The adjustable voltage output system based on STM32 and RT9214

Transcription

1 International Journal o Enineerin Inventions e-issn: , p-issn: olume 6, Issue [Feb. 07] PP: 8-3 The adjustable voltae output system based on STM3 and T94 Wu Jun, Wan Guolian, Xiao Zhitao (Tianjin Polytechnic University,Tianjin , hina) (Tianjin Key Laboratory o ptoelectronic Detection Technoloy and System, Tianjin , hina) Abstract:This paper puts orward a desin method o the system usin the embedded system control T94 to output power. This method avoids the restrictions o the T94 classic circuit usin potentiometer to adjust the output voltae, usin sotware control T94 voltae outputtin, more concise in the way o adjustion and more rich usae scenarios. This desin uses STM3 as core control I, T94 as power output core chip, usin the classic BUK circuit to output adjustable voltae. This paper introduces the hardware desin and sotware control rom the control circuit and the power output. And testin the system as a whole, the results show that the correctness o this desin, usin the embedded system can accurately control T94 output voltae, and accurate ormulas are deduced. Key words:stm3; The embedded system; T94; BUK I. INTDUTINS T94 is a typical special chip o buck converter (BUK) circuit. Accordin to T94 technical data, the output voltae can be adjusted rom to. when the maniication scale resistance o eedback loop is determined, it is not convenient to reulate the output voltae. Althouh the existin scheme can be used to adjust the potentiometer resistance to adjust the output voltae, but in the case o vibration, wron operation, or circuit board closed, potentiometer adjustment method will be limited. In the desin, to avoid the case, STM3 is used to control T94 output voltae. In this way, in T94 interation system, it is unrequired to adjust T94 voltae and reserve the external port. And also it may prevent the system damaes caused by the wron operation in the adjustin process o potentiometer. II. IUIT DESIGN We desined and commissioned the circuit whose output voltae is adjusted with T94. In T94 chip manual, duty may be adjusted rom 0% to 00%. It is calculated accordin to ormula (): Duty () The output voltae adjustment rane is 0~ v. In this desin, we control the output voltae o 3 v~0 throuh the STM3 voltae reulation.the core o T94 voltae reulation is to control the relationship between the eedback voltae and 0.8. The desin idea is to use the output pin o the STM3 and the T94 eedback voltae to control the Pin6 eedback voltae o the T94, and then control the output voltae by controllin the eedback voltae () STM3 entral control system In STM3 embedded central control system, the unction o STM3 chip may transmit the enablin sinal to T94 power output module throuh input/output pin. The output power is adjusted throuh Pulse Width Modulation () wave. The voltae sinal transmitted by utput voltae acquisition system is used in the comparison and the standard o power module reulation.in the desin, STM3F00BT6 chip is selected and used accordin to the simple requirements o control unction. The chip includes 48 pins, -bit synchronous AD collection and analo to diital converter (AD) collection channel and supports online simulation. Pae 8

2 Fiure STM3 minimum system Fiure shows the composition o STM3 minimum system. The system reulation uses Serial Wire Debu (SWD) mode. Accordin to the chip manual, connect Pin 37 and Pin 34 in STM 3 as per iure. STM 3 may be commissioned in SWD mode. () T94 oltae reulatin circuit In the desin process o T94 voltae reulatin circuit, we irstly analyze the classical circuit iven in chip data, and calculate the output voltae. The classical power output circuit o T94 is shown in iure. Fiure T94 utput circuit oltae reulation principle o T94: When the eedback pin receives the voltae FB 0.8, T94 widens the duty and increase the voltae. When FB 0.8, T94 narrows the duty and stabilize the voltae. In the reulation mode, accordin to the overlappin principle in circuit analysis, we derive the standard ormula o circuit output voltae : It is oranized rom ormula (): 0. 8 () 0.8 ( ) (3) Formula (3) is the calculation ormula o output voltae standard iven in T94 chip manual. The disadvantae o the circuit lines in reulatin the output voltae throuh chanin the proportion o two eedback resistance. It is inconvenient to use. We improve the circuit. The circuit is shown in iure 3. Fiure 3 The desin o STM3 controllin the output Where, c is the control voltae. When other parts o circuit are not chaned, accordin to the circuit overlappin principle, we may obtain that: 0. (4) 8 Pae 9

3 It is oranized: - ( ) 0. (5) 8 As shown in ormula (5), output voltae is not only determined by the proportion o and. It also relates to control voltae iven in STM3. At the same time, it is an inverse relation, namely when c is the maximum, the output voltae will be the minimum; when c is the minimum, the output voltae will be the maximum; Here, the output voltae o embedded central control system is 0~+3.3. The reulation amplitude o voltae is too low and it does not meet the requirements. It is too complex to reulate throuh the proportional relationship; thereore, we ampliy output o embedded central control system as voltae reulation c o T94. The circuit is shown in iure 4. Fiure 4 Ampliied STM3 amplitude modulation circuit The circuit uses interation computin ampliier T94. The input in positive end reers to voltae re and the neative end inputs voltae o embedded central control system. The output end connects the resistance about 5KΩ and achieves rail-rail output, makin it accurately output 0 voltae under low-voltae output. The expression o voltae at output end is calculated with node overlappin principle: It is oranized: - (6) re ( ) (7) re As shown in ormula 97), the key point in c voltae control is divided into two parts: one part is the ratio o and ; re is the ixed quantity o two systems, namely the parameter may not be adjusted when the system desin is completed; another part is, namely output waveorm o STM3. It is the procedure control variable and the voltae reulation may be outputted accordin to the system requirement. The chane in c amplitude may break the limitation o STM3 output 3.3 and desin to the required size throuh calculatin eedback loop proportion and reerrin to the voltae. In order to obtain the output voltae 0, ormula (7) is substituted into ormula (5). is t, it is oranized: - ( ( ) ) 0.8 ( ) (8) re is k, it is oranized rom ormula (): t ( k ( k ) ) 0.8 ( t ) (9) re tk 0.8 ( t ) t ( k ) ) (0) ( re The unction relationship between waveorm and T94 in embedded central control system may be obtained rom ormula (9). The relationship between and T94 output voltae may be calculated throuh ormula (0). As shown in ormula (0), the second hal o the ormula is the ixed constant o circuit desin. It may not be reulated once determined. The irst hal is variable, namely waveorm o embedded central control system. It may be reulated accordin to the actual requirements. Pae 30

4 . Experimental results In order to veriy the correctness and reliability o the desin, the circuit parameters are desined and the results are in areement with the calculated results. In the experiment, parameter t is set as 3.33,k is set as 0.55, re is 0.6. Substitute t, k and re into ormula (9): () pwm As shown in the above ormula, the desin relates to the quantity relationship between and T94 output voltae. The experimental results reer to iure 5: Fiure 5 utput waveorm o 30% o duty Fiure 6 utput waveorm o duty 50% o wave Fiure 7 Stepped output o waveorm ormin o circulation reulation When iure 5 shows wave duty is 30%, is. and T94 output voltae is 3.84 ; iure 6 shows when wave duty is 50%, is.64,t94 output is 5.76 ; substitutin the data into ormula (), we may see the accuracy o ormula. Fiure 7 is adjustin wave duty throuh cycle. T94 presents the waveorm o stepped output. As shown in the iure, the output voltae o T94 chanes accordin to the chanes in wave duty. The correctness o the desin idea is proved by the ormula calculation and experimental waveorm. The desin uses a output pin in the STM3 with the T94 eedback voltae usin the voltae divider principle, toether with the control o the pin6 T94 eedback voltae to accurately control the output voltae. III. SUMMAY AND PSPET The desin calculates the accurate relationship between waveorm output and T94 output voltae in the embedded central control system throuh chanin the eedback pin circuit in T94 classical circuit and applyin the basic knowlede o circuit, and proves the reliability o circuit desin throuh the experiment. The desin chanes the adjustin mode o T94 output voltae to the sotware method o composin waveorm with embedded central control system throuh chanin the hardware reulation Pae 3

5 mode o circuit parameters and lexibly applies T94 classical circuit and output characteristics, and extends the use scenario o T94. EFEENES []. Hu Xianjun, ircuit Analysis (edition II) [M]. Beijin: Hiher Education Press, 006 []. Wan Guan, hen Jiankui, Zhai Jie, Shi Minhui, Temperature acquisition scheme based on ampliier and temperature sensor [J]. Instrument Technique and Sensor, 04(): [3]. Li Don, Lu Honjuan: Analysis o Application ircuit in D speed control system circuit [J]. Electronic Desin Enineerin 0,0():8-83 [4]. Li Shuo, Don Yiyuan, Desin o overcurrent alarm device based on SM00B and LM34 [J]. Modern electronic technoloy 0,34(4): [5]. T94-5/ Synchronous Buck D-D ontroller[]. IHTEK,0 [6]. Ton Hua, Ton Jianzhon, Fault dianosis and maintenance o computer mainboard [J]. Silicon alley 009(3):3 Author:. Wu Jun,978, male, associate proessor and doctor.. Wan Guolian, 99, male, Master Deree. The second author is communication author, School o electronic and inormation enineerin, Tianjin University o Technoloy, No. 399, West o Binxi oad, Xiqin District, Tianjin ity ,TEL:38869, 3. Xiao Zhoutao, 97, male, pro Pae 3