NRU Series
56
4 Ignition Power Control
The ignition power control module for in-vehicle applications is an MCU-based
implementation that monitors the ignition signal and reacts to turn on/off the
system according to predefined on/off delay. Its built-in algorithm supports other
features such as ultra-low power standby, battery-low protection, system
hard-off, etc. In this section, we’ll illustrate the principle of ignition power control
and operation modes.
4.1
Principles of Ignition Power Control
The basic concept of ignition power control module is to control the timing
correlation between ignition signal and system power status. A typical timing
correlation is described in following diagram.
1.
When DC power is supplied to the system, MCU starts to periodically
detect ignition signal. Note that only MCU is working at this moment and
the overall power consumption is less than 2 mW.
2.
Ignition signal is active (both 12VDC and 24VDC ignition signals are
accepted).
3.
MCU starts to count a pre-defined power-on delay.
4.
Once power-on delay expired, MCU turns on necessary standby power for
the system (3.3VSB & 5VSB).
5.
A PWRBTN# pulse is then issued to turn on the system (equivalent to one
pressing the power button on the front panel).
6.
The system is booting and becomes operational.
7.
After a period of time, the ignition signal becomes inactive.
8.
MCU starts to count a pre-defined power-off delay.
