ON Semiconductor CCRACGEVB AC LED Lighting Evaluation Board User Manual

ON Semiconductor CCRACGEVB AC LED Lighting Evaluation Board

Product Information

The CCRACGEVB is an AC LED Lighting Evaluation Board Using Constant Current Regulators (CCR). It allows engineers to evaluate six different circuit topologies that cover a wide input voltage range of 12 VAC to 250 VAC. The board is designed to help engineers  balance circuit efficiency, power factor, total harmonicdistortion, total cost of bill of materials, and input voltage range to meet various customer requirements.

The CCRACGEVB is equipped with multiple jumpers that allow for the reuse of circuit components in different topologies. Test points are also available at major nodes to collect circuit performance data and enable engineers to insert their own components for circuit variations. The components used in the board were selected to accommodate a large input voltage range, but designers can review their specific application requirements and opt for smaller or lower- cost parts if suitable.

The CCRACGEVB features different topologies for LED drivers, including options for dimming and non-dimming configurations. It also includes an inrush current limiter and comes with an LED board.

Product Features:

• Input Voltage: 12 VAC to 250 VAC
• CCR Current Options: 20 mA, 30 mA, 50 mA, 150-350 mA
• Topologies :
  • No Dimming, With Output Capacitance, With Triac Dimming
  • No Dimming, With Triac Dimming
  • No Dimming, With Triac Dimming

Product Usage Instructions

Straight LED Driver, Non-dimming (120 VAC Example):

The Straight LED driver circuit is the simplest with the lowest bill of materials (BOM) and highest power factor (PF). To set up the CCRACGEVB for the Straight LED driver non-dimming topology, follow the steps below:

1. Place the following jumpers onto the EVB:
   • J1
   • J13
   • J18
   • J19
   • J20
   • J22
   • J26
2. Refer to Appendix A for reference data.
3. Calculate the maximum forward voltage drop across the LED string using Equation 1 in the manual.
4. Calculate the minimum forward voltage drop across the LED string using Equation 2 in the manual.
5. Adjust the total LEDs and input peak voltage values accordingly.

For more detailed instructions and information on other circuit topologies, please refer to the CCRACGEVB User’s Manual.

Six Different Circuit Topologies Covering Smallest Bill of Materials to Widest Input Voltage: 12 VAC to 250 VAC.

Introduction

Engineers developing solid-state lighting control systems need to balance circuit efficiency, power factor (PF), total harmonic distortion (THD), total cost of bill of materials (BOM) and input voltage range to cover large geographic regions and aesthetics to satisfy different customer requirements. The CCRACGEVB allows engineers to evaluate six different topologies as they approach this difficult balancing act..

The CCRACGEVB (see Figure 1) has an input voltage range of 12 VAC to 250 VAC and showcases the NSIC20x0JBT3G series of 120 V CCRs and the NSI50150ADT4G (150 – 350 mA Adjustable) CCR. It has circuit topologies for “Straight LED Driving”, “Capacitive Drop LED Driving” and “Chopper LED Driving”, all with and without dimming by typical triac dimmers. It has a simple current inrush limiting circuit to suppress the impact of initial high inrush currents and power spikes.

CCRACGEVB

The CCRACGEVB is set up with multiple jumpers to allow reuse of circuit components in the different topologies. There are test points at all the major nodes to enable the collection of circuit performance data and also allow engineers to insert their own components for circuit variations. The components for CCRACGEVB were selected to allow evaluation over a large input voltage range. Designers should review their specific application requirements and determine if smaller or lower cost parts could be selected in place of those used here. The application note is broken up into sections covering the different circuits. A brief circuit description for each topology will be provided with the jumpers selected together with data collected at multiple voltages

CCRACGEVB Features:
Input Voltage

• 12 VAC to 250 VAC
  CCRs

• NSIC2020JBT3G 120 V 20 mA SMB

• NSIC2030JBT3G 120 V 30 mA SMB

• NSIC2050JBT3G 120 V 50 mA SMB

• NSI50150ADT4G 50 V 150−350 mA DPAK

Topologies

• Straight No Dimming, With Output Capacitance,
  With Triac Dimming

• Cap−Drop No Dimming, With Triac Dimming

• Chopper No Dimming, With Triac Dimming

Inrush Current Limiter
LED Board (supplied with CCRACGEVB)

• 10x XLAMP MX−6S LEDs

Straight LED Driver, Non−dimming (120 VAC Example):
The Straight LED driver circuit is the simplest with the lowest BOM and highest PF. To setup the CCRACGEVB for the Straight LED driver non-dimming topology, place jumpers according to Table 1.

JUMPERS PLACED ONTO THE EVB

The AC input is rectified using an AC bridge (D1 – D4). A CCR (CCR3, 4, 5 or 6) controls the current through the LED string. The LEDs will be turned on at double the AC mains frequency (120 Hz in the USA). The duty cycle is about 60%. Figure 2 depicts the schematic with the evaluation board reference designators

VF- Total LEDs
The maximum forward voltage drop across the LED string is determined by the minimum input peak voltage minus the minimum regulating voltage for the CCR. Assuming −10% tolerance of AC mains:

The minimum forward voltage drop across the LED string is determined by the maximum input peak voltage minus the breakdown voltage of the CCR.
Assuming +10% tolerance of AC mains:

Conduction Time (TON)
The conduction time (on time) of the LED string is based on the VF−TotalLEDs. The rectified voltage needs to rise above the forward voltage of the LEDs before they begin to conduct and the CCR regulates the current through them. The TON conduction time (%) calculation for the typical 120 VAC is the following:

Design Trade−off

• The lower the VF−TotalLEDs:

  • Higher %TON conduction time , more light output
  • Lower efficiency due to higher power lost across
    CCR

• The higher the VF−TotalLEDs:

  • Higher efficiency due to less power lost across CCR
  • Lower %TON conduction time, less light output

Straight LED Driver, Non−dimming, with Output Capacitor (120 VAC Example): This circuit will have a higher efficiency compared to the straight LED driver. To set up the CCRACGEVB for the Straight LED driver non-dimming topology with output Capacitor, place jumpers according to Table 2. Figure 3 depicts the schematic with the evaluation board reference designators.

Table 2. JUMPERS PLACED ONTO THE EVB

The AC input is rectified using an AC bridge (D1 – D4) and charges the capacitor (C7 & C8 in series). The voltage on the capacitor will be equal to or a little below the peak rectified voltage. A CCR (CCR3, 4, 5 or 6) controls the current through the LED string. The charge on the capacitor allows the CCR to continue providing current to the LED string when the rectified AC voltage is below the VF−TotalLEDs. The Inrush current limiter (T1, R2 & C6) can be employed to limit the inrush current or current spike from a power surge. As the capacitor C6 charges, T1 will turn on and provide a low impedance bypass.

Straight LED Driver, with Triac Dimming (120 VAC Example):
This circuit incorporates an additional circuit to provide a minimum load for the Triac dimmer. To set up the CCRACGEVB for the Straight LED driver dimming topology, place jumpers according to Table 3. Figure 4 depicts the schematic with the evaluation board reference designators.

This circuit comprises R3 – R7, R17, CCR1, M1, Q1 and D8. The selection of R3/4 and the value of R7 are based on the Triac dimmer. The selection of R3 & R4 in parallel (5.0 K) and R7 & R17 in series (50 ) have produced good results.

Cap−Drop LED Driver Topology, Non−dimming (120 & 230 VAC Example):
The Cap-Drop circuit is selected for high efficiency and a low BOM cost. To set up the CCRACGEVB for the Cap-Drop LED driver non-dimming topology, place jumpers according to Table 4. Figure 6 & Figure 7 depict the schematics with the evaluation board reference designators. Appendix D shows the 120 VAC example and Appendix E provides its 230 VAC counterpart

The operation of the Cap-Drop circuit is very similar to the straight LED circuit with the advantage of improved efficiency because the AC voltage is reduced to be a little over the forward voltage of the LED string.

Inrush Current Limiter
The Inrush Current Limiter (Figure 5) is incorporated to reduce the surge current if power is connected at the peak of the AC input. At turn on, the 6.8 K resistor will limit the current as the Darlington MJB5742 will be off and the 33 F capacitor will appear as a short. As the capacitor charges the Darlington will turn on and provide a low impedance bypass.

Cap−Drop LED Driver Topology with Triac Dimming (120 VAC Example):
To set up the CCRACGEVB for the Cap-Drop LED driver dimming topology, place jumpers according to Table 5. Figure 8 depicts the schematic with the evaluation board reference designators.

Table 5. JUMPERS PLACED ONTO THE EVB

This circuit has the addition of a Triac Edge Detect circuit to switch the LED string on and off. The circuit is comprised of: D5, D6, D10, CCR2, R12, R13 & M3. The circuit detects the triac waveform and turns the MOSFET M3 on. CCR2 provides a basic load to the triac to keep it functioning correctly.

Chopper LED Driver Topology 85 VAC to 250 VAC, Non−dimming:
The Chopper circuit is selected for high efficiency and a wide input voltage range. To set up the CCRACGEVB for the Chopper LED driver non-dimming topology, place jumpers according to Table 6. Figure 9 depicts the schematic with the evaluation board reference designators

Table 6. JUMPERS PLACED ONTO THE EVB

The operation of the Chopper circuit can be broken into two sub-circuits; a simple buck and a straight LED driver with output capacitance. The AC is then rectified using an AC bridge (D1 – D4). A CCR (CCR3, 4, 5 or 6) controls the current through the LED string. The Buck circuit is comprised of a voltage divider R8 & R16/R10 that are used to set the voltage through TL431, that the MOSFET switch M2 turns off. When the output from the bridge is below the set voltage, M2 is ON and capacitor C7/C8 is charged. If the voltage is above the threshold voltage Vf of the LED string, then the CCR will limit the current through the LEDs. When the voltage is above the set voltage, the MOSFET is turned OFF. The LEDs then draw current from the charge on capacitor C7/C8 which is limited by the CCR

Chopper LED Driver Topology 85 VAC to 250 VAC, with Triac Dimming:
This circuit is the same as Figure 9 with the addition of the Triac Dimming Detect circuit as described in the Cap-Drop description above (Figure 8). To setup the CCRACGEVB for the Chopper LED driver non-dimming topology, place jumpers according to Table 7. Figure 10 depicts the schematic with the evaluation board reference designators.

Table 7. JUMPERS PLACED ONTO THE EVB

APPENDIX A

Straight LED Driver, Non−dimming (120 VAC Example)
Table 8. PERFORMANCE EVALUATION

Figure 13. Straight LED Driver, Non−dimming Circuitry Flow (120 VAC)

Straight LED Driver, Non−dimming, with Output Capacitor (120 VAC Example)
Table 9. PERFORMANCE EVALUATION

Figure 16. Straight LED Driver, Non−dimming w/Cap Circuitry Flow (120 VAC)
Straight LED Driver, with Triac Dimming (120 VAC Example)
Table 10. PERFORMANCE EVALUATION

APPENDIX D

Cap−Drop LED Driver Topology, Non−dimming (120 VAC Example)
Table 11. PERFORMANCE EVALUATION

APPENDIX E
Cap−Drop LED Driver Topology, Non−dimming (230 VAC Example)

Table 12. PERFORMANCE EVALUATION

APPENDIX F
Cap−Drop LED Driver Topology with Triac Dimming (120 VAC Example)

APPENDIX G
Chopper LED Driver Topology 85 VAC to 250 VAC, Non−dimming
Table 13. PERFORMANCE EVALUATION (85 VAC)

Table 14. PERFORMANCE EVALUATION (230 VAC)

APPENDIX H
Chopper LED Driver Topology 85 VAC to 250 VAC, with Triac Dimming

Table 15. JUMPERS FUNCTION DEFINITION

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References

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