MOSFET Pass Element Yields 100

In terms of low RON, the best pass transistor for a low-dropout, posiTIve-voltage regulator is an N-channel MOSFET. All such commercially available regulators, however, use bipolar PNP pass transistors. The PNP transistor can saturate completely in these applicaTIons because the base voltage is lower than the output voltage, producing a collector-emitter voltage of less than 0.4V. For comparison, the corresponding drop across an NPN pass transistor is greater than VBE (SAT) (1.2V minimum) because regulator circuits generally provide no base-drive voltage higher than the input (VCC).

N-channel MOSFETs provide the lowest VDROP = IOUT × RON, but the required VGS drive varies with output current and ranges 3 to 4 volts above the output voltage. In Figure 1, the circuit provides this drive voltage by employing a voltage converter chip ( IC1) that uses charge-pump techniques to boost a 5V input to 10V. The 10V output then drives a posiTIve-voltage regulator (IC2), which in turn drives the N-channel, Logic-level MOSFET Q1. The gate drive available to Q1 remains high (10V) because the low supply current into IC2 (10µA) produces a small IR drop through IC1 (approximately 1.5mV), which enables IC1's output to remain nearly twice the value of VCC.

During the operaTIon at 500mA, the dropout voltage—the minimum value of VCC-VOUT that sustains regulation—is only 100mV. The quiescent current is only 1mA, thanks to the CMOS technology of IC1 and IC2. Resistor R3 prevents the MOSFET gate from floating when the regulator is OFF, and the feedback resistors R1 and R2 set the regulator's output voltage VOUT:

Equation 1

IC2 also incorporates a low-battery detector whose output (LOB) goes low when the detector's input voltage (connected LBI) goes below 1.3V. As shown, the circuit detects VCC overvoltage. LBO remains low for normal-range VCC levels and goes high when VCC exceeds it's upper limit (6.3V in this case). IC2 shuts down when LBO pulls the SHDN input high, thereby preventing excessive dissipation in the pass transistor by removing it's gate drive. R7 protects IC1 by restricting it's current flow.

You can also use the detector to sense complete saturation in Q1 (the condition in which VCC is less than VOUT plus 100mV). Connect SHDN to ground. (Or, you can turn the output off and on by driving SHDN with a CMOS gate. ) Set the R5–R6 divider to produce 1.3V when VCC = VOUT + 100mV, and then monitor LBO for the low (fault) condition.

Figure 1

Electric Tea Kettle:

 

Quickly brew the perfect cup of tea or make pour over coffee right at the table with the Electric Tea Kettle. With 1500 watts, this Electric Kettle boils water faster than a microwave, and is safer to use than a stovetop kettle because it automatically turns off when the water reaches a boil. Serving at the table is no problem as the kettle lifts off the base without the cord. Additional features include two water level windows and a pull-lid to make filling and serving easy. 

 

Features:

  •  Thermostat Control – Having a thermostat control allows the kettle to [know" when to shut off. This will prevent damage to the heating element and is an important feature in all modern styles.
  •   Auto shut off/Boil Dry Protection/Fuse â€“ these are three features that are great for protecting the safety of users as well as extending the life of the electric kettle.  The fuse and boil dry protection shut the kettle off if the water gets down below a certain level or if it`s left on for an extended period of time, It doesn`t burn up the kettle.
  • Colors and Designs â€“ Electric kettles come in all shapes, sizes and colors. Finding one that will fit with the kitchen design is actually pretty easy.  Finding one that matches and that has the features you`re looking for can be a bit harder, but with all the choices available and the newer models on the market today, you will be able to find the perfect electric kettle for your kitchen.
  • Savety in Electric- the heating element is typically fully enclosed, with a power rating of 2–3 kW at 220V. In countries with 110V mains electricity, kettles may be less powerful (1–1.5 kW) to avoid drawing too much current and requiring a very thick supply wire.

Application:

Heat the tea thoroughly

Bottle the water/beer

Boil water

Electric Tea Kettle

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