Do I Need Freewheel Diodes for My H Bridge Mosfet Inverter Circuit?

[khalil977]

TL;DR

hello i am designing H bridbe mosfet inverter with gate driver HCPL3120 i need help in circuit please help circuit diagram with all four drivers connected i am very confused about that please help me
Thanks

i am designing H bridbe mosfet inverter with gate driver HCPL3120 i need help in circuit

 

[Guineafowl]

Post a diagram of what you’ve got so far.

 

[khalil977]

 

[khalil977]

Plz correct my circuit diagram thanks

 

[Guineafowl]

Plz correct my circuit diagram thanks

What is wrong with the way the circuit works? Have you scoped it?

 

[Baluncore]

Welcome to PF.

The driver is capable of 2 amps, but you show 10k gate resistors.
I would expect 10 ohms.

You may need to connect the source of each mosfet to the pin 5 common output of the floating driver chip.

You must provide a boosted supply voltage for each high-side driver. That will require a capacitor and diode on each high-side driver.

Additional information required before revision of circuit diagram.
1. Is pin 3 common ground on the J2, J3, J4 & J5 ?
2. What is the J7 positive voltage?
3. What is the J8 negative voltage?

 

[Baluncore]

The IRF740 suggests you will be using high voltages, greater than the opto-isolator can handle, so you will need a floating supply for the low side switch, with a diode and capacitor for the high-side switch. That is necessary to turn on, and hold the hi-side switch on because the gate voltage must be higher than the positive supply rail.

You must find some way of preventing both Hi and Lo sides being turned on at the same time. I think there are better half-bridge drivers available that will prevent both switches conducting at the same time.

If you are driving an inductive or motor load you will need flyback or freewheel diodes across all mosfets.

Here is an improved half-bridge circuit using the HCLP-3020 and IRF740.
Use two half-bridge circuits to make a full H-bridge.

 

[Dullard]

You must find some way of preventing both Hi and Lo sides being turned on at the same time. I think there are better half-bridge drivers available that will prevent both switches conducting at the same time.

Definitely. Belt and Suspenders definitely. GPS IIA drove their solar arrays with an H-bridge. The 'legs' were controlled by a pair of light-sensing diodes arranged with a 'null' when aimed at the sun. Reactive components were added to the GPS II design as part of a hardening exercise. Reactive components + slip-ring (intermittent) connections = high-rate spikes. There are no service calls to 12,500 miles.

 

[essenmein]

If you are driving an inductive or motor load you will need flyback or freewheel diodes across all mosfets.

Adding freewheel diodes is only something you need to do with certain devices, BJT for sure, IGBT also natively needs it, although some are co packaged with diodes, if using bare die then IGBT needs a diode.

Mosfets have the intrinsic body diode that serves the purpose of freewheeling for all but the most demanding situations, where some people will put a schottky in parrallel to reduce conducted losses and reduce reverse recovery, although most of the gains can be had by active rectification, ie turning the FET on if its conducting regardless of the direction of current flow.