CN110739842A - soft start method of digital current source - Google Patents
soft start method of digital current source Download PDFInfo
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- CN110739842A CN110739842A CN201911233752.1A CN201911233752A CN110739842A CN 110739842 A CN110739842 A CN 110739842A CN 201911233752 A CN201911233752 A CN 201911233752A CN 110739842 A CN110739842 A CN 110739842A
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- duty ratio
- current source
- soft start
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0012—Control circuits using digital or numerical techniques
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- Power Engineering (AREA)
- Circuit Arrangement For Electric Light Sources In General (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses a soft start method of digital current sources, which sets different current threshold values, duty ratio rise cycles and duty ratio rise step values at different stages of soft start, increases duty ratio rise step values for the maximum duty ratio of a power MOS in each rise cycle of the digital current source according to the set soft start duty ratio rise cycle value and the soft start duty ratio rise step value in the corresponding current threshold value range, improves the start strategy of the digital current source, adjusts the rise rate of the current and eliminates the hidden danger of current overshoot on the premise of not adding extra hardware circuits.
Description
Technical Field
The invention relates to a digital current source, in particular to a soft start method of digital current source.
Background
The digital current source has extensive applications in fields such as illumination LED drive, laser cutting, laser welding, for analog current source, digital current source conversion efficiency is high, and current regulation is convenient nimble, can advantage such as output operating condition directly perceived.
Due to the load characteristics of the LED and the laser, the output current rise rate of the digital current source is very high at the moment of output starting, and the output current value of the digital current source often exceeds a set value before a current closed-loop control loop intervenes, so that current overshoot is caused.
The current overshoot is extremely harmful, so that the service lives of loads such as an LED (light emitting diode), a laser and the like can be shortened, and the use cost is increased; and thirdly, the voltage spike of the drain-source electrode of the power MOS in the current source can be caused by the current overshoot, the power MOS can be seriously and directly broken down, and finally the current source body is damaged.
Disclosure of Invention
The invention aims to provide soft start methods of a digital current source, improve the start strategy of the digital current source, regulate the rise rate of current and eliminate the potential hazard of current overshoot on the premise of not adding an additional hardware circuit.
The technical scheme of the invention is as follows:
A soft start method of a digital current source, comprising:
s1, setting parameters of the digital current source, including maximum duty ratio limit, initial value of soft start duty ratio, and current threshold, duty ratio rising period and duty ratio rising step value of , second and third stages respectively set according to the characteristics of the load;
s2, at the moment when the digital current source is output and started, the power MOS starts PWM according to the initial value of the soft start duty ratio;
s3, when the actual output current of the digital current source is less than or equal to the current threshold value of the soft start stage , according to the set duty ratio rising period value N1 of the soft start stage and the duty ratio rising step value S1 of the soft start stage , every N1 microseconds of the digital current source are carried out, and the maximum duty ratio of the power MOS is increased by S1;
s4, when the actual output current of the digital current source is larger than the current threshold value of the soft start second stage and smaller than or equal to the current threshold value of the soft start second stage, according to the set duty ratio rising period value N2 of the soft start second stage and the duty ratio rising step value S2 of the soft start second stage, every N2 microseconds of the digital current source, the maximum duty ratio of the power MOS is increased by S2;
s5, when the actual output current is larger than the soft-start second-stage current threshold and smaller than or equal to the soft-start third-stage current threshold, according to the set soft-start third-stage duty ratio rising period value N3 and the soft-start third-stage duty ratio rising step value S3, every N3 microseconds of the digital current source increases the maximum duty ratio of the power MOS by S3;
and S6, when the actual output current is larger than the current threshold value of the soft start third stage, the digital current source sets the maximum duty ratio of the power MOS to be the maximum duty ratio limiting parameter value set in the step S1.
Preferably, after the parameter is set in step S1, the digital current source stores the set parameter in the EEPROM, and if the load characteristic is not changed, the soft start parameter does not need to be set.
Preferably, the digital current source parameters are set through an upper computer.
The invention has the advantages that:
1. the soft start method of the digital current source realizes the soft start of the digital current source and eliminates the hidden trouble of output current overshoot on the premise of not increasing an additional hardware circuit.
2. According to the soft start method of the digital current source, different soft start parameters can be set through the upper computer according to different load characteristics, different rising rates can be set in different current interval ranges, and the flexibility of a product is greatly improved.
Drawings
The invention is further described with reference to the following figures and examples:
FIG. 1 is a flow chart of a soft start method of a digital current source in an embodiment;
fig. 2 is a curve of the maximum duty cycle of the power MOS and the output current during the soft start of the digital current source in the embodiment.
Detailed Description
The soft start method of the digital current source of the embodiment, firstly, configures parameters of the soft start of the digital current source through an upper computer, and comprises the following steps:
(1) modifying a parameter 'maximum duty ratio limit', and setting the maximum duty ratio allowed by the digital current source to be 80%;
(2) setting the parameter 'soft start switch' to 1, and starting the soft start function;
(3) setting the initial value of the soft start duty ratio to be 5 percent;
(4) according to the characteristics of the load, current threshold values, duty ratio rising periods and duty ratio rising step values of the soft start stage , the second stage and the third stage are respectively set, and the current threshold values, the duty ratio rising periods and the duty ratio rising step values are shown in table 1.
Table 1 soft start current threshold, duty cycle rise period of three phases.
After the soft start parameters of the digital current source are set according to the values, the digital current source can store the parameters in the EEPROM, and if the load characteristics are not changed, the soft start parameters do not need to be set. The operation process of the soft start of the digital current source is shown in fig. 1:
(a) at the moment when the output of the digital current source is started, the maximum duty ratio of the power MOS is 5 percent;
(b) when the actual output current is less than or equal to 7 amperes, the maximum duty ratio of the power MOS is increased by 2% every 5 microseconds;
(c) when the actual output current is greater than 7 amperes and less than or equal to 12 amperes, the maximum duty ratio of the power MOS is increased by 3% every 4 microseconds;
(d) when the actual output current is greater than 12 amperes and less than or equal to 18 amperes, the maximum duty ratio of the power MOS is increased by 5% every 3 microseconds;
(e) when the actual output current is larger than 18 amperes, the maximum duty ratio of the power MOS is 80 percent;
(f) to this end, the digital current source completes soft start to achieve stable current output, and fig. 2 is a maximum duty cycle of the power MOS and an output current curve in the soft start process of the digital current source in this embodiment.
Different soft start parameters can be set in different current intervals, different current limits are realized, and finally the actual output current stably and linearly rises.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose of the embodiments is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All modifications made according to the spirit of the main technical scheme of the invention are covered in the protection scope of the invention.
Claims (3)
- The soft start method of the digital current source of the types 1 and , characterized by comprising:s1, setting parameters of the digital current source, including maximum duty ratio limit, initial value of soft start duty ratio, and current threshold, duty ratio rising period and duty ratio rising step value of , second and third stages respectively set according to the characteristics of the load;s2, at the moment when the digital current source is output and started, the power MOS starts PWM according to the initial value of the soft start duty ratio;s3, when the actual output current of the digital current source is less than or equal to the current threshold value of the soft start stage , according to the set duty ratio rising period value N1 of the soft start stage and the duty ratio rising step value S1 of the soft start stage , every N1 microseconds of the digital current source are carried out, and the maximum duty ratio of the power MOS is increased by S1;s4, when the actual output current of the digital current source is larger than the current threshold value of the soft start second stage and smaller than or equal to the current threshold value of the soft start second stage, according to the set duty ratio rising period value N2 of the soft start second stage and the duty ratio rising step value S2 of the soft start second stage, every N2 microseconds of the digital current source, the maximum duty ratio of the power MOS is increased by S2;s5, when the actual output current is larger than the soft-start second-stage current threshold and smaller than or equal to the soft-start third-stage current threshold, according to the set soft-start third-stage duty ratio rising period value N3 and the soft-start third-stage duty ratio rising step value S3, every N3 microseconds of the digital current source increases the maximum duty ratio of the power MOS by S3;and S6, when the actual output current is larger than the current threshold value of the soft start third stage, the digital current source sets the maximum duty ratio of the power MOS to be the maximum duty ratio limiting parameter value set in the step S1.
- 2. The method as claimed in claim 1, wherein after the step S1, the digital current source stores the set parameters in the EEPROM, and if the load characteristics are not changed, the soft start parameters are not required to be set.
- 3. The soft-start method of the digital current source according to claim 1 or 2, wherein the digital current source parameters are set by an upper computer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201911233752.1A CN110739842B (en) | 2019-12-05 | 2019-12-05 | Soft start method of digital current source |
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| CN201911233752.1A CN110739842B (en) | 2019-12-05 | 2019-12-05 | Soft start method of digital current source |
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| CN110739842A true CN110739842A (en) | 2020-01-31 |
| CN110739842B CN110739842B (en) | 2021-11-23 |
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2019
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| US20090001946A1 (en) * | 2006-12-14 | 2009-01-01 | Intersil Americas Inc. | System and method to calculate initial duty cycle |
| CN101217252A (en) * | 2008-01-04 | 2008-07-09 | 华中科技大学 | A soft start circuit for PDM DC-DC switching power supply |
| CN101503060A (en) * | 2009-01-23 | 2009-08-12 | 西安智源电气有限公司 | Heavy truck electric appliance load driving device based on PWM control |
| CN102280994A (en) * | 2010-06-11 | 2011-12-14 | 中国科学院上海微系统与信息技术研究所 | Soft start circuit and method making use of pulse frequency and pulse width modulation |
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| CN103368051A (en) * | 2013-07-12 | 2013-10-23 | 北京信息科技大学 | Semiconductor laser driving system used for fiber laser pump |
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| CN110739842B (en) | 2021-11-23 |
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