Q67000-A9284-X201-K5 データシートの表示（PDF） - Infineon Technologies
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Q67000-A9284-X201-K5 Datasheet PDF : 39 Pages
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TDA 16888
PFC Section
At normal operation the PFC section operates with dual loop control. An inner loop,
which includes OP2, C1, FF1 and the PFC’s driver, controls the shape of the line current
by average current control enabling either continuous or discontinuous operation. By the
outer loop, which is supported by OP1, the multiplier, OP2, C1, FF1 and the PFC's driver,
the PFC output voltage is controlled. Furthermore there is a third control loop composed
of OTA1, OP2, C1, FF1 and the PFC’s driver, which allows the PFC section to be
operated as an auxiliary power supply even when the PWM section is disabled. With
disabled PWM section, however, the PFC section is operated with half of its nominal
operating frequency in order to reduce the overall current consumption.
Based on a pulse-width-modulation, which is leading edge triggered with respect to the
internal clock reference CLK OUT and which is trailing edge modulated according to the
PFC ramp signal VPFC RMP and the output voltage of OP2 VPFC CC (see Figure 18), the
PFC section is designed for a maximum duty cycle of ca. 94% to achieve minimal line
current gaps.
PWM Section
The PWM section is equipped with improved current mode control containing effective
slope compensation as well as enhanced spike suppression in contrast to the commonly
used leading edge current blanking. This is achieved by the chain of operational amplifier
OP3, voltage source V1 and the 1st order low pass filter composed of R1 and an external
capacitor, which is connected to pin 15 (PWM RMP). For crosstalk suppression between
PFC and PWM section a signal-to-noise ratio comparable to voltage mode controlled
PWM’s is set by operational amplifier OP3 performing a fivefold amplification of the PWM
load current, which is sensed by an external shunt resistor. In order to simultaneously
perform effective slope compensation and to suppress leading spikes, which are due to
parasitic capacitances being discharged whenever the power transistor is switched on,
the resulting signal is subsequently increased by the constant voltage of V1 and finally
fed into the 1st order low pass filter. The peak ramp voltage, that in this way can be
reached, amounts to ca. 6.5 V. By combination of voltage source V1 and the following
low pass filter a basic ramp (step response) with a leading notch is created, which will
fully compensate a leading spike (see Figure 12) provided, the external capacitor at
pin 15 (PWM RMP) and the external current sensing shunt resistor are scaled properly.
Data Sheet
8
2000-02-28
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