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RD0801

5. IRS2530D DIM8

The IRS2530D is an application specific solution for dimming CFL and TL lamps in CFL or

matchbox (small size ballasts) applications. It integrates all of the necessary functions for

preheat, ignition and dimming control of the lamp, plus lamp fault protection, low AC-line

protection, lamp exchange auto-restart, and a 600V half-bridge driver into a standard SO8

or DIP8 package.

The IRS2530D includes adaptive zero-voltage switching, non-zero voltage switching

(ZVS) protection, as well as an integrated 600V bootstrap MOSFET. The heart of this IC is

a voltage-controlled oscillator (VCO) with a dimming reference/feedback input. One of the

biggest advantages of the IRS2530D is that it uses the VS pin (the mid-point of the half-

bridge) for over-current protection and to detect non-ZVS conditions. The IRS2530D uses

the RDSon of the low-side half-bridge MOSFET for current sensing each cycle when the

low-side MOSFET is on. An internal 600V MOSFET connects the VS pin to the VS-

sensing circuitry and allows for the VS pin to be accurately measured during the time

when pin LO is high, while withstanding the high DC bus voltage during the other portion

of the switching cycle when the high-side MOSFET is turned on. This eliminates the need

for an external, precision current sensing resistor that is typically used to detect over-

current. Please refer to the IRS2530D datasheet for further information including electrical

parameters, a state diagram and a complete functional description.

As a result of the IRS2530D features, the IRPLDIM4E Reference Design is a complete

dimming ballast solution that includes lamp fault protection, low AC line protection, lamp

exchange auto-restart, and reduces component count and ballast size.

6. Circuit Description

The schematic for IRPLDIM4E is shown in Figure 7.1. The bill of materials with the

component values is shown in Table 8.1.

The ballast incorporates a fuse, input rectifier, EMI filter, bus capacitor, half-bridge,

dimming control and output stage. The output stage is a series-L, parallel-RC resonant

circuit consisting of an inductor (LRES), capacitor (CRES), and lamp. The AC line input

voltage is rectified to provide a bus voltage of approximately 300VDC. The start-up

resistors, RVCC1 and RVCC2, are sized such that they supply the micro-power current

during under-voltage lockout (UVLO) mode and determine the AC line voltage where the

ballast turns-on. When VCC exceeds the startup threshold (VCCUV+), the IRS2530D

begins to oscillate and the charge pump circuit (CVS, DCP1 and DCP2) supplies the

current to VCC while maintaining the internal VCC zener clamp at 15.6V.

The IRS2530D controls the frequency of the half-bridge for satisfying the lamp operating

modes. These include lamp preheat, lamp ignition, dimming, low AC line protection and

lamp/ballast fault protection.