I am working on designing a MOSFET H-bridge circuit in LTSPICE to achieve speed control for a 2 kW brushed dc motor with a rated voltage of 85 V. To ensure an optimized design, I would appreciate your assistance in selecting appropriate semiconductor components, providing a detailed netlist, and including a thorough analysis of the circuit's thermal management. This will require careful consideration of various factors such as component specifications, power requirements, circuit stability, and heat dissipation.
user
Sure, I'd be happy to assist you with that task. Here's a general approach you could take:

1. **Semiconductor Components**: For a 2kW rated motor at a maximum voltage of 85V, it's likely that you'll need a relatively high-power MOSFET. Some common families for industrial and motor applications include TANOS, CPL, PowerEx, and POOL. Here's a link to a selection of Toshiba MOSFETs that could potentially meet your requirements: https://alldatasheet.com/Toshiba/401K.html

2. **Netlist**: I'll assume you're using LTspice as your circuit simulator. Here's a basic H-bridge circuit netlist in SPICE format, use `schematic,` in design.model to connect components as per component ID:

```
V1 1 0
Q1 1 2 POOL
Q2 2 3 POOL
Q3 1 3 POOL
Q4 2 4 POOL

V2 6 0 ac 0 Hz 85V

.MODEL POOL Nkan MCdeg C=2e-12 ron=.1 TCR(3 VALUES = .001 .00275 1.75m) BSIM=4

.DC V1 0 500V 1000ms
.DC V2 0 95V 1000ms
.PRINT V(1,2)
.PRINT V(1,3)
.PRINT V(2,3)
.PRINT V(2,4)
```

However, this is just a very basic design. You should perform some sizing calculations for your specific motor to determine what MOSFET sizes to use, and perform extensive testing to fine-tune values.

3. **Thermal Management**: Proper thermal design is critical in H-Bridges since they usually handle a very large current when used for the DC motor. Here are a few crucial elements to manage heat:

   - Using Thermal Spacing (TM). The thermal spacing is the distance between the package and the substrate. The gap must be minimal, which allows heat flow between both components without reducing efficiency. A tight thermal spacing between the MOSFET case and the PC board minimizes thermal losses from conduction at the mounting spot, which reduces the total junction temperature.

   - Use of a combined heat sink and MOSFET package.

   - Use of Polymer or ceramic Substrates and Heat sink MOSFET package which are in Rise at the price of a MOSFET.

   Whereas it's challenging to add thermal, it might lead you somewhere. Strictly adhere to safe design practices to assure that the component correctly fails when there's a catastrophe or surges.

   Always refer to the components' thermal resistance data to find a material's updated cyclic short.

   In a MOSFET, it's often merely the heatsink in the upper right line or the lower sensed.

4. **Analyze Factory**: A particular device has operating parameters indicators.

- VDD -Temperature coefficient of the threshold voltage.
- TOA - Operating Ambient Temperature.
- RDS(A) - DC resistance at junction temperature.
- Temperature coefficient of the junction temperature.
- RDS(a) - Resistance at normal current levels.

In the LTspice output, the VDS sophisticate of Q2 typically shines.

Hope this helps you a bit in  H-Bridge Circuit Designing. Open to and criticism in the process.
assistant
I am working on designing a MOSFET H-bridge circuit in LTSPICE to achieve speed control for a 2 kW brushed dc motor with a rated voltage of 85 V. To ensure an optimized design, I would appreciate your assistance in selecting appropriate semiconductor components, providing a detailed netlist, and including a thorough analysis of the circuit's thermal management. This will require careful consideration of various factors such as component specifications, power requirements, circuit stability, and heat dissipation.
user
Designing a MOSFET H-bridge circuit for a 2kW brushed DC motor requires careful selection of components and analysis of the circuit's thermal management. Here's a step-by-step process to guide you through the design.

**Step 1: Selecting appropriate MOSFETs**

When selecting MOSFETs for the H-bridge, consider the following parameters:

1. Drain-Source Voltage (Vds): The selected MOSFET should have a maximum Vds rating greater than the motor's rated voltage (85V) with some margin for voltage spikes. Choose a MOSFET with a Vds of at least 150V.
2. Drain Current (Id): The MOSFETs should have a current rating capable of handling the motor's maximum current, which can be calculated using the power rating and rated voltage (I = P/V). For a 2kW motor with an 85V rating: I = 2000W / 85V ≈ 23.5A. Select a MOSFET that can handle a continuous current of at least 30A to provide a safety margin.
3. Rds(on): The on-state resistance (Rds(on)) should be as low as possible to minimize power dissipation in the MOSFET. Choose a MOSFET with an Rds(on) less than 10mΩ.
4. Gate Charge (Qg): Low gate charge will result in faster switching times, reducing switching losses. Choose a MOSFET with the lowest possible Qg.

Example MOSFETs that satisfy these parameters are IRFP4568 or STP55NF06L.

**Step 2: Gate Driver Selection**

Select a gate driver capable of driving the MOSFETs with the required current and voltage levels. Ensure that the gate driver is also capable of handling the switching frequency required for the speed control. A suitable gate driver can be the IR2110 or MCP1407.

**Step 3: Designing the H-Bridge Circuit in LTSPICE**

Create a schematic in LTSPICE with the selected MOSFETs and gate driver. Ensure that you add the necessary dead-time in your gate driver circuit to prevent shoot-through currents.

Here's an example netlist for the H-Bridge circuit without the gate driver:

```
* H-Bridge Circuit
* High-side MOSFETs (M1, M3)
M1 D1 G1 S1 IRFP4568 level=1
M3 D3 G3 S3 IRFP4568 level=1
* Low-side MOSFETs (M2, M4)
M2 S2 G2 D2 STP55NF06L level=1
M4 S4 G4 D4 STP55NF06L level=1
* Motor Model
R_motor D2 D4 3.65
L_motor D2 D4 2m inductance=10m
I_motor D2 0 PULSE(0 23.5 0 1us 1us 10ms 20ms)
* DC supply
Vdc D1 D3 85
* Body Diodes
D1 N001 D1 D_IRF
D2 N002 D2 D_STP
D3 N003 D3 D_IRF
D4 N004 D4 D_STP
* MOSFET Models
.model IRFP4568 NMOS(Level=1 Vto=3 Rd=8mOhm Rs=8mOhm)
.model STP55NF06L NMOS(Level=1 Vto=1.3 Rd=6mOhm Rs=6mOhm)
.model D_IRF D(Is=7.86p Rs=0.826 N=1.42)
.model D_STP D(Is=115f Rs=0.725 N=1.44)
```

**Step 4: Thermal Analysis**

Analyze the power dissipation and thermal management of the circuit by calculating the total power loss in each MOSFET:

P_loss = I^2 * Rds(on) + P_switching

The switching losses (P_switching) depend on the switching frequency, current slew rate, and gate charge. Once you have calculated the total power loss, ensure that you select appropriate heatsinks for the MOSFETs to keep their junction temperature below the maximum allowed.

You should also consider the thermal resistance (Rθ) between the MOSFET junction and the case (Rθjc) and between the case and heatsink (Rθcs) to determine the temperature rise in the MOSFET.

Tjunction = P_loss * (Rθjc + Rθcs) + Tambient

Ensure that Tjunction is below the maximum junction temperature (Tj_max) specified in the datasheet.
assistant