Current sense

Note One should employ only current sensing relays as far as possible for such applications as a iiegatise sequence current has a severe effect on motor windings due to i much lower negative sequence impedance of the motor (.Section I2.2(v)i thtin a corresponding negative sequence voltage. 

The above bypass facility can also be achieved with the use of a thyristor switch, which may be made current sensing or voltage sensing. 

Instantaneous current sensing is used to proteet the power semieonduetors. A eurrent sensing resistor is plaeed in the power switeh eurrent path and its voltage represents the instantaneous eurrent flowing through the power deviee. This... 

Figure 3-50 Methods of constant current limiting (a) discrete overcurrent limiting (constant-current limiting) (b) precision resistive current-sensing overcurrent protection (constant-current limiting) (c) use of a current transformer to sense ac current.

Use the MTPIONIOM. I have selected the current sensing style of power MOSFET since I wish to implement a current-mode controller and this will reduce my sensing losses by three orders of magnitude. 

It is necessary to add a small leading edge spike filter to the current sensing output. To keep the time delay to a reasonable value, I will use a 1K ohm resistor and a 470 pF capacitor. 

Every current-mode control application that exceeds 50 percent duty cycle must have slope compensation on the current ramp waveform. Otherwise an instability will occur whenever the duty cycle exceeds 50 percent. This is typically done by summing into the current waveform some of the oscillator ramp waveform. This will increase the slope of the current waveform and therefore trip the current sense comparator earlier. A common problem is the inadvertent loading of the oscillator, so I will use a PNP emitter-follower to buffer the oscillator. The circuit configuration can be seen in Figure 3-74. 

The design of the slope compensation circuit is almost fairly qualitative and may eventually need to be adjusted at the breadboard stage. To estimate how much additional ramp voltage is needed to keep the power supply stable, one performs the following equation. Aj is the gain or step-down influences of the transformers between the output and the current sense pin. 

Current sense resistor (R15) and voltage sensing resistor divider (Rll and R13)... 

All current-carrying traces should be as wide and as short as possible. One-point grounding practices between the input, output, and low-level grounds should be done at the ground side of the current sense resistor. 

Yongyi Oh really I just changed a tiny ceramic capacitor—the one connected between the timing capacitor pin of the IC and the current sense pin. In fact I only reduced it from 47pF to 33pF Or maybe 22pF, I can t remember exactly, but a verrry minor change, sir. 

Fixed ramp added to switch current sense signal (crude but popular method of introducing slope compensation)... 

Figure 2-3 Kelvin Sensing for Better Current Sensing... 

What is not clock instability If, for example, you have a Buck with 100% duty cycle, you may find that under transient conditions, the switch will stay completely ON for several cycles. But that is normal. Similarly, on an IC with low-side current sensing, pulses may be omitted entirely under sudden transients. That too is normal. So don t forget to interpret the scope waveforms you see, with due regard to the part s architecture and the applied conditions, not just the topology. 

Visual detection of surface layers on cathodes using microscopy techniques such as SFM seems to be supportive of the existence of LiF as a particulate-type deposition.The current sensing atomic force microscope (CSAFM) technique was used by McLarnon and co-workers to observe the thin-film spinel cathode surface, and a thin, electronically insulating surface layer was detected when the electrode was exposed to either DMC or the mixture FC/DMC. The experiments were carried out at an elevated temperature (70 °C) to simulate the poor storage performance of manganese spinel-based cathodes, and degradation of the cathode in the form of disproportionation and Mn + dissolution was ob-served. °° This confirms the previous report by Taras-con and co-workers that the Mn + dissolution is acid-induced and the electrolyte solute (LiPFe) is mainly responsible. 

Scanned probe microscopies (SPM) that are capable of measuring either current or electrical potential are promising for in situ characterization of nanoscale energy storage cells. Mass transfer, electrical conductivity, and the electrochemical activity of anode and cathode materials can be directly quantified by these techniques. Two examples of this class of SPM are scanning electrochemical microscopy (SECM) and current-sensing atomic force microscopy (CAFM), both of which are commercially available. 

Numerous approaches have been proposed for use in CMP for in situ EPD. They include optical, electrical, and acoustic sensing. Given the benefits of EPD, it is no surprise that many of these methods have been awarded patents. Some of these methods, most notably current sensing, have been developed to become commercially viable products while others remain laboratory curiosities. For a review of in situ endpoint detection methods up to early 1998, see the work of Bibby and Holland [68]. 

Lee HJ, Lee J, Park S-M (2010) Electrochemistry of conductive polymers. 45. Nanoscale conductivity of PEDOT and PEDOT PSS composite films studied by current-sensing AFM. J Phys Chem B 114 2660... 

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