected to the control circuit and the AC signal source, It further includes, The drive circuit according to claim 1, wherein the control circuit is configured to measure the timing of the AC signal of the AC signal source using the counter, receive the timing of the change in the output voltage from the comparator, latch and acquire the value of the counter, and control the amount of phase adjustment of the AC signal in the phase adjuster so that the first AC voltage and the second AC voltage are in opposite phase, based on the value of the counter.

4. One or both of the first resistor and the second resistor are variable resistors. The drive circuit according to claim 1, wherein the control circuit controls the resistance values ​​of one or both of the first resistor and the second resistor.

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