GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 1
Please refer to the Evaluation Board/Kit Important Notice on page 27
GSWP300W-EVBPA
300W GaN E-HEMT Wireless Power Transfer
Evaluation Board, Optimized for Class EF2
Amplifiers
User’s Guide
Visit www.gansystems.com for the latest version of this user’s guide.
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 2
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DANGER!
Electrical Shock Hazard - Hazardous high voltage may be present on the
board during the test and even brief contact during operation may result in
severe injury or death. Follow all locally approved safety procedures when
working around high voltage.
Never leave the board operating unattended. After it is de-energized,
always wait until all capacitors are discharged before touching the board.
This board should be handled by qualified personnel ONLY.
PCB surface and devices can become hot. Contact may cause burns. Do not
touch!
CAUTION
This product contains parts that are susceptible to damage by electrostatic
discharge (ESD) or exposure to voltages in excess of the specified voltage.
Always follow ESD prevention procedures when handling the product.
Avoid applying excessive voltages to the power supply terminals or signal
inputs or outputs, always connected to the load during the test on-going.
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 3
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Introduction to Magnetic Resonant Wireless Power Transfer
Recent technological advances in power semiconductors are enabling Wireless Power Transfer
(WPT) as a technically and commercially viable option for charging and powering equipment
across a wide range of markets, applications, and power levels.
Inductive charging has been in use for a number of years, however, it’s burdened with limitations
that restrict it to low power applications with tightly controlled alignment between the transmitter
and receiver.
A more advantageous approach, magnetic resonant charging, addresses these shortcomings by
using a high frequency oscillating magnetic field to transfer energy. The benefits that magnetic
resonant charging offers include variable spacing between the transmitter and receiver, the ability
to charge through materials such as a desk or an enclosure, one-to-many charging, ease of
installation, suitability for high power levels, and fast charging. Table 1 provides a comparison
between inductive charging and magnetic resonant charging.
GaN E-HEMTS are a key enabler of magnetic resonant charging because their extremely fast
switching speeds, on the order of a few nanoseconds, result in very low switching losses. This
allows them to operate efficiently at very high frequencies, such as the 6.78MHz that is commonly
used for magnetic resonant charging.
Table 1 A comparison of Inductive charging and Magnetic Resonant charging
Charging technology
Inductive
Magnetic Resonant
Frequency range
80-300kHz
6.78MHz
Max transfer range
5mm
50mm
Multi-device
No
Yes, at different power levels
Spatial Freedom
Low
High
Power Range
Low & limited
30W max
Broad & versatile
50W to 20kW+
Efficiency
Limited to 80%
High: up to 95%
A high-level block diagram of a resonant wireless power transfer system is shown in Figure 1. The
transmit section is composed of a power amplifier, an impedance matching circuit and a transmit
coil. High frequency energy is transferred wirelessly at 6.78MHz to the receive circuit which is
comprised of a receive coil, an impedance matching circuit and a rectifier.
The GSWP300W-EVBPA evaluation board is designed to support and expedite the innovation of
WPT systems by providing the Power Amplifier, the most challenging aspect of the system design.
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 4
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Figure 1 - A magnetic resonant wireless power transfer design.
Evaluation board overview
The GSWP300W-EVBPA uses GaN Systems’ GS66508B E-HEMTs in a 6.78MHz Class EF2 power
amplifier. The GS66508Bs are used with the integrated high-speed pSemi PE29102 gate driver in a
push-pull configuration. The outputs of the PE29102 are capable of providing switching transition
speeds in the nano-seconds range for hard switching applications.
This User’s Guide includes a circuit description, a quick-start guide and measurement results.
Evaluation Kit Contents and Requirements
Kit Contents
The GSWP300W-EVBPA includes the following hardware for evaluating the GaN E-HEMT 300W
power amplifier.
Table 2 GSWP300W-EVBPA Evaluation Kit Contents
Quantity
Description
1
GaN E-HEMT GS66508B WPT PA evaluation board assembly
1
WPT PA heatplate
1
WPT PA EMC shield
2
2 pins DC cord
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 5
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Hardware Requirements
In order to evaluate the performance of the evaluation board, the following equipment is required:
•
DC power supply 100V/15A
•
TEK scope with current probe TCM0030A
•
Fluke 87 multimeter for input current
•
50dB 500W attenuator as load
•
Spectrum analyzer
•
Power meter
•
Thermal meter
Evaluation Board Assembly Overview
The evaluation board (EVB) is assembled with two GS66508B E-HEMT transistors and two PE29102
GaN E-HEMT drivers. Headers are included for monitoring the signal input, signal output, power
connections and detection monitoring signals. Probe points are included for waveform
measurements. Provision has been made for a single, suitable heatsink to be fastened against the
two E-HEMTs, using the two holes in the center of the bottom heatplate.
Figure 2 • Top side of GSWP300W-EVBPA Evaluation Board Assembly
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 6
Please refer to the Evaluation Board/Kit Important Notice on page 27
Figure 3 • Bottom side of GSWP300W-EVBPA Evaluation Board Assembly, showing copper coins
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 7
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Block Diagram
The block diagram of the evaluation board is provided in Figures 4 through 6.
Figure 4 • GSWP300W-EVBPA WPT Push-Pull EVB Block Diagram
Note: The coil in Figure 4 is not included in the EVB.
Figure 5• GSWP300W-EVBPA WPT Class EF2 PA Block Diagram
Note: The switch devices are GaN Systems’ GS66508B E-HEMTSs
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 8
Please refer to the Evaluation Board/Kit Important Notice on page 27
Figure 6 • GSWP300W-EVBPA WPT driver Block Diagram
Figure 7 • PE29102 Dead-time Waveforms and Duty Cycle Setting
Figure 8 • Dead Time vs Dead Time Resistor
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Circuit Description
The Push-Pull circuit is comprised of two single ended PAs which share a common supply, however;
the impedance matching and EMI filters are separated.
The high-side E-HEMTs are powered by a DC source, referred to as the HV supply. It is connected
through J32 or J28. The voltage of this source not exceed 100VDC.
The low-voltage logic circuitry runs off a 3.3VDC voltage regulator, U88, which is powered from a
+5VDC source connected through JP35 or J28. The +5VDC rail also feeds two PE29102 drivers U86 and
U90, which are driven independently by U87, a common logic D-type flip/flop. U87 has a
frequency divider configuration, which is driven by a crystal oscillator Y8 at a frequency of
13.56MHz. The two PE29102 gate drives are capable of 6V operation.
The PA can be configured to operate in a number of different modes, which include
• Push-pull configuration with an EMI filter
• Single ended mode
• Operation without an EMI filter
• Operation with an external oscillator signal input. Users can run multiple PAs together at
the same frequency for high power operation.
Detailed operation procedures and setup for these alternative configurations are provided in the
section titled “quick start guide”.
The PA includes an over-temperature protection circuit. Temperature sensor U9, placed close to the
GS66508B E-HEMTs, monitors their temperature. In an over-temperature condition, the PE29102A
driver will be disabled through U133 and stop driving the E-HEMTs. The design also includes
circuitry to protect against over-current, and load mismatch.
The evaluation board includes an EMI filter, comprised of one low pass filter and one notch filter.
The output of PA can be configured, through jumpers, to operate either with or without an EMI
filter. The detailed jumper and SMA connector configurations are listed in Table 4
For convenience, test points are provided to monitor and measure the electrical signals. A
description of the test points and diagram of their location is provided in Table 5.
The PA also includes a Micro Controller Unit (MCU) monitor interface header, J1. The signals
available through J1 can be used to control the PA system for close loop in the WPT system. A
definition of the signals available on header J1 is provided in Figure 9.
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 10
Please refer to the Evaluation Board/Kit Important Notice on page 27
Figure 9 • MCU interface definition. Signals on J1
The PA connectivity is depicted in Figure 10 and includes the RF input and output, the DC biases
and the MCU monitor interface.
Figure 10 • Circuit Connectivity
Protection Circuit
The PA includes circuitry to protect against input DC overcurrent, device over temperature, output
RF overvoltage and Voltage Standing Wave Ratio (VSWR) protection. The protection signals are
combined by U133, a 3 inputs OR gate logic chip, and will shut the driver down under a fault
condition.
Input DC overcurrent protection (OCP): U91 is the DC current sensor chip, which can handle a
maximum of 10A. The output of the current sensor ship is a current sense signal that goes thru
buffer OP U122 and is compared to a reference voltage. The reference voltage is set with R101 and
• Monitor signals on J1.
• Pin1: PA GND
• Pin2: 5V Input
• Pin3: output voltage detection
• Pin4: PA HV DC current
• Pin5: 3.3V DC
• Pin6: over voltage and current
• Pin7: output power detection
• Pin8: Temperature sensor voltage
• Pin9: PA HV DC input
• Pin10: Fan control enable
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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R177. Upon an over current event, a signal is generated to signal OCP_TRIG.
Overvoltage protection (OVP): The design includes overvoltage protection circuitry for both the
high side and the low side. The high side voltage sensor is comprised of C276, C277, and two
Schottky diodes; D52 and D44. C276/C277 form a voltage divider, the ratio of which can be
changed. Two diodes rectify the RF signal to DC thru C278/C22 and R111 and the resulting voltage
represents the high side output. The low side circuit is similar. It’s comprised of C270, C280, and
two diode D50, D53. These two voltage detection signals go to a two-channel comparator U68 and
are combined with OR gate U70 into one overvoltage trigger, OVP_TRIG.
The OVP and OCP go into a hard combine circuit D45, which a dual diode in one. To generate an
overcurrent / overvoltage protection trigger signal.
Standing Wave Ratio (SWR) detection: two of coupler, T2, T83, comprise of the board band
bidirectional coupler. The reflection signal goes thru D75, C722, C721, it turns into DC signal which
goes thru the buffer OP U132 into comparator U130, of which the reference voltage is set by the
R936/R937, the trigger point can be set by the reference voltage, which is refer the SWR. The
direction of the coupler is around 15dB at 6.78MHz.
Figure 11 • Connectivity locations
Thermal Management
Thermal management of the GaN E-HEMTs in this RF power system is a critical aspect of the
J56
RF output before EMI filter
J28
HV DC Input
J31 & J33
RF output before EMI
Single ended
J1
MCU interface
J57
RF Out
Push pull SMA
pSemi
PE29102A
GaN Systems
GS66508B
J34
SMA external input
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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design. Maintaining low device temperatures through proper thermal management enhances the
system reliability and extends the range of operating temperature.
The GS66508B are bottom-side cooled devices that use GaNPX® packaging, designed for optimal
thermal performance. For effective thermal management, a hole is cut out of the PCB to permit
access to the copper coins. The two GS66508Bs’ bottom side thermal pads are soldered directly onto
the copper coins on the bottom side of the PCB and the Gate, Drain and Source signals are routed on
the top side of the PCB. This set up provides an ultra-low thermal impedance from the die to the
copper coins.
Figure 12 • Copper coins soldered beneath PCB and devices top PCB
Figure 13 • Aluminum heatplate with housing for two copper coins.
Heatplate
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 180614 © 2018 GaN Systems Inc. www.gansystems.com 13
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Quick Start Guide
The GSWP300W-EVBPA EVB is designed to as a platform for evaluating the GS66508B E-HEMTs in a
Push-Pull Class EF2 PA for WPT. This chapter will guide the user through the evaluation board
overview, PA operation, bench setup and test results.
Evaluation Board Overview
Kit Contents
The GSWP300W-EVBPA evaluation kit contains:
•
Power Amplifier evaluation board assembly
•
PA heatplate
•
PA EMC shield
•
4 pins DC cord
Evaluation board specifications
Table 3: EVB specifications:
PARAMETER
SPECS
Input Voltage range
100V
DC
max
Tx output power
300W
Tx efficiency (peak)
88%
Topology/Class
EF2
Frequency
6.78 MHz
Switching type
Push/Pull
GaN Systems part number
GS66508B
Number of GS devices
2
Optimized RL (load)
30Ω
Constant current mode
optional
The maximum operating specifications of the evaluation board are as follows:
•
Maximum HV supply input operating voltage of 100VDC. The 100VDC limit is based on
capacitor selection. Operation at a higher power level can be achieved if the capacitors are
replaced with ones having a higher voltage rating.
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Please refer to the Evaluation Board/Kit Important Notice on page 27
•
Maximum LV supply input operating voltage of 7VDC
•
Frequency of operation of 6.78MHz.
•
Maximum output power of 300W (default setting, adjustable)
Note: * The maximum output power depends on the input voltage, as shown in Figures 19 and
22
Configurations
The PA can be configured into three different operating options: voltage mode, current mode, and single
ended. Table 4 describes how to configure the board using the jumpers provided.
Table 4: Configuration options
Jumper
Option
Jumper on/off
JP51
Internal oscillator (default)
JP51 on / JP52 off
JP52
External oscillator
JP51 off / JP52 on
Voltage mode (without EMI filter)
Voltage mode
JP5/JP43/JP6/JP44 off
Current mode (with EMI filter)
Current mode
JP5/JP43/JP6/JP44 on
Voltage mode output
RF output
JP56
Current mode output
RF output
JP57
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Test points
To monitor the performance of PA, test points are provided and as described in Table 5. All test points
are available on the top side of the board, none are on the bottom side. The test points locations are
silkscreened on the PCB.
Table 5: Test point description
Test point Description
TP197 U90 input (PE29102 driver)
TP76 U6 input (PE29102 driver)
TP8 Q77 Gate voltage
TP81 Q76 Gate voltage
TP189 Q77 Drain voltage
TP82 Q76 Drain voltage
TP176 60V DC current detection
TP194 External oscillator monitor
Evaluation Bench Test Setup
The test bench setup for the GSWP300W-EVBPA EVB is shown in Figure 14. Ensure that the safety
precautions mentioned on page 2 are followed.
Figure 14 • Bench setup
A recommended list equipment is provided below. Equipment with equivalent performance
specifications can be substituted. In all cases, ensure that it is well calibration.
• DC power supply 100V/15A
• TEK scope with current probe TCM0030A
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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• Fluke 87 multimeter for input current
• 50dB 500W attenuator as load
• Spectrum analyzer: RIGOL DSA 815
• Power meter: GiGa 8542C
• Thermal meter, sensor is located at screw of copper coin
Note: The WPT test setup is normally a non-50Ω system. If the PA is tested under a non-50Ω system, the
measurement results may not correlate with 50Ω system due to the mismatch.
Hardware Operation
The following steps provide a guideline for proper hardware operation and configuration.
1)
First, set the current limit to 0.3A for the +5VDC supply feeding JP35 or JP28.
2)
Set the current limit to 1A for the HV DC supply feeding JP32 or JP28 at a voltage of between
+20VDC and +50VDC.
3)
Verify that all DC power supplies are turned off.
4)
Make sure the load is connected to JP56 or JP57.
5)
Verify the Class EF2 waveform via test points TP8, TP81 with JP32 +5VDC.
6)
Connect the VDD power supply to JP32 or JP28. Apply between +4V to +20VDC to JP32. Read the
output power at JP56 or JP57.
7)
Turn on the HV supply to the desired value. Do not exceed the absolute maximum voltage of
+100VDC. Keep the JP32 +5VDC on.
8)
To power the evaluation board down, reverse the steps above.
Measurement Technique
When measuring the high frequency content switch node, care must be taken to avoid long ground
leads. Measure the switch node by placing the oscilloscope probe tip at JP192 and JP193 (designed for
this purpose) or to the closest ground screws. Refer to Figure 15 for the proper probe technique.
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Figure 15 • Proper oscilloscope probe measurement technique
PA Performance without EMI filter
Power-on Procedure without EMI filter
• An additional heatsink may be required. The PA heatplate is provided with threaded hole
locations that can be used to attach the heatsink to the heatplate with 4-40 screws. To ensure
excellent thermal conduction, apply thermal grease to the PA / heatsink interface before
screwing the units together. Enough thermal grease should be applied so that a small amount
extrudes on all four sides as the screws are tightened. Wipe the assembly clean.
• Make sure jumpers JP5/JP43/JP6/JP44 are off
• Solder the wires with the SMA connector to JP56.
• Connect the load to JP56
• Plug the 5VDC supply into JP35. Pin 1: positive. Pin 2: negative. Turn the supply on and set the
DC input voltage to 5V
• Plug the HV supply into JP32. Pin 1: positive. Pin 2: negative. Turn the supply on and ramp the
voltage from 0V to 20V.
• Monitor the test point voltage by comparing the power meter measurement to GaN Systems’
test data which is available in Appendix A.
• If the measurements correlate, increase the HV supply to 60VDC.
• IMPORTANT: Ensure the 5VDC supply does not exceed 6V during testing.
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Evaluation Results-without EMI filter
The evaluation results for performance without an EMI filter are captured in Figures 16 through 20.
Figure 16 • Oscilloscope Plot Showing Both GS66508B Gate Node Signals at TP8, TP81
For a Class EF2 power amplifier topology, the optimal efficiency is achieved at a duty cycle of
approximately 35%. At that operating point, the PA can work under very ZVS wide impedance range
with high efficiency. The PA duty cycle is controlled by gate driver PE29102A. For a detailed time-delay
design please refer to Figure 8 and Figure 9. The total resistor value of R955/R965 dominates the dead
time of U86, and the delay time of U90 is controlled by R953/R952. Both two of PE29102A operate as
high side mode, low side of chip is disable, and to reduce inductance thru shortened length of trace
between gate of GS66508BP and PE29102A, the pins of low side output of PE29102A are removed in the
layout.
Typical waveforms at the device’s Drain node are shown in Figure 19. Channel 1 is shown in yellow and
channel 2 is shown in blue. At 77VDC input voltage, the output power is 150W before the EMI filter.
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Figure 17 • Oscilloscope Plot Showing Both GS66508B Drain Node Signals, without EMI filter
The ratio of maximum Drain voltage and input DC voltage is 2.33 which is ideal for a class EF2 amplifier.
This operating condition eliminates voltage stress on the transistors and has low second harmonics. The
output current shown in green, is not a perfect sinewave due to high order harmonics on the output load.
Switch mode Power Amplifiers have a lot of harmonics at the output. One significant advantage of the
Class EF2 topology is that it has a lower 2nd harmonic when compared to other PA topologies. This
advantage results in a Class EF2 PA with much better EMI performance.
Figure 18 shows the spectrum of the PA at 70W output power without an EMI filter. Compared to the
fundamental frequency, the 2nd harmonic is -35dBc, the 3rd harmonic is -20dBc, and the 4th harmonic is -
34dBc. This extremely low 2nd harmonic performance makes it much easier to filter out the PA’s high
order harmonic. This allows designers to meet EMI specifications and regulations without additional cost.
The PA’s output power and efficiency are shown in Figure 19. This PA delivers 93% efficiency at 70W
output power and 27VDC input voltage. This remarkable efficiency performance makes PA the best
candidate of the WPT systems, and particularly advantageous for high power applications such as drone,
autonomous robot and E-bike charging.
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Figure 18 • Spectrum Plot of output terminal JP56 SMA after 49.66dB attenuation at 300W output power.
Operation without an EMI filter.
Figure 19 • Output power and efficiency of PA without EMI filter at JP56 SMA
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Note: With the EMI filter, the maximum power level is limited to 300W, due to the 50Ω test.
The PA’s system reliability is optimized when the temperature rise of each device is kept to a minimum,
including that of the GaN E-HEMTs. The GS66508Bs are especially well suited in this regard, for a
number of reasons. First, they have very low switching losses which allows them to operate at high
efficiency and a low temperature rise at 6.78MHz, the common frequency used for resonant wireless
power transfer. Secondly, the bottom-side cooled GaNPX® packaging provides an extremely low
thermal impedance for efficient heat transfer to the heatsink, thereby drawing heat out of the device.
This GaN based design is able to operate over a wide ambient temperature and with convection cooling,
eliminating the need for cooling fans. These advantages support a PA design with excellent thermal
performance up to 300W output power.
The temperature plot of the PA design was measured and captured with a SEEK thermal camera and is
shown in Figure 20. The hottest devices are the first inductors, with the hottest inductor recording 35˚C
above ambient. The temperature rise of the GaN E-HEMTs, by comparison, is only 3˚C. Because the
GaN E-HEMTs run very cool, this allows operation over a very wide temperature range and extends
operation to a higher power level while simultaneously simplifying the cooling system design and
reducing the cost.
Figure 20 • Thermal measurement of PA without EMI filter at 300W output power
GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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PA Performance with EMI filter
Power-on Procedure with EMI filter
• An additional heatsink may be required. The PA heatplate is provided with threaded hole
locations that can be used to attach the heatsink to the heatplate with 4-40 screws. To ensure
excellent thermal conduction, apply thermal grease to the PA / heatsink interface before
screwing the units together. Enough thermal grease should be applied so that a small amount
extrudes on all four sides as the screws are tightened. Wipe the assembly clean.
• Make sure jumpers JP5/JP43/JP6/JP44 are on
• Do not attach a cable or wire to JP56.
• Connect the load to JP57.
• Plug 5VDC supply into JP35. Pin 1: positive. Pin 2: negative. Adjust the voltage to 5V.
• Plug the HV supply into JP32. Pin 1: positive. Pin 2: negative. Turn the supply on and ramp the
voltage from 0V to 20V
• Monitor the test point voltage by comparing the power meter measurement to GaN Systems’
test data which is available in Appendix A.
• If the measurements correlate, increase the HV supply to 60VDC.
• IMPORTANT: Ensure the 5VDC supply does not exceed 6V during testing.
• The optimized impedance of the current mode PA is around 30Ω. Using a 50Ω load will not
cause damage, however, the system will operate at a lower efficiency.
Evaluation Results-with EMI filter
For improved EMI performance, a filter can be used to reduce the higher order harmonics in each side of
the push-pull arm. Also, the addition of an EMI filter converts the PA from operating in voltage mode to
current mode, which provides a constant current for the WPT system.
The frequency spectrum of the PA is depicted in Figure 21. The 3rd harmonic rejection is around -58dBc,
with more than -60dBc rejection on high order harmonics. This outstanding performance will greatly help
the WPT system level EMI performance.
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GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Figure 21 • Spectrum plot of output terminal JP57 SMA after 49.66dB attenuation at 300W output power.
Operation with EMI filter
The output power and efficiency with an EMI filter are shown in Figure 22. This PA design delivers 88%
efficiency at 300W output power and 100VDC input voltage. This efficiency performance is lower than the
one of without EMI filter due to the loss id and mismatch loss from the EMI filter. The design of EMI filter
is optimal at 30 Ω, but the data is taken at 50 Ω.
Figure 22 • GSWP300W-EVBPA power (W) and efficiency (%) plotted against input voltage at 50Ω load
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The SEEK thermal camera photo of the PA is depicted in Figure 23. The thermal performance with EMI
filter is very impressive. The hottest points of the circuit are the two 2nd harmonics shunt inductors which
have a temperature rise of 35˚C. The temperature rise of the GaN devices is a modest 3˚C.
Figure 23 • Thermal measurement of PA with EMI filter at 300W output power
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Technical Resources
This document and additional technical resources are available for download from
www.gansystems.com.
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GaN E-HEMT Wireless Power Transfer Evaluation Board
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Appendix A:
Sample Test Data with and without EMI filter
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Please refer to the Evaluation Board/Kit Important Notice on page 27
Evaluation Board/kit Important Notice
GaN Systems Inc. (GaN Systems) provides the enclosed product(s) under the following AS IS conditions:
This evaluation board/kit being sold or provided by GaN Systems is intended for use for ENGINEERING
DEVELOPMENT, DEMONSTRATION, and OR EVALUATION PURPOSES ONLY and is not considered by GaN
Systems to be a finished end-product fit for general consumer use. As such, the goods being sold or provided are
not intended to be complete in terms of required design-, marketing-, and/or manufacturing-related protective
considerations, including but not limited to product safety and environmental measures typically found in end
products that incorporate such semiconductor components or circuit boards. This evaluation board/kit does not fall
within the scope of the European Union directives regarding electromagnetic compatibility, restricted substances
(RoHS), recycling (WEEE), FCC, CE or UL, and therefore may not meet the technical requirements of these directives,
or other related regulations.
If this evaluation board/kit does not meet the specifications indicated in the User’s Guide, the board/kit may be
returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE
EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES,
EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL
BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user
indemnifies GaN Systems from all claims arising from the handling or use of the goods. Due to the open construction
of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic
discharge.
No License is granted under any patent right or other intellectual property right of GaN Systems whatsoever. GaN
Systems assumes no liability for applications assistance, customer product design, software performance, or
infringement of patents or any other intellectual property rights of any kind.
GaN Systems currently services a variety of customers for products around the world, and therefore this
transaction is not exclusive.
Please read the User’s Guide and, specifically, the Warnings and Restrictions notice in the User’s Guide prior to
handling the product. Persons handling the product(s) must have electronics training and observe good
engineering practice standards.
This notice contains important safety information about temperatures and voltages. For further safety concerns,
please contact a GaN Systems’ application engineer.
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GaN E-HEMT Wireless Power Transfer Evaluation Board
User’s Guide
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Please refer to the Evaluation Board/Kit Important Notice on page 27
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www.gansystems.com
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death, or property or environmental damage. The information given in this document shall not in any event be regarded as a guarantee of performance. GaN Systems
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