Doc #9300-0008 Rev 1
Directed Energy, Inc. 2002
3kW AND 5kW HALF-BRIDGE CLASS-D RF GENERATORS
AT 13.56MHz WITH 89% EFFICENCY AND LIMITED FREQUENCY AGILITY
Abstract
DEI / IXYS has developed an RF generator design for very high power at
a ISM frequency. of 13.56MHz, using a pair of DE375-102N12A
MOSFETS driven by DEIC420 gate drive ICs, in a half-bridge operating in
Class-D with limited frequency agility, to generate 3kW of output power at
83.5% efficiency. A pair of modules generates 5KW at 89% efficiency
using a total of four DE375-102N12A RF MOSFETs. This technical note
discussed the design of this RF generator and supporting SPICE models.
DIRECTED ENERGY, INC. TECHNICAL NOTE
Directed Energy, Inc.
A
n
IXYS
Company
2401 Research Blvd.
Suite 108
Fort Collins, CO USA 80526
TEL (970) 493-1901 FAX (970) 493-1903
EMAIL: deiinfo@directedenergy.com
www.directedenergy.com
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Doc #9300-0008 Rev 1
Directed Energy, Inc. 2002
INTRODUCTION
Many industrial processes require several kilowatts at one or more of the ISM
frequencies. In addition these generators often require some level of frequency agility.
Given this need DEI/IXYS has developed a prototype RF generator for very high power
RF at ISM frequencies. The prototype generator uses a pair of DE375-102N12A
MOSFETS driven by DEIC420 gate drive ICs in a half-bridge topology operating Class-
D at 13.56MHz. We have achieved a power output of 3KW at 83.5% efficiency. A pair of
modules generates 5KW at 89% efficiency using a total of four DE375-102N12A RF
MOSFETs. The design consists of three modules: The gate driver, half-bridge and the
output tank. The power output was adjusted via the high voltage supply. Frequency
adjustments are made via the input clock. In this paper we will discuss each of the three
key sections in detail as well as a complete system spice model. In addition in some
applications the generator must be capable of some frequency agility. This capability
allows some frequency adjustments to assist in the tuning operation. This topic will also
be addressed in each section. The first section is the gate driver.
GATE DRIVER (DEI Module #5040-0289B)
As in all high frequency topologies, the gate drive section is of vital importance. If the
gate driver is not capable of generating narrow gate pulses at high currents, the
system’s overall performance will be low. The gate driver presented here is a low-cost,
narrow band driver with frequency agility, designed to drive multiple MOSFET devices
for RF generator designs in the 2kW to > 10kW range.