MP4031GS-Z

MP4031 TRIAC and Analog Dimmable, Primary-Side–Controlled Offline LED Controller with Active PFC The Future of Analog IC Technology DESCRIPTION FEATURES The MP4031 is a TRIAC and analog dimmable, primary-side–controlled, offline LED lighting controller with active PFC. It can output an accurate LED current for an isolated lighting application with a single-stage converter. The proprietary real-current–control method can accurately control the LED current using primaryside information. It can significantly simplify LED lighting system design by eliminating secondaryside feedback components and the optocoupler. • The MP4031 implements power-factor correction and works in boundary-conduction mode to reduce MOSFET switching losses. The MP4031 has an integrated charging circuit at the supply pin for fast start-up without a perceptible delay. The proprietary dimming control expands the TRIAC-based dimming range. The special current sense implement analog dimming. structure can The MP4031 has multiple protections that greatly enhance system reliability and safety, including over-voltage protection, overload protection, supply-pin under-voltage lockout, and overtemperature protection. • • • • • • • • • • • Primary-Side-Control without Secondary-Side Feedback Internal Charging Circuit at the Supply Pin for Fast Start-Up Accurate Line Regulation High Power Factor Operates in Boundary Conduction Mode Flicker-Free, Phase-Controlled TRIAC Dimming with Expanded Dimming Range. Analog-Dimming Compatible Cycle-by-Cycle Current Limit Over-Voltage Protection Over-Load Protection Over-Temperature Protection Available in an 8-Pin SOIC Package APPLICATIONS • Solid-State Lighting, including: o Industrial and Commercial Lighting o Residential Lighting All MPS parts are lead-free and adhere to the RoHS directive. For MPS green status, please visit MPS website under Products, Quality Assurance page. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. All fault protections feature auto-restart. The MP4031 is available in an 8-pin SOIC package. MP4031 Rev.1.03 9/5/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 1 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC TYPICAL APPLICATION Analog Dimming Application N:1 EMI Filter MP 4031 1 MULT COMP ZCD GND VCC D CS /DIM S VA_DIM Analog with Triac Dimming Application MP4031 Rev.1.03 9/5/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 2 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC ORDERING INFORMATION Part Number* Package SOIC8 MP4031GS Top Marking MP4031 * For Tape & Reel, add suffix –Z (e.g. MP4031GS–Z); PACKAGE REFERENCE TOP VIEW MULT 1 8 COMP ZCD 2 7 GND VCC 3 6 D 4 5 S CS/DIM SOIC8 (4) ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Input Voltage VCC ....................... -0.3V to +30V Low-Side MOSFET Drain Voltage -0.7V to +30V ZCD Pin Voltage ............................... -8V to +7V Other Analog Inputs and Outputs ..... -0.3V to 7V ZCD Pin Current ......................... -5mA to +5mA Continuous Power Dissipation (TA = +25°C) (2) SOIC8........................................................1.3W Junction Temperature .............................. 150°C Lead Temperature ................................... 260°C Storage Temperature ............... -65°C to +150°C SOIC8 ................................... 96 ...... 45 ... °C/W Recommended Operating Conditions (3) θJA θJC Notes: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ(MAX), the junction-toambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD(MAX)=(TJ(MAX)TA)/ θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 3) The device is not guaranteed to function outside of its operation conditions. 4) Measured on JESD51-7 4-layer board. Supply Voltage VCC ........................ 11V to 27V Operating Junction Temp (TJ). . -40°C to +125°C MP4031 Rev.1.03 9/5/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 3 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC ELECTRICAL CHARACTERISTICS TA = +25°C, unless otherwise noted. Parameter Supply Voltage Symbol Operating Range VCC VCC Upper Level: Internal Charging Circuit Stops and IC Turns On VCCH VCC Lower Level: Internal Charging Circuit Trigger VCCL VCC Re-charge/IC Turn-Off Level in Fault Condition Supply Current VCC Charging Current from D Quiescent Current Quiescent Current at Fault Operating Current Condition Min After turn on 10 Typ Max Units 27 V 9.5 10 10.5 V Vcc falling, No fault 8.55 9 9.45 V VCCEN Vcc falling, Fault occurs 6.45 7 7.55 V ID charge VD=16V, VCC=5V 12.5 15 17.5 mA Iq No switching, VCC=15V 800 1000 µA Iq_fault 220 300 µA Icc Fault condition, IC latch, VCC=15V fs =70kHz, VCC=15V 1 2 mA VMULT VCOMP from 1.9V to 4.9V 3 V 180 Multiplier Linear Operation Range (5) Gain K 0 VCOMP=2V, VMULT=0.5V 0.84 1.06 1.26 1/V VCOMP=2V, VMULT=1.5V 0.9 1.08 1.23 1/V VCOMP=2V, VMULT=3V 0.93 1.1 1.25 1/V TRIAC Dimming Off Detection Threshold TRIAC Dimming On Detection Threshold VMUL_off 0.13 0.15 0.17 V VMUL_on 0.32 0.35 0.38 V TRIAC Dimming Off Line-Cycle Blanking Ratio Doff_LEB 0.414 V 25% Error Amplifier Reference Voltage VREF Transconductance GEA 0.386 Guaranteed by design 0.4 250 µA/V COMP Lower Clamp Voltage VCOMPL Max. Source Current ICOMP+ 57 µA Max. Sink Current without Dimmer Sink Current at TRIAC Dimming Off ICOMP- -300 µA Over-Load Detect Threshold MP4031 Rev.1.03 9/5/2014 1.85 1.9 1.95 V Isink_dim 60 70 80 µA VCOMP_OLP 4.85 5 5.15 V www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 4 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC ELECTRICAL CHARACTERISTICS (continued) TA = +25°C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units Current Sense Comparator Leading-Edge Blanking Time τLEB 360 450 540 ns Current Sense Upper Clamp Voltage VS clamp H 2.2 2.3 2.4 V Current Sense Lower Clamp Voltage VS clamp L 0.12 0.15 0.18 V 0.32 0.35 0.37 V 520 550 580 mV 1.8 2.5 3.1 µs 5.2 5.5 5.8 V 1.5 2 2.5 µs 4.2 5.6 7 µs 90 115 140 µs Zero-Current Detector Zero-Current–Detect Threshold VZCD Zero-Current–Detect Hysteresis VZCD Zero-Current–Detect LEB VZCD LEB Over-Voltage Threshold VZCD OVP OVP Detect LEB τOVP LEB Minimum Off Time τoff T Falling Edge Hy Starts at Gate Turn Off Starts at Gate Turn Off min Starter Start-Timer Period τstart Internal Main MOSFET VGS=0 Breakdown Voltage BVDSS Drain-Source On-Resistor RDS(on)_main ID=100mA main 30 200 V 250 300 mΩ Notes: 5) The multiplier output is given by: Vs=K•VMULT• (VCOMP-1.5) MP4031 Rev.1.03 9/5/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 5 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC PIN FUNCTIONS Pin # Name 1 MULT 2 ZCD 3 VCC 4 CS/DIM 5 S Internal Low-Side Main MOSFET Source. Connect a resistor from this pin to GND to sense the internal MOSFET current. 6 D Internal Low-Side Main MOSFET Drain. This pin internally connects to VCC via a diode and a JFET to form an internal charging circuit for VCC. Connect to the source of the high-side MOSFET. 7 GND 8 COMP MP4031 Rev.1.03 9/5/2014 Pin Function Internal Multiplier Input. Connect to the tap of resistor divider from the rectified voltage of the AC line. The half-wave sinusoid signal to this pin provides a reference signal for the internal current control loop. The MULT pin also detects the TRIAC dimming phase. Zero-Current Detection. A negative going edge triggers the internal MOSFET’s turn-on signal. Connect to the tap of a resistor divider from the auxiliary winding to GND. ZCD can also detect over-voltage and over-current conditions. Over-voltage occurs if VZCD exceeds the over-voltage-protection (OVP) threshold after a 2µs blanking time when the internal MOSFET turns off. Supply Voltage. Supplies power for both the control signal and the internal MOSFET’s gate driver. Connect to an external bulk capacitor—typically 22µF with a 100pF ceramic capacitor to reduce noise. Current Sense and Analog dimming. An internal comparator compares the Current Sense voltage to the internal sinusoidal current reference to determine when the MOSFET turns off. If the voltage exceeds the current-limit threshold of 2.3V after the leading edge blanking time and during the turn-on interval, the gate signal turns off. In Triac dimming, this pin is connected directly to S Pin for current sense, and in Analog dimming, the Analog dimming signal is added through this pin as the typical application shows. Ground. Current return of the control signal and the gate drive signal. Loop Compensation. Connects to a compensation network to stabilize the LED driver and accurately control the LED driver current. The COMP pin can also monitor for overload conditions: if the COMP voltage rises above 5V, the overload protection triggers. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 6 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC TYPICAL PERFORMANCE CHARACTERISTICS VIN =120VAC, 7 LEDs in series, IO=350mA, VO=22V, Lm=1.6mH, NP:NS:NAUX =82:16:19, TRIAC dimmable. IIN 100mA/div. ILED 200mV/div. VS 1V/div. VCC 10V/div. VZCD 2V/div. VCOMP 1V/div. VD 10V/div. VD 10V/div. ILED 200mA/div. ILED 200mA/div. VCOMP 1V/div. ILED 100mA/div. VCC 10V/div. VCC 10V/div. VMULT 1V/div. VCOMP 1V/div. IIN 200mA/div. VCOMP 1V/div. VD 10V/div. VD 10V/div. VCOMP 1V/div. ILED 50mA/div. VMULT 1V/div. VCOMP 1V/div. ILED 5mA/div. VMULT 1V/div. IIN 200mA/div. IIN 200mA/div. MP4031 Rev.1.03 9/5/2014 VIN 100V/div. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 7 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC TYPICAL PERFORMANCE CHARACTERISTICS VIN =120VAC, 7 LEDs in series, IO=350mA, VO=22V, Lm=1.6mH, NP:NS:NAUX =82:16:19, TRIAC dimmable. Conducted EMI Triac Dimming Curve 400 350 300 250 200 150 100 50 0 0.0 20.0 40.0 60.0 80.0 100.0 Performance Data Vin (VAC) 108V 120V 132V Pin (W) 9.58W 9.54W 9.47W PF 0.993 0.99 0.982 THD 7.00% 9.50% 11.60% Io (A) 0.36A 0.364A 0.364A Vo (V) 21.62V 21.65V 21.64V Efficiency 81.20% 82.60% 83.10% MP4031 Rev.1.03 9/5/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 8 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC TYPICAL PERFORMANCE CHARACTERISTICS VIN =120VAC, 7 LEDs in series, IO=350mA, VO=22V, Lm=1.6mH, NP:NS:NAUX =82:16:19, Analog dimmable. ILED 200mV/div. VS 1V/div. VCC 10V/div. VZCD 2V/div. VCOMP 1V/div. VD 10V/div. VD 10V/div. ILED 200mA/div. ILED 200mA/div. VCC 10V/div. VCC 10V/div. VCOMP 1V/div. VCOMP 1V/div. VD 10V/div. VD 10V/div. VD 10V/div. VD 10V/div. VZCD 2V/div. VCOMP 1V/div. VZCD 2V/div. VCOMP 1V/div. VCS 500mV/div. VCS 500mV/div. MP4031 Rev.1.03 9/5/2014 IIN 100mA/div. VIN 100V/div. VD 10V/div. VZCD 2V/div. VCS 1V/div. VCOMP 1V/div. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 9 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC TYPICAL PERFORMANCE CHARACTERISTICS VIN =120VAC, 7 LEDs in series, IO=350mA, VO=22V, Lm=1.6mH, NP:NS:NAUX =82:16:19, Analog dimmable. 400 350 300 250 200 150 100 50 0 0 1 MP4031 Rev.1.03 9/5/2014 2 3 4 5 6 7 8 9 10 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 10 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC FUNCTIONAL BLOCK DIAGRAM N:1 TRIAC Dimmer EMI Filter MULT D TRIAC Phase Detector PWM / PFC Gate Driver Control Multiplier Current control S COMP Real Current Calculation Gate control Latch off and counting UVLO / EN VCC Power Supply Protection OVP OTP Current Sense CS/DIM Current LImit GND Zero Current Detection ZCD Zero current detection Figure 1: Functional Block Diagram MP4031 Rev.1.03 9/5/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 11 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC OPERATION The MP4031 is a TRIAC and analog dimmable, primary-side–controlled, offline LED controller designed for high-performance LED lighting. The MP4031 can accurately control the LED current using the real-current–control method based on primary-side information. It can also achieve a high power factor to eliminate noise pollution on the AC line. The integrated VCC charging circuit can achieve fast start-up without any perceptible delay. The MP4031 is suitable for TRIAC-based dimming with an extended dimming range. And the special current sense structure can implement analog dimming. Boundary-Conduction Mode During the external MOSFET ON time (τON), the rectified input voltage applied across the primaryside inductor (Lm) increases the primary current increases linearly from zero to the peak value (Ipk). When the external MOSFET turns off, the energy stored in the inductor forces the secondary-side diode to turn on, and the inductor current decreases linearly from the peak value to zero. When the current decreases to zero, the parasitic resonance caused by the inductor and the combined parasitic capacitances decreases the MOSFET drain-source voltage that is also reflected on the auxiliary winding (see Figure 2). The zero-current detector generates the external MOSFET turn-on signal when the ZCD voltage falls below 0.35V after a blanking time and ensures the MOSFET turns on at a relatively low voltage (see Figure 3). VDS VBUS +NV OUT turn-on VBUS I pri Ipk Inductor current t on I sec /N t off VZCD 0 Figure 2: Boundary-Conduction Mode Auxiliary Winding + Vcc RZCD1 ZCD 0.35V RZCD2 CZCD Figure 3: Zero-Current Detector As a result, there are virtually no primary-switch turn-on losses and no secondary-diode reverserecovery losses. This ensures high efficiency and low EMI noise. Real-Current Control The proprietary real-current–control method allows the MP4031 to control the secondary-side LED current based on primary-side information. The output LED mean current can be calculated approximately as: Io ≈ MP4031 Rev.1.03 9/5/2014 N ⋅ VFB 2 ⋅ Rs www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 12 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC Where: • N is the turn ratio of the primary side to the secondary side, • VFB is the feedback reference voltage (typically 0.4), and • Rs is the sense resistor between the MOSFET source and GND. again. This cycle repeats until the auxiliary winding voltage is high enough to power VCC. If any fault occurs during this time, the switching and the internal charging circuit will stop and latch, and VCC drops. When VCC decreases to 7V, the internal charging circuit re-charges for auto-restart. Vcc Auxiliary Winding Takes Charge And Regulates the VCC Power-Factor Correction The MULT pin connects to the tap of a resistor divider from the rectified instantaneous line voltage. The multiplier output also has a sinusoidal shape. This signal provides the reference for the current comparator against the primary-side–inductor current, which shapes the primary-peak current into a sinusoid with the same phase as the input line voltage. This achieves a high power factor. Fault happens 10V 9V 7V Internal Charging Circuit Gate Multiplier output Switching Pulses Inductor current Figure 5: VCC Timing Sequence Auto Start Figure 4: Power-Factor Correction The multiplier’s maximum output voltage to the current comparator is clamped to 2.3V to limit the cycle-by-cycle current. The multiplier’s minimum output voltage is clamped to 0.1 to ensure a turnon signal during the TRIAC dimming OFF interval, which pulls down the rectifier input voltage and accurately detects the dimming phase. VCC Timing Sequence Initially, VCC charges through the internal charging circuit from the AC line. When VCC reaches 10V, the internal charging circuit stops charging, the control logic initializes and the internal main MOSFET begins to switch. Then the auxiliary winding takes over the power supply. However, the initial auxiliary-winding positive voltage may not be large enough to charge VCC, causing VCC to drop. Instead, if the VCC voltage drops below the 9V threshold, the internal charging circuit triggers and charges VCC to 10V MP4031 Rev.1.03 9/5/2014 The MP4031 includes an auto starter that starts timing when the MOSFET turns off. If ZCD fails to send a turn-on signal after 122µs, the starter will automatically sends a turn-on signal to avoid unnecessary IC shutdowns if ZCD fails. Minimum OFF Time The MP4031 operates with a variable switching frequency; the frequency changes with the instantaneous input-line voltage. To limit the maximum frequency and get good EMI performance, the MP4031 employs an internal minimum OFF-time limiter of 5µs, as shown in Figure 6. ZCD GATE 5.6us Figure 6: Minimum OFF time www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 13 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC Auxiliary Winding Leading-Edge Blanking In order to avoid premature switching-pulse termination due to the parasitic capacitances discharging when the MOSFET turns on, an internal leading-edge blanking (LEB) unit between the S pin and the current-comparator input blocks the path from the S pin to the current comparator input during the blanking time. Figure 7 shows the leading-edge blanking. + Vcc RZCD1 ZCD OVP signal Latch 5.5V VS RZCD2 CZCD 2 uS Blanking TLEB = 450nS Figure 8: OVP Sampling Circuit To avoid switch-on spikes mis-triggering OVP, OVP sampling has a τOVPS blanking period of around 2µs, as shown in Figure 9. t VZCD Sampling Here Figure 7: Leading-Edge Blanking Output Over-Voltage Protection (OVP) Output over-voltage protection (OVP) prevents component damage from over-voltage conditions. The auxiliary winding voltage’s positive plateau is proportional to the output voltage, and the OVP monitors this auxiliary winding voltage instead of directly monitoring the output voltage as shown in Figure 8. Once the ZCD pin voltage exceeds 5.5V, the OVP signal triggers and latches, the gate driver turns off, and the IC functions in quiescent mode. When the VCC voltage drops below the UVLO threshold, the IC shuts down and the system restarts. The output OVP set point can be calculated as: Vout _ ovp ⋅ Naux R ZCD2 ⋅ = 5.5 Nsec R ZCD1 + R ZCD2 Where: Vout-ovp is the output OVP threshold, Naux is the number of auxiliary winding turns, and Nsec is the number of secondary winding turns MP4031 Rev.1.03 9/5/2014 0V T OVPS Figure 9: ZCD Voltage and OVP Sampling Overload Protection (OLP) In the event of an output overload, the COMP voltage rises. When the voltage reaches 5V, the IC will shut down and restart until VCC drops below UVLO. Thermal Shutdown To prevent internal temperatures from exceeding 150°C and causing lethal thermal damage, the MP4031 shuts down the switching cycle and latched until VCC dropping below UVLO and restarts again. TRIAC-Based Dimming Control The MP4031 can be used in TRIAC-based dimming application with the CS pin connected directly to the S pin. The TRIAC dimmer usually consists of a bi-directional SCR with an adjustable turn-on phase. Figure 10 shows the leading-edge TRIAC dimmer waveforms. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 14 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC If the turn-on cycle decreases to less than 75% of the line cycle, the internal reference voltage decreases as the dimming turn-on phase decreasing, and the output current decreases accordingly to implement dimming. As the dimming turn-on cycle decreases, the COMP voltage also decreases. Once the COMP voltage reaches to 1.9V, it is clamped so that the output current decreases slowly to maintain the TRIAC holding current and avoid random flicker. Figure 12 shows the relationship between the dimming turn-on phase and output current. Input line voltage before TRIAC dim m er Line voltage after TRIAC dimmer Rectified line voltage Dimmer t urn on phase Line cycle Io Figure 10: TRIAC Dimmer Waveforms The MP4031 detects the dimming turn-on cycle through the MULT pin, which is fed into the control loop to adjust the internal reference voltage. When the MULT voltage exceeds 0.35V, the device treats this signal as a dimmer turn-on signal. When the MULT voltage falls below 0.15V, the system treats this as a dimmer turn-off signal. The MP4031 has a 25% line-cycle–detection blanking time with each line cycle, The real phase detector output adds this time, as shown in Figure 11. That means if the turn-on cycle exceeds 75% of the line cycle, the output remains at the same maximum current. It improves the line regulation during the maximum TRIAC turn-on cycle or without a dimmer. Figure 11: Dimming Turn-On Cycle Detector MP4031 Rev.1.03 9/5/2014 VCOMP 30% 75% 100% TRIAC dimming turn on cycle Figure 12: Dimming Curve Analog Dimming The MP4031 is also available for analog dimming. With injecting an analog signal to the CS/DIM pin. Figure 13 shows a typical application circuit for analog dimming. The analog dimming signal is usually on the second side, so there will be isolation circuit (opto-coupler is used) to transfer the dimming signal from second side to the primary side. Opto-coupler can only transfer PWM signal for high accuracy, so there will be interface circuit to change the analog dimming signal into PWM signal as Figure 13 shows. The interface circuit is also used to change the logic of the second analog dimming signal, so that the output current will be direct proportion to the second analog dimming signal. Then a 0V to 10V analog signal VA_DIM is got on the primary side after these two steps. So the voltage at CS/DIM pin ( VCS/DIM ) is determined by the voltage at S pin ( Ip*Rs ) and VA_DIM. The output LED mean current ( Io ) can be calculated www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 15 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC decreases from max value to min, when VA_DIM increasing from 0V to 10V. approximately as: Io = N ⋅ VFB ⋅ 2 Ip R1 R2 ⋅ VA _ DIM + ⋅R ⋅I R1 + R2 R1 + R2 s p As the equation shows, the output current Io N:1 EMI Filter MP4031 1 Power supply MULT COMP ZCD GND VCC D CS /DIM S Ip VCS/DIM 0-10V Dimmer Interface circuit Rs Isolation circuit VA_DIM R2 R1 Figure 13: Typical Application Circuit for Analog Dimming MP4031 Rev.1.03 9/5/2014 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 16 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC RIPPLE SUPPRESSOR (Innovative Proprietary) For dimming LED lighting application, a single stage PFC converter needs large output capacitor to reduce the ripple whose frequency is double of the Grid. And in deep dimming situation, the LED would shimmer caused by the dimming on duty which is not all the same in every line cycle. What’s more, the Grid has noise or inrush which would bring out shimmer even flicker. Figure 14 shows a ripple suppressor, which can shrink the LED current ripple obviously. About the RC filter, it can be selected by τRC ≥ 50 / fLineCycle . Diode D can select 1N4148, and the Zener voltage of DZ is as small as possible when guarantee VD + VDZ > 0.5 ⋅ VCO _PP . Optional Protection Circuit In large output voltage or large LEDs current application, MOSFET M may be destroyed by over-voltage or over-current when LED+ shorted to LED- at working. Gate-Source(GS) Over-voltage Protection: DO DO NS DM R RO + CO C DZ + NS RO D + R CO C M DG DZ RG + Figure 15: Gate-Source OVP Circuit Figure14: Ripple Suppressor Principle: Shown in Figure 14, Resister R, capacitor C, and MOSFET M compose the ripple suppressor. Through the RC filter, C gets the mean value of the output voltage VCo to drive the MOSFET M. M works in variable resistance area. C’s voltage VC is steady makes the LEDs voltage is steady, so the LEDs current will be smooth. MOSFET M holds the ripple voltage vCo of the output. Diode D and Zener diode DZ are used to restrain the overshoot at start-up. In the start-up process, through D and DZ, C is charged up quickly to turn on M, so the LED current can be built quickly. When VC rising up to about the steady value, D and DZ turn off, and C combines R as the filter to get the mean voltage drop of VCo. The most important parameter of MOSFET M is the threshold voltage Vth which decides the power loss of the ripple suppressor. Lower Vth is better if the MOSFET can work in variable resistance area. The BV of the MOSFET can be selected as double as VCo and the Continues Drain current level can be selected as decuple as the LEDs’ current at least. MP4031 Rev.1.03 9/5/2014 Figure 15 shows GS over-voltage protection circuit. Zener diode DG and resistor RG are used to protect MOSFET M from GS over-voltage damaged. When LED+ shorted to LED- at normal operation, the voltage drop on capacitor C is high, and the voltage drop on Gate-Source is the same as capacitor C. The Zener diode DG limits the voltage VGS and RG limits the charging current to protect DG. RG also can limit the current of DZ at the moment when LED+ shorted to LED-. VDG should bigger than Vth. Drain-Source Over-voltage and Over-current Protection As Figure 16 shows, NPN transistor T, resistor RC and RE are set up to protect MOSFET M from over-current damaged when output short occurs at normal operation. When LED+ shorted to LED-, the voltage vDS of MOSFET is equal to the vCo which has a high surge caused by the parasitic parameter. Zener Dioder DDS protects MOSFET from over-voltage damaged. Transistor T is used to pull down the VGS of M. When M turns off, the load is opened, MP4030 detects there is an OVP happened, so the IC functions in quiescent. The www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. 17 MP4031—PRIMARY-SIDE–CONTROLLED, OFFLINE LED CONTROLLER WITH PFC pull down point is set by RC and RE: RC /RE ⋅ MOSFET LIST In the Table 1, there are some recommended MOSFET for ripple suppressor. VCO = 0.7V . 2 Figure 16: Drain-Source OVP and OCP Circuit Table 1: MOSFET LIST Manufacture P/N Si4446DY FTD100N10A P6015CDG MP4031 Rev.1.03 9/5/2014 Manufacture Vishay IPS NIKO-SEM VDS/ID 40V/3A 100V/17A 150V/20A Vth(VDS=VGS@TJ=25°C) 0.6-1.6V@ Id=250μA 1.0-2.0V@ Id=250μA 0.45-1.20V@ Id=250μA www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2014 MPS. All Rights Reserved. Power Stage