Semiconductor Devices

Abstract

To accurately calculate temperature of an element constituting a semiconductor device to protect the element from overheating.SOLUTION: A control unit Cnt of an inverter 1 calculates a limited current so that estimated element temperature does not exceed predetermined temperature by calculating a counter value acquired in a predetermined time from a parameter affecting heat generation of switching elements Q1 to Q6 and adding it to a counter value obtained from results of temperature sensors Ts1 and TS2. As a parameter, there are provided an element temperature variable X(n) corresponding to temperature of the switching elements Q1 to Q6 themselves, and a simulated temperature variable ΔY(n) for simulating temperature rise of a portion having a large thermal capacity that is connected to the switching elements Q1 to Q6 for heat transfer. The control unit Cnt calculates a counter upper limit value Z_limit(n) from a current value detected by current detection units Si1 and Si2 based on the element temperature variable X (n) and the simulated temperature variable ΔY (n).SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device. [Background technology]

[0002] The elements that make up a semiconductor device are easily affected by temperature. For example, semiconductor devices used to control the rotation of drive motors in industrial vehicles such as forklifts require high output. In addition, while the drive motor is generally stopped during loading and unloading, it rotates at a relatively high speed while the vehicle is traveling, resulting in large fluctuations in output over time. As a result, the heat generation of the elements that make up the semiconductor device fluctuates frequently.

[0003] Therefore, the temperature of the elements constituting the semiconductor device is measured by a temperature sensor or the like, and the elements are protected from overheating based on the measured temperature.

[0004] For example, a technology has been proposed for an inverter device that executes a predetermined protective operation when the junction temperature of a power semiconductor element for each PWM carrier period estimated by a temperature estimation calculation unit exceeds a predetermined value (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-46647 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to protect the elements that make up the semiconductor device from overheating, it is possible to accurately measure the temperature of the elements that are the target of overheating protection by arranging multiple temperature sensors that measure the temperature of the elements that make up the semiconductor device, or by placing a temperature sensor in an ideal location, such as near the element to be measured.

[0007] However, increasing the number of temperature sensors can improve the accuracy of temperature measurement to some extent, but it also leads to increased costs. Furthermore, due to limitations on product layout, such as the configuration of the semiconductor device, it may not be possible to place the temperature sensors in ideal locations, making it impossible to accurately measure the temperature of the element. Due to limitations on the number of temperature sensors and layout, the element temperature may differ from the temperature sensor value, making it difficult to determine the actual state of the element temperature. As a result, the accuracy of temperature measurement may decrease, and overheating protection of the element may not be adequately performed.

[0008] An object according to one aspect of the present invention is to accurately calculate the temperature of elements constituting a semiconductor device and protect the elements from overheating. [Means for solving the problem]

[0009] One aspect of the present invention is a semiconductor device comprising an element constituting the semiconductor device, temperature measurement means for measuring the temperature of heat generated by the element, a current detection unit for detecting a current flowing through the element, and a control unit for controlling the element. The control unit calculates a limiting current so that the estimated element temperature does not exceed a predetermined temperature by calculating a counter value acquired at a predetermined time from parameters affecting heat generation of the element and adding the counter value obtained from the temperature measurement means. The parameters include an element temperature variable corresponding to the temperature of the element itself and a simulated temperature variable simulating a temperature rise in a portion of the element that is thermally connected to the element and has a large heat capacity in response to a temperature rise in the element. The control unit has counter increment extraction means for calculating the limiting current based on the element temperature variable and the simulated temperature variable from the current value detected by the current detection unit.

[0010] This allows the control unit to calculate the limiting current based on the current value detected by the current detection unit, a temperature variable corresponding to the temperature of the element itself, and a simulated temperature variable simulating the temperature rise of a portion heat-transferably connected to the element and having a large heat capacity in response to a temperature rise of the element. Therefore, the limiting current can be calculated based on a minimal number of temperature measurement means, taking into account not only the temperature of the element itself but also the response delay due to the temperature difference between the temperature measurement means and the element. This improves the accuracy of temperature measurement while suppressing cost increases. As a result, the temperatures of the elements constituting the semiconductor device can be accurately calculated, and the elements can be protected from overheating.

[0011] The arrangement direction of the elements and the extending direction of a plate of a heat sink that cools the elements may be the same direction, and the temperature measuring means may be disposed on the upstream and downstream sides of the heat sink.

[0012] This allows the elements to be arranged with high density, while suppressing the influence of the values ​​measured by the temperature measuring means.

[0013] The control unit may have a counter upper limit value used to calculate the limit current, and may be capable of setting a margin coefficient corresponding to a margin for temperature rise used in calculating the limit current.

[0014] This makes it possible to easily adjust parameters such as the margin coefficient corresponding to the temperature rise margin when deploying the device in multiple applications, thereby reducing the number of design steps. [Effects of the Invention]

[0015] According to the present invention, the temperature of elements constituting a semiconductor device can be calculated with high accuracy, and the elements can be protected from overheating. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram showing an example of a semiconductor device according to an embodiment of the present invention; [Figure 2]FIG. 2 is a perspective view showing the relationship between a temperature sensor and a switching element. [Figure 3] 10 is a graph showing the relationship between the counter value Z(n) and the current value. [Figure 4] 10 is an example of a flowchart illustrating a process for calculating a limit current. [Figure 5] 10 is an example of a table showing the relationship between variables and currents. [Figure 6] 10 is an example of a table showing the relationship between variables and currents. [Figure 7] 10 is an example of a graph showing the relationship between a counter value Z(n) and a current value. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0018] FIG. 1 is a diagram showing an example of a semiconductor device according to an embodiment of the present invention.

[0019] 1 shows an inverter 1 as the semiconductor device. The inverter 1 includes a control unit Cnt, switching elements Q1 to Q6, temperature sensors Ts1 and Ts2, current detection units Si1 and Si2, and a capacitor C.

[0020] The switching elements Q1 to Q6 are an example of elements that constitute a semiconductor device. MOSFETs (metal-oxide-semiconductor field-effect transistors) are used as the switching elements Q1 to Q6. However, IGBTs (insulated gate bipolar transistors) or the like may also be used as the switching elements. The switching elements Q1 to Q6 include diodes D1 to D6, respectively. The six diodes D1 to D6 are parasitic diodes of the six switching elements (MOSFETs) Q1 to Q6, respectively.

[0021] Between the positive bus bar Lp and the negative bus bar Ln, a switching element Q1 constituting a u-phase upper arm and a switching element Q2 constituting a u-phase lower arm are connected in series. Between the positive bus bar Lp and the negative bus bar Ln, a switching element Q3 constituting a v-phase upper arm and a switching element Q4 constituting a v-phase lower arm are connected in series. Between the positive bus bar Lp and the negative bus bar Ln, a switching element Q5 constituting a w-phase upper arm and a switching element Q6 constituting a w-phase lower arm are connected in series.

[0022] By configuring the inverter 1 using a MOSFET and a parasitic diode of the MOSFET, the semiconductor device can be configured with a simpler structure than when using a mechanical switch or the like, and the semiconductor device can be made smaller.

[0023] The connection point between switching element Q1 and switching element Q2 is connected to the u-phase input terminal of motor M, the connection point between switching element Q3 and switching element Q4 is connected to the v-phase input terminal of motor M, and the connection point between switching element Q5 and switching element Q6 is connected to the w-phase input terminal of motor M.

[0024] With the switching operations of the switching elements Q1 to Q6 that configure the upper and lower arms, the DC power supplied from the power storage device B can be converted into three-phase AC power that is 120 degrees out of phase with each other and supplied to the motor M. The motor M is, for example, a motor for driving a vehicle or a motor for handling cargo.

[0025] A control unit Cnt is connected to the gate terminals of the switching elements Q1 to Q6 of the inverter 1. The control unit Cnt controls the switching elements Q1 to Q6 of the inverter 1 to perform switching operations based on a pulse pattern that is a control signal.

[0026] The current detection unit Si1 is connected to the v-phase input terminal of the motor M and detects the current supplied from the inverter 1 to the motor M through the v-phase. The current detection unit Si2 is connected to the w-phase input terminal of the motor M and detects the current supplied from the inverter 1 to the motor M through the w-phase. The control unit Cnt detects the current supplied from the inverter 1 to the motor M through the u-phase based on the current supplied to the motor M through the v-phase detected by the current detection unit Si1 and the current supplied to the motor M through the w-phase detected by the current detection unit Si2. This allows the control unit Cnt to detect the current supplied from the inverter 1 to the motor M.

[0027] The temperature sensors Ts1 and Ts2 are examples of temperature measurement means. When there is no need to distinguish between the temperature sensors Ts1 and Ts2, they will hereinafter be referred to as the "temperature sensor Ts." The temperature sensor Ts measures the temperatures of elements such as MOSFETs that constitute the inverter 1.

[0028] The temperature sensor Ts may be disposed near the switching elements Q1 to Q6 that constitute the inverter 1 to measure the component temperatures of the switching elements Q1 to Q6, such as MOSFETs, that constitute the inverter 1. Alternatively, the temperature sensor Ts may be disposed directly next to the switching elements Q1 to Q6, such as MOSFETs, to directly measure the temperatures of the switching elements Q1 to Q6. The temperature sensor Ts and the switching elements Q1 to Q6 are heat-conductively connected to each other. A heat-conductive connection refers to a state in which the elements are connected in such a way that heat can be transferred between them through an object or space, and refers to a state in which the heat of the switching elements Q1 to Q6 can be transferred to the temperature sensor Ts by thermal conduction, convection, radiation, etc.

[0029] Fig. 2 is a perspective view showing the relationship between temperature sensors Ts1 and Ts2 and switching element Q1. As shown in Fig. 2, inverter 1 is placed on heat sink Hs. Heat sink Hs is composed of multiple plate-like bodies P extending in the same direction. In this embodiment, the direction in which the plate-like bodies P extend is defined as the upstream and downstream sides of heat sink Hs. Heat sink Hs cools switching elements Q1 to Q6 that constitute inverter 1.

[0030] 2, the temperature sensors Ts1 and Ts2 are arranged in the same direction as the extension direction of the plate-like body P that constitutes the heat sink Hs, and on the upstream and downstream sides of the heat sink Hs (on the end sides in the extension direction of the heat sink Hs). This allows the switching elements Q1 to Q6 to be arranged with high density, and also minimizes the influence of the values ​​obtained by the temperature sensors Ts1 and Ts2 based on the difference between the thermal resistance and heat capacity.

[0031] The control unit Cnt calculates a counter value Z(n) obtained at a predetermined time from parameters that affect the heat generation of the switching elements Q1 to Q6, and adds the calculated value to the counter value obtained from the temperatures obtained from the temperature sensors Ts1 and Ts2. The control unit Cnt indicates an estimated element temperature value of the temperature rise of the switching elements Q1 to Q6 based on the output current. The counter value Z(n) is the amount of temperature rise of the switching elements Q1 to Q6 per count cycle. The counter value Z(n) is obtained at a predetermined time. For example, the estimated value of the temperature of the switching element Q1 is determined by the following equation 1.

[0032] Measured temperature T1 measured by temperature sensor Ts1 + counter value Z(n) = estimated temperature of switching element Q1...Equation 1

[0033] The parameter indicates the effective value of the current detected by the current sensor in the section from current I(n)=t(n-1) to t(n). In the above-mentioned formula 1, the measured temperature T1 measured by the temperature sensor Ts1 is estimated, but this is not limited to this. For example, by substituting the measured temperature T2 measured by the temperature sensor Ts2 instead of the measured temperature T1 measured by the temperature sensor Ts1 in formula 1, the estimated value of the temperature of the switching element can be calculated using the measured temperature T2 measured by the temperature sensor Ts2 in the same way.

[0034] 3 is a graph showing the relationship between the counter value Z(n) and the current value. The counter value on the vertical axis is a value that is proportional to the temperature. The current value is the current flowing through the inverter 1. The current value may be the current flowing through the inverter 1 via the switching elements Q1 to Q6.

[0035] The counter value Z(n) indicates the counter value in the current (n) count cycle, i.e., the nth count cycle. The counter value Z(n-1) indicates the counter value in the previous (n-1) count cycle, i.e., the n-1th count cycle. The counter upper limit value Z_limit(n) indicates the counter threshold value in the nth counter cycle. The counter upper limit value Z_limit(n) is a value used to determine the current that can be calculated in the flowchart showing the process of calculating the limit current described in Figure 4.

[0036] FIG. 4 is an example of a flowchart showing a process for calculating the limit current. When calculating the limit current, the control unit Cnt functions as a counter increment extraction unit. In this case, the control unit Cnt calculates the limit current from the current value detected by the current detection units Si1 and Si2, based on the temperature variable X(n) and the simulated temperature variable Y(n). Specifically, the control unit Cnt performs current limitation in the following steps, for example, according to the flowchart of FIG. 4. First, the control unit Cnt calculates a count-up value based on the current that has flowed from the previous time (n-1th time) to the current time (nth time) (step S1). Then, the control unit Cnt calculates the limit current so that the temperature will not exceed the limit from the current time (nth time) to the next time (n+1th time) (step S2).

[0037] The control unit Cnt can continue to calculate the limit current by repeatedly executing the processes of steps S1 and S2. The control unit Cnt can protect the switching elements Q1 to Q6 from overheating by limiting the current based on the calculated limit current.

[0038] Specifically, the control unit Cnt uses the estimated counter value to calculate the current counter value Z(n) according to the following equation 2. Counter value Z(n) = X(n) + Y(n-1) + ΔY(n) Equation 2

[0039] X(n) is a variable (element temperature variable) that simulates the temperature rise in a part with small heat capacity (such as the inside of the element). X(n) is a variable that corresponds to the temperature of the element itself. ΔY(n) is a variable (simulated temperature variable) that simulates the temperature rise of a part with a large heat capacity (such as from the element to the temperature sensor) that is connected to the element through heat transfer and corresponds to the temperature rise of the element. X(n) is calculated from the table shown in Figure 5(1). ΔY(n) is calculated from the table shown in Figure 5(2).

[0040] Figure 5 is an example of a table showing the relationship between variables and current. Current I(n) indicates the effective value of the current detected by current detection units Si1 and Si2 in the section from t(n-1th time) to t(nth time). Y(n-1) indicates the previous (n-1th time) counter value. ΔY(n) indicates the increase in the counter value from the previous (n-1th time) to the current (nth time) counter value.

[0041] Fig. 5(1) is a table showing the relationship between the current I(n) and the variable X(n). For example, when the current I(n) is 400 A, the control unit Cnt refers to the table in Fig. 5(1) and determines the variable X(n) to be 15.

[0042] 5(2) is a table showing the relationship between Y(n-1), current I(n), and variable ΔY(n). For example, when Y(n-1)=5 and current I(n)=400A, the control unit Cnt refers to the table in FIG. 5(2) and determines ΔY(n)="10".

[0043] The control unit Cnt determines the current variable Y(n) according to the following equation 3.

[0044] Y(n)=Y(n-1)+ΔY(n) Equation 3

[0045] The variable Y(n) is a value that simulates the response delay due to the temperature rise in parts with large heat capacity, such as the temperature sensors from the element. Therefore, the variable Y(n) corresponds to the response delay of the temperature sensors Ts1 and Ts2 in response to the temperature rise of the element. The control unit Cnt refers to Equation 3, inputs Y(n-1) = "5" and ΔY(n) = "10", and calculates the variable Y(n) = "15".

[0046] By substituting Equation 3 into Equation 2, Equation 2 can be rewritten, and the counter value Z(n) can be calculated by Equation 2' below.

[0047] Counter value Z(n) = X(n) + Y(n) Equation 2'

[0048] The control unit Cnt inputs the calculated variable X(n)="15" and the calculated variable Y(n)="15" into the above formula 2' to calculate the counter value Z(n). The control unit Cnt calculates the counter value Z(n)=15+15="30".

[0049] Next, the control unit Cnt determines the counter upper limit value Z_limit(n) (limited current) according to the following equation 4.

[0050] Counter upper limit Z_limit(n) = Element rated temperature ET - Sensor temperature T - α Equation 4

[0051] The element rated temperature ET is the rated temperature of the switching elements Q1 to Q6. For example, it is set to 175°C. The sensor temperature T is the substrate temperature measured by the temperature sensor Ts at that time. The coefficient corresponding to the margin (margin coefficient) α is a value corresponding to the margin for temperature rise. The coefficient corresponding to the margin (margin coefficient) α is a value that can be set when used to calculate the limit current. The coefficient corresponding to the margin α includes an expected amount of temperature rise of the temperature sensor Ts until the next time. The coefficient corresponding to the margin α is set to, for example, "10°C".

[0052] The control unit Cnt can easily handle the parameter adjustment of the coefficient α corresponding to the margin. As a result, it becomes possible to reduce the design man-hours.

[0053] The control unit Cnt selects a current upper limit value I_limit(n + 1) that satisfies the following formula 5 such that the counter value at the next (n + 1)-th time is below the threshold value. Based on the selected current upper limit value I_limit(n + 1), the upper limit value of the outputable current can be set.

[0054] X(n + 1) + Y(n) + ΔY(n + 1) < Z_limit(n) ··· Formula 5

[0055] The current upper limit value I_limit(n + 1) is calculated from the table shown in FIG. 6.

[0056] FIG. 6 is an example of a table showing the relationship between variables and current. It shows the effective value of the current with I = X’(n + 1)-th time. The variable Y(n) represents the counter value at the current (n-th) time. The variable ΔY’(n + 1) represents the increase amount of the counter value at the next (n + 1)-th time.

[0057] FIG. 6(1) is a table showing the relationship between the current I and the variable X’(n + 1). FIG. 6(2) is a table showing the relationship between the current I(n), the variable ΔY(n), and the variable ΔY’(n + 1). The control unit Cnt selects a current upper limit value I_limit(n + 1) that satisfies the following formula 6 by referring to FIG. 6(1) and FIG. 6(2).

[0058] Z’(n + 1) = X’(n + 1) + Y(n) + ΔY’(n + 1) ··· Formula 6

[0059] When applied to the above formula 6, when the current I = 500 A, Z’(n + 1) = 20 + 15 + 7 = "42", when the current I = 400 A, Z’(n + 1) = 15 + 15 + 5 = "35", when the current I = 300 A, Z’(n + 1) = 10 + 15 + 2 = "27", and when the current I = 200 A, Z’(n + 1) = 5 + 15 + 0 = "20" are respectively calculated.

[0060] Therefore, for example, if Z(n) = "30" and Z_limit(n) = "38", the control unit Cnt selects the current I = "400 A", which is less than or equal to Z_limit(n) = "38", as the current upper limit value I_limit(n+1).

[0061] 7 is an example of a graph showing the relationship between the counter value Z(n) and the current value. When the counter upper limit value Z_limit(n) is set so that the current I is equal to or less than Z_limit, as shown in FIG. 7, if the temperature of the switching elements Q1 to Q6 acquired by the temperature sensor Ts increases, the current limit set by the current upper limit value I_limit(n+1) decreases.

[0062] When the current limit is decreased, the control unit Cnt controls the duty ratios of the switching elements Q1 to Q6 so that the current limit is equal to or less than the current upper limit I_limit(n+1).

[0063] According to the above-described embodiment, the control unit Cnt can calculate the current I(n) based on the variable X(n) corresponding to the temperature of the switching elements Q1 to Q6 themselves and the variable Y(n) corresponding to the response delay of the temperature sensors Ts1 and Ts2 relative to the temperature rise of the switching elements Q1 to Q6. Therefore, the current I(n) can be calculated based on the minimum number of temperature sensors Ts1 and Ts2, taking into account the response delay of the temperature sensors Ts1 and Ts2. This improves the accuracy of temperature measurement while suppressing increases in product costs. As a result, the temperatures of the switching elements Q1 to Q6 constituting the inverter 1 can be calculated with high accuracy, and the switching elements Q1 to Q6 can be protected from overheating.

[0064] Furthermore, the control unit Cnt can easily adjust parameters such as the coefficient α corresponding to the margin, etc. As a result, when the semiconductor device is used for multiple purposes, it is possible to reduce the number of design steps.

[0065] <Variation 1> The temperature sensor Ts may measure the temperature of components (hereinafter also referred to as "component temperature") that constitute the inverter 1. For example, the temperature sensor Ts may measure the component temperature of components that constitute the vehicle, such as the inverter 1 and the control unit Cnt. [Explanation of symbols]

[0066] 1 inverter Medium motor Si1, Si2 current detection section C capacitor Ts, Ts1, Ts2 temperature sensors B Energy storage device Cnt control unit Q1~Q6 switching elements D1~D6 diodes Hs heat sink P plate

Claims

1. an element constituting a semiconductor device; a temperature measuring means disposed in the vicinity of the element for measuring the temperature of the element; a current detection unit that detects a current flowing through the element; a control unit that controls the element at a predetermined count cycle; The control unit First correspondence information representing a correspondence between a value of the element current detected by the current detection unit and a first variable that simulates a temperature rise of the element itself; and retaining second correspondence relationship information representing a correspondence relationship between a combination of the value of the device current and a third variable at a previous processing timing of the count cycle, and a second variable simulating a temperature rise in a region between the device and the temperature measuring means at a current processing timing of the count cycle; The control unit, at the n-th processing timing of the count cycle, acquiring the n-th first variable by referring to the first correspondence information with the n-th value of the device current detected by the current detection unit between the (n-1)-th processing timing and the n-th processing timing; acquiring the n-th second variable by referring to the second correspondence information using a combination of the n-th element current value and the (n-1)-th third variable; calculating an n-th third variable by adding the n-th second variable to the n-1-th third variable; calculating an n-th counter value representing a difference between the temperature measured by the temperature measuring means and the actual temperature of the element by adding an n-th third variable to an n-th first variable; calculating an n-th counter upper limit value based on a value obtained by subtracting the n-th temperature measured by the temperature measuring means from a preset element rated temperature; determining an upper limit value of the (n+1)th element current value within a range in which the sum of the (n+1)th first variable, the (n+1)th third variable, and the (n+1)th second variable does not exceed the (n+1)th counter upper limit value by referring to the first correspondence information and referring to the second correspondence information with the (n)th third variable used in calculating the (n)th counter value; The element is controlled so that the value of the element current does not exceed the upper limit of the value of the (n+1)th element current. The semiconductor device is characterized by the above.

2. The arrangement direction of the elements and the extension direction of the heat sink plate that cools the elements are the same direction, 2. The semiconductor device according to claim 1, wherein the temperature measuring means is disposed on the upstream and downstream sides of the heat sink.

3. The n-th counter upper limit value is calculated based on a value obtained by subtracting the n-th temperature measured by the temperature measuring means and a margin from the element rated temperature.

3. The semiconductor device according to claim 1, wherein the first insulating film is a semiconductor material.

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