QUICK START GUIDE
Demonstration System EPC9083
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DESCRIPTION
The EPC9083 is a high eciency, dierential mode Class-E amplier
development board that can operate up to 15 MHz, including 6.78 MHz
which is popular for wireless power. However, this board is not pre-
congured for any particular frequency. Higher frequency may be possible
but is currently under evaluation. The purpose of this development board
is to simplify the evaluation process of class-E amplier technology using
eGaN® FETs by allowing engineers to easily mount all the critical class-E
components on a single board that can be easily connected into an
existing system.
This board may also be used for applications where a low side switch is
utilized. Examples include, and are not limited to, push-pull converters,
current-mode Class D ampliers, common source bi-directional switch,
and generic high voltage narrow pulse width applications such as LiDAR.
The amplier board features the 200 V rated EPC2207 eGaN FET. The
amplier is set to operate in dierential mode and can be re-congured to
operate in single-ended mode and includes the gate driver and logic
supply regulator.
For more information on the EPC2207 eGaN FETs please refer to the
datasheet available from EPC at www.epc-co.com. The datasheet should
be read in conjunction with this quick start guide.
DETAILED DESCRIPTION
The Amplier Board (EPC9083)
Figure 1 shows the schematic of a single-ended, Class-E amplier with
ideal operation waveforms where the amplier is connected to a tuned
load such as a highly resonant wireless power coil. The amplier has not
been congure due to the specic design requirements such as load re-
sistance and operating frequency. The design equations of the specic
Class-E amplier support components are given in this guide and specic
values suitable for a RF amplier application can then be calculated.
Figure 2 shows the dierential mode Class-E amplier EPC9083 demo
board power circuit schematic. In this mode the output is connected
between Out 1 and Out 2. A block-wave external oscillator with 50 %
duty cycle and 0 V – 5 V signal amplitude is used as a signal for the board.
Duty cycle modulation is recommended only for advanced users who
are familiar with the Class-E amplier operation and require additional
eciency.
The EPC9083 is also provided with a 5 V regulator to supply power to the
logic circutis and gate driver. Adding a 0 Ω resistor in position R90 allows
the EPC9083 to be powered using a single-supply voltage; however in this
conguration the maximum operating voltage is limited to between 7 V
and 12 V.
Single-ended Mode operation
Although the default conguration is dierential mode, the demo
board can be re-congured for single-ended operation by shorting out
C74 (which disables only the drive circuit) and connecting the
load between Out 1 and GND only (see gures 2 and 5 for details).
Class-E amplier operating limitations
The impact of load resistance variation is signicant to the performance of
the Class-E amplier, and must be carefully analyzed to select the optimal
design resistance.
The impact of load resistance (R
Load
– Real part of Z
Load
) variation
on the operation of the Class-E amplier is shown in gure 3. When
operating a Class-E amplier with a load resistance (R
Load
– Real part
of Z
Load
) that is below the design value (see the waveform on the
left of gure 3), the load tends to draw current from the amplier
too quickly. To compensate for this condition, the amplier supply
voltage is increased to yield the required output power. The shorter
duration of the energy charge cycle leads to a signicant increase in
the voltage to which the switching device is exposed. This is done in
order to capture sucient energy and results in device body diode
conduction during the remainder of the device o period. This period
is characterized by a linear increase in device losses as a function of
decreasing load resistance (R
Load
).
When operating the Class-E amplier with a load resistance (R
Load
)
that is above the design value (see the waveform on the right of
gure 3), the load tends to draw insucient current from the ampli-
er, resulting in an incomplete voltage transition. When the device
switches there is a residual voltage across the device, which leads to
shunt capacitance (C
OSS
+ C
sh
) losses. This period in the cycle is char-
acterized by an exponential increase in device losses as function of
increasing reected load resistance.
* Maximum current depends on die temperature – actual maximum current will be
subject to switching frequency, bus voltage and thermals.
EPC9083 Amplier Board
Table 1: Performance Summary (TA = 25°C) EPC9083
Symbol Parameter Conditions Min Max Units
V
IN
Main Supply Voltage
Range
Class-E Conguration 0 40 V
Current Mode Class-D
Conguration
0 35 V
Push-Pull Conguration 0 80 V
V
DD
Control Supply Input
Range
7 12 V
I
OUT
Switch Node Output
Current (each)
4* A
V
OSC
Oscillator Input
Threshold
Input ‘Low’ -0.3 1.5 V
Input ‘High’ 3.5 5 V