July 2000 PRELIMINARY ML4833* Electronic Dimming Ballast Controller GENERAL DESCRIPTION FEATURES The ML4833 is a complete solution for a dimmable or a non-dimmable, high power factor, high efficiency electronic ballast. The BiCMOS ML4833 contains controllers for “boost” type power factor correction as well as for a dimming ballast. The ML4833 was designed to minimize the number of external components required to build an electronic ballast. ■ The PFC circuit uses a new, simple PFC topology which requires only one loop for compensation. This system produces a power factor of better than 0.99 with low input current THD. An overvoltage protection comparator inhibits the PFC section in the event of a lamp out or lamp failure condition. The ballast controller section provides for programmable starting sequence with individually adjustable preheat and lamp out-of-socket interrupt times. The IC controls lamp output power through feedback. The ML4833 provides a power down input which reduces power to the lamp, for GFI, end of life, etc. ■ ■ ■ ■ ■ ■ ■ ■ ■ Complete power factor correction and dimming ballast control in one IC Low distortion, high efficiency continuous boost, peak current sensing PFC section Programmable start scenario for rapid or instant start lamps Lamp current feedback for dimming control Variable frequency dimming and starting Programmable restart for lamp out condition to reduce ballast heating Internal over-temperature shutdown replaces external heat sensor PFC overvoltage comparator eliminates output “runaway” due to load removal Low start-up current <0.5mA Power reduction pin for end of life and GFI detectors (* Indicates part is End Of Life as of July 1, 2000) BLOCK DIAGRAM INTERRUPT 6 7 RSET RT /CT LAMP FB VARIABLE FREQUENCY OSCILLATOR LFB OUT 8 4 5 OUTPUT DRIVERS 9 RX/CX PRE-HEAT AND INTERRUPT TIMERS OUT A CONTROL & GATING LOGIC OUT B 3 PDWN PFC OUT 10 2 1 18 14 13 15 CRAMP PIFB PEAO PVFB/OVP PGND POWER FACTOR CONTROLLER VCC UNDER-VOLTAGE AND THERMAL SHUTDOWN VREF GND 12 16 17 11 1 ML4833 PIN CONFIGURATION ML4833 18-Pin DIP (P18) PEAO PIFB PDWN LAMP FB LFB OUT RSET RT/CT INTERRUPT RX/CX 1 18 2 17 3 16 4 15 5 14 6 13 7 12 8 11 9 10 ML4833 18-Pin SOIC (S18) PEAO 1 18 PVFB/OVP PIFB 2 17 VREF PDWN 3 16 VCC LAMP FB 4 15 PFC OUT LFB OUT 5 14 OUT A OUT B RSET 6 13 OUT B P GND RT/CT 7 12 P GND INTERRUPT 8 11 GND RX/CX 9 10 CRAMP PVFB/OVP VREF VCC PFC OUT OUT A GND CRAMP TOP VIEW TOP VIEW PIN DESCRIPTION PIN# NAME 1 PEAO PFC error amplifier output and compensation node. 2 PIFB Sensing of the inductor current and peak current sense point of the PFC cycle by cycle current limit comparator. 3 PDWN A one volt comparator threshold that switches the operating frequency to the preheat frequency when exceeded. 4 LAMP FB Inverting input of an error amplifier used to sense (and regulate) lamp arc current. Also the input node for dimming control. 5 2 FUNCTION LFB OUT PIN# NAME FUNCTION 8 INTERRUPT Input used for lamp-out detection and restart. A voltage less than 1.25 volts resets the chip and causes a restart after a programmable interval. 9 RX/CX Sets the timing for the preheat, dimming lockout, and interrupt. 10 CRAMP Integrated voltage of the error amp out. 11 GND Ground. 12 P GND Power ground for the IC. 13 OUT B Ballast MOSFET drive output. 14 OUT A Ballast MOSFET drive output. Output of the lamp current error transconductance amplifier used for lamp current loop compensation. 15 PFC OUT Power Factor MOSFET drive output. 16 VCC Positive supply for the IC. 6 RSET External resistor which sets oscillator FMAX, and R(X)/C(X) charging current. 17 VREF Buffered output for the 7.5V voltage reference. 7 RT/CT Oscillator timing components. 18 PVFB/OVP Inverting input to PFC error amplifier and OVP comparator input. ML4833 ABSOLUTE MAXIMUM RATINGS Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. Supply Current (ICC) ............................................... 60mA Output Current, Source or Sink (OUT A, OUT B, PFC OUT) DC ......................... 250mA Output Energy (capacitive load per cycle).............. 1.5 mJ Analog Inputs (LAMP FB, INTERRUPT, VCC) ........... –0.3V to VCC –2V PIFB input voltage ......................................... –1.5V to 2V Maximum Forced Voltage (PEAO, LFB OUT) ................................... –0.3V to 7.7V Maximum Forced Current (PEAO, LFB OUT) ........ ±20mA Junction Temperature ............................................ 150°C Storage Temperature Range ..................... –65°C to 150°C Lead Temperature (Soldering 10 sec.) .................... 260°C Thermal Resistance (qJA) ML4833CP ...................................................... 70°C/W ML4833CS .................................................... 100°C/W OPERATING CONDITIONS Temperature Range ........................................ 0°C to 85°C ELECTRICAL CHARACTERISTICS Unless otherwise specified, RSET = 22.1ký, RT = 15.8kW, CT = 1.5nF, CVCC = 1µF, VCC = 12.5V. (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS –0.3 –1.0 µA 65 105 µW 5.0 V 0.2 0.4 V 7.1 7.5 7.8 V Lamp Current Amplifier (LAMP FB, LFB OUT) Small Signal Transconductance 35 Input Voltage Range –0.3 W Input Bias Current Output Low Voltage at LAMP FB = 3V, RL = Output High Voltage at LAMP FB = 2V, RL = Source Current Voltage at LAMP FB = 0V, LFB OUT = 7V, TA = 25°C –0.05 –0.15 –0.25 mA Voltage at LAMP FB = 5V, LFB OUT = 0.3V, TA = 25°C 0.05 0.12 0.22 mA –0.3 –1.0 µA 65 105 µW 5.0 V 0.2 0.4 V 6.5 6.8 7.1 V Sink Current PFC Voltage Feedback Amplifier (PEAO, PVFB/OVP) Small Signal Transconductance 35 Input Voltage Range –0.3 W Input Bias Current Output Low Voltage at PVFB = 3V, RL = Output High Voltage at PVFB = 2V, RL = Source Current Voltage at PVFB/OVP = 0V, PEAO = 6V, TA = 25°C –0.05 –0.15 –0.25 mA Voltage at PVFB/OVP = 3V, PEAO = 0.3V, TA = 25°C 0.03 0.07 0.16 mA –0.90 –1.05 –1.15 V Sink Current PFC Current — Limit Comparator (PIFB) Current-Limit Threshold Propagation Delay 100mV step and 100mV overdrive 100 ns Oscillator Initial Accuracy TA = 25°C Voltage Stability VCCZ – 4.5V < VCC <VCCZ – 0.5V 72 Temperature Stability Total Variation Ramp Valley to Peak Line, temperature 76 80 kHz 1 % 2 % 69 83 2.5 kHz V 3 ML4833 ELECTRICAL CHARACTERISTICS PARAMETER (Continued) CONDITIONS MIN TYP MAX UNITS Voltage at LAMP FB = 3V, RT/CT = 2.5V, RX/CX = 0.9V (Preheat) –90 –110 –130 µA LAMP FB = 3V, RT/CT = 2.5V, RX/CX = Open –180 –220 –260 µA 4.0 5.5 7.0 mA 0.65 1 1.35 µs 7.4 7.5 7.6 V Oscillator (Continued) CT Charging Current CT Discharge Current Voltage at RT/CT = 2.5V Output Drive Deadtime Reference Section Output Voltage TA = 25°C, IO = 1mA Line regulation VCCZ – 4.5V < VCC < VCCZ – 0.5V 2 35 mV Load regulation 1mA < IO < 5mA 2 15 mV Temperature stability 0.4 7.35 % Total Variation Line, load, temp 7.65 V Output Noise Voltage 10Hz to 10kHz 50 µV Long Term Stability TJ = 125°C, 1000 hrs 5 mV Initial Preheat Period 0.8 s Subsequent Preheat Period 0.7 s Start Period 1.2 s Interrupt Period 5.7 s Preheat and Interrupt Timer (RX/CX where RX = 680ký, CX = 4.7µF) RX/CX Charging Current RX/CX Open Circuit Voltage VCC < Start-up threshold RX/CX Maximum Voltage Input Bias Current –24 –28 –33 µA 0.4 0.7 1.0 V 7.0 7.3 7.7 V 0.1 µA Voltage at CRAMP = 1.2V Preheat Lower Threshold 1.05 1.22 1.36 V Preheat Upper Threshold 4.2 4.7 5.1 V Interrupt Recovery Threshold 1.05 1.22 1.36 V Start Period End Threshold 6.05 6.6 7.35 V 1.1 1.22 1.4 V 0.1 µA Interrupt Input (INTERRUPT) Interrupt Threshold Input Bias Current RSET Voltage 2.4 2.5 2.6 V OVP Threshold 2.63 2.73 2.83 V Hysteresis 0.18 0.23 0.27 V OVP Comparator (PVFB/OVP) Propagation Delay 4 1.4 µs ML4833 ELECTRICAL CHARACTERISTICS (Continued) PARAMETER CONDITIONS MIN TYP MAX UNITS IOUT = 20mA 0.1 0.2 V IOUT = 200mA 1.0 2.0 V Outputs (OUT A, OUT B, PFC OUT) Output Voltage Low Output Voltage High IOUT = –20mA VCC – 0.2 VCC – 0.1 V IOUT = –200mA VCC – 2.0 VCC – 1.0 V Output Voltage Low in UVLO IOUT = 10mA, VCC < Start-up threshold Output Rise/Fall Time CL = 1000pF 0.2 20 V ns Under-Voltage Lockout and Bias Circuits IC Shunt Protection Voltage (VCCZ) ICC = 15mA Start-up Current Operating Current 14.2 15.0 15.8 V VCC - Start-up threshold 0.34 0.48 mA VCC = 12.5V, Voltage at LAMP FB = 0V, LFB OUT = 2.3, PVFB/OVP = 2.3V PIFB = Open 5.5 8.0 mA Start-up Threshold VCC – 1.2 VCCZ – 1.0 VCC – 0.8 V Shutdown Threshold VCC – 5.3 VCCZ – 4.8 VCC – 4.3 V 130 °C 30 °C Shutdown Temperature (TDWN) (Note 2) Hysteresis (TDWN) PDWN PDWN Threshold Note 1: Note 2: 0.9 1.0 1.1 V Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions. Junction temperature. 5 ML4833 FUNCTIONAL DESCRIPTION compensation is needed), an integrator, a comparator, and a logic control block. In the boost topology, power factor correction is achieved by sensing the output voltage and the current flowing through the current sense resistor. Duty cycle control is achieved by comparing the integrated voltage signal of the error amplifier and the voltage across RSENSE. The duty cycle control timing is shown in Figure 2. Setting minimum input voltage for output regulation can be achieved by selecting CRAMP according to equation 1. OVERVIEW The ML4833 consists of peak current controlled continuous boost power factor front end section with a flexible ballast control section. Start-up and lamp-out retry timing are controlled by the selection of external timing components, allowing for control of a wide variety of different lamp types. The ballast section controls the lamp power using frequency modulation (FM) with additional programmability provided to adjust the VCO frequency range. This allows for the IC to be used with a variety of different output networks. Figure 1 depicts a detailed block diagram of ML4833. CRAMP = LFB OUT RSET RT/CT OSC + CLK 9 16 17 11 RX/CX VCC VREF 18 1 10 + PREHEAT TIMER – 1.25V GND S PDWN 4 8 3 1.0V Q + – V TO I PVFB/OVP LAMP FB + – 5 2.5V INTERRUPT – UNDER-VOLTAGE THERMAL SHUTDOWN REFOK 2.5V (1) The OVP pin serves to protect the power circuit from being subjected to excessive voltages if the load should change suddenly (lamp removal). A divider from the high voltage DC bus sets the OVP trip level. When the voltage on PVFB/OVP exceeds 2.75V, the PFC transistor are inhibited. The ballast section will continue to operate. The ML4833 power factor section is a peak current sensing boost mode PFC control circuit in which only voltage loop compensation is needed. It is simpler than a conventional average current control method. It consists of a voltage error amplifier, a current sense amplifier (no 7 } OVERVOLTAGE PROTECTION AND INHIBIT POWER FACTOR SECTION 6 { PEAOMAX 1 (1− D)Ts − 1.1µs 22K 2P OUT − VOUT − 2VIN (1− D)Ts 8R SENSE 2L VIN – R + PEAO CRAMP PFC OUT – 2.75V OVP S + Q OUT A 15 14 R T Q –1.0V – + 2 PIFB ILIM PGND ISENSE AMPLIFIER Figure 1. ML4833 Detailed Block Diagram 6 OUT B 13 12 ML4833 TRANSCONDUCTANCE AMPLIFIERS The PFC voltage feedback amplifier is implemented as an operational transconductance amplifier. It is designed to have low small signal forward transconductance such that a large value of load resistor (R1) and a low value ceramic capacitor (<1µF) can be used for AC coupling (C1) in the frequency compensation network. The compensation network shown in Figure 3 will introduce a zero and a pole at: fZ = 1 2π R1C1 fP = 1 2π R1C2 PVFB/OVP 18 – 2.5V + R1 C2 C1 (2) Figure 3. Compensation Network L VOUT SW2 RA EMI FILTER LAMP NETWORK INVERTER RSENSE 2 PIFB OUT A SINE –A RB SW1 14 18 L A M P L A M P PVFB/OVP + R Q – S SINE CLK OSC RAMP PEAO – V TO I + VREF1 CLK PFC OUT 10 1 CRAMP PEAO R1 CRAMP C2 C1 Figure 2. ML4833 PFC Controller Section 7 ML4833 Figure 4 shows the output configuration for the operational transconductance amplifiers. CURRENT MIRROR IN OUT IQ + IQ – OSCILLATOR The VCO frequency ranges are controlled by the output of the LFB amplifier (RSET). As lamp current increases, LFB OUT falls in voltage, causing the CT charging current to increase, thereby causing the oscillator frequency to increase. Since the ballast output network attenuates high frequencies, the power to the lamp will be decreased. gmVIN 2 io = gmVIN gmVIN 2 17 VREF VREF IN OUT RT/CT CURRENT MIRROR CONTROL ICHG RT + 7 1.25/3.75 – CT Figure 4. Output Configuration 5.5mA A DC path to ground or VCC at the output of the transconductance amplifiers will introduce an offset error. The magnitude of the offset voltage that will appear at the input is given by VOS = io/gm. For an io of 1µA and a gm of 0.05 µW the input referred offset will be 20mV. Capacitor C1 as shown in Figure 3 is used to block the DC current to minimize the adverse effect of offsets. W Slew rate enhancement is incorporated into all of the operational transconductance amplifiers in the ML4833. This improves the recovery of the circuit in response to power up and transient conditions. The response to large signals will be somewhat non-linear as the transconductance amplifiers change from their low to high transconductance mode. This is illustrated in Figure 5. iO CLOCK tDIS tCHG VTH = 3.75V CT VTL = 1.25V Figure 6. Oscillator Block Diagram and Timing VIN Differential 0 Linear Slope Region The oscillator frequency is determined by the following equations: FOSC = 1 t CHG + tDIS (3) and Figure 5. Transconductance Amplifier Characteristics BALLAST OUTPUT SECTION The IC controls output power to the lamps via frequency modulation with non-overlapping conduction. This means that both ballast output drivers will be low during the discharging time tDIS of the oscillator capacitor CT. 8 V + I R − VTL t CHG = R T CT In REF CH T VREF + ICH R T − VTH (4) The oscillator’s minimum frequency is set when ICH = 0 where: FOSC ≅ 1 0.51× R T CT (5) ML4833 This assumes that tCHG >> tDIS. TJ ≅ TA + (PD + 65°C / W) When LFB OUT is high, ICH = 0 and the minimum frequency occurs. The charging current varies according to two control inputs to the oscillator: (9) VCC VCCZ 1. The output of the preheat timer V(ON) 2. The voltage at LFB OUT (lamp feedback amplifier output) V(OFF) In preheat condition, charging current is fixed at ICHG (PREHEAT) = 2.5 RSET (6) In running mode, charging current decreases as the voltage rises from 0V to VOH at the LAMP FB amplifier. The highest frequency will be attained when ICHG is highest, which is attained when voltage at LFB OUT is at 0V: ICHG(0) = 5 RSET (7) Highest lamp power, and lowest output frequency are attained when voltage at LFB OUT is at its maximum output voltage (VOH). 5.5mA 0.34mA t Figure 7. Typical VCC and ICC Waveforms when the ML4833 is Started with a Bleed Resistor from the Rectified AC Line and Bootstrapped from an Auxiliary Winding. STARTING, RE-START, PREHEAT AND INTERRUPT In this condition, the minimum operating frequency of the ballast is set per equation 5 above. For the IC to be used effectively in dimming ballasts with higher Q output networks a larger CT value and lower RT value can be used, to yield a smaller frequency excursion over the control range (voltage at LFB OUT). The discharge current is set to 5mA. Assuming that IDIS >> IRT: tDIS(VCO) ≅ 600 × CT t ICC (8) IC BIAS, UNDER-VOLTAGE LOCKOUT AND THERMAL SHUTDOWN The IC includes a shunt clamp which will limit the voltage at VCC to 15V (VCCZ). The IC should be fed with a current limited source, typically derived from the ballast transformer auxiliary winding. When VCC is below VCCZ – 1.1V, the IC draws less than 0.48mA of quiescent current and the outputs are off. This allows the IC to start using a “bleed resistor” from the rectified AC line. To help reduce ballast cost, the ML4833 includes a temperature sensor which will inhibit ballast operation if the IC’s junction temperature exceeds 120°C. In order to use this sensor in lieu of an external sensor, care should be taken when placing the IC to ensure that it is sensing temperature at the physically appropriate point in the ballast. The ML4833’s die temperature can be estimated with the following equation: The lamp starting scenario implemented in the ML4833 is designed to maximize lamp life and minimize ballast heating during lamp out conditions. The circuit in Figure 8 controls the lamp starting scenarios: Filament preheat and lamp out interrupt. CX is charged with a current of IR(SET)/4 and discharged through RX. The voltage at CX is initialized to 0.7V (VBE) at power up. The time for CX to rise to 4.8V is the filament preheat time. During that time, the oscillator charging current (ICHG) is 2.5/RSET. This will produce a high frequency for filament preheat, but will not produce sufficient voltage to ignite the lamp or cause significant glow current. After cathode heating, the inverter frequency drops to FMIN causing a high voltage to appear to ignite the lamp. If lamp current is not detected when the lamp is supposed to have ignited, the lamp voltage feedback coming into pin 8 remains below 1.25V, the CX charging current is shut off and the inverter is inhibited until CX is discharged by RX to the 1.2V threshold. Shutting off the inverter in this manner prevents the inverter from generating excessive heat when the lamp fails to strike or is out of socket. Typically this time is set to be fairly long by choosing a large value of RX. 9 ML4833 A summary of the operating frequencies in the various operating modes is shown below. 0.625 RSET RX/CX + 9 Operating Mode Operating Frequency Preheat [F(MAX) to F(MIN)] 2 Dimming Lock-out F(MIN) Dimming Control F(MIN) to F(MAX) HEAT CX 1.2/4.8 – RX 6.8 + 1.2/6.8 – 1.25V – INHIBIT R INTERRUPT 8 DIMMING LOCKOUT Q S + TYPICAL APPLICATIONS Figure 8. Lamp Preheat and Interrupt Timers LFB OUT is ignored by the oscillator until CX reaches 6.8V threshold. The lamps are therefore driven to full power and then dimmed. The CX pin is clamped to about 7.5V. Figure 10 shows a schematic for a dimming power-factor corrected 60W ballast, designed to operate two F32T8 fluorescent lamps connected in series. 6.8 4.8 RX/CX 1.2 .65 0 HEAT DIMMING LOCKOUT >1.25 INT INHIBIT Figure 9. Lamp Starting and Restart Timing 10 PDWN NEUTRAL 220 VAC HOT F1 T1 C24 R4 3 4 C7 L2 L1 C3 C1 R8 R3 R1 D4 D3 C4 D2 R5 C4 R2 D6 D5 C6 9 6 D9 R7 R6 D10 Q1 9 8 7 6 5 4 3 2 1 + R22 C20 Q1 D7 VCC VREF PVFB PGND RTC T TP3 RXCX C2 R5 R15 R23 CRAMP GND OUT B RSET INTERRUPT OUT A LFB OUT R4 C3 C13 10 11 12 13 14 15 16 17 18 R8 C10 PFC OUT U1 LAMP FB PDWN PIFB PEAO ML4833 T1 R10 D12 C5 8 10 C25 D13 R20 C26 D2 D1 DIMMER CONTROL INTERFACE SUBASSEMBLY D1 C11 R25 R14 C2 C1 D8 R3 R13 R12 R11 6 5 2 3 C14 – + – + 8 4 U2 C15 R16 R7 R6 C16 7 1 R1 C12 C19 7 6 8 1 2 3 R19 C17 T2 TP2 TP1 R18 R17 Q3 U1 R2 Q2 R21 R24 GRAY C8 7 6 C21 D11 VIOLET C22 TP4 1 9 8 2 3 4 5 1 T5 6 10 C23 REMOTE MANUAL DIMMER 0–10VDC TP5 C9 T4 B B Y Y R R ML4833 Figure 10. 220V Dimming Ballast 11 ML4833 PHYSICAL DIMENSIONS inches (millimeters) Package: P18 18-Pin PDIP 0.890 - 0.910 (22.60 - 23.12) 18 0.240 - 0.260 0.295 - 0.325 (6.09 - 6.61) (7.49 - 8.26) PIN 1 ID 1 0.045 MIN (1.14 MIN) (4 PLACES) 0.050 - 0.065 (1.27 - 1.65) 0.100 BSC (2.54 BSC) 0.015 MIN (0.38 MIN) 0.170 MAX (4.32 MAX) SEATING PLANE 0.016 - 0.022 (0.40 - 0.56) 0.125 MIN (3.18 MIN) 0º - 15º 0.008 - 0.012 (0.20 - 0.31) Package: S18 18-Pin SOIC 0.449 - 0.463 (11.40 - 11.76) 18 0.291 - 0.301 0.398 - 0.412 (7.39 - 7.65) (10.11 - 10.47) PIN 1 ID 1 0.024 - 0.034 (0.61 - 0.86) (4 PLACES) 0.050 BSC (1.27 BSC) 0.095 - 0.107 (2.41 - 2.72) 0º - 8º 0.090 - 0.094 (2.28 - 2.39) 12 0.012 - 0.020 (0.30 - 0.51) SEATING PLANE 0.005 - 0.013 (0.13 - 0.33) 0.022 - 0.042 (0.56 - 1.07) 0.009 - 0.013 (0.22 - 0.33) ML4833 ORDERING INFORMATION PART NUMBER ML4833CP (End of Life) ML4833CS (Obsolete) TEMPERATURE RANGE PACKAGE 0°C to 85°C 0°C to 85°C Molded DIP (P18) SOIC (S18) © Micro Linear 1997 is a registered trademark of Micro Linear Corporation Products described in this document may be covered by one or more of the following patents, U.S.: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502; 5,508,570; 5,510,727; 5,523,940; 5,546,017; 5,559,470; 5,565,761; 5,592,128; 5,594,376; Japan: 2598946; 2619299. Other patents are pending. Micro Linear reserves the right to make changes to any product herein to improve reliability, function or design. Micro Linear does not assume any liability arising out of the application or use of any product described herein, neither does it convey any license under its patent right nor the rights of others. The circuits contained in this data sheet are offered as possible applications only. Micro Linear makes no warranties or representations as to whether the illustrated circuits infringe any intellectual property rights of others, and will accept no responsibility or liability for use of any application herein. The customer is urged to consult with appropriate legal counsel before deciding on a particular application. 2092 Concourse Drive San Jose, CA 95131 Tel: 408/433-5200 Fax: 408/432-0295 DS4833-01 13