Solid State Amplifier Controller and Sequencer Jeff Millar, wa1hco

Solid State Amplifier Concept ● Control and protect SSA ● Metering and Display ● Separate Control box from Amplifier ● Relays in Amp or separate ● Directional coupler in Amp or separate ● Sequencing for Tower and Amp bypass relays ● Built in 28V supply ● relays ● ucontroller

SSA Block Diagram AmpAmp 28V AC Fwd Rev LPF Couple r RLY Relay Drive RLY Bypass PWR Switch 50V, 50A RF Input Antenna To Receiver Temp Arduino Uno Met er 20x4 LCD Controlle r

Controller Front Panel ● 28V power supply On/Off ● LCD display with backlight ● 20 character x 4 line LCD – State (initialize, standby, transmit, fault) – Drain Current – Drain Voltage (switched, current value) – Supply Voltage – Power Forward – Power Reflected – Temperature ● Analog meter for RF Power output ● Power Cycle to reset Fault LCD Mete r 1 Front wa1hco Transmit Id 35.6A Pf 1250W Vd 49.5V Pr 50W Vs 50.6V T 26.1C reflected Fault Id 0.0A Pf 0W Vd 0.0V Pr 0W Vs 50.7V T 26.1C

Controller Rear Panel Connectors ● Line Cord connector ● EMI filtered, IEC type ● DC Input ● 75 Amp, Powerpole, Blue/Black ● DC Output ● 75 Amp, Powerpole, Blue/Black ● Power Forward Sample ● Coax, SMA ● Power Reflected Sample ● Coax, SMA ● Tower Relay control ● DB-9, to tower mounted relays ● With lighting protection ● Amplifier Relay control ● DB-9, to in and out relays ● Amplifier temperature ● DB-9, to amp box ● Key ● RCA phono, ground to key Rea r Towe r Tem p Relay s Fw d Re f

SSA Control Board ● 4 x 3 inches ● Mounts to headers on Arduino Uno Processor ● PWB Contains ● 50 Amp DC power switch ● 50 Amp DC metering ● Fwd and Ref RF metering ● Vs and Vd metering ● Temp metering ● 28V Relay drivers with protection ● Arduino Software contains ● Fault detection every 2 msec ● Vd power switching ● Relay sequencing

Amplifier Control ● Electronically switched Vd ● Fast electronic circuit breaker on Vd ● Fold back current limit ● Trip in less than 100 usec ● Sense forward and reverse power ● Constant gate bias ● Keyed by closure to ground

Amplifier Power Switching ● LT1641 Hot Swap Controller ● Drive N channel FET as a high side switch ● Electronic circuit breaker ● Ramps voltage into capactive load ● Switch on Vd only when amplifier keyed ● Switch off Vd on Fault, over current ● IRF4368 HEXFET, Ohms Rs ● Ohm Current sense in SMT1210 package

Integral vs External Power Switch ● Integral ● smaller ● use wires to heat sink ● irregular shape to sink ● 2-4W in the transistor ● 1-2W in the resistors/ ● Separate ● More robust connections ● mounted on heat sink ● Connections ● Vs, Vd Studs – 50 Amp or more – Add wiring for control/meter ● Fet SWITCH gate – Filtered, protected ● Current sense Kelvin connections – two pins ● Components ● Heat sink ● 50V Studs ● Gate terminal with resistor, bypass, OVP ● Current sense terminals

Forward and Reverse Power ● High dynamic range RF detectors measure output forward and reverse power ● Directional couplers mounted with amplifier ● or part of separate LFP and Dir Coupler ● LTC5507 RF detectors mounted in SSAC ● Two small coax run from coupler to SSAC

Sequencer ● Key amplifier ● Amp in Standby – Vd off, Amp bypassed, Tower in Rx mode ● PTT pulled low – Switch Tower to Tx mode – switch output relay – Switch input relay – Switch on Vd ● Amp in Tx mode ● Un-key amplifier ● Amp in Tx mode – Vd on, Amp inline, Tower in Tx mode ● PTT pulldown released – Switch off Vd – Switch input relay – Switch output relay – Switch tower to Rx

Relay Control ● LT1161 quad relay drive IC ● Controls enhancement mode MOSFETS ● High Side switching ● Current limited