Electronic load circuit and loading capacity testing method thereof

Abstract

The invention discloses an electronic load circuit and a loading capacity testing method thereof. The circuit comprises an operational amplifier, a control element, a reference voltage generation unit, at least one sampling resistor, a first switch group and a second switch. The control end of the control element is connected with the output end of the operational amplifier, and the input end serves as the circuit input end. The output end of the reference voltage generation unit is selectively connected to the input end of the operational amplifier. One end of the sampling resistor is connected with the output end of the control element. The first switch group is used for selectively connecting reference voltage to the inverted or in-phase input end of the operational amplifier. The second switch is used for selectively connecting the output end of the control element to the inverting input end of the operational amplifier. Multiple load control modes are realized by controlling switch combination and adjusting reference voltage. The device is simple in structure, low in cost and suitable for low-voltage environment testing, load parameters can be accurately controlled, and the loading capacity testing requirements of low-voltage semiconductors such as chips can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic loads, and in particular to an electronic load circuit and a method for testing its load capacity. Background Art

[0002] Electronic loads play a vital role in power supply testing, electronic component testing, and semiconductor device testing. They help verify the performance, stability, and reliability of power supply equipment and electronic components by simulating loads under actual working conditions. However, existing electronic load devices have some significant problems.

[0003] Traditional electronic load devices usually use high-precision control circuits and high-performance components, which are expensive. This poses a certain economic pressure on units with limited R&D budgets, limiting their application in the R&D and testing process.

[0004] In addition, the structure of existing electronic load devices is often complex. This complexity not only increases the cost of the equipment, but also requires a high level of technical skills for operation and maintenance. For non-professional users and small and medium-sized laboratories, the use and maintenance of these devices may face great difficulties, affecting the test efficiency and accuracy.

[0005] More importantly, many traditional electronic load devices are designed mainly for high-voltage and high-power applications, and have little support for applications in low-voltage environments. This feature makes them perform poorly when testing some low-voltage semiconductor devices or small power modules. Especially in low-voltage applications such as chip digital, analog pins and chip internal LDO (low dropout linear regulator) drive capability testing, the performance of existing electronic load devices is often limited and cannot provide accurate and stable loads, thus affecting the reliability of test results.

[0006] These problems make it difficult to test low-voltage semiconductor devices, especially when the load conditions need to be precisely controlled. The lack of electronic load devices that are suitable for low-voltage environments, reasonably priced and easy to operate has seriously restricted the development and innovation of related technologies. Summary of the invention

[0007] The object of the present invention is to provide an electronic load circuit and a method for using the same, so as to solve the problems in the prior art that the electronic load device is expensive, has a complex structure and has poor adaptability in low-voltage applications.

[0008] To achieve the above-mentioned object, the present invention provides an electronic load circuit, comprising an operational amplifier, a control element, a reference voltage generating unit, at least one sampling resistor, a first switch group and a second switch. The control end of the control element is connected to the output end of the operational amplifier, and the input end serves as the input end of the electronic load circuit. The output end of the reference voltage generating unit can be selectively connected to the input end of the operational amplifier. One end of the at least one sampling resistor is connected to the output end of the control element, and the other end is grounded. The first switch group is used to selectively connect the output end of the reference voltage generating unit to the inverting input end or the non-inverting input end of the operational amplifier. The second switch is used to selectively connect the output end of the control element to the inverting input end of the operational amplifier. By controlling the on-off combination of the first switch group and the second switch, and adjusting the output of the reference voltage generating unit, a variety of load control modes including constant current, constant voltage, constant resistance and constant power are realized.

[0009] Further, the first switch group includes a first switch of the first switch group and a second switch of the first switch group. One end of the first switch of the first switch group is connected to the output end of the reference voltage generating unit, and the other end is connected to the inverting input end of the operational amplifier. One end of the second switch of the first switch group is connected to the output end of the reference voltage generating unit, and the other end is connected to the non-inverting input end of the operational amplifier.

[0010] Specifically, the electronic load circuit further includes a third switch, one end of which is connected to the input end of the electronic load circuit, and the other end of which is connected to the non-inverting input end of the operational amplifier.

[0011] The reference voltage generating unit comprises a precision resistor and an adjustable potentiometer. One end of the precision resistor is connected to a power supply, one end of the adjustable potentiometer is connected to the other end of the precision resistor to form a reference voltage output end, and the other end is grounded.

[0012] The control element is a triode or a MOS tube, with a base or a gate as a control terminal, a collector or a drain as an input terminal, and an emitter or a source as an output terminal.

[0013] Furthermore, the electronic load circuit also includes a current limiting resistor connected in series between the output end of the operational amplifier and the control end of the control element.

[0014] The electronic load circuit further comprises a low-pass filter unit and a fourth switch. The low-pass filter unit comprises a resistor and a capacitor connected in parallel, and the fourth switch is used to selectively connect the low-pass filter unit between the input terminal and the control terminal of the control element.

[0015] Specifically, the electronic load circuit further includes a plurality of sampling resistors and a plurality of gear switches. The plurality of sampling resistors are connected in parallel between the output end of the control element and the ground. One end of each gear switch is connected in series with the corresponding sampling resistor, and the other end is connected with the second switch, for selecting one or more of the plurality of sampling resistors.

[0016] The resistance values ​​of the plurality of sampling resistors increase in increments according to a preset ratio, and the resistance ratio of adjacent sampling resistors is 10:1.

[0017] The first switch group and the second switch are one or more of a DIP switch, a jumper cap, a relay or an analog switch.

[0018] The present invention also provides a load capacity testing method using the electronic load circuit, comprising the following steps: determining the operating voltage range of the object under test; selecting a suitable sampling resistor according to the operating voltage range; setting the reference voltage by adjusting the adjustable potentiometer in the reference voltage generating unit; adjusting the on-off state of the first switch group and the second switch to set the test mode; connecting the output end of the object under test to the input end of the electronic load circuit, and connecting the ground of the object under test to the ground of the electronic load circuit; adjusting the load parameters by adjusting the output of the reference voltage generating unit, and measuring the output voltage change of the object under test at the same time.

[0019] The test mode includes at least one of a constant current mode, a constant voltage mode, a constant resistance mode and a constant power mode, and each mode is realized by a specific switch combination and a reference voltage setting. In the constant current mode, the first switch of the first switch group is disconnected, the second switch of the first switch group is closed, the third switch is disconnected, and the second switch is closed; in the constant voltage mode, the first switch of the first switch group is closed, the second switch of the first switch group is disconnected, the third switch is closed, and the second switch is disconnected; in the constant resistance mode, the first switch of the first switch group is disconnected, the second switch of the first switch group is closed, the third switch is disconnected, and the second switch is closed, and the reference voltage is dynamically adjusted according to the target resistance value and the input voltage; in the constant power mode, the first switch of the first switch group is disconnected, the second switch of the first switch group is closed, the third switch is disconnected, and the second switch is closed, and the reference voltage is dynamically adjusted according to the target power value and the real-time voltage.

[0020] The load capacity testing method is used to test the load capacity of a semiconductor device, including but not limited to testing the load capacity of a chip digital pin, an analog pin or an internal low voltage drop linear regulator.

[0021] The electronic load circuit provided by the present invention has a simple structure and low cost. Through the cooperation of an operational amplifier and a control element, accurate control of load current, voltage, impedance and power is achieved. The circuit is suitable for low-voltage environment testing, and is particularly suitable for load capacity testing of low-voltage semiconductor devices such as chips. Through the combination of multiple switches and precision sampling resistors, multi-gear adjustment is achieved to meet different test requirements.

[0022] Furthermore, the electronic load circuit of the present invention realizes multiple test modes such as constant current, constant voltage, constant resistance and constant power through a flexible combination of a reference voltage generating unit and a plurality of switches. The stability and safety of the circuit are improved by combining the design of a low-pass filter unit and a current limiting resistor. The design of multiple sampling resistors enables the circuit to have a wider test range and can adapt to devices under test of different specifications. These characteristics enable the electronic load circuit of the present invention to have higher flexibility and practicality in practical applications. At the same time, by using a variety of switch types such as a DIP switch, a jumper cap, a relay or an analog switch, the adaptability of the circuit is improved, and manual control or automatic control mode can be selected according to actual needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. 4 is a schematic diagram of the structure of an electronic load circuit in one embodiment of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the described embodiments are only used to explain the technical principles of the present invention, rather than to limit the scope of protection thereof. Those skilled in the art should understand that, without departing from the spirit and scope of the present invention, various changes, modifications or equivalent substitutions may be made to these embodiments. These changes, modifications or equivalent substitutions shall all be deemed to fall within the scope of protection defined by the claims of the present invention.

[0025] Embodiment 1 like Figure 1 As shown, the electronic load circuit provided by the present invention includes an operational amplifier U1, a transistor U2, a reference voltage generating unit, a plurality of sampling resistors R3-R7, a plurality of function switching switches S1-S4 and S10, and a plurality of gear switches S5-S9.

[0026] The operational amplifier U1 is used to control the output voltage according to the reference voltage and feedback, and its output terminal is connected to the base of the transistor U2 through the current limiting resistor R8. The current limiting resistor R8 is used to protect the transistor U2 from excessive base current. The transistor U2 is used to adjust the load voltage and current according to the output control signal of the operational amplifier, and its collector serves as the input terminal IN of the electronic load circuit, and the emitter is connected to the output terminal OUT of the electronic load circuit through a combination of multiple sampling resistors R3~R7 and gear switches S5~S9.

[0027] The reference voltage generating unit includes a precision resistor R1 and a precision adjustable potentiometer R2. The precision resistor R1 is used to cooperate with the precision adjustable potentiometer R2 to generate a reference voltage, one end of which is connected to a DC voltage source V_ADJ, and the other end is connected to the sliding end of the precision adjustable potentiometer R2 to form a reference voltage output point P1. The precision adjustable potentiometer R2 is used to fine-tune the reference voltage generated by the voltage divider resistor, and the other end of which is grounded.

[0028] The function switching switches S1 and S2 are used to selectively connect the reference voltage output point P1 to the inverting input terminal or the non-inverting input terminal of the operational amplifier U1. The function switching switch S3 is used to selectively connect the input terminal IN of the electronic load circuit to the non-inverting input terminal of the operational amplifier U1. The function switching switch S4 is used to selectively connect the emitter of the transistor U2 to the inverting input terminal of the operational amplifier U1 to receive the voltage on the feedback clamp sampling resistor.

[0029] The electronic load circuit also includes a low-pass filter unit, which is composed of a resistor R9 and a capacitor C1 connected in parallel, and is used to prevent oscillation. The function switching switch S10 is used to selectively connect the low-pass filter unit between the collector and the base of the transistor U2.

[0030] The plurality of sampling resistors R3 - R7 are used to detect load current, and cooperate with the plurality of gear switches S5 - S9 to switch the gears of the sampling resistors to achieve multi-gear regulation.

[0031] In this embodiment, the DC voltage source V_ADJ can be a 12V DC power supply, which is used to provide power for the reference voltage generating unit. The supply voltage of the operational amplifier U1 can also be 12V. The precision resistor R1 can be selected from 10KΩ, with an accuracy greater than or equal to 0.1%. The precision adjustable potentiometer R2 can be selected from 10KΩ, with an accuracy greater than or equal to 0.1%. The precision sampling resistors R3~R7 can be selected from 1Ω, 10Ω, 100Ω, 1KΩ, and 10KΩ respectively, with an accuracy greater than or equal to 0.1%, and a power greater than or equal to 250mW. The current limiting resistor R8 can be selected from 1KΩ, the low-pass filter resistor R9 can be selected from 10KΩ, and the low-pass filter capacitor C1 can be selected from 1nF.

[0032] Preferably, the operational amplifier U1 can be AD8066, and the transistor U2 can be 2N2222. Function switching switches S1~S4 and S10, and gear switches S5~S9 can be DIP switches or jumper caps. When automatic control is required, these switches can also be relays or analog switches. The specific selection belongs to the usual means of those skilled in the art and will not be repeated here.

[0033] It should be noted that the power supply voltage of the operational amplifier U1 needs to be higher than the reference voltage (P1 position voltage) and the voltage of the input terminal IN of the electronic load circuit to ensure normal operation. In addition, the number of switches and precision sampling resistors can be increased or decreased according to actual needs to increase or decrease the gears.

[0034] Embodiment 2 The working principle and use method of the electronic load circuit of the present invention are explained below with reference to specific examples. This method is suitable for testing the load capacity of semiconductor devices, including but not limited to testing the load capacity of chip digital pins, analog pins or internal low voltage drop linear regulators. The specific steps are as follows: 1. Determine the operating voltage range Vdut of the object under test. Take the chip digital pin load capacity test of 3.3V pin voltage as an example, Vdut is 3.3V.

[0035] 2. Select a suitable sampling resistor Rsense according to the operating voltage range. The selection should meet the condition of Ic × Rsense <= Vdut, where Ic is the expected load current.

[0036] 3. Set the reference voltage Vref by adjusting the precision adjustable potentiometer R2 in the reference voltage generation unit.

[0037] 4. According to the required test mode, adjust the on / off state of the first switch group (S1, S2) and the second switch (S4). The present invention supports constant current mode, constant voltage mode, constant resistance mode and constant power mode.

[0038] 5. Connect the output terminal of the object under test to the input terminal IN of the electronic load circuit, and connect the ground of the object under test to the output terminal OUT of the electronic load circuit.

[0039] 6. Adjust the load parameters by adjusting the output of the reference voltage generation unit and measure the output voltage change of the object under test at the same time.

[0040] The following describes the specific operations of each test mode: Constant current mode: 1. Open switches S1, S3, and S10 and close S2 and S4 to put the operational amplifier into amplifier mode.

[0041] 2. Determine the starting load current Ic, such as 1mA. Select a suitable sampling resistor, such as R6 (1KΩ).

[0042] 3. Adjust the precision adjustable potentiometer R2 so that the reference voltage Vref at P1 is equal to Ic × Rsense (1V in this example).

[0043] 4. The operational amplifier U1 adjusts the base voltage of the transistor U2 according to the voltage feedback at P3, so that a constant load current Ic is generated on Rsense.

[0044] 5. Gradually increase Vref, that is, increase the load current, and observe the changes in the voltage of the digital pin of the chip under test.

[0045] Constant voltage mode: 1. Close switches S1, S3, and S10 and open switches S2 and S4 to operate the op amp in comparator mode.

[0046] 2. Determine the required load voltage Vc.

[0047] 3. Select the minimum sampling resistance position to minimize the impact on the current in the path, so that the transistor can pass a larger current.

[0048] 4. Adjust the precision adjustable potentiometer R2 so that the reference voltage Vref at P1 is equal to Vc.

[0049] 5. Operational amplifier U1 controls transistor U2 to adjust the current passing through transistor U2 to maintain a constant voltage at the collector of transistor U2, thereby clamping the voltage at the input terminal IN.

[0050] 6. Observe how much current can be drawn from the object under test under the current clamping voltage.

[0051] Constant resistance mode: 1. Open switches S1, S3, and S10, and close S2 and S4.

[0052] 2. Determine the required load resistance Rc and calculate Ic = Vdut / Rc.

[0053] 3. Select a suitable sampling resistor Rsense and calculate the reference voltage Vref = Ic × Rsense.

[0054] 4. Adjust the precision adjustable potentiometer R2 to set the required reference voltage Vref.

[0055] 5. Operational amplifier U1 controls transistor U2 to maintain a constant current on Rsense, thereby simulating a constant resistance load.

[0056] Constant power mode: 1. Open switches S1, S3, and S10, and close S2 and S4.

[0057] 2. Determine the required load power Pc.

[0058] 3. According to the power calculation formula P = I × I × R, calculate the load current Ic = sqrt(Pc / Rsense).

[0059] 4. Adjust the precision adjustable potentiometer R2 to set the reference voltage Vref = Ic × Rsense.

[0060] 5. Operational amplifier U1 controls transistor U2 to maintain constant power.

[0061] In all modes, by adjusting the reference voltage and observing the output voltage change of the object under test, its performance under different load conditions can be evaluated. This method can accurately test the load capacity of various semiconductor devices, including chip digital pins, analog pins and internal low-dropout linear regulators.

[0062] Through the above method, accurate testing of the load capacity of various semiconductor devices can be achieved to meet different testing requirements.

[0063] Through the above method, the load capacity of the chip digital pin can be accurately tested. Similarly, by adjusting the switch state and reference voltage, other test modes such as constant voltage, constant resistance and constant power can be realized to meet different test requirements.

[0064] The electronic load circuit provided by the present invention has the following beneficial effects: 1. Simple structure, low cost, easy to implement and operate, especially suitable for load capacity test of low voltage semiconductor devices.

[0065] 2. Through the cooperation of operational amplifiers and transistors, precise control of load current, voltage, impedance and power is achieved to meet various testing requirements.

[0066] 3. The combined design of multiple switches and precision sampling resistors enables the circuit to have multi-level adjustment functions to adapt to devices under test of different specifications.

[0067] 4. The design of low-pass filter unit and current limiting resistor improves the stability and safety of the circuit and ensures the reliability of the test process.

[0068] 5. Supports multiple switch types, and can choose manual control or automatic control mode according to actual needs, which improves the adaptability and practicality of the circuit.

[0069] In summary, the electronic load circuit provided by the present invention not only solves the problems in the prior art that electronic load equipment is expensive, complex in structure and has poor adaptability in low-voltage applications, but also provides an economical and practical solution for testing low-voltage semiconductor devices, and has broad application prospects.

[0070] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An electronic load circuit, characterized in that: include: Operational amplifier; A control element, whose control end is connected to the output end of the operational amplifier and whose input end serves as the input end of the electronic load circuit; a reference voltage generating unit, whose output terminal can be selectively connected to the input terminal of the operational amplifier; at least one sampling resistor, one end of which is connected to the output end of the control element and the other end of which is grounded; A first switch group, used for selectively connecting the output terminal of the reference voltage generating unit to the inverting input terminal or the non-inverting input terminal of the operational amplifier; a second switch for selectively connecting the output terminal of the control element to the inverting input terminal of the operational amplifier; Among them, by controlling the on-off combination of the first switch group and the second switch and adjusting the output of the reference voltage generating unit, four load control modes including constant current, constant voltage, constant resistance and constant power are realized.

2. The electronic load circuit according to claim 1, characterized in that: The first switch group includes: A first switch of the first switch group, one end of which is connected to the output end of the reference voltage generating unit, and the other end of which is connected to the inverting input end of the operational amplifier; The second switch of the first switch group has one end connected to the output end of the reference voltage generating unit, and the other end connected to the non-inverting input end of the operational amplifier.

3. The electronic load circuit according to claim 1, characterized in that: It also includes a third switch, one end of which is connected to the input end of the electronic load circuit, and the other end of which is connected to the non-inverting input end of the operational amplifier.

4. The electronic load circuit according to claim 1, characterized in that: The reference voltage generating unit comprises: A precision resistor, one end of which is connected to the power supply; An adjustable potentiometer has one end connected to the other end of the precision resistor to form a reference voltage output end, and the other end is grounded.

5. The electronic load circuit according to claim 1, characterized in that: The control element is a triode or a MOS tube, with a base or a gate as a control terminal, a collector or a drain as an input terminal, and an emitter or a source as an output terminal.

6. The electronic load circuit according to claim 1, characterized in that: Also includes: The current limiting resistor is connected in series between the output terminal of the operational amplifier and the control terminal of the control element.

7. The electronic load circuit according to claim 1, characterized in that: Also includes: A low-pass filter unit, including a resistor and a capacitor connected in parallel; The fourth switch is used to selectively connect the low-pass filter unit between the input terminal and the control terminal of the control element.

8. The electronic load circuit according to claim 1, characterized in that: Also includes: A plurality of sampling resistors connected in parallel between the output terminal of the control element and the ground; A plurality of gear switches, one end of each gear switch is connected in series with a corresponding sampling resistor, and the other end is connected to the output end of the control element, for selecting one or more of the plurality of sampling resistors.

9. The electronic load circuit according to claim 8, characterized in that: The resistance values ​​of the plurality of sampling resistors increase in increments according to a preset ratio, and the resistance ratio of adjacent sampling resistors is 10:

1.

10. A method for testing the load capacity of an electronic load circuit according to any one of claims 1 to 9, characterized in that: The following steps are involved: Determine the operating voltage range of the object under test; Selecting a sampling resistor according to the operating voltage range; The reference voltage is set by adjusting the adjustable potentiometer in the reference voltage generating unit; Adjusting the on / off combination of the first switch group and the second switch, and adjusting the output of the reference voltage generating unit, to achieve four load control modes including constant current, constant voltage, constant resistance and constant power; Connecting the output terminal of the object under test to the input terminal of the electronic load circuit, and connecting the ground of the object under test to the ground of the electronic load circuit; The output of the reference voltage generating unit is adjusted to adjust the load parameters, and the output terminal voltage change of the measured object is measured at the same time.

11. The load capacity testing method according to claim 10, characterized in that: In the constant current mode, the first switch of the first switch group is opened, the second switch of the first switch group is closed, the third switch is opened, and the second switch is closed; In the constant voltage mode, the first switch of the first switch group is closed, the second switch of the first switch group is opened, the third switch is closed, and the second switch is opened; In the constant resistance mode, the first switch of the first switch group is opened, the second switch of the first switch group is closed, the third switch is opened, the second switch is closed, and the reference voltage is dynamically adjusted according to the target resistance value and the input voltage; In the constant power mode, the first switch of the first switch group is opened, the second switch of the first switch group is closed, the third switch is opened, the second switch is closed, and the reference voltage is dynamically adjusted according to the target power value and the real-time voltage.

12. The load capacity testing method according to claim 11, characterized in that: Used to test the load capacity of semiconductor devices, including testing the load capacity of chip digital pins, analog pins or internal low-dropout linear regulators.

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