IR21592_08

Not recommended for new designs - please refer to IRPLDIM3 IRPLDIM1E International Rectifier • 233 Kansas Street, El Segundo, CA 90245 USA IR21592 Dimming Ballast Control IC Design Kit Features ! ! ! ! ! ! ! ! Drives: 1 x 36W T8 Lamp Input: 185-265VAC/50Hz High Power Factor/Low THD High Frequency Operation Lamp Filament Preheating Lamp Fault Protection with Auto-Restart Brownout Protection IR21592 HVIC Ballast Controller Description The IRPLDIM1E is a high efficiency, high power factor, dimming electronic ballast designed for driving rapid start fluorescent lamp types. The design contains an EMI filter, active power factor correction and a ballast control circuit using the IR21592. This demo board is intended to ease the evaluation of the IR21592 Dimming Ballast Control IC, demonstrate PCB layout techniques and serve as an aid in the development of production ballast’s using the IR21592. IR21592 Dimming Ballast Block Diagram Line EMI Filter Rectifier PFC Output Stage Lamp IR21592 Interface Dim Input Half-Bridge Driver Dimming Feedback Preheat Feedback Lamp Fault www.irf.com 1 Electrical Characteristics Parameter Lamp Type Input Power (100%) Input Current (100%) Filament Preheat Current Preheat Mode Lamp Voltage Preheat Time Input AC Voltage Range Input DC Voltage Range Power Factor Total Harmonic Distortion Maximum Output Voltage Units [W] [Arms] [Arms] [Vrms] [s] [VACrms] [VDC] [%] [Vpk] Value (IRPLDIM1E) 36W T8 36 0.16 0.6 220 1.0 185..255/50..60Hz 250..350 0.98 12.5V and VDC > 5.1V and SD < 1.7V and TJ < 165C (UV+) (Bus OK) (Lamp OK) (T jmax) VCC < 10.9V (VCC Fault or Power Down) or VDC < 3.0V (dc Bus/ac Line Fault or Power Down) or SD > 2.0V (Lamp Fault or Lamp Removal) SD > 2.0V (Lamp Removal) or VCC < 10.9V (Power Turned Off) FAULT Mode Fault Latch Set 1/2-Bridge Off IQCC=240µA CPH=0V VCC=15.6V Oscillator Off T > 165C J (Over-Temperature) PREHEAT Mode 1/2-BridgeOscillator On VCSPK+VIPH (Peak Current Control) CPH Charging@I PH+1µA DIM+Open Circuit Over-Current Disabled CPH > 5.1V CS > V CSTH (1.6V) (Failure to Strike Lamp or Hard Switching) or T J > 165C (Over-Temperature) (End of PREHEAT Mode) IGNITION Mode fPH ramps to fMIN CPH Charging@I PH+1µA DIM=Open Circuit Over-Current Enabled CS > V (1.6V) CSTH (Over-Current or Hard Switching) or TJ > 165C VCS>VIPH(enable ignition detection) (Over-Temperature) then VCS 5kHz (2) I ign < I ignmax ICath1% ≥ ICathmin Table II, Ballast design constraints www.irf.com 7 IR2159 Programmable Inputs In order to program the MIN and MAX settings of the dimming interface, the phase of the output stage current at minimum and maximum lamp power must be calculated. This is obtained using the following equations:  4V  1− DC  V π  2 22  1 32P  1 1 32P % f% = − 2 % +  − 2 %  −4 4 4 2π LC C V% LC C V%  L2C2 2 This ballast design procedure has been summarized into the following 3 steps: Define Lamp Requirements Iterate L and C to fulfill constraints (8) Calculate IR2159 Programmable Inputs Figure 3, Simplified Ballast Design Procedure ϕ% = 180 −1 V 2P V23 % tan [( C − 2 L)2πf% −4 LCπ3 f%] 2P V% P π % % 2 % 2 % (9) Ballast Designer Software Included with the design kit is the Ballast Designer Software which allows for selection of different lamp types, different input voltage ranges or different lamp configurations. The software then performes all of the necessary design iterations and generates new schematics and a bill of materials. With the lamp requirements defined, the L and C of the ballast output stage selected, and the minimum and maximum phase calculated, the component values for setting the programmable inputs of the IR21592 are obtained with the following equations: RFMIN = (25e − 6) − ( f MIN − 10000) ⋅ (1e − 10) ( f MIN − 10000) ⋅ (2e − 14) [Ohms] (10) RCS = 2 ⋅ (1.6) I ign [Ohms] (11) RIPH = RFMIN RCS I ph 2 CCPH = ( 2 E − 7)(t PH ) [Ohms] (12) [Farads] (13) R MIN = R FMIN  ϕ 1%  1 −  4 45  [Ohms] (14) RMAX = 0.86 ⋅ RFMIN ⋅ RMIN [Ohms] (15)  ϕ100%  4 ⋅ RMIN − RFMIN ⋅ 1 −  45   www.irf.com 8 IRPLDIM1E Design Line Input Voltage: 185 to 265VAC/50/60Hz DC Bus Voltage: 400VDC Lamp Power/Type: 36W/T8 L C [mH] [nF] [Vpp] [kHz] [kHz] [App] [kHz] [Arms] V ph f ph f ign I ign f pmax I Cath P min 2.0 6.8 700 57 51 1.4 42 0.32 2.0 8.2 622 53 46 1.6 42 0.35 2.0 10 546 49 42 1.8 41 0.38 1) Lamp Requirements Typical high-frequency (25kHz) lamp requirements for the 36W/T8 lamp type are given as: Variable Value 0.6 1.0 600 1500 32 282 1 330 0.35 Units Arms s Vpp Vpp W Vpp W Vpp Arms I ph t ph V phmax Table IV, Ballast parameters for different C values. Vign Pmax VPmax Pmin VPmin I Cathmin Table III, 36W/T8 lamp requirements 2) Iterate L and C to Fulfill Constraints To select the ballast output stage inductor and capacitor, a range of values were inserted into equations (2) through (7), which have been summarized in the following table: When compared against the lamp requirements, a capacitor value of 6.8nF gives a lamp voltage during pre-heat that exceeds the maximum allowable specified for this lamp type. This can ignite the lamp before the cathodes have reached their emission temperature, drastically reducing lamp life. The pre-heat current can be reduced to give a lower pre-heat voltage, but the pre-heat time must then be increased for proper heating. Also, I Cathmin is too low, which will cause the lamp to extinguish at low light levels where the arc current alone is too low to heat the cathodes. Increasing the capacitor value to 10nF fulfills the lamp requirements quite well, even allowing some room in the pre-heat voltage for the pre-heat current to be increased and the pre-heat time shortened. During dimming, however, the lamp voltage increases with decreasing lamp power due to lamp negative incremental impedance effects. A maximum is reached around 10% brightness, after which the lamp voltage decreases as the lamp is further dimmed. The maximum filament current occurs at the maximum lamp voltage, which for a capacitor value of 10nF, is too high and will overheat the filaments. A capacitor value of 8.2nF was chosen which fulfills the lamp requirements without over-heating the cathodes. www.irf.com 9 3) IR21592 Programmable Inputs With all of the lamp requirements fulfilled, the component values for setting the programmable inputs of the IR21592 are calculated as: Equation No. (8) (8) (9) (9) (10) (11) (12) (13) (14) (15) Variable Value 46kHz 58kHz -56.12deg -89.27deg 33kOhm 0.8 Ohm 24kOhm 330nF 27kOhm 24kOhm f100% f1% ϕ100% ϕ 1% RFMIN RCS RIPH CTPH RMIN RMAX Table V, IR21592 Programmable Inputs for T8/36W lamp. Important Note: These design kits are intended as a demonstration of the functionality and performance of the IR21592 Dimming Ballast Control IC only. Adequate EMI filtering, line transient protection, galvanic dim control input isolation, and ballast and lamp life testing are not considered in this design. 10 www.irf.com Waveforms Figure 4 shows the voltage appearing across the lamp while Figure 5 shows the current flowing through the lamp during Startup, Preheat, Ignition and Dim modes. Figure 4, Lamp voltage during Startup, Preheat, Ignition and Dim (100%) Figure 5, Lamp current during Startup, Preheat, Ignition and Dim (100%) (100mA/div.) Normal Powerdown A Normal Powerdown occurs when the AC line voltage is disconnected from the ballast. When this occurs the voltage on the VDC pin of IC2 drops below the line fault threshold (3V) and IC2 shuts down in a controlled fashion. The oscillator is stopped, the half-bridge driver outputs (LO and HO) are turned off and capacitor CPH is discharged. IC2 also goes into its UVLO/micro-power mode and the bus voltage begins to collapse. Fault Mode Fault mode is when the ballast driver is shutdown due to the detection of a lamp fault. Note that when the ballast is in this Fault mode the power factor correction section of the ballast is also shutdown and the bus voltage will drop to the non-boosted/unregulated level. There are several lamp fault conditions which can put the ballast into the Fault mode. The lamp fault conditions detected include: near/below resonance (under-current) detection, hard-switching detection and over-current detection. Resistor RCS in the source lead of the low side MOSFET (M3) serves as the current sensing point for the half-bridge which is used to detect these lamp fault conditions. In operation when the half-bridge is oscillating, a voltage appears across RCS whenever the low side MOSFET, M3, is turned on or the high side MOSFET, M2, is turned off. The magnitude of this voltage directly relates to the current in the lamp resonant circuit. Figure 6 shows the voltage which appears across resistor RCS during normal Run mode conditions while Figure 14 shows the voltage appearing across the lamp during the end of Preheat mode, Ignition Ramp mode and the beginning of Run mode. Also shown in Figure 7 are the gate drive signals for the low side MOSFET (LO pin) and the high side MOSFET (HO-VS pin). www.irf.com 11 Figure 6, Normal Run mode, Upper trace: voltage across RCS, Middle trace: IC2 LO pin voltage, Lower trace: IC2 HO-VS pin voltage Figure 7, Normal lamp ignition: Lamp voltage during the end of Preheat mode, Ignition Ramp mode and the beginning of the Run mode During the Preheat mode the over-current protection is disabled. However, at the end of Preheat mode (the beginning of the Ignition mode) the hard-switching and over-current detection are enabled. If at any time thereafter the voltage magnitude across resistor RCS rises above the overcurrent threshold (1.6V) of the CS pin of IC2, a lamp fault condition is signaled and the half-bridge output MOSFETs’, (M2 and M3) are turned off and the ballast goes into Fault mode. This can happen if the lamp fails to ignite or if the upper filament is open. For failure to ignite the lamp, the current in the half-bridge increases and thus the voltage across resistor RCS increases above the over-current threshold signaling a fault. Figure 8 shows the voltage across resistor RCS and the voltage appearing across the lamp when the ballast detects a failure to ignite the lamp and goes into Fault mode. Figure 9 shows the voltage appearing across the lamp during the tail end of the Preheat mode and the Ignition mode for a failure of the lamp to ignite condition. If the upper filament is open, the halfbridge output hard-switches and each time the low side MOSFET (M3) is turned on a large current pulse occurs and thus a large voltage pulse occurs across resistor RCS signaling a fault, Figure 10 shows this hard-switching condition. Figure 11 shows the lamp voltage during the Preheat mode and beginning of Ignition Ramp mode for this hard-switching condition when the lamp fault condition is detected. The ballast will remain in Fault mode until either the line voltage is cycled or a lamp replacement is performed. 12 www.irf.com Figure 8, Failure of lamp to ignite condition (lamp filaments good): Upper trace: voltage across RCS, Lower trace: lamp voltage Figure 9, Failure of lamp to ignite condition (lamp filaments good): Lamp voltage during the end of Preheat and Ignition Ramp modes Figure 10, Hard-switching condition (upper trace filament open): Upper trace: voltage across RCS, Middle trace: IC2 LO pin voltage, Lower trace: IC2 HO-VS pin voltage Figure 11, Hard-switching condition (upper filament open): Lamp voltage during Preheat mode and beginning of Ignition Ramp mode when lamp fault is detected IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105 Data and specifications subject to change without notice. 8/8/2008 www.irf.com 13 REVISION HISTORY FOR REFERENCE DESIGN IRPLDIM1E Date August 8, 2008 Change Added “Not recommended for new designs – please refer to IRPLDIM3 14 www.irf.com