IN-PLUG

© Copyright 2005-2007 - ASIC Advantage, Inc. – All rights reserved

- Revision 11 – April 02, 2007

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INTRODUCTION:

The IPS401 is based on the IPS101 core technology. It has all the qualities of AAI’s PFC controller with low

component count and a self-oscillating mode for low EMI and low switching losses, but it has been optimized for

offers the same key features of its predecessor but in most applications does not require input and output electrolytic

capacitors.

OPERATING DESCRIPTION:

3-input current multiplier:

The IPS401controller incorporates a 3-input current-mode multiplier that monitors a constant loop gain and ensures

a good stability and response over a broad range of input AC voltages and output loads. It also forces the current

drawn from the AC line to be proportional to the instant line voltage thus resulting in a power factor close to unity.

This ensures to pass the AC line harmonic limits of the EN61000-3-2 standard for Class C equipment with all

application requirements.

Voltage error amplifier:

The IPS401 includes a voltage error amplifier between pin 6 and pin 7. It’s non-inverting input is connected to an

internally trimmed 0.50V reference. Its output connected to pin 7,

is internally connected to a V-to-I

converter/multiplier. As indicated in the typical application schematic of figure 1, pin 6 and pin 7 are used for the

following purposes:

(a) DC output overvoltage protection:

- The output DC voltage is set by the number and voltage characteristics of the output LED diodes in series.

- The number of zener diodes involved in the overvoltage protection circuitry is determined by

ΣVz min > Vout

(b) Loop feedback, linear dimming, PWM dimming.

(c) the loop feedback compensation network R1, C1, C2 (see Fig. 1) provides a suitable network for most

applications. More complicated schemes are possible for demanding applications where transient response is

paramount.

MOSFET current control:

The recommended use of the IPS401 is in a non-isolated boost converter operating from raw rectified AC voltage.

The FET, diode, and boost inductor generate a regulated output voltage that exceeds the peak voltage of the AC

input voltage.

The maximum current increases with increasing output power demand. Once Vcc is established, the control logic

turns the MOSFET on. The current in the inductor and MOSFET is sensed by resistor R9. The output power of the

circuit is determined by the value of this current.

When the current reaches the peak value set by the internal multiplier circuit, the MOSFET is switched off and the

current in the inductor decreases as it's energy is dumped into the output capacitor and load LEDs. In the

recommended application circuit, the inductor current decreases to zero, at which time the control logic turns the

MOSFET on again. The system is therefore self-oscillating and does not require a dedicated oscillator. Note that the

frequency varies with input voltage and output load, but:

- the frequency variation is low (less than 2:1).

- the frequency variation helps to reduce conducted EMI.

- the frequency decreases with increasing load. Lower frequency implies higher efficiency.

MOSFET driver:

The MOSFET driver has been sized to be capable of driving power MOSFETs featuring a total gate charge up to

80nC.

Due to the continuous mode of operations of the inductor, the MOSFET must be driven with a reasonably (but not

excessively) low impedance, to minimize switching losses at both turn-on and turn-off without generating too

excessive EMI.

In term of Ron, the driver’s output devices are as follow: