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Voltage-to-pulse-duration converter

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Hello everybody,

I read an article in Philips application note (AN170, Dec. 1988) about an application to convert voltage to pulse duration - PWM.

I tried the circuit with a simulator programme with the only difference using 2N2222 instead of a 2N3642. No matter which input voltage is applied or offset adjustments are done the timer output is constantly high.

The simulation programme is very old and maybe some features of the NE555 are not implied.

Has somebody made any experience concerning voltage to pulse duration? If Yes please notify me.

Thank you

Herman the German

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Yes... we (where I work) have a flyback DC-DC converter (voltage mode) design that uses a 556. It's configured like Fig 6 in that app's note and the feedback is fed into the control pin. The only problem is that the frequency isn't constant. We use the other half of the 556 as a one-shot for the current limit hic-up time-out. You could do this with just about any voltage mode PWM.

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