Soft-start control for a push-pull converter-regulator with a flux balancing circuit

Claim 2

In a converter controlled in response to a pulse width modulated waveform to provide a DC output, the converter having an error detecting means for comparing the output of the converter to a reference signal to vary the duty cycle of the pulse width modulated (PWM) waveform, improved means for controlling the start-up of said converter to limit inrush currents, comprising: means for signaling the start-up of the converter; and means for providing a varying reference signal to said error detecting means, said reference signal gradually incresing from zero to a predetermined level so that the duty cycle of the PWM waveform gradually increases following the signaled start-up of said converter.

Claim 3

In a converter controlled in response to a pulse width modulated waveform to provide a DC output, the converter having an error detecting means for comparing the output of the converter to a reference signal to vary the duty cycle of the pulse width modulated waveform, improved means for controlling the start-up of said converter, comprising: means for signaling the start-up of the converter; and means for providing a varying reference signal to said error detecting means, said reference signal gradually incresing from zero to a predetermined level in response to the signaled start-up of said converter wherein said reference signal providing means includes a capacitor and a constant current source for charging said capacitor.

Claim 4

In a converter controlled in response to a pulse width modulated waveform to provide a DC output, the converter having an error detecting means for comparing the output of the converter to a reference signal to vary the duty cycle of the pulse width modulated waveform, improved means for controlling the start-up of said converter, comprising: means for signaling the start-up of the converter; and means for providing a varying reference signal to said error detecting means, said reference signal gradually incresing from zero to a predetermined level in response to the signaled start-up of said converter wherein said reference signal providing means includes a capacitor and a constant current source for charging said capacitor.

Claim 5

The converter of claim 2 wherein the reference signal providing means further includes a zener diode connected in parallel with said capacitor to limit the voltage across the capacitor to said predetermined level.

Claim 6

The converter of claim 2 wherein the means for signaling the start-up of the converter includes a normally closed switch coupled across the capacitor, said switch being opened when power to the converter is turned on.

Claim 7

In a converter having a DC source, a pair of power switches, an output transformer and a pulse width modulation control for alternately closing the power switches to connect the DC source with said output transformer to produce a regulated output and having an error detecting means for comparing the output of the converter to a reference signal to provide an error signal to said pulse width modulation control, improved means for controlling the start-up of said converter comprising: means for signaling the start-up of the converter; means for providing a varying reference signal to said error detecting means, said reference signal gradually increasing from zero to a predetermined level in response to the signaled start-up of the converter; and flux balance control means for sensing an imbalance in the currents flowing through the power switches to provide a correction signal for modifying the error signal output from said error detecting means.

Claim 8

In a converter having a DC source, a pair of power switches, an output transformer and a pulse width modulation control for alternately closing the power switches to connect the DC source with said output transformer to produce a regulated output and having an error detecting means for comparing the output of the converter to a reference signal to provide an error signal to said pulse width modulation control, improved means for controlling the start-up of said converter comprising: means for signaling the start-up of the converter; means for providing a varying reference signal to said error detecting means, said reference signal gradually increasing from zero to a predetermined level in response to the signaled start-up of the converter; and flux balance control means for sensing an imbalance in the currents flowing through the power switches to provide a correction signal for modifying the error signal output from said error detecting means.

Claim 9

The converter of claim 5 wherein said means for providing said reference signal includes a capacitor and a zener diode connected in parallel and a constant current source for charging the capacitor to a level determined by said diode.