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Технический раздел / Re: Двухтактник на IRFP460
« : 11 Октябрь 2018, 17:25:37 »
Вот ещё некоторые полезные рекомендации по передатчику Криса Вилсона
In general, it's a bad idea to use AC coupling capacitors with the inputs of the driver chip.
Next, the IR2110 is weaker than the MCP1404, so drives the MOSFETs somewhat slower.
One more, the IR2110 has asymmetric propagation delays (turning OFF faster than ON), this provides some dead time in the original circuit.
Last: you can use your 12V supply for the IR2110 logic side, this is clearly stated in the datasheet, so no need for the 7805.
If your exciter doesn't provide enough level to drive the IR2110 input, you'll have to use some kind of level translator chip, like a 74LCX08, not AC coupling. AC coupling is "forbidden" with this kind of drivers. Treat them as "logic" ICs (like the 74xx series or whatever), not analog stuff that may work fine with AC coupling. These drivers must be driven by proper "logic" levels, like the output of a '04 inverter (or the '74 Flipflop) operating at 3.3V or 5V.
Provide a solid ground plane for the MOSFETs sources and place the driver chip on this same solid ground plane, do not use wiring to connect the driver outputs to the gate and source. Keep the ground connection from MOSFET sources to the driver chip as short and solid as possible. You'll also need a proper ground plane from the logic chip driving the MOSFET driver to the MOSFET drivers. These drivers are quite fast and can pick up all kind of ground noise at their inputs, resulting in oscillation. The IR2110 is way much less sensitive here than the other one, so for a non-optimum layout, the IR2110 would be the better choice anyway. Stay away from more modern parts, as they often are faster and more sensitive to noise and ground shifting. They need real good layouts, decoupling and so on, and won't work reliably on a poor prototype built. Don't drive MOSFETs faster than required for your purpose.
Driving the MOSFETs too fast (by using a beefier driver chip) can cause all kinds of unwanted feedback and oscillation. Real good ground plane design helps you out of here, or just use larger gate resistors to drive the MOSFETs somewhat slower. Your description of 12V supply voltage causing havoc points into this direction.
Having not enough dead time can cause cross conduction with the MOSFETs, resulting in large unwanted currents circulating in your circuit through the ouput transformer. These also can cause all kinds of distorted waveforms until full destruction of the power stage. If the driver chip (the MCP1404) doesn't provide dead time on it's own, you'll have to provide some circuitry. Two 180° shifted waveforms aren't enough here, there must be some delay from the falling edge of one phase to the rising edge of the other phase, in both directions. The delay is required in the ballpark of 10ns ... 100ns.
Ссылка https://www.eevblog.com/forum/beginners/class-d-fet-driver-questions-(long-)/
In general, it's a bad idea to use AC coupling capacitors with the inputs of the driver chip.
Next, the IR2110 is weaker than the MCP1404, so drives the MOSFETs somewhat slower.
One more, the IR2110 has asymmetric propagation delays (turning OFF faster than ON), this provides some dead time in the original circuit.
Last: you can use your 12V supply for the IR2110 logic side, this is clearly stated in the datasheet, so no need for the 7805.
If your exciter doesn't provide enough level to drive the IR2110 input, you'll have to use some kind of level translator chip, like a 74LCX08, not AC coupling. AC coupling is "forbidden" with this kind of drivers. Treat them as "logic" ICs (like the 74xx series or whatever), not analog stuff that may work fine with AC coupling. These drivers must be driven by proper "logic" levels, like the output of a '04 inverter (or the '74 Flipflop) operating at 3.3V or 5V.
Provide a solid ground plane for the MOSFETs sources and place the driver chip on this same solid ground plane, do not use wiring to connect the driver outputs to the gate and source. Keep the ground connection from MOSFET sources to the driver chip as short and solid as possible. You'll also need a proper ground plane from the logic chip driving the MOSFET driver to the MOSFET drivers. These drivers are quite fast and can pick up all kind of ground noise at their inputs, resulting in oscillation. The IR2110 is way much less sensitive here than the other one, so for a non-optimum layout, the IR2110 would be the better choice anyway. Stay away from more modern parts, as they often are faster and more sensitive to noise and ground shifting. They need real good layouts, decoupling and so on, and won't work reliably on a poor prototype built. Don't drive MOSFETs faster than required for your purpose.
Driving the MOSFETs too fast (by using a beefier driver chip) can cause all kinds of unwanted feedback and oscillation. Real good ground plane design helps you out of here, or just use larger gate resistors to drive the MOSFETs somewhat slower. Your description of 12V supply voltage causing havoc points into this direction.
Having not enough dead time can cause cross conduction with the MOSFETs, resulting in large unwanted currents circulating in your circuit through the ouput transformer. These also can cause all kinds of distorted waveforms until full destruction of the power stage. If the driver chip (the MCP1404) doesn't provide dead time on it's own, you'll have to provide some circuitry. Two 180° shifted waveforms aren't enough here, there must be some delay from the falling edge of one phase to the rising edge of the other phase, in both directions. The delay is required in the ballpark of 10ns ... 100ns.
Ссылка https://www.eevblog.com/forum/beginners/class-d-fet-driver-questions-(long-)/
