Start
• Design
requirements
•
System
Architecture
•
External
Charging Unit
•
Internal
Charging Unit
•
Charging
Coils
•
Charging
Data
• Power
Up
•
Sources
and PDF
EXTERNAL
CHARGING UNIT
The
ECU converts energy from the electric power mains
into an AC waveform that can be transmitted to
the ICU through a pair of mutually coupled transinductance
coils. Closing an SPST slide-switch initiates
the operation of the ECU (see Figure 2, p. 14).
When this switch is closed, it takes the ATmega8
microcontroller’s PD7 pin high. The microcontroller
continuously polls PD7.
|
(Click
here to enlarge)
|
Figure
2—For the ECU, energy is received by the inductor
connected to the two-pin header J1. You can
control the ECU via the RS-232 interface. |
When
the input is high, an AC waveform through the
transinductance coil is generated. Using the ATmega8’s
control pins PD5 and PD6 to alternately open and
close the FETs diagonally opposite each other
generates the AC waveform. Rather than using microcontroller
pins directly, an NDS9956A FET array provides
higher currents than the microcontroller can provide
by itself.
For
our transinductance coil, a nominal self-inductance
of 4 mH was measured, along with a series resistance
of 5 W. This corresponded to a coil self-impedance
of approximately 120 W at 4.7 kHz.
