Universal constant current source adapter based on single power supply-positive and negative symmetrical power supply converter

Abstract

The invention discloses a general constant current source adapter based on a single power supply-positive and negative symmetric power supply converter, which is characterized in that a voltage follower based on an operational amplifier can convert single power supply into positive and negative symmetric dual power supply, and output voltage of the operational amplifier A1 is subjected to power amplification through a complementary push-pull circuit to form a positive and negative symmetric power supply with relatively high power; the in-phase proportion operation circuit based on the operational amplifier can amplify the reverse constant current source control voltage and the forward constant current source control voltage, and the amplified control voltages respectively drive corresponding transistors of the complementary push-pull amplification circuit to be switched on. A positive power supply and a negative power supply of the positive and negative symmetrical dual power supplies respectively provide voltage sources for the constant current range switching circuit through the correspondingly conducted transistors, and the current passing through the constant current range switching circuit is equal to the current passing through the load RL. Through switching of the switch S1, the reverse constant current source control voltage and the forward constant current source control voltage can change the current direction passing through the load RL.

Description

Technical Field

[0001] The present invention relates to a technology for the design of a constant current source adapter, in particular to a constant current output device that can generate relatively high power. There are corresponding solutions whether the front-end circuit is powered by a single power supply or a symmetrical dual power supply of positive and negative polarities. At the same time, this constant current source adapter can also be used as a single power supply - symmetrical dual power supply converter. Background Art

[0002] In the field of electronic design, there are many electrical devices that require the supplied current (rather than voltage) to remain constant. Generally, a power supply that can provide a constant current to a load is called a constant current source.

[0003] Basic constant current source circuits can be divided into three categories according to different main components: transistor constant current sources, field effect transistor constant current sources, integrated operational amplifier constant current sources, etc.

[0004] A transistor constant current source uses a bipolar transistor as the main component. It utilizes the fact that the change in the collector voltage of the bipolar transistor has little effect on the current, and current negative feedback is adopted in the circuit to improve the constancy of the output current. The disadvantage of this current source is that the collector-emitter resistance of the transistor is generally above several tens of kiloohms. When only a few volts of working voltage is required, using this constant current source circuit, its equivalent internal resistance is very large, the power consumption is large, and the accuracy is not high.

[0005] A constant current circuit with a field effect transistor as the main component. The field effect transistor in this constant current source circuit is a JEFT, with ultra-low noise. The output current is determined by the JEFT, and the detection voltage is related to the JEFT.

[0006] For an integrated operational amplifier constant current source, in order to accurately output current, usually an operational amplifier is used as feedback, and at the same time, a field effect transistor is used to avoid the error caused by the base-emitter junction current of the bipolar transistor. This constant current source circuit can be regarded as a standard circuit for constant current sources. In addition to sufficient accuracy and adjustability, the components used are also very common, making it easy to build and debug. However, the reference voltage Vref still needs to be provided additionally.

[0007] From the above circuit introduction, it can be seen that there is a fixed pattern for constant current sources, that is, using a voltage reference to form a fixed current on a resistor. With this fixed pattern, the construction of constant current sources can be extended to all devices that can provide this "voltage reference".

[0008] The practical constant current source circuits commonly seen in textbooks often have relatively low power, and are not easy to adjust or have a narrow adjustment range.

[0009] Electronic design enthusiasts generally have a regulated power supply device with an output voltage of 30V and an output current of more than 300mA. However, a complete set of constant current source power supply devices with relatively high power is not commonly available because they are not frequently used. In fact, there is no need to purchase a complete set of constant current source power supply devices. Once a constant current source power supply is needed, a constant current source adapter can be connected to the existing regulated power supply to output a relatively high power and a constant current with an easily adjustable current value.

[0010] The power supply of a circuit is generally divided into two types: single power supply and symmetric positive and negative power supplies. Therefore, this constant current source adapter usually has two uses: First, in the existing circuit architecture, regardless of whether the circuit is powered by a single power supply or a symmetric positive and negative power supply, without changing the original power supply of the front-end circuit, the constant current source adapter can be directly connected to the front-end circuit to generate a constant current output with an adjustable current value. Second, if the front-end circuit is powered by a single power supply, but the back-end circuit is changed to a symmetric positive and negative dual power supply, the constant current source adapter can also be directly used to generate the required symmetric positive and negative dual power supply output.

[0011] The specific solution is to use a follower circuit based on an ideal operational amplifier to change the single power supply to a symmetric positive and negative dual power supply. To increase the output power of the dual power supply, a complementary push-pull amplifier circuit is connected in series to the follower circuit, and the back-end circuit is powered by the complementary push-pull amplifier circuit to output a symmetric positive and negative dual power supply. As for the constant current source formation part, a constant current source circuit based on an ideal operational amplifier is used to generate a constant current output. To increase the output power of the constant current source, a complementary push-pull amplifier circuit is also connected in series to the constant current source circuit, and the output of the constant current is provided by the complementary push-pull amplifier circuit rather than directly by the output terminal of the operational amplifier.

[0012] The advantages of the complementary push-pull amplifier circuit mainly include high efficiency and linear characteristics. This circuit structure uses two power BJT or MOSFET tubes with the same parameters, existing in the circuit in a push-pull manner, each responsible for the amplification task of the positive and negative half-cycles.

[0013] Therefore, this constant current source adapter can generate a constant current output with relatively high power, and there are corresponding solutions regardless of whether the front-end circuit is powered by a single power supply or a symmetric positive and negative dual power supply. At the same time, this constant current source adapter can also be used as a single power supply - symmetric positive and negative dual power supply converter. Summary of the Invention

[0014] The technical problem to be solved by the present invention is to provide an adapter with a simple structure, low cost, reliable use, and capable of conveniently providing a constant current for a load. Regardless of how the load changes, the output current can be constantly output, that is, the load current is independent of the load size.

[0015] To achieve the above object, the present invention provides a general constant current source adapter based on a single power supply - positive and negative symmetric power converter, which includes a +30V single power supply, a +30V single power supply working ground, a single power supply - positive and negative symmetric ±15V power generation circuit based on an operational amplifier follower, a positive and negative symmetric ±15V power supply working ground, a forward constant current source control voltage generation circuit, a reverse constant current source control voltage generation circuit, a non-inverting proportional operation circuit, a non-inverting input resistance circuit of operational amplifier A2, an operational amplifier zero adjustment circuit, a forward constant current source power supply circuit, a reverse constant current source power supply circuit, a constant current range switching circuit, and a load circuit; operational amplifier A1, resistor R1, resistor R2, capacitor C1, transistor T1, and transistor T2 constitute the single power supply - positive and negative symmetric ±15V power generation circuit based on an operational amplifier follower. The +30V single power supply is connected to pin 7 of operational amplifier A1, and the +30V single power supply working ground is connected to pin 4 of operational amplifier A1. The +15V voltage output by operational amplifier A1 is power amplified by transistors T1 and T2, and the connection point of the emitters of transistors T1 and T2 is used as the positive and negative symmetric ±15V power supply working ground; based on the positive and negative symmetric ±15V power supply working ground, a +15V power supply is output at the positive end of capacitor C2, and a -15V power supply is output at the negative end of capacitor C3; the +15V power supply is sequentially connected to the positive and negative symmetric ±15V power supply working ground through potentiometer P1, resistor R3, and resistor R4 to form the forward constant current source control voltage generation circuit, and the sliding end of potentiometer P1 is connected to the normally closed moving contact of switch S1; the -15V power supply is sequentially connected to the positive and negative symmetric ±15V power supply working ground through potentiometer P2, resistor R6, and resistor R5 to form the reverse constant current source control voltage generation circuit, and the sliding end of potentiometer P2 is connected to the normally open moving contact of switch S1; operational amplifier A2, resistor R8 of the non-inverting input resistance circuit of operational amplifier A2, resistor R7, resistor R10, transistor T3, and transistor T4 constitute the non-inverting proportional operation circuit. The static contact of switch S1 is connected to the non-inverting input terminal of operational amplifier A2 through resistor R8. When the output of operational amplifier A2 is a positive voltage, transistor T3 conducts, and the +15V power supply forms the forward constant current source power supply circuit through the C-E pole of transistor T3. When the output of operational amplifier A2 is a negative voltage, transistor T4 conducts, and the -15V power supply forms the reverse constant current source power supply circuit through the C-E pole of transistor T4; resistors R11, R12, R13, R14, and switch S2 constitute the constant current range switching circuit. Closing different moving contacts of the static contact of switch S2 can switch different output current ranges; the static contact of switch S2 is connected to the positive and negative symmetric ±15V power supply working ground through the load circuit RL; when the static contact of switch S1 closes the normally closed moving contact, the load circuit RL passes through the forward constant current source. When the static contact of switch S1 closes the normally open moving contact, the load circuit RL passes through the reverse constant current source.

[0016] The single - power supply to ±15V symmetrical positive - negative power supply generation circuit based on an operational amplifier follower. The +30V single - power supply is sequentially connected to the +30V single - power supply working ground through resistor R1 and resistor R2. Resistor R1 and resistor R2 have the same resistance value. The connection point of resistor R1 and resistor R2 is connected to the non - inverting input terminal of operational amplifier A1, providing an input voltage of +15V to the non - inverting input terminal of operational amplifier A1. The non - inverting input terminal of operational amplifier A1 is connected to the +30V single - power supply working ground through a forward capacitor C1. The output terminal of operational amplifier A1 is connected to the base of transistor T1, and the output terminal of operational amplifier A1 is also connected to the base of transistor T2. The +30V single - power supply is connected to the collector of transistor T1, and the +30V single - power supply working ground is connected to the collector of transistor T2. The voltage of the connection point of the emitters of transistor T1 and transistor T2 relative to the +30V single - power supply working ground is +15V, and this connection point serves as the ±15V symmetrical positive - negative power supply working ground.

[0017] For the non - inverting proportional operation circuit, the non - inverting input terminal of operational amplifier A2 is connected to the right - hand point Ⅱ of the load circuit RL through resistor R9. The output terminal of operational amplifier A2 is connected to the base of transistor T3, and the output terminal of operational amplifier A2 is also connected to the base of transistor T4. The connection point of the emitters of transistor T3 and transistor T4 is connected to the inverting input terminal of operational amplifier A2 through resistor R10. The inverting input terminal of operational amplifier A2 is connected to the ±15V symmetrical positive - negative power supply working ground through resistor R7. The +15V power supply is connected to pin 7 of operational amplifier A2, and the - 15V power supply is connected to pin 4 of operational amplifier A2.

[0018] For the constant - current range - switching circuit, the emitter of transistor T3 is connected to the moving contact 1 of switch S2 through resistor R11, the emitter of transistor T3 is connected to the moving contact 2 of switch S2 through resistor R12, the emitter of transistor T3 is connected to the moving contact 3 of switch S2 through resistor R13, and the emitter of transistor T3 is connected to the moving contact 4 of switch S2 through resistor R14.

[0019] The resistance value of resistor R8 in the non - inverting - terminal input - resistance circuit of operational amplifier A2 is 1.5MΩ.

[0020] For the operational - amplifier zero - adjustment circuit, a potentiometer P3 is connected between pin 1 and pin 5 of operational amplifier A2. The sliding terminal of potentiometer P3 is connected to the - 15V power supply. When adjusting the sliding terminal of potentiometer P3 to make the non - inverting input terminal of operational amplifier A2 at 0V, the output voltage of operational amplifier A2 is 0V. Description of the Drawings

[0021] Appendix Figure 1 、Appendix Figure 2 、Appendix Figure 3 Used to provide a further understanding of the present invention and form a part of this application. Appendix Figure 1 is a single - power supply converted to a positive - negative dual - power supply composed of operational amplifiers; AppendixFigure 2 is a non-inverting proportional operation circuit; attached Figure 3 is a universal constant current source adapter based on a single power supply - positive and negative symmetric power supply converter. Specific implementation manners

[0022] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0023] First, two basic circuit knowledge needed in this design idea will be briefly introduced. One is to realize the single power supply - positive and negative symmetric dual power supply conversion by using a follower based on an ideal operational amplifier; the other is to realize the constant current source design based on an ideal operational amplifier.

[0024] As mentioned above, in the design idea of this constant current source adapter, it is mentioned to use a follower circuit based on an operational amplifier to realize the single power supply - positive and negative symmetric dual power supply conversion, as Figure 1 shown. The principle is very simple. The non-inverting input terminal of the operational amplifier A is connected with a symmetric series resistor R1 / R2 voltage divider, and the operational amplifier itself is connected in the form of a voltage follower; according to the characteristics of the linear operation of the operational amplifier, it is not difficult to see that the potential between the output terminal of the operational amplifier A and the voltage dividing point is strictly equal. Since the output terminal of the operational amplifier is grounded, the power supply Vcc of the operational amplifier is accordingly divided into two groups of symmetric positive and negative power supplies ±VCC / 2.

[0025] However, the output current of a general operational amplifier circuit is generally between 0 - 25 mA. Therefore, when the output current of the operational amplifier A cannot meet the actual requirements of the subsequent circuit, it cannot be simply used in parallel like a gate circuit. At this time, the general-purpose low-power operational amplifier can be replaced with a power amplifier type operational amplifier device with a larger output current, such as the common TDA2030A. If the output current of the dual power supply is still insufficient, a larger power complementary push-pull amplifier circuit can also be connected in series in the output loop of the operational amplifier A, and a larger power positive and negative symmetric dual power supply can be output at both ends of the push-pull circuit.

[0026] Constant current source circuit based on operational amplifier

[0027] Figure 2 The circuit is a non-inverting proportional operation circuit, which is a typical voltage series negative feedback circuit.

[0028] Input voltage U I is connected to the non-inverting terminal of the operational amplifier A, and a feedback resistor R is connected between the output terminal and the inverting terminal X , and the inverting terminal is grounded through a compensation resistor R, as Figure 2 shown, so it can be considered that the input resistance is infinite and the output resistance is "0".

[0029] According to the concepts of "virtual short" and "virtual open" of the ideal operational amplifier circuit, the net input voltage of the ideal operational amplifier is "0", that is uP= u N = u I The net input current is "0", so i R = i X‘ , that is

[0030] It can be seen from the above formula that as long as the compensation resistor R and the input voltage U I are kept constant, it can ensure i X is constant. Therefore Figure 2 The in-phase proportional operation circuit of can achieve a constant current source output.

[0031] Just like Figure 1 , the output current of the operational amplifier is limited. If the load Rx requires a large current, a complementary push-pull amplifier circuit similar to Figure 1 can also be connected in series in the output loop of the operational amplifier A. Then a larger current can be obtained at the load Rx.

[0032] For another application, if it is desired that the current through the resistor R is a constant current, based on the characteristic of "virtual open" of the operational amplifier, on the basis of not fully referring to Figure 2 the in-phase proportional operation circuit, ensure that the potential at the connection point of the resistor R and Rx remains constant. Then as long as the input voltage U I is stable, the current through the resistor R is a constant current; or different values of the resistor Rx correspond to different constant currents passing through the resistor R.

[0033] Universal constant current source adapter based on single power supply - positive and negative symmetric power supply converter This universal constant current source adapter based on single power supply - positive and negative symmetric power supply converter is as Figure 3 shown. It includes a +30V single power supply, a +30V single power supply working ground, a single power supply - positive and negative symmetric ±15V power supply generation circuit based on an operational amplifier follower, a positive and negative symmetric ±15V power supply working ground, a forward constant current source control voltage generation circuit, a reverse constant current source control voltage generation circuit, an in-phase proportional operation circuit, an in-phase input resistance circuit of operational amplifier A2, an operational amplifier zero adjustment circuit, a forward constant current source power supply circuit, a reverse constant current source power supply circuit, a constant current range circuit, and a load circuit.

[0034] With the introduction of the above Figure 1 and Figure 2 basic knowledge, Figure 3 the electrical principle of the constant current source adapter circuit is not difficult to understand.

[0035] Single - supply to symmetrical ±15V power supply generation circuit based on operational amplifier follower The "single - supply to symmetrical ±15V power supply generation circuit based on operational amplifier follower" is powered by a 30V single - supply, and consists of voltage - dividing resistors R1 / R2, operational amplifier A1, and complementary push - pull circuits T1 / T2.

[0036] If the complementary push - pull circuits T1 and T2 are not considered, then the principle of the single - supply to symmetrical ±15V power supply generation circuit based on operational amplifier follower is the same as that of Figure 1 the circuit. The voltage - dividing resistors R1 and R2 divide the 30V single - supply voltage, and a 15V potential is placed at the non - inverting input terminal of the operational amplifier A1. If the emitter - base junction of transistor T1 or the emitter - base junction of transistor T2 is short - circuited, the inverting input terminal of the operational amplifier A1 will be short - circuited to the output terminal of the operational amplifier A1. The potential between the output terminal of the operational amplifier A1 and the voltage - dividing point of R1 / R2 is strictly equal, forming a voltage - follower circuit. Therefore, the 30V power supply of the operational amplifier A1 is correspondingly divided into two groups of symmetrical positive and negative power supplies ±15V.

[0037] Taking the complementary push - pull circuits T1 / T2 into account, the +15V power supply will be output from the collector of transistor T1, and the - 15V power supply will be output from the collector of transistor T2. The emitters of T1 and T2 are short - circuited, and the short - circuit point is treated as the ground point of the positive and negative dual - power supplies (note the difference from the ground point of the single - supply +30V). Therefore, the power supply +30V is divided into two groups of symmetrical ±15V power supplies (with the short - circuit point of the emitters of T1 and T2 as the working ground), and ±15V effective output voltages are provided at both ends of capacitors C2 and C3 respectively. Therefore, the function of the complementary push - pull circuits T1 / T2 is obviously power amplification.

[0038] This symmetrical ±15V power supply can not only provide symmetrical ±15V power supply for other module circuits of this design, such as the forward constant - current source control voltage generation circuit, the reverse constant - current source control voltage generation circuit, the non - inverting proportional operation circuit, etc.; moreover, if the power supply of the subsequent circuit is different from the single - supply of the previous stage and requires symmetrical positive and negative dual - power supply, then this symmetrical ±15V power supply can exactly undertake this responsibility. The working ground of the subsequent circuit is of course the short - circuit point A of the emitters of T1 and T2.

[0039] Forward and reverse constant - current source control voltage generation circuit Figure 3 In the circuit, through the load R L the constant current can be a forward constant current (as shown in the figure), or a reverse constant current. The direction of the current is controlled by the voltage at the non - inverting input terminal of the operational amplifier A2. If the voltage at the non - inverting terminal is positive, the constant current is forward (such as Figure 3 ), if the voltage at the non - inverting terminal is negative, the constant current is reverse (opposite to the direction of Figure 3 ).

[0040] The +15V power supply is successively connected to the working ground (the connection point of the emitters of transistors T1 and T2) through potentiometer P1, resistors R3 and R4. A positive constant current source control voltage is output from the sliding end of potentiometer P1, and then enters the non-inverting input terminal of operational amplifier A2 through the normally closed moving contact, static contact of switch S1, and resistor R8. The control voltage output by P1 U P1 The range is 1.5V to 15V; similarly, the -15V power supply is successively connected to the working ground (the connection point of the emitters of transistors T1 and T2) through potentiometer P2, resistors R5 and R6. A negative constant current source control voltage is output from the sliding end of potentiometer P2, and enters the non-inverting input terminal of operational amplifier A2 through the normally open moving contact, static contact of switch S1, and resistor R8. The control voltage output by P2 U P2 The range is -1.5V to -15V.

[0041] The positive constant current source control voltage and the negative constant current source control voltage are realized by the changeover switch S1. Figure 3 By default, the positive constant current source control is provided by the sliding end of potentiometer P1, and the load R L generates the current direction shown in the figure.

[0042] Non-inverting proportional operation circuit In Figure 3 , if the existence of the complementary push-pull circuit T3 / T4 is not considered, but the emitter junction of T3 is short-circuited or the emitter junction of T4 is short-circuited, then resistors R7, R8, R10 and operational amplifier A2 form a non-inverting proportional operation circuit. At this time, the output voltage of this operation circuit U O is

[0043] Here U I refers to the input voltage of this non-inverting proportional operation circuit, that is, the voltage at the non-inverting input terminal of operational amplifier A2, and also refers to the voltage U at the sliding end of potentiometer P1 P1 or the voltage U at the sliding end of potentiometer P2 P2 .

[0044] Positive constant current source power supply voltage circuit and negative constant current source power supply voltage circuit Such as Figure 2Similarly, when the load current is small, the output of the operational amplifier can directly drive the constant current source circuit. However, when the load requires a large current, the operational amplifier is unable to provide sufficient drive. Therefore, the push-pull circuit T3 / T4 still serves a power amplification function. The output of operational amplifier A2 will drive transistors T3 and T4 to conduct in sequence. If the positive constant current source control voltage is obtained from the sliding end of potentiometer P1, the constant current source control voltage is positive, and transistor T3 will conduct to generate a positive constant current source supply (powered by +15V); if the constant current source control voltage is obtained from the sliding end of potentiometer P2, the constant current source control voltage is negative, and transistor T4 will conduct to generate a negative constant current source supply (powered by -15V).

[0045] Constant Current Range Switching Circuit Whether it is a positive or negative constant current source, the value of the constant current source can be controlled not only by the positive constant current source control voltage U P1 (output voltage of the sliding end of potentiometer P1) and the negative constant current source control voltage U P2 (output voltage of the sliding end of potentiometer P2), but also by the resistors R11~R14 of the constant current range switching circuit and the switching switch S2.

[0046] That is to say, the constant current passing through the load R L depends on the voltage adjustment of P1 or P2 and the resistance range selected by the switch S2. The circuit feature is that after the actual range is determined, the current passing through the load R L is determined by the adjusted voltage of P1 or P2 U P1 or U P2 . The complementary push-pull circuit T3 and T4 only serve a buffering and power amplification function. The positive output current of this general constant current source adapter can be obtained from the following formula (1) Where R S refers to the resistor selected by the switching switch S2, which can be R11, R12, R13, or R14.

[0047] The negative output current can be obtained from the following formula (2) As known above, the output voltage of the non-inverting proportional operation circuit composed of operational amplifier A2 U O =1.1U P1 (positive) or U O =1.1U P2 (negative). Therefore, the above two formulas for calculating the load current IL The formula can be proved as follows: From Figure 3 it can be seen that the in-phase input terminal of the operational amplifier A2 draws a current of "0" (virtual open). Since the resistance value of the resistor R8 is very large (1.5 MΩ), then U P1 or U P2 The current passing through the resistor R8 due to the voltage is so small that it can be ignored. Based on "Kirchhoff's current law", at any moment in the circuit, the algebraic sum of the currents flowing out of any node is always equal to zero. Then the current passing through the resistor R9 is also equal to "0". Therefore Figure 3 The potential at point "Ⅱ" in the circuit (which is also the static contact potential of the switch S2) is U P1 or U P2 , then the voltage across both ends of any resistance range (R11~R14) is (1.1U P1 - U P1 =0.1 U P1 ) or (1.1U P2 - U P2 =0.1 U P2 ). Then the current passing through any resistance range must be equal to the current passing through the load R L . I L Thus, formulas (1) and (2) are obtained.

[0048] Manufacturing and Precautions The potentiometer P1 or P2 should have a scale of 1~10 (denoted by X, i.e., X = 1~10, as shown in Table 1) to facilitate the control of the required current. According to the adjustment of the range selection switch S2, the current can be calculated by means of the multiples listed in Table 1 below. Initially, the zero-adjustment potentiometer P3 of the operational amplifier A2 should be adjusted so that when S2 is placed in the position range "1" and P1 or P2 is adjusted to the minimum output (scale "1"), an output current of 10 μA or -10 μA can be obtained.

[0049] Table 1 Constant current source current range values S2 (Range) <![CDATA I L Current range]]> <![CDATA[P1*X]]> <![CDATA[P2*X]]> 1 (R11 = 15K) 10uA ~ 100uA 10uA - 10uA 2 (R12 = 1.5K) 100uA ~ 1mA 100uA - 100uA 3 (R13 = 150 Ω) 1mA ~ 10mA 1mA - 1mA 4 (R14 = 15Ω ) 10mA ~ 100mA 10mA - 10mA Taking the potentiometer P1 as an example, the detailed explanation is as follows: When the switch S2 range is set to "1" (resistor R11 = 15 k) and the scale of the potentiometer is "1" (U P1 = 1.5 V), I L = 0.1 U P1 / 15 K = 0.1 * 1.5 / 15 K = 10 μA; when the scale of the potentiometer is "10" (U P1 = 15 V), I L = 0.1 U P1 / 15K = 100uA, that is, the current passing through I L ranges from 10uA to 100uA. Other scales of the potentiometer P1 are similar, as shown in Table 1.

[0050] When the switch S2 range is set to "4" (resistance R11 = 15Ω) and the scale of the potentiometer is "1" (U P1 = 1.5V), I L = 0.1U P1 / 15 = 0.1 * 1.5 / 15 = 10mA; when the scale of the potentiometer is "10" (U P1 = 15V), I L = 0.1U P1 / 15 = 100mA, that is, the current passing through I L ranges from 10mA to 100mA. Other scales of the potentiometer P1 are similar, as shown in Table 1.

[0051] The calculations involving the potentiometer P2 are similar and will not be elaborated in detail, as shown in Table 1.

[0052] In addition, note that whether the front-end circuit is powered by a single power supply or a positive-negative symmetric dual power supply, this constant current source adapter can easily adapt to the front-end circuit to form a constant current source power supply. Figure 3 The circuit is a constant current source designed for single power supply. If the front-end power supply is a positive-negative symmetric dual power supply, the positive power supply of the dual power supply can be connected to the collector of the transistor TI, the negative power supply can be directly connected to the collector of the transistor T2, and the working ground of the symmetric dual power supply can be directly connected to Figure 3 point A of the circuit, that is, the "single power supply - positive-negative symmetric dual power supply converter" module circuit of Figure 3 can be ignored.

[0053] If the front-end circuit is powered by a single power supply but the back-end circuit requires a positive-negative symmetric dual power supply, this adapter can be directly used as a symmetric dual power supply without having to purchase another dual power supply.

[0054] This adapter can not only provide a constant current source module with adjustable current value and direction, but also be used as a separate symmetric power supply.

[0055] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that; still modifications or equivalent replacements can be made to the present invention, and any modification or partial replacement without departing from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. A universal constant current source adapter based on a single power supply - positive and negative symmetrical power converter, characterized in that: The constant current source adapter includes a +30V single power supply, a +30V single power supply working ground, a single power supply based on an op amp follower - positive and negative symmetrical ±15V power supply generating circuit, a positive and negative symmetrical ±15V power supply working ground, a positive constant current source control voltage generating circuit, a reverse constant current source control voltage generating circuit, a common-phase proportional operation circuit, a common-phase input resistance circuit of an op amp A2, an op amp zeroing circuit, a positive constant current source power supply circuit, a reverse constant current source power supply circuit, a constant current range switching circuit, and a load circuit; the op amp A1, the resistor R1, the resistor R2, the capacitor C1, the transistor T1, and the transistor T2 constitute the single power supply based on an op amp follower - positive and negative symmetrical ±15V power supply generating circuit, the The +30V single power supply is connected to the 7th pin of the operational amplifier A1, and the working ground of the +30V single power supply is connected to the 4th pin of the operational amplifier A1. The +15V voltage output by the operational amplifier A1 is amplified by the transistor T1 and the transistor T2, and the emitter of the transistor T1 and the emitter of the transistor T2 are connected as the positive and negative symmetrical ±15V power supply working ground; on the basis of the positive and negative symmetrical ±15V power supply working ground, the +15V power supply is output at the positive end of the capacitor C2, and the -15V power supply is output at the negative end of the capacitor C3; the +15V power supply is connected to the positive and negative symmetrical ±15V power supply working ground through the potentiometer P1, the resistor R3, and the resistor R4 in turn to form the positive constant current source control voltage generating circuit, and the sliding of the potentiometer P1 The end is connected to the normally closed moving contact of switch S1; the -15V power supply is connected to the positive and negative symmetrical ±15V power supply working place through potentiometer P2, resistor R6, and resistor R5 in sequence to form the reverse constant current source control voltage generating circuit, and the sliding end of potentiometer P2 is connected to the normally open moving contact of switch S1; operational amplifier A2, the in-phase input resistance circuit of the operational amplifier A2, resistor R8, resistor R7, resistor R10, transistor T3, and transistor T4 constitute the in-phase proportional operation circuit, the static contact of switch S1 is connected to the in-phase input end of operational amplifier A2 through resistor R8, when the output of operational amplifier A2 is a positive voltage, transistor T3 is turned on, and the +15V power supply forms the forward constant current source through the CE pole of transistor T3. Power supply circuit, when the output of operational amplifier A2 is a negative voltage, transistor T4 is turned on, and the -15V power supply constitutes the reverse constant current source power supply circuit through the CE pole of transistor T4; resistor R11, resistor R12, resistor R13, resistor R14, and switch S2 constitute the constant current range switching circuit, and the static contact of switch S2 closes different moving contacts to switch different output current ranges; the static contact of switch S2 is connected to the positive and negative symmetrical ±15V power supply working ground through the load circuit RL; when the static contact of switch S1 closes the normally closed moving contact, the load circuit RL passes through the forward constant current source, and when the static contact of switch S1 closes the normally open moving contact, the load circuit RL passes through the reverse constant current source.

2. The universal constant current source adapter based on a single power supply - positive and negative symmetrical power converter according to claim 1, characterized in that: The single power supply - positive and negative symmetrical ±15V power supply generating circuit based on the operational amplifier follower, the +30V single power supply is connected to the +30V single power supply working ground through resistors R1 and R2 in sequence, the resistance value of resistors R1 and R2 is the same, the connection point of resistors R1 and R2 is connected to the non-inverting input terminal of operational amplifier A1, and a +15V input voltage is provided for the non-inverting input terminal of operational amplifier A1, the non-inverting input terminal of operational amplifier A1 is connected to the +30V single power supply working ground through a positive capacitor C1, the output terminal of operational amplifier A1 is connected to the base of transistor T1, and the output terminal of operational amplifier A1 is simultaneously connected to the base of transistor T2, the +30V single power supply is connected to the collector of transistor T1, the +30V single power supply working ground is connected to the collector of transistor T2, the voltage of the connection point between the emitter of transistor T1 and the emitter of transistor T2 relative to the +30V single power supply working ground is +15V, and this connection point serves as the positive and negative symmetrical ±15V power supply working ground.

3. The universal constant current source adapter based on a single power supply - positive and negative symmetrical power converter according to claim 1, characterized in that: In the in-phase proportional operation circuit, the in-phase input terminal of the operational amplifier A2 is connected to the right end point II of the load circuit RL through the resistor R9, the output terminal of the operational amplifier A2 is connected to the base of the transistor T3, the output terminal of the operational amplifier A2 is also connected to the base of the transistor T4, the connection point between the emitter of the transistor T3 and the emitter of the transistor T4 is connected to the inverting input terminal of the operational amplifier A2 through the resistor R10, the inverting input terminal of the operational amplifier A2 is connected to the positive and negative symmetrical ±15V power supply working ground through the resistor R7, the +15V power supply is connected to the 7th pin of the operational amplifier A2, and the -15V power supply is connected to the 4th pin of the operational amplifier A2.

4. The universal constant current source adapter based on a single power supply - positive and negative symmetrical power converter according to claim 1, characterized in that: In the constant current range switching circuit, the emitter of transistor T3 is connected to the moving contact 1 of switch S2 through resistor R11, the emitter of transistor T3 is connected to the moving contact 2 of switch S2 through resistor R12, the emitter of transistor T3 is connected to the moving contact 3 of switch S2 through resistor R13, and the emitter of transistor T3 is connected to the moving contact 4 of switch S2 through resistor R14.

5. The universal constant current source adapter based on a single power supply - positive and negative symmetrical power converter according to claim 1, characterized in that: The resistance value of the resistor R8 of the non-inverting input resistor circuit of the operational amplifier A2 is 1.5 MΩ.

6. The universal constant current source adapter based on a single power supply - positive and negative symmetrical power converter according to claim 1, characterized in that: In the operational amplifier zero adjustment circuit, a potentiometer P3 is connected between pins 1 and 5 of the operational amplifier A2, and a sliding end of the potentiometer P3 is connected to a -15V power supply. When the sliding end of the potentiometer P3 is adjusted so that the output voltage of the operational amplifier A2 is 0V when the in-phase input end of the operational amplifier A2 is 0V,

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