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Self-oscillating control circuit voltage converter

A technology for voltage converters and control circuits, applied in control/regulation systems, output power conversion devices, instruments, etc., can solve problems such as increased cost, low cost, and converter damage

Inactive Publication Date: 2006-05-24
STMICROELECTRONICS SRL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This significantly increases the cost and is also the shortcoming that this type of converter is often damaged
[0013] Therefore, converters with self-oscillating control circuits are conventionally not capable of matching the output voltage V OUT Compatible with regulation, while maintaining the advantage of low cost

Method used

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  • Self-oscillating control circuit voltage converter

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Embodiment Construction

[0032] In different figures, the same elements are indicated by the same symbols. The time graph of Figure 5 is not scaled. For the sake of clarity, only the elements of the voltage converter that are useful for understanding the invention are shown in the figures and will be described next. In particular, the structures of the fixed reference voltage generator circuit, driver, comparator and oscillator are not described in detail, nor are they the object of the present invention.

[0033] A feature of the invention is to use the image of the voltage on the secondary winding providing the output voltage to modulate the reference voltage of the comparator to determine the duration of the ON state of the regulation switch. In other words, the reference voltage used to turn on the supply voltage switch is allowed to vary and this variation is made a function of the output voltage. In order to achieve the regulation of the output voltage.

[0034] To provide protection against co...

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PUM

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Abstract

A voltage converter with a self-oscillating control circuit that allows regulation of the output voltage without the need for galvanic isolation elements between the transformer secondary winding and the control circuit. the voltage converter having a primary winding (5) in series with a switch (6) for leveling the supply voltage and a transformer (4) with a secondary winding (7) connected to a capacitor (C2) to provide a low DC voltage; and A self-oscillating control circuit (30) for controlling the switch, the control circuit comprising: a device (17) for detecting the completion of demagnetization of the transformer auxiliary winding (8) to close the switch; for detecting the current in the on state of the switch, when means for opening the switch when the current reaches a set point; and means (20) for varying the set point in response to the voltage across the terminals of the auxiliary winding. The invention achieves output voltage regulation according to desired rated voltage and continuous current overload protection while maintaining the operation of the self-oscillating control circuit of the voltage converter.

Description

technical field [0001] The invention relates to the field of low voltage switch mode power supply type voltage converters. The present invention more particularly relates to isolated power supplies, ie power supplies having no common point between an input voltage (such as an AC power supply system) and a regulated DC output voltage. Isolation is achieved with a transformer having a primary winding connected to a switch and a secondary winding connected to a diode and a capacitor providing the output voltage. The invention more particularly relates to so-called self-oscillating converters in which the switches are controlled by frequency modulation, as opposed to conventional converters in which the switches are controlled by pulse width modulation. Background technique [0002] Figure 1 shows an example of a conventional switch mode type power supply to which the invention is applicable. Two input terminals P, N receive AC voltage V ac , such as mains voltage. Voltage V...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M3/338
CPCH02M3/3385
Inventor 伊果·宾保德
Owner STMICROELECTRONICS SRL