Intelligent Lighting & Control
Intelligent Lighting & Control
- Design Partners
- LED Drivers for Human Centric Lighting
- Lighting Communications Development Platform
- PIC16F1947 Lighting Control Console
- PIC16F1788 Wireless DC/DC LED Driver (Proof of Concept)
- PIC16F1509 Solar Powered LED Security Lamp (Proof of Concept)
- PIC12F752 AC/DC LED Driver (Proof of Concept)
- PIC16F1508 DALI Dimmable Fluorescent Ballast (Proof of Concept)
PIC16F1508 DALI Dimmable Fluorescent Ballast (Proof of Concept)
Rapid Start Intelligent Fluorescent Ballast
- Universal input 1st stage peak current mode boost supply
- Resonant LCC inverter for lamp drive
- 120 VAC – 240 VAC Input
- Single hardware platform
- Firmware based configuration
- Active Power Factor Correction (PFC)
- 0.95 or better (0.98 at full load)
- PIC16F1508 Controlled Topology
- Core Independent Peripheral Integration
- 5-bit DAC
- Configurable Logic Cell (CLC)
- Numerically Controlled Oscillator (NCO) Comparators
- Smooth digital dimming control via NCO linear frequency control
- Analog input or serial e.g. DALI communications
- MCP1416 FET Driver
Theory of Operation
This proof of concept design is a rapid start resonant fluorescent power supply with active PFC.
- Peak current mode DCM boost converter at 150kHz+ switching frequency
- Internal 5-bit DAC used for voltage envelope reference
- High Performance Comparators used for peak current mode limits
- CLC for overall integration and SR-Latch
- NCO for accurate resonant frequency generation
- A boost-strapping power supply consisting of 2 Zener diodes is used to supply power to the FET driver and the microcontroller at startup.
- The onboard DAC is used as a voltage divider from the external rectified AC supply voltage to supply a line voltage envelope reference for the power factor correcting peak current mode boost converter. Since the DAC has a selectable tap point the amplitude of the reference is controllable from software.
- A small shunt resistor is used to measure the inductor current and the high performance comparator is used to detect when the inductor current reaches the reference current supplied.
- The CLC is used as the heart of the controller set up as an SR-Latch. The latch is set by a PWM control signal which turns on the switching FET and starts a near-linear increase in inductor current.
- When the inductor current reaches the reference envelope the comparator trips and resets the output SR-Latch in the CLC. The next pulse starts when the PWM starts its next switching cycle.
- An ADC is used to roughly regulate the output of this boost converter to above the line voltage (typically 200V or 400V depending on input voltage).
- A resonant half-bridge LCC drive circuit is then used to apply this signal to the lamp.
- At startup a high frequency signal is generated to heat the lamp filaments.
- Once the filaments are on temperature the frequency is quickly reduced to the point where a striking potential is generated by the resonant circuit and the lamp arc is established.