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DC-DC LED driving circuit based on PWM dimming

A driving circuit and dimming technology, applied in the direction of light source, electric light source, electrical components, etc., can solve problems such as LED damage, capacitor noise, etc., achieve good linearity, eliminate overshoot current, and fast settling speed

Pending Publication Date: 2017-09-19
上海灿瑞微电子有限公司 +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

On the one hand, the LED current overshoot may cause damage to the LED, and on the other hand, the capacitor may generate noise

Method used

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  • DC-DC LED driving circuit based on PWM dimming
  • DC-DC LED driving circuit based on PWM dimming
  • DC-DC LED driving circuit based on PWM dimming

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Embodiment Construction

[0037] The above and / or additional aspects and advantages of the present invention will become apparent and comprehensible from the following description of the embodiments in conjunction with the accompanying drawings.

[0038] image 3 It shows a BUCK type DC-DC LED drive circuit based on PWM dimming in the present invention, including LED load 101, DC-DC conversion circuit 102, logic circuit 103, error amplifier 105, compensation circuit 106, and duty cycle signal generation circuit 107 and the current sampling resistor Rcs. Each component in this embodiment is described in detail below:

[0039] The compensation circuit 106 is the core of the present invention, which includes: a frequency compensation resistor R1, one end of which is connected to the duty cycle signal generating circuit 107; a first switching tube M1, whose gate is connected to a PWM dimming signal end to receive a PWM For the dimming signal, the drain is connected to the output terminal of the error amp...

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PUM

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Abstract

The present invention provides a DC-DC LED driving circuit based on PWM dimming. The circuit comprises a DC-DC conversion circuit, a logic circuit, an error amplifier, a compensation circuit, a duty ratio signal generating circuit and a current sampling resistor. The compensation circuit comprises a frequency compensation resistor, a first switch tube, a second switch tube, a first frequency compensation capacitor, a second frequency compensation capacitor, and a third switch tube, wherein the gate of the first switch tube is connected to a PWM dimming signal end, the drain electrode of the first switch tube is connected to the error amplifier, the source electrode of the first switch tube is connected to the duty ratio signal generating circuit, the gate of the second switch tube is connected to the PWM dimming signal end, the drain electrode of the second switch tube is connected to the frequency compensation resistor, the positive electrode end of the first frequency compensation capacitor is connected to the source electrode of the second switch tube, the positive electrode end of the second frequency compensation capacitor is connected to the drain electrode of the second switch tube, the drain electrode of the third switch tube is connected to the source electrode of the second switch tube, and the gate of the third switch tube is connected to the PWM dimming signal end through an inverter. According to the DC-DC LED driving circuit, a series of problems that a long soft start time affects a minimum dimming frequency and PWM dimming linearity in a small duty ratio and LED current overshoot brings lamp damage and capacitance noise in PWM dimming are avoided.

Description

technical field [0001] The invention relates to a DC-DC LED driving circuit, in particular to a DC-DC LED driving circuit based on PWM dimming. Background technique [0002] DC-DC LED drive circuits are widely used in LCD TVs, portable electronic devices and lighting, etc. PWM dimming technology is commonly used in LED drive circuits to change the brightness of LEDs. Good dimming includes characteristics such as good linearity and no noise from electronic components. [0003] The DC-DC LED drive circuit generally adopts a closed-loop control method to achieve precise control of the LED current, and often adds a soft-start method to smooth the start-up process and avoid damage to the LED due to overshoot current. Soft start is generally realized by using the low bandwidth of its own loop or controlling the slow rise of the reference voltage. The time of soft start is often relatively long, generally at the millisecond level. When dimming with PWM signal, longer soft-start ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H05B33/08H05B44/00
CPCH05B45/10Y02B20/30
Inventor 不公告发明人
Owner 上海灿瑞微电子有限公司
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