A low current wide range adjustable pulse constant current source circuit

Abstract

A low-current wide-range adjustable pulse constant current source circuit relates to the technical field of power device static parameter Vgeth testing, and solves the problems that the existing constant current source cannot continuously select output, cannot meet the different current values ​​required by different models of power devices with different Vgeth parameters, and cannot cover all power device tests. The circuit comprises a digital signal isolation circuit, a digital potentiometer output circuit, a switch switching circuit, and a current source circuit; the digital signal isolation circuit is connected to the digital potentiometer output circuit, and the current source circuit is connected to the digital potentiometer output circuit through the switch switching circuit; the digital signal isolation circuit sends the set current signal value to the digital potentiometer output circuit, the digital potentiometer output circuit and the switch switching circuit cooperate with each other to output different resistance values, and select the current source circuit output loop, so as to control the constant current source circuit to continuously adjust the constant current output at 10uA-1A; the circuit structure is simple, the test speed is fast, and the output low current 10uA-1A is continuously adjustable with high precision.

Description

Technical Field

[0001] The invention relates to the technical field of power device static parameter Vgeth testing, in particular to a low-current wide-range adjustable pulse constant current source circuit. Background Art

[0002] Today, IGBT (insulated gate field effect transistor) has become the mainstream of high-power components and occupies a leading position in the market. Due to the progress of science and technology, the requirements of power electronic devices for lightness, thinness, compactness and high performance have driven the development of IGBT, especially in the fields of electrical equipment, optoelectronics, aerospace, railways, power conversion, etc., so that semiconductor development technicians continue to make breakthroughs in the development of high-power components under market demand.

[0003] In addition to the good functions of semiconductor components themselves, their various parameters must meet the requirements of the circuit and must be measured regularly. Otherwise, the quality characteristics of the product are difficult to guarantee, especially for larger power components, which are easy to age and reduce efficiency due to their wear and tear, burn out due to imbalance, and even explode during use. Therefore, it is more important to screen and check the parameters of new products and components in use. As for IGBT, IGBT is a mainstream semiconductor switching device widely used in modern medium and large power converters. Among them, IGBT devices are widely used in important electrical equipment such as traction inverters and auxiliary inverters of urban rail transit vehicles. The various static parameters of IGBT devices provide users with a very intuitive reference basis for reliable device selection. Therefore, accurately measuring the various static parameters of IGBT is of great practical significance.

[0004] Low current wide range adjustable pulse constant current source is a key test device specifically for measuring the Vgeth (gate-emitter threshold voltage) parameters of power device static tests; Figure 3 As shown, the main function of the constant current source is to output a specified constant current to GE after the power device CG under test is short-circuited, and measure Vge. The voltage when Vge remains constant is Vgeth.

[0005] like Figure 4 As shown, in the current national standard test circuit, the static test Vgeth parameter measurement of power devices is to apply the rated voltage between C and E, and adjust the voltage step by step through the voltage source. When the value of the current detection Ice reaches the preset current value, the value of the voltage detection Vge at this time is recorded, that is, Vgeth. This circuit has many components and the test method is complicated. In addition, in the Vgeth test circuit currently on the market, the output current of the constant current source applied only meets the requirements of multiple fixed values ​​for selectable output, but cannot meet the requirements of continuously selectable output, and cannot meet the requirements of different current values ​​required by different models of power devices with different Vgeth parameters, and cannot cover the test of all power devices.

[0006] In the prior art, "Design of a New Continuously Adjustable Pulse Current Source" (Zhou Haibing et al., Institute of Semiconductors, Chinese Academy of Sciences) discloses a new type of digitally controlled adjustable pulse current source, the core of which is a precision constant current source circuit and a pulse current mirror circuit. The precision constant current source circuit adopts deep negative feedback technology based on operational amplifiers to provide a constant current output with high precision, good stability and continuously adjustable amplitude; the pulse current mirror circuit adopts high-speed field effect transistors to achieve the replication and multiplication of the constant current source current, reduce the influence of the pulse current source output load on the deep negative feedback part of the previous stage, improve the stability of the circuit, and use the analog multiplexer to control the current mirror gate to pass the pulse signal to the pulse current, thereby outputting the pulse current.

[0007] However, the technical solution of the above document does not solve the problem that the applied constant current source cannot meet the requirement of continuously selectable output, cannot meet the requirements of different current values ​​required by different models of power devices with different Vgeth parameters, and cannot cover the test of all power devices. Summary of the invention

[0008] The technical problem to be solved by the present invention is that the existing constant current source cannot continuously select output, cannot meet the different current values ​​required by different models of power devices with different Vgeth parameters, and cannot cover the test of all power devices.

[0009] The present invention solves the above technical problems through the following technical solutions:

[0010] A low-current wide-range adjustable pulse constant current source circuit comprises a digital signal isolation circuit, a digital potentiometer output circuit, a switch switching circuit, and a current source circuit; the digital signal isolation circuit is connected to the digital potentiometer output circuit, and the current source circuit is connected to the digital potentiometer output circuit through the switch switching circuit; the digital signal isolation circuit sends a set current signal value to the digital potentiometer output circuit, the digital potentiometer output circuit and the switch switching circuit cooperate with each other to output different resistance values, and select the output loop of the current source circuit, thereby controlling the constant current source circuit to continuously output an adjustable constant current of 10uA-1A.

[0011] The constant current source circuit of the present invention ensures fast, high-precision and continuously adjustable constant current source output by controlling the output adjustable resistance of a high-precision digital potentiometer and selecting high-precision current sources in different ranges; the constant current source is output to the power device of the object to be tested to directly obtain a stable static parameter Vgeth value of the power device; in the national standard test circuit, the power device static test Vgeth parameter measurement requires a continuously adjustable voltage source, and the current value is detected in real time to reach a preset current value. At this time, the applied voltage value is Vgeth. This method requires synchronous detection of voltage and current values, has high requirements on sampling rate, is relatively costly to implement, and is complex to control.

[0012] As a further improvement of the technical solution of the present invention, the digital signal isolation circuit includes a four-channel digital signal isolator (U1) and a dual-channel digital signal isolator (U2); the digital potentiometer output circuit includes a 100K digital potentiometer (U3), a 10K digital potentiometer (U4) and a 1K digital potentiometer (U5); the 100K digital potentiometer (U3) is connected to the four-channel digital signal isolator (U1); the 10K digital potentiometer (U4) is respectively connected to the four-channel digital signal isolator (U1) and the dual-channel digital signal isolator (U2); the 1K digital potentiometer (U5) is respectively connected to the four-channel digital signal isolator (U1) and the dual-channel digital signal isolator (U2).

[0013] As a further improvement of the technical solution of the present invention, the digital potentiometer output circuit also includes a capacitor C1 and a capacitor C3, one end of the capacitor C1 is connected to the 7# pin of the 100K digital potentiometer (U3), and the other end is grounded; one end of the capacitor C3 is connected to the 7# pin of the 10K digital potentiometer (U4), and the other end is grounded.

[0014] As a further improvement of the technical solution of the present invention, the switch switching circuit includes a first switch (SW1), a second switch (SW2), a fifth switch (SW5), a sixth switch (SW6), an eighth switch (SW8), and a ninth switch (SW9); the 1# terminal of the first switch (SW1) is connected to the 4# pin of the 100K digital potentiometer (U3), the 1# terminal of the second switch (SW2) is connected to the 5# pin of the 100K digital potentiometer (U3), the 1# terminal of the fifth switch (SW5) is connected to the 2# pin of the 10K digital potentiometer (U4), and the 6# terminal of the first switch (SW1) is connected to the 4# pin of the 100K digital potentiometer (U3). The 1# terminal of the eighth switch (SW8) is connected to the 3# pin of the 10K digital potentiometer (U4), the 1# terminal of the eighth switch (SW8) is connected to the 7# pin of the 1K digital potentiometer (U5), and the 1# terminal of the ninth switch (SW9) is connected to the 1# pin of the 1K digital potentiometer (U5); the 2# terminal of the first switch (SW1), the 2# terminal of the fifth switch (SW5), and the 2# terminal of the eighth switch (SW8) are connected together, and the 2# terminal of the second switch (SW2), the 2# terminal of the sixth switch (SW6), and the 2# terminal of the ninth switch (SW9) are connected together.

[0015] As a further improvement of the technical solution of the present invention, the switch switching circuit further includes a first selection switch (SW4) and a second selection switch (SW7); the current source circuit includes a current source chip (U6), an adjustable low-dropout voltage regulator (U7), and a resistor R1; the 2# terminal of the first selection switch (SW4) is connected to the 2# terminal of the first switch (SW1), the 2# terminal of the fifth switch (SW5), and the 2# terminal of the eighth switch (SW8); the 1# terminal of the first selection switch (SW4) is connected to the 1# pin of the current source chip (U6); One end of the resistor R1 is connected to the 2# pin of the adjustable low-dropout voltage regulator (U7), and the other end of the resistor R1 is connected to the 3# terminal of the first selection switch (SW4); the 2# terminal of the second selection switch (SW7) is connected to the 2# terminal of the second switch (SW2), the 2# terminal of the sixth switch (SW6), and the 2# terminal of the ninth switch (SW9); the 1# terminal of the second selection switch (SW7) is connected to the 2# pin of the current source chip (U6), and the 3# terminal of the second selection switch (SW7) is connected to the 1# pin of the adjustable low-dropout voltage regulator (U7).

[0016] As a further improvement of the technical solution of the present invention, the current source circuit also includes an analog selection switch (SW3), a MOSFET power device (Q1), a resistor R2, a power device control signal generator; a capacitor C2, a capacitor C4; the 2# terminal of the analog selection switch (SW3) is connected to the 1# pin of the current source chip (U6), the 1# terminal of the analog selection switch (SW3) is connected to the drain of the MOSFET power device (Q1), the 3# terminal of the analog selection switch (SW3) is grounded, and the source of the MOSFET power device (Q1) is connected to the 1# pin of the current source chip (U6). grounded; one end of the capacitor C2 is connected to the 3# pin of the current source chip (U6), and the other end is grounded; one end of the capacitor C4 is connected to the 3# pin of the adjustable low-dropout voltage regulator (U7), and the other end is grounded; one end of the resistor R1 is connected to the 2# pin of the adjustable low-dropout voltage regulator (U7), and the other end of the resistor R1 is connected to the drain of the MOSFET power device (Q1); the resistor R2 is connected in parallel between the gate and source of the MOSFET power device (Q1), and the power device control signal generator is connected in parallel to both ends of the resistor R2.

[0017] As a further improvement of the technical solution of the present invention, the constant current source circuit has a continuous adjustable constant current output of 10uA-1A, which is implemented in a 5-stage combination:

[0018] 1) 10uA-0.06mA continuous adjustable current output

[0019] The four-channel digital signal isolator (U1) selects the 100K digital potentiometer (U3), and sets the D value of the 100K digital potentiometer (U3) through formulas (1) and (2), so that the 100K digital potentiometer (U3) outputs a resistance value corresponding to the required current. The current source chip (U6) is selected to output the corresponding current value through the first switch (SW1), the second switch (SW2), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows:

[0020] Iout=67.7 / RSET(D) (1)

[0021] RSET(D)=D*100K / 1024 (2)

[0022] Wherein, Iout is the output current value, RSET(D) is the set resistance value, 67.7 is the rated output value of the current source chip (U6), and D is a decimal value. In this case, the value range is 1-69;

[0023] 2) 0.06mA-1mA continuous adjustable current output

[0024] The four-channel digital signal isolator (U1) and the two-channel digital signal isolator (U2) select the 1K digital potentiometer (U5) and set the D value of the 1K digital potentiometer (U5) through formulas (1) and (3), so that the 1K digital potentiometer (U5) outputs a resistance value corresponding to the required current, and the current source chip (U6) is selected to output the corresponding current value through the eighth switch (SW8), the ninth switch (SW9), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows:

[0025] Iout=67.7 / RSET(D) (1)

[0026] RSET(D)=D*1K / 256 (3)

[0027] Among them, the value range of D at this time is 17-256;

[0028] 3) 1mA-10mA continuous adjustable current output

[0029] The four-channel digital signal isolator (U1) and the two-channel digital signal isolator (U2) select the 1K digital potentiometer (U5) and set the D value of the 1K digital potentiometer (U5) through formulas (3) and (4), so that the 1K digital potentiometer (U5) outputs a resistance value corresponding to the required current, and the adjustable low-dropout voltage regulator (U7) is selected to output the corresponding current value through the eighth switch (SW8), the ninth switch (SW9), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows:

[0030] RSET(D)=D*1K / 256 (3)

[0031] Iout=RSET(D)*10 (4)

[0032] Among them, 10 is the rated output value of the adjustable low-dropout regulator (U7), and the value range of D is 26-256;

[0033] 4) 10mA-100mA continuous adjustable current output

[0034] The four-channel digital signal isolator (U1) and the two-channel digital signal isolator (U2) select the 10K digital potentiometer (U4) and set the D value of the 10K digital potentiometer (U4) through formulas (4) and (5), so that the 10K digital potentiometer (U4) outputs a resistance value corresponding to the required current, and the adjustable low-dropout voltage regulator (U7) is selected to output the corresponding current value through the fifth switch (SW5), the sixth switch (SW6), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows:

[0035] Iout=RSET(D)*10 (4)

[0036] RSET(D)=D*10K / 1024 (5)

[0037] Among them, the value range of D at this time is 102-1024;

[0038] 5) 100mA-1A continuous adjustable current output

[0039] The four-channel digital signal isolator (U1) selects the 100K digital potentiometer (U3) and sets the D value of the 100K digital potentiometer (U3) through formulas (2) and (4), so that the 100K digital potentiometer (U3) outputs a resistance value corresponding to the required current. The adjustable low-dropout regulator (U7) is selected to output the corresponding current value through the first switch (SW1), the second switch (SW2), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows:

[0040] RSET(D)=D*100K / 1024 (2)

[0041] Iout=RSET(D)*10 (4)

[0042] The value range of D is 103-1024.

[0043] As a further improvement of the technical solution of the present invention, the model of the four-channel digital signal isolator (U1) is ADUM141E, and the model of the dual-channel digital signal isolator (U2) is ADUM1200.

[0044] As a further improvement of the technical solution of the present invention, the model of the 100K digital potentiometer (U3) is AD5293, the model of the 10K digital potentiometer (U4) is AD5174, and the model of the 1K digital potentiometer (U5) is AD8400.

[0045] As a further improvement of the technical solution of the present invention, the model of the current source chip (U6) is LM334; the model of the adjustable low-dropout voltage regulator (U7) is LT3080; the model of the analog selection switch (SW3) is ADG5419; and the model of the MOSFET power device (Q1) is FQP50N06.

[0046] The advantages of the present invention are:

[0047] (1) The constant current source circuit of the present invention ensures fast, high-precision and continuously adjustable constant current source output by controlling the output adjustable resistance of the high-precision digital potentiometer and selecting high-precision current sources in different ranges; the constant current source is output to the power device under test to directly obtain a stable static parameter Vgeth value of the power device; in the national standard test circuit, the static test Vgeth parameter measurement of the power device requires a continuously adjustable voltage source, and the current value is detected in real time to reach the preset current value. At this time, the applied voltage value is Vgeth. This method requires synchronous detection of voltage and current values, has high requirements on sampling rate, is relatively costly to implement, and is complex to control.

[0048] (2) The constant current source outputs a low current of 10uA-1A, which is continuously adjustable and has high output precision. The output of the constant current source is mostly single and non-adjustable or divided into multiple levels of adjustment. By programming and controlling the output of three high-precision digital potentiometers of 1K, 10K, and 100K to achieve continuously adjustable resistance values, combined with different combinations of power supply chips with high and low current ranges, a wide range of low current continuously adjustable and high-precision constant current source output is output. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A digital signal isolation circuit diagram of a low current wide range adjustable pulse constant current source circuit according to an embodiment of the present invention;

[0050] Figure 2 This is a main circuit diagram of a low current wide range adjustable pulse constant current source circuit according to an embodiment of the present invention;

[0051] Figure 3 This is the circuit schematic diagram of the national standard Vgeth parameter test method;

[0052] Figure 4 This is the circuit schematic diagram for applying the Vgeth parameter test method of a wide-range adjustable constant current source. DETAILED DESCRIPTION

[0053] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0055] Embodiment 1

[0056] like Figure 1 and Figure 2 As shown, a low-current wide-range adjustable pulse constant current source circuit includes a digital signal isolation circuit, a digital potentiometer output circuit, a switch switching circuit, and a current source circuit; the digital signal isolation circuit is connected to the digital potentiometer output circuit, and the current source circuit is connected to the digital potentiometer output circuit through the switch switching circuit; the IGBT power device DUT1 under test is connected to the current source circuit through the analog selection switch SW3 or the MOSFET power device Q1.

[0057] like Figure 1 As shown, the digital signal isolation circuit includes a four-channel digital signal isolator U1 and a dual-channel digital signal isolator U2; the model of the four-channel digital signal isolator U1 is ADUM141E, and the model of the dual-channel digital signal isolator U2 is ADUM1200; the signal input ends of the four-channel digital signal isolator U1 and the dual-channel digital signal isolator U2 are respectively connected to the DSP controller through SPI communication, and the signal output ends of the four-channel digital signal isolator U1 and the dual-channel digital signal isolator U2 are respectively connected to the 100K digital potentiometer U3, the 10K digital potentiometer U4 and the 1K digital potentiometer U5.

[0058] like Figure 2 As shown, the digital potentiometer output circuit includes a 100K digital potentiometer U3 and an external capacitor C1, a 10K digital potentiometer U4 and an external capacitor C3, and a 1K digital potentiometer U5; the 100K digital potentiometer U3 is model AD5293, the 10K digital potentiometer U4 is model AD5174, and the 1K digital potentiometer U5 is model AD8400.

[0059] The switch switching circuit includes a first switch SW1, a second switch SW2, a fifth switch SW5, a sixth switch SW6, an eighth switch SW8, a ninth switch SW9, a first selection switch SW4, and a second selection switch SW7, and switches are combined to match different resistance values ​​and select current source circuits.

[0060] The current source circuit includes a current source chip U6, an adjustable low-dropout voltage regulator U7, a capacitor C2, a capacitor C4, an analog selection switch SW3, a MOSFET power device Q1, a resistor R1, a resistor R2, and a power device control signal generator; the current source chip U6 is LM334; the adjustable low-dropout voltage regulator U7 is LT3080; the analog selection switch SW3 that controls the on-off of the output current of the current source chip U6 is ADG5419; the MOSFET power device Q1 that controls the on-off of the output current of the adjustable low-dropout voltage regulator U7 is FQP50N06.

[0061] The 100K digital potentiometer U3 is connected to the four-channel digital signal isolator U1; the 10K digital potentiometer U4 is respectively connected to the four-channel digital signal isolator U1 and the dual-channel digital signal isolator U2; the 1K digital potentiometer U5 is respectively connected to the four-channel digital signal isolator U1 and the dual-channel digital signal isolator U2; one end of the capacitor C1 is connected to the 7# pin of the 100K digital potentiometer U3, and the other end is grounded; one end of the capacitor C3 is connected to the 7# pin of the 10K digital potentiometer U4, and the other end is grounded.

[0062] The 1# terminal of the first switch SW1 is connected to the 4# pin of the 100K digital potentiometer U3, the 1# terminal of the second switch SW2 is connected to the 5# pin of the 100K digital potentiometer U3, the 1# terminal of the fifth switch SW5 is connected to the 2# pin of the 10K digital potentiometer U4, the 1# terminal of the sixth switch SW6 is connected to the 3# pin of the 10K digital potentiometer U4, the 1# terminal of the eighth switch SW8 is connected to the 7# pin of the 1K digital potentiometer U5, and the 1# terminal of the ninth switch SW9 is connected to the 1# pin of the 1K digital potentiometer U5; the 2# terminal of the first switch SW1, the 2# terminal of the fifth switch SW5, and the 2# terminal of the eighth switch SW8 are connected together, and the 2# terminal of the second switch SW2, the 2# terminal of the sixth switch SW6, and the 2# terminal of the ninth switch SW9 are connected together.

[0063] The 2# terminal of the first selection switch SW4 is connected to the 2# terminal of the first switch SW1, the 2# terminal of the fifth switch SW5, and the 2# terminal of the eighth switch SW8, the 1# terminal of the first selection switch SW4 is connected to the 1# pin of the current source chip U6, and the 3# terminal of the first selection switch SW4 is connected to the drain of the MOSFET power device Q1.

[0064] The 2# terminal of the second selection switch SW7 is connected to the 2# terminal of the second switch SW2, the 2# terminal of the sixth switch SW6, and the 2# terminal of the ninth switch SW9, the 1# terminal of the second selection switch SW7 is connected to the 2# pin of the current source chip U6, and the 3# terminal of the second selection switch SW7 is connected to the 1# pin of the adjustable low dropout regulator U7.

[0065] One end of the capacitor C2 is connected to the 3# pin of the current source chip U6, and the other end is grounded; one end of the capacitor C4 is connected to the 3# pin of the adjustable low-dropout voltage regulator U7, and the other end is grounded; one end of the resistor R1 is connected to the 2# pin of the adjustable low-dropout voltage regulator U7, and the other end of the resistor R1 is connected to the drain of the MOSFET power device Q1; the resistor R2 is connected in parallel between the gate and source of the MOSFET power device Q1, the power device control signal generator is connected in parallel at both ends of the resistor R2, and the source of the MOSFET power device Q1 is grounded; the 2# terminal of the analog selection switch SW3 is connected to the 1# pin of the current source chip U6, the 1# terminal of the analog selection switch SW3 is connected to the drain of the MOSFET power device Q1, and the 3# terminal of the analog selection switch SW3 is grounded.

[0066] The host computer sends the set current signal value to the DSP controller, and the DSP controller sends the current signal value to the digital signal isolation circuit through SPI communication. The digital signal isolation circuit sends the current signal value to the digital potentiometer output circuit. The digital potentiometer output circuit outputs the resistance value corresponding to the current signal value by selecting 100K digital potentiometer U3, 10K digital potentiometer U4 or 1K digital potentiometer U5, and selects the current source chip U6 or the adjustable low voltage drop regulator U7 through the switch switching circuit to achieve 10uA-1A continuous adjustable constant current output.

[0067] In the embodiment of the present invention, a 10uA-1A continuously adjustable constant current source output is achieved in a 5-stage combination mode, which are:

[0068] (1) 10uA-0.06mA continuous adjustable current output

[0069] DSP selects 100K digital potentiometer U3 through four-channel digital signal isolator U1, and sets the D value of 100K digital potentiometer U3 through formulas (1) and (2), so that 100K digital potentiometer U3 outputs the resistance value corresponding to the required current, and selects current source chip U6 to output the corresponding current value through the first switch SW1, the second switch SW2, the first selection switch SW4, and the second selection switch SW7. The calculation formula is as follows:

[0070] Iout=67.7 / RSET(D) (1)

[0071] RSET(D)=D*100K / 1024 (2)

[0072] Among them, Iout is the output current value, RSET(D) is the set resistance value, 67.7 is the rated output value of the current source chip U6, and D is a decimal value. At this time, the value range is 1-69.

[0073] (2) 0.06mA-1mA continuously adjustable current output

[0074] DSP selects 1K digital potentiometer U5 through four-channel digital signal isolator U1 and two-channel digital signal isolator U2 and sets the D value of 1K digital potentiometer U5 through formulas (1) and (3), so that 1K digital potentiometer U5 outputs the resistance value corresponding to the required current, and selects current source chip U6 to output the corresponding current value through the eighth switch SW8, the ninth switch SW9, the first selection switch SW4 and the second selection switch SW7. The calculation formula is as follows:

[0075] Iout=67.7 / RSET(D) (1)

[0076] RSET(D)=D*1K / 256 (3)

[0077] Here, the value range of D is 17-256.

[0078] (3) 1mA-10mA continuously adjustable current output

[0079] DSP selects 1K digital potentiometer U5 through four-channel digital signal isolator U1 and two-channel digital signal isolator U2 and sets the D value of 1K digital potentiometer U5 through formulas (3) and (4), so that 1K digital potentiometer U5 outputs the resistance value corresponding to the required current, and selects the adjustable low-dropout voltage regulator U7 to output the corresponding current value through the eighth switch SW8, the ninth switch SW9, the first selection switch SW4, and the second selection switch SW7. The calculation formula is as follows:

[0080] RSET(D)=D*1K / 256 (3)

[0081] Iout=RSET(D)*10 (4)

[0082] Among them, 10 is the rated output value of the adjustable low-dropout regulator U7, and the value range of D is 26-256.

[0083] (4) 10mA-100mA continuous adjustable current output

[0084] DSP selects 10K digital potentiometer U4 through four-channel digital signal isolator U1 and two-channel digital signal isolator U2 and sets the D value of 10K digital potentiometer U4 through formulas (4) and (5), so that 10K digital potentiometer U4 outputs the resistance value corresponding to the required current, and selects adjustable low-dropout voltage regulator U7 to output the corresponding current value through the fifth switch SW5, the sixth switch SW6, the first selection switch SW4, and the second selection switch SW7. The calculation formula is as follows:

[0085] Iout=RSET(D)*10 (4)

[0086] RSET(D)=D*10K / 1024 (5)

[0087] Here, the value range of D is 102-1024.

[0088] (5) 100mA-1A continuous adjustable current output

[0089] DSP selects 100K digital potentiometer U3 through four-channel digital signal isolator U1 and sets the D value of 100K digital potentiometer U3 through formulas (2) and (4), so that 100K digital potentiometer U3 outputs the resistance value corresponding to the required current, and selects the adjustable low-dropout voltage regulator U7 to output the corresponding current value through the first switch SW1, the second switch SW2, the first selection switch SW4, and the second selection switch SW7. The calculation formula is as follows:

[0090] RSET(D)=D*100K / 1024 (2)

[0091] Iout=RSET(D)*10 (4)

[0092] The value range of D is 103-1024.

[0093] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low current wide range adjustable pulse constant current source circuit, characterized in that: It includes a digital signal isolation circuit, a digital potentiometer output circuit, a switch switching circuit, and a current source circuit; the digital signal isolation circuit is connected to the digital potentiometer output circuit, and the current source circuit is connected to the digital potentiometer output circuit through the switch switching circuit; the digital signal isolation circuit sends the set current signal value to the digital potentiometer output circuit, the digital potentiometer output circuit and the switch switching circuit cooperate with each other to output different resistance values, and select the output loop of the current source circuit, so as to control the constant current source circuit to continuously adjust the constant current output at 10uA-1A; The digital signal isolation circuit comprises a four-channel digital signal isolator (U1) and a two-channel digital signal isolator (U2); the digital potentiometer output circuit comprises a 100K digital potentiometer (U3), a 10K digital potentiometer (U4) and a 1K digital potentiometer (U5); the 100K digital potentiometer (U3) is connected to the four-channel digital signal isolator (U1); the 10K digital potentiometer (U4) is respectively connected to the four-channel digital signal isolator (U1) and the two-channel digital signal isolator (U2); the 1K digital potentiometer (U5) is respectively connected to the four-channel digital signal isolator (U1) and the two-channel digital signal isolator (U2); The switch switching circuit includes a first switch (SW1), a second switch (SW2), a fifth switch (SW5), a sixth switch (SW6), an eighth switch (SW8), a ninth switch (SW9), a first selection switch (SW4), and a second selection switch (SW7); the 1# terminal of the first switch (SW1) is connected to the 4# pin of the 100K digital potentiometer (U3), the 1# terminal of the second switch (SW2) is connected to the 5# pin of the 100K digital potentiometer (U3), the 1# terminal of the fifth switch (SW5) is connected to the 2# pin of the 10K digital potentiometer (U4), and the The 1# terminal of the sixth switch (SW6) is connected to the 3# pin of the 10K digital potentiometer (U4), the 1# terminal of the eighth switch (SW8) is connected to the 7# pin of the 1K digital potentiometer (U5), and the 1# terminal of the ninth switch (SW9) is connected to the 1# pin of the 1K digital potentiometer (U5); the 2# terminal of the first switch (SW1), the 2# terminal of the fifth switch (SW5), and the 2# terminal of the eighth switch (SW8) are connected together, and the 2# terminal of the second switch (SW2), the 2# terminal of the sixth switch (SW6), and the 2# terminal of the ninth switch (SW9) are connected together; The current source circuit comprises a current source chip (U6), an adjustable low-dropout voltage regulator (U7), and a resistor R1; the 2# terminal of the first selection switch (SW4) is connected to the 2# terminal of the first switch (SW1), the 2# terminal of the fifth switch (SW5), and the 2# terminal of the eighth switch (SW8); the 1# terminal of the first selection switch (SW4) is connected to the 1# pin of the current source chip (U6); one end of the resistor R1 is connected to the 2# pin of the adjustable low-dropout voltage regulator (U7); The other end of the resistor R1 is connected to the 3# terminal of the first selection switch (SW4); the 2# terminal of the second selection switch (SW7) is connected to the 2# terminal of the second switch (SW2), the 2# terminal of the sixth switch (SW6), and the 2# terminal of the ninth switch (SW9); the 1# terminal of the second selection switch (SW7) is connected to the 2# pin of the current source chip (U6); and the 3# terminal of the second selection switch (SW7) is connected to the 1# pin of the adjustable low-dropout regulator (U7).

2. A low current wide range adjustable pulse constant current source circuit according to claim 1, characterized in that: The digital potentiometer output circuit also includes a capacitor C1 and a capacitor C3. One end of the capacitor C1 is connected to the 7# pin of the 100K digital potentiometer (U3) and the other end is grounded. One end of the capacitor C3 is connected to the 7# pin of the 10K digital potentiometer (U4) and the other end is grounded.

3. A low current wide range adjustable pulse constant current source circuit according to claim 1, characterized in that: The current source circuit also includes an analog selection switch (SW3), a MOSFET power device (Q1), a resistor R2, a power device control signal generator; a capacitor C2 and a capacitor C4; the 2# terminal of the analog selection switch (SW3) is connected to the 1# pin of the current source chip (U6), the 1# terminal of the analog selection switch (SW3) is connected to the drain of the MOSFET power device (Q1), the 3# terminal of the analog selection switch (SW3) is grounded, and the source of the MOSFET power device (Q1) is grounded; the capacitor One end of C2 is connected to the 3# pin of the current source chip (U6), and the other end is grounded; one end of the capacitor C4 is connected to the 3# pin of the adjustable low-dropout voltage regulator (U7), and the other end is grounded; one end of the resistor R1 is connected to the 2# pin of the adjustable low-dropout voltage regulator (U7), and the other end of the resistor R1 is connected to the drain of the MOSFET power device (Q1); the resistor R2 is connected in parallel between the gate and source of the MOSFET power device (Q1), and the power device control signal generator is connected in parallel to both ends of the resistor R2.

4. A low current wide range adjustable pulse constant current source circuit according to claim 1, characterized in that: The constant current source circuit has a continuous adjustable constant current output of 10uA-1A, which is realized in 5 sections: 1) 10uA-0.06mA continuous adjustable current output The four-channel digital signal isolator (U1) selects the 100K digital potentiometer (U3), and sets the D value of the 100K digital potentiometer (U3) through formulas (1) and (2), so that the 100K digital potentiometer (U3) outputs a resistance value corresponding to the required current. The current source chip (U6) is selected to output the corresponding current value through the first switch (SW1), the second switch (SW2), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows: Iout=67.7 / RSET(D) (1) RSET(D)=D*100K / 1024 (2) Wherein, Iout is the output current value, RSET(D) is the set resistance value, 67.7 is the rated output value of the current source chip (U6), and D is a decimal value. In this case, the value range is 1-69; 2) 0.06mA-1mA continuous adjustable current output The four-channel digital signal isolator (U1) and the two-channel digital signal isolator (U2) select the 1K digital potentiometer (U5) and set the D value of the 1K digital potentiometer (U5) through formulas (1) and (3), so that the 1K digital potentiometer (U5) outputs a resistance value corresponding to the required current, and the current source chip (U6) is selected to output the corresponding current value through the eighth switch (SW8), the ninth switch (SW9), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows: Iout=67.7 / RSET(D) (1) RSET(D)=D*1K / 256 (3) Among them, the value range of D at this time is 17-256; 3) 1mA-10mA continuous adjustable current output The four-channel digital signal isolator (U1) and the two-channel digital signal isolator (U2) select the 1K digital potentiometer (U5) and set the D value of the 1K digital potentiometer (U5) through formulas (3) and (4), so that the 1K digital potentiometer (U5) outputs a resistance value corresponding to the required current, and the adjustable low-dropout voltage regulator (U7) is selected to output the corresponding current value through the eighth switch (SW8), the ninth switch (SW9), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows: RSET(D)=D*1K / 256 (3) Iout=RSET(D)*10 (4) Among them, 10 is the rated output value of the adjustable low-dropout regulator (U7), and the value range of D is 26-256; 4) 10mA-100mA continuous adjustable current output The four-channel digital signal isolator (U1) and the two-channel digital signal isolator (U2) select the 10K digital potentiometer (U4) and set the D value of the 10K digital potentiometer (U4) through formulas (4) and (5), so that the 10K digital potentiometer (U4) outputs a resistance value corresponding to the required current, and the adjustable low-dropout voltage regulator (U7) is selected to output the corresponding current value through the fifth switch (SW5), the sixth switch (SW6), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows: Iout=RSET(D)*10 (4) RSET(D)=D*10K / 1024 (5) Among them, the value range of D at this time is 102-1024; 5) 100mA-1A continuous adjustable current output The four-channel digital signal isolator (U1) selects the 100K digital potentiometer (U3) and sets the D value of the 100K digital potentiometer (U3) through formulas (2) and (4), so that the 100K digital potentiometer (U3) outputs a resistance value corresponding to the required current. The adjustable low-dropout regulator (U7) is selected to output the corresponding current value through the first switch (SW1), the second switch (SW2), the first selection switch (SW4), and the second selection switch (SW7). The calculation formula is as follows: RSET(D)=D*100K / 1024 (2) Iout=RSET(D)*10 (4) The value range of D is 103-1024.

5. A low current wide range adjustable pulse constant current source circuit according to claim 1, characterized in that: The model of the four-channel digital signal isolator (U1) is ADUM141E, and the model of the dual-channel digital signal isolator (U2) is ADUM1200.

6. A low current wide range adjustable pulse constant current source circuit according to claim 1, characterized in that: The model of the 100K digital potentiometer (U3) is AD5293, the model of the 10K digital potentiometer (U4) is AD5174, and the model of the 1K digital potentiometer (U5) is AD8400.

7. A low current wide range adjustable pulse constant current source circuit according to claim 3, characterized in that: The model of the current source chip (U6) is LM334; the model of the adjustable low-dropout voltage regulator (U7) is LT3080; the model of the analog selection switch (SW3) is ADG5419; and the model of the MOSFET power device (Q1) is FQP50N06.

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