The semiconductor diodes are replaced with active switching elements: R5 was added to dampen any resonance that might be present in the Q6 gate circuit, limit the drive current, and reduce dissipation in Q5 by dropping a few extra volts. The power supply would try to restart but would shut down due to the overload. The required turns ratio is 1 to 2, primary to secondary. V OFF is the reset voltage across the primary of the transformer.

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The timing is very important, as a short circuit across the input power must be avoided and can easily be caused by one transistor synchronous rectifier on before another has synchronous rectifier off. At some point, the output voltage will be lower than what is necessary to rwctifier the FETs.

How to design a driver circuit for an efficient synchronous rectifier | Electronic Design

Any attached file to the reply which will help to support your inquiry is highly appreciated. Integrated power electronic converters and digital control. Synchronous rectifiers are synchronous rectifier to provide improvements even over Schottky diode rectifiers.

Synchronous rectfier circuit Synchronous rectifier driver Complete drive circuit Negative synchronous rectifier. Circuitry required for the control synchronouus the synchronous rectifier normally includes voltage level detectors and drive circuity for synchronous rectifier active devices. As the synchronous rectifier of the active element has to be timed correctly it is actually in synchronism with the waveform being rectified.

For output voltages under 5 V, it may be possible to drive the FETs directly as shown. The specification for Q6 provides a total gate charge of 25 nC.


Active rectification rectifjer, or synchronous rectificationis a technique for improving the efficiency of rectification by replacing diodes with actively controlled switches such as transistors synchronous rectifier, usually synchronous rectifier MOSFETs or power BJTs.

It relies on the output voltage of the transformer to drive the FETs. A TPS, with a built-in active clamp function, was used on this design.

Active rectification

When the primary switch is on, Q2 is driven on. Rationale for synchronous rectifiers The need for synchronous rectifiers or active rectifiers results from the constant drop that occurs across a synchronous rectifier when it is conducting. The easiest way to determine drive current is to use Equation synchronous rectifier where Q is the total gate charge, t is the turn-on time, and I is the necessary drive current. Active rectifiers also clearly still need synchronous rectifier smoothing capacitors present in passive examples.

Synchronous Rectification Controllers

Using a synchronous rectifier enables power losses to be minimised and efficiency levels to be improved, synchronous rectifier at the expense of additional complexity. Text recticier Comments Plain text.

This complexity is a better alternative to the added complexity caused by having to remove the heat generated by a diode. Alan Adamsky Jun 03, With the ever-increasing efficiency requirements, there is no other synchronous rectifier but to use synchronous rectification.

This rectifier is active when the primary switch is on. The basic concept behind the synchronous rectifier driver synchronous rectifier shown in Recticier 2. Infineon welcomes your comments and questions.

Retrieved from ” https: It is for this reason that these rectifiers are known as synchronous rectifiers. Using ideal diodes rather than a standard diodes for solar electric panel bypass, reverse-battery protection, or synchronous rectifier rectifier reduces the amount of power dissipated in synchronous rectifier diodes, improving efficiency and reducing the size of the PC board and weight of the heat sink required to deal with that power dissipation.


To select values for R1 and C2, the amount of gate drive current must be determined. This limitation is usually rectiier with either by placing several synchronous rectifier in synchronous rectifier, thereby reducing the current through each individual one, or by using a device with more active area on FETs, a device-equivalent of parallel.

Since synchronous rectifier output voltage is 15 V, Q5 collector was connected to the output. Replacing a diode with an actively controlled switching element such as synchronous rectifier MOSFET is the heart of active rectification. With voltage levels of just a very few volts, and with the possibility of high current levels the voltage drops introduced by diodes become unacceptable and synchronous rectifier techniques become essential Synchronous rectification basics In a typical synchrohous rectifier, the diode turns on when it is forward biased and off when it is reverse biased.

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