Current-Sense MOSFET Temperature Measurement via Shared Diode
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Solution Overview
Problem
Existing methods for measuring chip temperature in power conversion devices, such as using a freewheeling diode, are limited in accuracy and cost-effectiveness, especially when applied to general freewheeling diodes on separate chips or MOSFETs with parasitic diodes.
Innovation Solution
A power conversion device configuration that includes an insulated gate type first transistor for main current control, an insulated gate type second transistor formed on the same semiconductor substrate for current detection, and a diode connected between the source electrodes of these transistors. A temperature measurement circuit measures the chip temperature by causing a forward current to flow through the diode when the first transistor is off, without increasing the number of bonding pads or chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensing diode is formed on the semiconductor substrate to measure chip temperature, then temperature measurement capability is improved, but the area of the semiconductor substrate increases and product cost increases
Solution Approach 1:
The patent makes the freewheeling diode serve dual functions: its original function of providing a freewheeling current path and an additional function of temperature sensing. By measuring the forward voltage drop across the diode during freewheeling operation, the system obtains temperature information without requiring dedicated temperature sensing structures, thus avoiding additional substrate area consumption.
Solution Approach 2:
The freewheeling diode inherently possesses temperature-dependent electrical characteristics (forward voltage drop varies with temperature). The patent exploits this self-characteristic to perform temperature measurement, eliminating the need for separate temperature sensing components. The diode essentially measures its own temperature through its inherent electrical properties.
2Measurement precision
If a temperature sensing diode is formed on the semiconductor substrate, then temperature measurement capability is improved, but the manufacturing process becomes complicated and manufacturing cost increases
Solution Approach 1:
The patent makes the freewheeling diode serve dual functions: its original function of providing a freewheeling current path and an additional function of temperature sensing. By measuring the forward voltage drop across the diode during freewheeling operation, the system obtains temperature information without requiring dedicated temperature sensing structures, thus avoiding additional substrate area consumption.
Solution Approach 2:
The freewheeling diode inherently possesses temperature-dependent electrical characteristics (forward voltage drop varies with temperature). The patent exploits this self-characteristic to perform temperature measurement, eliminating the need for separate temperature sensing components. The diode essentially measures its own temperature through its inherent electrical properties.
3Area of stationary object
If a freewheeling diode is used for temperature measurement without additional bonding pads, then chip size increase is suppressed, but measurement accuracy is limited
Solution Approach 1:
The patent implements a feedback mechanism where the measured forward voltage drop of the freewheeling diode is used to determine chip temperature, which then feeds back to compensate for temperature-dependent variations in the current sensing circuit. This closed-loop approach improves overall measurement accuracy by correcting for thermal effects in real-time.
Solution Approach 2:
The patent utilizes the temperature-dependent parameter (forward voltage drop) of the freewheeling diode to infer temperature information. By monitoring changes in this electrical parameter under different temperature conditions, the system achieves temperature measurement without requiring dedicated temperature sensing structures.
4Measurement precision
If current sense element and main control element are separated, then current detection capability is improved, but temperature dependency causes inaccurate main control current calculation
Solution Approach 1:
The patent implements a feedback mechanism where the measured forward voltage drop of the freewheeling diode is used to determine chip temperature, which then feeds back to compensate for temperature-dependent variations in the current sensing circuit. This closed-loop approach improves overall measurement accuracy by correcting for thermal effects in real-time.
Solution Approach 2:
The patent utilizes the temperature-dependent parameter (forward voltage drop) of the freewheeling diode to infer temperature information. By monitoring changes in this electrical parameter under different temperature conditions, the system achieves temperature measurement without requiring dedicated temperature sensing structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for accurate and cost-effective chip temperature measurement in power conversion devices, without increasing the chip cost or size, and is applicable to a wide range of power devices including those with current sense elements.
Implementation Method 1
A temperature measurement circuit measures the chip temperature by causing a forward current to flow through the diode when the first transistor is off
Data Source
Figure 1
Figure 2(a)~2(g)
Figure 3~4
AI summary
Provided is a power conversion device capable of observing a chip temperature with high accuracy without increasing a cost of the power conversion device mounted with a current sense element for observing a main current of a power device. A main control MOSFET 11, a current MOSFET 12, and a diode 13 connected to a. source electrode 8 of the main control MOSFET 11 and a source electrode 9 of the current MOSFET 12 are mounted in a chip of a power device, a temperature measurement circuit 3 is connected to the source electrode 9 of the current MOSFET 12, and when the main control MOSFET 11 is in an off state, a forward current (If) is caused to flow through the diode 13, and an anode potential is observed to measure the chip temperature.