A main circuit structure of a high-position energy-taking power supply

Abstract

The present invention relates to a main circuit structure of a high-position energy-taking power supply, which adopts the principle of a single-ended flyback switching power supply. Since the input voltage is very high, the power supply uses multiple switching tubes in series to solve the problem of insufficient voltage withstand of the devices, reducing the cost of purchasing ultra-high voltage devices. At the same time, it cleverly solves the problem of suppressing the voltage spike generated by the leakage inductance of the transformer at the moment when the switch is turned off, and plays a role in equalizing the voltage of the series switching tubes. The power supply of the present invention not only has high working efficiency, but also has simple control and can be controlled by using conventional switching power supply control methods.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and particularly to a main circuit structure of a high-position energy-taking power supply. Background Art

[0002] A high-position energy-taking power supply is a special power supply applied to a VSC-HVDC converter valve. Its input voltage is DC300V to DC4500V, the rated input voltage is DC2800V, the output is DC16V, the power is 18W, and the higher the efficiency, the better; the electrical isolation insulation level between the input and the output is 10kV, and the leakage current is less than 5mA; the input end has a surge suppression ability, and the power supply continues to output normally during a surge.

[0003] The high-position energy-taking power supply has the characteristics of high input voltage, wide voltage range, and high electrical isolation level. The current conventional method in the market is to use multiple resistors in series for voltage division. After each resistor gets a relatively small voltage, a conventional switching power supply is then connected in parallel to the resistor to obtain the output voltage and power, as Figure 1 shown. The high-position energy-taking power supply using this method has extremely low working efficiency, consumes most of the energy on the resistors, has large losses, and cannot be widely used; and due to large losses, the power supply generates serious heat, and the power supply is prone to damage in a high-temperature environment.

[0004] In order to reduce the input-end voltage and not lose too much electric energy, a method of using capacitors in series for voltage division has emerged in the market. The more capacitors are connected in series, the smaller the voltage on each capacitor. After each capacitor gets a relatively small voltage, a conventional switching power supply is then connected in parallel to each capacitor, and finally the output ends of each switching power supply are connected in parallel to output the voltage and power, as Figure 2 shown. The resistors R1 to R3 connected in parallel to the capacitors C1 to C3 in the figure are capacitor voltage-sharing resistors with very large resistance values, and a small amount of electric energy is consumed. The high-position energy-taking power supply using this method has relatively high working efficiency, but the control is complex. It is necessary to adjust the output power of each conventional switching power supply in real time so that the input equivalent impedance of each switching power supply is basically equal. If the impedances are not equal, the one with a larger impedance will get a very high voltage, and the one with a smaller impedance will get a very low voltage. Only when the dynamic equivalent impedances of each switching power supply during operation are equal, the voltages on each capacitor can be balanced and remain basically equal. If the output powers of each switching power supply are not balanced, it will cause the voltages on the capacitors C1 to C3 to be unequal, and even differ greatly. Some capacitors have very high voltages, and some have very low voltages. The capacitors and switching power supplies in the capacitor loop with a high voltage will be damaged due to overvoltage. Moreover, the high-position energy-taking power supply of this method requires many switching power supplies to be connected in parallel, making its cost relatively high and its volume relatively large. Summary of the Invention

[0005] The purpose of the present invention is to design a reliable, high-efficiency, simple-to-control, and low-cost high-position energy-taking power supply.

[0006] To this end, a main circuit structure of a high-voltage energy-taking power supply is provided, including terminal CN1, terminal CN2, switching tube Q1, switching tube Q2, switching tube Q3, switching tube Q4, switching tube Q5, switching tube Q6, transformer T2, diode D11, diode D22, diode D33, diode D44, diode D55, diode D66, as well as resistors R1, R2, R3, R4, R5, R6 with equal resistance values, and capacitors C1, C2, C3, C4, C5, C6 with equal capacitance values;

[0007] The D pole of switching tube Q1 is connected to terminal CN1, the S pole is grounded and connected to the anode of diode D11, and the cathode of diode D11 is connected to terminal CN1 through resistor R1, and capacitor C1 is connected in parallel with resistor R1;

[0008] The D pole of switching tube Q2 is connected to the S pole of switching tube Q1, the S pole of switching tube Q2 is grounded and connected to the anode of diode D22, and the cathode of diode D22 is connected to the end of resistor R1 far from terminal CN1 through resistor R2, and capacitor C2 is connected in parallel with resistor R2;

[0009] The D pole of switching tube Q3 is connected to the S pole of switching tube Q2, the S pole of switching tube Q3 is grounded and connected to the cathode of diode D33 and the upper end of the primary winding of transformer T2, and the anode of diode D33 is grounded;

[0010] The D pole of switching tube Q4 is connected to the lower end of the primary winding of transformer T2 and connected to the anode of diode D44. The cathode of diode D44 is connected to the end of resistor R2 far from terminal CN1 through resistor R3, and capacitor C3 is connected in parallel with resistor R3. The S pole of switching tube Q4 is grounded and connected to the anode of diode D55, and the cathode of diode D55 is connected to the end of resistor R3 far from terminal CN1 through resistor R4, and capacitor C4 is connected in parallel with resistor R4;

[0011] The D pole of switching tube Q5 is connected to the S pole of switching tube Q4, the S pole of switching tube Q5 is grounded and connected to the anode of diode D66, and the cathode of diode D66 is connected to the end of resistor R4 far from terminal CN1 through resistor R5, and capacitor C5 is connected in parallel with resistor R5;

[0012] The D pole of switching tube Q6 is connected to the S pole of switching tube Q5, the S pole of switching tube Q6 is connected to the ground and terminal CN2, and is connected to the end of resistor R5 far from terminal CN1 through resistor R6, and capacitor C6 is connected in parallel with resistor R6;

[0013] The secondary winding of transformer T2 is rectified and filtered to be used as the output of the main circuit structure of the high-voltage energy-taking power supply.

[0014] Further, it also includes a thermistor NTC1, which is connected in series on the circuit between the resistor R1 and the terminal CN1.

[0015] Further, the G poles of the respective switching tubes are controlled by the same control signal V.

[0016] Further, it includes a transformer T1, which has a primary winding and at least six secondary windings. One end of each secondary winding of the transformer T1 is grounded, and the other end is respectively connected to the G pole of each switching tube. One end of the primary winding of the transformer T1 is grounded, and the other end inputs the control signal V.

[0017] Further, it includes a resistor R71, a capacitor C71, and a diode D71. One end of the primary winding of the transformer T1 is connected to the input point of the control signal V after sequentially connecting the capacitor C71 and the resistor R71 in series, and this end is connected to the anode of the diode D71. The cathode of the diode D71 is connected to the contact point between the resistor R71 and the capacitor C71.

[0018] Further, one end of each secondary winding of the transformer T1 is electrically connected to the G pole of each switching tube through a resistor.

[0019] Further, the G pole of each switching tube is bridged to its S pole through a resistor.

[0020] The high-voltage energy-taking power supply of the present invention adopts the principle of a single-ended flyback switching power supply. Since the input voltage is very high, the power supply uses multiple switching tubes connected in series to solve the problem of insufficient device withstand voltage, reducing the cost of purchasing ultra-high-voltage devices. At the same time, it cleverly solves the problem of suppressing the voltage spike generated by the leakage inductance of the transformer at the moment when the switch is turned off, and plays a role in equalizing the voltage of the series-connected switching tubes. This power supply not only has high working efficiency, but also has simple control and can be controlled by using conventional switching power supply control methods. Brief Description of the Drawings

[0021] Figure 1 It is the topological structure diagram of the high-voltage energy-taking power supply with resistor voltage division + conventional switching power supply.

[0022] Figure 2 It is the topological structure diagram of the high-voltage energy-taking power supply with capacitor voltage division + conventional switching power supply.

[0023] Figure 3 It is the main circuit electrical topological structure of the high-voltage energy-taking power supply of the present invention.

[0024] Figure 4 It is the topological structure diagram of a conventional flyback switching power supply.

[0025] Figure 5 It is the switch control and trigger circuit.

[0026] Figure 6Shows the electrical simulation of the high-position energy-taking power supply of the present invention.

[0027] Figure 7 Shows the output voltage waveform of the high-position energy-taking power supply of the present invention.

[0028] Figure 8 Shows the peak voltage waveforms of the switching transistors FET21 - FET23 of the high-position energy-taking power supply of the present invention. Detailed implementation manners

[0029] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0030] As Figure 3As shown in the figure, the main circuit structure of the high-voltage energy-taking power supply in this embodiment mainly includes terminal CN1, terminal CN2, switching transistor Q1, switching transistor Q2, switching transistor Q3, switching transistor Q4, switching transistor Q5, switching transistor Q6, transformer T2, diode D11, diode D22, diode D33, diode D44, diode D55, diode D66, resistors R1, R2, R3, R4, R5, R6 with equal resistance values, and capacitors C1, C2, C3, C4, C5, C6 with equal capacitance values. The D pole of switching transistor Q1 is connected to terminal CN1, the S pole is grounded and connected to the anode of diode D11, the cathode of diode D11 is connected to terminal CN1 through resistor R1, and capacitor C1 is in parallel with resistor R1; the D pole of switching transistor Q2 is connected to the S pole of switching transistor Q1, the S pole of switching transistor Q2 is grounded and connected to the anode of diode D22, the cathode of diode D22 is connected to the end of resistor R1 far from terminal CN1 through resistor R2, and capacitor C2 is in parallel with resistor R2; the D pole of switching transistor Q3 is connected to the S pole of switching transistor Q2, the S pole of switching transistor Q3 is grounded and connected to the cathode of diode D33 and the upper end of the primary winding of transformer T2, and the anode of diode D33 is grounded; the D pole of switching transistor Q4 is connected to the lower end of the primary winding of transformer T2 and connected to the anode of diode D44, the cathode of diode D44 is connected to the end of resistor R2 far from terminal CN1 through resistor R3, capacitor C3 is in parallel with resistor R3, the S pole of switching transistor Q4 is grounded and connected to the anode of diode D55, the cathode of diode D55 is connected to the end of resistor R3 far from terminal CN1 through resistor R4, and capacitor C4 is in parallel with resistor R4; the D pole of switching transistor Q5 is connected to the S pole of switching transistor Q4, the S pole of switching transistor Q5 is grounded and connected to the anode of diode D66, the cathode of diode D66 is connected to the end of resistor R4 far from terminal CN1 through resistor R5, and capacitor C5 is in parallel with resistor R5; the D pole of switching transistor Q6 is connected to the S pole of switching transistor Q5, the S pole of switching transistor Q6 is connected to the ground and terminal CN2, and is connected to the end of resistor R5 far from terminal CN1 through resistor R6, and capacitor C6 is in parallel with resistor R6; the secondary winding of transformer T2 is used as the output of the main circuit structure of the high-voltage energy-taking power supply after rectification and filtering; the thermistor NTC1 is connected in series on the line between resistor R1 and terminal CN1.

[0031] During operation, the incoming high-voltage power supply is input from terminals CN1 and CN2. Terminal CN1 is connected to the positive power supply, and CN2 is connected to the negative power supply. After passing through the NTC1 thermistor, the high-voltage power supply is applied to capacitors C1 to C6. When switching transistors Q1 to Q6 are turned on, the high-voltage power supply is applied to the primary winding (6 - 4) of transformer T2, and the current flows out from pin 4 of transformer T2. Based on the principle of flyback switching power supply, diodes D1 and D2 in the secondary winding of transformer T2 are in the cut-off state. At this time, the primary winding (6 - 4) of the transformer is in the inductive energy storage state. When switching transistors Q1 to Q6 are turned off, the secondary winding of transformer T2 outputs voltage and power to the load through diodes D1 and D2. While the secondary side of the transformer outputs power, due to the turn-off of the switching transistors, the leakage inductance energy of the transformer primary side is discharged to the surge absorption circuit R and C through diodes.

[0032] In the above, the surge absorption circuit is composed of a thermistor NTC1, capacitors, and resistors. The main function of the thermistor NTC1 is to reduce the current impact on the power supply because the capacitor is equivalent to a short circuit when it is powered on. Here, the capacitor plays the role of filtering and storing energy. Since the withstand voltage of a conventional single capacitor is relatively small, multiple capacitors are connected in series to reduce the withstand voltage of a single capacitor. To make the withstand voltage of each capacitor balanced, resistors with large and equal resistance values are connected in parallel across the capacitors, mainly playing the role of voltage equalization for capacitors C1 to C6 and providing an energy discharge channel when power is off. At the same time, the method of using a thermistor + capacitor + resistor also plays a role in surge suppression. When a voltage surge appears at the input end, it can absorb and suppress voltage spikes in a timely manner, preventing the impact on and damage to the power supply backend circuit. For surge absorption, the usual method is to add a varistor, and the varistor is connected in parallel at the input end of the power supply. When the voltage exceeds the voltage of the varistor, the excess voltage is absorbed and consumed by the varistor, but the number of times (life) of the varistor absorbing energy is limited. To improve the system reliability, this power supply uses the method of thermistor + capacitor + resistor to play a role in surge suppression.

[0033] At the moment when the flyback power supply switches off, due to the leakage inductance of the transformer and the reflected voltage on the secondary side of the transformer, a voltage higher than the input power supply will be formed across the switching transistor. Therefore, the voltage borne by the switching transistor is much higher than the input power supply voltage. The switching part of this high-voltage energy extraction power supply uses six 1700V switching transistors in series, with three in series at the upper end of the primary winding of the transformer and three in series at the lower end of the winding. To ensure overvoltage protection for a single switching transistor, a diode clamping circuit is set at the upper end of the switching transistor. The diode is connected to the surge absorption capacitor as Figure 3 shown. When the voltage across the switch exceeds the voltage across the capacitor, the diode conducts to clamp the voltage, protecting the switching transistor and also playing a role in discharging the leakage inductance energy of the transformer. Figure 3 In, this connection method of diode D with R and C is equivalent to six levels connected in series, playing both the role of clamping absorption and surge suppression.

[0034] The principle of the current conventional flyback switching power supply is as Figure 4 shown. The switching transistor is VT1 and there is only one. When VT1 is turned off, it needs to bear a voltage much higher than the power supply voltage Ui at most. Therefore, when the input voltage is DC300V (DC311V after rectifying AC220V), the switching transistor needs to be at least 600V, and generally 650V is selected, and RCD and other clamping and energy absorption circuits need to be added to prevent the voltage from exceeding the maximum withstand voltage of the switching transistor. If the input voltage Ui is DC4500V, a switching transistor above 9000V needs to be selected according to the above rules. There is no such high-voltage switching transistor in the market. Even if there is, the price will be very expensive. The highest voltage of the current conventional switching transistor is only DC1700V.

[0035] In this embodiment, the upper and lower switching mode is adopted on the primary side of the transformer to reduce the voltage of the switching transistor. Specifically, the diode D33 is clamped at pin 6 of the transformer T2. When the upper and lower switching transistors are turned off simultaneously, the current in the primary side coil of the transformer continues to flow from pin 6 to pin 4, but at this time the current passes through the diode D33. Since the voltage drop of the diode itself is below 1V, the voltage of pin 6 of the transformer relative to the ground PGND is only -1V at this time, which is equivalent to being clamped to 0V. The voltage at pin 4 of the transformer is only the reflected voltage of the secondary side of the transformer + the leakage inductance voltage of the transformer, and there is no input voltage Ui of the power grid. At this time, the Ui voltage is applied to the upper bridge arm. The lower bridge arm only bears the reflected voltage of the secondary side + the leakage inductance voltage of the transformer. Therefore, if the input voltage is DC4500V, it is not necessary to select a switching transistor above 9000V. Only a 4500V switching transistor is needed and it is divided into an upper bridge arm and a lower bridge arm. The purpose of dividing into upper and lower bridge arms is to reduce the voltage of the switch. Although the voltage of the switching transistor is reduced by half here, there is no 4500V switching transistor available in the market for purchase. Even if there is, the price is very expensive. Therefore, in this embodiment, the purpose of using 3 1700V switching transistors in series for voltage division in each of the upper and lower bridge arms is adopted.

[0036] The ingenious design of this embodiment lies in that by adopting the upper and lower bridge arms and the clamping method of the diode on the primary side of the transformer, the voltage required by the switching transistor is reduced by half, and multiple switching transistors are connected in series, making the devices used in this high-voltage energy extraction power supply conventional and reducing the cost. Moreover, the surge absorption circuit does not adopt conventional vulnerable (with limited lifespan) devices such as varistors and lightning protection tubes, but adopts the method of NTC + capacitor to absorb surges. In order to also use conventional capacitor devices for the capacitor, the method of series voltage division + voltage equalizing resistors is adopted. After that, the surge absorption circuit (NTC + multiple capacitors in series + multiple resistors) is also ingeniously used, and a diode is added between the switching transistor and the capacitor, which has both a clamping and absorption effect on each switching transistor and also plays a role in surge suppression.

[0037] In this embodiment, the G poles of each switching transistor are controlled by the same control signal V. As Figure 5 shown, the switching control and triggering circuit consists of the control signal V, resistor R71, capacitor C71, diode D71, and transformer T1. Transformer T1 has a primary winding and at least six secondary windings. One end of each secondary winding of transformer T1 is grounded, and the other end is respectively connected to the G pole of each switching transistor. One end of the primary winding of transformer T1 is grounded, and the other end is sequentially connected in series with capacitor C71 and resistor R71 and then connected to the input point of control signal V. This end is connected to the anode of diode D71, and the cathode of diode D71 is connected to the contact point between resistor R71 and capacitor C71. When there is a high-level signal in the primary side of the transformer, drive signals are simultaneously output at the six secondary sides, causing each switching transistor Q1 - Q6 to conduct simultaneously; when the primary side of transformer T1 is a low-level signal, low levels are simultaneously output at the six secondary sides, and switching transistors Q1 - Q6 are simultaneously turned off. In the above, transformer T1 is used to achieve isolation and reduce interference. Capacitor C71, resistor R71, and diode D71 play a role in discharging the energy of the leakage inductance of the transformer.

[0038] Furthermore, one end of each secondary winding of transformer T1 is electrically connected to the G pole of each switching transistor through a resistor to achieve the purpose of protecting the G pole. On this basis, a resistor is connected across the G pole and S pole of each switching transistor to provide a static bias for the G pole input.

[0039] As Figure 6 shown is the electrical simulation waveform of this high-voltage energy-taking power supply. In the figure, Lm is the excitation inductance of the transformer, and L1 is the leakage inductance of the transformer. The leakage inductance is taken as 10uH during simulation.

[0040] The input voltage is DC4500V, and two 16V power supplies are output. The voltage waveforms at startup and in the steady state of the output voltage when one path is loaded with 14.2Ω and the other path is loaded with 320Ω are as Figure 7 shown.

[0041] Taking the leakage inductance of the transformer as 10uH for simulation, the peak voltage waveforms of the voltages on switching transistors FET21 - FET23 are as Figure 8 shown.

[0042] Advantages of this embodiment:

[0043] 1. The control is simple. The control circuit and control method are no different from those of a conventional power supply. In a conventional power supply, a PWM signal of one path directly drives a switching transistor (one), while in the present invention, it directly drives the primary winding of transformer T1 (the switching transistors are simultaneously driven by multiple secondary sides of the transformer), without adding control signals and changing the control form.

[0044] 2. High efficiency. This high-voltage energy extraction power supply uses multiple conventional devices in series to solve the problems of insufficient device withstand voltage or difficult purchase. The power supply efficiency is the same as that of a multi-switch power supply module with capacitors in series for voltage division and in parallel, and both are relatively high.

[0045] 3. Low cost. Since it uses conventional devices in series to form an inverter high-voltage switch instead of the method of capacitors in series and multi-switch power supply modules in parallel, and the control method is the control method of a conventional switch power supply, the cost is relatively low.

[0046] 4. High reliability. After the switching tubes of this high-voltage energy extraction power supply are connected in series, they are then connected to the surge absorption circuit (6 capacitors + 6 resistors) of the power supply itself through diodes, which not only plays a role in equalizing the voltage of the series switching tubes but also discharges the energy of the leakage inductance of the transformer. It not only has a low cost but also improves the stability of the series connection of the switching tubes.

[0047] The above specific embodiments are only several preferred embodiments of the present invention. Based on the technical solution of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A main circuit structure of a high - level energy - taking power supply, characterized in that: It includes terminal CN1, terminal CN2, switching tube Q1, switching tube Q2, switching tube Q3, switching tube Q4, switching tube Q5, switching tube Q6, transformer T2, diode D11, diode D22, diode D33, diode D44, diode D55, diode D66, as well as resistors R1, R2, R3, R4, R5, R6 with equal resistance values, and capacitors C1, C2, C3, C4, C5, C6 with equal capacitance values; The D - pole of switching tube Q1 is connected to terminal CN1, the S - pole is grounded and connected to the anode of diode D11, the cathode of diode D11 is connected to terminal CN1 through resistor R1, and capacitor C1 is in parallel with resistor R1; The D - pole of switching tube Q2 is connected to the S - pole of switching tube Q1, the S - pole of switching tube Q2 is grounded and connected to the anode of diode D22, the cathode of diode D22 is connected to the end of resistor R1 far from terminal CN1 through resistor R2, and capacitor C2 is in parallel with resistor R2; The D - pole of switching tube Q3 is connected to the S - pole of switching tube Q2, the S - pole of switching tube Q3 is grounded and connected to the cathode of diode D33 and the upper end of the primary winding of transformer T2, and the anode of diode D33 is grounded; The D - pole of switching tube Q4 is connected to the lower end of the primary winding of transformer T2 and connected to the anode of diode D44, the cathode of diode D44 is connected to the end of resistor R2 far from terminal CN1 through resistor R3, capacitor C3 is in parallel with resistor R3, the S - pole of switching tube Q4 is grounded and connected to the anode of diode D55, the cathode of diode D55 is connected to the end of resistor R3 far from terminal CN1 through resistor R4, and capacitor C4 is in parallel with resistor R4; The D - pole of switching tube Q5 is connected to the S - pole of switching tube Q4, the S - pole of switching tube Q5 is grounded and connected to the anode of diode D66, the cathode of diode D66 is connected to the end of resistor R4 far from terminal CN1 through resistor R5, and capacitor C5 is in parallel with resistor R5; The D - pole of switching tube Q6 is connected to the S - pole of switching tube Q5, the S - pole of switching tube Q6 is connected to ground and terminal CN2, and is connected to the end of resistor R5 far from terminal CN1 through resistor R6, and capacitor C6 is in parallel with resistor R6; The secondary winding of transformer T2 is used as the output of the main circuit structure of the high - level energy - taking power supply after rectification and filtering.

2. The main circuit structure of a high-position energy-taking power supply according to claim 1, characterized in that: It also includes a thermistor NTC1, and the thermistor NTC1 is connected in series on the line between resistor R1 and terminal CN1.

3. The main circuit structure of a high-position energy-taking power supply according to claim 1, wherein: The G - poles of each switching tube are controlled by the same control signal V.

4. The main circuit structure of a high-position energy-taking power supply according to claim 3, characterized in that: It includes transformer T1, transformer T1 has a primary winding and at least six secondary windings, one end of each secondary winding of transformer T1 is grounded, and the other end is respectively connected to the G - poles of each switching tube, one end of the primary winding of transformer T1 is grounded, and the other end inputs the control signal V.

5. A main circuit structure of a high-position energy-taking power supply according to claim 4, characterized in that: It includes a resistor R71, a capacitor C71, and a diode D71. One end of the primary winding of a transformer T1 is connected to the input point of a control signal V after sequentially connecting the capacitor C71 and the resistor R71 in series, and this end is connected to the anode of the diode D71. The cathode of the diode D71 is connected to the junction point between the resistor R71 and the capacitor C71.

6. The main circuit structure of a high-position energy-taking power supply according to claim 4, characterized in that: One end of each secondary winding of the transformer T1 is electrically connected to the G pole of each switching tube through a resistor.

7. A main circuit structure of a high-position energy-taking power supply according to claim 6, characterized in that: The G pole of each switching tube is bridged to its S pole through a resistor.

Images