Primary-side regulated pulse width modulation controller with improved load regulation

A controller and primary-end technology, applied in the direction of adjusting electrical variables, control/regulation systems, and conversion equipment with intermediate conversion to AC, etc., can solve the problem that the feedback signal cannot accurately follow the transformer voltage, the relationship is weakened, and the load regulation is insufficient and other issues, to achieve the effects of reducing production costs, improving accuracy, and improving voltage regulation

CN1806380AActive Publication Date: 2006-07-19SYST GEN
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2006-07-19

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Abstract

The present invention provides a primary-side regulated PWM (pulse width modulation, pulse width modulation) controller with improved load regulation. In each PWM cycle, a built-in feedback voltage generator samples and holds the flyback voltage from the auxiliary winding of the transformer through a sampling switch, and generates a feedback voltage accordingly. A bias current sink sinks a bias current proportional to the feedback voltage. When the output load changes, the bias current will generate a voltage drop through a sense resistor to compensate the voltage drop of the output rectifier diode. According to the present invention, the bias current may enable the PWM controller to regulate the output voltage very accurately without using a secondary feedback circuit.
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Description

technical field

[0001] The present invention relates to a switching power supply, and more particularly, the present invention relates to a primary-side regulated pulse width modulation (PWM) controller of a switching power supply. Background technique

[0002] Usually we use switching power supply (SMPS) as the primary power supply for computers, communication devices and many other products. SMPSs have many advantages in design over other types of power supplies, including more efficient power conversion, smaller size, and lighter weight. However, the high component count in SMPS designs remains a problem for power supply manufacturers and engineers. In order to reduce the production cost of the power supply, some solutions without secondary-side feedback control are provided in the prior art. The applicant of the present invention filed a corresponding patent application in the United States entitled "PWM controller regulating output voltage and output current in primar...

Examples

Embodiment Construction

[0020] image 3 A flyback power supply using a primary side regulated PWM controller 101 according to the present invention is shown. V 1 is the flyback voltage of the auxiliary winding of the transformer 400 . V 2 is the flyback voltage of the secondary winding of the transformer 400 . When the PWM controller 101 is running, the auxiliary winding supplies the power supply voltage Vcc through the rectifier diode D1. Auxiliary winding flyback voltage V 1 Can be expressed as:

[0021] N 1 = N A dφ dt - - - ( 1 )

[0022] Among them, N A is the number of turns of the auxiliary winding, and φ is the magnetic flux of the transformer 400 .

[0023] secondary winding flyback voltage V 2 Can be expressed as:

[0024] V 2 = ...