QUICK START GUIDE
EPC – EFFICIENT POWER CONVERSION CORPORATION |
| COPYRIGHT 2017 | | 3
Demonstration System EPC9113
MECHANICAL ASSEMBLY
The assembly of the EPC9113 Wireless Demonstration kit is simple and
shown in Figure 1. The source coil and amplifier have been equipped
with SMA connectors. The source coil is simply connected to the
amplifier.
The device board does not need to be mechanically attached to the
source coil.
The coil sets of the EPC9111 and EPC9112 (both the source and
device coils) are not compatible with the EPC9113/4 kit. To prevent
inadvertent connection of either, the connectors of the amplifier and
coils have been changed from reverse polarity to standard polarity.
Please contact EPC for modifications to the original coil set to ensure
compatibility with the EPC9509 amplifier.
DETAILED DESCRIPTION
The Amplifier Board (EPC9509)
Figure 2 shows the system block diagram of the EPC9509 ZVS class-D
amplifier with pre-regulator and Figure 3 shows the details of the
ZVS class-D amplifier section. The pre-regulator is used to control
the ZVS class-D wireless power amplifier based on three feedback
parameters 1) the magnitude of the coil current indicated by the
green LED, 2) the DC power drawn by the amplifier indicated by
the yellow LED and 3) a maximum supply voltage to the amplifier
indicated by the red LED. Only one parameter at any time is used to
control the pre-regulator with the highest priority being the maximum
voltage supplied to the amplifier followed by the power delivered
to the amplifier and lastly the magnitude of the coil current. The
maximum amplifier supply voltage is pre-set to 52 V and the maximum
power drawn by the amplifier is pre-set to 16 W. The coil current
magnitude is pre-set to 800 mA
RMS
but can be made adjustable
using P25. The pre-regulator comprises a SEPIC converter that can
operate at full power from 17 V through 24 V.
The pre-regulator can be bypassed by connecting the positive supply
directly to the ZVS class-D amplifier supply after removing the jumper
at location JP1 and connecting the main positive supply to the bottom
pin. JP1 can also be removed and replaced with a DC ammeter to directly
measure the current drawn by the amplifier. When doing this observe
a low impedance connection to ensure continued stable operation of
the controller. Together with the Kelvin voltage probes (TP1 and TP2)
connected to the amplifier supply, an accurate measurement of the
power drawn by the amplifier can be made.
The EPC9509 is also provided with a miniature high efficiency switch-
mode 5 V supply to power the logic circuits on board such as the gate
drivers and oscillator.
The amplifier comes with its own low supply current oscillator that is
pre-programmed to 6.78 MHz ± 678 Hz. It can be disabled by placing
a jumper into JP70 or can be externally shutdown using an externally
controlled open collector / drain transistor on the terminals of JP70 (note
which is the ground connection). The switch needs to be capable of
sinking at least 25 mA. An external oscillator can be used instead of the
internal oscillator when connected to J70 (note which is the ground
connection) and the jumper (JP71) is removed.
The pre-regulator can also be disabled in a similar manner as the oscillator
using JP50. However, note that this connection is floating with respect to
the ground so removing the jumper for external connection requires a
floating switch to correctly control this function. Refer to the datasheet of
the controller IC and the schematic in this QSG for specific details.
The ZVS timing adjust circuits for the ZVS class D amplifiers are each
independently settable to ensure highest possible efficiency setting
and includes separate ZVS tank circuits. This allows OOK modulation
capability for the amplifier.
The EPC9509 is provided with 3 LED’s that indicate the mode of
operation of the system. If the system is operating in coil current limit
mode, then the green LED will illuminate. For power limit mode, the
yellow LED will illuminate. Finally, when the pre-regulator reaches
maximum output voltage the red LED will illuminate indicating that
the system is no longer A4WP compliant as the load impedance is too
high for the amplifier to drive. When the load impedance is too high
to reach power limit or voltage limit mode, then the current limit LED
will illuminate incorrectly indicating current limit mode. This mode
also falls outside the A4WP standard and by measuring the amplifier
supply voltage across TP1 and TP2 will show that it has nearly reach the
maximum value limit.
Table 2: Performance Summary (T
A
= 25 °C) Category 3 Device Board
Symbol
Parameter
Conditions Min
Max Units
V
OUT
Output Voltage Range
0
38
V
I
OUT
Output Current Range
0
1.5#
A
# Actual maximum current subject to operating temperature limits
Table 1: Performance Summary (T
A
= 25°C) EPC9509
Symbol
Parameter
Conditions
Min
Max Units
V
IN
Bus Input Voltage Range – Pre-
Regulator Mode
Also used in
bypass mode
for logic supply
17
24
V
V
IN
Amp Input Voltage Range –
Bypass Mode
0
52
V
V
OUT
Switch-Node Output Voltage
52
V
I
OUT
Switch-Node Output
Current (each)
1*
A
V
extosc
External Oscillator Input
Threshold
Input ‘Low’
-0.3
0.8
V
Input ‘High’
2.4
5
V
V
Pre_Disable
Pre-Regulator Disable
Voltage Range
Floating
-0.3
5.5
V
I
Pre_Disable
Pre-Regulator Disable
Current
Floating
-10
10
mA
V
Osc_Disable
Oscillator Disable
Voltage Range
Open Drain/
Collector
-0.3
5
V
I
Osc_Disable
Oscillator Disable
Current
Open Drain/
Collector
-25
25
mA
V
sgnDiff
Differential or Single-Select
Voltage
Open Drain/
Collector
-0.3
5.5
V
I
sgnDiff
Differential or Single-Select
Current
Open Drain/
Collector
-1
1
mA
* Maximum current depends on die temperature – actual maximum current will be subject to switching
frequency, bus voltage and thermals.