TPS92513: tps92513pwm调光有问题

Hi Customer,

Could you please provide the spec (forward voltage and forward current) of your LED?

Best Regards,

Steven

led的电压为24v，电流为8ma

Hi Customer,

Could you please double-check if the LED forward voltage is 24V? I see the input voltage is 24V in the schematic you provide.

Best Regards,

Steven

是的，正向电压是24v，这有什么问题吗？只要能让led发亮就行了吧，输出比24v低一点也没事

Hi Customer,

Please make sure the input voltage is higher than the LED forward voltage in such a Buck LED driver.

Please increase the input voltage and have another try.

Best Regards,

Steven

我们增加了输入电压还是一样的情况；我想问一下用pwm调光是否能让tps92513输出0~24v；因为我现在的现象是pwm可调光，但是输出范围是19~24v；无法关闭led灯；测量过pwm波形，从0%~100%占空比没有问题

我们还买了你们的TPS92513EVM-001模块，但是用我们板子上的STM32F401RET6给到公板的pwm信号，出现了跟我们板子一样的现象；pwm频率为1khz，当pwm拉高后再拉低，发现输出端还是有电压，led灯处于微亮，也用示波器测量过pwm波形，没有发现异常

Hi Customer,

TPS92513 cannot work with Vin = 24V and Vout = 24V (the switching duty cycle cannot be always 100%) since you need some switching-off time to charge the BOOT capacitor.

I will check if I can reproduce on our EVM the condition you observed when Vin was increased and will feedback to you later.

Best Regards,

Steven

好的，我们没有总是在占空比100%时工作，更多的是50%左右

Hi Customer,

Understood. I will do the bench test and feedback to you later.

Best Regards,

Steven

有结果了？

Hi Customer,

I tried to reproduce the situation you observed on our EVM but failed. Have you measured the leakage current on the LED when PDIM turns low from PWM input?

Best Regards,

Steven

当pwm为90%占空比时我们量过电流为8ma，但是当pwm占空比降低到0%时，电流为0ma；但是此时电压却依然有8.5v；你们也是用pwm为0%时去关闭输出的嘛；你们的led参数能提供一下嘛

我们是12v输入，然后用STM32F401RET6去发出pwm信号

Hi Customer,

Sorry. I am currently out of office. I will reply to you this Friday when I am back to office. Thanks for your understanding.

Best Regards,

Steven

Hi Customer,

Sorry for the late response.

Yes. We are using PWM duty cycle = 0% at PDIM pin to turn off the current output. The LEDs we use in the test are KW CSLPM1.TG-8N7P-EBVF46FCBB46-15B5-S from ams OSRAM.

Best Regards,

Steven

你好，你们测试时候的pwm波形图能发出来给我们参考一下嘛，还有你们是用什么芯片去产生pwm波形的？

Hi Customer,

We are using a signal generator to generate the PWM signal. The signal is a square wave with high level = 3.3V and low level = 0V. The frequency is set to 1kHz.

Best Regards,

Steven