從最基本的說起吧，DC-DC的變換電路有很多種，線性電源、開關(guān)電源、電荷泵，線性電源大家比較熟悉的應(yīng)該就是78XX系列的芯片了，電荷泵主要用在小電流的應(yīng)用中，我們也不加討論。主要講講開關(guān)電源，我呢也是一個(gè)先學(xué)先賣的人，就對(duì)照資料啥的隨便介紹下拉，權(quán)當(dāng)是開源本設(shè)計(jì)前的一點(diǎn)準(zhǔn)備工作。
開關(guān)穩(wěn)壓器的工作原理，就是通過控制電路來控制開關(guān)器件的通斷，配合負(fù)反饋完成穩(wěn)壓，跟線性穩(wěn)壓比起來，具有效率高體積小的特點(diǎn)，但是輸出沒有線性電源穩(wěn)定。開關(guān)電源的基本結(jié)構(gòu)有很多種，包括BUCK、BOOST、BUCK-BOOST、CUK等非隔離式的DCDC變換器，也有Flyback、LLC等隔離式的DCDC變換器。開源的這個(gè)設(shè)計(jì)，是以buck拓?fù)錇楹诵模浜螰334的高級(jí)定時(shí)器的PWM、PI算法，實(shí)現(xiàn)的一個(gè)很簡(jiǎn)單的閉環(huán)控制，設(shè)計(jì)輸入電壓60V時(shí)，輸出電壓可調(diào)，輸出電流最大5A，輸出最大功率在200W左右。
這是基本的原理框圖
系統(tǒng)框圖如上，首先說明我這款電壓是從HP電源的基礎(chǔ)上增加人機(jī)界面和改善柵極驅(qū)動(dòng)做的，借這個(gè)機(jī)會(huì)分享下自己的心得。
采用同步BUCK，就是采用導(dǎo)通電阻特別低的mosfet來代替續(xù)流二極管，以此來提高整個(gè)拓?fù)涞墓ぷ餍?。基本圖如下：
圖中采用了無電解電容設(shè)計(jì)，這樣雖然紋波可能會(huì)大一點(diǎn)，但是響應(yīng)的體積卻小了很多，實(shí)際測(cè)試中，紋波在100MV以下。電感和電容的取值有響應(yīng)公式可以推到，這里不多贅述，直接給大家提供一個(gè)小工具，輸入?yún)?shù)就可以計(jì)算出結(jié)果的小工具：在文章最后配套資料
下面談一談程序的設(shè)計(jì)思路，因?yàn)檫@款設(shè)計(jì)為了盡可能減少體積，因此使用了較大頻率的PWM波，取值為250k，所采用的主控stm32f334是意法半導(dǎo)體專為數(shù)控電源所設(shè)計(jì)的一款MCU。STM32F334xx微控制器具有高分辨率定時(shí)器（HRTIM）外設(shè)，可產(chǎn)生多達(dá)10個(gè)信號(hào)，能夠處理用于控制、同步或保護(hù)的各種不同輸入信號(hào)。其模塊化架構(gòu)允許對(duì)大部分轉(zhuǎn)換拓?fù)浜投嗖⒙?lián)轉(zhuǎn)換器進(jìn)行處理，并可在運(yùn)行中重新配置它們。
在如上所示的拓?fù)洚?dāng)中，包括輸出電壓讀數(shù)和過流保護(hù)（利用FAULT輸入），使在電流超出可編程閾值時(shí)關(guān)閉轉(zhuǎn)換器。為簡(jiǎn)單起見，此處不討論電流傳感器和調(diào)整電路；預(yù)期的FAULT反饋（在FLT1輸入上）為數(shù)字信號(hào)（在PA12輸入上）。
HRTIM工作于連續(xù)模式，PWM信號(hào)定義如下：
• TA1：在 TA Period 置位，在 TA CMP2 復(fù)位
• TA2：利用死區(qū)時(shí)間發(fā)生器，與 TA1 互補(bǔ) （相同的上升沿和下降沿死區(qū)時(shí)間）
需要注意的是，有關(guān)AD采樣的觸發(fā)時(shí)機(jī)選擇是一個(gè)很關(guān)鍵的點(diǎn)，如下圖所示，對(duì)于特定占空比的PWM波，在其中央觸發(fā)AD工作，這樣可以避免紋波的影響。
由此，通過AD采樣的輸出電壓與設(shè)定的電壓一起，配合PI調(diào)節(jié)占空比，即完成了閉環(huán)反饋過程，通過對(duì)輸出電壓電流的編程，即完成電池充電程序的編寫。
這里給出配置的代碼和PI的代碼。
/***************************************************************************
#define PWM_PERIOD = 144000000*32/switchfrequency
#define DT_RISING = risingtime*switchfrequency*PWM_PERIOD
#define DT_FALLING = fallingtime*switchfrequency*PWM_PERIOD
***************************************************************************/
/**
* [url=home.php?mod=space&uid=159083]@brief[/url] 用于配置HRTIM_A的輸出，關(guān)閉deadtime時(shí)，為單輸出，開啟deadtime時(shí)，為雙輸出。
* @param 死區(qū)使能，配套AD采樣使能，錯(cuò)誤使能，中斷使能，初始頻率，初始占空比（HO），中斷頻率，上升死區(qū)時(shí)間（單位納秒），下降死區(qū)時(shí)間
* @retval None
*/
void MY_BSP_Init_HRTIM_A(BOOLEAN deadtime,BOOLEAN adenable,BOOLEAN faultenable,BOOLEAN interrupt,uint32_t Initial_Fre,uint8_t Initial_Duty,uint8_t n_ISR,uint8_t risingtime,uint8_t fallingtime)
{
HRTIM_TimeBaseCfgTypeDef timebase_config;
HRTIM_TimerCfgTypeDef timer_config;
HRTIM_OutputCfgTypeDef output_config_TA;
HRTIM_CompareCfgTypeDef compare_config;
/* ----------------------------*/
/* HRTIM Global initialization */
/* ----------------------------*/
/* Initialize the hrtim structure (minimal configuration) */
hhrtimA.Instance = HRTIM1;
hhrtimA.Init.HRTIMInterruptResquests = HRTIM_IT_NONE;
hhrtimA.Init.SyncOptions = HRTIM_SYNCOPTION_NONE;
/* Initialize HRTIM */
HAL_HRTIM_Init(&hhrtimA);
/* HRTIM DLL calibration: periodic calibration, set period to 14祍 */
HAL_HRTIM_DLLCalibrationStart(&hhrtimA, HRTIM_CALIBRATIONRATE_14);
/* Wait calibration completion*/
if (HAL_HRTIM_PollForDLLCalibration(&hhrtimA, 100) != HAL_OK)
{
Error_Handler(); // if DLL or clock is not correctly set
}
/* --------------------------------------------------- */
/* TIMERA initialization: timer mode and PWM frequency */
/* --------------------------------------------------- */
timebase_config.Period = 4608000000/Initial_Fre; /* 400kHz switching frequency */
timebase_config.RepetitionCounter = n_ISR - 1; /* n ISR every 128 PWM periods */
timebase_config.PrescalerRatio = HRTIM_PRESCALERRATIO_MUL32;
timebase_config.Mode = HRTIM_MODE_CONTINUOUS;
HAL_HRTIM_TimeBaseConfig(&hhrtimA, HRTIM_TIMERINDEX_TIMER_A, &timebase_config);
/* --------------------------------------------------------------------- */
/* TIMERA global configuration: cnt reset, sync, update, fault, burst... */
/* timer running in continuous mode, with deadtime enabled */
/* --------------------------------------------------------------------- */
timer_config.DMARequests = HRTIM_TIM_DMA_NONE;
timer_config.DMASrcAddress = 0x0;
timer_config.DMADstAddress = 0x0;
timer_config.DMASize = 0x0;
timer_config.HalfModeEnable = HRTIM_HALFMODE_DISABLED;
timer_config.StartOnSync = HRTIM_SYNCSTART_DISABLED;
timer_config.ResetOnSync = HRTIM_SYNCRESET_DISABLED;
timer_config.DACSynchro = HRTIM_DACSYNC_NONE;
timer_config.PreloadEnable = HRTIM_PRELOAD_ENABLED;
timer_config.UpdateGating = HRTIM_UPDATEGATING_INDEPENDENT;
timer_config.BurstMode = HRTIM_TIMERBURSTMODE_MAINTAINCLOCK;
timer_config.RepetitionUpdate = HRTIM_UPDATEONREPETITION_ENABLED;
timer_config.ResetUpdate = HRTIM_TIMUPDATEONRESET_DISABLED;
if(interrupt == TRUE)
{
timer_config.InterruptRequests = HRTIM_TIM_IT_REP;
}
else
timer_config.InterruptRequests = HRTIM_TIM_IT_NONE;
timer_config.PushPull = HRTIM_TIMPUSHPULLMODE_DISABLED;
if(faultenable == TRUE)
timer_config.FaultEnable = HRTIM_TIMFAULTENABLE_FAULT1;
else
timer_config.FaultEnable = HRTIM_TIMFAULTENABLE_NONE;
timer_config.FaultLock = HRTIM_TIMFAULTLOCK_READWRITE;
timer_config.DeadTimeInsertion = HRTIM_TIMDEADTIMEINSERTION_ENABLED;
timer_config.DelayedProtectionMode = HRTIM_TIMER_A_B_C_DELAYEDPROTECTION_DISABLED;
timer_config.UpdateTrigger= HRTIM_TIMUPDATETRIGGER_NONE;
timer_config.ResetTrigger = HRTIM_TIMRESETTRIGGER_NONE;
HAL_HRTIM_WaveformTimerConfig(&hhrtimA, HRTIM_TIMERINDEX_TIMER_A, &timer_config);
/* Set compare registers for duty cycle on TA1 */
compare_config.CompareValue = 46080000*Initial_Duty/Initial_Fre; /*duty cycle */
HAL_HRTIM_WaveformCompareConfig(&hhrtimA,
HRTIM_TIMERINDEX_TIMER_A,
HRTIM_COMPAREUNIT_1,
&compare_config);
/* --------------------------------- */
/* TA1 and TA2 waveforms description */
/* --------------------------------- */
output_config_TA.Polarity = HRTIM_OUTPUTPOLARITY_HIGH;
output_config_TA.SetSource = HRTIM_OUTPUTSET_TIMPER;
output_config_TA.ResetSource = HRTIM_OUTPUTRESET_TIMCMP1;
output_config_TA.IdleMode = HRTIM_OUTPUTIDLEMODE_NONE;
output_config_TA.IdleLevel = HRTIM_OUTPUTIDLELEVEL_INACTIVE;
output_config_TA.FaultLevel = HRTIM_OUTPUTFAULTLEVEL_INACTIVE;
output_config_TA.ChopperModeEnable = HRTIM_OUTPUTCHOPPERMODE_DISABLED;
output_config_TA.BurstModeEntryDelayed = HRTIM_OUTPUTBURSTMODEENTRY_REGULAR;
HAL_HRTIM_WaveformOutputConfig(&hhrtimA,
HRTIM_TIMERINDEX_TIMER_A,
HRTIM_OUTPUT_TA1,
&output_config_TA);
if(deadtime == TRUE)
{
HAL_HRTIM_WaveformOutputConfig(&hhrtimA,
HRTIM_TIMERINDEX_TIMER_A,
HRTIM_OUTPUT_TA2,
&output_config_TA);
}
if(deadtime == TRUE)
{
HRTIM_DeadTimeCfgTypeDef HRTIM_TIM_DeadTimeConfig;
/* Deadtime configuration for Timer A */
HRTIM_TIM_DeadTimeConfig.FallingLock = HRTIM_TIMDEADTIME_FALLINGLOCK_WRITE;
HRTIM_TIM_DeadTimeConfig.FallingSign = HRTIM_TIMDEADTIME_FALLINGSIGN_POSITIVE;
HRTIM_TIM_DeadTimeConfig.FallingSignLock = HRTIM_TIMDEADTIME_FALLINGSIGNLOCK_READONLY;
HRTIM_TIM_DeadTimeConfig.FallingValue = risingtime*4096/1000;
HRTIM_TIM_DeadTimeConfig.Prescaler = HRTIM_TIMDEADTIME_PRESCALERRATIO_MUL8;
HRTIM_TIM_DeadTimeConfig.RisingLock = HRTIM_TIMDEADTIME_RISINGLOCK_WRITE;
HRTIM_TIM_DeadTimeConfig.RisingSign = HRTIM_TIMDEADTIME_RISINGSIGN_POSITIVE;
HRTIM_TIM_DeadTimeConfig.RisingSignLock = HRTIM_TIMDEADTIME_RISINGSIGNLOCK_READONLY;
HRTIM_TIM_DeadTimeConfig.RisingValue = fallingtime*4096/1000;
HAL_HRTIM_DeadTimeConfig(&hhrtimA, HRTIM_TIMERINDEX_TIMER_A, &HRTIM_TIM_DeadTimeConfig);
}
if(adenable == TRUE)
{
HRTIM_ADCTriggerCfgTypeDef adc_trigger_config;
/* ------------------------------------------- */
/* ADC trigger intialization (with CMP4 event) */
/* ------------------------------------------- */
compare_config.AutoDelayedMode = HRTIM_AUTODELAYEDMODE_REGULAR;
compare_config.AutoDelayedTimeout = 0;
if(Initial_Duty >=50)
compare_config.CompareValue = 46080000*Initial_Duty/Initial_Fre; /* Samples in middle of ON time */
else
compare_config.CompareValue = 23040000*(100+Initial_Duty)/Initial_Fre;
HAL_HRTIM_WaveformCompareConfig(&hhrtimA,
HRTIM_TIMERINDEX_TIMER_A,
HRTIM_COMPAREUNIT_4,
&compare_config);
adc_trigger_config.Trigger = HRTIM_ADCTRIGGEREVENT24_TIMERA_CMP4;
adc_trigger_config.UpdateSource = HRTIM_ADCTRIGGERUPDATE_TIMER_A;
HAL_HRTIM_ADCTriggerConfig(&hhrtimA,
HRTIM_ADCTRIGGER_2,
&adc_trigger_config);
}
if(faultenable == TRUE)
{
HRTIM_FaultCfgTypeDef fault_config;
/* ---------------------*/
/* FAULT initialization */
/* ---------------------*/
fault_config.Filter = HRTIM_FAULTFILTER_NONE;
fault_config.Lock = HRTIM_FAULTLOCK_READWRITE;
fault_config.Polarity = HRTIM_FAULTPOLARITY_LOW;
fault_config.Source = HRTIM_FAULTSOURCE_DIGITALINPUT;
HAL_HRTIM_FaultConfig(&hhrtimA,
HRTIM_FAULT_1,
&fault_config);
HAL_HRTIM_FaultModeCtl(&hhrtimA,
HRTIM_FAULT_1,
HRTIM_FAULTMODECTL_ENABLED);
}
if(deadtime == TRUE)
{
/* ---------------*/
/* HRTIM start-up */
/* ---------------*/
/* Enable HRTIM's outputs TA1 and TA2 */
/* Note: it is necessary to enable also GPIOs to have outputs functional */
/* This must be done after HRTIM initialization */
HAL_HRTIM_WaveformOutputStart(&hhrtimA, HRTIM_OUTPUT_TA1 | HRTIM_OUTPUT_TA2);
}
else
HAL_HRTIM_WaveformOutputStart(&hhrtimA, HRTIM_OUTPUT_TA1);
/* Start both HRTIM TIMER A, B and D */
if(interrupt == TRUE)
HAL_HRTIM_WaveformCounterStart_IT(&hhrtimA, HRTIM_TIMERID_TIMER_A);
else
HAL_HRTIM_WaveformCounterStart(&hhrtimA, HRTIM_TIMERID_TIMER_A);
GPIO_InitTypeDef GPIO_InitStruct;
/* Enable GPIOA clock for timer A outputs */
__HAL_RCC_GPIOA_CLK_ENABLE();
/* Configure HRTIM output: TA1 (PA8) */
GPIO_InitStruct.Pin = GPIO_PIN_8;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;;
GPIO_InitStruct.Alternate = GPIO_AF13_HRTIM1;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
if(deadtime == TRUE)
{
/* Configure HRTIM output: TA2 (PA9) */
GPIO_InitStruct.Pin = GPIO_PIN_9;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}
}/**
* @brief This function calculates new duty order with PI.
* @param None
* @retval New duty order
*/
int32_t PI_Buck(uint32_t RealVol,uint32_t SetVol,int32_t dec2hex(int32_t temp))
{
/* Compute PI for Buck Mode */
/* Every time the PI order sets extreme values then CTMax or CTMin are managed */
int32_t seterr, pid_out;
int32_t error;
error = ((int32_t ) RealVol - (int32_t) SetVol);
error = dec2hex(error);
seterr = (-Kp * error) / 200;
Int_term_Buck = Int_term_Buck + ((-Ki * error) / 200);
if (Int_term_Buck > SAT_LIMIT)
{
Int_term_Buck = SAT_LIMIT;
}
if (Int_term_Buck < -(SAT_LIMIT))
{
Int_term_Buck = -(SAT_LIMIT);
}
pid_out = seterr + Int_term_Buck;
pid_out += BUCK_PWM_PERIOD / 2;
if (pid_out >= MAX_DUTY_A)
{
pid_out = MAX_DUTY_A;
CTMax++;
}
else
{
if (CTMax != 0)
{
CTMax--;
}
}
if (pid_out <= MIN_DUTY_A)
{
pid_out = MIN_DUTY_A;
CTMin++;
}
else
{
if (CTMin != 0)
{
CTMin--;
}
}
return pid_out;
}