GreenChip PC secondary control ICs
Rev. 01 — 13 February 2009
Preliminary data sheet
1. General description
The TEA1781T and TEA1782T are designed to cooperate with the TEA1771T primary
side controller in a unique converter topology based on the active clamp forward
converter. On the secondary side the output voltages are regulated via bidirectional
switches. A typical application area of this converter is a power supply for a desktop PC.
The TEA1781T and TEA1782T are secondary control ICs and regulate each output
voltage independently of the primary duty cycle and other secondary output voltages.
Because of these separated regulations, the system does not show any cross regulation
and makes the design of the transformer easier.
As each output can also be completely turned off, the system allows for an integrated
standby supply. To maximize the efﬁciency in Standby mode, the duty cycle and operating
frequency are minimized in Standby mode.
The TEA1781T and TEA1782T have integrated drivers and individual output voltage
regulators. In this way the 3.3 V, 5 V, 12 V and 5 V standby outputs of a typical PC power
supply are regulated separately giving accurate output voltages and fast transient
All requirements according to the Intel ATX speciﬁcation (V 2.0) are integrated, such as
soft start, a PS_ON# connection, a PwrOK signal and all required protections like
OverCurrent Protection (OCP) and OverVoltage Protection (OVP). These voltage and
current levels are monitored at each output separately. The system also has an
OverTemperature Protection (OTP) function.
The system fulﬁlls the current and proposed efﬁciency standards such as 80+ gold,
energy star and blue angel.
The TEA1781T and TEA1782T are implemented in a high voltage (ABCD)
Silicon On Insulator (SOI) process.
I Designed for ATX PC power supplies
I Integrated standby supply
I Enhanced efﬁciency in Standby mode
I No cross regulation
I Accurate output voltage regulation
I Fast transient response
I Integrated soft start for all output voltages
I Flexible transformer design without the need of a post regulator