Primary constant-current control device of isolated type flyback converter
A technology of flyback converter and constant current control, which is applied in the direction of output power conversion device, lighting device, DC power input conversion to DC power output, etc. It can solve the problems of large electromagnetic interference, large dv/dt, etc., and reduce the Effects of electromagnetic interference, circuit reliability, and component count reduction
Active Publication Date: 2013-06-05
盐城市盐南高新区都市产业发展有限公司
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[0014] Another disadvantage of the hard turn-on of the switch tube at a higher voltage between the drain and the source (or collector-emitter) is that the switch tube will generate a larger dv / dt at the moment of conduction, which will generate a larger electromagnetic interference
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[0046] The content of the present invention will be described in detail below in conjunction with specific embodiments and accompanying drawings.
[0047] refer to Figure 5 , the primary side constant current control device of the isolated flyback converter mainly includes a peak sampling and holding module 21, a secondary side current simulation module 22, an average current loop 23, a comparison module 24, an inductor current zero-crossing detection module 25, and a driving pulse generation module 26 and drive module 27.
[0048] The present invention forms a switching power supply together with the main circuit of the flyback converter, wherein the main circuit of the flyback converter includes an input DC power supply V in , transformer T, absorption network, primary side switch tube Q 1 , primary current sampling network, output rectifier (choose rectifier diode D 1 ) and the output capacitor C o .
[0049] The peak sampling and holding module 21 is connected to the...
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The invention discloses a primary constant-current control device of an isolated type flyback converter, which comprises a peak sampling and holding module, a secondary current analog module, an average current ring, a comparison module, an inductive current zero passage detection module, a drive pulse generation module and a driving module. The output end of the peak sampling and holding module is connected with the input end of the secondary current analog module, and the output end of the secondary current analog module is connected with the input end of the average current ring; the output end of the average current ring is connected with one input end of the comparison module, the output end of the compassion module is connected with one input end of the drive pulse generation module, the inductive current zero passage detection module is connected with the other input end of the drive pulse generation module, and the output end of the drive pulse generation module is connected with the driving module. The device does not uses optocoupling elements and transformer secondary control circuits any more, has simple circuit structure, not only can realize the quasi-resonant control of the flyback converter, but also can output constant current very well.
Description
technical field [0001] The invention belongs to the technical field of switching power supplies, and relates to a primary side constant current control device of an isolated flyback converter. Background technique [0002] The light characteristics of LEDs are usually described as a function of current rather than voltage. A small change in the forward voltage drop of an LED will cause a large change in the LED current, thereby causing a large change in brightness. Therefore, using a constant voltage source to drive cannot guarantee the consistency of the LED brightness, and affects the reliability, life and light decay of the LED. Therefore, LEDs are usually driven by a constant current source. In addition, some civilian products such as mobile phone chargers must also have a constant current output function [0003] Flyback converters are widely used in low-power LED drivers and mobile phone chargers due to their low cost. The traditional single-transistor flyback conve...
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IPC IPC(8): H05B37/02H02M3/335
CPCY02B70/1433Y02B70/10
Inventor 谢小高
Owner 盐城市盐南高新区都市产业发展有限公司