VNH2SP30 H桥对电流控制的意外反应

对于我正在研究的项目，我必须能够切换珀耳帖元件（或其他器件）的极性，并能够线性控制通过珀耳帖的电流。

我不想在这个系统中使用普通继电器来做机械磨损，所以H桥是最好的选择。在阅读数据表后，VNH2SP30是我认为最好的选择。所以设计是基于这个H桥。


我用这个H-Bridge制作了原型PCB，并看到了对线性电流控制的意外反应。 （线性电流控制是一个OPAMP，基于MOSFET的电路，我之前已经使用了很多次，这个电路在PCB上作出预期的反应/工作）


当我启用INA时，启用PWM到DC值，所以假设PWM为100％并限制最大直流电流，让2Adc通过珀耳帖。根据我使用的电流限制设置，H桥的输出将以类似PWM的占空比脉冲。电流限制越高，PWM占空比越高。当电流达到可以通过珀耳帖（在15Vdc PSU）的最大值时，H桥的输出是稳定的100％''PWM''。


在阅读了数据表后，我的印象是可以在直流配置中使用这个H桥（带有0Hz的'PWM''）。所以我的问题是，输出上的PWM来自哪里？这是VNH2SP30的正常行为吗？

当电流限制设置为2A时，将拍摄下图中显示的信号




电路：



#h-bridge＃vnh2sp30



以下为原文




For a project I'm working on I have to be able to switch the polarity of a peltier element (or other device) and be able to linear control the current through the peltier.

I didn't want to put a normal relay in this system do to the mechanical wear, so a H-bridge was the best option. The VNH2SP30 was the best choise in my opinion after reading the datasheet. So the design was made based on this H-bridge.


I have made a prototype PCB with this H-Bridge and saw a unexpected reaction to the lineair current control. (The lineair current control is a OPAMP, MOSFET based circuit I have used many times before and this circuits reacts/works as expected on the PCB)


When I enable INA, enable the PWM to a DC value so lets say a PWM of 100% and limit the max dc current to lets say 2Adc through the peltier. The Output of the H-bridge will pulse in a PWM-like dutycycle based on the current limit setting I use. The higher the current limit the higher the PWM duty-cycle. When the current reaches maximum that is possible to go through the peltier (at a 15Vdc PSU) the output of the H-Bridge is a stable 100% ''PWM''.


After reading the datasheet I was under the impression that it was possible to use this H-Bridge in a DC configuration (with a 0Hz ''PWM''). So my question is, where does the PWM on the output come from? Is this normal behaviour for the VNH2SP30?  

The signals displayed in the images below are taken when the current limit was set to 2A




Circuit:


  
#h-bridge #vnh2sp30