TEA18363T

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Product data sheet

Rev. 2 — 12 December 2013

8 of 27

NXP Semiconductors

TEA18363T

GreenChip SMPS control IC

7.4 Mains voltage measuring

In a typical application, the mains input voltage is measured using the HV pin.

Once per ms the mains voltage is measured by pulling down the HV pin to ground and

measuring its current. This current then reflects the input voltage.

The system determines if the mains voltage exceeds the brownin level or it is

disconnected using an analog-to-digital converter and digital control (see Figure 1).

Once the mains is above the brownin level, the system is allowed to start switching

(see Figure 6).

If the mains voltage is continuously below the brownout level for a period of at least

30 ms, a brownout is detected and the system immediately stops switching. This period is

required to avoid that the system stops switching due to the zero crossings of the mains or

during a short mains interruption.

When the mains voltage is measured by pulling the HV pin to ground, the digital control

calculates if there is a positive dV/dt at the mains. A positive dV/dt implies that a mains is

connected.

Once a mains is detected, the measuring of the mains input voltage is stopped for a

period of 6 ms to improve efficiency. In burst mode this waiting period is enlarged to 97 ms

to improve efficiency.

Fig 6.

Mains voltage measuring

Fig 7.

Detecting mains connection by +dV/dt