HVLED805 Off-line LED driver with primary-sensing Features ■ 800 V, avalanche rugged internal power MOSFET ■ 5% accuracy on constant LED output current with primary control ■ Optocoupler not needed ■ Quasi-resonant (QR) zero voltage switching (ZVS) operation ■ Internal HV start-up circuit ■ Open or short LED string management ■ Automatic self supply ■ Input voltage feed-forward for mains independent cc regulation SO16N Table 1.
Contents HVLED805 Contents 1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 Application information . . . . .
HVLED805 1 Description Description The HVLED805 is a high-voltage primary switcher intended for operating directly from the rectified mains with minimum external parts to provide an efficient, compact and cost effective solution for LED driving. It combines a high-performance low-voltage PWM controller chip and an 800V, avalanche-rugged power MOSFET, in the same package.
Maximum ratings 2 HVLED805 Maximum ratings Table 2. Symbol VDS ID Eav Absolute maximum ratings Pin Parameter 1,2, 13-16 Drain-to-source (ground) voltage 1,2, 13-16 Drain current (1) 1,2, 13-16 Single pulse avalanche energy (Tj = 25°C, ID = 0.7A) Value Unit -1 to 800 V 1 A 50 mJ Vcc 3 Supply voltage (Icc < 25mA) Self limiting V IDMG 6 Zero current detector current ±2 mA Vcomp 7 Analog input -0.3 to 3.6 V 0.
HVLED805 3 Electrical characteristics Electrical characteristics TJ = -25 to 125 °C, Vcc=14 V; unless otherwise specified. Table 4. Electrical characteristics Symbol Parameter Test condition Min. Typ. Max.
Electrical characteristics Table 4. HVLED805 Electrical characteristics (continued) Symbol Parameter Test condition Min. Typ. Max. Unit VDMGH Upper clamp voltage IDMG = 1 mA 3.0 3.3 3.6 V VDMGL Lower clamp voltage IDMG = - 1 mA -90 -60 -30 mV VDMGA Arming voltage positive-going edge 100 110 120 mV VDMGT Triggering voltage negative-going edge 50 60 70 mV IDMGON Min.
HVLED805 4 Pin connection Pin connection Figure 2. Pin connection (top view) SOURCE 1 16 DRAIN SOURCE 2 15 DRAIN VCC 3 14 DRAIN GND 4 13 DRAIN ILED 5 12 N.C. DMG 6 11 N.A. 7 10 8 9 COMP N.A. Note: N.A. N.A.
Pin connection Table 5. N. 1, 2 HVLED805 Pin functions Name Function Power section source and input to the PWM comparator. The current flowing in the MOSFET is sensed through a resistor connected between the pin and GND. The resulting voltage is compared with an internal reference (0.75V typ.) to determine MOSFET’s turn-off. The pin is SOURCE equipped with 250 ns blanking time after the gate-drive output goes high for improved noise immunity.
HVLED805 Pin connection Figure 3. COSS output capacitance variation 500 C OSS (pF) 400 300 200 100 0 0 25 50 75 100 125 150 V DS (V) Figure 4. Off state drain and source current test circuit + - 1 4V V CC 2.5V A D RA IN + CUR RE NT CON TR OL - D MG COM P Note: Idss IL ED G ND V in 75 0V S OUR CE The measured IDSS is the sum between the current across the 12 MΩ start-up resistor (62.5 µA typ.
Pin connection HVLED805 Figure 5. Start-up current test circuit + Icc sta rt-u p A - 1 1.8 V V CC 2.5V D RA IN CUR RE NT CON TR OL D MG COM P Figure 6. IL ED G ND S OUR CE Quiescent current test circuit + Iq _m ea s A - VC C 2 .5V 14 V DR AIN C UR REN T C ONT RO L DM G 33 k - 3V C OMP ILE D GN D SO URC E + + 1 0k + - Iq = Iq_meas - 10/29 - 0.8 V 0.11⋅ 3V -100μ A 3.3kΩ Doc ID 18077 Rev 1 0 .
HVLED805 Pin connection Figure 7. Operating supply current test circuit + Icc A - 1 .5k 2W 15 V 27 k V CC DRA IN 2 20 k 2.5 V + CU RRE NT CO NTR OL - D MG 10 k 15 0V 10 k CO MP IL ED GND S OU RCE 10 5 .6 + 2 .8V + 5 0kHz - Note: - -5 V The circuit across the DMG pin is used for switch-on synchronization Figure 8. Quiescent current during fault test circuit + Iq (fa ult) A - V CC 2.
Application information 5 HVLED805 Application information The HVLED805 is an off-line all-primary sensing switching regulator, specific for offline LED drivers based on quasi-resonant ZVS (zero voltage switching at switch turn-on) flyback topology. Depending on converter’s load condition, the device is able to work in different modes (Figure 9 for constant voltage operation): 1. QR mode at heavy load.
HVLED805 5.1 Application information Power section and gate driver The power section guarantees safe avalanche operation within the specified energy rating as well as high dv/dt capability. The Power MOSFET has a V(BR)DSS of 800V min. and a typical RDSon of 11 Ω. The gate driver of the power MOSFET is designed to supply a controlled gate current during both turn-on and turn-off in order to minimize common mode EMI.
Application information HVLED805 Most of this current will charge the bypass capacitor connected between the Vcc pin and ground and make its voltage rise linearly. As the Vcc voltage reaches the start-up threshold (13 V typ.) the chip starts operating, the internal power MOSFET is enabled to switch and the HV generator is cut off by the Vcc_OK signal asserted high. The IC is powered by the energy stored in the Vcc capacitor.
HVLED805 Secondary side demagnetization detection and triggering block The demagnetization detection (DMG) and Triggering blocks switch on the power MOSFET if a negative-going edge falling below 50 mV is applied to the DMG pin. To do so, the triggering block must be previously armed by a positive-going edge exceeding 100 mV.
Application information HVLED805 After the first few cycles initiated by the starter, as the voltage developed across the auxiliary winding becomes large enough to arm the DMG circuit, MOSFET’s turn-on will start to be locked to transformer demagnetization, hence setting up QR operation. The starter is activated also when the IC is in CC regulation and the output voltage is not high enough to allow the DMG triggering.
HVLED805 Application information Figure 14. Voltage control principle: internal schematic DMG S/H - Rdmg EA + Rfb + Aux To PWM Logic CV 2.5V DEMAG LOGIC F rom Rsense COMP R C Due to the parasitic wires resistance, the auxiliary voltage is representative of the output just when the secondary current becomes zero.
Application information 5.5 HVLED805 Constant current operation Figure 15 presents the principle used for controlling the average output current of the flyback converter. The output voltage of the auxiliary winding is used by the demagnetization block to generate the control signal for the mosfet switch Q1. A resistor R in series with it absorbs a current VC/R, where VC is the voltage developed across the capacitor C.
HVLED805 Application information Equation 6 IP = VC R SENSE Combining (2), (3) (5) and (6): Equation 7 IOUT = n VCLED ⋅ 2 R SENSE This formula shows that the average output current does not depend anymore on the input or the output voltage, neither on transformer inductance values. The external parameters defining the output current are the transformer ratio n and the sense resistor RSENSE. Figure 15. Current control principle .
Application information HVLED805 Figure 16. Constant current operation: Switching cycle waveforms T IP t Is t Q t IC ICLED V ICLED =− C R 5.6 t Voltage feedforward block The current control structure uses the voltage VC to define the output current, according to (7). Actually, the CC comparator will be affected by an internal propagation delay Td, which will switch off the MOSFET with a peak current than higher the foreseen value.
HVLED805 Application information Figure 17. Feedforward compensation: internal schematic DRAIN DMG F eedforward Logic . Rfb Aux CC Block IF F - Rdmg CC PWM LOGIC + RFF SO URCE Rsense During MOSFET’s ON-time the current sourced from DMG pin is mirrored inside the “Feedforward Logic” block in order to provide a feedforward current, IFF.
Application information HVLED805 This offset is proportional to VIN and is used to compensate the current overshoot, according to the formula: Equation 13 VIN ⋅ Td V ⋅R ⋅ RSENSE = IN FF Lp m ⋅ R dmg Finally, the Rdmg resistor can be calculated as follows: Equation 14 R dmg = L p ⋅ RFF NAUX ⋅ NPRI Td ⋅ R SENSE In this case the peak drain current does not depend on input voltage anymore.
HVLED805 Application information Figure 18. Load-dependent operating modes: timing diagrams COMP 65 mV hyster. VCOMPL IDS Normal-mode 5.8 TSTART TSTART TSTART Burst-mode TSTART Normal-mode Soft-start and starter block The soft start feature is automatically implemented by the constant current block, as the primary peak current will be limited from the voltage on the CLED capacitor.
Application information HVLED805 before the VCC capacitor is charged again and the device restarted. Ultimately, this will result in a low-frequency intermittent operation (Hiccup-mode operation), with very low stress on the power circuit. This special condition is illustrated in the timing diagram of Figure 18. Figure 19. Hiccup-mode OCP: timing diagram Secondary diode is shorted here VCC VccON VccOFF Vccrest VSOURCE Vcsdis t 1V Two switching cycles VDS t t 5.
HVLED805 Application information Figure 20. Suggested routing for converter ACIN ACIN DRAIN VDD DMG COMP ...
Package mechanical data 6 HVLED805 Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark. Table 6. SO16N mechanical data mm inch Dim. Min Typ A a1 Min Typ 1.75 0.1 Max 0.069 0.25 a2 0.004 0.009 1.6 0.063 b 0.35 0.46 0.014 0.
HVLED805 Package mechanical data Figure 21.
Revision history 7 HVLED805 Revision history Table 7.
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