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Circuit for improving linearity of output current control

A technology of output current and linearity, applied in the direction of electrical digital data processing, special data processing applications, instruments, etc., can solve problems such as the decrease of constant current accuracy and the deterioration of regulator stability

Inactive Publication Date: 2018-11-06
南京博德新能源技术有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] UC3842 generally adopts constant frequency control. In applications that require a small constant current output, such as LED dimming, UC3842 needs to reduce the pulse width; when the pulse width drops below 0.1, the stability of the regulator becomes worse, and the constant current The accuracy drops

Method used

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  • Circuit for improving linearity of output current control
  • Circuit for improving linearity of output current control
  • Circuit for improving linearity of output current control

Examples

Experimental program
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Effect test

Embodiment 1

[0024] image 3 It is the current control circuit used to control the chip L6562 of the first embodiment.

[0025] Assume that pin 1 INV of the L6562 is connected to a 10K resistor to the ground, and a 10K resistor is connected between pin 1 INV and pin 2 COMP of the L6562, then due to the voltage characteristics of the op amp, VCOMP=5V; and further assume that VMULT works between 0V and 0.8V linear region.

[0026] The current reference signal VIref enters the non-inverting terminal of the operational amplifier U2A through the resistor R5, and the current feedback signal VIf enters the inverting terminal of the operational amplifier U2A through the resistor R4. The capacitor C2 and the resistor R6 form a compensation network. The current feedback signal and the current reference signal The error adjustment signal after the difference value passes through the regulator is output by pin 1 of the operational amplifier U2A, and the primary side current is generated in the diode ...

Embodiment 2

[0030] Assume that pin 1 INV of the L6562 is connected to a 10K resistor to the ground, and a 10K resistor is connected between pin 1 INV and pin 2 COMP of the L6562, then due to the voltage characteristics of the op amp, VCOMP=5V; and further assume that VMULT works between 0V and 0.8V linear region.

[0031] The main power topology chooses the BUCK converter. The circuit characteristic of BUCK is that the average value of the inductor current is equal to the output current. L6562 works in the critical continuous state of the inductor current, and the average value of the inductor current is half of the peak value of the inductor current. The peak value of the current is equal to the peak value of the inductor current. The switching current of the switching tube enters the 4th pin of the L6562, namely Vcs, after passing through the detection circuit; the setting of VCOMP makes the relationship between VMULT and Vcs in the linear region, and finally it can be obtained that the ...

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Abstract

The invention discloses a circuit for improving the linearity of output current control. According to the circuit, a multiplying unit integrated inside a PFC control chip is utilized to perform outputcurrent control, two input ends of the multiplying unit integrated inside the PFC control chip are a COM pin and an MULT pin respectively, and by fixing the voltage of the COM pin and controlling thevoltage of the MULT pin, linear regulation of an output current is realized, wherein the specific regulation scheme can be closed-loop regulation or open-loop regulation.

Description

technical field [0001] The invention relates to a circuit for improving the linearity of output current control, in particular to a circuit for controlling output current by using a multiplier integrated in a PFC control chip. Background technique [0002] The voltage-controlled switching power supply has difficulty in overcurrent protection, slow response, and poor stability. Compared with it, the current-controlled switching power supply is a voltage and current double closed-loop control system, which can overcome the shortcomings of current runaway, and has reliable performance and simple circuit. [0003] UC3842 is a full-featured, relatively typical single-ended current-mode PWM control integrated circuit, which includes error amplifier, current measurement comparator, PWM latch, oscillator, internal reference power supply and undervoltage lockout and other units. [0004] The functions of several main pins of UC3842 are as follows: Pin 1 is the output terminal of the ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/50
CPCG06F30/327
Inventor 张从峰杨宏
Owner 南京博德新能源技术有限公司