The additional circuit block required for dimming is also shown. The lamp arc current is detected through RCS after ignition and coupled onto a dc reference voltage to provide an ac signal with a dc offset at the DIM pin of IC1. When the ac line is switched off, IC2 detects this rapidly and starts a timer. The IRSD dimming control IC enables a simple and low-cost solution that can be used for a wide variety of dimming applications. The feedback circuit will then increase the frequency to decrease the gain of the resonant tank until the valley reaches COM again.
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In each case, only the interface circuit needs to be designed such that it generates the correct dc reference voltage to the dimming control IC.
Figure 6 shows the microcontroller PWM output for each dimming level and the corresponding waveforms for lamp voltage and current. 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. A complete set of schematics and waveforms is included to help designers better understand and design the new circuit.
The VDD supply capacitor C1 is large enough to allow IC2 to continue to run for more than one second after the ac line has been removed.
The IRSD dimming control IC enables a simple and low-cost solution that can be used for a wide variety of dimming applications.
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. When the CFL is first turned on, the control IC sweeps the half-bridge frequency from the maximum frequency down towards the resonance frequency of the high-Q ballast output stage. Existing interface circuits include a 1-toVdc interface, digitally-addressable lighting interface DALItriac-based wall dimmers, three-way lamp sockets, power line communications, and wireless communications.
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 complete ballast control, dimming feedback loop and fault protection are included in the IC, so few external components are needed.
IRS2530DSTRPBF IC DIMMING BALLAST CTRL 8-SOIC IRS2530DSTRPBF 2530 IRS2530 IRS2530D IRS2530DS 2530D
Block diagram of four-level switch-dimming ballast. 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. After VDD has discharged below the minimum operating voltage of IC2 the microcontroller will shut off. During ir2s530d, the resonant tank is a series-LC circuit with a high Q-factor.
This causes the amplitude of the lamp current to then increase or decrease 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 lamp filaments are preheated as the frequency decreases and the lamp voltage and load lev increase Figure 2.
The higher the duty cycle, the higher the DIM pin voltage and the higher the brightness level. The lamp arc current is detected through RCS after ignition and coupled onto a dc reference voltage to provide an ac signal with a dc offset at the DIM pin of IC1.
If power is restored within one second, the output square-wave duty-cycle is reduced and the dimming level is reduced by one step. When the ac line is switched off, IC2 detects this rapidly and starts a timer.
Electronic ballasts for dimming fluorescent lamps require a control interface for the user to set the desired lamp-brightness level. 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. 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.
The full application circuit is shown in Figure 5. 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.
The lamp requires a current to preheat the filaments, a high-voltage signal for ignition, and a high-frequency ac current to maintain operation during the running mode. 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 dimming function is ifs2530d by combining the ac-lamp-current measurement Figure 3 with the dc reference voltage at a single node.
This article explains how the IRSD operates and presents a igs2530d four-level switch-dimming application circuit built around this IC. The board is a two-layer design with a very small form factor for driving a W fluorescent lamp.
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. After ignition and during the running mode, the tank is a series-L, parallel-RC circuit with a Q-factor somewhere between a high and low value depending on the lamp dimming level.
If the dc reference is decreased, the valley will decrease below COM. The additional circuit block required for dimming is also shown.