Constant-power load analog circuit, constant-power adjusting method and rack-mounted load box

Abstract

The invention provides a constant-power load analog circuit, a constant-power adjusting method and a rack-mounted load box, and belongs to the field of rack-mounted load boxs.The analog circuit comprises a rectifying circuit, a diverter, a power module, a fan module and a control and drive circuit, and the power module comprises at least one heating tube and at least one transistor. The control and drive circuit comprises a main control circuit, a voltage signal processing circuit, a current signal processing circuit, a power setting and display module and at least one IGBT drive circuit, the base electrode of the transistor is connected to the main control circuit through the IGBT drive circuit, and the power setting and display module is connected to the main control circuit and used for inputting a set power value. The main control circuit collects voltage and current of an external power supply, calculates a rated power value, calculates a signal duty ratio according to a set power value and the rated power value, outputs a PWM wave, controls on or off of a transistor through the IGBT driving circuit, dynamically adjusts actual output power of the load simulation circuit to be consistent with the set power value, and controls the load simulation circuit to work. And the power regulation precision of the load box is improved.

Description

Technical Field

[0001] The invention relates to the technical field of rack-type load boxes, and in particular to a constant power rack-type load box. Background Art

[0002] A load bank is an electrical load that is usually applied to a power source and converts or dissipates power. The function of a load bank is to simulate the actual load of a power source in actual application and use its energy output to test, support or protect the power source. Since real loads are scattered, unpredictable and random, load banks need to provide a wide range of operating characteristics and a load with controllable capacity. Load banks are usually used together with generator sets, battery systems, UPS systems, inverters, etc. as test units to test the above equipment.

[0003] After the construction of a data center is completed and before it is put into operation, it is necessary to perform load testing on the equipment and routes on the site. That is, the electrical characteristics of the equipment and routes are stress-tested by connecting a mobile load box or a rack-mounted load box, and the heat generated by the load box is used to provide a heat load for the cooling system to achieve load testing.

[0004] Load boxes are divided into resistive load boxes, inductive load boxes and capacitive load boxes according to electrical characteristics, among which resistive load boxes are the most widely used. The fixed ears of rack-mounted resistive load boxes are used for installation on the mounting rack in the cabinet. Server cabinets are usually used to install standard 19-inch wide equipment. Therefore, rack-mounted load boxes use the same specifications as servers, with a width of 19 inches, and the height varies according to the output power of the load box, usually including 1U (1U = 4.445cm), 2U, 4U, 5U and other heights. Its installation form in the cabinet is as follows: Figure 1 As shown in the figure, the airspace in the cabinet is blocked with blind panels to meet the requirements of isolating the hot and cold channels.

[0005] In the data center test verification phase, the typical load box power supply topology is as follows Figure 2 As shown in Figure 1, the load box is usually at the end of the entire power supply topology and consumes electrical energy as a power load and converts it into heat energy. Currently, the output power of rack-mounted resistive load boxes is adjusted manually, such as Figure 3As shown, the load box configures resistive heating tubes of different powers on the internal circuit, and then sets a switch device such as a circuit breaker or contactor for switching control in each circuit to put the resistive heating tube into operation or cut off the operation, thereby adjusting the power of the entire load box. There are currently two main types of heating tube materials: the first is a dry-burning electric heating tube, which is a tubular electric heating element. It is composed of a metal tube spiral resistance wire and crystalline magnesium oxide powder. The high-temperature resistance wire is evenly distributed in the stainless steel seamless tube, and the gap is filled with crystalline magnesium oxide powder with good thermal conductivity and insulation properties. The structure is relatively advanced, the thermal efficiency is high, and the heat is uniform. When current passes through the high-temperature resistance wire, the heat generated is diffused to the surface of the metal tube through the magnesium oxide powder, and then transferred to the heated part or the air to achieve the purpose of heating. The heat generated by the electric heating tube (i.e., the power consumed) is proportional to the square of the voltage and the square of the current. The second type of heating tube material is a PTC heater, which is composed of a PTC ceramic heating element and an aluminum tube. It has the advantages of low thermal resistance and high heat exchange efficiency. It is an automatic constant temperature and energy-saving electric heater. It consists of a galvanized outer pressure plate, a stainless steel corrugated spring sheet, a galvanized inner pressure plate, a single-layer aluminum heat sink, a PTC heating sheet, a double-layer aluminum heat sink, a nickel-plated copper electrode terminal and a high-temperature plastic electrode sheath.

[0006] At present, rack-mounted resistive load boxes have the following shortcomings: (1) Different power combinations are achieved by switching on and off heating devices (including electric heating tubes and PTC heaters) of different powers. Although the initial power can be adjusted and selected, the accuracy is poor. The power adjustment span of most resistive load boxes is at the order of 500W, which cannot achieve a more accurate setting of the power; (2) The fan does not have speed control. After the equipment is powered on, no matter what the power setting value of the equipment is, the fan is at full speed. Although it can play a good heat dissipation role, it causes the equipment to enter and exit. The wind temperature difference is not fixed and cannot simulate the actual operating conditions of the server and other equipment in the computer room; (3) For the load box using dry-burning electric heating tubes, when the power supply voltage changes, since the resistance of the dry-burning electric heating tubes will basically not change at the stable operating temperature, according to Ohm's law, its output power will fluctuate with the voltage fluctuation, thereby affecting the power supply side and the cooling side; (4) For the load box using PTC heating tubes, when the equipment inlet temperature, fan air volume, equipment altitude, internal structure, etc. change, its output power will also change. Summary of the invention

[0007] The technical problem to be solved by the present invention is how to improve the accuracy of power regulation of a rack-type load box.

[0008] The present invention solves the above technical problems through the following technical solutions: a constant power load simulation circuit, the simulation circuit includes a rectifier circuit, a shunt, a power module, a fan module, a control and drive circuit, the power module includes at least one heating tube, at least one transistor, the control and drive circuit includes a main control circuit, a voltage signal processing circuit, a current signal processing circuit, a power setting and display module, at least one IGBT drive circuit, the input end of the rectifier circuit is connected to an external power supply, the output negative electrode of the rectifier circuit is connected in series with the shunt and then connected to the emitter of the transistor, the output positive electrode of the rectifier circuit is connected in series with the heating tube and then connected to the collector of the transistor, and the base of the transistor is connected to the collector of the transistor. The positive pole is connected to the main control circuit through the IGBT driving circuit, the output positive pole of the rectifier circuit is connected to the main control circuit through the voltage signal processing circuit, the two ends of the shunt are connected to the main control circuit through the current signal processing circuit, the fan module is connected between the rectifier circuit and the main control circuit, the power setting and display module is connected to the main control circuit for inputting the set power value, the main control circuit collects the voltage and current of the external power supply and calculates the rated power value, calculates the signal duty cycle according to the set power value and the rated power value, and outputs a PWM wave to control the conduction or shutdown of the transistor through the IGBT driving circuit, and dynamically adjusts the actual output power of the load box to keep it consistent with the set power value.

[0009] The constant power load simulation circuit of the present invention collects the voltage signal and the current signal of the external input power supply, calculates the rated power value, calculates the signal duty cycle according to the set power value and the rated power value, and the main control circuit outputs a PWM wave according to the value of the signal duty cycle, controls the on or off of the transistor through the IGBT drive circuit, adjusts the ratio of the load input time to the total time, and realizes that the output power of the load simulation circuit is equal to the set power value, thereby realizing dynamic adjustment of the actual output power of the load simulation circuit and keeping it consistent with the set power value, realizing that the power of the load simulation circuit can be automatically adjusted to the set power according to the change of the external input power supply, and realizing closed-loop control of the power.

[0010] Preferably, the power module also includes at least one DC contactor and at least one temperature sensing element, the control and drive circuit also includes a relay control circuit, the DC contactor is connected between the output positive pole of the rectifier circuit and the heating tube, the control port of the DC contactor is connected to the main control circuit through the relay control circuit, and the temperature sensing element is close to the heating tube for measuring the temperature of the heating tube and inputting the temperature signal into the main control circuit through the relay control circuit.

[0011] Preferably, the main control circuit includes a main control chip, a crystal oscillator Y1, a capacitor C6, and a capacitor C20. The main control chip adopts a single-chip microcomputer. The first pin of the single-chip microcomputer is connected to the output end of the voltage signal processing circuit, the second pin of the single-chip microcomputer is connected to the output end of the current signal processing circuit, the fourteenth pin of the single-chip microcomputer is respectively connected to one end of the crystal oscillator Y1 and one end of the capacitor C20, the fifteenth pin of the single-chip microcomputer is respectively connected to the other end of the crystal oscillator Y1 and one end of the capacitor C8, the other end of the capacitor C8 is connected to the other end of the capacitor C20 and then grounded, the thirty-first pin, the thirty-second pin, and the thirty-third pin of the single-chip microcomputer are respectively connected to the IGBT drive circuit, and the forty-fourth pin of the single-chip microcomputer is connected to the output end of the power setting and display module.

[0012] Preferably, the voltage signal processing circuit includes a rectifier chip D6, a voltage zener diode D7, a capacitor C16, a capacitor C26, a resistor R40, and a resistor R41. The second pin and the third pin of the rectifier chip D6 are respectively connected to the two output ends of the rectifier circuit, the first pin of the rectifier chip D6 is respectively connected to the positive plate of the capacitor C16 and one end of the resistor R40, the other end of the resistor R40 is respectively connected to one end of the resistor R41, the cathode of the voltage zener diode D7, one end of the capacitor C26, and the first pin of the main control chip, and the fourth pin of the rectifier chip D6 is respectively connected to the negative plate of the capacitor C16, the other end of the resistor R41, the anode of the voltage zener diode D7, the other end of the capacitor C26 and grounded.

[0013] Preferably, the number of the multiple IGBT drive circuits is the same as the number of the multiple heating tubes and corresponds to the heating tubes one by one. The IGBT drive circuit includes a switch tube Q3, a switch tube Q4, a switch tube Q5, a switch tube Q6, a voltage regulator diode D5, a resistor R19, a resistor R20, a resistor R23, and a resistor R24. One end of the resistor R24 ​​is connected to the thirty-third pin of the main control chip, and the other end of the resistor R24 ​​is connected to the base of the switch tube Q5. The collector of the switch tube Q5 is respectively connected to one end of the resistor R19, one end of the resistor R20, the base of the switch tube Q3, the switch tube Q6, and the base of the switch tube Q5. The base of the switch tube Q6, the other end of the resistor R19, the other end of the resistor R20, and the collector of the switch tube Q3 are connected, then connected to the cathode of the voltage-stabilizing diode D5 and connected to an 18V power supply. The anode of the voltage-stabilizing diode D5 is grounded. The emitter of the switch tube Q3 is respectively connected to the emitter of the switch tube Q6 and one end of the resistor R23. The other end of the resistor R23 is connected to the gate of the switch tube Q4. The source of the switch tube Q4 is connected to one end of the first heating tube. The emitter of the switch tube Q5, the collector of the switch tube Q6, and the drain of the switch tube Q4 are connected, then connected to the other end of the first heating tube and grounded.

[0014] Preferably, the load simulation circuit also includes a temperature probe, the control and drive circuit also includes a temperature sampling circuit, the temperature sampling circuit includes a resistor R18 and a capacitor C21, one end of the resistor R18 is respectively connected to one end of the temperature probe, one end of the capacitor C21, and the 42nd pin of the main control chip, the other end of the resistor R18 is connected to a 5V voltage, and the other end of the capacitor C21 is connected to the other end of the temperature probe and grounded.

[0015] Preferably, the control and drive circuit also includes an air volume setting and display module and a fan speed control circuit. The air volume setting and display module is connected to the main control circuit for inputting the set air volume value. The fan speed control circuit is connected between the main control circuit and the fan module. The main control circuit inputs a control signal to the fan speed control circuit according to the signal duty cycle to achieve air volume regulation.

[0016] Preferably, the power setting and display module and the air volume setting and display module both include an adjustable resistance circuit and a voltage conversion and display circuit. The power setting and display module adjusts the magnitude of the input signal voltage through the knob of the adjustable resistance and inputs it into the A / D port in the main control circuit. The signal undergoes voltage conversion synchronously to convert the voltage value of the input signal into a voltage value equal to the set power value, and is connected to the voltage meter to display the set power value. The air volume setting and display module adjusts the magnitude of the input signal voltage through the knob of the adjustable resistance and inputs it into the A / D port in the main control circuit. The signal undergoes voltage conversion synchronously to convert the voltage value of the input signal into a voltage value equal to the set fan speed value, and is connected to the voltage meter to display the set speed value.

[0017] Preferably, the control and drive circuit further includes a power switching and DC / DC conversion circuit, which includes a chip U1, a chip U2, a MOS tube M1, a MOS tube M2, a MOS tube M3, a MOS tube M4, a diode D1, a diode D2, capacitors C1-C7, capacitors C9-C15, a capacitor C17, resistors R4-R9, resistors R11-R14, and a resistor R16, one end of the resistor R8 is respectively connected to the anode of the diode D1 and the anode of the diode D2 and connected to the positive electrode of the 24V input power supply, the other end of the resistor R8 is respectively connected to one end of the resistor R12 and the gate of the MOS tube M3, and the other end of the resistor R12 is respectively connected to the M The source of MOS tube M3, one end of resistor R11, and the source of MOS tube M4 are grounded. The drain of MOS tube M3 is connected to one end of resistor R4, the other end of resistor R11, and the gate of MOS tube M4 respectively. The drain of MOS tube M4 is connected to one end of resistor R9. The other end of resistor R4 is connected to the source of MOS tube M1 and the positive electrode of another 24V input power supply. The other end of resistor R9 is connected to the gate of MOS tube M1, one end of resistor R5, and the gate of MOS tube M2 respectively. The other end of resistor R5 is connected to the drain of MOS tube M1 and the drain of MOS tube M2. The source of MOS tube M2 is connected to the cathode of diode D1, the cathode of diode D2, and the positive electrode of diode D3 respectively. One end of resistor R6, one end of capacitor C1, one end of capacitor C2, one end of capacitor C3, and the first pin of chip U2; the other end of resistor R6 is connected in series with resistor R14 and respectively connected to one end of capacitor C13, one end of capacitor C14, one end of capacitor C15, and the third pin of chip U1; the other end of capacitor C1, the other end of capacitor C2, the other end of capacitor C3, one end of capacitor C4, one end of capacitor C5, one end of capacitor C6, and one end of capacitor C7 are connected to one end of resistor R7 and then grounded; the other end of resistor R7 is connected to the third pin of chip U2, one end of resistor R13, the other end of resistor R13, the other end of capacitor C4, the other end of capacitor C5, and capacitor C6 The other end of capacitor C7, the other end of the second pin of chip U2 are connected and then connected to 18V voltage, the other end of capacitor C13, the other end of capacitor C14, the other end of capacitor C15, one end of capacitor C17, and the first pin of chip U1 are connected and then grounded, the second pin of chip U1 is respectively connected to one end of capacitor C9, one end of capacitor C10, one end of capacitor C11, one end of capacitor C12, and the thirty-eighth pin of the main control chip and are connected to 5V voltage, the other end of capacitor C9, the other end of capacitor C10, and the other end of capacitor C11 are connected and then connected to one end of resistor R16 and grounded, and the other end of resistor R16 is respectively connected to the other end of capacitor C12 and the fourth pin of the main control chip.

[0018] The present invention also provides a constant power regulation method, which is applied to the constant power load simulation circuit. The power setting and display module inputs the set power value into the main control circuit. The main control circuit collects the voltage of the external power supply and calculates the rated power value. The signal duty cycle is calculated according to the set power value and the rated power value, and a PWM wave is output to control the on or off of the transistor through the IGBT drive circuit. The main control circuit collects the current of the external power supply to fine-tune the signal duty cycle, and dynamically adjusts the actual output power of the load simulation circuit to keep it consistent with the set power value.

[0019] The present invention also provides a rack-type load box, comprising the constant power load simulation circuit and a box body, wherein the load simulation circuit is located in the box body.

[0020] The advantages provided by the present invention are:

[0021] (1) The constant power load simulation circuit of the present invention collects the voltage signal and current signal of the external input power supply and calculates the rated power value. The signal duty cycle is calculated according to the set power value and the rated power value. The main control circuit outputs a PWM wave according to the value of the signal duty cycle, and controls the on or off of the transistor through the IGBT drive circuit to adjust the ratio of the load input time to the total time, so that the output power of the load simulation circuit is equal to the set power value, thereby realizing dynamic adjustment of the actual output power of the load simulation circuit and keeping it consistent with the set power value, so that the power of the load simulation circuit can be automatically adjusted to the set power according to the change of the external input power supply, thereby realizing closed-loop control of the power.

[0022] (2) The present invention takes into account that the heating tube will change slightly with temperature and usage time, thereby affecting the power accuracy. By collecting current signals, calculating the power of the current system and comparing it with the set power, and then fine-tuning the duty cycle, the closed-loop control of the output power is achieved, which can further improve the accuracy of the power regulation of the rack-mounted load box.

[0023] (3) The present invention arranges a temperature sensing element near the heating tube. When the temperature of the heating tube measured by the temperature sensing element exceeds a set threshold value, which may cause the heating tube to burn out, the main control circuit controls the relay control circuit to output a drive signal, controls the DC contactor to disconnect, disconnects the circuit where the heating tube is located, and stops working, thereby protecting the heating tube.

[0024] (4) The present invention can connect multiple heating tubes in parallel in the power module according to the load size of the object to be tested (such as a data center). When three heating tubes are connected in parallel and the rated power of each heating tube is 2kW, the load box can be adjusted in power from 0 to 6kW.

[0025] (5) The present invention can collect the temperature inside the load box by setting a temperature sampling circuit, perform temperature compensation on the actual working resistance of the heating tube, and further improve the adjustment accuracy of the load box power.

[0026] (6) The present invention sets an air volume setting and display module for inputting the set air volume value. The main control circuit inputs a control signal to the fan speed regulation circuit according to the signal duty cycle to achieve air volume regulation. This can solve the problem in the prior art that the fans are all running at full speed, resulting in an unstable inlet and outlet temperature difference of the equipment, and cannot simulate the actual operating conditions of the server and other equipment in the computer room. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of installing a rack-type resistive load box in a cabinet in the prior art;

[0028] Figure 2 A power supply topology diagram of a data center connected to a load box in the prior art;

[0029] Figure 3 It is a schematic diagram of the output power regulation principle of a rack-type resistive load box in the prior art by switching heating tubes with different powers;

[0030] Figure 4 A schematic diagram of a constant power load simulation circuit provided by an embodiment of the present invention;

[0031] Figure 5 A schematic diagram of a control and drive circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0032] Figure 6 A circuit diagram of a main control circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0033] Figure 7 A circuit diagram of a voltage signal processing circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0034] Figure 8 A circuit diagram of an IGBT driving circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0035] Fig. 9 A circuit diagram of another IGBT driving circuit in the constant power load simulation circuit provided by an embodiment of the present invention;

[0036] Fig.10 A circuit diagram of another IGBT driving circuit in the constant power load simulation circuit provided by an embodiment of the present invention;

[0037] Fig.11 A circuit diagram of a temperature sampling circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0038] Fig.12 A circuit diagram of a voltage conversion and display circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0039] Fig.13 A circuit diagram of a fan speed regulating circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0040] Fig.14 A circuit diagram of a power supply switching and DC / DC conversion circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0041] Fig.15 A circuit diagram of a signal voltage conversion circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0042] Fig.16 A circuit diagram of a 2.5V reference voltage circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0043] Fig.17 A circuit diagram of a burning and communication circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0044] Fig.18 A circuit diagram of an indicating circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0045] Fig.19 A circuit diagram of an alarm circuit in a constant power load simulation circuit provided by an embodiment of the present invention;

[0046] Fig. 20 A schematic diagram of the arrangement of various modules in a rack-type load box provided in an embodiment of the present invention;

[0047] In the figure: 10 rectifier circuit, 20 shunt, 30 power module, 40 fan module, 50 control and drive circuit, 51 main control circuit, 52 voltage signal processing circuit, 53 current signal processing circuit, 54 power setting and display module, 55 IGBT drive circuit, 56 relay control circuit, 57 temperature sampling circuit. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the technical solution of the present invention is clearly and completely described below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0049] Explanation of relevant terms:

[0050] Rack-mounted load box: A load box that meets the external dimensions and structural components of a standard 19-inch rack installation.

[0051] Constant power: refers to constant output power, that is, as external conditions change, the power consumption of the equipment can remain constant.

[0052] Duty cycle: refers to the proportion of power-on time to the total time in a pulse cycle.

[0053] Example 1

[0054] like Figure 4 As shown, this embodiment provides a constant power load simulation circuit, including a rectifier circuit 10, a shunt 20, a power module 30, a fan module 40, and a control and drive circuit 50. The power module 30 includes at least one heating tube and at least one transistor. Figure 5 The control and drive circuit 50 includes a main control circuit 51, a voltage signal processing circuit 52, a current signal processing circuit 53, a power setting and display module 54, and at least one IGBT drive circuit 55. The input end of the rectifier circuit 10 is connected to an external power supply, the output negative electrode of the rectifier circuit 10 is connected in series with the shunt 20 and then connected to the emitter of the transistor, the output positive electrode of the rectifier circuit 10 is connected in series with the heating tube and then connected to the collector of the transistor, the base of the transistor is connected to the main control circuit 51 through the IGBT drive circuit 55, and the output positive electrode of the rectifier circuit 10 is connected to the collector of the transistor through the voltage signal processing circuit 52. The main control circuit 51, both ends of the shunt 20 are connected to the main control circuit 51 through the current signal processing circuit 53, the fan module 40 is connected between the rectifier circuit 10 and the main control circuit 50, and the power setting and display module 54 is connected to the main control circuit 51 for inputting the set power value. The main control circuit 51 collects the voltage and current of the external power supply and calculates the rated power value, calculates the signal duty cycle according to the set power value and the rated power value, and outputs the PWM wave to control the conduction or shutdown of the transistor through the IGBT drive circuit 55, and dynamically adjusts the actual output power of the load box to keep it consistent with the set power value. Signal duty cycle = set power value / rated power value.

[0055] The existing load box inputs a certain resistance through a switch, and the power adjustment accuracy is the minimum power that can be input individually. Due to the number of load branches, it is impossible to achieve a large power adjustment span. Most resistive load boxes on the market have a power adjustment span of 500W or 1000W, and a very small number have a power adjustment span of 100W. However, there is still a problem of large power span and inability to automatically adjust power according to changes in input power.

[0056] The present invention achieves that the output power of the load box is equal to the set power by adjusting the ratio of the load input time to the total time. For example, when the output power of the load box is required to be 100% of the rated power of the equipment, the set power is equal to the rated power of the load box, and the ratio is equal to 1, that is, the resistance of the load box is always input, and the output power of the load box is equal to the rated power. When the output power of the load box is required to be 50% of the rated power of the equipment, the set power is equal to 50% of the rated power of the load box, and the ratio is equal to 0.5, that is, the resistance of the load box is only 50% input per unit time, and the output power of the load box is equal to 50% of the rated power. The remaining ratios are similar. The present invention adjusts the power by adjusting the ratio, that is, the time parameter. The main control circuit has high control accuracy over time, compared with Figure 3 In the invention, heating devices of different powers are switched on and off by switches to realize combinations of different powers, and the power regulation accuracy of the invention is very high.

[0057] The main control circuit 51 collects the current of the external power supply for fine-tuning the signal duty cycle. When the deviation between the rated power value and the set power value exceeds the set threshold, the main control circuit 51 calculates the current power value according to the collected current, and fine-tunes the signal duty cycle according to the magnitude of the current power value and the rated power value. If the current power value is greater than the rated power value, the signal duty cycle is fine-tuned to reduce the signal duty cycle. If the current power value is less than the rated power value, the signal duty cycle is fine-tuned to increase the signal duty cycle until the deviation between the rated power value and the set power value is within the set threshold. The present invention takes into account that the heating tube will change slightly with the temperature and the length of use, thereby affecting the power accuracy. By collecting the current signal, calculating the power of the current system, and comparing it with the set power, and then fine-tuning the duty cycle, the closed-loop control of the output power is realized, which can further improve the accuracy of the power regulation of the rack-mounted load box.

[0058] The input end of the rectifier circuit 10 is connected to an external power supply, and is used to rectify the external input voltage and output it. It supports AC220V and DC270V input, with a minimum power of 8kW. A bridge rectifier module with a heat sink is selected, and the model is MDQ100A.

[0059] The input end of the shunt 20 is connected to the output end of the rectifier circuit 10, and the output end of the shunt 20 is connected to the emitter of the transistor. The shunt is connected to the main control circuit 51 through the current signal processing circuit 53, and is used to collect the current signal in the line and input it to the main control circuit 51. The shunt uses a 30A / 75mV high-precision shunt, model FL-2.

[0060] Continue reading Figure 4 and Figure 5The power module 30 also includes at least one DC contactor and at least one temperature sensing element. The control and drive circuit 50 also includes a relay control circuit 56. The DC contactor is connected between the output positive electrode of the rectifier circuit 10 and the heating tube. The control port of the DC contactor is connected to the main control circuit 51 through the relay control circuit 56. The temperature sensing element is close to the heating tube and is used to measure the temperature of the heating tube and input the temperature signal to the main control circuit 51 through the relay control circuit 56. When the temperature of the heating tube measured by the temperature sensing element exceeds the set threshold value, which may cause the heating tube to burn, the main control circuit 51 controls the relay control circuit 56 to output a drive signal, controls the DC contactor to disconnect, and disconnects the circuit where the heating tube is located, stops working, and protects the heating tube.

[0061] The number of heating tubes in the power module is determined according to the load size of the object to be measured (such as a data room). When multiple heating tubes are selected, the multiple heating tubes are connected in parallel, and each branch where the heating tube is located is connected to a DC contactor and a transistor. There is a temperature sensing element near each heating tube. In this embodiment, three heating tubes are connected in parallel, namely the first heating tube, the second heating tube, and the third heating tube. Each heating tube adopts a dry-burning electric heating tube with a rated power of 2kW. One end of the first DC contactor, one end of the second DC contactor, and one end of the third DC contactor are connected to the output end of the rectifier circuit. The other end of the first DC contactor is connected in series with the first heating tube and then connected to the collector of the first transistor. The other end of the second DC contactor is connected in series with the second heating tube and then connected to the collector of the second transistor. The other end of the third DC contactor is connected in series with the third heating tube and then connected to the collector of the third transistor. The base of the first transistor, the base of the second transistor, and the base of the third transistor are respectively connected to the input end of the IGBT drive circuit, and the output end of the IGBT drive circuit is connected to the main control circuit. The control ports of the first DC contactor, the second DC contactor, and the third DC contactor are all connected to the output end of the relay control circuit, and the input end of the control circuit is connected to the main control circuit. By controlling the conduction time of the first transistor, the second transistor, and the third transistor, the load box can be adjusted in power from 0 to 6kW.

[0062] like Figure 6As shown, the main control circuit 51 includes a main control chip, a crystal oscillator Y1, a capacitor C6, and a capacitor C20. The main control chip adopts a single-chip microcomputer, and the model is STC90C58AD. The model of the crystal oscillator Y1 is CRYSTAL-1. The first pin of the single-chip microcomputer is connected to the output end of the voltage signal processing circuit 52, the second pin of the single-chip microcomputer is connected to the output end of the current signal processing circuit 53, the fourteenth pin of the single-chip microcomputer is respectively connected to one end of the crystal oscillator Y1 and one end of the capacitor C20, the fifteenth pin of the single-chip microcomputer is respectively connected to the other end of the crystal oscillator Y1 and one end of the capacitor C8, the other end of the capacitor C8 is connected to the other end of the capacitor C20 and then grounded, the thirty-first pin, the thirty-second pin, and the thirty-third pin of the single-chip microcomputer are respectively connected to the IGBT drive circuit 55, and the forty-fourth pin of the single-chip microcomputer is connected to the output end of the power setting and display module 54. The main control chip has an AD port and a multi-channel IO output port, and has a high degree of integration. It can easily collect the analog quantity and switch quantity of the system, and output PWM signals and control signals.

[0063] See also Figure 5 The voltage signal processing circuit 52 includes a voltage sampling circuit and a peak holding circuit. The external voltage signal is input into the voltage sampling circuit for sampling. The sampling signal is input into the peak holding circuit for filtering to obtain the voltage waveform peak value, which is then input into the first pin of the main control chip.

[0064] like Figure 7 As shown, the voltage signal processing circuit 52 includes a rectifier chip D6, a voltage stabilizing diode D7, a capacitor C16, a capacitor C26, a resistor R40, and a resistor R41. The second pin and the third pin of the rectifier chip D6 are respectively connected to the two output ends of the rectifier circuit, the first pin of the rectifier chip D6 is respectively connected to the positive plate of the capacitor C16 and one end of the resistor R40, the other end of the resistor R40 is respectively connected to one end of the resistor R41, the cathode of the voltage stabilizing diode D7, one end of the capacitor C26, and the first pin of the main control chip, and the fourth pin of the rectifier chip D6 is respectively connected to the negative plate of the capacitor C16, the other end of the resistor R41, the anode of the voltage stabilizing diode D7, the other end of the capacitor C26 and grounded. The model of the rectifier chip D6 is ABS210. The use of the rectifier chip enables the circuit to adapt to both AC and DC power inputs, and the power supply peak value is obtained through the peak holding voltage composed of the capacitor, the voltage divider voltage composed of the resistor, and the overvoltage protection of the voltage stabilizing diode.

[0065] The current signal processing circuit 53 includes an amplifier circuit and a peak holding circuit. The current signal collected by the shunt is input into the amplifier circuit, the signal after amplification is input into the peak holding circuit, and the peak value of the current waveform output after filtering is input into the second pin of the main control chip. The amplifier circuit of the current signal processing circuit of the present invention can adopt an existing amplifier circuit, and the peak holding circuit can adopt a peak holding circuit in the voltage signal processing circuit.

[0066] The relay control circuit 56 includes a three-position, two-speed selection switch, whose power comes from the 24V power supply of the main board. The operator controls the contactor to be closed or disconnected by switching the gear of the selection switch. At the same time, the drive signal of the contactor is connected in series with the temperature control switch of the heating tube controlled by each contactor, so that the operator can control the input / output of the heating tube and the over-temperature protection of the heating tube.

[0067] like Figure 8 As shown, the IGBT drive circuit 55 includes a switch tube Q3, a switch tube Q4, a switch tube Q5, a switch tube Q6, a voltage stabilizing diode D5, a resistor R19, a resistor R20, a resistor R23, and a resistor R24. One end of the resistor R24 ​​is connected to the thirty-third pin of the main control chip, and the other end of the resistor R24 ​​is connected to the base of the switch tube Q5. The collector of the switch tube Q5 is respectively connected to one end of the resistor R19, one end of the resistor R20, the base of the switch tube Q3, and the base of the switch tube Q6. The other end of the resistor R19, the resistor R20, the base of the switch tube Q3, and the base of the switch tube Q6 are connected. The other end of the resistor R20 and the collector of the switch tube Q3 are connected to the cathode of the voltage-stabilizing diode D5 and connected to an 18V power supply. The anode of the voltage-stabilizing diode D5 is grounded. The emitter of the switch tube Q3 is respectively connected to the emitter of the switch tube Q6 and one end of the resistor R23. The other end of the resistor R23 is connected to the gate of the switch tube Q4. The source of the switch tube Q4 is connected to one end of the first heating tube. The emitter of the switch tube Q5, the collector of the switch tube Q6, and the drain of the switch tube Q4 are connected to the other end of the first heating tube and grounded.

[0068] The IGBT drive circuit includes a transistor amplifier, a push-pull part and an overvoltage protection, and can realize high-frequency drive of the IGBT. The number of IGBT drive circuits 55 corresponds to the number of heating tubes. When multiple heating tubes are provided, multiple IGBT drive circuits are also provided and correspond to the heating tubes one by one. In this embodiment, three heating tubes are provided, and three IGBT drive circuits are provided. Fig. 9As shown, the second IGBT drive circuit includes a switch tube Q7, a switch tube Q8, a switch tube Q9, a switch tube Q10, a resistor R26, a resistor R27, a resistor R29, and a resistor R30. One end of the resistor R30 is connected to the 32nd pin of the main control chip, and the other end of the resistor R30 is connected to the base of the switch tube Q9. The collector of the switch tube Q9 is respectively connected to one end of the resistor R26, one end of the resistor R27, the base of the switch tube Q7, and the base of the switch tube Q10. The other end of the resistor R26, the other end of the resistor R27, and the collector of the switch tube Q7 are connected and then connected to an 18V power supply. The emitter of the switch tube Q7 is respectively connected to the emitter of the switch tube Q10 and one end of the resistor R29. The other end of the resistor R29 is connected to the gate of the switch tube Q8. The source of the switch tube Q8 is connected to one end of the second heating tube. The emitter of the switch tube Q9, the collector of the switch tube Q10, and the drain of the switch tube Q8 are connected and then connected to the other end of the second heating tube and grounded.

[0069] like Fig.10 As shown, the third IGBT driving circuit includes a switch tube Q11, a switch tube Q12, a switch tube Q13, a switch tube Q14, a resistor R34, a resistor R35, a resistor R36, and a resistor R37. One end of the resistor R37 is connected to the thirty-first pin of the main control chip, and the other end of the resistor R37 is connected to the base of the switch tube Q13. The collector of the switch tube Q13 is respectively connected to one end of the resistor R34, one end of the resistor R35, the base of the switch tube Q11, and the base of the switch tube Q14. The other end of resistor R34, the other end of resistor R35, and the collector of switch tube Q11 are connected and then connected to an 18V power supply. The emitter of switch tube Q11 is respectively connected to the emitter of switch tube Q14 and one end of resistor R36. The other end of resistor R36 is connected to the gate of switch tube Q12. The source of switch tube Q12 is connected to one end of the third heating tube. The emitter of switch tube Q13, the collector of switch tube Q14, and the drain of switch tube Q12 are connected and then connected to the other end of the third heating tube and grounded. The models of switch tubes Q3, Q6, Q7, Q10, Q11, and Q14 are all MMBT8550D, and the models of switch tubes Q4, Q8, and Q12 are all FGA25N120AND.

[0070] Place temperature probes at the air inlet of the load box and inside the box. Figure 5The control and drive circuit 50 also includes a temperature sampling circuit 57. Each temperature probe is connected to the main control circuit 51 through the temperature sampling circuit 57, and is used to measure the air inlet temperature and the temperature inside the box. The present invention can perform temperature compensation on the actual working resistance of the heating tube by collecting the temperature inside the load box. The calibrated resistance of the heating tube is R0 at 25°C. According to the temperature coefficient α of the calibrated alloy heating resistor and the collected temperature T inside the box, according to the formula R t = R0(1+α(T-25)) Calculate the actual working resistance R of the heating pipe t , further improving the regulation accuracy of the load box power.

[0071] like Fig.11 As shown, the temperature sampling circuit 57 includes a resistor R18 and a capacitor C21, one end of the resistor R18 is respectively connected to one end of the temperature probe, one end of the capacitor C21, and the 42nd pin of the main control chip, the other end of the resistor R18 is connected to a 5V voltage, and the other end of the capacitor C21 is connected to the other end of the temperature probe and grounded. The present invention places temperature probes at the air inlet position of the rack-type load box and inside the box, and the output ends of the two temperature sampling circuits are respectively connected to the 42nd pin and the 43rd pin of the main control chip. The temperature probe uses an NTC temperature sensing element to collect the temperature of the air inlet and the box, and converts it into a voltage value and sends it to the AD port.

[0072] Continue reading Figure 5 The control and drive circuit also includes an air volume setting and display module and a fan speed control circuit. The air volume setting and display module is connected to the main control circuit 51 for inputting the set air volume value. The fan speed control circuit is connected between the main control circuit and the fan module. The main control circuit inputs a control signal to the fan speed control circuit according to the signal duty cycle to achieve air volume regulation. This can solve the problem in the prior art that the fans are all running at full speed, resulting in an unstable inlet and outlet air temperature difference of the equipment, and cannot simulate the actual operating conditions of the server and other equipment in the computer room.

[0073] The circuits of the power setting and display module and the air volume setting and display module are the same, both of which include an adjustable resistor circuit and a voltage conversion and display circuit. The power setting and display module adjusts the voltage of the input signal through the knob of the adjustable resistor and inputs it to the A / D port in the single-chip microcomputer. The signal undergoes voltage conversion synchronously, converting the voltage value of the input signal into a voltage value equal to the set power value, and is connected to the voltage meter to display the set power value. The air volume setting and display module adjusts the voltage of the input signal through the knob of the adjustable resistor and inputs it to the A / D port in the single-chip microcomputer. The signal undergoes voltage conversion synchronously, converting the voltage value of the input signal into a voltage value equal to the set fan speed value, and is connected to the voltage meter to display the set speed value. Through the adjustable resistor on the panel and the addition of a voltage conversion circuit, the set voltage and the digital display window can be displayed synchronously.

[0074] like Fig.12 As shown, the voltage conversion and display circuit includes a resistor R28, a resistor R32, a resistor R33, and a capacitor C25. One end of the resistor R28 is connected to an 18V voltage, and the other end of the resistor R28 is respectively connected to one end of the adjustable resistor, one end of the resistor R32, and a digital display interface. The other end of the adjustable resistor is grounded. The other end of the resistor R32 is respectively connected to one end of the resistor R33, one end of the capacitor C25, and the 44th pin of the main control chip. The other end of the resistor R33 is connected to the other end of the capacitor C25 and grounded. Continue to refer to Figure 4 The fan module 40 includes a switching power supply module and at least one DC fan. The model of the switching power supply module is LM150-20B24. The input end of the switching power supply module is connected to the output end of the rectifier circuit 10, which is used to convert the output voltage of the rectifier circuit into different voltage levels to supply power to the DC fan, control and drive circuits respectively. The DC fan is connected to the main control circuit through the fan speed control circuit. Fig.13 As shown, the fan speed control circuit includes a resistor R1, one end of the resistor R1 is connected to a 5V voltage, and the other end is connected to a DC fan. The twenty-third pin of the single-chip microcomputer outputs a speed control signal to the DC fan.

[0075] Continue reading Figure 5 The control and driving circuit also includes a power switching and DC / DC conversion circuit, a signal voltage conversion circuit, a 2.5V reference voltage circuit, a burning and communication circuit.

[0076] like Fig.14As shown, the power switching and DC / DC conversion circuit includes a chip U1, a chip U2, a MOS tube M1, a MOS tube M2, a MOS tube M3, a MOS tube M4, a diode D1, a diode D2, capacitors C1-C7, capacitors C9-C15, a capacitor C17, resistors R4-R9, resistors R11-R14, and a resistor R16. One end of the resistor R8 is respectively connected to the anode of the diode D1 and the anode of the diode D2 and connected to the positive electrode of the 24V input power supply. The other end of the resistor R8 is respectively connected to one end of the resistor R12 and the gate of the MOS tube M3. The other end of the resistor R12 is respectively connected to the source of the MOS tube M3, one end of the resistor R11, and the MOS The source of MOS tube M4 is connected to ground, the drain of MOS tube M3 is connected to one end of resistor R4, the other end of resistor R11, and the gate of MOS tube M4 respectively, the drain of MOS tube M4 is connected to one end of resistor R9, the other end of resistor R4 is connected to the source of MOS tube M1 and connected to the positive electrode of another 24V input power supply, the other end of resistor R9 is connected to the gate of MOS tube M1, one end of resistor R5, and the gate of MOS tube M2 respectively, the other end of resistor R5 is connected to the drain of MOS tube M1 and the drain of MOS tube M2, the source of MOS tube M2 is connected to the cathode of diode D1, the cathode of diode D2, one end of resistor R6, and one end of capacitor C1 respectively , one end of capacitor C2, one end of capacitor C3, and the first pin of chip U2. The other end of resistor R6 is connected in series with resistor R14 and is respectively connected to one end of capacitor C13, one end of capacitor C14, one end of capacitor C15, and the third pin of chip U1. The other end of capacitor C1, the other end of capacitor C2, the other end of capacitor C3, one end of capacitor C4, one end of capacitor C5, one end of capacitor C6, and one end of capacitor C7 are connected to one end of resistor R7 and are then grounded. The other end of resistor R7 is connected to the third pin of chip U2, one end of resistor R13, the other end of resistor R13, the other end of capacitor C4, the other end of capacitor C5, the other end of capacitor C6, and capacitor The other end of C7 and the second pin of chip U2 are connected and then connected to 18V voltage, the other end of capacitor C13, the other end of capacitor C14, the other end of capacitor C15, one end of capacitor C17, and the first pin of chip U1 are connected and then grounded, the second pin of chip U1 is respectively connected to one end of capacitor C9, one end of capacitor C10, one end of capacitor C11, one end of capacitor C12, and the thirty-eighth pin of the main control chip and connected to 5V voltage, the other end of capacitor C9, the other end of capacitor C10, and the other end of capacitor C11 are connected and then connected to one end of resistor R16 and grounded, and the other end of resistor R16 is respectively connected to the other end of capacitor C12 and the fourth pin of the main control chip.The model of chip U1 is LY-7250M, the model of chip U2 is ZLDO1117K50TC, the models of MOS tube M1 and MOS tube M2 are both PV507BA, the models of MOS tube M3 and MOS tube M4 are both L2N7002LTIG, and the models of diode D1 and diode D2 are both SS54BF.

[0077] The power switching and DC / DC conversion circuit supports dual 24V power inputs and can automatically select one of the power supplies as the system's working power supply to improve system reliability. It includes 24 / 18V and 24 / 5V voltage conversion circuits to provide working power for different modules. The power switching and DC / DC conversion circuit is also used to provide working power to the fan and relay control circuits. The cathode of the diode D1 is connected in series with the fuse and is connected to the power input of the fan and the power input of the relay control circuit respectively. The function of the series fuse is to protect the fan.

[0078] like Fig.15 As shown, the signal voltage conversion circuit includes an AC / DC mode selection switch and a resistor R21, one end of the resistor R21 is connected to a 5V voltage, the other end of the resistor R21 is connected to a first pin of the AC / DC mode selection switch, the second pin of the AC / DC mode selection switch is connected to a 20th pin of the main control chip, and the third pin of the AC / DC mode selection switch is grounded.

[0079] like Fig.16 As shown, the 2.5V reference voltage circuit includes a linear voltage regulator chip T1, a resistor R22, a capacitor C22, and a capacitor C23. One end of the resistor R22 is connected to a 5V voltage, and the other end of the resistor R22 is respectively connected to one end of the capacitor C22, one end of the capacitor C23, the first pin of the linear voltage regulator chip T1, the second pin of the linear voltage regulator chip T1, and the third pin of the main control chip. The other end of the capacitor C22, the other end of the capacitor C23, and the third pin of the linear voltage regulator chip T1 are connected and then grounded. The model of the linear voltage regulator chip T1 is SMAZ5V1-13-F. The 2.5V reference voltage circuit provides a 2.5V reference voltage, which is used as a reference for the voltage value when calculating the peak voltage inside the program to avoid the deviation of the calculation result caused by the power supply voltage fluctuation.

[0080] like Fig.17As shown, the input end of the burning and communication circuit is connected to the output end of the main control circuit, and the output end of the burning and communication circuit is respectively connected to the burning port and the communication port. The burning and communication circuit includes chip J12, chip P2, and chip J. The model of chip J12 is CHUSB-AF900102. The second pin and the third pin of chip J12 are respectively connected to the 40th pin and the 41st pin of the main control chip. The second pin and the sixth pin of chip J are respectively connected to the seventh pin and the fifth pin of the main control chip. The second pin and the third pin of chip P2 are respectively connected to the seventh pin and the fifth pin of the main control chip.

[0081] like Fig.18 and Fig.19 As shown, the control and drive circuit 50 also includes an indication circuit and an alarm circuit. The input ends of the indication circuit and the alarm circuit are respectively connected to the main control circuit. The indication circuit includes a resistor R3, a resistor R10, an indicator light D3, and a switch tube Q1. One end of the resistor R10 is connected to the 18th pin of the main control chip, and the other end of the resistor R10 is connected to the base of the switch tube Q1. The collector of the switch tube Q1 is connected to the cathode of the indicator light D3. The anode of the indicator light D3 is connected in series with the resistor R3 and then connected to a 5V voltage. The emitter of the switch tube Q1 is grounded. The alarm circuit includes a resistor R15, a resistor R17, an alarm light D4, and a switch tube Q2. One end of the resistor R17 is connected to the 19th pin of the main control chip, and the other end of the resistor R17 is connected to the base of the switch tube Q2. The collector of the switch tube Q2 is connected to the cathode of the indicator light D4. The anode of the alarm light D4 is connected in series with the resistor R15 and then connected to a 5V voltage. The emitter of the switch tube Q2 is grounded. The models of the switch tubes Q1 and Q2 are both LMBT3904LT1G. By setting the indication circuit and the alarm circuit, the system operation status can be conveniently indicated. When the system power supply is normal and working normally, the indication circuit works (the green light is on). When the system voltage is too low or the power deviation exceeds the tolerance, the alarm circuit works (the red light is on).

[0082] Working principle: Fig. 20 As shown, each module and device is reasonably arranged in the box of the load box to obtain a rack-type load box. The size of the entire box can be: 430mm (width) × 177.8mm (height) × 550mm (depth), which meets the requirements of 19-inch rack installation. The box is a sheet metal box, painted black. By arranging multiple rack-type load boxes of the present invention in the same rack and setting the power and air volume of each rack-type load box, the power consumption of the entire rack can be increased.

[0083] The constant power rack-mounted load box of the present invention can be used for testing and verification of data rooms, aging testing of UPS power supplies, full load testing of distribution cabinets, etc. Here, the working principle of the constant power rack-mounted load box of the present invention is introduced by taking the testing and verification of data rooms as an example. Before testing, the load box is installed in a cabinet in the data room, and then the power cord matching the load box is inserted into the PDU socket of the cabinet to connect the load box to the power supply system of the data room.

[0084] During the test, according to the prepared test index requirements, the power value and the air volume value are set, and the load box is started. The set power value and the set air volume value are respectively input into the main control chip of the main control circuit. The main control chip of the present invention adopts a single-chip microcomputer. The single-chip microcomputer collects the voltage signal and the current signal of the external input power supply according to the set power value and the set air volume value, and calculates the rated power value of the load box. The set power value is divided by the rated power value to obtain the signal duty cycle. The single-chip microcomputer outputs a PWM wave according to the value of the signal duty cycle, controls the conduction or shutdown of the transistor through the IGBT drive circuit, adjusts the proportion of the load input time to the total time, and realizes that the output power of the load box is equal to the set power value, thereby realizing dynamic adjustment of the actual output power of the load box and keeping it consistent with the set power value. The load box of the present invention has the characteristics of consuming constant electrical energy and converting it all into heat.

[0085] According to the selection of the mode switch, the microcontroller identifies whether the input signal is DC or AC. When the input signal is DC, the mode switch selects DC. After the microcontroller recognizes the signal, the system rated power is equal to (voltage value * voltage value) / (loop resistance). When the system input is AC, the mode switch selects AC. After the microcontroller recognizes the signal, the system rated power is equal to (voltage value * voltage value) / (loop resistance * 2). The loop resistance is equal to the total resistance of multiple heating tubes connected in parallel.

[0086] The constant power rack-mounted load box uses sampling and control technology to achieve automatic adjustment of the load box power to the set power according to changes in the external input power supply, realizing closed-loop control of the power, and by adjusting the fan speed, the air intake of the equipment is equal to the set air volume value, thereby realizing automatic adjustment of the load box power and air volume.

[0087] The present invention is used for data room testing and verification. As an electrical device, it is installed in a cabinet in the room and connected to the power supply system through cables. During the equipment and line testing process, it can effectively overcome the influence of the change in the voltage at the power source end, maintain a constant output power, and ensure the smooth progress of the test. In addition, the air volume data of the later server can be accurately matched by adjusting the air volume, thereby realizing accurate simulation of the test scene and ensuring the accuracy and effectiveness of the test data.

[0088] Example 2

[0089] This embodiment provides a constant power regulation method for the constant power load simulation circuit in Embodiment 1, including: the power setting and display module 54 inputs the set power value into the main control circuit 51, the main control circuit 51 collects the voltage of the external power supply and calculates the rated power value, calculates the signal duty cycle according to the set power value and the rated power value, and outputs a PWM wave to control the on or off of the transistor through the IGBT drive circuit 55, the main control circuit 51 collects the current of the external power supply for fine-tuning the signal duty cycle, and dynamically adjusts the actual output power of the load simulation circuit to keep it consistent with the set power value.

[0090] The specific method in which the main control circuit 51 collects the current of the external power supply for fine-tuning the signal duty cycle is as follows: when the deviation between the rated power value and the set power value exceeds the set threshold, the main control circuit 51 calculates the current power value based on the collected current, and fine-tunes the signal duty cycle based on the magnitude of the current power value and the rated power value. If the current power value is greater than the rated power value, the signal duty cycle is fine-tuned to reduce the signal duty cycle; if the current power value is less than the rated power value, the signal duty cycle is fine-tuned to increase the signal duty cycle until the deviation between the rated power value and the set power value is within the set threshold range.

[0091] The air volume setting and display module is connected to the main control circuit 51 for inputting the set air volume value. The fan speed control circuit is connected between the main control circuit and the fan module. The main control circuit inputs a control signal to the fan speed control circuit according to the signal duty cycle to achieve air volume regulation.

[0092] The constant power regulation method also includes a process of compensating the temperature of the heating tube. The temperature sampling circuit 57 collects the temperature inside the load box. According to the formula R t = R0(1+α(T-25)) Calculate the actual working resistance R of the heating pipe t , where R0 is the calibrated resistance of the heating tube at 25°C, α is the temperature coefficient of the calibrated alloy heating resistor, and T is the collected temperature inside the box. By collecting the temperature inside the load box, the actual working resistance of the heating tube can be temperature compensated, further improving the adjustment accuracy of the load box power.

[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. Constant power load simulation circuit, characterized in that: The analog circuit comprises a rectifier circuit (10), a shunt (20), a power module (30), a fan module (40), and a control and drive circuit (50). The power module (30) comprises at least one heating tube and at least one transistor. The control and drive circuit (50) comprises a main control circuit (51), a voltage signal processing circuit (52), a current signal processing circuit (53), a power setting and display module (54), and at least one IGBT drive circuit (55). The input end of the rectifier circuit (10) is connected to an external power supply. The output negative electrode of the rectifier circuit (10) is connected in series with the shunt (20) and then connected to the emitter of the transistor. The output positive electrode of the rectifier circuit (10) is connected in series with the heating tube and then connected to the collector of the transistor. The base of the transistor is connected to the IGBT drive circuit (55). ) is connected to a main control circuit (51), the output positive electrode of the rectifier circuit (10) is connected to the main control circuit (51) through a voltage signal processing circuit (52), the two ends of the shunt (20) are connected to the main control circuit (51) through a current signal processing circuit (53), the fan module (40) is connected between the rectifier circuit (10) and the main control circuit (50), the power setting and display module (54) is connected to the main control circuit (51) for inputting a set power value, the main control circuit (51) collects the voltage and current of the external power supply and calculates the rated power value, calculates the signal duty cycle according to the set power value and the rated power value, and outputs a PWM wave to control the conduction or shutoff of the transistor through an IGBT drive circuit (55), and dynamically adjusts the actual output power of the load box to keep it consistent with the set power value.

2. The constant power load simulation circuit according to claim 1, characterized in that: The power module (30) further comprises at least one DC contactor and at least one temperature sensing element. The control and drive circuit (50) further comprises a relay control circuit (56). The DC contactor is connected between the output positive electrode of the rectifier circuit (10) and the heating tube. The control port of the DC contactor is connected to the main control circuit (51) via the relay control circuit (56). The temperature sensing element is close to the heating tube and is used to measure the temperature of the heating tube and input the temperature signal into the main control circuit (51) via the relay control circuit (56).

3. The constant power load simulation circuit according to claim 1, characterized in that: The main control circuit (51) comprises a main control chip, a crystal oscillator Y1, a capacitor C6, and a capacitor C20. The main control chip adopts a single-chip microcomputer. The first pin of the single-chip microcomputer is connected to the output end of the voltage signal processing circuit (52). The second pin of the single-chip microcomputer is connected to the output end of the current signal processing circuit (53). The fourteenth pin of the single-chip microcomputer is respectively connected to one end of the crystal oscillator Y1 and one end of the capacitor C20. The fifteenth pin of the single-chip microcomputer is respectively connected to the other end of the crystal oscillator Y1 and one end of the capacitor C8. The other end of the capacitor C8 is connected to the other end of the capacitor C20 and then grounded. The thirty-first pin, the thirty-second pin, and the thirty-third pin of the single-chip microcomputer are respectively connected to the IGBT drive circuit (55). The forty-fourth pin of the single-chip microcomputer is connected to the output end of the power setting and display module (54).

4. The constant power load simulation circuit according to claim 1, characterized in that: The voltage signal processing circuit (52) comprises a rectifier chip D6, a voltage stabilizing diode D7, a capacitor C16, a capacitor C26, a resistor R40, and a resistor R41. The second pin and the third pin of the rectifier chip D6 are respectively connected to two output ends of the rectifier circuit. The first pin of the rectifier chip D6 is respectively connected to the positive plate of the capacitor C16 and one end of the resistor R40. The other end of the resistor R40 is respectively connected to one end of the resistor R41, the cathode of the voltage stabilizing diode D7, one end of the capacitor C26, and the first pin of the main control chip. The fourth pin of the rectifier chip D6 is respectively connected to the negative plate of the capacitor C16, the other end of the resistor R41, the anode of the voltage stabilizing diode D7, the other end of the capacitor C26, and grounded.

5. The constant power load simulation circuit according to claim 1, characterized in that: The number of the multiple IGBT drive circuits (55) is the same as the number of the multiple heating tubes and corresponds to the heating tubes one by one. The IGBT drive circuit (55) comprises a switch tube Q3, a switch tube Q4, a switch tube Q5, a switch tube Q6, a voltage regulator diode D5, a resistor R19, a resistor R20, a resistor R23, and a resistor R24. One end of the resistor R24 ​​is connected to the thirty-third pin of the main control chip, and the other end of the resistor R24 ​​is connected to the base of the switch tube Q5. The collector of the switch tube Q5 is respectively connected to one end of the resistor R19, one end of the resistor R20, and the base of the switch tube Q3. , the base of the switching tube Q6, the other end of the resistor R19, the other end of the resistor R20, and the collector of the switching tube Q3 are connected to the cathode of the voltage-stabilizing diode D5 and connected to an 18V power supply. The anode of the voltage-stabilizing diode D5 is grounded. The emitter of the switching tube Q3 is respectively connected to the emitter of the switching tube Q6 and one end of the resistor R23. The other end of the resistor R23 is connected to the gate of the switching tube Q4. The source of the switching tube Q4 is connected to one end of the first heating tube. The emitter of the switching tube Q5, the collector of the switching tube Q6, and the drain of the switching tube Q4 are connected to the other end of the first heating tube and grounded.

6. The constant power load simulation circuit according to claim 1, characterized in that: The analog circuit also includes a temperature probe, and the control and drive circuit (50) also includes a temperature sampling circuit (57). The temperature sampling circuit (57) includes a resistor R18 and a capacitor C21, one end of the resistor R18 is respectively connected to one end of the temperature probe, one end of the capacitor C21, and the forty-second pin of the main control chip, the other end of the resistor R18 is connected to a 5V voltage, and the other end of the capacitor C21 is connected to the other end of the temperature probe and is grounded.

7. The constant power load simulation circuit according to claim 1, characterized in that: The control and drive circuit also includes an air volume setting and display module and a fan speed regulation circuit. The air volume setting and display module is connected to a main control circuit (51) for inputting a set air volume value. The fan speed regulation circuit is connected between the main control circuit and the fan module. The main control circuit inputs a control signal to the fan speed regulation circuit according to a signal duty cycle to achieve air volume regulation.

8. The constant power load simulation circuit according to claim 7, characterized in that: The power setting and display module and the air volume setting and display module both include an adjustable resistance circuit and a voltage conversion and display circuit. The power setting and display module adjusts the magnitude of the input signal voltage through the knob of the adjustable resistance and inputs it into the A / D port in the main control circuit. The signal undergoes voltage conversion synchronously to convert the voltage value of the input signal into a voltage value equal to the set power value, and is connected to the voltage meter to display the set power value; the air volume setting and display module adjusts the magnitude of the input signal voltage through the knob of the adjustable resistance and inputs it into the A / D port in the main control circuit. The signal undergoes voltage conversion synchronously to convert the voltage value of the input signal into a voltage value equal to the set fan speed value, and is connected to the voltage meter to display the set speed value.

9. A constant power regulation method, applied to the constant power load simulation circuit according to any one of claims 1 to 8, characterized in that: The power setting and display module (54) inputs the set power value into the main control circuit (51); the main control circuit (51) collects the voltage of the external power supply and calculates the rated power value; calculates the signal duty cycle according to the set power value and the rated power value; and outputs a PWM wave to control the on or off of the transistor through the IGBT drive circuit (55); the main control circuit (51) collects the current of the external power supply to fine-tune the signal duty cycle, and dynamically adjusts the actual output power of the load simulation circuit to keep it consistent with the set power value.

10. A rack-mounted load box, comprising the constant power load simulation circuit according to any one of claims 1 to 8, characterized in that: It also includes a box, in which the load simulation circuit is located.

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