Introduction The STEVAL-LLL008V1 reference design is a dual-stage LED driver with high power factor designed for 100 W LED lighting applications using 6LoWPAN mesh networking. It consists of two main sections, the power main board and the connectivity daughter board. The power board in the STEVAL-LLL008V1 evaluation kit, with dual-stage power conversion and high power factor, is highly suitable for satisfying LED power supply specifications in street lighting applications. On the primary side, the HVLED001B controller manages the AC/DC HPF Flyback converter. The control loop is managed through primary side regulation (PSR), in which the primary auxiliary transformer provides a signal proportional to the output voltage on the controller pin ZCD. The main advantage of primary side management of the voltage loop is that no isolated optocoupler is needed. The converter output (J2 connector) can deliver 105 W with an average output voltage of 79 V (~1.8 V maximum ripple) to the buck stage, which can generate 1.4 A regulated current to the LED driver loads. The auxiliary choke of a few milliamps available on the secondary transformer stage is able to supply the voltage needed to power the HVLED002 controller, which manages the inverse buck circuit. The connectivity daughter board integrates an STM32L071KZ microcontroller, which is able to receive remote on, off and dimming commands via an embedded SPSGRFC sub-1 GHz transceiver module. The connectivity functionality can be extended to multiple lighting nodes in a 6LowPAN mesh network. The daughter board can be connected through the J12 4-pin connector on the power board. Pin 1 powers the control board with 3.3 V; Pin 4 provides a common GND; Pin 3 is for Enable/ Disable signals from the control board; Pin 2 is for PWM dimming signals from the control board. The overall design offers high efficiency, a PSR control loop without optocoupler, and the option to connect a control board with programmable STM32 microcontroller for dimming and Enable/Disable functionality. Figure 1. STEVAL-LLL008V1 evaluation kit power board and control board 100 W high efficiency and low THD dimmable LED driver reference design based on HVLED001B, HVLED002 and SPSGRFC AN5467 Application note AN5467 - Rev 1 - May 2020 For further information contact your local STMicroelectronics sales office. www.st.com
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IntroductionThe STEVAL-LLL008V1 reference design is a dual-stage LED driver with high power factor designed for 100 W LED lightingapplications using 6LoWPAN mesh networking. It consists of two main sections, the power main board and the connectivitydaughter board.
The power board in the STEVAL-LLL008V1 evaluation kit, with dual-stage power conversion and high power factor, is highlysuitable for satisfying LED power supply specifications in street lighting applications.
On the primary side, the HVLED001B controller manages the AC/DC HPF Flyback converter. The control loop is managedthrough primary side regulation (PSR), in which the primary auxiliary transformer provides a signal proportional to the outputvoltage on the controller pin ZCD. The main advantage of primary side management of the voltage loop is that no isolatedoptocoupler is needed.
The converter output (J2 connector) can deliver 105 W with an average output voltage of 79 V (~1.8 V maximum ripple) to thebuck stage, which can generate 1.4 A regulated current to the LED driver loads. The auxiliary choke of a few milliamps availableon the secondary transformer stage is able to supply the voltage needed to power the HVLED002 controller, which manages theinverse buck circuit.
The connectivity daughter board integrates an STM32L071KZ microcontroller, which is able to receive remote on, off anddimming commands via an embedded SPSGRFC sub-1 GHz transceiver module. The connectivity functionality can beextended to multiple lighting nodes in a 6LowPAN mesh network. The daughter board can be connected through the J12 4-pinconnector on the power board. Pin 1 powers the control board with 3.3 V; Pin 4 provides a common GND; Pin 3 is for Enable/Disable signals from the control board; Pin 2 is for PWM dimming signals from the control board.
The overall design offers high efficiency, a PSR control loop without optocoupler, and the option to connect a control board withprogrammable STM32 microcontroller for dimming and Enable/Disable functionality.
Figure 1. STEVAL-LLL008V1 evaluation kit power board and control board
100 W high efficiency and low THD dimmable LED driver reference design based on HVLED001B, HVLED002 and SPSGRFC
AN5467
Application note
AN5467 - Rev 1 - May 2020For further information contact your local STMicroelectronics sales office.
High voltage LED street and zone lighting applications typically require robust but highly efficient power suppliesable to generate tightly regulated output currents with high power factor, low THD and minimal voltage ripple.The design achieves very high efficiency through the HVLED001B controller, which drives a STF23N80K5 powerMOSFET on the primary side of an AC/DC HPF flyback converter and regulates the voltage on the same primaryside.The flyback converter output is then regulated by the inverse buck stage, which is driven by the HVLED002controller through the STL4N10F7 power MOSFET. The HVLED002 translates external dimming commands intocurrent limitation on the inverse buck converter to achieve the desired dimming effect.Networking and connectivity solutions are also often implemented for the simultaneous control of several lightingnodes in a certain area. The STEVAL-LLL008V1 power converter is coupled with a SPSGRFC module to providesub-1 GHz connectivity for remote dimming and on/off control. The STSW-LLL008FW firmware for the evaluationkit provides 6LoWPAN functionality to allow wireless mesh network control of multiple nodes, with the addition ofa data concentrator unit able to provision devices on a 6LoWPAN network and interface with an app to deliverSmart City lighting control.
Figure 2. LED street lighting application with high voltage LED controller
90 - 265VAC Mains LDO
Bridgerectifier
STM32L071KZMCU
STM32L0
STSW-LLL008FW firmware
SPSGRFCSPIRIT-1
transceiver unitON / OFF
DIMMING
CURRENTCONTROL
Vout = 75V
3V3
Flyback topology
STF23N80K5
STM32 NUCLEO PLATFORMDATA CONCENTRATOR UNIT
powerboard
HVLED001BHPF flyback
controller
STTH30R03CG1.5KE300A
STPS1H100U
mobileApp
STM32L0
6LoWPAN wirelessmesh network
HVLED002LED
controller
connectivityboard
Pout = 105Wat 1.4A
drivers
utilities
CMSISmiddleware
applications
STTH108A
STL4N10F7
Inverse buck
VIN
Filter
GATEDRIVER
ZCD
PSRCONTROL
LOOP
ON / OFF
DIMMING
LF33AB
AN5467LED street lighting in Smart City applications
No Load Consumption265 VIN_AC stand alone: <300 mW
265 VIN_AC with MCU board: <600 mW
Output Ripple Current max. <100 mA
THD at 100 W for range VIN <15%
PF at 100 W for range VIN >95%
Table 2. STEVAL-LLL008V1 Connectors and Test Points
Reference Type Description
J1 PCB Terminal Power Input
J2 PCB Terminal Output AC-DC converter
J5 PCB Terminal Output A/K LED load
J12 Female Headers Connection with MCU board
TP1 Test Point VCC → HVLED001B
TP2 Test Point FB → HVLED001B
TP3 Test Point CS → HVLED001B
TP4 Test Point TOFF → HVLED001B
TP5 Test Point OPTO → HVLED001B
TP6 Test Point ZCD → HVLED001B
TP7 Test Point Primary VBUS
TP8 Test Point GD → HVLED001B
TP9 Test Point Primary GND
TP10 Test Point Secondary GND
TP11 Test Point Secondary VAUX
TP12 Test Point VOUT AC-DC converter
TP13 Test Point Primary VDrain
TP15 Test Point Secondary VCS
AN5467STEVAL-LLL008V1 power board overview
AN5467 - Rev 1 page 6/35
Reference Type Description
TP16 Test Point Secondary VGate
TP17 Test Point Secondary VDrain
RELATED LINKS refer to the HVLED001B datasheet for detailed electrical characteristics of this device
refer to the HVLED002 datasheet for detailed electrical characteristics of this device
4.1 HPF Flyback stage
The HPF Flyback stage is able to support a wide input voltage range (90-265 V) managed on the primary side bythe HVLED001B (U3) controller, which implements quasi-resonant valley skipping with secondary rectificationdiode.The PSR control loop is regulated through an auxiliary winding partitioned on the ZCD pin. By exploiting thisappropriately calculated partition, it is also possible to set an output overvoltage threshold beyond which thesystem halts primary switching activity, as well as possible brown-in/out thresholds.As soon as the input voltage is supplied to the J1 connector, the HVLED001B device is turned on thanks to thehigh voltage start up (pin 1), which preloads the VCC of the device, and is then self-powered thanks to theswitching activity that provides a voltage from the primary auxiliary.The same auxiliary, thanks to the R5, R6 and R14 partition on the ZCD pin, is able to regulate the converteroutput voltage (PSR). The STF23N80K5 (800 V) Power MOSFET is able to withstand the voltage peaks, whichare clamped by diodes D4 and D5. The secondary diode is the high performance STTH30R03CG diode and theregulated converter output is 79 V with a 1.8 V pk-pk network frequency ripple.
4.2 Inverted Buck stage
The second stage is an inverted buck capable of controlling an average current of 1.4 A (at 100% load), withswitching activity managed by the HVLED002 (U2) controller. It is powered by the secondary auxiliary windingwhich, thanks to diode D1 and the circuit with the linear regulator (with Q5, U5), turns on the HVLED002 controller(U2), which manage the switching of the buck circuitry (Q2, D18, L2).The constant output LED load current is set by the current sense resistors R42 and R52. The FB pin works insideits operating range set by the fixed VREF pull-up voltage (5 V), which provides a current on resistor R38 throughthe PNP MOSFET.In zero load conditions, a Zener diode (D11-82 V) prevents the output voltage from exceeding the maximumratings of embedded devices. This overvoltage can occur during burst mode switching activity at the no loadcondition, as the primary winding is unable to provide an appropriate signal to the ZCD to regulate the outputvoltage..
4.3 External On/Off and dimming control
The STEVAL-LLL008V1 evaluation kit includes an MCU board with STM32 microcontroller that can be connectedto the power board and receive a 3.3 V regulated voltage from the HVLED002 VIN line via the LF33AB regulator.The connected microcontroller can provide a 0 - 3.3 V square wave PWM signal (pin2) to control dimmingfunctionality. When the signal is 0 V, the FB pin remains inside operating range and the HVLED002 controlleroperates normally; when the signal is at 3.3 V, the FB pin is pulled out of range and controller activity issuspended. Dimming is therefore achieved by regulation of the average LED current output, which is directlyproportional to the TON component of the PWM signal sent by the microcontroller.The MCU board can also supply 3.3 V continuous voltage on the EN Control ON-OFF (pin3) that injects a currenton the U5 Voltage Reference to ensure that the output voltage of the linear regulator will stabilize at approximately5.5 V. This voltage is enough to allow the low drop LF33AB regulator to continue supplying the microcontroller, butit is below the supply threshold of the HVLED002 controller (U2), consequently turning it off and stoppingswitching activity in the inverted buck stage.
The voltage on the cathode (J5) referred to the secondary GND during operation is between 9 V (79-9 V for 70 Voutput voltage) and 39 V (79-39 V for 40 V output). Thanks to the D24 Zener Diode, the board can intercept asudden spike above 68 V in the cathode voltage (e.g., short-circuit), by turning on MOSFET Q3 and pulling the FBpin out of its operating range, consequently stopping the switching activity of the HVLED002 controller in order toprotect related componentry.When the power supply is removed, the voltage present on the capacitance C16, C17, C18 and C19 mounted onthe converter output cannot discharged because MOSFET Q2 is turned off. To overcome this issue, dischargecircuitry has been added to switch MOSFET Q7A off and then switch MOSFET Q7B on when the main powerremoval persists, in order to rapidly discharge the VOUT capacitance of the converter through R57.When the power supply is removed, the voltage present on the converter output cannot discharged becauseMOSFET Q2 is turned off. To overcome this, discharge circuitry is included to switch Q7A off and Q7B on whenswitching activity interruption is detected through the secondary auxiliary winding, consequently dischargingconverter VOUT through R57.
The STEVAL-LLL008V1 evaluation kit power board can be configured only to generate output from the high PFflyback converter managed by the HVLED001B controller, or to also apply the buck converter stage managed bythe HVLED002 controller.
Step 1. remove R16 (0R0) to remove power from the HVLED002 controller on the buck stage
Step 2. short-circuit the Q2 Gate-Source of to avoid unintentional powering on of this MOSFET
Step 3. supply with 90 - 265 VAC input voltage on J1
Step 4. place a maximum 1.25 A load between pin 1 (+79 V) and pin 2 (GND) of connector J2max. Power Out/Converter VOUT = 100 W/79 V = 1.25 A
Note: ensure that with the load set at 1.25 A, the input power does not exceed 108 W at 90 VIN_AC and 106 W at265 VIN_AC.
5.2 Flyback and buck converter operation
Step 1. if you do not wish to use the MCU board included in the kit and simply operate the power board at100% LED load (1.4 A), remove R62 (1k0) to toggle correct start-up operation
Step 2. supply 90-265VAC on the power board J1 connector
Step 3. connect a constant voltage (40-70 V) active load between pin1 (A) and pin2 (K) on J5 or a LED Loadrated above 1.4 A constant current
Note: ensure that the current supplied to the LED load is within 1.4 A ± 100 mA
6 STEVAL-LLL008V1 performance and efficiency measurements
Figure 8. STEVAL-LLL008V1 efficiency with ILED=1.4 A at 40 VOUT and 70 VOUT
ILED=1.4
Efficiency [%]
Vin ac [V]
85%
86%
87%
88%
89%
90%
91%
92%
93%
94%
95%
80 110 140 170 200 230 260
Efficiency Full Load @40Vout
Efficiency Full Load @70Vout
AN5467STEVAL-LLL008V1 performance and efficiency measurements
AN5467 - Rev 1 page 10/35
Figure 9. STEVAL-LLL008V1 efficiency at 70 VOUT with 5%-100% dimming
65%
70%
75%
80%
85%
90%
95%
0% 10% 20% 30% 40% 60% 70% 80% 90% 100%
Efficiency 265Vin @Load between 5%-100%
Efficiency 90Vin @Load between 5%-100%
Efficiency [%]
Load [%]
50%
Figure 10. STEVAL-LLL008V1 Total Harmonic Distortion
0%
2%
4%
6%
8%
10%
12%
14%
16%
18%
20%
80 110 140 170 200 230 260
THD
[%]
Vin [Vac]
THD 70Vout
THD 40Vout
AN5467STEVAL-LLL008V1 performance and efficiency measurements
AN5467 - Rev 1 page 11/35
Figure 11. STEVAL-LLL008V1 Power Factor
92.00%
94.00%
96.00%
98.00%
100.00%
80 110 140 170 200 230 260
PF
Vin [Vac]
PF 70Vout
PF 40Vout
Figure 12. STEVAL-LLL008V1 output voltage regulation
36
40
44
48
52
56
60
64
68
72
85 130 175 220 265
Vout
[V]
Vin [Vac]
Vout 70V
Vout 40V
AN5467STEVAL-LLL008V1 performance and efficiency measurements
AN5467 - Rev 1 page 12/35
7 STEVAL-LLL008V1 waveforms
7.1 Power-on and power-off
The figures below show the linear start-up characteristics of the STEVAL-LLL008V1 power board at minimuminput voltage with maximum output power and maximum input voltage with approximately half output power. Inboth cases, the converter output voltage and ILED do not demonstrate any abrupt behavior.The converter output voltage in the second figure shows an overshoot due to the light load. Thanks to the internaldynamic overvoltage protection of the HVLED001B (pin ZCD), the primary switching activity is stopped, stabilizingthe right VOUT.
Figure 13. 90 VIN_AC at 70 V-1.4 A power on
Ch.1: Primary VDrain; Ch.2: Converter VOUT; Ch.3: VCCHVLED001B: Ch.4: LED output current
Figure 14. 265 VIN_AC at 40 V-1.4 A power on
Ch.1: Primary VDrain; Ch.2: Converter VOUT; Ch.3: VCCHVLED001B: Ch.4: LED output current
The following figures show the linear behavior of the main signals when VIN is removed.
Figure 15. 90 VIN_AC at 40 V-1.4 A power off
Ch.1: Primary VDrain; Ch.2: Converter VOUT; Ch.3: VCCHVLED001B; Ch.4: LED output current
Figure 16. 265 VIN_AC at 70 V-1.4 A power off
Ch.1: Primary VDrain; Ch.2: Converter VOUT; Ch.3: VCCHVLED001B; Ch.4: LED output current
The following figures show the main primary side signals (VDS, VGS and ZCD) and the buck VGS managed bythe HVLED002 controller in the steady state condition.
The following figures show the input current shape vs the primary VDrain at minimum output voltage (40 V,approximately half load) for the minimum and maximum input voltages.
Figure 21. 90 VIN_AC at 40 V-1.4 A input current
Ch.1: Primary VDrain; Ch.4: Input Current
Figure 22. 265 VIN_AC at 40 V-1.4 A input current
Ch.1: Primary VDrain; Ch.4: Input Current
The following figures show the burst mode behavior of switching activity.
The following figure highlights the primary VDrain peak voltage with the highest Input Voltage (VDrain peak worstcase) showing that the VDS break down voltage of 800 V is guaranteed.
Figure 25. 265 VIN_AC at 70 V-1.4 A primary VDS maximum spike
Ch.1: Primary VDrain; Ch.2: Input Rectified Voltage
7.3 Current and voltage ripple
The following figures show the current (ILED) ripple for the maximum and minimum output voltages.
Figure 26. 90 VIN_AC at 70 V-1.4 A ILED ripple Figure 27. 265 VIN_AC at 40 V-1.4 A ILED ripple
AN5467Current and voltage ripple
AN5467 - Rev 1 page 16/35
The following figures show the output voltage ripple of the converter stage, showing 1.8 V as the highest peak topeak value.
Figure 28. 90 VIN_AC at 70 V-1.4 A VOUT ripple Figure 29. 265 VIN_AC at 40 V-1.4 A VOUT ripple
7.4 Short-circuit overcurrent protection and overvoltage protection (OVP)
The following figures show the appropriate behavior of the main signals during a short-circuit. As soon as theshort-circuit is detected, the VCATHODE voltage on J5 rises rapidly above the D24 Zener diode threshold of 68 V.The MOSFET Q3 is turned on and the FB pin of the HVLED002 is pulled out of its operating range andconsequently stops the switching activity of the HVLED002, reducing overall consumption to around 1 W andavoiding any component damage due to the short-circuit.
AN5467Short-circuit overcurrent protection and overvoltage protection (OVP)
AN5467 - Rev 1 page 18/35
The following figure shows the converter output voltage behavior during start-up. Considering the light loadcondition, the converter output voltage tends to have an undesired voltage overshoot. The dynamic overvoltageprotection function provided by the HVLED001B controller limits any undesired overshoot. Once the overvoltagelimit value is identified, the appropriate resistor values for the R5, R6 and R14 divider must be calculated toachieve a voltage of 3 V on the ZCD pin (OVP threshold). The HVLED001B therefore interrupts switching activityand it prevents overvoltage from damaging components on the converter output.
AN5467Short-circuit overcurrent protection and overvoltage protection (OVP)
AN5467 - Rev 1 page 19/35
8 STEVAL-LLL008V1 with MCU board on J12
8.1 Dimming on pin2
The following figures show the behavior of the ILED output current when applying between 1% and 100% dimmingfunctionality provided by the MCU board via pin2 on connector J12.
The following figures show the thermal maps on the top and bottom sides of the evaluation kit power board at fullload conditions, with the main components indicated.
Figure 48. 115VIN_AC at 70 V-1.4 A - top
A: L1; B: D3; C: Q1; D: D4; E: T1; F: L2
Figure 49. 230VIN_AC at 70 V-1.4 A - top
A: L1; B: D3; C: Q1; D: D4; E: T1; F: L2
Figure 50. 115 VIN_AC at70 V-1.4 A - bottom
A: Q1; B: R11; C: D2
Figure 51. 230 VIN_AC at70 V-1.4 A - bottom
A: Q1; B: R11; C: D2
AN5467STEVAL-LLL008V1 power board thermal maps
AN5467 - Rev 1 page 24/35
12 Bill of materials
Table 3. STEVAL-LLL008P1 bill of materialsThe STEVAL-LLL008P1 board is supplied with the STEVAL-LLL008V1 kit and is not available for separate sale
Item Q.ty Ref. Part / Value Description Manufacturer Order code
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