CN116660681A - Generating device for converting low-voltage direct current into 20kV high-voltage direct current - Google Patents
Generating device for converting low-voltage direct current into 20kV high-voltage direct current Download PDFInfo
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Abstract
The invention relates to the technical field of line fault investigation equipment, in particular to a generating device for converting low-voltage direct current into 20kV high-voltage direct current. The generating device is a full-load high-efficiency boost DC-DC converter designed based on a PWM/PFM modulation mode, and the system framework mainly comprises: a PWM/PFM control circuit, a current sampling circuit, an oscillator, a VDD selection circuit, a logic control circuit, a triangular wave signal and an enable signal; the main functional module of the generating device comprises: a soft start circuit; a reference voltage source; an error amplifier; PWM/PFM switching control circuit. The invention designs a high-precision power supply chip control technology and an electronic filtering voltage regulation technology, and a single 12V direct current storage battery is used, so that a 12V power supply can be boosted to 20kV direct current voltage, and the random regulation of 0-20kV voltage is realized; the whole weight of the portable electric power line is within 8KG, so that people can conveniently carry the portable electric power line out, carry-on load is reduced, and the line fault detection and fault finding efficiency is improved.
Description
Technical Field
The invention relates to the technical field of line fault investigation equipment, in particular to a generating device for converting low-voltage direct current into 20kV high-voltage direct current.
Background
During transportation of electric power, the transmission line is one of the core components, and once a problem occurs in the transmission line, a short circuit or the like occurs in the whole transmission circuit, which has serious consequences. In the long-distance transportation process, many transmission lines need to pass through mountain, geological structures and geological conditions are quite complex, personnel generally have difficulty in reaching the transmission lines directly, and the current fault place must be positioned quickly in a certain way, so that the transmission lines are convenient to send people to carry out timely rush repair.
If the mountain area of the red river power supply bureau is multiple mountains, the mountain area is dense in topography and the fault positioning device is not covered and installed on the mountain area, line faults often occur, the troubleshooting difficulty is high after the faults occur, and the consumed manpower and material resources are large. After the fault occurs, the fault can be checked only by manual line inspection, and no professional fault checking device exists.
Currently, the most widely used power management chips in industry are of three types: linear voltage regulators, switching power converters, and charge pumps. The linear voltage stabilizer has the advantages of simple structure, low noise, small ripple and higher response speed, and the low-dropout regulator is a popular research direction at present, so that the working efficiency of the linear voltage stabilizer can be remarkably improved. The switching power supply converter can realize both voltage boosting and voltage dropping, and can be divided into a voltage boosting type, a voltage dropping type and a voltage boosting type according to different topological structures. The switching power supply converter utilizes the energy storage characteristics of a capacitor and an inductor, and then the power tube switch is controlled through logic to obtain stable output voltage. The linear voltage stabilizer has the advantages of high conversion efficiency, high stability, small volume and the like, and is widely applied to replace linear voltage stabilizers in various fields. The charge pump utilizes the capacitor to store energy, and has smaller volume and lower cost.
However, these three types of power management chips still have the following limitations: the output voltage of the linear voltage stabilizer is necessarily lower than the input voltage, and only the voltage reduction requirement can be met; the charge pump has low conversion efficiency due to the limitation of a topological structure; the working efficiency of the switching power supply converter is reduced under high frequency, and the switching power supply converter is mainly influenced by switching loss, so that the loss generated by the system is required to be comprehensively considered during design; the design difficulty and the complexity of the digital switching power supply converter are higher, more subject fields are involved, and the development cost is high. In addition, most fault checking devices for power transmission lines are large in size and weight, and are inconvenient for on-site maintenance personnel to carry and use. In view of this, we propose a generator device for converting low voltage dc into 20kV high voltage dc.
Disclosure of Invention
The invention aims to provide a generating device for converting low-voltage direct current into 20kV high-voltage direct current so as to solve the problems in the prior art.
In order to solve the above technical problems, one of the purposes of the present invention is to provide a generating device for converting low voltage DC into 20kV high voltage DC, where the generating device is a full-load high-efficiency boost DC-DC converter designed based on PWM/PFM modulation mode, and the system frame mainly includes: a PWM/PFM control circuit, a current sampling circuit, an oscillator, a VDD selection circuit, a logic control circuit, a triangular wave signal and an enable signal;
the main functional module of the generating device comprises:
soft start circuit: the output voltage is slowly increased to the preset voltage through the soft start circuit, so that the work safety of components is protected, and the conditions of surge current and overshoot voltage in the circuit start stage are reduced;
reference voltage source: a depletion tube structure is adopted to provide a high-precision reference voltage which is not influenced by a voltage source and temperature;
an error amplifier: a low-power consumption single-stage amplifier design with a folding type cascode structure is adopted to meet the performance requirement of a chip;
PWM/PFM switching control circuit: by detecting the duty cycle of the PWM comparator output signal, a smoother switching between PWM and PFM modes is achieved.
As a further improvement of the technical scheme, the system framework of the generating device also comprises a PWM comparator;
the two ends of the PWM comparator are respectively input with a triangular wave signal and an output signal of the error amplifier; when the surge protection state is finished, the output signal of the surge protection circuit is at a low level;
the output signal of the PWM comparator is a switch control signal of the oscillator, if the output signal is in a skip period state, the output signal of the PWM comparator is in a low level state in one period, at the moment, the oscillator stops working, the energy loss is reduced, and the oscillator resumes working until the output signal of the PWM comparator is in a high level again.
As a further improvement of the technical scheme, the PWM/PFM control circuit comprises a PWM/PFM mode switching logic circuit, a zero-crossing comparison circuit, a peak current limiting circuit and an anti-ringing circuit.
As a further improvement of the technical scheme, the working principle of the soft start circuit is as follows:
when the boost DC-DC converter in the generating device starts to work after being electrified, the output voltage gradually rises from zero to a preset value, so that the feedback voltage is smaller in the starting stage, if the feedback voltage is input into the error amplifier together with the fixed reference voltage, the error amplifier can be caused to output too high, and finally the PWM comparator outputs a modulation signal with a large duty ratio, so that the NMOS power tube is excessively long in conduction time, the inductance current is continuously increased, and the generated surge current and the overshoot voltage cause the chip to be damaged; the soft start circuit limits the output of the error amplifier by generating a gradually increasing reference voltage to avoid excessive duty cycle signal.
As a further improvement of the technical scheme, the working principle of the reference voltage source is as follows:
to realize high efficiency of full load, the boost DC-DC converter in the generating device needs to have a circuit structure with lower power consumption as much as possible;
the traditional band gap reference circuit has a complex structure, an operational amplifier circuit and a starting circuit are needed, the performance of the operational amplifier directly influences the precision of the output reference voltage, and the consumed current is generally more than ten mu A, which is not beneficial to high-efficiency design;
the reference voltage source adopts a depletion reference, so that a circuit structure is simplified, an operational amplifier circuit and a starting circuit are not needed, the layout area is reduced, the cost is saved, and the static power consumption can be greatly reduced. Although the reference voltage source with the structure does not need a starting circuit, the circuit structure is simpler, and the extremely low static power consumption meets the design target of a high-efficiency system.
As a further improvement of the technical scheme, the working principle of the error amplifier is as follows:
NMOS load in the generating device adopts a low-voltage connection mode, so that the output voltage swing of the error amplifier is larger;
providing a proper bias voltage; the input end of the error amplifier is respectively a reference voltage and a feedback voltage which are gradually increased and provided by a reference voltage circuit, and the output voltage value is sampled in real time according to a certain preset proportion; amplifying the signal by using the difference value of the gradually-increased reference voltage and the feedback voltage as an output signal of the error amplifier;
when the output voltage drops, the feedback voltage signal follows the drop, the reference voltage which is gradually increased is larger than the feedback voltage, the output signal rises, the duty ratio is increased, and the output voltage is regulated to rise; when the output voltage rises, the feedback voltage signal rises along with the rising of the output voltage, the reference voltage which gradually rises is smaller than the feedback voltage, the output signal falls, the duty ratio is reduced, and the output voltage is regulated to fall back.
As a further improvement of the technical scheme, the working principle of the PWM/PFM switching control circuit is as follows:
detecting the duty cycle of the output signal of the PWM comparator; if the load current is increased from the light load, the duty ratio of the output signal of the PWM comparator is increased, and the PWM working mode is automatically switched to when the duty ratio is increased to a certain degree;
comparing the high level time of the output signal of the PWM comparator with the time required by the inductor current to reach the current limiting value, the signal with longer duration determines the conduction time of the NMOS power tube, so that the switching of the system between the PWM working mode and the PFM working mode is smoother.
The second object of the present invention is to provide an operation method of a generator for converting low voltage direct current into 20kV high voltage direct current, comprising the following steps:
s1, when an enabling signal end is at a high level, starting to work by a booster circuit;
s2, comparing the output voltage with the input voltage by a VDD selection circuit, wherein the output voltage and the input voltage are larger as the power supply voltage of each module in the circuit;
s3, before the voltage value of the output voltage rises to the input voltage, the surge protection circuit acts, at the moment, the feedback loop does not work, the power switch tube is closed, the freewheel tube is controlled by the direct charging circuit to be conducted, and the output capacitor is charged until the output voltage is equal to the input voltage;
s4, after the state in the step S3 is finished, the surge protection signal jumps, and each module starts to work normally and enters a closed-loop control stage;
s5, in the process that the output voltage slowly rises to a preset value, a soft start circuit is utilized to obtain a gently rising reference voltage, the difference mode value between the reference voltage and the feedback voltage is smaller, and overshoot of the output voltage is avoided when the duty ratio is too large in the stage;
s6, when the load current is smaller, the power supply works in a PFM mode, some periods are skipped and the current-sustaining tube is closed by the zero-crossing detection circuit; when the load current is large, the system works in a PWM mode, and the system efficiency is always kept at a high level through automatic switching of the PWM/PFM mode.
The third object of the present invention is to provide a system control device of a generator, which includes a processor, a memory, and a computer program stored in the memory and running on the processor, wherein the processor is configured to implement the step of converting the low-voltage dc into the 20kV high-voltage dc when executing the computer program, and a working method thereof.
A fourth object of the present invention is to provide a computer-readable storage medium storing a computer program which, when executed by a processor, implements the steps of the aforementioned generator for converting low-voltage direct current into 20kV high-voltage direct current and a method of operating the same.
Compared with the prior art, the invention has the beneficial effects that:
1. the low-voltage direct current is converted into 20kV high-voltage direct current, and the generation device can boost a 12V power supply to 20kV direct current voltage by using a single 12V direct current storage battery through a high-precision power supply chip control technology and an electronic filtering voltage regulation technology, and can realize random regulation of 0-20kV voltage;
2. the whole weight of the generating device for converting the low-voltage direct current into the 20kV high-voltage direct current is within 8KG, so that people can conveniently carry the generating device out, carry-on loads are reduced, and the line fault detection and fault finding efficiency is improved.
Drawings
FIG. 1 is a system frame diagram of an exemplary overall generating device of the present invention;
FIG. 2 is a block diagram of an exemplary soft start control circuit of the present invention;
FIG. 3 is a circuit block diagram of an exemplary depletion reference in the present invention;
FIG. 4 is a circuit diagram of an exemplary error amplifier of the present invention;
fig. 5 is a circuit diagram of an exemplary PWM/PFM switching control circuit of the present invention;
fig. 6 is a block diagram of an exemplary electronic computer platform device according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
As shown in fig. 1, the present embodiment provides a generating device for converting low-voltage direct current into 20kV high-voltage direct current, where the generating device is a full-load high-efficiency boost DC-DC converter designed based on PWM/PFM modulation mode, and the system framework mainly includes: a PWM/PFM control circuit, a current sampling circuit, an oscillator, a VDD selection circuit, a logic control circuit, a triangular wave signal and an enable signal; the system also comprises an error amplifier and a PWM comparator;
two ends of the PWM comparator are respectively input with a triangular wave signal V and an output signal of the error amplifier; when the surge protection state is finished, the output signal V of the surge protection circuit is in a low level;
the output signal V of the PWM comparator is a switching control signal of the oscillator, and if the output signal V of the PWM comparator is in a skip cycle state, the output signal V of the PWM comparator is low in one cycle, at this time, the oscillator stops working, and energy loss is reduced, until the output signal V of the PWM comparator is high again, and the oscillator resumes working, see fig. 5.
The PWM/PFM control circuit comprises a PWM/PFM mode switching logic circuit, a zero-crossing comparison circuit, a peak current limiting circuit and an anti-ringing circuit.
In fig. 1, the input voltage is the output voltage, the feedback voltage dividing resistors are all used, MN1 and the power switching tube are used, and MP1 is the continuous tube.
Specifically, when the enable signal terminal is at a high level, the booster circuit starts to operate; the output voltage and the input voltage are compared by a VDD selection circuit, and the output voltage and the input voltage are larger as the power supply voltage VDD of each module in the circuit; before the voltage value of the output voltage rises to the input voltage, the surge protection circuit acts, the feedback loop does not work at the moment, the power switch tube MN1 is closed, the freewheel tube MP1 is controlled to be conducted by the direct charging circuit, and the output capacitor is charged until the output voltage is equal to the input voltage; after the state is finished, the surge protection signal jumps, and each module starts to work normally and enters a closed-loop control stage; in the process that the output voltage slowly rises to a preset value, a soft start circuit is utilized to obtain a reference voltage which rises slowly, the difference module value between the reference voltage and the feedback voltage is smaller, and overshoot of the output voltage is avoided when the duty ratio is too large in the stage; when the load current is smaller, the load current works in the PFM mode, and some periods are skipped to be not operated, and at the moment, the zero-crossing detection circuit closes the shunt tube MP1; when the load current is large, the system works in a PWM mode, and the system efficiency is always kept at a high level through automatic switching of the PWM/PFM mode.
In this embodiment, the main functional modules of the generating device include:
1. soft start circuit: the output voltage is slowly increased to the preset voltage through the soft start circuit, so that the work safety of components is protected, and the conditions of surge current and overshoot voltage in the circuit start stage are reduced;
when the boost DC-DC converter in the generating device starts to work after being electrified, the output voltage gradually rises from zero to a preset value, so that the feedback voltage is smaller in the starting stage, if the feedback voltage is input into the error amplifier together with the fixed reference voltage, the error amplifier can be caused to output too high, and finally the PWM comparator outputs a modulation signal with a large duty ratio, so that the NMOS power tube is excessively long in conduction time, the inductance current is continuously increased, and the generated surge current and the overshoot voltage cause the chip to be damaged; to avoid the above-mentioned situation, the present invention designs a soft start circuit by generating a gradually rising reference voltage V r Limiting the output of the error amplifier to avoid the overlarge duty cycle signal;
the structure of the soft start control circuit is shown in FIG. 2, M1 and M2 are power switch tubes, M3, M4 and M5 are depletion tubes, GND is ground potential, C1 is filter capacitor, R1 is load resistor and bias voltage, VDD is supply voltage, V ru Is a surge protection signal.
2. Reference voltage source: a depletion tube structure is adopted to provide a high-precision reference voltage which is not influenced by a voltage source and temperature; although the reference voltage source with the structure does not need a starting circuit, the circuit structure is simpler, and the extremely low static power consumption meets the design target of a high-efficiency system;
to realize high efficiency of full load, the boost DC-DC converter in the generating device needs to have a circuit structure with lower power consumption as much as possible;
the traditional band gap reference circuit has a complex structure, an operational amplifier circuit and a starting circuit are needed, the performance of the operational amplifier directly influences the precision of the output reference voltage, and the consumed current is generally more than ten mu A, which is not beneficial to high-efficiency design;
the reference voltage source adopts the depletion reference, so that the circuit structure is simplified, an operational amplifier circuit and a starting circuit are not needed, the layout area is reduced, the cost is saved, and the static power consumption can be greatly reduced;
the circuit structure diagram of the depletion reference is shown in fig. 3, M7 and M8 are both switching tubes, M9 is an enhancement tube, a signal EN is an enable control signal, en_n is an inversion control signal thereof, and when EN is at a high level, the circuit normally works, and at this time, the M1 tube is in an off state, and the switching tubes M6 and M10 tube are in an on state; m4, M5 and M11 are depletion, although their threshold voltages are negative; the grid electrode of the M5 tube is directly connected with the ground, and when the M6 tube is opened, the grid source voltage is equal to zero, so that constant branch current is generated; although the existence of M4 can inhibit the channel length modulation effect, the influence of VDD change on the current of the M5 tube is reduced; the current of the branch where the M5 pipe is located is copied to the branch where the M9 is located through a current mirror, and then is converted into the grid voltage of the M9 through I-V, namely a reference voltage; m12 is a switch tube, controlled by a soft start signal, generating a gradually rising reference voltage V r 。
3. An error amplifier: a low-power consumption single-stage amplifier design with a folding type cascode structure is adopted to meet the performance requirement of a chip;
the error amplifier is one of the core modules of the DC-DC converter designed by the invention, and the performance of the error amplifier can directly influence the accuracy of output voltage and the response speed of the system; the multistage amplifier has higher gain, but the quiescent current is larger, which is not beneficial to compensation; for the DC-DC converter designed by the invention, the single-stage amplifier meets the design requirement of low power consumption, and the gain of the folded cascode structure is larger, so that the performance requirement of a chip can be met.
Different from the traditional folding type cascode structure, the NMOS load in the generating device designed by the invention adopts a low-voltage connection mode, so that the output voltage swing of the error amplifier is larger;
the error amplifier circuit diagram is shown in fig. 4, and in fig. 4, the appropriate bias voltages are provided; the input ends of the error amplifier are respectively the gradually-rising reference voltages V provided by the reference voltage circuit r And feedback voltage, sampling the output voltage value in real time according to a specific proportion; at a gradually rising reference voltage V r And vice versaThe difference amplification signal of the feed voltage is used as an output signal of the error amplifier;
when the output voltage drops, the feedback voltage signal follows the drop, at which time the reference voltage V gradually rises r The feedback voltage is greater than the output signal, the duty ratio is increased, and the output voltage is regulated to rise; when the output voltage rises, the feedback voltage signal follows the rising reference voltage V r And the feedback voltage is less than the feedback voltage, the output signal is reduced, the duty ratio is reduced, and the output voltage is regulated to fall back.
4. PWM/PFM switching control circuit: by detecting the duty cycle of the output signal V of the PWM comparator, smoother switching between PWM and PFM modes is realized;
detecting the duty cycle of the output signal V of the PWM comparator; if the load current is increased from light load, the duty ratio of the V signal is increased, and the PWM working mode is automatically switched to when the duty ratio is increased to a certain degree; comparing the 'hard' switching of the detection current, the detection duty cycle can make PWM and PFM mode switching smoother;
comparing the high level time of the output signal of the PWM comparator with the time required by the inductor current to reach the current limiting value, and determining the on-time of the NMOS power tube by the signal with longer duration so as to enable the switching of the system between two working modes of PWM and PFM to be smoother; the PWM/PFM switching control circuit diagram is shown in fig. 5.
In addition, in one period, it is assumed that the output vhigh level time of the PWM comparator is t1, and the time for the inductor current to reach the current limit point is t2. When the converter is in light load, t1 is smaller than t2 in the PFM mode, the signal V turns on the NMOS power tube, and after reaching the peak current limiting point, the NMOS power tube is turned off by the signal V, and the PMOS power tube is turned on to enter the follow current stage.
The PWM/PFM switching control circuit designed by the invention takes an RS trigger as a key logic circuit, and the specific working principle is as follows: when in light load, the output of the error amplifier is lower, the time for outputting the high level of the V signal is very short, the V signal is input into the S end of the RS trigger, the initial state of the V signal is low level, the Q end is kept high level, and the NOR1 outputs a low level signal. Osc_n is the inverse of the oscillator signal OSC, which is low at this time, and the output signal control_n of NOR2 is high at this time, which turns on the NMOS power transistor. And when the inductor current reaches the current limiting point, the V signal becomes high level, the RS trigger is reset, the Q end is low level, V is low level at the moment, the control_N is low level, and the NMOS power tube is turned off at the moment.
When the load is increased, the output signal VE of the error amplifier increases, and the vhigh level time t1 increases. When t1 is greater than t2, the on and off of the NMOS power tube is controlled by the V signal and the OSC signal, and is not influenced by the V signal any more, namely, the converter enters a PWM working mode. In this state, the specific working principle of the PWM/PFM switching control circuit is as follows: the V signal is input into the S end of the RS trigger, the Q end outputs high level, and the NOR1 outputs low level. When the V signal is changed to high level, Q is changed to low level, at the moment, the V signal is still high level, the NOR1 outputs low level, and the NMOS power tube is kept on and is not turned off until the V signal is changed to low level.
In addition, the signal is input into the RS trigger and output into the judgment signal V of PWM and PFM modes [ . If the signal is V [ High level, the PWM mode is operated, and if low level, the PFM mode is operated. Thereby improving the accuracy of detecting the fault range under different conditions.
In addition, according to the characteristic of 35kV cable insulation in the red river region, the device disclosed by the invention adopts a direct current boosting technology, based on a voltage doubling principle, a 12V power supply can be boosted to 20kV direct current voltage through a single 12V direct current storage battery, and the voltage can be regulated at will by a high-precision power supply chip control technology and an electronic filtering voltage regulation technology. In addition, the weight of the device can be reduced to be within 8KG, and the device is convenient for field personnel to carry and use.
The embodiment also provides an operation method of the generating device for converting low-voltage direct current into 20kV high-voltage direct current, which comprises the following steps:
s1, when an enabling signal end is at a high level, starting to work by a booster circuit;
s2, comparing the output voltage with the input voltage by a VDD selection circuit, wherein the output voltage and the input voltage are larger as the power supply voltage VDD of each module in the circuit;
s3, before the voltage value of the output voltage rises to the input voltage, the surge protection circuit acts, at the moment, the feedback loop does not work, the power switch tube MN1 is closed, the freewheel tube MP1 is controlled to be conducted by the direct charging circuit, and the output capacitor is charged until the output voltage is equal to the input voltage;
s4, after the state in the step S3 is finished, the surge protection signal jumps, and each module starts to work normally and enters a closed-loop control stage;
s5, in the process that the output voltage slowly rises to a preset value, a soft start circuit is utilized to obtain a gently rising reference voltage, the difference mode value between the reference voltage and the feedback voltage is smaller, and overshoot of the output voltage is avoided when the duty ratio is too large in the stage;
s6, when the load current is smaller, the load current works in a PFM mode, some periods are skipped and the shunt tube MP1 is closed by the zero-crossing detection circuit; when the load current is large, the system works in a PWM mode, and the system efficiency is always kept at a high level through automatic switching of the PWM/PFM mode.
As shown in fig. 6, the present embodiment also provides a system control device of a generating device, which includes a processor, a memory, and a computer program stored in the memory and running on the processor.
The processor comprises one or more than one processing core, the processor is connected with the memory through a bus, the memory is used for storing program instructions, and the processor realizes the steps of the generating device for converting the low-voltage direct current into the 20kV high-voltage direct current and the operation method thereof when executing the program instructions in the memory.
Alternatively, the memory may be implemented by any type or combination of volatile or nonvolatile memory devices such as Static Random Access Memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic or optical disk.
In addition, the invention also provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program is executed by a processor to realize the steps of the generating device for converting the low-voltage direct current into the 20kV high-voltage direct current and the operation method thereof.
Optionally, the present invention also provides a computer program product comprising instructions which, when run on a computer, cause the computer to perform the steps of the generating device and the operating method of the generating device for converting low voltage direct current into 20kV high voltage direct current in the above aspects.
It will be appreciated by those of ordinary skill in the art that the processes for implementing all or part of the steps of the above embodiments may be implemented by hardware, or may be implemented by a program for instructing the relevant hardware, and the program may be stored in a computer readable storage medium, where the above storage medium may be a read-only memory, a magnetic disk or optical disk, etc.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, and that the above-described embodiments and descriptions are only preferred embodiments of the present invention, and are not intended to limit the invention, and that various changes and modifications may be made therein without departing from the spirit and scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (7)
1. The utility model provides a generating device of low voltage direct current conversion to 20kV high voltage direct current which characterized in that: the generating device is a full-load high-efficiency boost DC-DC converter designed based on a PWM/PFM modulation mode, and the system framework mainly comprises: a PWM/PFM control circuit, a current sampling circuit, an oscillator, a VDD selection circuit, a logic control circuit, a triangular wave signal and an enable signal;
the main functional module of the generating device comprises:
soft start circuit: the output voltage is slowly increased to the preset voltage through the soft start circuit, so that the work safety of components is protected, and the conditions of surge current and overshoot voltage in the circuit start stage are reduced;
reference voltage source: a depletion tube structure is adopted to provide a high-precision reference voltage which is not influenced by a voltage source and temperature;
an error amplifier: a low-power consumption single-stage amplifier design with a folding type cascode structure is adopted to meet the performance requirement of a chip;
PWM/PFM switching control circuit: by detecting the duty cycle of the output signal of the PWM comparator, smoother switching between PWM and PFM modes is realized;
the operation method of the generating device comprises the following steps:
s1, when an enabling signal end is at a high level, starting to work by a booster circuit;
s2, comparing the output voltage with the input voltage by a VDD selection circuit, wherein the output voltage and the input voltage are larger as the power supply voltage of each module in the circuit;
s3, before the voltage value of the output voltage rises to the input voltage, the surge protection circuit acts, at the moment, the feedback loop does not work, the power switch tube is closed, the freewheel tube is controlled by the direct charging circuit to be conducted, and the output capacitor is charged until the output voltage is equal to the input voltage;
s4, after the state in the step S3 is finished, the surge protection signal jumps, and each module starts to work normally and enters a closed-loop control stage;
s5, in the process that the output voltage slowly rises to a preset value, a soft start circuit is utilized to obtain a gently rising reference voltage, the difference mode value between the reference voltage and the feedback voltage is smaller, and overshoot of the output voltage is avoided when the duty ratio is too large in the stage;
s6, when the load current is smaller, the power supply works in a PFM mode, some periods are skipped and the current-sustaining tube is closed by the zero-crossing detection circuit; when the load current is large, the system works in a PWM mode, and the system efficiency is always kept at a high level through automatic switching of the PWM/PFM mode.
2. The generator for converting low voltage dc into 20kV high voltage dc according to claim 1, wherein: the system framework of the generating device further comprises a PWM comparator;
the two ends of the PWM comparator are respectively input with a triangular wave signal and an output signal of the error amplifier; when the surge protection state is finished, the output signal of the surge protection circuit is at a low level;
the output signal of the PWM comparator is a switch control signal of the oscillator, if the output signal is in a skip period state, the output signal of the PWM comparator is in a low level state in one period, at the moment, the oscillator stops working, the energy loss is reduced, and the oscillator resumes working until the output signal of the PWM comparator is in a high level again.
3. The generator for converting low voltage dc into 20kV high voltage dc according to claim 1, wherein: the PWM/PFM control circuit comprises a PWM/PFM mode switching logic circuit, a zero-crossing comparison circuit, a peak current limiting circuit and an anti-ringing circuit.
4. The generator for converting low voltage dc into 20kV high voltage dc according to claim 1, wherein: the working principle of the soft start circuit is as follows:
when the boost DC-DC converter in the generating device starts to work after being electrified, the output voltage gradually rises from zero to a preset value, so that the feedback voltage is smaller in the starting stage, if the feedback voltage is input into the error amplifier together with the fixed reference voltage, the error amplifier can be caused to output too high, and finally the PWM comparator outputs a modulation signal with a large duty ratio, so that the NMOS power tube is excessively long in conduction time, the inductance current is continuously increased, and the generated surge current and the overshoot voltage cause the chip to be damaged; the soft start circuit limits the output of the error amplifier by generating a gradually increasing reference voltage to avoid excessive duty cycle signal.
5. The generator for converting low voltage dc into 20kV high voltage dc according to claim 1, wherein: the working principle of the reference voltage source is as follows:
to realize high efficiency of full load, the boost DC-DC converter in the generating device needs to have a circuit structure with lower power consumption as much as possible;
the traditional band gap reference circuit has a complex structure, an operational amplifier circuit and a starting circuit are needed, the performance of the operational amplifier directly influences the precision of the output reference voltage, and the consumed current is generally more than ten mu A, which is not beneficial to high-efficiency design;
the reference voltage source adopts a depletion reference, so that a circuit structure is simplified, an operational amplifier circuit and a starting circuit are not needed, the layout area is reduced, the cost is saved, and the static power consumption can be greatly reduced.
6. The generator for converting low voltage dc into 20kV high voltage dc according to claim 1, wherein: the working principle of the error amplifier is as follows:
NMOS load in the generating device adopts a low-voltage connection mode, so that the output voltage swing of the error amplifier is larger;
providing a proper bias voltage; the input end of the error amplifier is respectively a reference voltage and a feedback voltage which are gradually increased and provided by a reference voltage circuit, and the output voltage value is sampled in real time according to a certain preset proportion; amplifying the signal by using the difference value of the gradually-increased reference voltage and the feedback voltage as an output signal of the error amplifier;
when the output voltage drops, the feedback voltage signal follows the drop, the reference voltage which is gradually increased is larger than the feedback voltage, the output signal rises, the duty ratio is increased, and the output voltage is regulated to rise; when the output voltage rises, the feedback voltage signal rises along with the rising of the output voltage, the reference voltage which gradually rises is smaller than the feedback voltage, the output signal falls, the duty ratio is reduced, and the output voltage is regulated to fall back.
7. The generator for converting low voltage dc into 20kV high voltage dc according to claim 1, wherein: the working principle of the PWM/PFM switching control circuit is as follows:
detecting the duty cycle of the output signal of the PWM comparator; if the load current is increased from the light load, the duty ratio of the output signal of the PWM comparator is increased, and the PWM working mode is automatically switched to when the duty ratio is increased to a certain degree;
comparing the high level time of the output signal of the PWM comparator with the time required by the inductor current to reach the current limiting value, the signal with longer duration determines the conduction time of the NMOS power tube, so that the switching of the system between the PWM working mode and the PFM working mode is smoother.
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| CN202310647103.6A CN116660681A (en) | 2023-06-02 | 2023-06-02 | Generating device for converting low-voltage direct current into 20kV high-voltage direct current |
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| CN202310647103.6A CN116660681A (en) | 2023-06-02 | 2023-06-02 | Generating device for converting low-voltage direct current into 20kV high-voltage direct current |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117544150A (en) * | 2024-01-09 | 2024-02-09 | 杰华特微电子股份有限公司 | High-side sampling circuit and power supply system |
| CN117914147A (en) * | 2024-03-19 | 2024-04-19 | 芯北电子科技(南京)有限公司 | CMCOT architecture-based PFM control method |
-
2023
- 2023-06-02 CN CN202310647103.6A patent/CN116660681A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117544150A (en) * | 2024-01-09 | 2024-02-09 | 杰华特微电子股份有限公司 | High-side sampling circuit and power supply system |
| CN117544150B (en) * | 2024-01-09 | 2024-04-19 | 杰华特微电子股份有限公司 | High-side sampling circuit and power supply system |
| CN117914147A (en) * | 2024-03-19 | 2024-04-19 | 芯北电子科技(南京)有限公司 | CMCOT architecture-based PFM control method |
| CN117914147B (en) * | 2024-03-19 | 2024-06-04 | 芯北电子科技(南京)有限公司 | CMCOT architecture-based PFM control method |
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