IRPLDIM2U International Rectifier, IRPLDIM2U Datasheet - Page 6

• Manufacturer Part Number: IRPLDIM2U
• Description: BALLAST DIM DIG 32W/T8 120VAC
• Manufacturer: International Rectifier

Specifications of IRPLDIM2U

• Main Purpose: Lighting, Ballast Control
• Utilized Ic / Part: IR21592
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / Rohs Status: Not Compliant
• Other names: *IRPLDIM2U

The shutdown signal (RB4) enables or disables the IR21592. When high, the lamp is off and the IR21592 is
disabled with minimal current flowing. When low, the lamp is on. The PIC16F628 has control of this line and
determines if lamp should be on or off based on fault conditions and user requested settings from the DALI. There
are two signals used for fault detection, lamp-out (RB6), and fault (RB5). The lamp-out signal indicates the pres-
ence of a lamp or lamp fault. When the lamp is removed the lamp-out signal is pulled up to VDD by the pull-up
resistor R17 and the software forces the IR21592 to shutdown. When the lamp is changed, this pin goes to 0
Volts, the microcontroller turns the IR21592 on again and the lamp re-starts automatically. Other fault conditions
are indicated by the fault signal (pin FMIN of the IR21592). A low on the fault signal indicates that the IR21592 is
in a fault state (the IR21592 turns off automatically in fault conditions such us VCC fault, over-current, failure to
strike or low AC line and will remain in this FAULT state until the IC is reset.
The IR21592 requires a 0.5-volt to 5-volt analog voltage (in pin DIM) to perform dimming, thus 0.5 volts corre-
sponds to the 1% arc power level and 5 volts corresponds to the 100% arc power level. The PIC16F628 provides
a pulse width modulated signal on pin RB3 that is filtered with a single RC network (R25 and C17). This provides
an analog voltage for dimming. The micro can change the dim voltage from 0.5V to 5V by changing the duty cycle
and therefore generate 256 different voltage levels for the IR21592. To conform to the digital dimming require-
ments, the output is logarithmic rather than linear. Since the human eye is much more sensitive to lower light levels
than high levels, the logarithmic output appears to be linear. Therefore the PIC16F628 is programmed to produce
a logarithmic voltage and the IR21592 drives the lamp arc power (Figure 5).
The microcontroller can also change the fade time by controlling the speed in which the duty cycle changes.
The relation between light level and dim level can be tuned according to specific needs. The minimum light level
can be changed by adjusting RMIN, and the maximum level can be changed adjusting RMAX. RMIN sets the
lower phase boundary corresponding to minimum lamp power when VDIM = 0.5V, and RMAX sets the upper
phase boundary corresponding to maximum lamp power when VDIM = 5V. RMAX must be set after RMIN.
The software
The software to implement the DALI is quite large but simple to understand when broken into some elementary
functional blocks. Figure 6 outlines the basic flow of the software in its most simplified form (the details source
code is available in a CD enclosed with the Reference Design Kit).
6
5
4
3
2
1
0
85
115
Logarithmic Voltage Output
145
Digital Input
175
205
Fig. 5 Dimming Chacteristics
235
100
80
60
40
20
0
85
115
Logarithmic Arc Power Output
145
Digital Input
175
205
IRPLDIM2U
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