A power supply voltage regulation circuit for testing contact smart cards

Abstract

This application relates to a power supply voltage regulation circuit for testing contact smart cards. The circuit includes: a voltage generation unit connected to a main controller, used to convert digital signals sent by the main controller into output voltage signals; a precision calibration unit, which collects the output voltage of the voltage generation unit, compares it with a set reference voltage, and transmits the comparison result to the main controller; and a main controller connected to the voltage generation unit and the precision calibration unit, used to adjust the output voltage according to the comparison result fed back by the precision calibration unit, and output a voltage control signal to the voltage generation unit. The power supply voltage regulation circuit of this application generates the output voltage through a multi-level adjustable gain architecture, realizing high-precision linear mapping from digital signals to output voltage and high-precision adjustment of the output voltage, significantly improving the stability and accuracy of the output voltage.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuits and contact smart card technology, specifically relating to a power control circuit for testing contact smart cards according to the ISO / IEC 7816 standard. Background Technology

[0002] Contact smart card testing involves applying specific stimuli to the smart card under test, measuring its response, and comparing it to the expected response to determine whether the smart card's functionality or performance meets design requirements. In this process, the power supply voltage setting is particularly critical—it is not only the foundation for the card's normal operation but also the core variable triggering various test scenarios. Although international standards (such as ISO / IEC 7816) clearly specify three nominal operating voltages for smart cards (1.8V, 3V, and 5V), to comprehensively cover the functional testing, reliability testing, and security verification of smart cards, voltage signals far exceeding the standards are required.

[0003] Currently, there is considerable research in this field on smart card testing instruments. Beijing Zhongdian Huada Electronics' "A Test Reader with Automatically Controllable Smart Card Power Supply Voltage" (CN201310665341.6) primarily uses an embedded processor to control the output voltage of a digitally controlled potentiometer. This direct control of the output voltage using a resistor is relatively simple, but its output voltage range is only 1.58–7.5V, resulting in a narrow output range and non-linear resolution. Beijing Ziguang Qingteng's "A Power Interference Test Device Applicable to High-Capacity SIM Card Chips"... The interference device mainly uses high-frequency square waves to form a high-frequency disturbance power supply. The test chip's function under such high-frequency disturbance power supply interference is tested. The power supply to the smart card chip is constantly changing, so it cannot measure the chip's operation when the supply voltage is continuously too high or too low. The test system in Datang Microelectronics' "Level Conversion Circuit, Conversion Method and Contact IC Card Test System" (CN202310083202.6) consists of an MCU and a level conversion circuit. It uses a level conversion chip to solve the problem of changing the supply voltage. However, the voltage value can only be controlled by a combination of preset values, which has relatively low flexibility.

[0004] Therefore, there is a lack in the field of adjustable, wide-range power supply voltage regulation circuit and its control method for testing contact smart cards. Summary of the Invention

[0005] This application provides a power supply voltage regulation circuit for testing contact smart cards. Its voltage generation unit controls a differential DAC chip to output a differential current via a main controller. The voltage generation unit then converts the current into a single-ended voltage output and linearly amplifies it. This method significantly improves output stability. A precision calibration unit samples the output voltage and feeds it back to the controller to ensure accuracy. To address the issue of unstable power supply voltage over long periods, a precision calibration circuit and upper / lower limit feedback control circuit are used to ensure the stability of the power supply voltage under prolonged overvoltage and heat generation conditions.

[0006] Specifically, this application provides a power supply voltage regulation circuit, including: a voltage generation unit connected to a main controller, used to convert a digital signal sent by the main controller into an output voltage signal; a precision calibration unit, which collects the output voltage of the voltage generation unit, compares it with a reference voltage set by the main controller, and transmits the comparison result to the main controller; and a main controller connected to the voltage generation unit and the precision calibration unit, used to adjust the voltage control signal output to the voltage generation unit according to the comparison result fed back by the precision calibration unit.

[0007] In the above-mentioned power supply voltage regulation circuit, the power supply voltage regulation circuit further includes: an upper and lower limit feedback unit, which is connected to the main controller and is used to receive the upper and lower limit control signals sent by the main controller and to perform feedback control on the upper and lower limits of the circuit.

[0008] In the above power supply voltage regulation circuit, the voltage generation unit includes: a first digital-to-analog converter circuit, a differential current to single-ended voltage converter circuit, and a voltage amplifier circuit. The first digital-to-analog converter circuit converts the digital signal input by the main controller into a proportional differential current and outputs it to the differential current to single-ended voltage converter circuit. The differential current to single-ended voltage converter circuit converts the differential current into an intermediate voltage and outputs it to the voltage amplifier circuit. The voltage amplifier circuit amplifies the intermediate voltage to obtain the output voltage.

[0009] In the aforementioned power supply voltage regulation circuit, the differential current to single-ended voltage conversion circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a first operational amplifier, wherein: the fourth resistor is connected between the first output terminal of the first digital-to-analog converter circuit and the inverting input terminal of the first operational amplifier; the third resistor is connected between the second output terminal of the first digital-to-analog converter circuit and the non-inverting input terminal of the first operational amplifier; the first end of the first resistor is connected between the second output terminal of the first digital-to-analog converter circuit and the third resistor, and the second end of the first resistor is grounded; the first end of the second resistor is connected between the first output terminal of the first digital-to-analog converter circuit and the fourth resistor, and the second end of the second resistor is grounded; the first end of the fifth resistor is connected between the third resistor and the non-inverting input terminal of the first operational amplifier, and the second end of the fifth resistor is grounded; the first end of the sixth resistor is connected between the fourth resistor and the inverting input terminal of the first operational amplifier, and the second end of the sixth resistor is connected to the output terminal of the first operational amplifier.

[0010] In the above power supply voltage regulation circuit, the formula for converting differential current into voltage by the differential current to single-ended voltage circuit is as follows: in, The current value output from the second output terminal of the first digital-to-analog converter circuit is [value]. R1 represents the current value output from the first output terminal of the first digital-to-analog converter circuit, R2 represents the first resistor value, R3 represents the third resistor value, R4 represents the fourth resistor value, R5 represents the fifth resistor value, and R6 represents the sixth resistor value. This is the output voltage.

[0011] In the above power supply voltage regulation circuit, R1=R2, R3=R4, and R5=R6.

[0012] In the above power supply voltage regulation circuit, the first operational amplifier is a current feedback operational amplifier.

[0013] In the above power supply voltage regulation circuit, the voltage amplification circuit includes a second operational amplifier, a third operational amplifier, and a feedback resistor. The third operational amplifier and the feedback resistor form the negative feedback network of the second operational amplifier.

[0014] In the above power supply voltage regulation circuit, the first digital-to-analog converter circuit in the voltage generation unit is a differential current type digital-to-analog converter circuit.

[0015] In the above power supply voltage regulation circuit, the precision control unit includes: a fourth digital-to-analog conversion circuit, a sampling voltage divider circuit, a first comparator, and a second comparator. The sampling voltage divider circuit collects the output voltage in real time and outputs it to the first comparator and the second comparator respectively. The fourth digital-to-analog conversion circuit receives a first threshold and a second threshold of voltage preset by the main controller, and converts the first threshold and the second threshold into voltage signals and inputs them into the first comparator and the second comparator respectively. The main controller adjusts the output according to the comparison result of the first comparator and the second comparator.

[0016] In the above power supply voltage regulation circuit, when the output voltage collected by the sampling circuit is higher than the first threshold, the first comparator outputs an alarm signal; when the sampled voltage is lower than the second threshold, the second comparator outputs an alarm signal; the main controller determines whether the voltage is within the allowable range based on the comparison results of the first and second comparators, and dynamically adjusts the output if it exceeds the range.

[0017] In the above power supply voltage regulation circuit, the upper and lower limit feedback units include an upper limit feedback unit and a lower limit feedback unit. The lower limit feedback unit is used to perform feedback control on the circuit zero point, and the upper limit feedback unit is used to perform feedback control on the circuit upper limit value.

[0018] In the aforementioned power supply voltage regulation circuit, the lower limit feedback unit includes: a second digital-to-analog converter circuit, a differential current-to-single-ended voltage converter circuit, a filter circuit, a voltage amplifier circuit, and a comparator. The main controller inputs the zero-point voltage digital code to the second digital-to-analog converter circuit as a calibration control signal. The digital-to-analog converter converts the digital signal into a proportional differential current, which is then converted into a voltage signal by the differential current-to-single-ended voltage converter circuit. The voltage signal is then input to the comparator after passing through the filter circuit and the voltage amplifier circuit. The comparator compares the voltage signal with the ground level deviation and feeds it back to the main controller. The main controller dynamically sets the digital code value of the zero-point voltage according to the deviation of the differential current-to-single-ended voltage converter circuit.

[0019] In the aforementioned power supply voltage regulation circuit, the upper limit feedback unit includes: a third digital-to-analog converter circuit, a differential current-to-single-ended voltage converter circuit, a filter circuit, a voltage amplifier circuit, and a comparator. The main controller inputs the upper limit voltage digital value to the third digital-to-analog converter circuit as a calibration control signal. The digital-to-analog converter converts the digital signal into a proportional differential current, which is then converted into a voltage signal by the differential current-to-single-ended voltage converter circuit. The voltage signal is then input to the comparator after passing through the filter circuit and the voltage amplifier circuit. The comparator compares the voltage with the preset reference voltage in the fourth digital-to-analog converter circuit and feeds the deviation back to the main controller. The main controller dynamically adjusts the calibration output according to the deviation.

[0020] In the above power supply voltage regulation circuit, the second, third and fourth digital-to-analog conversion circuits are all differential current type digital-to-analog conversion circuits.

[0021] The power supply voltage regulation circuit provided in this application uses a differential current-to-voltage converter and a voltage amplification circuit to linearly convert digital codes into voltage signals. A comparator-based precision calibration circuit effectively improves voltage accuracy, providing a stable and accurate voltage value for testing the VCC contact voltage of smart cards over a long period. This helps solve the problems of misjudgment and missed judgment in conventional smart card testing regarding voltage withstand quality. It supports refined parameter testing, provides accurate data support for card design optimization, and greatly improves the reliability of smart card voltage test results. The voltage generation unit of this application generates output voltage through a multi-level adjustable gain architecture, achieving a high-precision linear mapping from digital signals to output voltage. The precision calibration unit achieves high-precision adjustment of the output voltage through closed-loop control. The upper and lower limit feedback unit eliminates the influence of temperature drift on the circuit zero point through closed-loop feedback, significantly improving the stability and accuracy of the output voltage. Attached Figure Description

[0022] Various other advantages and benefits of this application will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0023] Figure 1 The figure shows a schematic diagram of the power supply voltage regulation circuit according to an embodiment of this application.

[0024] Figure 2 The figure shows a circuit diagram of the power supply voltage regulation circuit according to an embodiment of this application.

[0025] Figure 3 The figure shows a circuit diagram of the differential current to single-ended voltage circuit according to an embodiment of this application.

[0026] Figure 4 The diagram illustrates a common voltage amplifier circuit in this field.

[0027] Figure 5 The figure shows a circuit diagram of a voltage amplifier circuit according to an embodiment of this application.

[0028] Figure 6 The illustration shows the embodiments described in this application. Figure 4 and Figure 5 The equivalent two-terminal network diagram of the voltage amplifier circuit described above. Figure 7 The figure shows a circuit diagram of the accuracy calibration unit described in an embodiment of this application. Detailed Implementation

[0029] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0030] Since different contact smart cards support different voltages, and to cover voltage tolerance testing, abnormal scenario simulation, and compatibility with non-standard cards and future devices, high requirements are placed on the resolution, dynamic range, and accuracy of the contact smart card power supply circuit. To meet the performance specifications for smart card C1 contact (voltage contact) testing, this application designs an adjustable accuracy wide-range power supply voltage regulation circuit, which includes a voltage generation unit. The main controller controls the differential DAC chip to output differential current, and then the voltage generation unit converts the current into a single-ended voltage output and linearly amplifies it. This method greatly improves output stability. Accuracy is ensured by sampling the output voltage and feeding it back to the controller through an accuracy calibration unit. To address the problem of unstable power supply voltage over long periods, an accuracy calibration circuit and upper and lower limit feedback control circuits are used to ensure the stability of the power supply voltage under prolonged overvoltage and heating conditions.

[0031] according to Figure 1 As shown, the device of the present invention mainly includes a main controller, a voltage generation unit, and a precision calibration unit. In some embodiments, it also includes an upper limit control unit and a lower limit control unit. The main controller is generally an FPGA controller, which is connected to the voltage generation unit, the precision calibration unit, the upper limit control unit, and the lower limit control unit, respectively, and is used to send and receive control signals or data signals.

[0032] The voltage generation unit receives signals from the main controller and generates an output voltage. This unit consists of a first digital-to-analog converter (DAC1), a differential current-to-single-ended voltage converter, and a voltage amplifier circuit. The first DAC1 uses a high-performance 12-bit differential current output DAC, characterized by low noise and high resolution. The differential current-to-single-ended voltage converter converts the differential current output from DAC1 into a single-ended voltage, which is then amplified by the subsequent voltage amplifier circuit and output to the VCC contact of the smart card. This provides the card with a low-ripple, high-resolution, dynamically adjustable power supply, while also offering considerable current output capability.

[0033] In one specific embodiment, the voltage generating unit comprises three parts: a first digital-to-analog converter circuit, a differential current-to-single-ended voltage converter circuit, and an improved in-phase voltage amplifier circuit.

[0034] The first digital-to-analog converter (DAC1) is a differential current digital-to-analog converter. As the first-stage circuit of the voltage generation unit, it is a crucial interface module between the digital back-end and the analog front-end, completing the signal conversion and reconstruction from the digital domain to the analog domain. Its performance determines the voltage resolution, output voltage accuracy, and rise time of the adjustable power supply. Based on the required power supply voltage amplitude of 0~10 V and output resolution of 5 mV as described in this application, the resolution N of DAC1 can be obtained and determined by the following formula. (Formula 1) From Formula 1, we can obtain N >10. As the primary circuit of this unit, DAC1's errors will determine the performance of the entire circuit. The error performance of DAC1 mainly includes Differential Nonlinearity (DNL) and Integral Nonlinearity (INL). DNL reflects the deviation between the actual step and the ideal step between adjacent codes, directly affecting the local linearity of the output signal; INL represents the global cumulative deviation between the actual transmission curve and the ideal straight line, directly determining the error range of the output voltage. The superposition of these two will lead to a systematic shift and local distortion of the output signal amplitude.

[0035] Differential current signals are used throughout the circuit design. While they typically offer good anti-interference capabilities, they are difficult to process. Therefore, it is necessary to convert the differential current signal output from DAC1 into a single-ended voltage signal. When a low DC frequency response is required, a differential current-to-single-ended voltage circuit structure is needed. This is achieved by connecting an operational amplifier as a differential-to-single-ended converter to obtain a single-ended output. This application employs this method, specifically as follows: Figure 3 As shown.

[0036] according to Figure 3As shown in the differential current to single-ended voltage circuit diagram, the differential current to single-ended voltage circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a first operational amplifier. Specifically: the fourth resistor is connected between the first output terminal of the first digital-to-analog converter (DAC) and the inverting input terminal of the first operational amplifier; the third resistor is connected between the second output terminal of the first DAC and the non-inverting input terminal of the first operational amplifier; the first terminal of the first resistor is connected between the second output terminal of the first DAC and the third resistor, and the second terminal of the first resistor is grounded; the first terminal of the second resistor is connected between the first output terminal of the first DAC and the fourth resistor, and the second terminal of the second resistor is grounded; the first terminal of the fifth resistor is connected between the third resistor and the non-inverting input terminal of the first operational amplifier, and the second terminal of the fifth resistor is grounded; the first terminal of the sixth resistor is connected between the fourth resistor and the inverting input terminal of the first operational amplifier, and the second terminal of the sixth resistor is connected to the output terminal of the first operational amplifier.

[0037] Based on the characteristics of the virtual short and continuous discontinuity of an ideal operational amplifier and the superposition law, we have: when When used alone, for: (Formula 2) when When used alone, for: (Formula 3) According to the superposition theorem, the final... for: (Formula 4) The formula for converting differential current into voltage using the differential current to single-ended voltage circuit is as follows: (Formula 5) In the above formula, the The current value output from the second output terminal of the first digital-to-analog converter circuit is the value of the current output. R1 represents the current value output from the first output terminal of the first digital-to-analog converter circuit, R2 represents the first resistor value, R3 represents the third resistor value, R4 represents the fourth resistor value, R5 represents the fifth resistor value, and R6 represents the sixth resistor value. This is the output voltage.

[0038] In one specific implementation, when R1=R2, R3=R4, R5=R6, the above equation can be rearranged to obtain: (Formula 6) As shown in Equation 6, this circuit amplifies the differential current output by the DAC. After rearranging according to Equation 5, considering the common-mode input signal, the differential-mode input signal is... Then we have: (Formula 7) Substituting Formula 7 into Formula 5, we get... (Formula 8) Simplifying Formula 8, we get: (Formula 9) Let Formula 9 be: (Formula 10) In Formula 10, Acm is the common-mode gain and Adm is the differential-mode gain. The calculated common-mode rejection ratio (CMRR) is shown in the following formula: (Formula 11) Therefore, when R1=R2, R3=R4, and R5=R6, the denominator of formula 11 is 0, and the common-mode rejection ratio of the circuit tends to infinity, which ensures the suppression of noise and common-mode signals and improves the stability of the circuit.

[0039] In the circuit described in this application, the coordinated design of the pre-stage differential current-to-single-ended voltage circuit and the voltage amplifier circuit is the core component of the voltage generation unit. The pre-stage differential current-to-single-ended voltage circuit essentially converts the input differential current signal into a single-ended voltage signal through a feedback network composed of an operational amplifier and low-temperature coefficient resistors. The subsequent voltage amplifier circuit mainly uses a resistor network to set the gain, amplifying the millivolt-level voltage signal output from the differential current-to-single-ended voltage circuit with low distortion to match the load voltage requirements and provide sufficient output current to drive the load. This application employs an improved voltage amplifier circuit.

[0040] A typical integrated operational amplifier can be used to form a voltage amplifier circuit, such as... Figure 4 As shown, the signal is input from the non-inverting input, and the amplification factor is determined by the feedback network and R. RF acts as a negative feedback network, ensuring that the op-amp operates in a linear state. Its output can be expressed by the following equation: (Formula 12) Among them, R-generation (R8+R9), R F Equivalent to R10.

[0041] Figure 5A circuit diagram of the improved voltage amplifier circuit described in this application is shown. The voltage amplifier circuit used in this application includes a second operational amplifier, a third operational amplifier, and a feedback resistor. The third operational amplifier and the feedback resistor form the negative feedback network of the second operational amplifier. This application improves the feedback network of the circuit without changing the voltage amplification factor, thereby increasing the circuit's load-driving capability, reducing errors under the same input conditions, and increasing the output voltage and current.

[0042] In the embodiments described in this application, the improved voltage amplifier circuit is as follows: Figure 5 As shown, the third operational amplifier B forms a voltage follower instead of the ordinary feedback resistor network, and together with the feedback resistor R10, they form a negative feedback network. Since the second operational amplifier A introduces negative feedback, based on the characteristics of "virtual short" and "virtual open," it can be concluded that... Figure 4 The ordinary voltage amplifier circuit shown and Figure 5 The input and output expressions of the voltage amplifier circuit used in this application are consistent.

[0043] Figure 4 and Figure 5 The voltage amplifier circuits shown can all be equivalent to the two-terminal network shown in Figure 6. Figure 4 The resistances of the equivalent two-terminal network of the circuit shown are RA and RA10, respectively. Figure 5 The equivalent resistances of the voltage amplifier circuit shown are RB and RB10. Let the output resistance of the integrated operational amplifier be Ro and the input resistance be Ri. Since the input resistance of the integrated operational amplifier tends to infinity and the output resistance tends to zero, according to the voltage amplifier circuit structure in Figure 4, its output resistance RAS is: And according to Figure 5 The voltage amplifier circuit structure shown has an output resistance RBS: In summary, since Ri >> (R8 + R9) >> RA10 = RB10 = R10, then RAS ≈ RBS ≈ R10; and Figure 4 In the equivalent two-terminal network of the voltage amplifier circuit, RA is less than Figure 5 In the equivalent two-terminal network of a medium-voltage amplifier circuit, RB (i.e., RA) draws a larger current from US, resulting in greater energy loss. Furthermore, given the same US, the improved circuit... Figure 5 The voltage amplifier circuit shown achieves nearly equal internal resistance, higher output voltage and current, and improved driving capability. Therefore, the contact-type smart card power supply unit designed in this paper has an adjustable range of 0~9.94 V and a theoretical resolution of 4.88 mV.

[0044] The power supply voltage regulation circuit described in this application also includes a precision calibration unit to achieve closed-loop high-precision voltage output.

[0045] In one embodiment of this application, the accuracy calibration unit includes: a fourth digital-to-analog converter circuit, a sampling voltage divider circuit, a first comparator, and a second comparator. The sampling voltage divider circuit acquires the output voltage in real time and outputs it to the first comparator and the second comparator respectively. The fourth digital-to-analog converter circuit receives a first threshold and a second threshold of voltage preset by the main controller, and converts the first threshold and the second threshold into voltage signals and inputs them into the first comparator and the second comparator respectively. The main controller adjusts the output according to the comparison results of the first comparator and the second comparator.

[0046] Figure 7 A circuit diagram of the accuracy calibration unit described in this application is shown.

[0047] In this application, the main controller outputs a digitally encoded value as an output voltage signal through a digital-to-analog converter (DAC). Ideally, the DAC output voltage or current should have an ideal linear relationship with the input value. However, in practical applications, the DAC will inevitably be affected by various external factors, resulting in errors. Temperature is a significant factor; therefore, the DAC output will drift with temperature changes, causing a non-linear relationship between the input and output. To eliminate the influence of ambient temperature, this application employs a precision calibration unit to calibrate the output voltage, thereby eliminating the impact of errors.

[0048] The accuracy calibration unit described in this application uses a fourth digital-to-analog converter circuit (DAC4) to control the entire unit. The main controller presets two reference voltage encoding values ​​(i.e., the first threshold and the second threshold) through DAC4 based on the input encoding D0. The two comparator circuits ensure that the output voltage value is maintained near the set value by comparing it with the output voltage after sampling and voltage division and the preset value. The size of the control comparison window reaches the millivolt level accuracy (within 9 millivolts).

[0049] like Figure 7As shown, the core mechanism of the precision calibration unit described in this application is as follows: The main controller FPGA dynamically sets the reference voltage first threshold code D1 and the second threshold code D2 of the comparator through the dual-channel DAC4, and converts the encoded values ​​into voltage values ​​U1 and U2, respectively, which are then input into the first and second comparators. The sampling voltage divider circuit simultaneously inputs the sampled value U0 of the output voltage of the voltage generation unit into the first and second comparators for window comparison. Only when the output voltage U0 is between U1 and U2 will the two comparators output different status signals (one high and one low). At this time, the FPGA adjusts the output of DAC1 in real time, so that the system ultimately stabilizes the output voltage UOUT precisely within the voltage window range formed by U1 and U2.

[0050] The circuit needs to determine the comparison window in real time, and the final comparison output results are as follows: (Formula 13) (Formula 14) The result of the output voltage obtained after sampling and voltage division is: (Formula 15) In the above formula, U0 is the output voltage, which is output to the contact pins of the test smart card as the power supply voltage. It is the same as the output voltage of the voltage generation unit. To be precise, U0 is the output voltage value sampled from the output voltage of the voltage generation unit. In this embodiment, DAC 4 is a serial 16-bit digital-to-analog converter circuit. The main controller inputs a 16-bit code to DAC 4, where the first four bits are used to define the output channel, and the last 12 bits are the input code value of D1 or D2.

[0051] In Formula 15, D0 is the decimal representation of the twelve-bit input code sent by the main controller to DAC1, and U0 is the output voltage value obtained by sampling and dividing the output voltage of the voltage generation unit from the voltage divider circuit. Therefore, it can be analyzed that when C1 = C2 = C0 (C... x Since the main influencing factor of parameters in different circuits is the resistance value, when D2=D0=D1-1, a narrow voltage window, i.e. a comparison window, is formed with the D0 input as the center, which greatly improves the accuracy level.

[0052] According to one embodiment of this application, the power supply voltage regulation circuit further includes an upper limit feedback unit and a lower limit feedback unit. The circuit structures of the upper limit feedback unit and the lower limit feedback unit are basically the same, both including a digital-to-analog converter circuit, a differential current to single-ended voltage circuit, a filter circuit, a voltage amplifier circuit, and a comparator. In the lower limit feedback unit, the main controller inputs the zero-point voltage digital value to the digital-to-analog converter circuit DAC2 as a calibration control signal. The digital-to-analog converter converts the digital signal into a proportional differential current and outputs it to the voltage conversion circuit, converting it into a voltage signal. The voltage signal is then input to the comparator after passing through the filter circuit and the voltage amplifier circuit. The comparator compares the deviation between the ground voltage and the circuit voltage and feeds it back to the main controller. The main controller dynamically adjusts the digital code value of the calibration digital-to-analog converter circuit according to the deviation until the comparator determines that the deviation is zero. At this time, the digital value of the digital-to-analog converter circuit is locked as the reference zero point.

[0053] In practical applications, the circuit voltage output may exceed the set range at the beginning or during use due to improper reset, component aging, or ambient temperature. In this case, the accuracy control circuit cannot control the voltage output well due to the range limitation of the comparator. In addition, the actual output voltage range of the DAC is -10~+10V. In order to prevent the output of negative voltage, the upper and lower limit feedback units are designed.

[0054] When the system enters the initialization phase, it first sends the differential current to the differential current-to-single-ended voltage converter circuit through the digital encoding of the preset zero-point voltage value of DAC2 in the upper and lower limit feedback unit. Then, after passing through the filtering circuit, the processed voltage is input into the voltage amplifier circuit and amplified by the set fixed gain value. Finally, it is compared with the ground voltage and output back to the FPGA main controller. This is used to detect environmental parameters and redetermine the reference zero point, generating a corresponding 12-bit digital code in the system. Subsequently, based on this code, the preset upper voltage limit value in DAC4 is re-determined. At the same time, the target output voltage is calculated and converted into a 12-bit control signal, which drives the load through DAC1, the differential current-to-single-ended voltage converter in the voltage generation unit, and the voltage amplifier circuit to finally output a stable voltage value. In this way, it is ensured that the voltage outside the range will not be generated due to environmental factors in the initial stage.

[0055] The upper and lower limit feedback unit includes an upper limit feedback circuit and a lower limit feedback circuit. Specific implementation methods are as follows: Figure 2 As shown.

[0056] The main working principle of the lower limit feedback circuit is as follows: Figure 2As shown, when entering the working stage, in order to prevent the generation of negative voltage, this application uses DAC2 in the digital encoding input lower limit feedback circuit set by the main controller for voltage comparison. Similarly, it passes through a differential current to single-ended voltage circuit and a filtering circuit. In order to ensure that the voltage is within the comparator comparison voltage range, a parallel resistor is added after the filtering circuit for voltage division and then voltage amplification, so that the output voltage range is near the comparator's optimal comparison voltage value. Then it is compared with the ground voltage. The final comparison result is sent back to the FPGA main controller through a voltage follower. The main controller makes a judgment based on the result and performs addition and subtraction control on the twelve-bit digital signal to keep the final output result above the ground voltage.

[0057] The upper limit circuit principle and circuit diagram are basically the same as the lower limit feedback circuit. The main difference is that it compares the upper limit voltage value in the reference voltage set by the 16-bit serial data of the DAC4 control output with the comparator. The final comparison result is sent back to the FPGA controller. After the data is sent back to the main controller, the main controller controls the 12-bit input digital code of DAC1 according to the comparison result, and controls the final voltage output to ensure that the output voltage is always within the set upper and lower limits.

[0058] Example 1: The working principle of the circuit described in this application is illustrated below through specific embodiments: If a 5V voltage needs to be applied to the smart card contacts, the following is the operation process of the power supply voltage regulation circuit described in this application.

[0059] 1. Lower Bound Feedback Unit After the power supply voltage regulation circuit starts, it first calibrates the ground voltage. At this time, the lower limit feedback unit works, and the main controller sends the code corresponding to the default 0V to DAC2, for example: 2048. At this time, the comparator in the lower limit feedback unit compares the collected output voltage with the result and finds that the comparator output is 1, indicating that the actual ground potential is higher than the initial setting. At this time, the main controller increments the count by 1, and then the DAC2 code is incremented by 1. This process is repeated until the comparator output flips (becomes 0), at which point the counting stops. For example, if the main controller counts 3, the ground potential calibration ends, indicating that the actual potential is 3 units higher than our set value due to environmental factors. All codes sent by the main controller will be incremented by 3 by default to balance the environmental influence.

[0060] 2. Voltage generation unit The main controller sends the digital code D0 corresponding to 5V to DAC1 (e.g., 5V corresponds to code D0=3057). Since the lower limit feedback unit has already calibrated the code to zero potential, the code sent by the main controller should be incremented by 3. Therefore, the output code corresponding to 5V is D0=3060. The main controller outputs the twelve-bit digital code 1011 1111 0100 corresponding to D0 to DAC1. DAC1 outputs the corresponding differential current IA-IB=(2D0-4095) / 4096=7.58 mA based on the digital code value. The differential current is converted to voltage to obtain the output voltage U=7.58*90=682.25mV. After passing through a voltage amplifier circuit with an amplification factor of approximately 7.3, the final output voltage U is obtained. OUT =5000mv.

[0061] 3. Precision calibration unit As time progresses, the device is affected by rising temperature or other factors, causing the output voltage to slowly increase or decrease. At this point, the accuracy calibration circuit begins to operate. Simultaneously, the main controller sends a 12-bit parallel digital code D0 corresponding to the 5V voltage to DAC1, while simultaneously inputting two 16-bit serial digital codes to DAC4. The first four bits of the 16-bit serial digital code represent the channel value, and the last 12 bits represent the digital code values ​​D1 and D2 corresponding to the point voltage, where D2 = D0 = D1 - 1. DAC4 outputs two voltage values ​​from the two channels. The relationship between the digital code of DAC4 and the output voltage is: U = [2.5 * (2D - 4096)] / 4096). These values ​​are then amplified by C1 and C2 times by the voltage amplifier circuit to obtain two reference voltage values ​​U1 and U2. At the same time, the sampling voltage divider circuit collects the output voltage U sampled from the output voltage. OUT The voltage divider yields U0. At this point, the three voltage values ​​are as shown in formulas 13, 14, and 15, and their magnitudes should be in the following relationship: U1≈2.5*2026 / 4096>U0≈2.5*2025 / 4096>U2≈2.5*2024 / 4096 If the voltage U0 sampled by the sampling voltage divider circuit slowly rises above U1, comparator 1 changes from high to low. At this time, the main controller receives a signal and decrements D0 by 1. D1 and D2 remain unchanged, and the magnitude relationship returns to U1>U0>U2. If the voltage U0 sampled by the sampling voltage divider circuit slowly falls below U2, comparator 2 changes from high to low. At this time, the main controller receives a signal and increments D0 by 1. D1 and D2 remain unchanged, and the magnitude relationship returns to U1>U0>U2, thus ensuring that the output voltage signal is maintained within a certain range.

[0062] 4. Upper Limit Feedback Unit When a large voltage is directly input without calibration due to various reasons such as the circuit not being reset, the initial output voltage may directly exceed 10V and fluctuate violently. In this case, although the accuracy calibration circuit will maintain the voltage, it cannot keep decreasing. At this time, the upper limit feedback unit needs to tell the main controller to reduce D0 by comparing the circuit voltage upper limit value preset by DAC4 (such as 9V voltage) so that the output voltage returns to near the safe voltage.

[0063] As can be seen from the above examples, the voltage generation unit of the power supply voltage regulation circuit described in this application can linearly convert digital codes into voltage signals. The accuracy calibration unit can eliminate errors in the circuit, so that the output voltage is stabilized within the preset value window, thereby improving the output voltage accuracy. The lower limit feedback unit can adjust and control the zero point of the circuit, and the upper limit feedback unit can effectively prevent the output voltage from exceeding the upper limit safety range due to factors such as abnormal reset, sudden device failure, or extreme environmental interference, ensuring that the circuit can quickly return to the set range under drastic fluctuation scenarios. The entire circuit works in concert, effectively improving the accuracy and stability of the voltage output.

[0064] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not restrict the application from being implemented using the specific details described above.

[0065] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0066] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0067] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0068] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A power supply voltage regulation circuit for testing a contact smart card, characterized by, include: A voltage generating unit, which is connected to the main controller, is used to convert the digital signal sent by the main controller into an output voltage signal; A precision calibration unit acquires the output voltage of the voltage generation unit, compares it with the reference voltage set by the main controller, and transmits the comparison result to the main controller. as well as The main controller is connected to the voltage generation unit and the accuracy calibration unit, and is used to adjust the voltage control signal output to the voltage generation unit based on the comparison result fed back by the accuracy calibration unit.

2. The power supply voltage regulation circuit of claim 1, wherein, The power supply voltage regulation circuit further includes an upper and lower limit feedback unit, which is connected to the main controller and is used to receive upper and lower limit control signals sent by the main controller to perform feedback control on the upper and lower limits of the circuit voltage.

3. The supply voltage regulation circuit of claim 1, wherein, The voltage generating unit includes: The circuit comprises a first digital-to-analog converter, a differential current-to-single-ended voltage converter, and a voltage amplifier circuit. The first digital-to-analog converter converts the digital signal of the main control input into a proportional differential current and outputs it to the differential current-to-single-ended voltage converter. The differential current-to-single-ended voltage converter converts the differential current into an intermediate voltage and outputs it to the voltage amplifier circuit. The voltage amplifier circuit amplifies the intermediate voltage to obtain the output voltage.

4. The power supply voltage regulation circuit according to claim 3, wherein, The differential current-to-single-ended voltage circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a first operational amplifier, wherein: The fourth resistor is connected between the first output terminal of the first digital-to-analog converter circuit and the inverting input terminal of the first operational amplifier. The third resistor is connected between the second output terminal of the first digital-to-analog converter circuit and the positive input terminal of the first operational amplifier; The first end of the first resistor is connected between the second output terminal of the first digital-to-analog converter circuit and the third resistor, and the second end of the first resistor is grounded; The first end of the second resistor is connected between the first output terminal of the first digital-to-analog converter circuit and the fourth resistor, and the second end of the second resistor is grounded. The first end of the fifth resistor is connected between the third resistor and the positive input terminal of the first operational amplifier, and the second end of the fifth resistor is grounded. The first end of the sixth resistor is connected between the fourth resistor and the inverting input of the first operational amplifier, and the second end of the sixth resistor is connected to the output of the first operational amplifier.

5. The power supply voltage regulation circuit according to claim 4, wherein, The formula for converting differential current into voltage using the differential current to single-ended voltage circuit is as follows: ， in, The current value output from the second output terminal of the first digital-to-analog converter circuit is [value]. R1 represents the current value output from the first output terminal of the first digital-to-analog converter circuit, R2 represents the first resistor value, R3 represents the third resistor value, R4 represents the fourth resistor value, R5 represents the fifth resistor value, and R6 represents the sixth resistor value. This is the output voltage.

6. The power supply voltage regulation circuit according to claim 5, wherein, R1=R2, R3=R4, R5=R6.

7. The power supply voltage regulation circuit according to claim 4, wherein, The first operational amplifier is a current feedback type operational amplifier.

8. The power supply voltage regulation circuit according to claim 3, wherein, The voltage amplifier circuit includes a second operational amplifier, a third operational amplifier, and a feedback resistor. The third operational amplifier and the feedback resistor form the negative feedback network of the second operational amplifier.

9. The power supply voltage regulation circuit according to claim 3, wherein, The first digital-to-analog converter circuit in the voltage generation unit is a differential current-type digital-to-analog converter circuit.

10. The power supply voltage regulation circuit according to claim 1, characterized in that, The accuracy calibration unit includes: a fourth digital-to-analog converter circuit, a sampling voltage divider circuit, a first comparator, and a second comparator. The sampling voltage divider circuit acquires the output voltage in real time and outputs it to the first comparator and the second comparator respectively. The fourth digital-to-analog converter circuit receives a first threshold and a second threshold of voltage preset by the main controller and converts the first threshold and the second threshold into voltage signals, which are then input into the first comparator and the second comparator respectively. The main controller adjusts the output according to the comparison results of the first comparator and the second comparator.

11. The power supply voltage regulation circuit according to claim 2, wherein, The upper and lower limit feedback units include an upper limit feedback unit and a lower limit feedback unit. The lower limit feedback unit is used to perform feedback control on the circuit zero point, and the upper limit feedback unit is used to perform feedback control on the circuit upper limit value.

12. The power supply voltage regulation circuit according to claim 11, wherein, The lower limit feedback unit includes: a second digital-to-analog converter circuit, a differential current to single-ended voltage converter circuit, a filter circuit, a voltage amplifier circuit, and a comparator. The main controller inputs the zero-point voltage digital code to the second digital-to-analog converter circuit as a calibration control signal. The digital-to-analog converter converts the digital signal into a proportional differential current, which is then converted into a voltage signal by the differential current to single-ended voltage converter circuit. The voltage signal is then input to the comparator after passing through the filter circuit and the voltage amplifier circuit. The comparator compares the deviation between the voltage signal and the ground level and feeds it back to the main controller. The main controller dynamically sets the digital code value of the zero-point voltage according to the deviation.

13. The power supply voltage regulation circuit according to claim 11, wherein, The upper limit feedback unit includes: a third digital-to-analog converter circuit, a differential current-to-single-ended voltage converter circuit, a filter circuit, a voltage amplifier circuit, and a comparator. The main controller inputs the upper limit voltage digital code to the third digital-to-analog converter circuit as a calibration control signal. The digital-to-analog converter converts the digital signal into a proportional differential current, which is then converted into a voltage signal by the differential current-to-single-ended voltage converter circuit. The voltage signal is then input to the comparator after passing through the filter circuit and the voltage amplifier circuit. The comparator compares the voltage with the preset reference voltage in the fourth digital-to-analog converter circuit and feeds it back to the main controller. The main controller dynamically adjusts the calibration output according to the deviation.

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