Gan Systems GSWP300W-EVBPA User manual

GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
Technical Manual
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 220215 © 2022 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
Technical Manual
Visit www.gansystems.com for the latest version of this technical manual.

GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
Technical Manual
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GSWP300W-EVBPA Rev 220215 © 2022 GaN Systems Inc. www.gansystems.com 2
Please refer to the Evaluation Board/Kit Important Notice on page 27
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
Technical Manual
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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
Technical Manual
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 220215 © 2022 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 Technical Manual 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
Technical Manual
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GSWP300W-EVBPA Rev 220215 © 2022 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
Technical Manual
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 220215 © 2022 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
Technical Manual
_____________________________________________________________________________________________________________________
GSWP300W-EVBPA Rev 220215 © 2022 GaN Systems Inc. www.gansystems.com 7
Please refer to the Evaluation Board/Kit Important Notice on page 27
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
Technical Manual
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GSWP300W-EVBPA Rev 220215 © 2022 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
Technical Manual
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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
Technical Manual
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GSWP300W-EVBPA Rev 220215 © 2022 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
Technical Manual
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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
J32
HV DC Input

GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
Technical Manual
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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
Technical Manual
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GSWP300W-EVBPA Rev 220215 © 2022 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
100VDC 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.
• Maximum LV supply input operating voltage of 7VDC

GSWP300W-EVBPA
GaN E-HEMT Wireless Power Transfer Evaluation Board
Technical Manual
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• 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

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GaN E-HEMT Wireless Power Transfer Evaluation Board
Technical Manual
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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
Technical Manual
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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-50Ωsystem, 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 J28.
2) Set the current limit to 1A for the HV DC supply feeding J32 or J28 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 J32 +5VDC.
6) Connect the VDD power supply to J32 or J28. Apply between +4V to +20VDC to J32. 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 J32 +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
Technical Manual
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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 J32. 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
Technical Manual
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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
Technical Manual
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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
Technical Manual
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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
Note: With the EMI filter, the maximum power level is limited to 300W, due to the 50Ω test.