A signal output circuit and method

Abstract

The application discloses a signal output circuit and method, and belongs to the technical field of electronic circuits. The circuit comprises: a first operation circuit configured as a same-phase proportional attenuation circuit, which is used for attenuating a power supply voltage by a first fixed proportion to generate a reference voltage; a signal processing unit, whose power supply end and reference end are both connected to the reference voltage, which is used for processing an input signal to generate an intermediate output signal; and a second operation circuit configured as a same-phase proportional amplification circuit, which is used for amplifying the intermediate output signal by a second fixed proportion to generate a final output signal. The two operation circuits adopt operation amplifiers of the same specification, and the two fixed proportions are reciprocal. The application constructs a symmetrical proportional scaling link, so that the final output signal is proportional to the power supply voltage in real time and accurately, thereby adapting to wide-range power supply voltage changes, and stability and anti-interference capability are improved.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a signal output circuit and method. Background Technology

[0002] In fields such as automotive electronics, sensor measurement, and industrial control, many electronic devices need to process signals from sensitive components and convert them into standardized voltage signals for output to subsequent controllers.

[0003] In existing signal processing circuits, low-dropout linear regulators (LDOs) or on-chip voltage modulators are typically used to provide a stable and fixed operating voltage and reference voltage for the signal processing unit. The advantage of this approach is stable power supply, but its disadvantages are also significant: the amplitude of the output signal is entirely determined by this fixed reference voltage and is independent of the external power supply voltage; this leads to the following problems: Poor product compatibility: A sensor designed to output 0.5V-4.5V under 5V power supply will still have an output range of 0.5V-4.5V when applied to an 8V or 12V power supply system. If the host computer controller expects a signal proportional to the power supply voltage, it cannot be directly used, limiting the product's versatility.

[0004] Unable to achieve adaptive calibration: After the product leaves the factory, its signal output characteristics are fixed and cannot be dynamically adjusted or calibrated according to the actual voltage of the power supply system on site, making it difficult to meet the needs of customers who require a continuously variable signal range.

[0005] Power supply fluctuations introduce errors: In systems with unstable power supply voltage (such as automotive batteries and energy harvesting systems), a fixed output signal cannot reflect the impact of power supply fluctuations, or measurement errors are introduced due to power supply ripple, which reduces the robustness of the system and measurement consistency. Summary of the Invention

[0006] To address the technical problems of signal output being independent of power supply voltage and poor product adaptability in existing technologies, this application provides a signal output circuit and method that adjusts proportionally to the power supply voltage.

[0007] The first technical solution adopted in this application is: providing a signal output circuit, including: The first operational circuit is configured as a non-inverting proportional attenuation circuit. Its input terminal receives the power supply voltage, and its output terminal generates a reference voltage. The attenuation ratio of the first operational circuit is set to a first fixed ratio by a first set of resistors. A signal processing unit, whose power supply terminal and reference terminal are both connected to the output terminal of the first arithmetic circuit to receive the reference voltage, is configured to process the input signal according to the reference voltage to generate an intermediate output signal; The second operational circuit is configured as a non-inverting amplifier circuit. Its input terminal receives the intermediate output signal, and its output terminal generates the final output signal. The amplification ratio of the second operational circuit is set to a second fixed ratio by the second set of resistors. The first operational circuit and the second operational circuit are constructed using operational amplifiers of the same specifications, and the first fixed ratio and the second fixed ratio are reciprocals of each other.

[0008] Furthermore, it also includes: a bias voltage compensation module, whose input terminal is connected to the output terminal of the first arithmetic circuit to receive the reference voltage, and configured to generate a bias voltage based on the reference voltage, the bias voltage being used to provide an operating voltage for the internal circuitry of the signal processing unit.

[0009] Furthermore, the signal processing unit is a microcontroller, which includes an analog-to-digital converter and a digital-to-analog converter, and the reference voltage input terminals of the analog-to-digital converter and the digital-to-analog converter are both connected to the output terminal of the reference voltage.

[0010] Furthermore, it also includes: a drive interface configured to connect to an external transformer coil and provide a drive signal thereto; and a signal input interface configured to receive a secondary side signal from the external transformer coil as the input signal.

[0011] Furthermore, the first group of resistors and the second group of resistors are resistors from the same batch and made of the same material.

[0012] The second technical solution adopted in this application is: providing a signal output method, including the following steps: A first operational circuit is used to attenuate the supply voltage in phase to generate a reference voltage, wherein the attenuation ratio of the first operational circuit is set to a first fixed ratio by a first set of resistors. The reference voltage is used simultaneously as the power supply voltage and reference voltage of a signal processing unit, and the signal processing unit processes the input signal according to the reference voltage to generate an intermediate output signal. The intermediate output signal is amplified by a second operational circuit in an in-phase manner to generate the final output signal. The amplification ratio of the second operational circuit is set to a second fixed ratio by a second set of resistors. The first operational circuit and the second operational circuit use operational amplifiers of the same specifications, and the first fixed ratio and the second fixed ratio are reciprocals of each other.

[0013] Furthermore, it also includes: generating a bias voltage based on the reference voltage, and using the bias voltage to provide an operating voltage for the internal circuitry of the signal processing unit.

[0014] Furthermore, the signal processing unit is a microcontroller, and the method further includes: using the reference voltage as a common reference voltage for the analog-to-digital converter and the digital-to-analog converter within the microcontroller.

[0015] Furthermore, it also includes: providing a drive signal to an external transformer coil via a drive interface; and receiving a secondary side signal from the external transformer coil via a signal input interface and using it as the input signal.

[0016] Furthermore, the first fixed ratio and the second fixed ratio are set by using a first group of resistors and a second group of resistors made of the same batch and material.

[0017] Due to the adoption of the above technical solution, this application has at least one of the following beneficial effects compared with the prior art: 1. By setting a first operational circuit and a second operational circuit with attenuation ratios that are reciprocals of each other, and using the reference voltage output by the first operational circuit as both the power supply and reference source of the signal processing unit, the signal processing unit processes a reference voltage that is proportional to the supply voltage, and the final output signal can be accurately restored to an output that is proportional to the supply voltage.

[0018] 2. A symmetrical operational amplifier structure is adopted, and the circuit has good common-mode rejection capability and temperature consistency. When the supply voltage fluctuates due to load changes or external interference, the entire signal link will adjust synchronously and proportionally, which is equivalent to a dynamic compensation mechanism. This effectively suppresses the measurement error caused by power supply ripple and improves the robustness of the system.

[0019] 3. This invention does not require expensive programmable power management chips or complex software calibration algorithms. It can be implemented using only standard operational amplifiers, resistors, and conventional MCUs, resulting in a simple circuit structure. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 A schematic diagram of the signal output circuit provided in an embodiment of this application; Figure 2 A schematic diagram of the signal output circuit provided in another embodiment of this application; Figure 3 This is a schematic flowchart of a signal output method provided in an embodiment of this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are only for explaining this application and not for limiting it. Furthermore, it should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, not all structures. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] The terms "first," "second," etc., used in this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] In existing technologies, the power supply voltage and reference voltage of the signal processing unit are usually provided by independent fixed regulators (such as LDOs), which means that the amplitude of its output signal is only related to the input signal and not to the power supply voltage of the system. When the power supply voltage varies over a wide range, the output signal cannot be adjusted proportionally, making it difficult for the same circuit to adapt to application scenarios with different voltage standards. It also cannot meet the needs of the host computer to determine the system status based on the ratio of output to power supply, resulting in serious deficiencies in product compatibility and adaptability.

[0025] In view of this, this application provides a signal output circuit that attenuates the supply voltage by a fixed ratio and uses it as a unified reference and power supply for the signal processing unit, then amplifies and recovers it by a reciprocal ratio, so that the final output signal changes proportionally to the supply voltage in real time; such as Figure 1 As shown, Figure 1 A schematic diagram of the signal output circuit provided in one embodiment of this application includes: The first operational circuit is configured as a non-inverting proportional attenuation circuit. Its input terminal receives the power supply voltage, and its output terminal generates a reference voltage. The attenuation ratio of the first operational circuit is set to a first fixed ratio by the first set of resistors. The signal processing unit has its power supply terminal and reference terminal both connected to the output terminal of the first operational circuit to receive a reference voltage. The signal processing unit is configured to process the input signal according to the reference voltage to generate an intermediate output signal. The second operational circuit is configured as a non-inverting amplifier circuit. Its input terminal receives the intermediate output signal, and its output terminal generates the final output signal. The amplification ratio of the second operational circuit is set to a second fixed ratio by the second set of resistors. The first operational circuit and the second operational circuit are constructed using operational amplifiers of the same specifications, and the first fixed ratio and the second fixed ratio are reciprocals of each other.

[0026] The core concept of the signal output circuit lies in constructing a signal link that first attenuates proportionally and then recovers proportionally, ensuring that the entire operating domain of the signal processing unit is below the attenuated reference voltage. The working principle of the signal output circuit is described in detail below: Specifically, the first operational circuit is essentially a non-inverting proportional attenuator, whose attenuation ratio is set by a first set of resistors to a first fixed ratio (value greater than 0 and less than 1). This circuit is not used for voltage regulation, but rather for precisely scaling down the supply voltage to generate a reference voltage, which is equal to the first fixed ratio multiplied by the supply voltage.

[0027] The signal processing unit can be a microcontroller, a digital signal processor, or a dedicated signal conditioning chip; unlike traditional designs that separate the power supply and reference, in this application, the power supply terminal and the reference reference terminal of the signal processing unit are both connected to a reference voltage; this means: All analog-to-digital converters, digital-to-analog converters, and the reference level for signal processing within the signal processing unit are proportional to the supply voltage in real time. The result of its processing of the input signal (i.e., the intermediate output signal) will naturally be expressed as the processing function of the input signal multiplied by the reference voltage, that is, the processing function of the input signal multiplied by the first fixed ratio and then multiplied by the supply voltage.

[0028] The second operational circuit is a non-inverting amplifier, whose amplification ratio (greater than 1) is set by a second set of resistors. To ensure the supply voltage factor is fully preserved, the second fixed ratio is set to the reciprocal of the first fixed ratio. Therefore, the final output signal equals the second fixed ratio multiplied by the intermediate output signal, which is the reciprocal of the first fixed ratio multiplied by the input signal processing function multiplied by the first fixed ratio, then multiplied by the supply voltage, ultimately equal to the input signal processing function multiplied by the supply voltage.

[0029] As can be seen from this derivation, no matter how the supply voltage changes (within its allowable range), the final output signal is always precisely equal to the product of the processed input signal and the current supply voltage, thus achieving the goal of proportionally adjusting the output signal according to the power supply voltage.

[0030] As a key technical means, in order to ensure the accuracy of the proportional relationship and the temperature stability of the entire signal chain, this embodiment specifically stipulates that the first operational circuit and the second operational circuit must use operational amplifiers of the same specifications. This can maximize the offsetting of gain error and common-mode error caused by device inconsistency.

[0031] like Figure 2 As shown, Figure 2 The diagram below shows a schematic of the signal output circuit according to another embodiment of this application. The signal output circuit further includes a bias voltage compensation module, whose input terminal is connected to the output terminal of the first operational circuit to receive a reference voltage and is configured to generate a bias voltage based on the reference voltage. The bias voltage is used to provide an operating voltage for the internal circuit of the signal processing unit.

[0032] In practical applications, the signal processing unit may have a minimum operating voltage. However, the reference voltage after attenuation by the first operational circuit may be lower than this requirement when the supply voltage is low; for example, if the minimum operating voltage is 5V, the supply voltage is 8V, and the first fixed ratio is half; in this case, the reference voltage is 4V < 5V.

[0033] To address this issue, this embodiment introduces a bias voltage compensation module. The input of this module is connected to the output of the first operational circuit to obtain a reference voltage. Internally, it can be a charge pump, a boost DC-DC converter, or a low-dropout linear regulator. Its function is to generate a higher, more stable bias voltage based on the reference voltage. This bias voltage is used solely to provide operating voltage for the internal digital logic circuits or analog circuits of the signal processing unit, ensuring their normal startup and operation.

[0034] It is particularly important to emphasize that the reference voltage terminals of the analog-to-digital converter (ADC) and digital-to-analog converter (DAC) within the signal processing unit must still be directly connected to the original reference voltage, not the boosted bias voltage. Only in this way can the quantization scale of the ADC / DAC maintain a proportional relationship with the reference voltage, which is the core of achieving proportional following between the final output and the supply voltage. The bias voltage compensation module only addresses the power supply capability and does not participate in the transmission of the proportional signal.

[0035] The signal processing unit is a microcontroller, which includes an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC). The reference voltage input terminals of both the ADC and the DAC are connected to the output terminal of the reference voltage.

[0036] The reference voltage inputs of both the analog-to-digital converter (ADC) and the digital-to-analog converter (DAC) of the microcontroller are directly connected to the reference voltage output by the first operational circuit. This means that the full-scale value of the ADC during quantization is the reference voltage, and the full-scale value of the DAC during analog output is also the reference voltage. Therefore, when a change in the supply voltage causes a proportional change in the reference voltage, the ADC reading and the DAC output will scale synchronously and proportionally, thus maintaining a proportional relationship with the supply voltage throughout the entire digital processing path.

[0037] The signal output circuit also includes a drive interface (not shown) and a signal input interface (not shown). The drive interface is configured to connect to an external transformer coil and provide a drive signal to it; the signal input interface is configured to receive the secondary side signal of the external transformer coil as an input signal.

[0038] The input of the drive interface is connected to the output of the pulse width modulator or signal generator of the signal processing unit, and the output is connected to the primary side of the external transformer coil. Specifically, the drive interface can be a bridge driver chip or a full-bridge circuit. Since driving the transformer coil requires a large current and voltage swing, and the microcontroller's input / output ports lack sufficient driving capability, this drive interface is needed for power amplification. It is worth noting that the power supply of this drive interface is directly connected to the original supply voltage; thus, when the supply voltage changes, the amplitude of the excitation signal applied to the primary side of the transformer will change synchronously.

[0039] The input terminal of the signal input interface is connected to the secondary side of the external transformer coil, and its output terminal is connected to the input terminal of the analog-to-digital converter of the signal processing unit. The signal input interface can be a voltage divider circuit, a filter circuit, or a front-end amplifier, used to condition the weak induced signal on the secondary side to the range that the analog-to-digital converter can sample, without any limitation.

[0040] Since the amplitude of the primary excitation signal of the transformer coil is proportional to the supply voltage, the amplitude of the induced signal on its secondary side is also proportional to the supply voltage under the same coupling conditions; at the same time, the reference voltage of the microcontroller's analog-to-digital converter is also proportional to the supply voltage. Therefore, when the external physical quantity remains unchanged, the absolute amplitude of the secondary signal changes with the supply voltage, but the digital quantity read by the analog-to-digital converter is constant; when the external physical quantity changes, this digital quantity changes linearly.

[0041] The microcontroller's internal algorithm maps this digital quantity to a preset output range (such as 10% to 95%), and then outputs it through a digital-to-analog converter. Since the reference voltage of the digital-to-analog converter is also a reference voltage, the absolute amplitude of the final intermediate output signal must be within the range of 10% to 95% multiplied by the reference voltage, ensuring a strict proportional relationship between the final output signal and the supply voltage.

[0042] To achieve the ideal relationship where the first and second fixed ratios are reciprocals of each other, in addition to requiring operational amplifiers to have identical specifications, the accuracy and matching of the resistors are crucial. Any deviation in resistor value will directly cause the attenuation ratio and amplification ratio to not perfectly satisfy the reciprocal relationship, thus introducing a ratio error at the output. In this application, the first and second sets of resistors are resistors from the same batch and made of the same material.

[0043] This application also provides a signal output method, such as Figure 3 As shown, Figure 3 A flowchart illustrating a signal output method according to an embodiment of this application includes the following steps: A first operational circuit is used to attenuate the supply voltage in phase to generate a reference voltage. The attenuation ratio of the first operational circuit is set to a first fixed ratio by a first set of resistors. The reference voltage is used as both the power supply voltage and the reference voltage for a signal processing unit. The signal processing unit processes the input signal based on the reference voltage to generate an intermediate output signal. The intermediate output signal is amplified in phase by a second operational circuit to generate the final output signal. The amplification ratio of the second operational circuit is set to a second fixed ratio by a second set of resistors. The first and second operational circuits use operational amplifiers of the same specifications, and the first fixed ratio and the second fixed ratio are reciprocals of each other.

[0044] The signal output method also includes generating a bias voltage based on a reference voltage and using the bias voltage to provide operating voltage for the internal circuitry of the signal processing unit.

[0045] After the reference voltage and before entering the signal processing unit, a bias voltage generation step is added. This step generates a higher and more stable bias voltage based on the reference voltage through a bias voltage compensation module. This bias voltage is then used to power the internal logic circuits of the signal processing unit to ensure its normal function.

[0046] Meanwhile, the analog-to-digital / digital-to-analog conversion operation inside the signal processing unit must use the original reference voltage directly, and cannot use the boosted bias voltage. This hybrid power supply method, which uses the bias voltage for the operating voltage and the reference voltage for the reference voltage, solves the low-voltage startup problem without compromising the accurate transmission of the proportional signal.

[0047] The signal processing unit is a microcontroller, and the method further includes using a reference voltage as a common reference voltage for the analog-to-digital converter and the digital-to-analog converter within the microcontroller.

[0048] Connect the reference voltage generated by the first operational circuit directly, without any buffering or scaling, to the analog-to-digital converter (ADC) reference voltage pin and digital-to-analog converter (DAC) reference voltage pin of the microcontroller. If the reference voltage of the microcontroller's internal ADC / DAC comes from the power supply pin, ensure that the microcontroller's power supply pin is also directly powered by the reference voltage to ensure the consistency of the reference source.

[0049] In this way, all analog-to-digital (A / D) and digital-to-analog (D / A) conversions performed internally by the microcontroller are quantized directly with reference voltage. When a change in the supply voltage causes a change in the reference voltage, the A / D conversion result for the same input physical quantity remains unchanged, while the D / A conversion output amplitude for the same digital quantity follows the change in reference voltage.

[0050] The signal output method also includes: providing a drive signal to an external transformer coil through a drive interface; the signal processing unit generates a high-frequency excitation signal, which is amplified by the drive interface and then applied to the primary side of the external transformer coil; the power supply of the drive interface is directly taken from the supply voltage, so the amplitude of the drive signal is proportional to the supply voltage.

[0051] The transformer coil receives a secondary signal from an external transformer coil via a signal input interface and uses it as an input signal. The secondary side of the transformer coil generates an induced signal containing information about the measured physical quantity due to electromagnetic induction. The induced signal is sent to the analog-to-digital converter input terminal of the signal processing unit via the signal input interface.

[0052] Since the primary excitation amplitude is proportional to the supply voltage, and the magnetic coupling coefficient and the measured physical quantity remain unchanged, the amplitude of the secondary induced signal is also proportional to the supply voltage. This induced signal is used as an input signal and is sampled by an analog-to-digital converter with the same reference voltage.

[0053] Therefore, the digital quantity output by the analog-to-digital converter is proportional to (the amplitude of the induced signal divided by the reference voltage), and its value is constant, eliminating the influence of power supply voltage fluctuations on the original measurement value. Subsequently, the microcontroller maps this digital quantity according to a preset proportional output range and outputs it through the digital-to-analog converter. As mentioned earlier, the output amplitude of the digital-to-analog converter is proportional to the reference voltage, and after being recovered by the second arithmetic circuit, the final output signal is proportional to the power supply voltage.

[0054] The first fixed ratio and the second fixed ratio are set by using a first group of resistors and a second group of resistors made of the same batch and material; in this embodiment, the first group of resistors is the first resistor and the second resistor; the second group of resistors is the third resistor and the fourth resistor.

[0055] The same batch ensures that the ratio of the first resistor to the second resistor and the ratio of the third resistor to the fourth resistor are statistically optimally consistent, reducing the initial ratio deviation caused by production errors.

[0056] The use of the same material ensures a high degree of matching in the temperature coefficients of the resistors. When the ambient temperature changes, the resistance values ​​of the first, second, third, and fourth resistors will change by the same percentage, thus keeping the product of the first and second fixed ratios constant and independent of temperature.

[0057] In the several embodiments provided in this application, it should be understood that the disclosed methods and devices can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0058] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0059] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0060] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A signal output circuit, characterized in that, include: The first operational circuit is configured as a non-inverting proportional attenuation circuit. Its input terminal receives the power supply voltage, and its output terminal generates a reference voltage. The attenuation ratio of the first operational circuit is set to a first fixed ratio by a first set of resistors. A signal processing unit, whose power supply terminal and reference terminal are both connected to the output terminal of the first arithmetic circuit to receive the reference voltage, is configured to process the input signal according to the reference voltage to generate an intermediate output signal; The second operational circuit is configured as a non-inverting amplifier circuit. Its input terminal receives the intermediate output signal, and its output terminal generates the final output signal. The amplification ratio of the second operational circuit is set to a second fixed ratio by the second set of resistors. The first operational circuit and the second operational circuit are constructed using operational amplifiers of the same specifications, and the first fixed ratio and the second fixed ratio are reciprocals of each other.

2. The signal output circuit according to claim 1, characterized in that, Also includes: A bias voltage compensation module has its input terminal connected to the output terminal of the first operational circuit to receive the reference voltage and is configured to generate a bias voltage based on the reference voltage. The bias voltage is used to provide operating voltage for the internal circuitry of the signal processing unit.

3. The signal output circuit according to claim 1, characterized in that, The signal processing unit is a microcontroller, which includes an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC). The reference voltage input terminals of both the ADC and the DAC are connected to the output terminal of the reference voltage.

4. The signal output circuit according to claim 1, characterized in that, Also includes: A drive interface configured to connect to an external transformer coil and provide a drive signal thereto; and a signal input interface configured to receive a secondary side signal from the external transformer coil as the input signal.

5. The signal output circuit according to claim 1, characterized in that, The first group of resistors and the second group of resistors are resistors from the same batch and made of the same material.

6. A signal output method, characterized in that, Includes the following steps: A first operational circuit is used to attenuate the supply voltage in phase to generate a reference voltage, wherein the attenuation ratio of the first operational circuit is set to a first fixed ratio by a first set of resistors. The reference voltage is used simultaneously as the power supply voltage and reference voltage of a signal processing unit, and the signal processing unit processes the input signal according to the reference voltage to generate an intermediate output signal. The intermediate output signal is amplified by a second operational circuit in an in-phase manner to generate the final output signal. The amplification ratio of the second operational circuit is set to a second fixed ratio by a second set of resistors. The first operational circuit and the second operational circuit use operational amplifiers of the same specifications, and the first fixed ratio and the second fixed ratio are reciprocals of each other.

7. The signal output method according to claim 6, characterized in that, Also includes: A bias voltage is generated based on the reference voltage, and the bias voltage is used to provide operating voltage for the internal circuitry of the signal processing unit.

8. The signal output method according to claim 6, characterized in that, The signal processing unit is a microcontroller, and the method further includes: using the reference voltage as a common reference voltage for the analog-to-digital converter and the digital-to-analog converter within the microcontroller.

9. The signal output method according to claim 6, characterized in that, Also includes: A drive signal is provided to an external transformer coil via a drive interface; and a secondary side signal is received from the external transformer coil via a signal input interface and used as the input signal.

10. The signal output method according to claim 6, characterized in that, The first fixed ratio and the second fixed ratio are set by using a first group of resistors and a second group of resistors made of the same batch and material.

Images