Infineon XDPP1100, Technical Reference Manual

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User Manual 139 of 562 V 1.0
2021-08-25
XDPP1100 technical reference manual
Digital power controller
Digital pulse width modulator
7.3.2 Peak current mode control
PCMC is based on current information and it can be selected by setting the register value mode_control_loopX
to 1 for secondary-side PCMC or to 2 for primary-side PCMC. In the case of PCMC the compensator output
represents the control current, whereas for VMC it was directly the duty cycle.
Figure 61 shows the functional
block diagram of the XDPP1100 internal configuration when PCMC is applied.
Figure 61 Functional block diagram of PCMC
PID selection for ramp0 and ramp1 is programmable, whereas the CE selection is hardwired. This is because:
•
Current estimator CE0 (ISEN) is connected to ramp0
•
Current estimator CE1 (BISEN) is connected to ramp1
•
Current used for control (either primary or secondary) should be sensed by ISEN/IREF in a single-loop
system using ramp0
The PID output represents “normalized control current”, where the normalization is to the maximum range of
the IADC. This leads to a signed output range of -1.0 to +1.0. PCMC supports only TE modulation, and therefore
the register
rampX_m_flavor should be set to value 2. This means that the t1 crossing event always occurs at
ramp = 0.
PCMC requires slope compensation to prevent subharmonic oscillation when the duty cycle is higher than 0.5.
A slope compensation ramp is provided, and its value is programmable through register
compensation_slope ,
as shown in Table 43 .
Table 43 PCMC slope compensation values
Compensation_slope Slope of compensation ramp
0 V
OUT
/ L
1 V
OUT
/ 2L
2 V
OUT
/ 4L
3 Reserved
As illustrated in Figure 61 , the output of the slope compensation ramp is subtracted from the control current in
order to obtain the reference current. The reconstructed current output from the CE, synth_i, is then compared
against this reference current. Both of these currents are digital and discrete in time. Therefore, in order to
PID
S
+
-
control_current
Slope Compensation
compensation_slope
Current
Estimator
synth_i
PCMC
cross
detect
current slope information
Ramp
t1_val = 0
t1_crossing
t2_crossing
ramp
cross
detect
t2_phase
ref_current