led-driver-dat

https://w.electrodragon.com/w/LED_Drive

boards

tech

Common questions

This is a buck (step-down) constant-current LED driver. Input: 5–32 V.

  • The input voltage must be at least 1 V higher than the LED string voltage required. This is a constant-current driver, not a constant-voltage regulator.
  • People often ask "what is the output voltage?" — the board controls current, not voltage. The output voltage will adjust to whatever the LEDs require.
    • Example: if one LED requires ~3 V, the LED voltage stays ~3 V. Two in series ~6 V, etc.
    • Do not measure output voltage with no load. No-load output reads the input voltage (a phantom voltage).
  • This is a step-down (buck) constant-current driver, not a boost driver.
    • If two LEDs in series require 6 V to light, and you supply 5 V, they will not light. You must supply at least ~7 V (6 V + ~1 V headroom).
  • Output current formula: I = 0.1 / R_CS (R_CS = current sense resistor).

driver options

integrated chip solutions

mosfet control options

The FQP30N06L MOSFET (datasheet) is an N-channel MOSFET designed for switching high-speed circuits, and it’s perfect for switching LEDs. It can control up to a 60V, 30A load and can be switched from 3.3V or 5V.

https://cdn.sparkfun.com/datasheets/Components/General/FQP30N06L.pdf

mosfet PWM control

futher concern

high speed switching

LCD backlight drive

option 1

chip

option 3

背光驱动

该部分用于驱动RGB屏幕背光，标准40Pin RGB屏幕基本采用串联背光，由于本身开发板供电只有5V，所以我们需要使用背光驱动芯片升压到合适的电压，来驱动屏幕背光。同时，背光驱动芯片采用恒流控制，可以避免电流过大导致背光LED烧毁，该部分原理图如下所示：

其中：

C19 C20为滤波电容，C19电容的耐压需要特别考虑，一般的RGB屏背光电压基本在18V以上(白光LED压降3V*6串)，过低的电容耐压会导致电容损坏。

BL_CTR为芯片背光控制引脚，此处直接接入了上拉，再开发时可以将BL_CTR引脚接入F1C200S的PWM引脚上，这样可以灵活控制屏幕亮度，同时，有恒流驱动的存在，控制亮度时，背光也不存在明显的频闪。

L1 为升压电路的电感，按照要求一般取10uh或22uh即可，不需要使用公式详细计算，但是需要注意电流不能超过电感额定电流。

R5为芯片的反馈电阻，用于调节输出的电流，计算公式可参考下方：

图2.13反馈电阻计算公式

此处我们选择20ma，所以R1=0.25/0.020（Ω） = 12.5Ω，就近取12Ω。

选择的20ma电流可以参考屏幕数据手册：

图2.14 屏幕数据手册线路原理图

如上图，下方说明了LED为2并5串，额定电流为40ma，我们为了保险，选择了20ma，亮度会有所损失。

12V button-MCU-transistor driver

button buttons on the back side, low-side control white and warm white LED strips

driver AOA3 ?

unsort

  • MIC2871YMK-T5 - LED Driver IC 1 Output DC DC Regulator Step-Up (Boost) Single-Wire Dimming 1.2A (Flash) 14-LDFN (3x2)

driving method

Current Push vs Pull: Power Supply & LED

1️⃣ Conceptual difference

Term Meaning Direction of Current Notes
Current Push Source actively drives current into a load From power supply → load Standard operation of most DC power supplies: source “pushes” electrons into the device.
Current Pull Load draws current from the source From load → source Seen when load is voltage-controlled, like LEDs with a series resistor on a constant voltage supply.

In practice:

  • Power supply: pushes current.
  • LED: draws (pulls) current according to its forward voltage and series resistor/driver.

2️⃣ Relation to LEDs

  • LED is a current-driven device:

    • Brightness is determined by current, not voltage.
    • Excess current → LED damage.

  • Power supply types:

    1. Constant Voltage (CV, e.g., 12V)
      • Supply pushes voltage → LED pulls current through series resistor.
      • Resistor needed to limit current.
    2. Constant Current (CC, e.g., 350mA)
      • Supply pushes fixed current → LED sets voltage automatically.
      • Stable brightness, no extra resistor needed.

3️⃣ Practical Examples

12V LED with resistor:

12V (push) → resistor → LED (pull)

  • Power supply pushes 12V.
  • LED pulls current: I = (12V - Vf) / R
  • If R too small → LED pulls too much → burns out.

Constant current driver:

12V CC driver (pushes 350mA) → LED (accepts 350mA)

  • Driver maintains current automatically.
  • LED adjusts voltage accordingly.
  • No resistor needed.

4️⃣ Key Takeaways

  1. LEDs are current-driven; control current rather than voltage.
  2. Push vs Pull is perspective: supply pushes, LED pulls.
  3. Use constant current drivers to protect LEDs.
  4. With voltage supply, always use a series resistor to limit current.

ref

Table of Contents

https://www.electrodragon.com