EL SEGUNDO, CA. October 1997 - International Rectifier (IR), the power semiconductor expert, is introducing new product families that promise to help substantially reduce the size of compact ballasts and AC/DC adapters. The IR5xH, IR5xHD, IR0xH and IR0xHD Series are high voltage integrated half-bridges that combine the power MOSFET output stage in a half-bridge configuration with a high voltage integrated circuit controller into a single 9-pin SIP package. The package only takes up 85 mm of board real estate, yet performs the complete set of high voltage power conversion switching and control functions.

Compact fluorescent lamps are becoming popular consumer products since older generations of fluorescent lamps are bulky with the ballast taking up much of the space and weight. The new generation of compact ballasts are much smaller, thanks to high frequency zero voltage switching power converter designs. Another rapidly growing product type, the AC/DC adapter, is also downsizing very quickly by using high frequency and high efficiency zero voltage or currentswitching topologies. The new integrated half-bridge products from IR are ideal for these compact, low power and high efficiency designs.

The IR51H and IR52H series of integrated half-bridges include: a high side power MOSFET; a low side power MOSFET; a low noise high side gate drive circuit; a low noise low side gate drive circuit; a 555 type oscillator; deadtime and delay matching; UV lockout; and Vcc supply with Zener clamp. The power MOSFETs are avalanche rated. Versions are available that have breakdown voltages rated at 250, 300, 400, or 500 V and the various offerings in power MOSFET sizes are targeted for the different power converter output levels from 5 to 30 W. The high side gate drive circuits have common mode capabilities of floating to above the breakdown rating of the power MOSFET. The level shifting circuits have dv/dt immunity from slow to fast switching transients up to 50 V/ns. Both the high side and low side MOSFET are driven from gate drive voltages that can be as high as 15.6 V, which is internally limited by the Zener clamp. The internal oscillator is similar to the 555 type timer requiring an external resistor and capacitor to program the frequency. Internal deadtime is set at 1.2 µs. The delay times and dead times are matched very tightly to achieve a 50% duty cycle. The IR51H differs from the IR52H Series by having a reverse polarity from the input control pin to the output of the half-bridge. The IR51HD and IR52HD Series add internal bootstrap diodes from the Vcc supply pin to the floating gate drive channel.

The IR53H and HD Series and the IR54H and HD Series add micropower startup, shutdown mode and deadtime with a very low temperature coefficient. The micropower startup circuit limits the Vcc supply current to less than 150 µA, which would allow the use of a ¼-W resistor for startup and a charge pumped circuit using two diodes and a capacitor to supply Vcc during normal operating conditions. The shutdown mode turns off oscillation and both power MOSFETs. The tight and temperature-independent deadtime specifications allow stable operation to a higher frequency.

The IR01/02/03/04H and HD series of products are similar to the 5xH and 5xHD Series except for the omission of the 555 type oscillator which is replaced by logic inputs. These series of products are designed to be used with an external controller while still simplifying the power conversion circuit by providing the complete interface function from a low level logic signal to the high voltage power MOSFET output. The different control versions differ in the logic states and deadtime.

The IR5xH and HD Series and the IR0xH and HD series of products are designed for high efficiency low power converters. The junction to air thermal resistance of the 9-pin SIP package is rated at 60ºC/W, and it can be reduced to 30ºC/W with a clip-on heatsink. Therefore, the power dissipation of the integrated half-bridge stage can be as high as 1.3 to 2.7 W for a maximum operating ambient temperature of 70ºC.

IR has demonstrated the effectiveness of the integrated half-bridge product by the design of a ballast circuit board that is smaller in area than the base of a popular table top compact lamp. The demonstration ballast design uses the IR51H420 for either 110 VAC or 220 VAC input, and incorporates additional value-added features such as pre-heating, open lamp protection and lamp current control. The demonstrated design will be available in the form of a design kit.

Samples and production quantities of the IR51H and HD Series and the IR01H and HD series of products are available from stock now. Samples for other control and power variations will be available as customer specified requests. Volume production quantities are available with a lead time of 8-12 weeks.

Reference Design: Compact Ballast