# Tag Info

18

The entire half-bridge configuration is not called a synchronous rectifier- the low-side MOSFET (which replaces a diode) is the synchronous rectifier. The gate of that MOSFET must be driven synchronously for it to work. There are other kinds of synchronous rectifiers, for example this full-wave mechanical synchronous rectifier (home-built at a time when high-...

7

First off, I am not aware that half-bridge circuits are always called synchronous rectifiers. The way I understand it, synchronous rectifiers replace the traditional diodes in a half-wave or full wave bridge configuration with transistors (usually MOSFETs nowadays). These transistors are turned on and off synchronously with respect to the incoming AC or ...

6

A CC-CV control is a classic in battery management systems. Basically, you have two loops: a voltage loop for constant-voltage operation (CV) which observes the output voltage and maintains it to the regulated level by generating a frequency-compensated error voltage. a current loop for constant-current operation (CC) which senses the output current - ...

5

Does connecting the boost converter outputs to linear regulators make any technical sense, or there are better solutions to the problem? Yes, but. Typically linear regulators have good PSRR at low frequency ; if you still want good PSRR upwards of a few kHz you have to do your shopping more carefully, some are really bad and some are quite good. You will ...

3

Beside impacting the physical dimensions of the converter, increasing the switching frequency offers the ability to push the crossover frequency higher. In theory, the crossover frequency $f_c$ is limited to half of the switching frequency $F_{sw}$ for a converter like the buck which does not have a right-half-plane zero for instance. Practically ...

2

The inductor becomes an AC source when driven this way. From the standpoint of the inductor, its polarity is reversing. If this isn't clear, have a look at illustrations in this answer.

2

No, you should not attempt to drive LEDs with constant voltage. This has been addressed here over and over again.

2

Does connecting the boost converter outputs to linear regulators make any technical sense, or there are better solutions to the problem? Yes it makes sense, if you need less noise. But the switching frequency is not that easy to completely remove, you do need a LC lowpass filter before the LDO, at least. Ultralow Noise Switching Power Supplies

2

The designer was too lazy to figure out the appropriate level shifter with bootstrap. Ok, to be more charitable, they only wanted to see how the SiC device behaved by itself, so they control gate-source bias directly. As it's an n-FET, the gate has to be driven higher than source to turn it on, but not too high such that it will cause the gate to break down. ...

2

Here are my simulations about "starting" behavior. UJ3C120080K3S for SiC (1200V 8A) and 6EWH06FN-E (600V 6A) for diode (should be changed). I will update ... diode voltage too low. Changed for a 1200 V. Peaks are same. You can see that there is (ok, there are short ... but not negligible when choosing devices ...) important peaks of voltage of ...

2

No, a BMS is not a charger. A BMS will not implement charging. Connecting a battery with or without a BMS directly to a DC voltage is wrong. Lithium cells need to be safely charged and that happens with a charger that implements CV-CC charging and will stop charging when batteries are determined to be fully charged.

2

Many of the offline ac-dc power supplies you can find in consumer products operate at a fixed 65-kHz switching frequency. The reason is simple: the EMI standard for conducted emissions starts at 150 kHz and goes up to 30 MHz. When a flyback converter switches at 65 kHz, the second harmonic of the differential mode (DM) current is 130 kHz and is already ...

1

A custom power supply could very well do exactly what you've done, but it all comes down to your requirements. I will try to cover a few notes on your approach and how a custom power supply could do it differently. You don't give requirements for each rail, but from what you've shown you'll have a max current draw of 3A on the 3.3V rails (combined). We'll ...

1

That, 5mV, is a valid concern for analog or high resolution mixed signal circuitry. I put LDO(s) after a switched mode converter.

1

There are buck, boost, buck&boost converters. All of them make a "chopping" of the input current. To make the input current with low ripple, a capacitor bank is used. There are also interleaved converters, like having multiple of them in parallel, having the synced switching frequency but delayed phase, like 4 cylinder engine - they provide ...

1

If the 5V requires only a small current, using a boost (or even a flying-cap converter) from 3.3V would give wide flexibility for the input voltage. For higher 5V current it could instead be a buck-boost directly from Vin, which would be more efficient than boosting from the 3.3V rail. One challenge you face is the large input voltage range required. This ...

1

To a first approximation, in a real buck converter the output voltage is only dependent on the switching duty cycle and the the input voltage. There are small deviations from this because of voltage drop losses across the switches; switching time losses and deadtime losses. If you raise the switching frequency, the switching time and deadtime losses become ...

1

The feedback network, if it’s working properly, servos the voltage back to the set point, regardless of the basic switching frequency. So the frequency can vary (and it does for a constant-on-time regulator) while the output stays the same. The thing that matters is the net duty cycle, which determines the energy delivered to the load. The packets of energy ...

1

Thus, the output voltage will stay the same. Is my assumption correct? Yes, as long as the swicthing frequency is such that "normal" behavior is not affected then of course, the regulation loop will compensate for the change and its effects and just regulate the output voltage to the desired value independent of the switching frequency. What might ...

1

Option 1 does not isolate so if isolation is what you need or want you can't use it. The SN65176B tolerates only -10 to +15V on the A and B pins, in reference to the GND pin, so there is no isolation. Option 2 is better as it keeps isolation of bus and MCU. If you calculated 2V as the max ground voltage difference between devices due to current flowing in ...

1

You say that you are reducing the voltage, so current through the 5Ω should decrease, but you are forgetting that you are not reducing the voltage across the 5Ω load, you are reducing it at the input to the buck converter. The load voltage does not change. The whole point of the converter is to produce a fixed ouput voltage regardless of voltage changes at ...

1

If we consider all non-load components to have no losses, then you can generally say that PowerIn = PowerOut. But I assume that the intended question is something more like: How does a buck converter produce more current at the output than is provided at the (higher voltage) input? In short, the buck converter does not actually manufacture charges flowing as ...

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