October 2014
39
A
UTOMOTIVE
interfaces such as LIN 2.1, RVC (Regulated
Voltage Control), PWM, C-Term and a bit-se-
rial interface are integrated in the generator
regulator, the component is highly universal.
In most cases, the generator is mechanically
attached directly to the motor shaft. Through
appropriate excitation of the rotor windings,
output variables such as speed can be deter-
mined automatically. During a cold start, the
electronic system has to decide whether the
battery still has sufficient capacity or whether
electricity needs to be immediately generated,
which would increase the speed of the motor.
This is the task of the load response control
(LRC), which controls the load when starting
torque occurs. In conventional solutions, this
takes place as part of a strictly defined LRC
scheme during a cold start. Epona allows
you to completely redefine the LRC proper-
ties, which means that for example other load
torques can be set.
The generator regulator performs normal bat-
tery recharging in P-controller mode, whereby
quasi-recuperation mode is also possible
here. These functions can be programmed
directly or controlled via the relevant inter-
faces. When a suitable target regulated voltage
is specified via LIN, the bit-serial interface or
the analog protocols, as is currently the case,
the controller ensures that recharging stops
once this voltage has been reached by setting
the excitation coil current to zero. The com-
parators required for this are already con-
tained; the relevant threshold values are set by
programming the parameters. Even if other
battery technologies replace lead batteries in
the future, Epona allows the parameters to be
adjusted more easily.
The generator regulator can respond to differ-
ent events in the on-board electrical system
and in the controller itself. The component
is equipped with protected output drivers,
which allow for a simplified design. Different
trigger levels can also be introduced by means
of software to allow a more flexible response
to the current situation in the vehicle. These
include the ability to connect and shut-down
loads as well as to compensate for and respond
to large loads. When powerful consumers are
switched on and off in a 24V on-board electri-
cal system, for example, this can lead to major
disturbances in the electrical system. With the
right software, however, these peaks can be
stabilized relatively quickly.
The solution also features Control Fault Diag-
nosis as well as systems for increasing opera-
tional safety and reliability, with a watchdog
being just one of a multitude of such systems.
Epona is a system in a package containing
two semiconductor chips – one high voltage
component and one CMOS component. This
separation means that the state machine can
be woken by the hardware or a reset can be
carried out, which offers improved safety over
a monolithically integrated solution.
The generator regulator was originally
designed exclusively for the European mar-
ket. But since the excitation coil is available
on the global market in both a high-side and
low-side configuration, EBV designed the
control output in such a way that it can actu-
ate the MOSFET switch for the excitation coil
winding both directly to earth and directly to
the positive supply voltage. Epona therefore
features a suitable gate driver that can drive
the MOSFET in both the high-side and low-
side configuration. A sensor input can then
be used to clearly establish whether or not
the MOSFET has switched through. The com-
ponent can also measure the current flowing
through the excitation coil as well as the volt-
age currently applied. For this measurement,
variable gain amplifiers that are suitably buff-
ered depending on the input or output are fit-
ted on the chip.
The generator regulator also offers functions
to prevent individual batteries from becom-
ing overloaded in systems containing multiple
generators. For this purpose, the component
features universal inputs that can be con-
nected differently depending on the applica-
tion. To ensure that raised current levels in
this circuit can also be utilized, load-depen-
Figure 1. Block diagram of Epona, a system in a package containing two semiconductor chips –
one high voltage component and one CMOS component
