Constant current control circuit

Abstract

A constant-current control circuit comprises a full bridge rectifier, a transformer, a fly-wheel diode and a power switch tube. The direct-current forward direction output end of the full bridge rectifier is connected with a primary side forward direction end of the transformer. The primary side reverse direction end of the transformer is connected with the drain electrode of the power switch tube. The alternating current forward direction input end of the full bridge rectifier is connected with the high-voltage power end of a high-voltage power supply branch circuit. The high-voltage power supply branch circuit comprises a high-voltage NMOS tube and a medium-voltage NMOS tube, wherein the high-voltage NMOS tube and the medium-voltage NMOS tube are connected with each other in series and are respectively connected between a high-voltage power end and a secondary high-voltage end and between the secondary high-voltage power end and a low-voltage power end. The high-voltage power supply branch circuit further comprises a charge pump, a starting charging circuit, a low-voltage comparator, a secondary high-voltage comparator and a charging logic circuit. The constant-current control circuit realizes charging management of a VDD only through time division multiplex access of a single high-voltage NM1tube, and other control circuits are all low-medium voltage elements, so that the layout area of a chip is greatly reduced.

Description

technical field [0001] The invention belongs to the field of integrated circuits and relates to a constant current control circuit. Background technique [0002] With the improvement of the efficiency of the power management chip, the reduction of the volume and the reduction of the cost, the power management chip is also more and more widely used in the AC-DC (alternating current to direct current) power management module. All kinds of white goods, chargers, and LED (Light Emitting Diode) lighting equipment that come into contact with in daily life need AC-DC power management modules to realize AC-DC conversion. [0003] In the AC-DC power management module, chips such as flyback, non-isolated step-down or resonant control are usually used to realize AC-DC conversion. The traditional power supply methods of these chips are as follows: figure 1 Shown (take the flyback control chip as an example). The application circuit includes diode rectifiers D0~D3, input capacitor Cin...

AI Technical Summary

Problems solved by technology

[0005] Aiming at the problems existing in existing chip working power supply technology that direct power supply from high-voltage Vin will cause large losses and is only suitable for applications with low chip working current, and that power supply from auxiliary windings causes complex system design and increased cost, the present invention provides a constant current control circuit

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