User’s Guide
ROHM Solution Simulator

PTC Heater Thermal Simulation
This documents introduces and describes the use of a simulation environment that allows simultaneous electrical simulation ofPTC (Positive Temperature Coefficient) heaters and temperature simulation of built-in devices. By changing the parameters of thecomponents, it is possible to simulate a wide range of conditions.

1Simulation circuit

Figure 1. Simulation circuit
In this circuit diagram, the black and blue lines show the electrical simulation circuit and the red lines show the thermal simulation
circuit.
The circuit consists of three IGBTs connected in parallel, which function as switches. A load resistor (heater) is connected toeach IGBT and is driven independently. The load current is adjusted in three steps only by turning the three IGBTs on and off;
no fine-tuning via switches is envisaged. The total current of the three loads is detected by a shunt resistor and a circuit isprovided to prevent over current.
The thermal simulation circuit creates a thermal simulation model (ROM *1) of the device losses calculated in the electricalsimulation and a typical PTC heater (including a water-cooled environment), and calculates the temperature of the IGBTs andshunt resistor.
*1 ROM (Reduced Order Model): A model created by 3D-CAE using a technique to reduce the dimensionality to 1D.

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User’s Guide

Simulation method
Simulation settings such as simulation time and convergence
options can be set from “Simulation Settings” shown in Figure 2, andthe initial simulation settings are shown in Table 1.

Simulation
SettingsIf you are having problems with the convergence of the simulation,
you can change the advanced options to fix the problem. The

Simulate

simulation temperature and various parameters of the electricalcircuit are defined in “Manual Options”.
Figure 2. Simulation Settings and execution
Table 1. Initial values for Simulation Settings
Parameters
Simulation TypeEnd time
Advanced Options
Manual Options

Initial values

Remarks
Do not change the simulation typeTime-Domain
5000 secs
More Speed

Simulation temperature of the circuit
Set to around the convergence temperature ofthe IGBTSee Table 2 for details.TEMP 100.PARAM …

3Simulation conditions
3.1 Definition of parameters
The parameters for the components shown in blue in
Figure 3 are defined in the manual options as they need
to be set in the simulation conditions.
Table 2 shows the initial values of the parameters. Thesevalues are written in a text box in the “Manual Options”
section of the simulation settings, as shown in Figure 4.
Figure 3. Definition of component parameters
Table 2. Simulation conditions
Parameters
VIN
ILOAD1ILOAD2ILOAD3
VGdelay1
VGdelay2
VGdelay3© 2021 ROHM Co., Ltd.

Variable namesV_VIN
I_LOAD1
I_LOAD2
I_LOAD3
VG_delay1
VG_delay2
VG_delay3

Initial values
400
10101001000
2000

2/8UnitVAAA
sec
secsecDescription

When IGBT1 is on
When IGBT2 is on
When IGBT3 is on

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Write parameters

Figure 4. Definition of parameters

3.2 Over current protection
Figure 5 shows the over current protection circuit. The load current is detected by a low-side sense circuit using a shunt
resistor and an op-amp. The total current flowing through the load generates a voltage of ΔVSHUNT via the shunt resistor.
This voltage is differentially amplified by the op-amp and if it exceeds the threshold of the “Voltage to Digital” stage, thenext stage turns on and protection begins. If the input offset voltage of the op-amp is ignored, the output VO of the op-amp
can be expressed by the following equation.

𝑉𝑂 = 𝐼𝐿𝑂𝐴𝐷 × 𝑅𝑆𝐻𝑈𝑁𝑇 ×

𝑅2
𝑅1[𝑉]

The default circuit is ILOAD=30 A, RSHUNT=1 mΩ, R1=2 kΩ, R2=120 kΩ, so the output VO=1.8 V. The threshold value for“Voltage to Digital” is set to 2 V (over current ≈ 33.3 A), so the protection is not activated.

Figure 5. Over current protection circuit© 2021 ROHM Co., Ltd.

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3.3 Thermal circuit
The “PTC-heater” symbol in Figure 6 is the thermal simulation model of the PTC heater (ROM). Also, Table 3 shows theterminal description for the PTC heater thermal simulation model.

Figure 6. PTC heater thermal simulation model

Table 3. Terminal description of the thermal simulation model
Terminal name
S_S_IGBT_1
S_S_IGBT_2
S_S_IGBT_3
S_S_Res
F_Heater
F_Water_Near_Side
F_Water_Far_Side
F_20CAmbient
S_M_IGBT1_mold
S_M_IGBT2_mold
S_M_IGBT3_mold
S_M_R_lead

Description
Inputs the losses of IGBT1 and monitors TJ
Inputs the losses of IGBT2 and monitors TJ
Inputs the losses of IGBT3 and monitors TJ
Inputs the losses of RSHUNT and monitors TJ
Heater temperature
Cooling water temperature (inlet)
Cooling water temperature (outlet)
Ambient temperature
Monitors the mold temperature of IGBT1 (received at high impedance)
Monitors the mold temperature of IGBT2 (received at high impedance)
Monitors the mold temperature of IGBT3 (received at high impedance)
Monitors the lead temperature of RSHUNT (received at high impedance)• The S_S_xxxx pin allows monitoring of the device temperature by inputting the device losses.
• The F_xxxx pin is connected to “tc_amb” and is set to the temperature at that location.
• The S_M_xxxx pin allows monitoring of the temperature of the IGBT mold and the lead temperature of the shunt resistor.

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Parts listFigure 7 shows the main component names. The initial values for each component can be found in Table 4. Some components
allow the user to select the component to be used from a predetermined list of component names. The components that can bechanged and the component name list are shown in Table 5. To change the name of a component, right-click on the component
and select “Properties” as shown in Figure 8. In “Property Editor”, select “Spicelib Part” and choose the name of the component
you want to use.

Figure 7. Main component names

Table 4. Initial values of components
Component name
Q1, Q2, Q3
RSHUNTRL1, RL2, RL3
OPAMP© 2021 ROHM Co., Ltd.

Function
IGBT
Resistor
Load Resistor
Opamp

Initial values
RGS00TS65D1mΩ
{Vin/ILOADx}
Parameter model

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Remarks
Can be changed
PMR100
Fixed
LMR1802G-LB

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Table 5. List of components that can be changed and component names
Component name
Q1, Q2, Q3

FunctionIGBT

Product name
RGC80TSX8R
RGCL60TS60D
RGCL80TS60D
RGS00TS65D
RGS00TS65E
RGS50TSX2DHR
RGS60TS65D
RGS80TS65D
RGS80TSX2DHR
RGT00TS65D
RGT16TM65D
RGT30TM65D
RGT40TS65D
RGT50TS65D
RGT60TS65D
RGT80TS65D
RGT8TM65D
RGTH00TS65D
RGTH40TS65D
RGTH50TS65D
RGTH60TS65D
RGTH80TS65D
RGTV60TS65D
RGW00TS65D
RGW60TS65D
RGW80TS65D

Specifications
1800V, 40A
600V, 30A
600V, 40A
650V, 50A
650V, 50A
1200V, 25A
650V, 30A
650V, 40A
1200V, 40A
650V, 50A
650V, 5A
650V, 8A
650V, 20A
650V, 25A650V, 30A
650V, 40A
650V, 3A
650V, 50A
650V, 20A
650V, 25A
650V, 30A
650V, 40A
650V, 30A
650V, 50A
650V, 30A
650V, 40A

Figure 8. Changing the name of the component to be used

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Links to related documents
5.1

Products
IGBT (TO247 package)
Shunt Resistors PSR series
Ground Sense Operation Amplifier

5.2

Application Note
Low-Side Current Sensing Circuit Design© 2021 ROHM Co., Ltd.

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Reference: About the PTC heater thermal simulation model
An image of the 3D model used to create the thermal simulation model (ROM) is shown in Figure A. Structural information isalso shown in Table A.

Board outline

Water coolingpipe

Cooling water
inlet

Cooling wateroutletView from the top

View from the bottom

IGBT (TO247)
From left: IGBT1, IGBT2, IGBT3RSHUNT (PSR100)

Board
Insulation
sheet
Aluminum
housing
Water flow

IGBT periphery

BoardFigure A. 3D image of the PTC heater

Table A. Structural information
Structural parts
Aluminum housing
BoardInsulation sheet

Description
Outline dimensions: 250mm × 110mm × 120mm
Outline dimensions: 100mm × 90mm × 1.6mmt
Board material: FR-4
Copper foil thickness: 70 μm (2 oz copper foil)
Thickness: 1mm*In order to save simulation time, the thermal capacity of the aluminum housing is not taken into account.

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NoticeNotes
1) The information contained herein is subject to change without notice.
2) Before you use our Products, please contact our sales representative and verify the latest specifications :3) Although ROHM is continuously working to improve product reliability and quality, semiconductors can break down and malfunction due to various factors.
Therefore, in order to prevent personal injury or fire arising from failure, please take safetymeasures such as complying with the derating characteristics, implementing redundant andfire prevention designs, and utilizing backups and fail-safe procedures. ROHM shall have noresponsibility for any damages arising out of the use of our Poducts beyond the rating specified byROHM.
4) Examples of application circuits, circuit constants and any other information contained herein areprovided only to illustrate the standard usage and operations of the Products. The peripheral
conditions must be taken into account when designing circuits for mass production.
5) The technical information specified herein is intended only to show the typical functions of andexamples of application circuits for the Products. ROHM does not grant you, explicitly or implicitly,
any license to use or exercise intellectual property or other rights held by ROHM or any otherparties. ROHM shall have no responsibility whatsoever for any dispute arising out of the use ofsuch technical information.
6) The Products specified in this document are not designed to be radiation tolerant.
7) For use of our Products in applications requiring a high degree of reliability (as exemplifiedbelow), please contact and consult with a ROHM representative : transportation equipment (i.e.
cars, ships, trains), primary communication equipment, traffic lights, fire/crime prevention, safety
equipment, medical systems, servers, solar cells, and power transmission systems.
8) Do not use our Products in applications requiring extremely high reliability, such as aerospaceequipment, nuclear power control systems, and submarine repeaters.
9) ROHM shall have no responsibility for any damages or injury arising from non-compliance withthe recommended usage conditions and specifications contained herein.
10) ROHM has used reasonable care to ensure the accuracy of the information contained in thisdocument. However, ROHM does not warrants that such information is error-free, and ROHM
shall have no responsibility for any damages arising from any inaccuracy or misprint of suchinformation.
11) Please use the Products in accordance with any applicable environmental laws and regulations,such as the RoHS Directive. For more details, including RoHS compatibility, please contact aROHM sales office. ROHM shall have no responsibility for any damages or losses resulting
non-compliance with any applicable laws or regulations.
12) When providing our Products and technologies contained in this document to other countries,
you must abide by the procedures and provisions stipulated in all applicable export laws andregulations, including without limitation the US Export Administration Regulations and the Foreign
Exchange and Foreign Trade Act.
13) This document, in part or in whole, may not be reprinted or reproduced without prior consent ofROHM.

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