using a synchronous rectifier in a boost circuit
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From: Jamie on 28 Jun 2010 21:02 Hi, I am making a high power boost circuit (500watts+ with 12VDC input and 13.5VDC output). The boost diode dissipates more than 30watts so I am looking for a circuit to replace this diode with a synchronous rectifier. Are there any boost PWM controller IC's out there that can control an external sync rectifier (n-mosfet) to replace the boost diode? I have found many buck IC's with sync rectifier control but haven't seen one for the boost configuration. I have tried rigging up my own sync rectifier with a bit of success but it would be nice to find a boost IC that has this function built in! :) cheers, Jamie
From: Vladimir Vassilevsky on 28 Jun 2010 21:32 Jamie wrote: > Hi, > > I am making a high power boost circuit (500watts+ with 12VDC input and > 13.5VDC output). I wonder what is this for. > The boost diode dissipates more than 30watts so I am > looking for a circuit to replace this diode with a synchronous > rectifier. Are there any boost PWM controller IC's out there that can > control an external sync rectifier (n-mosfet) to replace the boost > diode? I have found many buck IC's with sync rectifier control but > haven't seen one for the boost configuration. I have tried rigging up > my own sync rectifier with a bit of success but it would be nice to find > a boost IC that has this function built in! :) Make a transformer buck from 12 to 1.5V, then connect it in series to the input 12V? VLV
From: Joerg on 28 Jun 2010 21:41 Jamie wrote: > Hi, > > I am making a high power boost circuit (500watts+ with 12VDC input and > 13.5VDC output). The boost diode dissipates more than 30watts so I am > looking for a circuit to replace this diode with a synchronous > rectifier. Are there any boost PWM controller IC's out there that can > control an external sync rectifier (n-mosfet) to replace the boost > diode? I have found many buck IC's with sync rectifier control but > haven't seen one for the boost configuration. I have tried rigging up > my own sync rectifier with a bit of success but it would be nice to find > a boost IC that has this function built in! :) > See if this one fits your needs, comes with LTSpice simulator model and the whole nine yards: http://cds.linear.com/docs/Datasheet/3813fb.pdf -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jamie on 28 Jun 2010 23:22 On 6/28/2010 6:32 PM, Vladimir Vassilevsky wrote: > > > Jamie wrote: > >> Hi, >> >> I am making a high power boost circuit (500watts+ with 12VDC input and >> 13.5VDC output). > > I wonder what is this for. Hi, I am using an off the shelf ATX power factor corrected 750Watt powersupply as the 12VDC input, and then boosting this to ~13.5VDC for charging lead acid batteries at 600watts+. This is part of my "ATX power tower" project, a cheap home energy system in a PC case :) Its going to be open source, and designed in eagle cad. Here are some of the specs: grid input (charges batteries and/or powers load) 120VAC generator input (charges batteries and/or powers load) internal auto transfer relays to auto-select power sources solar/wind/hydro compatible MPPT input (charges batteries) modular inverter interface (turns on when grid is down) optional battery desulphator outputs fully microcontroller controlled to set charging voltages and monitor currents etc I am putting this circuitry on an ATX rev 2.2 compatible PCB so that it can be installed into a surplus ATX PC case. cheers, Jamie > >> The boost diode dissipates more than 30watts so I am looking for a >> circuit to replace this diode with a synchronous rectifier. Are there >> any boost PWM controller IC's out there that can control an external >> sync rectifier (n-mosfet) to replace the boost diode? I have found >> many buck IC's with sync rectifier control but haven't seen one for >> the boost configuration. I have tried rigging up my own sync rectifier >> with a bit of success but it would be nice to find a boost IC that has >> this function built in! :) > > Make a transformer buck from 12 to 1.5V, then connect it in series to > the input 12V? > > VLV
From: Jamie on 28 Jun 2010 23:25
On 6/28/2010 6:41 PM, Joerg wrote: > Jamie wrote: >> Hi, >> >> I am making a high power boost circuit (500watts+ with 12VDC input and >> 13.5VDC output). The boost diode dissipates more than 30watts so I am >> looking for a circuit to replace this diode with a synchronous >> rectifier. Are there any boost PWM controller IC's out there that can >> control an external sync rectifier (n-mosfet) to replace the boost >> diode? I have found many buck IC's with sync rectifier control but >> haven't seen one for the boost configuration. I have tried rigging up >> my own sync rectifier with a bit of success but it would be nice to find >> a boost IC that has this function built in! :) >> > > See if this one fits your needs, comes with LTSpice simulator model and > the whole nine yards: > > http://cds.linear.com/docs/Datasheet/3813fb.pdf Thanks Joerg, that IC looks great! I have a sim of it running with 12VDC input and 13.3VDC output at about 750watts and 97% efficiency measured in ltspice. I would be happy with anything above 90%, but this makes it a lot easier to heatsink the sync rectifier when it dissipates 10watts instead of 30watts+ for a diode. cheers, Jamie > |