Patent ID: 7514971
Filing Date: 2009-04-07
Classification: H05B

Abstract:
1. A triangle wave generator used in a pulse width modulation current adjustment apparatus, the triangle wave generator comprising: a first operational amplifier; a front resistor electrically connecting a negative terminal of the first operational amplifier to ground; a first feedback resistor, a second feedback resistor and a first current limiting resistor electrically connected to a positive terminal of the first operational amplifier so as to form a zero-crossing comparator; a second operational amplifier, a second current limiting resistor, a capacitor, and a back grounding resistor together forming an integrator; the back grounding resistor electrically connecting a positive terminal of the second operational amplifier to ground; and an output of the first operational amplifier electrically connected to the positive terminal of the first operational amplifier via the first current limiting resistor and the first feedback resistor, an output of the second operational amplifier electrically connected to the negative terminal of the second operational amplifier via the capacitor and also electrically connected to the positive terminal of the first operational amplifier via the second feedback resistor, and the output of the second operational amplifier outputting a triangle wave voltage signal; wherein the integrator comprising the back grounding resistor electrically connecting the positive terminal of the second operational amplifier to ground provides the triangle wave generator with the characteristic that the triangle wave voltage signal output by the second operational amplifier has a plurality of rising portions and a plurality of declining portions, with the triangle wave voltage signal consisting only of odd harmonics such that a percentage of high frequency harmonics of the triangle wave voltage signal is low.