CN101982934A - Soft starting device and method of high-power switching power supply - Google Patents

Abstract

The invention provides a soft starting device of a high-power switching power supply, comprising a soft starting charging circuit, a three-phase bridge rectified thyristor series circuit, a filter capacitor voltage detection circuit, a current detection and changeover decision circuit, a pulse power supply charging circuit, a pulse generating circuit and a filter capacitor, wherein the soft starting charging circuit is connected with the three-phase bridge rectified thyristor series circuit in parallel; the filter capacitor voltage detection circuit is connected with the pulse power supply charging circuit and the three-phase bridge rectified thyristor series circuit; the current detection and changeover decision circuit is connected with the pulse power supply charging circuit, the pulse generating circuit and the soft starting charging circuit; the pulse power supply charging circuit is connected with the pulse generating circuit; the pulse generating circuit is connected with the three-phase bridge rectified thyristor series circuit and the soft starting charging circuit; and the filter capacitor is connected with the circuits respectively. The invention also provides a soft starting method implemented by the device. The invention can strictly ensure the order of the core in the soft starting process.

Description

Soft-start device and method for high-power switching power supply

technical field

The invention belongs to the technical field of power starting, and in particular relates to a soft starting device and method for a high-power switching power supply.

Background technique

In the input stage circuit of a high-power switching power supply, the filter capacitor connected in parallel with the rectifier circuit is a large-capacity electrolytic capacitor, and the voltage rectified by the rectifier bridge is relatively high. At the moment of power-on, the voltage at both ends of the filter capacitor is zero. At this time, if the rectified voltage is directly applied to both ends of the filter capacitor without passing through the current-limiting resistor, a large inrush current will be generated, which will easily cause damage to components. . Therefore, we must design a device so that the voltage across the capacitor rises slowly at the moment of power-on, so as to avoid the above-mentioned faults, which is what we call the soft-start problem.

Commonly used soft start methods have the following four schemes:

(1) Connect the thermistor in series

As shown in Figure 1, the soft start circuit includes a rectifier bridge composed of diode 1, diode 2, diode 3, diode 4, diode 5, and diode 6, a thermistor 7, a capacitor 8, an insulated gate transistor 9, an insulated gate transistor 10. The insulated gate transistor 11, the insulated gate transistor 12 and the transformer 13 rectify and bridge the three phase lines 99, 100, 101 of the AC power supply; the thermistor 7 is a thermistor with a negative temperature coefficient. The thermistor 7 with a negative temperature coefficient characteristic has a large resistance at room temperature, and the resistance of the thermistor 7 drops sharply after being energized and heated. Utilizing the characteristics of the thermistor 7 can reduce the inrush current at the moment of power-on, and reduce the power consumption when the power supply is working normally. The disadvantage of this solution is that, with the increase of the input current, the power consumption of the thermistor 7 also increases, thereby reducing the efficiency of the input stage circuit, and further restricting the overall efficiency of the entire switching power supply. In high-power switching power supplies, the input current is relatively large. Therefore, this soft-start scheme is not suitable for high-power switching power supplies.

(2) Current limiting resistor, contactor switching

As shown in Figure 2, the soft start circuit includes a rectifier bridge composed of diode 14, diode 15, diode 16, diode 17, diode 18, diode 19, a current limiting resistor 20, a contactor contact 21, a contactor coil 22, Relay contacts 23, relay coils 24, capacitors 25, insulated gate transistors 26, insulated gate transistors 27, insulated gate transistors 28, insulated gate transistors 29, transformers 30, three phase lines 99, 100, 101 of rectifying and bridged AC power; At the instant of electricity, the coil 22 of the contactor is not conducting, the contact 21 of the contactor is in the disconnected state, the rectifier circuit charges the capacitor 25 through the current limiting resistor 20, and when the voltage of the capacitor 25 is charged to the preset voltage value, the coil of the relay 24 is turned on, the contact 23 of the relay is closed, the coil 22 of the contactor is turned on, the contact 21 of the contactor is closed, and the current-limiting resistor 20 is short-circuited, so that when the power supply is working normally, the current-limiting resistor 20 does not generate power consumption , overcome the shortcoming of scheme (1). The disadvantage of this solution is that the conductive part of the contactor is a movable contact, which is not suitable for passing large currents; the operating voltage of the relay will vibrate and oscillate, resulting in unreliable operation.

(3) Thyristor three-phase full-bridge half-controlled rectification

As shown in Figure 3, the circuit includes a half-controlled rectifier bridge composed of diode 34, diode 35, diode 36, thyristor 31, thyristor 32, thyristor 33, filter capacitor 37, insulated gate transistor 38, insulated gate transistor 39, insulated gate Transistor 40, insulated gate transistor 41 and transformer 42, three phase lines 99, 100, 101 of rectification bridge AC power supply; The voltage rises slowly according to the set rule to realize soft start. The disadvantage of this solution is that the thyristor half-controlled rectifier bridge is expensive, the cost is high, and the conduction angle needs to be controlled, no trigger is not allowed, and the design of the trigger circuit is complicated.

(4) Current limiting resistor, thyristor switching

As shown in Figure 4, the circuit includes a rectifier bridge composed of diode 43, diode 44, diode 45, diode 46, diode 47, diode 48, a thyristor 49, a current limiting resistor 50, a filter capacitor 51, an insulated gate transistor 52, an insulating The gate transistor 53, the insulated gate transistor 54, the insulated gate transistor 55 and the transformer 56 rectify and bridge the three phase lines 99, 100, 101 of the AC power supply; when the power is turned on, the rectifier circuit charges the filter capacitor 51 through the current limiting resistor 50, etc. When the voltage of the filter capacitor 51 is charged to a desired value, the thyristor 49 is triggered. The disadvantage of this scheme is that no triggering is allowed.

Contents of the invention

The object of the present invention is to overcome the shortcomings and deficiencies of the above-mentioned prior art, and provide a soft start device for a high-power switching power supply that has a simple and reasonable structure and can reliably ensure that the filter capacitor voltage rises to the desired voltage first and then the pulse generating circuit restarts. .

The present invention adopts following technical scheme:

Soft start device for high-power switching power supply, including soft start charging circuit, three-phase bridge rectification series thyristor circuit, filter capacitor voltage detection circuit, current detection switching judgment circuit, pulse power supply charging circuit, pulse generating circuit and filter capacitor, soft start The charging circuit is connected in parallel with the three-phase bridge rectification series thyristor circuit; the filter capacitor voltage detection circuit is connected with the pulse power supply charging circuit and the three-phase bridge rectification series thyristor circuit; the current detection switching judgment circuit is respectively connected with the pulse power supply charging circuit and the pulse generating circuit , soft-start charging circuit connection; the pulse power supply charging circuit is connected with the pulse generating circuit; the pulse generating circuit is respectively connected with the three-phase bridge rectifier series thyristor circuit and the soft-start charging circuit; the soft-start charging circuit, the three-phase bridge The rectification series thyristor circuit, the filter capacitor voltage detection circuit, the current detection switching judgment circuit, the pulse power supply charging circuit, and the pulse generation circuit are all connected to the filter capacitor; the soft start charging circuit, the pulse power supply charging circuit, and the three-phase bridge rectification series thyristor The circuits are respectively externally connected with three-phase AC power supply.

The three-phase bridge rectification series thyristor circuit includes an eighth diode, a ninth diode, a tenth diode, an eleventh diode, a twelfth diode, a thirteenth diode and Thyristor, the eighth diode, the ninth diode, the tenth diode, the eleventh diode, the twelfth diode and the thirteenth diode are all power diodes; The pole tube is connected in series with the eleventh diode, the ninth diode is connected in series with the twelfth diode, the tenth diode is connected in series with the thirteenth diode; the cathode of the eighth diode, the ninth second diode The cathode of the pole tube and the cathode of the tenth diode are connected to each other, and both are connected to the anode of the thyristor; the anode of the eleventh diode, the anode of the twelfth diode and the anode of the thirteenth diode are connected to each other connected, and both are connected to the negative pole of the filter capacitor; the cathode of the thyristor is connected to the positive pole of the filter capacitor, and its gate is connected to the pulse generating circuit; between the anode of the eighth diode and the cathode of the eleventh diode , between the anode of the ninth diode and the cathode of the twelfth diode, and between the anode of the tenth diode and the cathode of the thirteenth diode, are respectively connected to the three-phase AC power supply through the lead wires On the phase line, the cathodes of the eleventh diode, the twelfth diode, and the thirteenth diode are respectively connected to the soft-start charging circuit.

The soft start charging circuit includes a fourth diode, a sixth diode, a seventh diode, a thirteenth resistor and a fourteenth resistor, and the fourth diode, the sixth diode and the first The seven diodes are all rectifier diodes; the thirteenth resistor is connected in series with the fourteenth resistor, and the other end of the thirteenth resistor is respectively connected to the cathode of the fourth diode, the cathode of the sixth diode, and the cathode of the seventh diode The other end of the fourteenth resistor is connected to the current detection switching judgment circuit, the positive pole of the filter capacitor, and the pulse generating circuit respectively; the anode of the fourth diode, the anode of the sixth diode, and the seventh diode The anodes are respectively connected to the three phase lines of the three-phase AC power supply, and are respectively connected to the cathode of the eleventh diode, the cathode of the twelfth diode, and the thirteenth diode in the three-phase bridge rectifier series thyristor circuit. the cathode connection.

The current detection switching decision circuit includes a fifth diode, a third diode, a fourth resistor, a sixth capacitor, a ninth resistor, an eleventh resistor and a fourth triode, and the sixth capacitor is an electrolytic capacitor; the anode of the fifth diode is connected between the thirteenth resistor and the fourteenth resistor in the soft-start charging circuit, and the cathode of the fifth diode is respectively connected to the anode of the third diode and the sixth capacitor Positive connection; the anode of the third diode is connected to the positive pole of the sixth capacitor, and its cathode is respectively connected to one end of the fourth resistor and the pulse power supply charging circuit; the other end of the fourth resistor is charged to the negative pole of the sixth capacitor and the pulse power supply Circuit connection; one end of the ninth resistor is connected to the cathode of the fifth diode, the anode of the third diode, and the anode of the sixth capacitor, and the other end is connected to the base of the eleventh resistor and the fourth triode. One end of the eleventh resistor is connected to the base of the fourth transistor, and the other end is connected to the negative electrode of the sixth capacitor; the emitter of the fourth transistor is connected to the negative electrode of the sixth capacitor, and its collector is connected to the negative electrode of the sixth capacitor. The pulse generating circuit is connected, and the negative pole of the sixth capacitor is respectively connected with the positive pole of the filter capacitor and the fourteenth resistor in the soft-start charging circuit.

The pulse power supply charging circuit includes a transformer, a first diode, a first triode, a second resistor, a second diode and a first capacitor, the first capacitor is an electrolytic capacitor, and the primary two ends of the transformer are respectively It is connected to the zero line and one phase line of the three-phase AC power supply, one end of its secondary is connected to the collector of the third transistor in the filter capacitor voltage detection circuit, and the other end of the secondary is connected to the anode of the first diode. The cathode of the diode is connected to the emitter of the first triode, the base of the first triode is connected to the anode of the second diode, and the cathode of the second diode is connected to the current detection switching judgment circuit; The collector of a triode is connected to the positive pole of the first capacitor and the pulse generating circuit; the negative pole of the first capacitor is connected to the current detection switching judgment circuit and the positive pole of the filter capacitor; one end of the second resistor is connected to the first diode between the cathode of the first triode and the emitter of the first triode, and the other end is connected between the base of the first triode and the anode of the second diode.

The pulse generating circuit includes a first resistor, a second triode, a unijunction transistor, a twelfth resistor, a third resistor, a second capacitor, a tenth resistor, a fifth capacitor, a fourth capacitor and an eighth resistor, and the One end of a resistor is respectively connected to the pulse power supply charging circuit, and the other end is connected to the emitter of the second triode; the collector of the second triode is connected to the gate of the unijunction transistor, and the base of the second triode It is connected to the anode of the unijunction transistor; the cathode of the unijunction transistor is connected to one end of the twelfth resistor, and the other end of the twelfth resistor is connected to the gate of the thyristor in the three-phase bridge rectification series thyristor circuit; the third resistor One end is respectively connected to the first resistor and the emitter of the second triode, and the other end is respectively connected to the base of the second triode, the anode of the unijunction transistor, and the current detection switching judgment circuit; one end of the second capacitor is connected to the single The anode of the junction transistor is connected, and the other end is connected with the negative pole of the sixth capacitor and the positive pole of the filter capacitor in the current detection switching judgment circuit; one end of the tenth resistor and the fifth capacitor are connected with the cathode of the unijunction transistor, and the other end is connected with the current The negative pole of the sixth capacitor in the detection switching judgment circuit is connected to the positive pole of the filter capacitor; the fourth capacitor is connected in parallel with the eighth resistor, and one end thereof is connected to the gate electrode of the unijunction transistor and the collector electrode of the second triode, and the other end All are connected to the negative pole of the sixth capacitor and the positive pole of the filter capacitor in the current detection switching decision circuit; the tenth resistor, the fifth capacitor, the fourth capacitor and the eighth resistor are all connected to the soft-start charging circuit.

One end of the first resistor is respectively connected to the positive pole of the first capacitor in the pulse power supply charging circuit and the collector of the first triode, and the other end is connected to the emitter of the second triode; one end of the third resistor The first resistor and the emitter of the second triode are respectively connected, and the other end is respectively connected with the base of the second triode, the anode of the unijunction transistor, and the collector of the fourth triode in the current detection switching judgment circuit .

The filter capacitor voltage detection circuit includes a third triode, a third capacitor, and a sixth resistor, a seventh resistor, and a fifth resistor connected in series in sequence, the third capacitor is an electrolytic capacitor; the other end of the fifth resistor is connected to the filter The positive pole of the capacitor, the positive pole of the third capacitor, and the emitter of the third triode are connected, and the other end of the sixth resistor is connected to the negative pole of the filter capacitor and the three-phase bridge rectifier series thyristor circuit; the negative pole of the third capacitor is connected to the Between the seventh resistor and the fifth resistor and connected to the base of the third transistor; the base of the third transistor is connected between the seventh resistor and the fifth resistor, and the collector of the third transistor is connected to the pulse One end of the transformer secondary in the power charging circuit is connected.

The soft start method of the high-power switching power supply realized by the above-mentioned device comprises the following steps:

(1) The high-power switching power supply is powered on by connecting to the three-phase alternating current;

(2) The soft start charging circuit charges the filter capacitor;

(3) The current detection switching judgment circuit detects the current of the soft-start charging circuit. At the same time, the filter capacitor voltage detection circuit detects the voltage across the filter capacitor. If the current of the soft-start charging circuit and the voltage across the filter capacitor both meet conditions, the pulse power supply charging circuit works;

(4) On the basis of step (3), the current detection switching judgment circuit detects the current of the soft-start charging circuit, if the current of the soft-start charging circuit is so small that the fourth triode in the current detection switching judgment circuit is cut off , the pulse generating circuit works;

(5) The pulse generation circuit generates pulses, triggers the thyristors in the three-phase bridge rectification series thyristor circuit, switches to the three-phase bridge rectification series thyristor circuit to charge the filter capacitor, and completes the soft start of the high-power switching power supply.

The specific steps that the soft-start charging circuit charges the filter capacitor in the step (2) include: the currents on the three phase lines of the three-phase alternating current pass through the fourth diode, the sixth diode, the The seventh diode and the eleventh diode, the twelfth diode, and the thirteenth diode in the three-phase bridge rectification series thyristor circuit constitute the output of the three-phase full-bridge rectifier circuit, and then pass through the tenth diode in turn. The three resistors and the fourteenth resistor charge the filter capacitor;

In the step (3), when the current of the soft-start charging circuit is less than the set value and the voltage at both ends of the filter capacitor is greater than the set value, the first triode in the pulse power supply charging circuit is turned on, so that the pulse power supply The charging circuit works; the three-phase alternating current supplies current to the transformer through its zero line and phase line, and the current passes through the first diode, the first triode, the second resistor, the second diode and the first capacitor respectively, and passes through the first A capacitor stores energy and supplies power to the pulse generating circuit;

In the step (5), the specific steps of the pulse generation circuit triggering the thyristor in the three-phase bridge rectification series thyristor circuit include: the voltage on the sixth capacitor in the current detection switching judgment circuit decreases continuously with the charging current of the filter capacitor When it drops to the set value, the fourth transistor changes from on to off, and the pulse generating circuit charges the fourth capacitor through the first resistor, the third resistor and the second transistor, and when the voltage on the second capacitor When it rises to close to the voltage on the first capacitor in the pulse power supply charging circuit, the second triode is turned off, so that the fourth capacitor is discharged through the eighth resistor, and when the voltage on the fourth capacitor drops to a certain value, the unijunction transistor is turned off. trigger, a pulse voltage is formed on the tenth resistor and the fifth capacitor, and the thyristor in the three-phase bridge rectification series thyristor circuit is triggered by the twelfth resistor; after the thyristor is triggered, the eighth diode, the ninth two-pole The three-phase full-bridge rectifier circuit composed of the tenth diode, the eleventh diode, the twelfth diode, and the thirteenth diode charges the filter capacitor through the thyristor, thereby completing the soft-start charging circuit to the Three-phase bridge rectifier switching in series thyristor circuits.

The principle of the present invention: when the high-power switching power supply is powered on, the soft-start charging circuit charges the large-capacity filter capacitor. At this time, the voltage across the filter capacitor is low and is not higher than the set voltage value. If the current is large and not less than the set current value, the charging circuit of the pulse power supply cannot enter the running state. As the voltage across the filter capacitor continues to increase, when the voltage of the filter capacitor is higher than the set voltage value, but at this time the soft-start charging current (the current of the soft-start charging circuit) is still higher than the set value, the pulse power charging circuit Still can't get into running state. As the soft-start charging current decreases, when the charging current is lower than the set value, it means that the difference between the output voltage of the rectifier circuit and the voltage across the filter capacitor is less than the set value. At this time, the pulse power supply charging circuit is put into operation. When charging When the current is further reduced to another set value, the pulse generating circuit is put into operation. At this time, the charging circuit of the filter capacitor is switched from the soft-start charging circuit to the three-phase bridge rectification series thyristor circuit, thus realizing the desired filter capacitor voltage. Switching of the lower charging circuit. The control of the pulse power supply charging circuit by the current detection switching judgment circuit and the filter capacitor voltage detection circuit is "AND" logic, that is, only when the two circuits reach the set target, the pulse power supply charging circuit will be put into operation.

The fifth resistor, the sixth resistor and the seventh resistor divide the voltage across the filter capacitor. When the voltage divided by the fifth resistor reaches the conduction voltage of the emitter junction of the third triode, the transformer of the pulse power supply charging circuit level to output current. In this way, we can control the third triode to turn on when the voltage across the filter capacitor reaches the desired value by properly selecting the resistance values of the fifth resistor, the fifth resistor and the seventh resistor, and the third capacitor It acts as a filter to prevent the high-frequency interference voltage from causing the third transistor to conduct.

The thirteenth resistor and the fourteenth resistor not only act as the current limiting resistors of the soft-start charging circuit, but also perform the task of detecting the charging current. The voltage dropped across the fourteenth resistor charges the sixth capacitor through the fifth diode, so that the voltage across the sixth capacitor is basically equal to the voltage drop across the fourteenth resistor. When the soft-start charging current is large, the voltage dropped on the thirteenth resistor and the fourteenth resistor is high, and the voltage on the sixth capacitor is also high. The transformer is a step-down transformer, and the effective value of the secondary voltage is 9 Volts, the peak voltage output by the first diode is about 12 volts, therefore, when the voltage on the sixth capacitor is higher than 12 volts, the second diode is always in the cut-off state, so that the first triode is basically The polar current is zero and is in a cut-off state, so that the first capacitor cannot be charged, so that the pulse generating circuit using the first capacitor as a power supply cannot work. When the voltage across the filter capacitor is higher than the set voltage value, when the soft-start charging current is so small that the voltage on the sixth capacitor is lower than 12 volts, the second diode starts to conduct, so that the first three The pole transistor is turned on to charge the first capacitor, that is, the pulse power supply charging circuit works. The ninth resistor and the eleventh resistor divide the voltage on the sixth capacitor, and the resistance values of the ninth resistor and the eleventh resistor are appropriately selected so that when the voltage on the sixth capacitor is greater than an appropriate value, the fourth triode is saturated and conducts On, the second capacitor cannot be charged, and the pulse generating circuit does not work. When the voltage across the sixth capacitor is less than a certain threshold, the fourth transistor is turned off, and the pulse generating circuit is put into operation.

The pulse generation circuit is a relaxation oscillation circuit with a unijunction transistor as the core. When the voltage on the second capacitor is lower than the voltage on the first capacitor in the pulse power supply charging circuit to exceed the conduction voltage of the emitter junction of the second triode, the first capacitor passes through the first resistor, the third resistor and the second triode The emitter junction of the tube charges the second capacitor, and at the same time charges the fourth capacitor through the collector of the second triode. The resistance value of the eighth resistor is selected to be large enough to ensure that the discharge speed of the fourth capacitor is slower than the charging speed. Therefore, the voltage on the fourth capacitor can be quickly charged to a saturation voltage drop lower than the emitter voltage of the second transistor, and as long as the second transistor is turned on, the voltage on the second capacitor It is an emitter junction conduction voltage lower than the emitter voltage of the second triode. It can be seen that when the triode is turned on, the voltage on the fourth capacitor is higher than the voltage on the second capacitor, and the unijunction transistor is in the cut-off state. When the voltage on the second capacitor rises to the point where the voltage drop on the third resistor is less than the conduction voltage of the emitter junction of the second transistor, the second transistor is turned off, the second capacitor continues to charge through the third resistor, and the fourth capacitor passes through The eighth resistor discharges until the voltage on the fourth capacitor is lower than the voltage on the second capacitor to trigger the unijunction transistor. When the unijunction transistor is triggered and turned on, both the second capacitor and the fourth capacitor pass through the unijunction transistor quickly. Discharge, and generate a pulse current through the twelfth resistor to trigger the thyristor. When the unijunction transistor returns to the cut-off state, there is only a very low residual voltage on the second capacitor and the fourth capacitor, so charging starts again, that is, the pulse generating circuit starts In the pulse generation process of the next cycle, the tenth resistor and the fifth capacitor function as filters to prevent the high-frequency interference voltage from triggering the thyristor by mistake.

When the high-power switching power supply is powered on, the filter capacitor voltage is zero, and the third transistor is not conducting. At this time, the soft-start charging current is large, the first transistor is not conducting, and the fourth transistor is saturated. conduction, so the pulse power supply charging circuit and the pulse generating circuit do not work. As the voltage of the filter capacitor increases continuously and is higher than the voltage setting value, the third transistor is turned on. On the other hand, the soft-start charging current decreases continuously and is less than the current setting value, that is, the difference between the output voltage of the rectifier circuit and the voltage across the filter capacitor reaches the setting value. At this point, the charging circuit of the pulse power supply is put into operation and starts to charge the first capacitor. After the voltage across the first capacitor rises to an appropriate value, and the soft-start charging current is further reduced, the voltage on the sixth capacitor drops to the first The four triodes are cut off, the pulse generating circuit is put into operation, and the circuit switches from the soft-start charging state to the three-phase bridge rectification charging state. The current detection and switching judgment circuit and the filter capacitor voltage detection circuit constitute the double insurance of circuit safety. Once one of the circuits fails to work due to various reasons, the other circuit can work alone to protect the switching power supply from great impact.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The present invention ensures that the circuit can still operate at a suitable filter capacitor voltage under the condition of interference by designing the filter capacitor voltage detection circuit, the current detection switching judgment circuit, and the soft start circuit, etc. Switch from the soft-start charging circuit to the three-phase bridge rectification series thyristor circuit to charge the filter capacitor.

(2) The device of the present invention is simple and low in cost.

Description of drawings

Fig. 1 is a schematic structural diagram of the prior art.

Fig. 2 is a second structure schematic diagram of the prior art.

Fig. 3 is a schematic diagram of a third structure of the prior art.

Fig. 4 is a schematic diagram of a fourth structure of the prior art.

Fig. 5 is a schematic structural view of the device of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example

As shown in Figure 5, the soft start device of this high-power switching power supply includes a soft start charging circuit, a three-phase bridge rectification series thyristor circuit, a filter capacitor voltage detection circuit, a current detection switching judgment circuit, a pulse power supply charging circuit, and a pulse generation circuit and filter capacitor 97, the soft-start charging circuit is connected in parallel with the three-phase bridge rectifier series thyristor circuit; the filter capacitor voltage detection circuit is connected with the pulse power supply charging circuit and the three-phase bridge rectifier series thyristor circuit; The power supply charging circuit, the pulse generating circuit, and the soft-start charging circuit are connected; the pulse power charging circuit is connected with the pulse generating circuit; the pulse generating circuit is respectively connected with the three-phase bridge rectification series thyristor circuit, and the soft-start charging circuit; the soft-start The charging circuit, the three-phase bridge rectification series thyristor circuit, the filter capacitor voltage detection circuit, the current detection switching judgment circuit, the pulse power supply charging circuit, and the pulse generating circuit are all connected to the filter capacitor 97; the soft start charging circuit, the pulse power supply charging circuit and the three-phase bridge rectification series thyristor circuit are respectively externally connected with a three-phase AC power supply.

The three-phase bridge rectification series thyristor circuit includes an eighth diode 90, a ninth diode 91, a tenth diode 92, an eleventh diode 93, a twelfth diode 94, a tenth diode Three diodes 95 and thyristors 96, the eighth diode 90, the ninth diode 91, the tenth diode 92, the eleventh diode 93, the twelfth diode 94 and the tenth diode The three diodes 95 are all power diodes; the eighth diode 90 is connected in series with the eleventh diode 93, the ninth diode 91 is connected in series with the twelfth diode 94, and the tenth diode 92 is connected in series with the twelfth diode 94. Thirteen diodes 95 are connected in series; the cathode of the eighth diode 90, the cathode of the ninth diode 91 and the cathode of the tenth diode 92 are connected to each other, and are all connected to the anode of the thyristor 96; The anode of the pole tube 93, the anode of the twelfth diode 94 and the anode of the thirteenth diode 95 are connected to each other, and are all connected to the negative pole of the filter capacitor 97; the cathode of the thyristor 96 is connected to the positive pole of the filter capacitor 97, Its gate is connected to the twelfth resistor 84 in the pulse generating circuit; between the anode of the eighth diode 90 and the cathode of the eleventh diode 93, between the anode of the ninth diode 91 and the tenth Between the cathodes of the two diodes 94, between the anodes of the tenth diode 92 and the cathodes of the thirteenth diode 95 are respectively externally connected to the three phase lines 99, 100, 101 of the three-phase AC power supply through lead wires , and the cathode of the eleventh diode 93, the cathode of the twelfth diode 94, and the cathode of the thirteenth diode 95 are respectively connected to the soft-start charging circuit.

The soft start charging circuit includes a fourth diode 85, a sixth diode 86, a seventh diode 87, a thirteenth resistor 88 and a fourteenth resistor 89, the fourth diode 85, the The six diodes 86 and the seventh diode 87 are rectifier diodes; the thirteenth resistor 88 is connected in series with the fourteenth resistor 89, and the other end of the thirteenth resistor 88 is respectively connected to the cathode of the fourth diode 85 and the fourth diode 85 The cathode of the six diodes 86 and the cathode of the seventh diode 87 are connected, and the other end of the fourteenth resistor 89 is respectively connected to the negative pole of the sixth capacitor 70 in the current detection switching judgment circuit, the positive pole of the filter capacitor 97, and the pulse generating circuit The tenth resistor 80, the fifth capacitor 81, the fourth capacitor 82 and the eighth resistor 83 are connected; the anode of the fourth diode 85, the anode of the sixth diode 86, and the anode of the seventh diode 87 are respectively It is connected with the three phase lines 99, 100, 101 of the three-phase AC power supply, and respectively connected with the cathode of the eleventh diode 93, the cathode of the twelfth diode 94, the cathode of the tenth diode 94 in the three-phase bridge rectification series thyristor circuit. The cathodes of three diodes 95 are connected.

The current detection switching decision circuit includes a fifth diode 69, a third diode 71, a fourth resistor 67, a sixth capacitor 70, a ninth resistor 72, an eleventh resistor 73 and a fourth transistor 74, The sixth capacitor 70 is an electrolytic capacitor; the anode of the fifth diode 69 is connected between the thirteenth resistor 88 and the fourteenth resistor 89 in the soft-start charging circuit, and the cathode of the fifth diode 69 is respectively connected to The anode of the third diode 71 is connected to the positive pole of the sixth capacitor 70; the anode of the third diode 71 is connected to the positive pole of the sixth capacitor 70, and its cathode is respectively connected to one end of the fourth resistor 67 and the pulse power supply charging circuit. The cathode of the second diode 66 is connected; the other end of the fourth resistor 67 is connected with the negative pole of the sixth capacitor 70 and the negative pole of the first capacitor 68 in the pulse power charging circuit; one end of the ninth resistor 72 is connected with the fifth The cathode of diode 69, the anode of the third diode 71, the anode of the sixth capacitor 70 are connected, and its other end is connected with the base of the eleventh resistor 73 and the fourth triode 74; the eleventh resistor 73 One end of the fourth triode 74 is connected to the base, and the other end is connected to the negative pole of the sixth capacitor 70; the emitter of the fourth triode 74 is connected to the negative pole of the sixth capacitor 70, and its collector is connected to the pulse generating circuit The anode of the unijunction transistor 79 is connected, the negative pole of the sixth capacitor 70 is respectively connected to the positive pole of the filter capacitor 97, and the fourteenth resistor 89 in the soft-start charging circuit.

The pulse power supply charging circuit includes a transformer 62, a first diode 63, a first triode 64, a second resistor 65, a second diode 66 and a first capacitor 68, and the first capacitor 68 is an electrolytic capacitor , the primary two ends of the transformer 62 are respectively connected with the zero line 98 and a phase line 99 of the three-phase AC power supply, and its secondary end is connected with the collector of the third triode 61 in the filter capacitor voltage detection circuit, and its secondary end is connected with The anode of the first diode 63 is connected, the cathode of the first diode 63 is connected with the emitter of the first triode 64, the base of the first triode 64 is connected with the anode of the second diode 66, The cathode of the second diode 66 is connected with one end of the fourth resistor 67 and the cathode of the third diode 71 in the current detection switching decision circuit; One end of the first resistor 75 in the generating circuit is connected; the negative pole of the first capacitor 68 is connected with the negative pole of the sixth capacitor 70 in the current detection switching decision circuit and the positive pole of the filter capacitor 97; one end of the second resistor 65 is connected to the first two The cathode of the transistor 63 is connected between the emitter of the first transistor 64 and the other end is connected between the base of the first transistor 64 and the anode of the second diode 66 .

The pulse generating circuit includes a first resistor 75, a second triode 77, a unijunction transistor 79, a twelfth resistor 84, a third resistor 76, a second capacitor 78, a tenth resistor 80, a fifth capacitor 81, a Four capacitors 82 and the eighth resistor 83, one end of the first resistor 75 is respectively connected with the positive pole of the first capacitor 68 of the pulse power supply charging circuit, and the other end is connected with the emitter of the second triode 77; the second triode 77 The collector of the unijunction transistor 79 is connected to the gate of the unijunction transistor 79, and the base of the second triode 77 is connected to the anode of the unijunction transistor 79; the cathode of the unijunction transistor 79 is connected to one end of the twelfth resistor 84, and the twelfth The other end of the resistor 84 is connected to the gate of the thyristor 96 in the three-phase bridge rectification series thyristor circuit; one end of the third resistor 76 is connected to the emitter of the first resistor 75 and the second transistor 77 respectively, and the other end is connected to the emitter of the second triode 77 respectively. The base of the second triode 77, the anode of the unijunction transistor 79, and the collector of the fourth triode 74 of the current detection switching decision circuit are connected; one end of the second capacitor 78 is connected with the anode of the unijunction transistor 79, and the other end It is connected with the negative pole of the sixth capacitor 70 and the positive pole of the filter capacitor 97 in the current detection switching judgment circuit; one end of the tenth resistor 80 and the fifth capacitor 81 are connected with the cathode of the unijunction transistor 79, and the other ends are connected with the current detection switching judgment circuit. In the circuit, the negative pole of the sixth capacitor 70 and the positive pole of the filter capacitor 97 are connected; the fourth capacitor 82 is connected in parallel with the eighth resistor 83, and one end thereof is connected with the gate of the unijunction transistor 79 and the collector of the second triode 77 , the other ends are all connected with the negative pole of the sixth capacitor 70 and the positive pole of the filter capacitor 97 in the current detection switching decision circuit; the tenth resistor 80, the fifth capacitor 81, the fourth capacitor 82 and the eighth resistor 83 are all connected to the soft start The fourteenth resistor 89 in the charging circuit is connected.

One end of the first resistor 75 is respectively connected with the anode of the first capacitor 68 in the pulse power charging circuit and the collector of the first triode 64, and the other end is connected with the emitter of the second triode 77;

One end of the third resistor 76 is respectively connected to the first resistor 75 and the emitter of the second triode 77, and the other end is respectively connected to the base of the second triode 77, the anode of the unijunction transistor 79, and the current detection switch. The collector of the fourth transistor 74 in the decision circuit is connected.

The filter capacitor voltage detection circuit includes a third triode 61, a third capacitor 59 and the sixth resistor 57, the seventh resistor 58 and the fifth resistor 60 connected in series in sequence, the third capacitor 59 is an electrolytic capacitor; The other end of the resistance 60 is connected with the positive pole of the filter capacitor 97, the positive pole of the third capacitor 59, and the emitter of the third triode 61, and the other end of the sixth resistor 57 is connected with the negative pole of the filter capacitor 97; The negative pole is connected between the seventh resistor 58 and the fifth resistor 60 and is connected with the base of the third transistor 61; the base of the third transistor 61 is connected between the seventh resistor 58 and the fifth resistor 60, The collector of the third triode 61 is connected to the secondary end of the transformer 62 of the pulse power charging circuit.

The soft start charging circuit is used to charge the large-capacity filter capacitor 97 when the high-power switching power supply is powered on; the three-phase bridge rectifier series thyristor circuit is used to charge the large-capacity filter capacitor 97 when the high-power switching power supply is working normally; the current detection The switching judgment circuit is used to detect the soft-start charging current, and judge whether to put the pulse power supply charging circuit and the pulse generating circuit into operation. The condition for the pulse power supply charging circuit and the pulse generating circuit to be put into operation is that the voltage on the filter capacitor 97 is higher than the set value , and the soft-start charging current should be less than the set value. It should be pointed out that the charging current ultimately reflects the difference between the output voltage of the rectifier circuit and the voltage across the filter capacitor 97; The voltage is detected, and it is judged whether to put the pulse power supply charging circuit into operation. The condition for the pulse power supply charging circuit to be put into operation is that the voltage across the filter capacitor 97 is greater than the set value and the soft start charging current is less than the set value; the pulse power supply charging circuit is Provide a relatively stable DC voltage for the pulse generating circuit; the pulse generating circuit generates pulses with a higher frequency that can trigger the thyristor.

The soft start method of the high-power switching power supply realized by the above-mentioned device comprises the following steps:

(1) The high-power switching power supply is powered on by connecting to the three-phase alternating current;

(2) The soft start charging circuit charges the filter capacitor 97;

(3) The current detection switching judgment circuit detects the current of the soft-start charging circuit. At the same time, the filter capacitor voltage detection circuit detects the voltage at both ends of the filter capacitor 97. If the conditions are met at the same time, the pulse power supply charging circuit will work;

(4) On the basis of step (3), the current detection switching judgment circuit detects the current of the soft-start charging circuit, if the current of the soft-start charging circuit is so small that the fourth triode 74 in the current detection switching judgment circuit cut off, the pulse generating circuit works;

(5) The pulse generation circuit generates pulses, triggers the thyristors in the three-phase bridge rectification series thyristor circuit, switches to the three-phase bridge rectification series thyristor circuit to charge the filter capacitor 97, and completes the soft start of the high-power switching power supply.

The specific steps that the soft-start charging circuit charges the filter capacitor in the step (2) include: the currents on the three phase lines of the three-phase alternating current pass through the fourth diode 85 and the sixth diode 85 in the soft-start charging circuit respectively. 86. The seventh diode 87 and the eleventh diode 93, the twelfth diode 94, and the thirteenth diode 95 in the three-phase bridge rectification series thyristor circuit constitute the output of the three-phase full-bridge rectifier circuit , and then charge the filter capacitor 97 through the thirteenth resistor 88 and the fourteenth resistor 89 in turn;

In described step (3), when the electric current of soft-start charging circuit is less than setting value and the voltage at two ends of filter capacitor 97 is greater than setting value, then the first triode 64 conduction in the pulse power supply charging circuit, so that The pulse power supply charging circuit works; the three-phase alternating current provides current to the transformer through its zero line and phase line, and the current passes through the first diode 63, the first triode 64, the second resistor 65, the second diode 66 and The first capacitor 68 stores energy through the first capacitor 68 to supply power to the pulse generating circuit;

In the step (5), the specific steps of the pulse generation circuit triggering the thyristor in the three-phase bridge rectification series thyristor circuit include: the voltage on the sixth capacitor 70 in the current detection switching judgment circuit decreases continuously with the charging current of the filter capacitor When it is small and drops to the set value, the fourth triode 74 changes from on to off, and the pulse generating circuit charges the second capacitor 78 through the first resistor 75, the third resistor 76 and the second triode 77, and at the same time , the pulse power supply charging circuit also charges the fourth capacitor 82 via the first resistor 75 and the second triode 77, when the voltage on the second capacitor 78 rises to the voltage close to the first capacitor 68 in the pulse power charging circuit , the second triode 77 is cut off, so that the fourth capacitor 82 is discharged through the eighth resistor 83, and when the voltage on the fourth capacitor 82 drops to a certain value, the unijunction transistor 79 is triggered, and the tenth resistor 80 and the fifth capacitor 81 forms a pulse voltage and triggers the thyristor 96 in the three-phase bridge rectification series thyristor circuit through the twelfth resistor 84; after the thyristor is triggered, the eighth diode 90, the ninth diode 91, the twelfth diode The three-phase full-bridge rectifier circuit formed by the pole transistor 92, the eleventh diode 93, the twelfth diode 94, and the thirteenth diode 95 charges the filter capacitor 97 through the thyristor, thereby completing the soft-start charging circuit to Three-phase bridge rectifier switching in series thyristor circuits.

The principle of the present invention: when the high-power switching power supply is powered on, the soft-start charging circuit charges the large-capacity filter capacitor 97. At this time, the voltage at both ends of the filter capacitor 97 is relatively low, and is not higher than the set voltage value, and this When the charging current is large, and it is not less than the set current value, the pulse power supply charging circuit cannot be put into operation. With the continuous increase of the voltage across the filter capacitor 97, when the voltage of the filter capacitor 97 is higher than the set voltage value first, but at this time the soft-start charging current (the current of the soft-start charging circuit) is still higher than the set value, the pulse The power charging circuit still cannot be put into operation. With the continuous reduction of the soft-start charging current, when the charging current is lower than the set value, the charging circuit of the pulse power supply is put into operation. The circuit is also put into operation. At this time, the charging circuit of the filter capacitor 97 is switched from the soft-start charging circuit to the three-phase bridge rectification series thyristor circuit, thereby realizing the switching of the charging circuit under the appropriate filter capacitor 97 voltage. The control of the pulse power supply charging circuit by the current detection switching judgment circuit and the filter capacitor voltage detection circuit is "AND" logic, that is, only when the two circuits reach the set target, the pulse power supply charging circuit will be put into operation.

The fifth resistor 60, the sixth resistor 57 and the seventh resistor 58 divide the voltage across the filter capacitor 97. When the voltage divided by the fifth resistor 60 reaches the conduction voltage of the emitter junction of the third triode 61, the pulse power supply Only the secondary of the transformer 62 of the charging circuit can output current. In this way, we can control the third triode 61 to operate when the voltage across the filter capacitor 97 takes an appropriate value by properly selecting the resistance values of the fifth resistor 60, the sixth resistor 57, and the seventh resistor 58. conduction, thereby ensuring that under interference, only when the voltage across the filter capacitor 97 is higher than an appropriate threshold, it is possible to switch from the soft-start charging circuit to the three-phase bridge rectification series thyristor circuit.

The thirteenth resistor 88 and the fourteenth resistor 89 not only act as the current limiting resistors of the soft-start charging circuit, but also perform the task of detecting the charging current. The voltage dropped across the fourteenth resistor 89 charges the sixth capacitor 70 through the fifth diode 69 , so that the voltage across the sixth capacitor 70 is substantially equal to the voltage drop across the fourteenth resistor 89 . When the soft-start charging current is large, the voltage dropped on the thirteenth resistor 88 and the fourteenth resistor 89 is relatively high, and the voltage on the sixth capacitor 70 is also high. The transformer 62 is a step-down transformer, and the secondary voltage The effective value is 9 volts, and the peak voltage output through the first diode 63 is about 12 volts. Therefore, when the voltage on the sixth capacitor 70 is higher than 12 volts, the second diode 66 is always in a cut-off state, so that The first triode 64 is in an off state because the base current is zero, so it cannot charge the first capacitor 68 , so that the pulse generating circuit powered by the first capacitor 68 cannot work. When the voltage across the filter capacitor is higher than the set voltage value, when the soft-start charging current is so small that the voltage on the sixth capacitor 70 is lower than 12 volts, the second diode 66 starts to conduct, so that the second diode 66 starts to conduct. A transistor 64 is turned on to charge the first capacitor 68 . The ninth resistor 72 and the eleventh resistor 73 divide the voltage on the sixth capacitor 70, and the resistance values of the ninth resistor 72 and the eleventh resistor 73 are appropriately selected so that the voltage on the sixth capacitor 70 is greater than a certain appropriate value. The four triodes 74 are saturated and turned on, so that the second capacitor 78 cannot be charged, and the pulse generating circuit does not work. When the voltage across the sixth capacitor 70 is less than a certain threshold, the fourth transistor 74 is turned off, and the pulse generating circuit is put into operation.

The pulse generation circuit is a relaxation oscillation circuit with a unijunction transistor 79 as the core. When the voltage on the second capacitor 78 is lower than the voltage on the first capacitor 68 to exceed the emitter junction conduction voltage of the second triode 77, the first capacitor 68 passes through the first resistor 75, the third resistor 76 and the second triode. The emitter junction of the tube 77 charges the second capacitor 78, and also charges the fourth capacitor 82 through the collector of the second triode 77, and the resistance value of the eighth resistor 83 is selected to be large enough to ensure the discharge of the fourth capacitor 82 The speed is much slower than the charging speed, so the voltage on the fourth capacitor 82 can be quickly charged to the degree of only one saturation voltage drop lower than the emitter voltage of the second triode 77, and as long as the second triode 77 is conducting If it is on, the voltage on the second capacitor 78 is lower than the emitter voltage of the second triode 77 by an emitter junction conduction voltage. It can be seen that when the triode is turned on, the voltage on the fourth capacitor 82 is higher than that of the second capacitor 78 The voltage on the unijunction transistor 79 is in the cut-off state. When the voltage on the second capacitor 78 rises to the point where the voltage drop on the third resistor 76 is less than the turn-on voltage of the emitter junction of the second triode 77, the second triode 77 is turned off, the second capacitor 78 continues to be charged through the third resistor 76, and the fourth capacitor 82 is discharged through the eighth resistor 83 until the voltage on the fourth capacitor 82 is lower than the voltage on the second capacitor 78 to trigger the unijunction transistor 79 , when the unijunction transistor 79 is triggered and turned on, the second capacitor 78 and the fourth capacitor 82 are quickly discharged through the unijunction transistor 79, and a pulse current is generated through the twelfth resistor 84 to trigger the thyristor 96, when the unijunction transistor When 79 resumes the cut-off state, there is only a very low residual voltage on the second capacitor 78 and the fourth capacitor 82, so charging starts again, that is, the pulse generating circuit starts the pulse generation process of the next cycle, and the tenth resistor 80 and the fifth capacitor 81 acts as a filter to prevent the thyristor 96 from being triggered by the high-frequency interference voltage by mistake.

When the high-power switching power supply is powered on, the voltage of the filter capacitor 97 is zero, and the third triode 61 is not conducting. At this time, the soft-start charging current is relatively large, and the first triode 64 is not conducting, and the fourth and third triodes 61 are not conducting. The pole tube 74 is saturated and turned on, so neither the pulse power supply charging circuit nor the pulse generating circuit works. As the voltage of the filter capacitor 97 increases continuously and is higher than the set value of the voltage, the third transistor 61 is turned on. On the other hand, the soft-start charging current decreases continuously and is less than the current setting value, that is, the difference between the output voltage of the rectifier circuit and the voltage across the filter capacitor 97 reaches the setting value. At this time, the charging circuit of the pulse power supply is put into the running state, and starts to charge the first capacitor 68, and waits for the voltage across the first capacitor 68 to rise to an appropriate value, and the soft-start charging current is further reduced to make the voltage on the sixth capacitor 70 When the fourth triode 74 is cut off, the pulse generating circuit is put into operation, and the circuit switches from the soft-start charging state to the three-phase bridge rectification charging state. The current detection and switching judgment circuit and the filter capacitor voltage detection circuit constitute the double insurance of circuit safety. Once one of the circuits fails to work due to various reasons, the other circuit can work alone to protect the switching power supply from great impact.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. A soft start device for a high-power switching power supply, characterized in that it includes a soft start charging circuit, a three-phase bridge rectifier series thyristor circuit, a filter capacitor voltage detection circuit, a current detection switching judgment circuit, a pulse power supply charging circuit, and a pulse generating circuit And the filter capacitor, the soft start charging circuit is connected in parallel with the three-phase bridge rectification series thyristor circuit; the filter capacitor voltage detection circuit is connected with the pulse power supply charging circuit and the three-phase bridge rectification series thyristor circuit; The charging circuit, the pulse generating circuit, and the soft-start charging circuit are connected; the pulse power supply charging circuit is connected with the pulse generating circuit; the pulse generating circuit is respectively connected with the three-phase bridge rectification series thyristor circuit, and the soft-start charging circuit; the soft-start charging The circuit, the three-phase bridge rectification series thyristor circuit, the filter capacitor voltage detection circuit, the current detection switching judgment circuit, the pulse power supply charging circuit, and the pulse generating circuit are all connected to the filter capacitor; the soft start charging circuit, pulse power supply charging circuit, three The three-phase AC power supply is externally connected to the phase bridge rectification series thyristor circuit. 2. The soft start device of high-power switching power supply according to claim 1, characterized in that: said three-phase bridge rectification series thyristor circuit comprises an eighth diode, a ninth diode, a tenth diode , the eleventh diode, the twelfth diode, the thirteenth diode and a thyristor, the eighth diode, the ninth diode, the tenth diode, the tenth diode, Both the twelfth diode and the thirteenth diode are power diodes; the eighth diode is connected in series with the eleventh diode, the ninth diode is connected in series with the twelfth diode, and the twelfth pole The tube is connected in series with the thirteenth diode; the cathode of the eighth diode, the cathode of the ninth diode and the cathode of the tenth diode are connected to each other, and are all connected to the anode of the thyristor; the eleventh diode The anode of the anode, the anode of the twelfth diode and the anode of the thirteenth diode are connected to each other, and are all connected to the negative pole of the filter capacitor; the cathode of the thyristor is connected to the positive pole of the filter capacitor, and its gate is connected to the pulse generating circuit ; Between the anode of the eighth diode and the cathode of the eleventh diode, between the anode of the ninth diode and the cathode of the twelfth diode, between the anode of the tenth diode and the cathode of the twelfth diode The cathodes of the thirteen diodes are respectively connected to the three phase lines of the three-phase AC power supply through lead wires, and the cathodes of the eleventh diode, the cathode of the twelfth diode, and the thirteenth diode The cathodes of each are connected to the soft-start charging circuit. 3. The soft start device of high power switching power supply according to claim 2, characterized in that: said soft start charging circuit comprises a fourth diode, a sixth diode, a seventh diode, a thirteenth diode resistor and the fourteenth resistor, the fourth diode, the sixth diode and the seventh diode are all rectifier diodes; the thirteenth resistor is connected in series with the fourteenth resistor, and the other ends of the thirteenth resistor are respectively It is connected to the cathode of the fourth diode, the cathode of the sixth diode, and the cathode of the seventh diode, and the other end of the fourteenth resistor is respectively connected to the current detection switching judgment circuit, the positive pole of the filter capacitor, and the pulse generation circuit ; The anode of the fourth diode, the anode of the sixth diode, and the anode of the seventh diode are respectively connected with the three phase lines of the three-phase AC power supply, and are respectively connected with the tenth in the three-phase bridge rectification series thyristor circuit. The cathode of one diode, the cathode of the twelfth diode and the cathode of the thirteenth diode are connected. 4. The soft start device of high-power switching power supply according to claim 3, characterized in that: said current detection switching decision circuit comprises a fifth diode, a third diode, a fourth resistor, a sixth capacitor, The ninth resistor, the eleventh resistor and the fourth triode, the sixth capacitor is an electrolytic capacitor; the anode of the fifth diode is connected between the thirteenth resistor and the fourteenth resistor in the soft-start charging circuit , the cathode of the fifth diode is respectively connected to the anode of the third diode and the anode of the sixth capacitor; the anode of the third diode is connected to the anode of the sixth capacitor, and its cathode is respectively connected to one end of the fourth resistor, connected to the pulse power charging circuit; the other end of the fourth resistor is connected to the negative pole of the sixth capacitor and the pulse power charging circuit; one end of the ninth resistor is connected to the cathode of the fifth diode, the anode of the third diode, the The positive pole of the sixth capacitor is connected, and the other end is connected to the base of the eleventh resistor and the fourth transistor; one end of the eleventh resistor is connected to the base of the fourth transistor, and the other end is connected to the negative pole of the sixth capacitor connection; the emitter of the fourth transistor is connected to the negative pole of the sixth capacitor, its collector is connected to the pulse generating circuit, and the negative pole of the sixth capacitor is respectively connected to the positive pole of the filter capacitor and the fourteenth resistor in the soft-start charging circuit . 5. The soft start device of high-power switching power supply according to claim 4, characterized in that: said pulse power supply charging circuit comprises a transformer, a first diode, a first triode, a second resistor, a second two A pole tube and a first capacitor, the first capacitor is an electrolytic capacitor, the primary two ends of the transformer are respectively connected to the zero line and a phase line of the three-phase AC power supply, and one end of the secondary side is connected to the third third pole in the filter capacitor voltage detection circuit The collector of the tube is connected, the other end of the secondary is connected to the anode of the first diode, the cathode of the first diode is connected to the emitter of the first triode, the base of the first triode is connected to the second two The anode of the pole tube is connected, the cathode of the second diode is connected with the current detection switching judgment circuit; the collector of the first triode is connected with the positive pole of the first capacitor and the pulse generating circuit; the negative pole of the first capacitor is connected with the current detection switching circuit The anode of the decision circuit and the filter capacitor are connected; one end of the second resistor is connected between the cathode of the first diode and the emitter of the first triode, and the other end is connected between the base of the first triode and the first triode. between the anodes of the two diodes. 6. The soft start device of high-power switching power supply according to claim 5, characterized in that: said pulse generating circuit comprises a first resistor, a second triode, a unijunction transistor, a twelfth resistor, a third resistor , the second capacitor, the tenth resistor, the fifth capacitor, the fourth capacitor and the eighth resistor, one end of the first resistor is respectively connected with the pulse power supply charging circuit, and the other end is connected with the emitter of the second triode; the second three The collector of the transistor is connected to the gate of the unijunction transistor, the base of the second triode is connected to the anode of the unijunction transistor; the cathode of the unijunction transistor is connected to one end of the twelfth resistor, and the other end of the twelfth resistor One end is connected to the gate of the thyristor in the three-phase bridge rectification series thyristor circuit; one end of the third resistor is respectively connected to the first resistor and the emitter of the second triode, and the other end is respectively connected to the base of the second triode. One end of the second capacitor is connected to the anode of the unijunction transistor, and the other end is connected to the negative pole of the sixth capacitor in the current detection switching judgment circuit and the positive pole of the filter capacitor; One end of the ten resistors and the fifth capacitor is connected to the cathode of the unijunction transistor, and the other end is connected to the negative pole of the sixth capacitor and the positive pole of the filter capacitor in the current detection switching judgment circuit; the fourth capacitor is connected in parallel with the eighth resistor, and its One end is connected with the gate of the unijunction transistor and the collector of the second triode, and the other end is connected with the negative pole of the sixth capacitor in the current detection switching judgment circuit and the positive pole of the filter capacitor; the tenth resistor, the fifth The capacitor, the fourth capacitor and the eighth resistor are all connected to the soft-start charging circuit. 7. The soft start device of high-power switching power supply according to claim 6, characterized in that: one end of the first resistor is respectively connected to the positive pole of the first capacitor in the pulse power supply charging circuit and the collector of the first triode connected, and the other end is connected to the emitter of the second triode; one end of the third resistor is respectively connected to the first resistor and the emitter of the second triode, and the other end is respectively connected to the base of the second triode 1. The anode of the unijunction transistor is connected to the collector of the fourth triode in the current detection switching decision circuit. 8. The soft start device for a high-power switching power supply according to any one of claims 1 to 7, wherein the filter capacitor voltage detection circuit includes a third triode, a third capacitor, and a sixth capacitor connected in series in sequence resistor, the seventh resistor and the fifth resistor, the third capacitor is an electrolytic capacitor; the other end of the fifth resistor is connected to the positive pole of the filter capacitor, the positive pole of the third capacitor, and the emitter of the third triode, and the sixth resistor The other end of the filter capacitor is connected to the negative pole of the filter capacitor and the three-phase bridge rectification series thyristor circuit; the negative pole of the third capacitor is connected between the seventh resistor and the fifth resistor and connected to the base of the third triode; the third three The base of the transistor is connected between the seventh resistor and the fifth resistor, and the collector of the third triode is connected with one end of the transformer secondary in the pulse power supply charging circuit. 9. The soft start method of the high-power switching power supply realized by the device described in any one of claims 1 to 8, is characterized in that, comprises the steps: (1) The high-power switching power supply is powered on by connecting to the three-phase alternating current; (2) The soft start charging circuit charges the filter capacitor; (3) The current detection switching judgment circuit detects the current of the soft-start charging circuit. At the same time, the filter capacitor voltage detection circuit detects the voltage across the filter capacitor. If the current of the soft-start charging circuit and the voltage across the filter capacitor both meet conditions, the pulse power supply charging circuit works; (4) On the basis of step (3), the current detection switching judgment circuit detects the current of the soft-start charging circuit, if the current of the soft-start charging circuit is so small that the fourth triode in the current detection switching judgment circuit is cut off , the pulse generating circuit works; (5) The pulse generation circuit generates pulses, triggers the thyristors in the three-phase bridge rectification series thyristor circuit, switches to the three-phase bridge rectification series thyristor circuit to charge the filter capacitor, and completes the soft start of the high-power switching power supply. 10. The soft-start method of high-power switching power supply according to claim 9, characterized in that, the specific steps of charging the filter capacitor by the soft-start charging circuit in the step (2) include: three phase lines of three-phase alternating current The current respectively passes through the fourth diode, the sixth diode, the seventh diode in the soft-start charging circuit and the eleventh diode and the twelfth diode in the three-phase bridge rectification series thyristor circuit tube and the thirteenth diode constitute the output of the three-phase full-bridge rectifier circuit, and then charge the filter capacitor through the thirteenth resistor and the fourteenth resistor in turn; In the step (3), when the current of the soft-start charging circuit is less than the set value and the voltage at both ends of the filter capacitor is greater than the set value, the first triode in the pulse power supply charging circuit is turned on, so that the pulse power supply The charging circuit works; the three-phase alternating current supplies current to the transformer through its zero line and phase line, and the current passes through the first diode, the first triode, the second resistor, the second diode and the first capacitor respectively, and passes through the first A capacitor stores energy and supplies power to the pulse generating circuit; In the step (5), the specific steps of the pulse generation circuit triggering the thyristor in the three-phase bridge rectification series thyristor circuit include: the voltage on the sixth capacitor in the current detection switching judgment circuit decreases continuously with the charging current of the filter capacitor When it drops to the set value, the fourth triode turns from on to off, and the pulse generating circuit charges the second capacitor through the first resistor, the third resistor and the second triode, and at the same time, the pulse power supply charging circuit also Charge the fourth capacitor through the first resistor and the second transistor. When the voltage on the second capacitor rises to the voltage close to the voltage on the first capacitor in the pulse power supply charging circuit, the second transistor is turned off, so that the fourth The capacitor is discharged through the eighth resistor, and when the voltage on the fourth capacitor drops to a certain value, the unijunction transistor is triggered, a pulse voltage is formed on the tenth resistor and the fifth capacitor, and the three-phase bridge rectification is triggered through the twelfth resistor The thyristor in the thyristor circuit in series; after the thyristor is triggered, the eighth diode, the ninth diode, the tenth diode, the eleventh diode, the twelfth diode, and the thirteenth diode The three-phase full-bridge rectifier circuit composed of transistors charges the filter capacitor through the thyristor, thereby completing the switching from the soft-start charging circuit to the three-phase bridge rectifier series thyristor circuit.

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