Current integrating charge source

Abstract

This invention relates to a current-integrating charge source, comprising a standard voltage source, a transconductance amplifier, a programmable switch, and a controller. It employs a constant current-time integration method to achieve the output of a DC constant charge source. The change in output charge is achieved by controlling the output time of the current. During the output process, the current is a constant current with feedback, and the output charge increases linearly with time. No energy storage device is required in the key components, and no charging or discharging is needed during the charge output process. The output is rapid and poses no safety hazards. The current source is a closed-loop circuit with feedback, which has virtually no requirements on the load impedance. It is applicable to various types of charge meters and loads, has a wide range of applicable loads, is simple and convenient to operate, and has high accuracy.

Description

Technical Field

[0001] This invention relates to the fields of electronics and circuit technology, and specifically to a current-integrating charge source. Background Technology

[0002] Electric charge, or simply charge, is the amount of electrical charge carried by an object. Its unit is the coulomb (symbol C). Electric charge is divided into positive charge and negative charge.

[0003] The charge source provides a standard charge output for the metrological verification of charge amplifiers and charge testing equipment, and is an important standard device in the electrostatic protection system.

[0004] The capacitance C of a capacitor is the ratio of the charge Q on the capacitor to the potential difference U between the capacitor's plates, i.e. Once a capacitor is selected, its capacitance value is fixed. Aside from the predetermined temperature coefficient, humidity coefficient, and aging factor, the capacitance value can be conveniently and accurately measured in the laboratory using a bridge circuit. According to the definition of capacitance, the amount of charge Q in a charge source is directly proportional to the capacitance value C and the voltage U across the capacitor. Once the capacitance is determined, the capacitance value C remains constant, and the amount of charge Q depends only on the voltage between the capacitor's plates.

[0005] Based on the definition of a capacitor, a capacitor voltage-type charge source can be made. Once the capacitor is manufactured, its capacitance value is determined, and the amount of charge stored in the capacitor is proportional to the voltage across the capacitor.

[0006] Electric current refers to the directional flow of electric charge. The magnitude of electric current is the amount of charge passing through a cross-section of a conductor per unit time; the amount of charge passing through one coulomb per second is called one ampere. Therefore, when the output current is constant, the amount of output charge is only related to the output duration.

[0007] According to the definition of current, once the output current is determined, controlling the current output time can conveniently control the amount of output charge. This is the principle of a current-time type charge source.

[0008] The current-integrating charge source outputs a constant current, and the charge output is linearly related to time. The longer the output time, the larger the output charge, and the charge output is uniform, making it easy to control.

[0009] Existing charge standard sources on the market, such as Kistler's 5393A, are capacitor-voltage type charge sources, which output standard charges by controlling the voltage value on a standard capacitor. Meanwhile, Chinese patent CN103178708A, "Static Charge Source and Calibration Method Thereof," proposes that static charge sources are also based on the principle of capacitor voltage, with both the controllable voltage source and the capacitor located in the feedback loop of the operational amplifier, and the controllable voltage source being a floating ground design.

[0010] However, the existing technology still has the following problems:

[0011] (1) Charging is required before outputting charge. The capacity of a capacitor voltage-type charge source is affected by the capacitor's capacitance and its voltage rating, resulting in a limited charge output. The output speed is influenced by the load impedance and the capacitor's inherent characteristics, and the charge is not output at a uniform rate. A capacitor voltage-type charge source is an energy storage type; it requires prior charging to store charge before outputting. After the stored charge is depleted, recharging is necessary to continue outputting charge. The maximum output charge depends on the capacitor's capacitance and voltage rating.

[0012] (2) Safety requires special attention. Capacitor-type charge sources must be equipped with a discharge circuit to release any residual charge on the capacitor after output is complete, preventing interference with subsequent measurements or damage to operators and equipment due to the capacitor remaining energized during shutdown. After use, the output of the capacitor-type charge source must be grounded to create a current path, discharging the charge on the capacitor so that the voltage on the capacitor is 0V, eliminating any voltage difference between the capacitor and ground. This prevents electric shock to operators or damage to the equipment due to capacitor discharge during reuse or handling.

[0013] (3) High load requirements and impedance matching are required. If the capacitor voltage-type charge source is an open-loop circuit, the capacitance value of the capacitor integrating charge measurement device must be much larger than the capacitance in the charge source; otherwise, capacitive voltage division will occur, and the expected charge value cannot be output. Secondly, there must always be a voltage difference between the charge source and the load during charge output, and the sign of the voltage difference must be consistent with the sign of the charge source. If the voltage difference between the charge source and the load is zero, no charge will be output; when the signs of the voltage difference between the output charge source and the load are opposite, the charge flows from the load to the charge source, causing backflow into the charge source, which fails to achieve the expected charge source function.

[0014] (4) Nonlinear charge output. When a capacitor voltage-type charge source outputs charge, the voltage across the capacitor decreases as the charge is output, and the voltage difference between the capacitor and the load gradually decreases. The slope of the entire amplification curve shows a trend of first being large and then small.

[0015] (5) High-accuracy capacitive voltage-type charge sources have complex structures and operations. Capacitive charge sources have complex structures, such as... Figure 1As shown, the system includes a charging voltage source, a discharge circuit, a standard capacitor, a standard voltmeter for real-time measurement of the voltage across the standard capacitor, and a relay group for function switching. The relay group can also be a non-physical entity, connected manually by the operator changing the connecting wires. The workflow is as follows: First, the voltage source charges the standard capacitor; second, the voltage value U1 on the capacitor is recorded; third, the charge is output; fourth, the voltage value U2 on the capacitor is recorded; fifth, the standard value of the output charge is Q = C × (U1 - U2); sixth, the two ends of the standard capacitor are connected to the discharge channel, and the voltage value on the standard voltmeter is observed in real time until the voltage reading reaches 0. Summary of the Invention

[0016] To address the problems existing in the prior art, the present invention proposes a current-integrating charge source.

[0017] The current-integrating charge source of this invention includes a standard voltage source, a transconductance amplifier, a programmable switch, and a controller.

[0018] Furthermore, the programmable switch is a single-pole double-throw switch, with the moving end connected to the input terminal of the transconductance amplifier, the first stationary end connected to the output of the standard voltage source, and the second stationary end grounded.

[0019] Furthermore, the default state of the moving terminal of the programmable switch is to ground the transconductance amplifier through the second stationary terminal, and the controller is used to output a switch control signal to control the position of the programmable switch.

[0020] Furthermore, the transconductance amplifier includes a first resistor, a second resistor, a third resistor, a fourth resistor, a feedback resistor, a first operational amplifier, a second operational amplifier, and a third operational amplifier.

[0021] Furthermore, the circuit structure of the transconductance amplifier is as follows: the high and low ends of the input voltage are connected to the positive and negative input terminals of the first operational amplifier through the second and third resistors, respectively. The output terminal of the first operational amplifier is connected to the feedback resistor and also to the positive input terminal of the second operational amplifier. The negative input terminal and output terminal of the second operational amplifier are shorted and connected in series with the fourth resistor, and then connected to the negative input terminal of the first amplifier. The other end of the feedback resistor is connected to the positive input terminal of the third operational amplifier. The negative input terminal and output terminal of the third operational amplifier are shorted and connected in series with the first resistor, and then connected to the positive input terminal of the first amplifier. The input voltage is applied across the feedback resistor after being divided by the resistors. The first and fourth resistors have the same resistance value, and the second and third resistors have the same resistance value.

[0022] Furthermore, the principle of the transconductance amplifier is as follows:

[0023] The input voltage is V, which is divided by various resistors, and then passes through various operational amplifiers and a feedback resistor to obtain a constant current I. o Output, let R2 / R1 = R3 / R4 = k, then the actual load on the feedback resistor R f Voltage V on o =V / k, then the output constant current I o The current value across the feedback resistor is:

[0024]

[0025] Furthermore, the charge source sets the programmable switch conduction time t and current output value I according to the required output charge Q. The setting of the current output value I specifically includes setting the voltage output value and setting the transconductance amplifier range.

[0026] Let the current output range of the standard voltage source be -I. max ~I max The minimum resolution is I res The maximum output current value is I max , let Q b As the control mode split point, when I res ≤0.01I max At that time, Q b =100s×I res Otherwise Q b =0.01s×I max .

[0027] Furthermore, the method for determining the on-time t of the programmable switch is as follows:

[0028] a. When Q > 1s × I max At that time, the output current value is I max Output time

[0029] b. When Q b ≤Q≤1s×I max At time t = 1s, the output current value in the charge source

[0030] c. When Q < Q b At that time, the output current value is 100I. res The output time is t = 0.1s.

[0031] Furthermore, the output control process of the charge source is as follows:

[0032] a. Before charge output, the programmable switch is set to the second stationary terminal conduction state, and the working state of the standard voltage source is set according to the calculated output current value I;

[0033] b. Set the programmable switch to the first stationary terminal conduction state, the charge output circuit is connected, and the output current begins. At the same time, the controller starts timing.

[0034] c. When the output time reaches the set time t, switch the programmable switch state, so that the programmable switch is in the second fixed terminal conduction state, so that the input of the transconductance amplifier is grounded, the output current becomes 0, and no more charge is output. The charge output is completed, and the output charge Q is the product of the output current I and the output time t.

[0035] The current-integrating charge source of this invention uses a constant current-time integration method to achieve the output of a DC constant charge source. The change in output charge is achieved by controlling the output time of the current. During the output process, the current is a constant current with feedback, and the output charge increases linearly with time. No energy storage device is required in the key components, and no charging or discharging is needed during the charge output process. The output is rapid and poses no safety hazards. The current source is a closed-loop circuit with feedback, which has virtually no requirements on the load impedance. It is applicable to various types of charge meters and loads, has a wide range of applicable loads, is simple and convenient to operate, and has high accuracy. Compared with the prior art, this invention has the following beneficial effects:

[0036] (1) The output charge capacity has high accuracy and good stability.

[0037] The charge source in this invention is based on a constant current source and time. The DC constant current source and time parameters are independent, and there is no mutual interference between them. Both the DC constant current source technology and the timer technology used for time setting are mature and have achieved high accuracy. Furthermore, the stability of the output charge is related to the stability of the constant current source and the stability of the output time length. Since the stability of the constant current source can reach an annual accuracy on the order of 1E-5, and the annual accuracy of the time length can reach 1E-12, the error introduced by the time accuracy is relatively negligible. That is, the stability of the output charge is only related to the stability of the constant current source; similarly, the accuracy of the output charge is only related to the accuracy of the constant current source. DC constant current source technology has been developed for many years and has achieved high accuracy and stability. In summary, the charge source in this application has high accuracy and good stability.

[0038] (2) The constant current source time-integral charge source has low internal resistance and strong adaptability to test equipment.

[0039] The internal resistance of the charge source in this invention is equivalent to that of a constant current source. Its internal resistance is very small, and there are no special requirements for the principle and input impedance of charge measurement equipment and charge amplifier. It is applicable to both capacitor-charged charge-voltage conversion devices and charge quantity testing equipment of various principles, and has a wide range of applications.

[0040] (3) Uniform charge output, suitable for dynamic charge and electrostatic charge testing equipment.

[0041] The charge source in this invention offers flexible charge output methods. Charge output can be achieved by setting a constant current and varying the output time; alternatively, it can be achieved by keeping the time constant while varying the output current value. The former is suitable for charge amplifiers or charge measuring devices where test duration is not critical, while the latter is suitable for charge amplifiers or charge measuring devices with integration time limitations.

[0042] (4) High security

[0043] In this invention, no energy storage device is involved in the charge source output process. After the charge output is completed, there is no need to worry about equipment damage or personnel injury caused by the energy storage device being charged. It is highly safe. Moreover, the output ends by terminating the signal first and then connecting the input to a determined ground potential, which reduces the error introduced by the uncertain state of the transconductance input terminal and makes the output signal reliable. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the principle of a capacitive charge source;

[0046] Figure 2 This is a schematic diagram of the principle of the current-integrating charge source according to an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the transconductance amplifier in the current-integrating charge source according to an embodiment of the present invention. Detailed Implementation

[0048] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0049] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0050] like Figure 2 As shown, this is a current-integrating charge source according to an embodiment of the present invention, which consists of four parts: a standard voltage source, a transconductance amplifier, a programmable switch K, and a controller. The programmable switch K is a single-pole double-throw switch. Its moving terminal is connected to the input terminal of the transconductance amplifier, its first stationary terminal (i.e., contact "1" of the programmable switch K in the figure, hereinafter referred to as "stationary terminal 1") is connected to the output of the standard voltage source, and stationary terminal 2 (hereinafter referred to as "stationary terminal 2") is directly grounded. The controller outputs a switch control signal to control the position of the programmable switch. The default state of the moving terminal of the programmable switch is position 2, meaning the input of the transconductance amplifier is connected to ground.

[0051] like Figure 3 As shown, this is a closed-loop transconductance amplifier in this embodiment. The high and low ends of the input voltage are connected to the positive and negative input terminals of the first operational amplifier U1 through the second resistor R2 and the third resistor R3, respectively. The output terminal of the first operational amplifier U1 is connected to the feedback resistor R. f The circuit is connected to the positive input terminal of the second operational amplifier U2. The negative input and output terminals of the second operational amplifier U2 are shorted and connected in series with a fourth resistor R4, which is then connected to the negative input terminal of the first operational amplifier U1. The feedback resistor R... f The other end is connected to the positive input terminal of the third operational amplifier U3. The negative input terminal and output terminal of the third operational amplifier U3 are shorted and connected in series with the first resistor R1, and then connected to the positive input terminal of the first amplifier. The input voltage is applied to the feedback resistor R after being proportionally divided by the resistors. f At both ends, the first resistor R1 and the fourth resistor R4 have the same resistance value, and the second resistor R2 and the third resistor R3 have the same resistance value.

[0052] The voltage V input to the transconductance amplifier from the standard voltage source is divided by various resistors, and then passed through various operational amplifiers and the feedback resistor R. f Then a constant current I was obtained o Output, let R2 / R1 = R3 / R4 = k, then the actual load on the feedback resistor R f Voltage V on o =V / k, then the output constant current I o For feedback resistor R f The current value on it, that is:

[0053]

[0054] The circuit employs a two-stage error amplifier to amplify the input differential voltage and the sampling resistor feedback voltage. This compensates for the input common-mode rejection ratio of the error amplifier, effectively controlling output linearity and improving system output performance over a wide output range. The standard voltage source output voltage range is 0–2.5V.

[0055] The on-time t of the programmable switch K and the current output value I (including setting the voltage output value and setting the transconductance amplifier range) are set according to the required output charge Q. The current output range of the standard voltage source is assumed to be -I. max ~I max The minimum resolution is I res The maximum output current value is I max , let Q b As the control mode split point, when I res ≤0.01I max At that time, Q b =100s×I res Otherwise Q b =0.01s×I max .

[0056] The method for determining the output time t is as follows:

[0057] a. When Q > 1s × Imax, the output current value is Imax, and the output time is...

[0058] b. When Qb≤Q≤1s×Imax, t=1s, the output current value in the charge source

[0059] c. When Q < Qb, the output current is 100Ires, and the output time is t = 0.1s.

[0060] The charge source output process control procedure is as follows:

[0061] a. Before outputting the charge, the programmable switch K is set to position 2, and the voltage source and current source working states are set according to the calculated output current value I;

[0062] b. Set the programmable switch to position 1. The charge output circuit is connected, and voltage is output, i.e., current is output. At the same time, the controller starts timing.

[0063] c. When the output time reaches the set time t, switch the state and set the switch to position 2, so that the input of the transconductance amplifier is grounded, the output current becomes 0, and no more charge is output. The charge output is completed.

[0064] The output charge Q is the product of the output current I and the output time t, i.e., Q = It. In this invention, the programmable switch can be a physical switch, such as a relay or analog switch, or a soft switch simulated by a controller. The above control can be achieved by controlling the output value of the current source. Specifically, the current source defaults to outputting 0A. When the charge source outputs, the controller controls the current source to output the corresponding value I, thus setting the programmable switch to position 1. After the output time reaches time t, the controller controls the current output to 0A, completing the operation of setting the programmable switch to position 2. To ensure the output charge performance, the transconductance amplifier must be a closed-loop constant current source with feedback.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A current-integrating charge source, characterized in that, Includes a standard voltage source, a transconductance amplifier, a programmable switch (K), and a controller; The programmable switch (K) is a single-pole double-throw switch, with the moving terminal connected to the input terminal of the transconductance amplifier, the first stationary terminal connected to the output of the standard voltage source, and the second stationary terminal grounded. The default state of the moving terminal of the programmable switch (K) is to ground the transconductance amplifier through the second stationary terminal. The controller is used to output a switch control signal to control the position of the programmable switch (K). The charge source sets the conduction time t of the programmable switch (K) and the current output value I according to the required output charge Q. The setting of the current output value I specifically includes two parts: setting the voltage output value and setting the transconductance amplifier range. Let the current output range of the standard voltage source be -I. max ~ I max The minimum resolution is I res The maximum output current value is I max , let Q b As the control mode split point, when I res ≤0.01I max At that time, Q b =100s×I res Otherwise Q b =0.01s×I max ; The output control process of the charge source is as follows: a. Before the charge output, the programmable switch (K) is set to the second fixed terminal conduction state, and the working state of the standard voltage source is set according to the calculated output current value I; b. Set the programmable switch (K) to the first stationary terminal on state, the charge output circuit is connected, and the output current begins. At the same time, the controller starts timing. c. When the output time reaches the set time t, switch the state of the programmable switch (K) and set the programmable switch (K) to the second fixed terminal conduction state, so that the input of the transconductance amplifier is grounded, the output current becomes 0, and no more charge is output. The charge output is completed, and the output charge Q is the product of the output current I and the output time t.

2. The current-integrating charge source according to claim 1, characterized in that, The transconductance amplifier includes a first resistor ( R 1 ), second resistor ( R 2 ), third resistor ( R 3 ), fourth resistor ( R 4 ), feedback resistor ( R f ), first operational amplifier ( U 1 ), second operational amplifier ( U 2 ) and the third operational amplifier ( U 3 ).

3. The current-integrating charge source according to claim 2, characterized in that, The circuit structure of the transconductance amplifier is as follows: The high and low ends of the input voltage pass through the second resistor respectively. R 2 ) and the third resistor ( R 3 ) connected to the first operational amplifier ( U 1 The positive and negative input terminals of the first operational amplifier () U 1 The output terminal of ) and the feedback resistor ( R f It is connected to the second operational amplifier ( ) and also connected to the second operational amplifier ( ) U 2 The positive input terminal of the first operational amplifier is connected to the second operational amplifier. U 2 The negative input terminal and the output terminal of ) are shorted together and then connected in series with a fourth resistor ( R 4 ), and then connected to the first operational amplifier ( U 1 The negative input terminal of ) and the feedback resistor ( R f The other end of the amplifier is connected to the third operational amplifier. U 3 The positive input terminal of the third operational amplifier () U 3 The negative input terminal and the output terminal of ) are shorted together and then connected in series with the first resistor ( R 1 Then it is connected to the positive input terminal of the first amplifier. The input voltage is applied to the feedback resistor after being divided by a resistor ratio. R f The two ends of ), where the first resistor ( R 1 ) and the fourth resistor ( R 4 The resistance values ​​of the first resistor and the second resistor are the same. R 2 ) and the third resistor ( R 3 The resistance values ​​are the same.

4. The current-integrating charge source according to claim 3, characterized in that, The principle of the transconductance amplifier is as follows: Input voltage is V After voltage division by various resistors, and after passing through various operational amplifiers and feedback resistors ( R f After that, a constant current output is obtained, and then... = = k Then it is actually loaded on the feedback resistor ( R f voltage on ) V o = V / k The output constant current is the feedback resistor ( R f The current value on ) is: .

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