The microcontroller IC2 generates a square-wave voltage at pin 5 that is RC-filtered to produce the dc dimming reference voltage at the DIM pin. Capacitor CPH is used to program the frequency sweep time for preheat and ignition of the lamp. At turn-on, the voltage at the VCO pin will ramp up from 0 V causing the frequency to decrease from the maximum frequency down to the minimum frequency. This circuitry includes a dimming reference signal, a lamp-current sensing and feedback signal, and a summing circuit for closed-loop control of the lamp current. The dimming function is realized by combining the ac-lamp-current measurement Figure 3 with the dc reference voltage at a single node. This simplification of the ballast circuitry allows designers to focus their creativity on developing the different types of dimming interfaces required for each new application.
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IRSD Datasheet(PDF) – International Rectifier
ids2530d Prior to that, Tom was e mployed by Knobel Lighting Components in Switzerland where he designed dimmable electronic ballast systems for a variety of applications. To fulfill these requirements, the electronic ballast circuit first performs a low-frequency ac-dc conversion at the input, followed by a high-frequency dc-ac conversion at the output.
This article explains how the IRSD operates and presents a complete four-level switch-dimming application circuit built around this IC. Once the lamp ignites, the lamp current is controlled such that the lamp runs at the is2530d power and brightness level.
IRSD Datasheet(PDF) – International Rectifier
The lamp requires a current to preheat the filaments, a high-voltage signal for ignition, lde a high-frequency ac current to maintain operation during the running mode. Electronic ballasts for dimming fluorescent lamps require a control interface for the user to set the desired lamp-brightness level.
The four-level switch-dimming circuit described in this article is only one application where dimming can be achieved without additional wiring. The board is a two-layer design with a very small form factor for driving a W fluorescent lamp. The VDD supply capacitor C1 is large enough to allow IC2 to continue to run for more than one second after the ac jrs2530d has been removed.
IRS2530DSTRPBF IC DIMMING BALLAST CTRL 8-SOIC IRS2530DSTRPBF 2530 IRS2530 IRS2530D IRS2530DS 2530D
If the ,ed line is removed for more than one second, the dimming level will not change. After ignition and during the running mode, the tank is a series-L, parallel-RC circuit with a Q-factor somewhere irs25530d a high and low value depending on the lamp dimming level.
When the ac line is switched off, IC2 detects this rapidly and starts a timer. The dimming function is realized by combining the ac-lamp-current measurement Figure 3 with the dc reference voltage at a single node. The lamp filaments are preheated as the frequency decreases and the lamp voltage and load current increase Figure 2.
To dim the fluorescent lamp, the frequency of the half-bridge is increased, causing the gain of the resonant tank circuit to decrease and therefore the lamp current to decrease. The frequency keeps decreasing until the lamp voltage exceeds the lamp ignition voltage threshold and the lamp ignites. If the dimming level was already at minimum then it will cycle back to maximum.
A complete set of schematics and waveforms is included to help designers lef understand ,ed design the new circuit. The microcontroller IC2 generates a square-wave voltage at pin 5 that is RC-filtered to produce the dc dimming reference voltage at the DIM pin.
At turn-on, the voltage at the VCO pin will ramp up from 0 V causing the frequency to decrease from the maximum frequency down to the minimum frequency. The complete reference design Figure 7 shows the through-hole components mounted on the top-side and the surface-mounted components on the bottom side not shown.
The complete ballast control, dimming feedback loop and fault protection ira2530d included in the IC, so few external components are needed. A microcontroller and pulse detection circuit is used to sense each recycling of the ac line voltage, change the dimming reference, and store the previous dimming level.
As the frequency continues to fall towards the resonance frequency of the tank circuit, the lamp voltage increases until the lamp ignites. During DIM mode, the IRSD adjusts the oscillator frequency in order to maintain the amplitude of this feedback signal and control the lamp current for dimming.
This simplification of the ballast circuitry allows designers to focus their creativity on developing the different types of dimming interfaces required for each new application. The higher the duty cycle, the higher the DIM pin voltage and the higher the brightness level. Block ird2530d of four-level switch-dimming ballast. The IRSD provides all of the necessary ballast functions, fault detection and dimming control required for operation of fluorescent lamps.
This ledd the amplitude of the lamp current to then increase or decrease for dimming. During pre-ignition, the resonant tank is a series-LC circuit with a high Q-factor. A closed-loop feedback circuit is then used to measure the lamp current and regulate the current to the dimming reference level by continuously adjusting the half-bridge operating frequency. The IRSD dimming control IC enables a simple and low-cost solution that can be used for a wide variety of dimming applications. The high-frequency ac square-wave voltage then drives the resonant tank circuit and becomes filtered to produce a sinusoidal current and voltage at the lamp.
The IRSD irs253d0 control IC includes the feedback control circuit described above, as well as all of the necessary functions to preheat and ignite the lamp and to protect against fault conditions such as open-filament failures, lamp non-strike and mains brown-out.