LED driver solution for MR16 and similar retrofit lamps
Shaping the input current as a square is the best solution for control: it keeps its value (i.e., the transformer and dimmer load current) above the required minimum for the whole cycle of the line voltage.
This control is obtained using components R8 (sense resistor), R7, and C9. R7 and C9 provide the average MOSFET current, which is the same as the average input current; the MAX16834 maintains this value constant throughout each cycle of the input voltage.
Since this solution does not include electrolytic capacitors, the LED current is a rectified sinusoid (without dimmer) or a rectified sinusoid cut for a part of the angle (with dimmer), because energy is not stored between one cycle of the AC voltage and the following (Figure 3).
Figure 3. LED current is a rectified sinusoid, with frequency equal to twice the line voltage frequency.
The MAX16834 features output overvoltage protection (OVP). With OVP, if the LEDs are disconnected or open the driver turns off and the driver is not damaged.
Test results
This reference design board was tested under these conditions:- Electronic transformer: Lightech LET-60
- Input voltage of the electronic transformer: 120VAC, 60Hz
- Input voltage of the driver circuit: 12VAC, 60Hz modulated at 40kHz
- Output: 4 series LEDs
- LED power: 4.2W
- Efficiency: 77%
- Input power factor: 0.943
| Input Voltage | Maker | Model |
| 120VAC | B+L Technologies | FX95100 |
| 120VAC | Eaglerise Electric Electronic (Foshan) Co Ltd. | B04558F1 |
| 120VAC | Q Tran®, Inc. | QT10-120/12-NTP-RC |
| 120VAC | Hatch | RS1260M-LED |
| 120VAC | Hatch | VS12-60WD |
| 120VAC | Hatch | VS12-75WD |
| 120VAC | Hatch | RS12-60PILB-LED |
| 120VAC | Hatch | RS12-80m |
| 120VAC | Hatch | RS12-15m |
| 120VAC | Hatch | RS12-30m |
| 120VAC | Lightech | LET-60 |
| 120VAC | Lightech | LVT-60 |
| 110VAC | Nobile | AFM-70KC |
| 120VAC | Progress Lighting® | P8560-31 |
| 120VAC | Wang House Technology | WH-801E6A |
| 120VAC | Wang House Technology | WH-601E2CA-2M |
| 220VAC | Hatch | RS12-60-230m |
| 220VAC | Leadman Electronics® | KY-05036S-12 |
| 220VAC | Ly SHLY | 021-66770066 |
| 220VAC | Nobile | EN-35M |
| 230VAC | Nobile | EN-35ST |
| 230VAC | Nobile | EN-60D2 |
| 80-270VAC | NVC® Lighting Technology Corporation | NLD-15W/12V |
| 220VAC | OSRAM® | ECO-ET 60/220 |
In addition, this solution has been tested to work with the following dimmer/electronic transformer combinations.
| Input Voltage | Dimmer Maker | Dimmer Model | Electronic Transformer |
| 120V | Lutron® Electronics | Nova NELV-450 | Hatch R12-60M-LED |
| B + L FX95100 | |||
| 120V | Lutron Electronics | Skylark SELV-300P | B + L FX95100 |
| 120V | Lutron Electronics | Diva DVELV-300P | Hatch R12-80M |
| B + L FX95100 |
This solution has been tested to work correctly with the following dimmer/magnetic transformer combinations.
| Input Voltage | Dimmer Maker | Dimmer Model | Magnetic Transformer |
| 120V | Lutron Electronics | Nova NLV-600 | Q Tran Qt10-120-12-NTP-PC10VA |
| Eaglerise B04558F1 40VA | |||
| Schneider Electric® 150VA150SV43A (Square D) | |||
| 120V | Lutron Electronics | Diva DLV-600P | Q Tran Qt10-120-12-NTP-PC10VA |
| Eaglerise B04558F1 40VA | |||
| 120V | Lutron Electronics | Skylark SLV-600P | Q Tran Qt10-120-12-NTP-PC10VA |
| 120V | Lutron Electronics | Maestro MALV-600 | Q Tran Qt10-120-12-NTP-PC10VA |
| Schneider Electric 150VA150SV43A (Square D) |
Test procedure
- Turn off the 120VAC/230VAC power supply.
- Connect the input of the trailing-edge dimmer (if present) to the power supply.
- Connect the output of the dimmer to the input of the electronic transformer. Alternatively, connect the input of the transformer to the power supply if no dimmer is present.
- Connect the output of the dimmer to the VIN1 and VIN2 board inputs.
- Connect the LEDs between LED+ (anode) and LED- (cathode).
- Turn on the power supply.
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