GEC PLESSEY RE EE WRT ee oo Tot : hat ra ci it cise ad Yaw atten) j LOLS LLO- + SK ow alae Latent SL443A ZERO VOLTAGE SWITCH The SL443A ts a symmetrical burst control integrated circuit in an 8-pin DIL plastic package and is mainly intended for manual heat control applications, for example cooker hot plates and powerful hair dryers SPECIAL FEATURES 1 Well defined load power/potentiometer placement characteristics 2. High immunity against spurious trac firing under noisy mains environment (automatic spike filtration) 3. Enables compliance with Cenelec EN50,006/ BS5406-1976 (A) Switching rate controlled (B) symmetrical burst control 4 Very low external component count 5 Tniac firing pulses inhibited whilst the |Cs power supply is being established dis- COMMON AC NPL wes TRIAC FIRING ALULSE 1 POT SLIDER Cr | PULSE DELAY CAPACITOR Ae IV) DP8 Fig 1 Pin connections - top view APPLICATIONS Me Cooker hotplates M Powerful hairdryers RAMP GENERATOR common pps at COMPARATOR Oo ] LOW Vor INHIBIT CIRCUIT p-- + 7V SPIKE PERIOD PULSE GENER ATOR ZERO VOLTAGE FILTER CROSSING DETECTOR OELAYED PULSE GENERATOR ! 7 SERIES STABILISER Pp-O + 7V Fig 2 SL443A block diagram 12ELECTRICAL CHARACTERISTICS Test conditions (unless otherwise stated): Tamo = 26C, All voltages measured with respect to common (pin 1) SL443A Value Characteristic Min. Typ. Max Units Conditions Shunt regulating voltage pin 3 147 V lg = 16mA Shunt regulating valtage pin 3 i6 Vv Is = 16mA Tamo = -75C Supply voltage trip level pin 3 122 Vv Supply current (less l1 AV, 2 < Is) See Note 1 72 mA Potentiometer supply pin 5, Vs 68 70 76 V Potentiometer resistance range 18 140 ko Triac gate drive pin4 Open circuit ON voltage 85 V Open circuit OFF voltage 01 V Output current into 2V drain 80 100 mA Output current into 4V drain 50 70 mA Output current into short circuit 200 mA Internal drain resistance 800 Q Control input pin 8 Bias current 1 nA Internal reference ramp Start 03 05 O07 ~ ramp finish Vs- O05] Vs-03 | Vs- 01 * Period of ramp generator - T 27 30 33 5 (Re =100K,C, =0.68p) (RMS mains voltage=220v) Pin 6 output impedance R6 215 27 325 kQ @ The supoly current 045 x (RMS current fed into Pin 2) *& Pernod of ramo = T =2xC-x Rex (RMS mains voltage) seconcs ABSOLUTE MAXIMUM RATINGS Voltages Voltage on pin 8, Va-1 Max 10v Voltage on pin 4, Va-1 Max 10v Currents Supply current, pin 2 peak value =< lam Max 50mA Non-repetitive peak current (tp 2 250uS) x lasm Max 200mA Output current, pin 5 I5 Short circuit protected Output current, pin 4, average value la (AV) Max 10mA Short circuit protected Temperatures Operating ambient temperature Tamb 10to 75 C Storage temperature Tstc 55 to +125 C Power Dissipation See Fig 3 13SL443A CIRCUIT DESCRIPTION The externally current iimited AC supply is applied to the device, and rectification followed by shunt regulation provides a 14V DC supply This is externally smoothed before application to the 7.0V series stabiliser which feeds the resistance bridge The stabiliser must be within regulation, or operation of the Low Vcc Inhibit circurt will result. This circuit overrides all other circuitry and prevents unsuitable firing pulses from being supplied to the triac at switch-on The current limited AC supply also drives the Period Pulse Generator (PPG) and zero voltage crossing circuits The PPG produces a single short duration pulse for each completed mains cycle and serves two purposes. Firstly it is used to clock logic information such that the circuit behaves 1n a symmetrical manner and only complete mains cycles are applied to the load. Secondly the pulse is used to switch timing components in the ramp generator and this enables long time constants to be achieved without having to resort to the use of electrolytic capacitors The zero voltage crossing detector contrals a pulse generator that has a delayed output. The delay !s necessary since, with loads that are slightly inductive or low power resistive, the tnac load current may not reach its required holding level at zero voltage point Both delay and pulse duration are defined by an external capacitor and this further serves the purpose of filtering out spikes which occur in the zero crossing region. Automatic rejection takes place of spikes having a duration of up to 50 per cent of the normal width of the triac firing pulse The comparator amplifier has differential inputs and these are used to compare the potential appearing on the slider of the control potentiometer with that of the ramp waveform. The output of thts amplifier controis the logic circuitry and the potentiometer setting defines the fraction of the ramp period for which the trac Is in conduction so controlling the power in the load 60 l ! | 200 + ! I ! 1 Riny-a2 200 C/W ~ 1804 | = t E ! _ l l = 1004 a ] I | | 50 4 I | I I 9 r 7 F sa 100 15a Tama (C) Fig 3 Power dissipation 14 AC MAINS uy iF WAFEFORM " ul i It I My Woy i ett ! Thy i wets i tl wn ' " | ry | ay Il wn hat I it " it lit i i" wii nL n y a QuTPUT OF a iv M Hh PERIOO Mh NW Ht Wy PULSE lt uw Lt GENERATOR T tl t u " t iu it a wt output oF { ZERO 1 CROSSING ! PULSE GENERATOR | Y EXPANQEO | EXPANOED \ ZERO \ CROSSING | | PERIOD PULSE 4 ! lasy FIRING | | PULSE 1 1 \ 1 | | ~~ ty 0 69RC C#CO CAPACITOR CONNECTED TO PIN 6 Rs Ping OUTPUT IMPEDANCE AS) Fig 4 Pulse timingSL443A 1 Control ts effected by varying the number of complete mains cycles applied to the load in the fixed timing | ! ! period T \ ' i \ | i S t | | LN NA fA A AA V7 TITTY | \ i | ' \ 1 | ' ' ' | 4 ZERQ POWER l INTERMEDIATE POWER I MAXIMUM POWER l t 1 | 1 ' i ' INTERNAL RAMP eo VOLTAGE REFERENCE Fig 5 Methad of contro! 15 TYSL443A Application Circuits INCREASE POWER Ap 5 ie 2kW SL GAIA 220V s \o*r. Rp LOAD Hz y |__|] -__+ SL443A Cs nm 220V = 10% 8 |__| Cp MT2 50Hz | _ Component values Ro 82k 5% 7W Re 100kKQ (Control characteristic of linear potentiometer ig shown 1n Fig 3) Cs 220uF 16V Cr 047uF (Ramp penod = 20 seconds nominal) Co 15nF+ 10% TRIAC TAG 255 - 400 wee ee ~ sa. VIN = 0-7V 1 kt TRIAC Cr G/ (Tt | Fig 1 Cooker hotplate control Component values Ro 9.2kQ 5% 7W Rp 100k2 Cs 220pF 16V Ct 047yF (Ramp penod = 20 seconds nominal) Co 15nF 10% TRIAC TAG 255 400 Fig 2 Voitage control 100 PERCENTAGE POWER 0 4 } 4 93 100 PEACENTAGE POTENTIOMETER TRAVEL 7 67V VOLTAGE o5v av This characteristic applies to a linear potentiameter Different contro! characteristics are easily obtained by using a non-linear potentiometer and/or offset resistors in the potentiometer circult __ Fig 3 Output power v potentiometer disolacement or voltage on pin 8 54