L9305EP datasheet(22/107 Pages) STMICROELECTRONICS

22 / 107 page

Figure 11. Fixed frequency signals

Tpwm

(2)

(1)

(2)

PWM

Load

current

GADG2709181214PS

In fixed frequency current control, basic operation is dependent on the ramp generator and the PI signal as

follows:

•

Switch OFF point (1): the PI signal crosses the RAMP signal from high to low, the output driver is switched

off and the load CURRENT reaches its maximum peak value.

•

Switch ON point (2): every clock based TPWM periods, the RAMP signal resets and the output driver is

switched on and the load current reaches its minimum peak value.

To optimize current control capability, the user must properly select KP and KI amplitude settings

(Channel_x.KGAINS) for each application.

•

KP: parameter controls the amplitude of the Proportional signal and is calculated as:

KP=2KP_sel

•

KI: parameter controls the amplitude of the Integral signal and is calculated as:

KI=2KIsel

6.1.5

Variable frequency control

From Figure 12, the current control loop subtracts the measured current from the programmed set point to derive

an error signal. The integral amplifier with gain KI processes the error signal creating the INTEGRAL signal. The

frequency control loop subtracts the PWM period set point TPWM from the measured PWM period creating a

period error signal. The integral amplifier with gain KFI, processes the period error and generates the resulting

frequency integral (F_I) output signal.

Variable frequency control operation is dependent on the INTEGRAL signal, F_I signal and zero level signal as

follows:

•

Switch OFF point: the INTEGRAL signal crosses the F_I signal from high to low, the output driver is

switched off and the load CURRENT reaches its maximum peak value.

•

Switch ON point: the INTEGRAL signal crosses the zero level signal from low to high, the output driver is

switched ON, and the load CURRENT reaches its minimum peak value.

The variable frequency control provides a transient mode for optimization of the transient condition behavior. It

eliminates in this way current over/undershoot and allows the fastest reaching of the final frequency. The transient

mode is entered in case of a change of current set point (Set Point Change) while the Auto Limit control bit is set.

The transient mode is also entered in case the PWM period is longer than a threshold (Long Period Detection).

The 2-bit control input Transition Time (D[15:14] in CTRLCFG register) selects the Long Period Detection

threshold.

L9305

Current control drivers

DS12774 - Rev 10

page 22/107

L9305EP 数据表(PDF) 22 Page - STMicroelectronics

L9305EP 数据表(HTML) 22 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载