High-voltage direct-current power supply based on constant-current discharge

Abstract

The high-voltage direct-current power supply comprises a power supply input end, an inverter circuit, an LLC resonance circuit, a voltage doubling rectifying circuit and a power supply output end which are connected in sequence, and the two ends of the power supply output end are in bridge connection with a high-voltage constant-current discharge circuit; the high-voltage constant-current discharge circuit comprises a dummy load circuit, a constant-current source circuit and a control switch K1; the dummy load circuit comprises N load resistors with the same specification and a voltage-regulator tube, after the load resistors are connected in series, one end is connected with the positive output end of the power supply, the other end is used as a ground-off end, the ground-off end is connected with the cathode of the voltage-regulator tube, and the anode of the voltage-regulator tube is connected with the negative output end of the power supply and is used as ground; the constant current source circuit comprises N + 1 discharge resistors and N triodes which are the same in specification, all the discharge resistors are connected in series and then are in bridge connection with the two ends of the power output end, one triode is connected between every two discharge resistors in series, and base electrodes of all the triodes are correspondingly connected to a contact between every two adjacent load resistors and a contact between the load resistor and the voltage-regulator tube; and the control switch K1 is connected in parallel with the voltage-regulator tube.

Description

Technical Field

[0001] The invention belongs to the field of power electronics, and in particular relates to a high-voltage direct current power supply based on constant current discharge and a control method thereof. Background Art

[0002] In the case of DC high voltage output, such as hash neutron source power supply, laser power supply, high voltage ozone power supply, demisting power supply, etc., the output voltage is usually several thousand volts, tens of kilovolts, or even hundreds of kilovolts. Although this type of power supply has low power, it is required to quickly cut off the power in the event of a system failure. In order to achieve the fast power-off function at the high voltage output end of this type of power supply, in addition to emergency shutdown of the inverter bridge, the control center must also quickly discharge the electricity on the high voltage end capacitor. In this regard, the usual practice is to add a series circuit of a resistor and a switch at the high voltage output end, such as Figure 1 The principle is: when discharge is required, the control center controls K1 in the discharge circuit to be closed (conducted), so that the voltage at the high-voltage output end is added to the resistors R1~Rn, so that the output end energy is quickly consumed on the resistors. As the energy is consumed, the output end voltage will also quickly drop to 0V.

[0003] from Figure 1 It can be seen that the discharge switch K1 must meet three indicators: 1) the voltage level must be higher than the voltage at the output end; 2) the switch can be controlled; 3) it must be closed quickly. From these three indicators, it can be seen that mechanical switches are not suitable here, and only solid-state switches can meet the requirements. However, it is difficult to find single solid-state switches on the market with a voltage exceeding 4.5kV, let alone exceeding tens of kilovolts or even hundreds of kilovolts. Even if such a solid-state switch is customized, the price cost and large size are unacceptable.

[0004] In addition, when using the resistor and switch in series for discharge, a large margin of power level should be reserved for the resistor and switch, because when the discharge is first pulled in, the voltage applied to the resistor is the highest, and the current flowing through the series circuit is also the largest. After the voltage gradually decreases, the power also gradually decreases. The discharge power gradually decreases over time.

[0005] Since the high voltage power supply uses a voltage doubling rectifier circuit to boost the voltage, which has unidirectional conductivity, the energy cannot return to the low voltage end (input end) through the boost circuit. Therefore, the requirement for fast discharge of this type of power supply can only be solved directly at the high voltage end. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention proposes a controllable constant current discharge method constructed by using conventional switch devices. When discharge is required, the switch is controlled to be disconnected, and when discharge is not required, the switch is controlled to be closed.

[0007] The purpose of the present invention is to construct a controllable constant current discharge with conventional switching devices, reduce cost and volume, and facilitate market promotion.

[0008] To this end, a high-voltage direct current power supply based on constant current discharge is provided, wherein the main circuit of the power supply comprises a power supply input terminal, an inverter circuit, an LLC resonant circuit, a voltage doubling rectifier circuit, and a power supply output terminal connected in sequence, and a high-voltage constant current discharge circuit is connected across both ends of the power supply output terminal; the high-voltage constant current discharge circuit at least comprises a dummy load circuit, a constant current source circuit, and a control switch K1; the dummy load circuit comprises N load resistors of the same specification and a voltage regulator tube, wherein one end of each load resistor is connected in series to the positive output end of the power supply, and the other end is used as a grounded end, the grounded end is connected to the cathode of the voltage regulator tube, and the anode of the voltage regulator tube is connected to the power supply The negative output terminal is used as the ground, and N is a positive integer; the constant current source circuit includes N+1 discharge resistors and N transistors with the same specifications, each discharge resistor is connected in series and connected across the two ends of the power supply output terminal, and one transistor is connected in series between every two discharge resistors, wherein the base of the first transistor is connected to the connection point between the first load resistor and the second load resistor, the base of the second transistor is connected to the connection point between the second load resistor and the third load resistor, and so on, and the base of the last transistor is connected to the connection point between the last load resistor and the voltage regulator tube; the control switch K1 is connected in parallel with the voltage regulator tube.

[0009] The control switch K1 is a photodiode or a phototransistor.

[0010] The photodiode or transistor used as a control switch is controlled via an optical fiber.

[0011] The control switch K1 is a transistor controlled by taking power from the high voltage output terminal.

[0012] Among them, the resonant inductor Lr1 in the LLC resonant circuit is made of ferrite material, and the winding wire is a multi-strand input copper wire. The resonant capacitor in the LLC resonant circuit is a CBB capacitor.

[0013] Among them, the transformer in the LLC resonant circuit is made of high-frequency ferrite material, the primary-secondary turns ratio is 1:10, and the primary-secondary winding is wound in layers with multiple strands of copper wire.

[0014] The voltage doubler rectifier circuit is connected to the power output terminal via a filter circuit formed by multiple capacitors connected in series.

[0015] Advantages of the present invention:

[0016] 1. Constant current discharge reduces the power capacity level of the discharge resistor and transistor switch.

[0017] 2. Sampling conventional switching devices effectively reduces costs and volume.

[0018] 3. The dummy load circuit in the original circuit is cleverly used to provide a reference voltage to the switching transistor, thereby achieving constant current discharge and further reducing the cost and volume of the overall power supply.

[0019] 4. The control of the discharge switch becomes simple and easy to operate. The voltage level only requires the selection of switches such as transistors of tens of volts.

[0020] 5. Constant current discharge not only improves the discharge speed, but also does not require too much discharge resistance and switch power margin. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A topological diagram of a conventional fast-discharging high-voltage power supply is shown;

[0022] Figure 2 The topology diagram of the high-voltage power supply for rapid discharge of the present invention is shown;

[0023] Figure 3 Shows a high voltage constant current discharge circuit diagram;

[0024] Figure 4 The power supply system block diagram is shown;

[0025] Figure 5 The figure shows a high voltage constant current discharge circuit diagram controlled by a photosensitive tube. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0027] The power supply main circuit of the present invention is composed of a power supply input terminal, an inverter circuit, an LLC resonant circuit, a voltage doubler rectifier circuit, a filter circuit, a dummy load and a discharge circuit and a power supply output, etc. Figure 2 As shown. The function of the dummy load in the power supply is to overcome the unstable output when no load or light load. The present invention utilizes the dummy load circuit in the original circuit to construct a controllable constant current discharge circuit composed of conventional switches.

[0028] When the high-voltage power supply is working normally, switch K1 is closed, the discharge circuit does not discharge, the current in the discharge circuit is 0A, and the voltage Uce of each switch tube TR1~TRn is equal, and they are connected in series to share the entire output voltage. When a system failure occurs, the control center controls the inverter unit to shut down and controls switch K1 to disconnect. At this time, the energy at the high-voltage output end is discharged through the discharge circuit (resistors R0~Rn, TR1~TRn), and the voltage Uce of all switch tubes is equal during the entire discharge process, and the current is constant. In order to clearly explain the principles of constant current discharge and switch voltage balancing, the dummy load and discharge circuit are separated, and only 3 switch tubes are placed for explanation. Figure 3 shown.

[0029] The high-voltage constant-current discharge circuit is composed of a dummy load circuit (Rd1, Rd2, Rd3, Z1, resistors of the same specification), a constant current source circuit (R1, TR1, R2, TR2, R3, TR3, Ro, resistors and transistors of the same specification), and a control switch K1. The dummy load circuit includes N load resistors Rd1, Rd2, Rd3 of the same specification and a voltage regulator Z1. After each load resistor is connected in series, one end is connected to the positive output end of the power supply, and the other end is used as the grounding end. The grounding end is connected to the cathode of the voltage regulator, and the anode of the voltage regulator is connected to the negative output end of the power supply as the ground. N is a positive integer. The voltage of the voltage regulator Z1 is not high, and it is taken below 20V, which is convenient for forming a constant current source. The constant current source circuit is composed of N+1 discharge resistors and N transistors of the same specification. Each discharge resistor is connected in series and connected across the two ends of the power supply output terminal. A transistor is connected in series between every two discharge resistors, wherein the base of the first transistor is connected to the connection point between the first load resistor and the second load resistor, the base of the second transistor is connected to the connection point between the second load resistor and the third load resistor, and so on. The base of the last transistor is connected to the connection point between the last load resistor and the voltage regulator tube. As shown in the figure, the base b of the transistor TR1 is connected to the tp1 point in the dummy load circuit, the base b of TR2 is connected to the tp3 point in the dummy load circuit, and the base b of TR3 is connected to the tp5 point in the dummy load circuit. The control switch K1 is connected between tp5 and tp7 and is connected in parallel with the voltage regulator tube Z1.

[0030] The dummy load circuit is a voltage regulator connected in series with the original circuit. Since the voltage of the voltage regulator is very small (below 20V), the load power is basically unchanged compared to the original dummy load circuit. If the dummy load power is really required to be unchanged, the resistance value can be recalculated. The calculation method is as follows: Assume that the output voltage of the high-voltage end of the original power supply is DC4500V, the resistance Rd1=Rd2=Rd3=2MΩ, and the voltage regulator value of the voltage regulator is DC18V, then the original dummy load current I 原 =4500V / 6MΩ=0.75mA. Now, in order to keep the current unchanged after adding the voltage regulator, the calculated resistance Rd1=Rd2=Rd3=(4500V-18V) / (3*0.00075A)=1.992MΩ. It can be seen that after adding the voltage regulator, the size of the dummy load is basically unchanged, especially the higher the output voltage, the more negligible it is.

[0031] from Figure 3 It can be seen that when switch K1 is disconnected, the voltage values ​​at each point on the dummy load side are:

[0032] U tp0tp7 =U dc =4500V,

[0033] U tp1tp7 =2*(U dc-18V) / 3+18V=3006V,

[0034] U tp3tp7 =(U dc -18V) / 3+18V=1512V,

[0035] U tp5tp7 =18V.

[0036] According to the emitter follower principle of transistor, ignoring the transistor junction voltage U be (usually 0.7V), the potential at each point of high-voltage constant-current discharge is:

[0037] U tp0tp7 =U dc =4500V,

[0038] U tp2tp7 =2*(U dc -18V) / 3+18V=3006V,

[0039] U tp4tp7 =(U dc -18V) / 3+18V=1512V,

[0040] U tp6tp7 =18V.

[0041] From these data, we can see that each transistor circuit has the same voltage, which achieves the purpose of series voltage division and voltage balancing, breaking the whole into zero.

[0042] U tp0tp2 =U dc -U tp2tp7 =4500V-3006V=1494V,

[0043] U tp2tp4 =U tp2tp7 -U tp4tp7 =3006V-1512V=1494V,

[0044] U tp4tp6 =U tp4tp7 -U tp6tp7 =1512V-18V=1494V,

[0045] The discharge resistors R0, R1, R2, and R3 are of the same specification, and here they are 10Ω. Then the current I on the resistor R0 is R0 =U tp6tp7 / R0=18V / 10Ω=1.8A. This current flows through R1, R2, and R3. When switch K1 is disconnected, such a large constant current can consume the energy on the output capacitor at once, so the output voltage can drop quickly. The size of the discharge current can be constrained by resistor R0. When rapid discharge is required, the resistance of resistors R0 to R3 can be reduced to shorten the discharge time.

[0046] When the power supply is working normally, the control switch K1 is closed and the discharge circuit does not discharge. tp5tp7 =0V, according to the emitter follower principle of transistor, U tp6tp7 =0V, the current I on the resistor R0 R0 =0A. R1, TR1, R2, TR2, R3, TR3, R0 are connected in series, and the currents are equal, which is 0A at this time, and no longer discharge. At this time, the voltage on the three transistors Uce = 4500V / 3 = 1500V.

[0047] The switch K1 is a transistor switch, such as a triode, COMS, etc., and can also be a switch controlled by infrared light, such as a photodiode, a phototransistor, etc.

[0048] Figure 4 The power supply system block diagram is given. The power supply system consists of voltage and current detection ⑤, control and drive ④, MCU ③ and operation panel ⑥. Voltage and current detection ⑤ mainly detects the voltage and current at the output end of the main circuit ①, and provides the detection to MCU ③. MCU ③ processes the voltage, current, communication and other data, controls ④ drive and controls the corresponding switch tube, discharge switch and some timing logic.

[0049] As an improvement, in order to achieve low input voltage and high output voltage, the inverter H-bridge switch tube in the inverter uses CMOS tube, and the voltage level is selected at 2.5 times. When the input voltage is DC48V, the voltage level is increased to 100V. Furthermore, the resonant inductor Lr1 in the LLC resonant circuit is made of ferrite material, the winding is multi-strand copper wire, and the resonant capacitor is a CBB capacitor. When the input voltage is DC48V, the voltage level is 200V. On this basis, the transformer is made of high-frequency ferrite material. When the input voltage is DC48V and the maximum output voltage is DC4500V, the primary and secondary turns ratio is 1:10, and the primary secondary winding is wound in layers with multi-strand copper wire.

[0050] The dummy load circuit is composed of a resistor and a voltage regulator. The base current of the transistor is ignored. The resistors have uniform specifications, and the resistance and power level are the same. The constant current discharge method is adopted. The discharge current is determined by the resistor R0, and the resistance specifications of the discharge circuit are the same. The discharge time can be changed by adjusting the resistance value.

[0051] The discharge switch K1 can be a transistor, a photosensitive diode, a triode, or other switches. If a transistor, such as a triode or a CMOS tube, is used as a control switch, it is necessary to take power from the high voltage output end to work under control. This is very troublesome, so the present invention uses a photosensitive diode or a photosensitive triode as a control switch, such as Figure 5 As shown. The photosensitive diode or triode used as the control switch can be directly controlled by the optical fiber, and it is not necessary to obtain energy at the high-voltage end to work. The discharge switch at the high-voltage end is controlled by the optical fiber. When there is light, the switch (photosensitive tube) is turned on (the resistance is infinitely small), and when there is no light, it is turned off (the resistance is infinitely large).

[0052] The PID algorithm is implemented in the MCU, and the calculated value is output to the corresponding IO port, and then the CMOS and other devices are controlled by the drive circuit. The entire power supply can be remotely operated, which is convenient for networking and integration. The MCU uses LSC335 with an operating frequency of 150MHz. The primary and secondary sides of the power supply are completely isolated, the energy circuit is isolated by a transformer, and the control circuit is isolated by optical fiber.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A high voltage DC power supply based on constant current discharge, The main power circuit includes a power input terminal, an inverter circuit, an LLC resonant circuit, a voltage doubler rectifier circuit, and a power output terminal connected in sequence, and is characterized in that: A high-voltage constant-current discharge circuit is connected across both ends of the power supply output; The high-voltage constant-current discharge circuit at least includes a dummy load circuit, a constant-current source circuit, and a control switch K1; The dummy load circuit includes N load resistors of the same specification and a voltage regulator tube. After the load resistors are connected in series, one end is connected to the positive output end of the power supply, and the other end is used as the grounded end. The grounded end is connected to the cathode of the voltage regulator tube, and the anode of the voltage regulator tube is connected to the negative output end of the power supply as the ground. N is a positive integer. The constant current source circuit includes N+1 discharge resistors and N transistors with the same specifications. The discharge resistors are connected in series and connected across the two ends of the power supply output terminal. A transistor is connected in series between every two discharge resistors. The base of the first transistor is connected to the connection point between the first load resistor and the second load resistor, the base of the second transistor is connected to the connection point between the second load resistor and the third load resistor, and so on. The base of the last transistor is connected to the connection point between the last load resistor and the voltage regulator tube. The control switch K1 is connected in parallel with the voltage regulator tube.

2. The high voltage DC power supply according to claim 1, characterized in that: The control switch K1 is a photodiode or a phototransistor.

3. The high voltage DC power supply according to claim 2, characterized in that: The photodiode or transistor used as the control switch is controlled through the optical fiber.

4. The high voltage DC power supply according to claim 1, characterized in that: The control switch K1 is a transistor that is powered by the high voltage output terminal.

5. The high voltage DC power supply according to claim 1, characterized in that: The resonant inductor Lr1 in the LLC resonant circuit is made of ferrite material, and the winding wire is a multi-strand input copper wire. The resonant capacitor in the LLC resonant circuit is a CBB capacitor.

6. The high voltage DC power supply according to claim 5, characterized in that: The transformer in the LLC resonant circuit is made of high-frequency ferrite material, the primary-to-secondary turns ratio is 1:10, and the primary-to-secondary winding is wound in layers with multiple strands of copper wire.

7. The high voltage DC power supply according to claim 1, characterized in that: The voltage doubler rectifier circuit is connected to the power output terminal via a filter circuit formed by multiple capacitors connected in series.

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