IGBT｜Application

IGBT IPM: Protection Functions and Operation Sequences Thermal shutdown（TSD） Function of IGBT IPMs

2024.05.22

Points of this article

・The BM6437x series is provided with a thermal shutdown (TSD) circuit that monitors the LVIC (low side gate driver) temperature; if the T_j of an LVIC chip rises above a specific value, the thermal shutdown circuit is actuated, IGBTs for all phases of the lower arm are turned off, and an FO signal is output.

・If TSD is actuated, the T_j of an IGBT has exceeded the absolute maximum rating of 150°C; hence the IPM must be replaced.

・The value T_j being monitored by this function is a property of an LVIC chip. Because rapid temperature increases of an IGBT chip cannot be followed, the TSD cannot effectively function in the case of a sharp increase in T_j, and so proper caution is required.

table of contents

・Thermal Shutdown（TSD）
・Operation Sequence of Thermal Shutdown Function

Here the third protection function, for thermal shutdown, is explained.

Short circuit current protection（SCP）
Control power supply undervoltage lockout（UVLO）
Thermal shutdown（TSD）
Analog temperature output（VOT）
Fault output （FO）
Control inputs （HINU, HINV, HINW, LINU, LINV, LINW ）

Thermal Shutdown（TSD）

The BM6437x series is provided with a thermal shutdown circuit that monitors the temperature of the LVIC (low side gate driver). If the LVIC temperature rises above a certain temperature, the thermal shutdown circuit is activated, the IGBTs for all phases of the lower arm are turned off, and an FO signal is output.

Item	Symbol	Limit			Unit	Condition
Item	Symbol	Min	Typ	Max	Unit	Condition
TSD trip temperature	T_SDT	115	130	–	℃	LVIC temperature monitored
TSD hysteresis temperature	T_SDHYS	–	20	–	℃	LVIC temperature monitored

Operation Sequence of Thermal Shutdown Function

Below are the operation sequence and timing chart of the thermal shutdown protection function provided in the LVIC. In the explanation of operation, d1 to d7 are the operations at the corresponding points shown in the timing chart.

d1: In normal operation, when the IGBTs are turned on an output current Ic flows.
d2: When the LVIC T_j rises and reaches T_SDT, protection operation begins.
d3: IGBTs shut off for all lower arm phases (regardless of LIN input).
d4: FO output (180 µs (Min)) when TSD=H interval is 180 µs or less. When the TSD=H interval is 180 µs or longer, FO is output (FO=L) until T_j with TSD=H falls to T_SDT -T_SDHYS.
d5: As the LVIC T_j falls, TSD is released at T_SDT -T_SDHYS.
d6: Even on TSD release at LIN=H (dashed line), IGBT is in the off state until the next LIN rising edge (each phase returns to the normal state with LIN input to the phase).
d7: Normal operation. IGBTs are on, and output current Ic flows.

Below is a schematic diagram showing the manner in which heat propagates to the LVIC chip mounted within an IGB IPM. There are two paths along which heat generated by the IGBT chips propagates: conducted along the bonding wire to the LVIC chip, and from the die attach pad to the package rear surface heat dissipating pad, through the heat sink, and returning to the package sealing resin.

※Notice

・When the TSD is activated and a fault output occurs, operation should be halted immediately to avoid an anomalous state.
・When operation is halted due to fault output, if a cause has been an abnormality in the cooling system such as loosening or separation of the heat sink or anomalous stoppage of the cooling fan, there is a strong possibility that these factors have caused the TSD to be activated and the FO signal to be output. In this case, the junction temperature of an IGBT chip has exceeded the 150°C absolute maximum rating, and so the IPM must be replaced.
・The junction temperature that is monitored by this function is the temperature of the lower IGBT gate driver chip (LVIC). Because sudden temperature increases of IGBT chips cannot be followed, this function is not effective with respect to sudden increases in junction temperature during motor locking, overcurrent occurrence, or the like, so proper care should be taken.

【Download Documents】 Basics of IGBTs

IGBTs are one of the typical power devices and are used in a wide range of applications including motor drives. This handbook provides a basic understanding of IGBTs, including their application scope and application picture based on their features, their structure and principle of operation, and how they compare with and use other power devices.

Download

IGBT

Basic

Application

IGBT IPM: Protection Functions and Operation Sequences ＋

Product Information