Low power dc-dc converter
OwnerBrian E. Attwoodinventor
Life of this patent
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Abstract
The converter is a switch mode converter in which a primary transformer winding (12) is switched by a power switch (Q5). The transformer secondary is wound with a power output winding (14) and a reference winding (29). The power switch (Q5) is operated by IC (24) connected as a ring-of-three oscillator. Regulation is achieved by two feedback means. First, the voltage on the reference winding (29) is peak rectified and fed back (30) to control the oscillator (24). Secondly, a signal which is a function of the on-time of the power switch (Q5) modifies the operation of a reference voltage source (Q1, Q2). The converter is particularly adapted to operate over a wide range of input voltages (typically 24 V-60 V) and over a wide range of low power (typically 24 mW-850 mW).
Claims11
A dc-dc converter comprising:
- an input for receiving an input voltage;
- a transformer having primary and secondary windings and producing a secondary side voltage;
- switching means operative to switch the input voltage across the transformer primary winding;
- oscillator means connected to the switching means to cause the switching means to operate repetitively;
- an output coupled to the transformer secondary winding via a low-pass filter;
- a control circuit for controlling the operation of the oscillator means to regulate an output voltage;
- a primary-side voltage reference source;
- and
- feedback means generating a feedback signal which varies with at least one parameter of the secondary side voltage;
- and in which the feedback means is operative to provide a feedback signal representative of the output voltage and an on-time of the switching means;
- and
- the converter further includes means for providing to the primary-side voltage reference source a variable dc offset which varies with the on time of the switching means to modify the output of the primary-side voltage reference source.
Dependencies are inferred from the claim text.