EPC EPC9113 Quick Start Manual - Page 4

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QUICK START GUIDE

Single ended or Differential Mode operation

The EPC9509 amplifier can be operated in one of two modes; single-ended

or differential mode. Single ended operation offers higher amplifier

efficiency but reduced imaginary impedance drive capability. If the

reflected impedance of the tuned coil load exceeds the capability of

the amplifier to deliver the desired power, then the amplifier can be

switched over to differential mode. In differential mode, the amplifier is

capable of driving an impedance range of 1 Ω through 56 Ω and ±50j Ω

and maintains either the 800 mA

of power. The EPC9509 is set by default to differential mode and can be

switched to single ended mode by inserting a jumper into J75. When

inserted the amplifier operates in the single-ended mode. Using an

external pull down with floating collector/ drain connection will have

the same effect. The external transistor must be capable of sinking 25

mA and withstand at least 6 V. "

For differential mode only operation, the two ZVS inductors L

can be replaced by a single inductor L

ZVS Timing Adjustment

Setting the correct time to establish ZVS transitions is critical to

achieving high efficiency with the EPC9509 amplifier. This can be

done by selecting the values for R71, R72, R77, and R78 or P71, P72,

P77, and P78 respectively. This procedure is best performed using a

potentiometer installed at the appropriate locations that is used to

determine the fixed resistor values. The procedure is the same for both

single-ended and differential mode of operation. The timing MUST

initially be set WITHOUT the source coil connected to the amplifier.

The timing diagrams are given in Figure 10 and should be referenced

when following this procedure. Only perform these steps if changes

have been made to the board as it is shipped preset. The steps are:

1. With power off, remove the jumper in JP1 and install it into JP50 to

place the EPC9509 amplifier into Bypass mode. Connect the main

input power supply (+) to JP1 (bottom pin – for bypass mode) with

ground connected to J1 ground (-) connection.

2. With power off, connect the control input power supply bus (19 V) to

(+) connector (J1). Note the polarity of the supply connector.

3. Connect a LOW capacitance oscilloscope probe to the probe-hole

of the half-bridge to be set and lean against the ground post as shown

in Figure 9.

4. Turn on the control supply – make sure the supply is approximately 19 V.

5. Turn on the main supply voltage starting at 0 V and increasing to the

required predominant operating value (such as 24 V but NEVER

exceedthe absolute maximum voltage of 52 V).

6. While observing the oscilloscope adjust the applicable potentiometers

to so achieve the green waveform of Figure 10.

7. Repeat for the other half-bridge.

8. Replace the potentiometers with fixed value resistors if required

Remove the jumper from JP50 and install it back into JP1 to revert the

EPC9509 back to pre-regulator mode.

4 |

coil current or deliver up to 16 W

RMS

and L

ZVS1

and by removing C

and C

ZVS12

ZVS1

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Determining component values for L

The ZVS tank circuit is not operated at resonance, and only provides the

necessary negative device current for self-commutation of the output

voltage at turn off. The capacitors C

a very small ripple voltage component and are typically around 1 µF.

The amplifier supply voltage, switch-node transition time will determine

the value of inductance for L

ZVS operation over the DC device load resistance range and coupling

between the device and source coil range and can be calculated using

the following equation:

Where:

Δt

= Voltage Transition Time [s]

ZVS2

= Operating Frequency [Hz]

ZVS2

= Charge Equivalent Device Output Capacitance [F]

OSSQ

= Gate driver well capacitance [F]. Use 20 pF for the LM5113

well

that the amplifier supply voltage V

NOTE.

it is accounted for by the voltage transition time. The C

eGaN FETs is very low and lower than the gate driver well capacitance

which as a result must now be included in the ZVS timing calculation.

well

The charge equivalent capacitance can be determined using

the following equation:

OSSQ

To add additional immunity margin for shifts in coil impedance, the value

of L

can be decreased to increase the current at turn off of the devices

ZVS

(which will increase device losses). Typical voltage transition times range

from 2 ns through 12 ns. For the differential case the voltage and charge

) are doubled when calculating the ZVS inductance.

OSSQ

The Source Coil

Figure 4 shows the schematic for the source coil which is Class 3

A4WP compliant. The matching network includes both series and

shunt tuning. The matching network series tuning is differential to

allow balanced connection and voltage reduction for the capacitors.

The Device Board

Figure 5 shows the basic schematic for the device coil which is Category 3

A4WP compliant. The matching network includes both series and

shunt tuning. The matching network series tuning is differential to

allow balanced connection and voltage reduction for the capacitors.

The device board comes equipped with a kelvin connected output

DC voltage measurement terminal and a built in shunt to measure

the output DC current.

Two LEDs have been provided to indicate that the board is receiving

power with an output voltage greater than 4 V (green LED) and that

the board output voltage limit has been reached (greater than 36 V

using the red LED).

Demonstration System EPC9113

ZVS

and C

ZVS1

ZVS2

which needs to be sufficient to maintain

ZVSx

∆t

ZVS

8 ∙ f

∙ C

+ C

OSSQ

well

is absent from the equation as

AMP

∫

V AMP

∙

(v) ∙ dv

OSS

AMP

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are chosen to have

(1)

of the EPC2108

OSS

(2)