TEA2017ABTSLASH2 datasheet(21/67 Pages) NXP

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NXP Semiconductors

TEA2017ABT/2

Digital configurable LLC and DCM/QR PFC controller

aaa-026794

FEEDBACK CONTROL

A/D

SNSFB

VSNSFB

12 kΩ

VPWRGD+VT

960 mV

Figure 19. Optobias regulation

Figure 19 shows that when the optocurrent decreases, the internal voltage across the

12 kΩ resistor drops to below the targeted level of 960 mV (= 80 μA (typical) × 12 kΩ).

The TEA2017ABT then slowly increases an additional offset at the power level (ΔP).

It continues to increase the additional offset until the optocurrent reaches the target of

80 μA (typical). When the optocurrent increases due to a transient, the additional offset

to the power level is decreased. As a result, the output voltage decreases which again

decreases the optocurrent. In this way, the optocurrent is continuously regulated to the

Ireg(SNSFB) level.

The behavior of the internal circuitry connected to the SNSFB pin is the same as

the behavior of the traditional circuitry. The fixed voltage at the SNSFB pin and the

continuous regulation of the optocurrent level does not influence the regulation level.

The advantage, however, is a reduction in no-load input power and an optimization of the

transient response.

When the system operates in low-power mode at the minimum energy per cycle and at

minimum duty cycle, it can no longer reduce the optocurrent level to the Ireg(SNSFB) target

(» 80 μA typical). If the output power decreases further and the optocurrent increases to

above the level of Istart(burst)

(» 100 μA typical), the burst mode is triggered. When the output power drops to below

this level again, a new burst cycle is started (see Figure 14 and Figure 15).

8.5 Power factor correction (PFC) regulation

To achieve a high power factor (PF) and low total harmonic distortion (THD), the input

current of the power supply must follow the mains input voltage. However, as the filter

capacitances cause a shift of 90° between the mains input current and its voltage, the

input filter disrupts PF and THD. To improve PF and THD, the average PFC current is in

accordance with a shifted sine wave (see Figure 20).

TEA2017ABT_2

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 1.1 — 17 May 2023

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