High-voltage linear direct-current excitation power supply and resistance measurement system

Abstract

The utility model provides a high-voltage linear direct-current excitation power supply and a resistance measurement system, and relates to the technical field of power electronics. The high-voltage linear direct-current excitation power supply comprises a transformer, a first switching device and a rectifier, the transformer comprises a primary winding and three secondary windings, and the first switching device comprises three optocoupler relays; the primary winding is used for being connected with an alternating current power supply, the secondary winding is connected with a third pin of the optocoupler relay, a fourth pin of the optocoupler relay is connected with the input end of the rectifier, and when the first pin of the optocoupler relay receives a high level, a circuit between the third pin and the fourth pin is conducted; wherein the first pin is connected with the corresponding second pin through the light emitting diode, and the third pin is connected with the corresponding fourth pin through the field effect transistor and the photosensitive diode. The high-voltage linear direct-current excitation power supply can meet various power requirements of equipment, and the applicability of the high-voltage linear direct-current excitation power supply is improved.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and more specifically, to a high-voltage linear DC excitation power supply and a resistance measurement system. Background Technology

[0002] High-voltage linear DC excitation power supplies are key components in modern electronic and industrial equipment, widely used in various fields such as medical equipment, communication equipment, scientific research instruments, and industrial automation control systems. The main function of a high-voltage linear DC excitation power supply is to convert the standard mains voltage into the high-voltage DC voltage required by the equipment, thereby providing stable power support for its normal operation.

[0003] In related technologies, high-voltage linear DC excitation power supplies provide a single high-voltage DC voltage. This not only fails to meet the diverse power demands of the same equipment, but also makes it difficult to match the different power requirements of different equipment. Utility Model Content

[0004] The problem this invention addresses is how to improve the applicability of high-voltage linear DC excitation power supplies.

[0005] To address the aforementioned problems, this invention provides a high-voltage linear DC excitation power supply and a resistance measurement system.

[0006] In a first aspect, this utility model provides a high-voltage linear DC excitation power supply, including: a transformer, a first switching device and a rectifier, wherein the transformer includes a first primary winding, a first secondary winding, a second secondary winding and a third secondary winding, and the first switching device includes a first optocoupler relay, a second optocoupler relay and a third optocoupler relay.

[0007] The first primary winding is used to connect to an AC power supply. The first secondary winding is connected to the third pin of the first optocoupler relay. The second secondary winding is connected to the third pin of the second optocoupler relay. The third secondary winding is connected to the third pin of the third optocoupler relay. The fourth pins of the first optocoupler relay, the second optocoupler relay, and the third optocoupler relay are all connected to the input terminal of the rectifier. When the first pin of the first optocoupler relay, the first pin of the second optocoupler relay, or the first pin of the third optocoupler relay receives a high level, the circuit between the third pin and the fourth pin is connected.

[0008] The first pin is connected to the corresponding second pin via a light-emitting diode, and the third pin is connected to the corresponding fourth pin via a field-effect transistor and a photodiode.

[0009] Optionally, the high-voltage linear DC excitation power supply further includes a filter; the input terminal of the filter is connected to the output terminal of the rectifier, and the filter includes polarized capacitors, the number of which is greater than or equal to 2.

[0010] Optionally, the high-voltage linear DC excitation power supply further includes a voltage regulator, the input terminal of which is connected to the output terminal of the filter. The voltage regulator includes a first operational amplifier, an adjustment transistor, a voltage source circuit, a voltage regulator, and a sampling circuit. The first operational amplifier, the adjustment transistor, the voltage source circuit, the voltage regulator, and the sampling circuit constitute a negative feedback circuit.

[0011] Optionally, the non-inverting input of the first operational amplifier is connected to one end of the voltage source circuit, and the other end of the voltage source circuit is grounded; the inverting input of the first operational amplifier is connected to the feedback node of the sampling circuit; one end of the sampling circuit is connected to the output of the regulating transistor, and the other end of the sampling circuit is grounded; the output of the first operational amplifier is connected to the regulating terminal of the regulating transistor; the input of the regulating transistor is connected to the output of the filter; the output of the regulating transistor is used as the output of DC voltage; the enable terminal of the first operational amplifier is connected to one end of the voltage regulator, and the other end of the voltage regulator is grounded; the positive power supply terminal of the first operational amplifier is connected to the output of the filter; and the negative power supply terminal of the first operational amplifier is grounded.

[0012] Optionally, the sampling circuit includes a first resistor, a second resistor, and a potentiometer;

[0013] One end of the second resistor is connected to the output terminal of the regulating tube, and the other end of the second resistor is connected to one end of the first resistor to form a feedback node. The other end of the first resistor is connected to one end of the potentiometer, and the other end of the potentiometer is grounded. The inverting input terminal of the first operational amplifier is connected to the feedback node between the first resistor and the second resistor.

[0014] Optionally, the high-voltage linear DC excitation power supply further includes a second switching device, which includes a fourth optocoupler relay, a fifth optocoupler relay, and a sixth optocoupler relay, and the second resistor includes a first sub-resistor, a second sub-resistor, and a third sub-resistor.

[0015] The first resistor is connected in parallel with the second resistor, and the second resistor is connected in parallel with the third resistor. One end of the first resistor, one end of the second resistor, and one end of the third resistor are connected and connected to the output terminal of the regulating tube. The other end of the first resistor is connected to the third pin of the fourth optocoupler relay, the other end of the second resistor is connected to the third pin of the fifth optocoupler relay, and the other end of the third resistor is connected to the third pin of the sixth optocoupler relay. The fourth pins of the fourth, fifth, and sixth optocoupler relays are all connected to the first resistor. When the first pin of the fourth, fifth, or sixth optocoupler relay receives the high level, the circuit between the third and fourth pins is connected.

[0016] The first pin is connected to the corresponding second pin via the light-emitting diode, and the third pin is connected to the corresponding fourth pin via the field-effect transistor and the photodiode.

[0017] Optionally, the regulating transistor includes a first transistor and a second transistor;

[0018] The base of the first transistor is connected to the output terminal of the first operational amplifier, the emitter of the first transistor is connected to the base of the second transistor, the emitter of the second transistor is used as the output terminal of DC voltage, and the collectors of the first transistor and the second transistor are both connected to the output terminal of the filter.

[0019] The power of the first transistor is less than that of the second transistor.

[0020] Optionally, the temperature coefficients of the first resistor and the second resistor are 0.5 ppm / ℃, and the temperature coefficient of the potentiometer is 5 ppm / ℃.

[0021] Optionally, the rectifier includes a single-phase half-wave rectifier and a single-phase full-wave rectifier.

[0022] Secondly, this utility model provides a resistance measurement system, including a high-voltage linear DC excitation power supply as described in the first aspect.

[0023] The beneficial effects of this high-voltage linear DC excitation power supply and resistance measurement system are as follows: By setting up a transformer consisting of one primary winding and three secondary windings, the AC voltage output from the AC power supply can be converted into multiple AC voltages to meet the diverse power needs of the same equipment and the different power needs of different equipment, thereby improving the applicability of the high-voltage linear DC excitation power supply. By setting one optocoupler relay for each secondary winding, and the three optocoupler relays forming the first switching device, the on / off state of the AC voltage output from the corresponding secondary winding can be accurately controlled, ensuring that only the AC voltage output from one secondary winding is connected to the subsequent circuit, realizing the switching of multiple AC voltage outputs and avoiding mutual interference between different AC voltage outputs. The optocoupler relay includes a light-emitting diode (LED), a photodiode, and a field-effect transistor (FET). The LED and photodiode transmit control signals, and the FET conducts the main circuit, achieving electrical isolation between the control circuit and the main circuit. This not only reduces the impact of electromagnetic interference from the main circuit on the control circuit but also prevents damage to the control circuit from the high voltage in the main circuit, thus ensuring the stability of the entire high-voltage linear DC excitation power supply. By incorporating a rectifier, AC voltage can be converted into DC voltage to power the equipment. Therefore, this invention, through the inclusion of a transformer, a first switching device, and a rectifier, can output different DC voltages to meet various practical needs of the equipment, thus improving the applicability of the high-voltage linear DC excitation power supply. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the high-voltage linear DC excitation power supply in the embodiment of this utility model;

[0025] Figure 2 This is a circuit diagram of the first switching device in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the high-voltage linear DC excitation power supply in another embodiment of the present invention;

[0027] Figure 4 This is a circuit diagram of the voltage regulator in an embodiment of this utility model.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. First pin; 2. Second pin; 3. Third pin; 4. Fourth pin; OCR1, First optocoupler relay; OCR2, Second optocoupler relay; OCR3, Third optocoupler relay; LED, Light-emitting diode; MOS, Field-effect transistor; VD, Photodiode; Q1, First transistor; Q2, Second transistor; U, Voltage regulator; V, Voltage source circuit; A1, First operational amplifier; R1, First resistor; R2, Second resistor; R dwPotentiometer. Detailed Implementation

[0030] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Although some embodiments of this utility model are shown in the drawings, it should be understood that this utility model can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this utility model. It should be understood that the drawings and embodiments of this utility model are for illustrative purposes only and are not intended to limit the scope of protection of this utility model.

[0031] It should be understood that the steps described in the method embodiments of this utility model may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of this utility model is not limited in this respect.

[0032] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this utility model are only used to distinguish different devices, modules, or units, and are not used to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0033] It should be noted that the terms "one" and "multiple" used in this utility model are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0034] The names of the messages or information exchanged between the multiple devices in this embodiment of the invention are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0035] like Figure 1 and Figure 2 As shown in the figure, a high-voltage linear DC excitation power supply provided by this utility model embodiment includes: a transformer, a first switching device and a rectifier. The transformer includes a first primary winding, a first secondary winding, a second secondary winding and a third secondary winding. The first switching device includes a first optocoupler relay, a second optocoupler relay and a third optocoupler relay.

[0036] The first primary winding is used to connect to an AC power supply. The first secondary winding is connected to the third pin 3 of the first optocoupler relay. The second secondary winding is connected to the third pin 3 of the second optocoupler relay. The third secondary winding is connected to the third pin 3 of the third optocoupler relay. The fourth pin 4 of the first optocoupler relay, the fourth pin 4 of the second optocoupler relay, and the fourth pin 4 of the third optocoupler relay are all connected to the input terminal of the rectifier. When the first pin 1 of the first optocoupler relay, the first pin 1 of the second optocoupler relay, or the first pin 1 of the third optocoupler relay receives a high level, the circuit between the third pin 3 and the fourth pin 4 is turned on.

[0037] The first pin 1 is connected to the corresponding second pin 2 via a light-emitting diode (LED), and the third pin 3 is connected to the corresponding fourth pin 4 via a field-effect transistor (MOSFET) and a photodiode (VD).

[0038] Specifically, a transformer is an electrical device that operates on the principle of electromagnetic induction. Its main function is to convert mains power (220V) into different AC voltages (such as 44V, 88V, and 132V) to meet different output requirements. A transformer consists of a core and windings. The core is typically made of stacked silicon steel sheets for magnetic conduction, reducing magnetic resistance and improving electromagnetic conversion efficiency. The silicon steel sheets are insulated from each other, effectively reducing eddy current losses and ensuring efficient transformer operation. The windings include a first primary winding, a first secondary winding, a second secondary winding, and a third secondary winding. The first primary winding is connected to the AC power source and receives the input mains power; the first, second, and third secondary windings output different AC voltages according to the designed turns ratio. For example, when the turns ratio of the first secondary winding is 5:1, the output AC voltage is 44V; when the turns ratio of the second secondary winding is 5:2, the output AC voltage is 88V; and when the turns ratio of the third secondary winding is 5:3, the output AC voltage is 132V. Good insulation is required between the first primary winding and the first, second, and third secondary windings to prevent high-voltage breakdown and ensure safe circuit operation.

[0039] The relationship between the turns ratio and the input AC voltage and the output AC voltage satisfies the following formula:

[0040]

[0041] Where, N p For the primary winding, N s For the secondary winding, V p Input AC voltage, V s This is the output AC voltage.

[0042] The first switching device consists of three optocoupler relays, each corresponding to a secondary winding. Specifically, the first switching device comprises a first optocoupler relay, a second optocoupler relay, and a third optocoupler relay. The first optocoupler relay corresponds to the first secondary winding, the second optocoupler relay corresponds to the second secondary winding, and the third optocoupler relay corresponds to the third secondary winding. The secondary winding and optocoupler relays can be expanded as a module. If an additional voltage output level is needed, simply add one secondary winding and one optocoupler relay without requiring large-scale modifications to the overall circuit, thus reducing design and manufacturing costs and improving the scalability of the high-voltage linear DC excitation power supply. The first, second, and third optocoupler relays are all composed of light-emitting diodes (LEDs), photodiodes (VDs), and MOSFETs (Metal-Oxide-Semiconductor Transistors). The LEDs convert the input electrical signal (control signal) into a light signal. When a voltage (high level) is applied to pin 1, the LEDs emit light, displaying light of a specific wavelength. The photodiode VD receives the light signal emitted by the light-emitting diode (LED) and converts it back into an electrical signal through the photoelectric effect, thus transmitting the control signal. This electrical signal serves as the gate voltage of the field-effect transistor (MOSFET). When the gate voltage reaches the turn-on voltage, the MOSFET conducts, outputting the corresponding AC voltage to the secondary winding. Furthermore, because the first, second, and third optocoupler relays are independent of each other, and only one relay conducts at a time after receiving the electrical signal (control signal), it ensures that only the AC voltage output from the secondary winding is fed into the rectifier. This enables switching between different voltage output levels and avoids potential power supply failures or output anomalies caused by simultaneous output of multiple voltages.

[0043] Additionally, the second pin 2 of the first optocoupler relay, the second pin 2 of the second optocoupler relay, and the second pin 2 of the third optocoupler relay are grounded through the current-limiting resistor of the light-emitting diode (LED). In some embodiments, the resistance of the current-limiting resistor is 330Ω.

[0044] In some embodiments, the maximum withstand voltage of the first, second, and third optocoupler relays is 200V, and the load voltage is 400V. The maximum switching time of the first, second, and third optocoupler relays is 1.5ms, and the switching waiting time is 1s. During the switching waiting time, the first, second, and third optocoupler relays are all in the off state.

[0045] A rectifier is an electronic device that converts alternating current (AC) voltage into direct current (DC) voltage. The working principle of a rectifier is based on the conduction and cutoff characteristics of semiconductor devices (usually diodes or thyristors). In a simple single-phase rectifier circuit, when the AC voltage is positive, the diode conducts, allowing current to flow; when the AC voltage is negative, the diode is reverse-biased, cutting off the current. Thus, the rectifier outputs a pulsating DC voltage consisting of positive half-cycles.

[0046] In some embodiments, the DC voltage output by the high-voltage linear DC excitation power supply is 50V, 100V, or 150V.

[0047] In this embodiment, by setting up a transformer consisting of one primary winding and three secondary windings, the AC voltage output from the AC power supply can be converted into multiple AC voltages to meet the diverse power needs of the same equipment and the different power needs of different equipment, thereby improving the applicability of the high-voltage linear DC excitation power supply. By setting one optocoupler relay for each secondary winding, and the three optocoupler relays forming the first switching device, the on / off state of the AC voltage output from the corresponding secondary winding can be accurately controlled, ensuring that only the AC voltage output from one secondary winding is connected to the subsequent circuit, realizing the switching of multiple AC voltage outputs and avoiding mutual interference between different AC voltage outputs. The optocoupler relay includes a light-emitting diode (LED), a photodiode (VD), and a field-effect transistor (MOSFET). The LED and photodiode (VD) transmit control signals, and the MOSFET conducts the main circuit, achieving electrical isolation between the control circuit and the main circuit. This not only reduces the impact of electromagnetic interference from the main circuit on the control circuit but also prevents damage to the control circuit from the high voltage in the main circuit, thus ensuring the stability of the entire high-voltage linear DC excitation power supply. By setting up a rectifier, the AC voltage can be converted into DC voltage to power the equipment. Therefore, by setting up a transformer, a first switching device, and a rectifier, this utility model can output different DC voltages to meet various practical needs of the equipment and improve the applicability of the high-voltage linear DC excitation power supply.

[0048] Optionally, such as Figure 3 As shown, the high-voltage linear DC excitation power supply also includes a filter; the input terminal of the filter is connected to the output terminal of the rectifier, and the filter includes polarized capacitors, the number of which is greater than or equal to 2.

[0049] Specifically, because the DC voltage output by a rectifier contains a significant amount of AC components (ripple) and has a large ripple coefficient, filters can effectively reduce ripple, making the output DC voltage smoother and more stable to meet the equipment's requirements for a high-quality, high-voltage linear DC excitation power supply. Filters can utilize the charging and discharging characteristics of capacitors to achieve their filtering function. When the rectified DC voltage rises, the capacitor charges rapidly, storing energy; when the rectified DC voltage drops, the capacitor discharges slowly, releasing energy, thus effectively reducing ripple and making the DC voltage smoother and more stable. Filters can use multiple polarized capacitors connected in parallel at the positive and negative terminals of the rectifier output to jointly perform the filtering task. The number and capacity of the polarized capacitors are selected based on the power supply's output power and load characteristics. More polarized capacitors and larger capacities result in better filtering, but also increase cost and size.

[0050] In some embodiments, the filter includes three polarized capacitors with a capacitance of 2200 μF.

[0051] In this optional embodiment, after the rectifier converts AC voltage to DC voltage, the output DC voltage often contains a certain amount of ripple and lacks stability, which affects the reliability of equipment operation. By introducing a filter containing polarized capacitors, these ripples can be absorbed, making the output DC voltage smoother and more stable. This helps improve the quality of the high-voltage linear DC excitation power supply and meets the equipment's requirement for a high-quality high-voltage linear DC excitation power supply. Furthermore, compared to a single polarized capacitor, multiple polarized capacitors increase the capacitance and improve the filtering effect, better handling ripples of different frequencies and amplitudes, thus enhancing the applicability of the high-voltage linear DC excitation power supply.

[0052] Optionally, such as Figure 3 and Figure 4 As shown, the high-voltage linear DC excitation power supply also includes a voltage regulator. The input terminal of the voltage regulator is connected to the output terminal of the filter. The voltage regulator includes a first operational amplifier A1, an adjustment transistor, a voltage source circuit V, a voltage regulator U, and a sampling circuit. The first operational amplifier A1, the adjustment transistor, the voltage source circuit V, the voltage regulator U, and the sampling circuit constitute a negative feedback circuit.

[0053] Optionally, such as Figure 3 and Figure 4As shown, the non-inverting input of the first operational amplifier A1 is connected to one end of the voltage source circuit V, and the other end of the voltage source circuit V is grounded. The inverting input of the first operational amplifier A1 is connected to the feedback node of the sampling circuit. One end of the sampling circuit is connected to the output of the regulating transistor, and the other end of the sampling circuit is grounded. The output of the first operational amplifier A1 is connected to the regulating terminal of the regulating transistor. The input of the regulating transistor is connected to the output of the filter. The output of the regulating transistor is used as the output of DC voltage. The enable terminal of the first operational amplifier A1 is connected to one end of the voltage regulator U, and the other end of the voltage regulator U is grounded. The positive power supply terminal of the first operational amplifier A1 is connected to the output of the filter, and the negative power supply terminal of the first operational amplifier A1 is grounded.

[0054] Specifically, since the DC voltage after filtering still contains some ripple, a voltage regulator can further reduce the ripple and output a stable DC voltage. The DC voltage output from the filter passes through a sampling circuit to obtain a sampled voltage. The first operational amplifier A1 compares the sampled voltage with the reference voltage provided by the voltage source circuit V. When the sampled voltage and the reference voltage are inconsistent, the first operational amplifier A1 determines the error voltage based on the sampled voltage and the reference voltage, and amplifies the error voltage. The amplified error voltage drives the regulating transistor to adjust its conduction level, so that the output DC voltage is the preset DC voltage. Specifically, when the sampled voltage is greater than the reference voltage, that is, when the output DC voltage is greater than the preset DC voltage, the error voltage is positive, reducing the conduction level of the regulating transistor, causing the output DC voltage to decrease. When the sampled voltage is less than the reference voltage, that is, when the output DC voltage is less than the preset DC voltage, the error voltage is negative, increasing the conduction level of the regulating transistor, causing the output DC voltage to increase.

[0055] Furthermore, the first operational amplifier A1 is connected to a voltage regulator U, which provides an enable signal to the first operational amplifier A1. In some embodiments, the voltage regulator U is model AMS1117-3.3. The enable signal generated by the voltage regulator U is 3.3V. Grounding the first operational amplifier A1 reduces noise and interference in the circuit, thereby improving stability and anti-interference capability, while also protecting circuit safety.

[0056] In some embodiments, the voltage source circuit V includes a voltage source and a voltage regulator chip. When the voltage source delivers a 15V voltage to the voltage regulator chip, the voltage regulator chip outputs a 6.95V reference voltage. The voltage regulator chip is model LM399.

[0057] In this optional embodiment, by introducing a voltage regulator, the ripple in the filtered DC voltage is further reduced, making the output DC voltage more stable. This meets the needs of devices requiring high-precision and high-stability power supplies, improving the applicability of the high-voltage linear DC excitation power supply. The voltage regulator consists of a first operational amplifier A1, a regulating transistor, a voltage source circuit V, a voltage regulator U, and a sampling circuit. The first operational amplifier A1 compares the reference voltage provided by the voltage source circuit V with the sampling voltage provided by the sampling circuit to determine and amplify the error voltage. The conduction level of the regulating transistor is adjusted by the error voltage, thereby controlling the filtered DC voltage and ensuring the stability of the output DC voltage. The voltage regulator U provides an enable signal to ensure that the operational amplifier can operate normally.

[0058] Optionally, such as Figure 4 As shown, the sampling circuit includes a first resistor R1, a second resistor R2, and a potentiometer R. dw ;

[0059] One end of the second resistor R2 is connected to the output terminal of the regulating transistor, and the other end of the second resistor R2 is connected to one end of the first resistor R1 to form a feedback node. The other end of the first resistor R1 is connected to the potentiometer R. dw One end is connected to the potentiometer R. dw The other end is grounded, and the inverting input of the first operational amplifier A1 is connected to the feedback node between the first resistor R1 and the second resistor R2.

[0060] Specifically, the DC voltage processed by the filter is divided by the first resistor R1 and the second resistor R2 to obtain a sampling voltage proportional to the DC voltage. The potentiometer R... dw The settings allow for fine-tuning of the sampling voltage ratio to accommodate different voltage regulation accuracy requirements. The sampling voltage is fed into the inverting input of the first operational amplifier A1 and compared with the reference voltage at the non-inverting input of the first operational amplifier A1. The first operational amplifier A1 amplifies the difference between the two (error voltage) to adjust the conduction level of the regulating transistor, thereby precisely controlling the output DC voltage. The output DC voltage satisfies the following formula:

[0061]

[0062] Among them, V OUT It is the output DC voltage, V REF This is the reference voltage. R1 is the resistance of the first resistor, and R2 is the resistance of the second resistor. dw It is the resistance value of the potentiometer.

[0063] In some embodiments, the first operational amplifier A1 operates at 180V and 45mA.

[0064] In this optional embodiment, by selecting appropriate values ​​for the first resistor R1, the second resistor R2, and the potentiometer R... dw With a resistance range that allows for precise sampling of different output voltage ranges, voltage regulation control can be achieved, ensuring that the high-voltage linear DC excitation power supply can stably output the required DC voltage under various operating conditions.

[0065] Optionally, such as Figure 3 As shown, the high-voltage linear DC excitation power supply also includes a second switching device, which includes a fourth optocoupler relay, a fifth optocoupler relay and a sixth optocoupler relay, and the second resistor R2 includes a first resistor, a second resistor and a third resistor.

[0066] The first resistor is connected in parallel with the second resistor, and the second resistor is connected in parallel with the third resistor. One end of the first resistor, one end of the second resistor, and one end of the third resistor are connected and connected to the output terminal of the regulating tube. The other end of the first resistor is connected to the third pin 3 of the fourth optocoupler relay, the other end of the second resistor is connected to the third pin 3 of the fifth optocoupler relay, and the other end of the third resistor is connected to the third pin 3 of the sixth optocoupler relay. The fourth pin 4 of the fourth optocoupler relay, the fourth pin 4 of the fifth optocoupler relay, and the fourth pin 4 of the sixth optocoupler relay are all connected to the first resistor R1. When the first pin 1 of the fourth optocoupler relay, the first pin 1 of the fifth optocoupler relay, or the first pin 1 of the sixth optocoupler relay receives the high level, the circuit between the third pin 3 and the fourth pin 4 is turned on.

[0067] The first pin 1 is connected to the corresponding second pin 2 via the light-emitting diode (LED), and the third pin 3 is connected to the corresponding fourth pin 4 via the field-effect transistor (MOS) and the photodiode (VD).

[0068] Specifically, the second switching device consists of three optocoupler relays, each corresponding to a resistor division setting of the second resistor R2. More specifically, the second switching device comprises a fourth, fifth, and sixth optocoupler relay. The fourth optocoupler relay corresponds to the first resistor division setting of the second resistor R2, the fifth to the second, and the sixth to the third. The resistor division and optocoupler relays can be expanded as a module. If an additional voltage output level is needed, simply add a secondary winding, one resistor division, and two optocoupler relays. One optocoupler relay is added to the first switching device, and one to the second switching device. This improves the scalability of the high-voltage linear DC excitation power supply. The fourth, fifth, and sixth optocoupler relays are all composed of light-emitting diodes (LEDs), photodiodes (VDs), and MOSFETs. The LEDs convert the input electrical signal (control signal) into a light signal. When a voltage (high level) is applied to pin 1, the LEDs emit light of a specific wavelength. The photodiode VD receives the light signal emitted by the LED and converts it back into an electrical signal through the photoelectric effect, thus transmitting the control signal. This electrical signal serves as the gate voltage of the MOSFET. When the gate voltage reaches the turn-on voltage, the MOSFET conducts, outputting the sampling voltage corresponding to the second resistor R2. Furthermore, since the fourth, fifth, and sixth optocoupler relays are independent of each other, and only one relay receives the electrical signal (control signal) and conducts at any given time, it ensures that only the sampling voltage output from the second resistor R2 is fed into the inverting input of the first operational amplifier A1 and compared with the reference voltage at the non-inverting input of A1, thus switching between different resistance values ​​of the second resistor R2.

[0069] In some embodiments, if the voltage output levels are 50V, 100V, and 150V, and the three turns ratios of the transformer are 5:1, 5:2, and 5:3, then the transformer converts 220V AC mains power to 44V, 88V, and 132V AC voltages. After rectification and filtering, the 44V, 88V, and 132V AC voltages are converted to DC voltages of 50V, 100V, and 150V or higher. In the voltage regulator, the resistance values ​​of the three voltage dividers of the second resistor R2 are 56kΩ, 130kΩ, and 200kΩ, the resistance value of the first resistor R1 is 10kΩ, and the potentiometer R... dw The resistance range is 0Ω to 500Ω. The reference voltage provided by the voltage source circuit V is 6.95V. The enable signal generated by the voltage regulator U is 3.3V.

[0070] In this optional embodiment, since the sampling voltage is compared with a reference voltage, and the reference voltage is a fixed value, a second resistor R2 with a different resistance value is required. The resistance value of the second resistor R2, the resistance value of the first resistor R1, and the potentiometer R... dw The resistance values ​​are varied to create different voltage division ratios, sampling different DC voltages to obtain a sampled voltage that accurately reflects the current DC voltage magnitude. These different DC voltages are obtained by rectifying and filtering AC voltages at different levels. In this way, the final DC voltage output by the regulator can meet the various power requirements of the equipment, thereby improving the applicability of the high-voltage linear DC excitation power supply.

[0071] Optionally, such as Figure 4 As shown, the regulating transistor includes a first transistor Q1 and a second transistor Q2;

[0072] The base of the first transistor Q1 is connected to the output terminal of the first operational amplifier A1, the emitter of the first transistor Q1 is connected to the base of the second transistor Q2, the emitter of the second transistor Q2 is used as the output terminal of DC voltage, and the collectors of the first transistor Q1 and the second transistor Q2 are both connected to the output terminal of the filter.

[0073] The power of the first transistor Q1 is less than the power of the second transistor Q2.

[0074] Specifically, transistor Q1 amplifies the error voltage output by the operational amplifier and transmits the amplified error voltage to transistor Q2, driving Q2 to adjust its conduction level, thereby controlling the DC voltage after filtering and ensuring the stability of the output DC voltage. When transistor Q1 is working, the voltage difference between the collector and emitter is small, and using a low-power transistor not only meets the signal amplification requirements but also significantly reduces the cost of the voltage regulator. When transistor Q2 is working, the voltage difference between the collector and emitter is large, requiring a high-power transistor to ensure a stable output DC current.

[0075] In this optional embodiment, because the first transistor Q1 has lower power, it can quickly respond to the error voltage output by the operational amplifier, enabling timely adjustment of the output DC voltage. Because the second transistor Q2 has higher power, it can handle high-voltage DC voltage, ensuring a stable output of the high-voltage DC voltage. The regulating transistor, composed of the first transistor Q1 and the second transistor Q2, can reduce ripple in the DC voltage after filtering, resulting in a stable output DC voltage to meet the needs of devices requiring high-precision, high-stability power supplies.

[0076] Optionally, the temperature coefficient of the first resistor R1 and the second resistor R2 is 0.5 ppm / ℃, and the potentiometer R... dw The temperature coefficient is 5 ppm / ℃.

[0077] Specifically, in the sampling circuit, the first resistor R1 and the second resistor R2 are used to divide the DC voltage output after filtering. The temperature coefficient of the first resistor R1 and the second resistor R2 is 0.5 ppm / ℃, meaning that the relative change in resistance value is 0.00005% for every degree Celsius change in temperature. Specifically, if the temperature increases by 1℃, the resistance value increases by 0.00005% of the original value; if the temperature decreases by 1℃, the resistance value decreases by 0.00005% of the original value. The lower the temperature coefficient, the smaller the change in resistance value with temperature. This low temperature coefficient resistor can maintain a relatively stable resistance value when the ambient temperature changes, thus ensuring the stability of the sampled voltage. In the sampling circuit, potentiometer R... dw Used to fine-tune the voltage divider ratio to adapt to different voltage regulation accuracy requirements. Potentiometer R dw The temperature coefficient is 5 ppm / ℃, meaning that the relative change in resistance is 0.0005% for every degree Celsius change in temperature. This type of potentiometer R has a low temperature coefficient. dw It can maintain a relatively stable resistance value when the ambient temperature changes, thereby ensuring the stability of the sampling voltage.

[0078] In this optional embodiment, the first resistor R1, the second resistor R2, and the potentiometer R have low temperature coefficients. dw This allows the sampling circuit to maintain high sampling accuracy under different ambient temperatures, thereby improving the accuracy of voltage regulation control and ensuring a stable output DC voltage.

[0079] Optionally, the rectifier includes a single-phase half-wave rectifier and a single-phase full-wave rectifier.

[0080] Specifically, a single-phase half-wave rectifier typically consists of one diode. When the AC voltage is in the positive half-cycle, the diode conducts, and current flows through the load; when the AC voltage is in the negative half-cycle, the diode is cut off, and the current is interrupted. Therefore, the output pulsating DC voltage is formed by the positive half-cycle of the AC voltage. Single-phase half-wave rectifiers are suitable for applications with low output power and power quality requirements. A single-phase full-wave rectifier typically consists of four diodes, i.e., a single-phase bridge rectifier. When the AC voltage is in the positive half-cycle, one set of diodes conducts, current flows through the load, and the output current is forward. When the AC voltage is in the negative half-cycle, the other set of diodes conducts, current flows through the load, and the output current is forward. Therefore, the output pulsating DC voltage is formed by both the positive and negative half-cycles of the AC voltage. Single-phase full-wave rectifiers are suitable for applications with high output power and power quality requirements.

[0081] In this optional embodiment, by providing two different rectification methods, the high-voltage linear DC excitation power supply can meet a wider range of application needs. For some devices or scenarios with low power quality requirements, a single-phase half-wave rectifier can be selected to reduce costs and complexity; while for some devices or scenarios with high power quality requirements, a single-phase full-wave rectifier can be selected to ensure output stability and reliability. In this way, the applicability of the entire high-voltage linear DC excitation power supply is further improved.

[0082] This utility model provides a resistance measurement system, which includes the high-voltage linear DC excitation power supply as described above.

[0083] In some embodiments, the output terminal of the high-voltage linear DC excitation power supply is connected to one end of the resistor under test, the other end of the resistor under test is connected to one end of an ammeter, and the other end of the ammeter is grounded. The DC voltage output by the high-voltage linear DC excitation power supply is adjusted according to the approximate range of the resistance value of the resistor under test. The current flowing through the resistor under test is measured using the ammeter, and the resistance value is calculated according to Ohm's law.

[0084] The beneficial effects of the resistance measurement system in this embodiment correspond to the beneficial effects of the high-voltage linear DC excitation power supply described above, and will not be repeated here.

[0085] Although the present invention has been disclosed above, its protection scope is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the protection scope of the present invention.

Claims

1. A high voltage linear DC power supply, characterized by Includes: a transformer, a first switching device, and a rectifier. The transformer includes a first primary winding, a first secondary winding, a second secondary winding, and a third secondary winding. The first switching device includes a first optocoupler relay, a second optocoupler relay, and a third optocoupler relay. The first primary winding is used to connect to an AC power supply. The first secondary winding is connected to the third pin of the first optocoupler relay. The second secondary winding is connected to the third pin of the second optocoupler relay. The third secondary winding is connected to the third pin of the third optocoupler relay. The fourth pins of the first optocoupler relay, the second optocoupler relay, and the third optocoupler relay are all connected to the input terminal of the rectifier. When the first pin of the first optocoupler relay, the first pin of the second optocoupler relay, or the first pin of the third optocoupler relay receives a high level, the circuit between the third pin and the fourth pin is connected. The first pin is connected to the corresponding second pin via a light-emitting diode, and the third pin is connected to the corresponding fourth pin via a field-effect transistor and a photodiode.

2. The high voltage linear DC power supply of claim 1, wherein, It also includes a filter; the input terminal of the filter is connected to the output terminal of the rectifier, and the filter includes polarized capacitors, the number of which is greater than or equal to 2.

3. The high voltage linear DC power supply of claim 2, wherein, It also includes a voltage regulator, the input of which is connected to the output of the filter. The voltage regulator includes a first operational amplifier, an adjustment transistor, a voltage source circuit, a voltage regulator, and a sampling circuit. The first operational amplifier, the adjustment transistor, the voltage source circuit, the voltage regulator, and the sampling circuit constitute a negative feedback circuit.

4. The high voltage linear DC power supply of claim 3, wherein, The non-inverting input of the first operational amplifier is connected to one end of the voltage source circuit, and the other end of the voltage source circuit is grounded. The inverting input of the first operational amplifier is connected to the feedback node of the sampling circuit. One end of the sampling circuit is connected to the output of the regulating transistor, and the other end of the sampling circuit is grounded. The output of the first operational amplifier is connected to the regulating terminal of the regulating transistor. The input of the regulating transistor is connected to the output of the filter. The output of the regulating transistor is used as the output of DC voltage. The enable terminal of the first operational amplifier is connected to one end of the voltage regulator, and the other end of the voltage regulator is grounded. The positive power supply terminal of the first operational amplifier is connected to the output of the filter, and the negative power supply terminal of the first operational amplifier is grounded.

5. The high voltage linear DC power supply of claim 3, wherein, The sampling circuit includes a first resistor, a second resistor, and a potentiometer; One end of the second resistor is connected to the output terminal of the regulating tube, and the other end of the second resistor is connected to one end of the first resistor to form a feedback node. The other end of the first resistor is connected to one end of the potentiometer, and the other end of the potentiometer is grounded. The inverting input terminal of the first operational amplifier is connected to the feedback node between the first resistor and the second resistor.

6. The high voltage linear DC power supply of claim 5, wherein, It also includes a second switching device, which includes a fourth optocoupler relay, a fifth optocoupler relay and a sixth optocoupler relay, and the second resistor includes a first sub-resistor, a second sub-resistor and a third sub-resistor; The first resistor is connected in parallel with the second resistor, and the second resistor is connected in parallel with the third resistor. One end of the first resistor, one end of the second resistor, and one end of the third resistor are connected and connected to the output terminal of the regulating tube. The other end of the first resistor is connected to the third pin of the fourth optocoupler relay, the other end of the second resistor is connected to the third pin of the fifth optocoupler relay, and the other end of the third resistor is connected to the third pin of the sixth optocoupler relay. The fourth pins of the fourth, fifth, and sixth optocoupler relays are all connected to the first resistor. When the first pin of the fourth, fifth, or sixth optocoupler relay receives the high level, the circuit between the third and fourth pins is connected. The first pin is connected to the corresponding second pin via the light-emitting diode, and the third pin is connected to the corresponding fourth pin via the field-effect transistor and the photodiode.

7. The high voltage linear DC power supply of claim 3, wherein, The regulating transistor includes a first transistor and a second transistor; The base of the first transistor is connected to the output terminal of the first operational amplifier, the emitter of the first transistor is connected to the base of the second transistor, the emitter of the second transistor is used as the output terminal of DC voltage, and the collectors of the first transistor and the second transistor are both connected to the output terminal of the filter. The power of the first transistor is less than that of the second transistor.

8. The high voltage linear DC power supply of claim 5, wherein, The temperature coefficients of the first resistor and the second resistor are 0.5 ppm / ℃, and the temperature coefficient of the potentiometer is 5 ppm / ℃.

9. The high voltage linear DC power supply of claim 1, wherein, The rectifier includes a single-phase half-wave rectifier and a single-phase full-wave rectifier.

10. A resistance measurement system characterized by, Includes the high-voltage linear DC excitation power supply as described in any one of claims 1 to 9.

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