How does zvs work

These trends combine to increase the voltage drop and associated switching losses across the regulator. For example a process control system may call for regulation from 24V to 3. This in turn limits the use of smaller passive components for filtering, penalizing the density of the total solution. These must be overcome or avoided to achieve any significant boost to regulator performance.

A better solution uses zero-voltage-switching ZVS topology, which allows for operation at a higher frequency and at higher input voltages without sacrificing efficiency. Figure 1 compares a conventional buck regulator with a version modified for ZVS operation.

These losses increase as the switching frequency or input voltage increases. Sign up to join this community. The best answers are voted up and rise to the top.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Asked 5 years, 5 months ago. Active 3 years, 7 months ago. Viewed 6k times.

Analytical calculation of resonant inductance for zero voltage switching in phase-shifted full-bridge converters. Bet the answer is in there, but not sure when I'll get to it The high-value 50mH is the expected series-choke on the DC supply.

These oscillate using one choke on each fet drain, or one choke as above, or one choke on a center-tapped tank coil. Add a comment. Active Oldest Votes. With this in mind, we can now get to your questions How is oscillation initiated? Note that: This modified circuit does not have the same issue, and upon reset it starts oscillating immediately again.

The output voltage is much higher than your simulated version vs V , because both halves of the output period are being used effectively instead of just half. If you slow down the simulation, you'll note that your circuit has significantly more overlap where both MOSFETs are on. The high voltage driver was originally touted as an improved way of driving flyback cores. Until the introduction of Mazilli's circuit, flybacks were typically driven with a single transistor and a feedback winding or with a push-pull transistor configuration e.

The operation of the circuit is descibed below, including its drawbacks and improvements. The operation also discusses selection of components, an area that is typically not well-covered at most sites. It appears that component selection is not well understood because of the unique characteristics of a resonant Royer-type oscillator.

The component stresses are considerable with this type of circuit because of the resonant operation of the primary which generates large voltages and currents that can stress poorly-selected components.

This section describes the basic operation of the ZVS Driver, including the design and purpose and selection of components. The descriptions below refer to Schematic 1 and Schematic 2. The operation of this kind of driver for the primary of a transformer is very straightforward and need not be discussed here.

The circuit is fed from the power supply through a center-tapped primary coil and a single choke or from two separate chokes connected to the FET drains as shown in Schematic 1. With the two 47uH uH choke coils and the resonating capacitance across the primary, the circuit operates as a "Royer" type inverter where the primary is resonated with the capacitance and where the chokes keep the power supply from reducing the resonant action of the primary.

These chokes also keep the primary oscillations from feeding back to the power supply. The role of these chokes and the resonating capacitor are discussed more fully below.

Zener diodes are connected across the FET gates so that the maximum gate to drain voltage is not exceeded. Use of a zener voltage higher than the minimum gate to source turn-on voltage ensures that the FETs are conducting at a high level. These diodes provide a fast turn off of the FET gates when they are driven toward ground as the opposite-phase FET saturates. Although the forward-biased diode of zener can be used, it is significantly slower than the Schottky diode.

Each FET is turned off as the opposite-phase FET turns on and this continues until the primary voltage reverses phase. This phase reversal happens when the primary voltage crosses zero so that switching occurs when there is zero voltage across the FET. In some cases, the FETs are run without zeners to ground and the gate voltage is limited by a voltage regulator such as a With this configuration, the resistors from the power supply to the gate can be lower e.

Note that the gate bias voltage must be lower than the drain supply voltage to ensure that the coupling diodes are reverse biased when the drain is high. Also note that the dissipation of the gate bias resistors should be carefully watched as their resistances are reduced.

Because of the resonant voltage rise in the primary, the FET drains must withstand more than 2 times the power supply voltage. Most designs recommend a voltage rating of 3 to 4 times the supply voltage.

Because of the resonant current rise in the primary, the FETs must be able to handle currents about 4 times the nominal power supply current. This requirement is normally satisfied by selecting FETs that have high continuous drain currents and Rds on resistances of less than a tenth of an Ohm.

Drain "on" resistance is 0. With reasonably fast switching, dissipation requirements can normally be satisfied with relatively small heat sinks e. A small heat sink or on-board copper fill can generally provide the needed dissipation of a Watt or so. As noted earlier, the zener diodes limit the FET gate to source voltage to the maximum specified in the spec sheet.

The zener limiting resistors not only limit the maximum dissipation of the zeners but also drive the gate to source capacitance of the FETs. A separate regulated gate supply voltage, should be set less than the zener voltage and the nominal FET drain voltage.

Or, the zener can be eliminated or substituted with a reverse-biased diode. If the gate supply voltage is at the same voltage as the supply voltage, the zener dissipation should be checked for the operating voltage. For fast operation, the zener current limiting resistors should be as small as possible while not challenging any power ratings. The resistors are typically tied to the power supply which can cause both zener and limiting resistor dissipation problems when increasing the supply voltage.

As previously noted, a better design is to use a separate gate power supply fed off the main power supply, as shown in Schematic 2. Because the driver I built operates at 24 VDC, the gate bias voltage was established by regulating the 24 Volt supply down to 15 Volts with a small LM regulator board. The board's trimpot was adjusted for an output of 15 Volts.

Using this approach, the bias supply can be regulated with only the requirement that the power supply voltage is always at least a few Volts larger than the desired output voltage 15 Volts. If you want a higher voltage power supply, then you might want to consider modifying a microwave oven transformer, but this is another project. As I don't have a large power supply so I used six 6v sealed lead acid batteries all in series to gain 36v to power my ZVS driver.

Then finaly the other bits and pieces you may need such as solder, thick wires, etc. The 5 turns of wire as the primary is not critical, you can add or remove windings for different performance.

The voltage input to the driver may affect the number of turns required as well. In general, if you want a higher voltage, the inductor should have an higher value, if you want more current, the inductor should have an lower value.

Changing the value of the capacitor can also affect the performance depending on the flyback transformer, again, make sure you use good quality capacitor. Not much to say here, just get your toolbox, read the schematics and build it! When winding the flyback transformer, make sure both wire go the same way.

When you first power on your ZVS driver, start with 12v input to make sure everything thing is working. Then you can increase the input voltage up to 36v. You can power the ZVS driver above 36v, but then you risk blowing up your driver, check step 7 for instructions for modifying your ZVS driver to handle higher input voltages.

You may hear an very high pitched squeal from your ZVS driver, don't worry, that is normal. What ever you use as your negative terminal, it will get hot, very hot! The arc will melt any thin wire you use into little metal balls and steal will just fly everywhere, which is cool and dangerous!

If anyone has a good explnation why the negative terminal get so hot and the positive terminal remains fairly cool, I'd like to know.. This is because when the arc got inside the bulb, the gas inside heats up, causing it to expand and escaping through the hole thus creating a "plasma thrower".

I have not tried this yet, but there is a revision of the ZVS driver by Andrinerii. The fun does not stop there, if you are hungry for more bigger, hotter, and beastly arcs, a few changes to your ZVS driver should be made to handle higher input voltages.

Change the 12v zenner diode to 15v zenner diode. Increase the number of windings on your flyback transformer. Increase the value of the inductor. I heard that some people had operated their ZVS driver at voltages over , just imagine how massive their arcs must be!