JP2012165516A - Control circuit of drive circuit ic and control method of drive circuit ic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a semiconductor switching element from overheat in a state capable of improving drive efficiency of an actuator as much as possible after measuring a temperature closer to an actual junction temperature.SOLUTION: When a guard logic of a CPU supplies control signals to a semiconductor switching element according to each of a plurality of drive patterns and obtains the increase degree of a junction temperature Tj as a deviation ΔTj by a diode built in a DC motor drive IC for states before and after driving a DC motor (S11-S16), threshold temperatures Tset for determining the propriety of the drive of the DC motor are obtained for the respective drive patterns corresponding to the deviation ΔTj, and they are stored in a memory (S17). The junction temperature Tj measured before driving the DC motor and the threshold temperature Tset obtained for the corresponding drive pattern are compared, and when it is predicted to be Tj>Tset, replacement with the drive pattern capable of satisfying a condition Tj≤Tset is performed and the DC motor is driven.

Description

  The present invention relates to a control circuit and a control method for controlling a drive circuit IC including one or more semiconductor switching elements for driving an actuator while performing overheat protection.

  For example, in order to drive an injector that injects fuel into an engine or an actuator such as a throttle valve, a semiconductor switching element is frequently controlled by PWM control of a driving circuit (driver) constituted by a semiconductor switching element such as a power MOSFET. Turn on and off. Then, since the drive current flows intermittently through the semiconductor switching element, the semiconductor switching element generates heat. Since the semiconductor switching element is destroyed when the heat is excessive, generally, a measure such as adding an overheat protection function to stop driving of the actuator is taken.

  Specifically, for example, when the ambient temperature Ta of the drive circuit is set in the evaluation environment or the like, the temperature detected by the temperature sensor set for evaluation in the package portion or the like of the drive circuit does not exceed a predetermined threshold value. The actuator is stopped, and when a certain stop time (waiting time) elapses and the heat generation temperature drops, a heat generation destruction guard is set to resume the drive, and the junction temperature Tj of the semiconductor switching element is rated. Exothermic destruction guard control is performed to protect the temperature Tjmax from exceeding. In this case, the junction temperature Tj is not directly measured, and Tj is often estimated from the measured value of the temperature Tc of the package of the drive circuit normally configured as an IC.

  Further, since the heat radiation characteristics change if the mounting state of the drive circuit is different, this becomes a variation factor of the junction temperature Tj. If the power consumption of the actuator changes, the junction temperature Tj naturally varies. As described above, since it is necessary to secure a heat generation margin for various fluctuation factors, the waiting time in the above-described heat generation destruction guard control is often set to be quite redundant. As a result, although the actual junction temperature Tj rarely reaches the rated temperature Tjmax, the actuator is often stopped and waits for a certain period of time. A decrease in efficiency is a problem.

  For example, FIG. 8 shows an example in which a DC motor for an EGR (Exhaust Gas Recirculation) valve is driven and controlled. It is a table which shows the opening-and-closing period set according to it. For example, when the command opening width is 20 deg, it is shown that the state where the junction temperature Tj is lower than the rated temperature Tjmax can be reliably maintained if the opening / closing cycle is 336 ms. However, if the actual usage environment is Ta = 85 ° C., the corresponding table is (b). In this case, if the command opening width is 20 deg, the opening / closing cycle should be 160 ms. However, for the sake of safety, such correspondence is not possible as long as a table created at Ta = 100 ° C. is used. As a result, the responsiveness of the EGR valve and the intake throttle may deteriorate, or the number of fuel injections by the injector may be limited, which may make it impossible to clear the emission regulations required for the engine.

  For example, by using the technique disclosed in Patent Document 1, in an ECU (Electronic Control Unit), a chip is placed in the middle of a path through which heat is transmitted from a mounting position of a circuit element that generates heat according to an energization operation to a microcomputer. It is considered that a thermistor is arranged, the ambient temperature Ta is monitored by a CPU inside the microcomputer, and the table shown in FIGS. 8A and 8B is switched and controlled according to the ambient temperature Ta. For example, when the ambient temperature Ta drops to 80 ° C. in the state using (a), the mode is switched to (b), and when the ambient temperature Ta exceeds 85 ° C. in the state using (b), the mode is switched to (a) again. To control. The reason why the temperature threshold value for switching between (a) and (b) is different between the descending side and the ascending side is to provide hysteresis characteristics.

However, even in this case, the junction temperature Tj cannot be recognized with high accuracy because there is a delay in heat transfer due to the thermal resistance existing between the semiconductor element driving the actuator and the heat generated by other elements. Therefore, optimal control according to the actual environment at the time of drive control is not achieved, and improvement in controllability is limited. For example, as shown in FIG. 9, Ta≈Tj should be obtained before the actuator is driven, and no restriction is imposed until the junction temperature Tj reaches the rated temperature Tjmax. Regarding the width, an opening / closing cycle of 0 ms should be sufficient, but it cannot be understood that the junction temperature Tj is lowered depending on the ambient temperature Ta measured by the technique of Patent Document 1.
Patent Document 2 discloses a technique in which a temperature detection diode is arranged inside an IC to be temperature-measured and the junction temperature Tj is measured based on a change in forward voltage.

JP 2000-45850 A JP 2000-304623 A

For example, although a slight improvement in accuracy can be expected by further applying the technique of Patent Document 2, since the above-described margin must be included in switching and controlling a plurality of tables, the responsiveness is still high. It cannot be fully improved.
The present invention has been made in view of the above circumstances, and its purpose is to measure the temperature closer to the actual junction temperature and to protect the semiconductor switching element from overheating in a state where the drive efficiency of the actuator can be improved as much as possible. It is an object to provide a control circuit for a drive circuit IC and a control method for the drive circuit IC that can be performed.

  According to the control circuit of the drive circuit IC according to claim 1, the temperature deviation calculating means supplies the control signal to the semiconductor switching element according to each of the plurality of control conditions, and the drive circuit IC is in a state before and after driving the actuator. The degree of increase in the junction temperature Tj is obtained as a deviation ΔTj by the built-in temperature measuring element. The threshold temperature calculation means obtains a threshold temperature Tset for determining whether or not the actuator can be driven according to the deviation ΔTj for each control condition, and stores them in the storage means. Then, the control means compares the temperature Tj measured before driving the actuator with the threshold temperature Tset obtained for the corresponding control condition, and when Tj> Tset is predicted, the condition Tj ≦ T The actuator is driven instead of the control condition that can satisfy Tset.

  In other words, the junction temperature Tj of the semiconductor switching element can be measured more accurately by the temperature measuring element incorporated in the drive circuit IC. Then, the threshold temperature Tset is set according to the deviation ΔT of the temperature Tj when the actuator is driven under each control condition. When the actuator is actually driven, whether or not the drive can be performed according to the threshold temperature Tset according to the control condition. Is determined in real time. Therefore, the threshold temperature Tset can be determined in a state very close to the actual driving environment, so that the driving efficiency of the actuator can be improved as compared with the conventional one while protecting the driving circuit IC from overheating.

  According to the control circuit of the drive circuit IC according to claim 2, when it is predicted that Tj> Tset, the control means gives the semiconductor switching element so that the condition Tj ≦ Tset can be satisfied. Change the control signal pattern. As a result, if the actuator is continuously driven according to the current control conditions, it is possible to continue driving the actuator while avoiding a decrease in efficiency as much as possible even when an overheating state is assumed.

  According to the control circuit of the drive circuit IC according to claim 3, when it is predicted that Tj> Tset, the control unit stops driving the actuator so that the condition Tj ≦ Tset can be satisfied. Extend the waiting time from the start to restart. As a result, if the actuator is continuously driven according to the current control conditions, the actuator can be resumed after a necessary minimum waiting time even if it is assumed that an overheating state is reached.

  According to the control circuit of the drive circuit IC according to the fourth aspect, the threshold temperature calculating means determines the threshold temperature Tset based on the threshold temperature previously determined for the same control condition and the temperature deviation ΔTj. That is, by determining the current threshold temperature Tset using the threshold temperature obtained in the past, it is possible to avoid occurrence of variations in the threshold temperature Tset when the temperature ΔTj changes instantaneously.

According to the control circuit of the drive circuit IC according to claim 5, the threshold temperature calculation means sets the control condition as A and sets the threshold temperature Tset (A, n) to be obtained for the nth time as a deviation of the temperature obtained for the nth time. Is ΔTj (A, n) and the rated temperature is Tjmax.
Tset (A, n) = [Tset (A, n−1) + {Tjmax−ΔTj (A, n)}] / 2
Ask for. That is, the difference between the rated temperature Tjmax and the deviation ΔTj (A, n) obtained at the nth time is added to the threshold temperature Tset (A, n-1) obtained at the (n-1) th time, and the average of both is obtained. Take. That is, the second term on the right side indicates a margin temperature until the temperature increase ΔTj (A, n) when driven by the drive pattern A reaches the rated temperature Tjmax. By adding the marginal temperature and the previous learning result threshold temperature Tset (A, n−1) and taking the average, it is possible to suppress the occurrence of variations in the execution results up to n times, thereby increasing the threshold temperature. Tset (A, n) can be set to a reasonable value.

The flowchart which is one Example and shows the processing content by the guard logic of CPU Flow chart showing processing contents of learning logic A diagram showing graphs corresponding to two drive patterns A and B, with the junction temperature Tj on the horizontal axis and the waiting time t_set on the vertical axis. A diagram showing a map of the graph of FIG. Fig. 3 shows a three-dimensional graph FIG. 4 equivalent view of FIG. Functional block diagram showing the DC motor drive system Diagram for explaining the prior art (part 1) Diagram for explaining the prior art (2)

  Hereinafter, an embodiment will be described with reference to FIGS. FIG. 7 is a functional block diagram showing a DC motor drive system. The DC motor (actuator) 1 is driven and controlled via a DC motor drive IC (drive circuit IC) 3 by a PWM signal supplied from a CPU (microcomputer or ECU (Electronic Control Unit), control circuit, control means) 2. Is done. The DC motor drive IC 3 constitutes an H-bridge type drive circuit composed of, for example, four power MOSFETs (semiconductor switching elements), and the (+) terminal and the (−) terminal of the DC motor 1 have two sets. Connected between the arms. Note that the driving circuit is not limited to the H-bridge driving circuit, and may be a high-side driving circuit or a low-side driving circuit.

Also, a diode 4 is built in the DC motor driving IC 3 as a temperature detecting element for measuring the junction temperature Tj of the power MOSFET. The anode of the diode 4 is pulled up to the power supply VCC via the resistance element 5, and is connected to the input terminal of the CPU 2, and the cathode is connected to the ground. The forward voltage Vf of the diode 4 has a negative temperature characteristic of about −2 mV / ° C., for example. Therefore, the CPU 2 can detect the internal temperature of the DC motor driving IC 3, that is, the junction temperature Tj of the power MOSFET, by A / D converting and reading the anode potential of the diode 4.
In order to obtain a larger voltage change with respect to temperature fluctuations, a plurality of diodes 4 may be connected in series. If a constant current source is arranged instead of the resistance element 5, it is possible to prevent a decrease in detection accuracy due to a change in anode potential. Further, the anode potential may be output to the CPU 2 via a voltage buffer or an amplifier circuit.

  The CPU 2 includes a DC motor operation guard logic 6 (hereinafter simply referred to as guard logic) as a function realized by the control program. As described above, the guard logic 6 performs A / D conversion on the anode potential of the diode 4 and performs arithmetic processing, and outputs a PWM signal (+) / (−) to the DC motor driving IC 3. In the case of the H bridge type, the PWM signal is actually output to each of the four elements.

  Next, the operation of this embodiment will be described with reference to FIGS. FIG. 1 is a flowchart showing the contents of processing by the guard logic (control means) 6, and FIG. 2 is learning logic (temperature deviation calculation means, threshold temperature calculation means) executed in parallel during the processing shown in FIG. It is a flowchart which shows the processing content of 6s part. In FIG. 1, first, it is determined whether or not there is a drive command for the DC motor 1 given to the CPU 2 from the upper side of the system (step S1).

  Here, it is assumed whether or not it is the drive command issued for the nth time for a specific drive pattern (control condition) A (for example, a command for setting the valve opening (difference) to 50 deg). .. Are divided according to the drive patterns A, B, C,..., And the same processing is performed for each drive pattern. In step S1, if the drive command for drive pattern A is not given (NO), the current valve opening degree is maintained and the drive command is waited (step S9), and the process returns to step S1.

  When the n-th drive command of the drive pattern A is issued (step S1: YES), the guard logic 6 performs A / D conversion and reads the anode voltage of the diode 4 and monitors the junction temperature Tj (step S2). Then, learning of the threshold temperature Tset (A, n) is started (step S3). Then, the learning logic 6s shown in FIG. 2 starts to operate, and thereafter, the learning logic 6s operates in parallel with the guard logic 6.

  Reference is now made to FIG. The learning logic 6s stores the junction temperature Tj monitored in step S2, that is, the junction temperature Tj before the DC motor 1 is driven n times in the drive pattern A as Tj (A, n, 0) as a memory (storage means, (Step S11). Then, when the driving pattern A is output to drive the DC motor 1 (step S12), the driving temperature A waits for t seconds (step S13) where the junction temperature Tj is expected to rise and reach a peak.

When the junction temperature Tj is monitored again (step S14), it is stored in the memory as the temperature Tj (A, n, t) after being driven by the drive pattern A (step S15). Next, the increase in the junction temperature Tj due to the driving by the nth driving pattern A is obtained by the difference between Tj (A, n, t) and Tj (A, n, 0), and the deviation ΔTj (A, n ) (Step S16, temperature deviation calculating means), the threshold temperature Tset (A, n), which is the current learning result, is obtained by equation (1) (step S17, threshold temperature calculating means).
Tset (A, n) = [Tset (A, n−1) + {Tjmax−ΔTj (A, n)}] / 2
... (1)
That is, the difference between the rated temperature Tjmax and the deviation ΔTj (A, n) obtained this time is added to the threshold temperature Tset (A, n−1) obtained as the previous learning result, and the average of both is obtained. The second term on the right side indicates a margin temperature until the temperature increase ΔTj (A, n) when driven by the drive pattern A reaches the rated temperature Tjmax. By adding the marginal temperature and the previous learning result threshold temperature Tset (A, n−1) and taking the average, it is possible to suppress the occurrence of variations in the execution results up to n times, thereby increasing the threshold temperature. Tset (A, n) can be set to a reasonable value. The threshold temperature Tset (A, n), which is the current learning result, is used at the time of the (n + 1) th driving by the next driving pattern A.

  Here, FIG. 1 will be referred to again. Learning of the threshold temperature Tset (A, n) started in step S2 is executed by the process as described above. Meanwhile, in step S4, the guard logic 6 determines the junction temperature Tj monitored in step S2 and the previous time. The threshold temperature Tset (A, n-1) obtained as a learning result is compared. If {Tj ≦ Tset (A, n−1)} (YES), there is no thermal problem even if the DC motor 1 is driven by the drive pattern A, so the drive is driven by the drive pattern A (step S5). At this point, since learning logic 6s executes steps S12 to S17, learning of threshold temperature Tset (A, n) is stopped (completed).

  On the other hand, if {Tj> Tset (A, n-1)} in step S4 (NO), whether or not to wait until {Tj≤Tset (A, n-1)} is set based on the setting by the user. (Step S6). If the setting by the user is “wait” (YES), the process waits without outputting the drive pattern A until {Tj ≦ Tset (A, n−1)} (guard by waiting time, step S7). That is, when the DC motor 1 is driven in accordance with a given command, the junction temperature Tj is likely to reach the rated temperature Tjmax. Therefore, the standby is performed until the junction temperature Tj falls below the threshold temperature Tset (A, n-1). To promote heat dissipation.

  On the other hand, if the setting by the user is “do not wait” in step S6 (NO), the DC motor 1 is driven with the drive pattern X that satisfies {Tj ≦ Tset (X, N)} (step S8). That is, even if the DC motor 1 is driven, the driving pattern X is driven so that the junction temperature Tj does not reach the rated temperature Tjmax. In this case, the learning logic 6s switches to perform learning for the threshold temperature Tset (X, N), and executes steps S12 to S17. In the above, the processing of steps S5 to S9 corresponds to the control means.

  Next, the processing of steps S5, S7, and S8 will be described with reference to FIGS. In FIG. 3, the horizontal axis represents the junction temperature Tj, and the vertical axis represents “waiting time” t_set in step S7, which corresponds to two drive patterns A and B (B is a command for setting the opening, for example, 10 degrees). The graph is shown. That is, this is a graph showing the waiting time t_set set for each of the drive patterns A and B when the junction temperature Tj takes a certain value. The portion {≦ Tset (A, n), ≦ Tset (B, n)} where the graph is flat is a waiting time t_set = 0, which is an area that can be driven without waiting time (step S5). A portion forming a straight line is an area for setting the waiting time t_set to a predetermined value (step S7). The slope of the straight line portion of the graph is automatically set according to the real-time heat dissipation capability of the drive element. In the driving pattern A, the graph rises at a lower junction temperature Tj.

  Here, when the junction temperature Tj is Tj_now, if it is the drive pattern A, it is necessary to set the waiting time t_set (Tj_now, A) in step S7. On the other hand, if the driving pattern is B, the waiting time t_set (Tj_now, B) = 0, so that it is possible to drive without waiting time in step S8. If the graph of FIG. 3 is mapped, a waiting time guard map as shown in FIG. 4 is obtained.

  FIG. 5 shows a three-dimensional graph of FIG. 3 by adding axes indicating a plurality of drive patterns. In the case of the junction temperature Tj1 shown in the figure, the waiting time t_set = 0 in both cases of the drive patterns A and B, and therefore can be executed in step S5. In the case of Tj2 where the junction temperature Tj is higher, the waiting time t_set = 0 for the driving pattern B and can be executed in step S8. However, if the driving pattern A is used, the waiting time t_set (Tj2, A) is required. S7 is executed. If the junction temperature Tj is higher Tj3, the driving pattern B requires the waiting time t_set (Tj3, B), and if the driving pattern A, the waiting time t_set (Tj3, A) is required. In either case, step S7 is executed. FIG. 6 shows a waiting time guard map corresponding to each case of (a) Tj = Tj1, (b) Tj = Tj2, and (c) Tj = Tj3.

  As described above, according to the present embodiment, the guard logic 6 of the CPU 2 applies the control signal to the semiconductor switching element in accordance with each of the plurality of drive patterns to drive the DC motor 1 to the DC motor driving IC 3. When the degree of increase in the junction temperature Tj is obtained as the deviation ΔTj by the built-in diode 4, a threshold temperature Tset for determining whether or not the DC motor 1 can be driven is obtained according to the deviation ΔTj and stored in the memory. Keep it. Then, the junction temperature Tj measured before driving the DC motor 1 is compared with the threshold temperature Tset obtained for the corresponding drive pattern, and if it is predicted that Tj> Tset, the condition Tj ≦ Tset The DC motor 1 is driven instead of the drive pattern that can satisfy the above.

  That is, the junction temperature Tj can be measured more accurately by the diode 4 built in the DC motor driving IC 3. Then, the threshold temperature Tset is set according to the deviation ΔT of the temperature Tj when the DC motor driving IC 3 is driven with each driving pattern. When the DC motor driving IC 3 is driven, the threshold temperature Tset according to the driving pattern is set. Whether or not the drive is possible is determined in real time. Therefore, since the threshold temperature Tset can be determined in a state very close to the actual driving environment, the driving efficiency can be improved as compared with the conventional one while the overheating protection of the DC motor driving IC 3 is performed.

  When it is predicted that Tj> Tset, the drive pattern applied to the semiconductor switching element is changed so that the condition Tj ≦ Tset can be satisfied. As a result, even if it is assumed that if the DC motor driving IC 3 is continuously driven according to the current driving pattern, an overheating state is assumed, it is possible to continue to drive the DC motor driving IC 3 while avoiding a decrease in efficiency as much as possible. Become.

  In addition, when it is predicted that Tj> Tset, the waiting time from when the driving of the DC motor driving IC 3 is stopped to when it resumes is extended so that the condition Tj ≦ Tset can be satisfied. Even when it is assumed that an overheat state is reached as described above, the driving of the DC motor driving IC 3 can be resumed after a necessary minimum waiting time.

  Further, the threshold temperature Tset (n) is obtained based on the threshold temperature Tset (n−1) and the temperature deviation ΔTj (n) obtained before that for the same drive pattern. That is, by determining the current threshold temperature Tset (n) using the threshold temperature Tset (n−1) obtained in the past, the threshold temperature Tset (n) when the temperature ΔTj changes instantaneously. ) Can be avoided. In this case, since the threshold temperature Tset (A, n) is obtained by the equation (1), the threshold temperature Tset (A, n) is set to an appropriate value by suppressing occurrence of variations in the execution results up to n times. Can be set.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or expansions are possible.
The temperature detecting element is not limited to the diode 4 and may be any element that can be disposed inside the drive circuit IC.
The semiconductor switching element is not limited to a power MOSFET, and may be a power transistor, an IGBT, or the like.
The threshold temperature Tset (A, n) is not limited to that obtained by the equation (1). For example, the current deviation ΔTj (n) is added to or subtracted from the previous result Tset (A, n−1). You may ask.
Only one of steps S7 and S8 may be executed.
The load is not limited to the DC motor 1, and any actuator may be used as long as it is driven by energizing the semiconductor switching element. Also, the present invention is not limited to driving an engine throttle or valve.

  In the drawings, 1 is a DC motor (actuator), 2 is a CPU (control circuit, control means), 3 is a DC motor drive IC (drive circuit IC), 4 is a diode (temperature detection element), and 6 is a DC motor operation guard. Logic (control means), 6s indicates learning logic (temperature deviation calculation means, threshold temperature calculation means).

Claims (10)

One or more semiconductor switching elements for driving the actuator are built in, a temperature measuring element is built in, and an output signal of the temperature measuring element is monitored to detect a junction temperature Tj ( Hereinafter, in a control circuit that controls a drive circuit IC configured to be able to estimate a temperature Tj),
In accordance with each of a plurality of control conditions, a temperature deviation calculating means for obtaining a deviation ΔTj of the temperature Tj with respect to a state before and after driving the actuator by giving a control signal to the semiconductor switching element;
A threshold temperature calculating means for obtaining a threshold temperature Tset for determining whether or not the actuator can be driven according to the deviation ΔTj for each of the control conditions, and storing them in a storage means;
Comparing the temperature Tj measured before driving the actuator with the threshold temperature Tset determined for the corresponding control condition;
When it is predicted that Tj> Tset, the control circuit of the drive circuit IC includes control means for driving the actuator in place of a control condition that can satisfy the condition Tj ≦ Tset .   When the control means is predicted to satisfy Tj> Tset, the control means changes a pattern of a control signal applied to the semiconductor switching element so that the condition Tj ≦ Tset can be satisfied. Item 5. A control circuit of the drive circuit IC according to Item 1.   When it is predicted that Tj> Tset, the control means extends the waiting time until the actuator is stopped and restarted so that the condition Tj ≦ Tset can be satisfied. The control circuit of the drive circuit IC according to claim 1.   4. The threshold temperature calculating means determines the threshold temperature Tset based on a threshold temperature previously determined for the same control condition and a deviation ΔTj of the temperature. A control circuit of the drive circuit IC described in 1. The threshold temperature calculation means sets the control condition as A, sets the threshold temperature Tset to be obtained at the nth time as Tset (A, n), sets the temperature deviation obtained at the nth time as ΔTj (A, n), and sets the rated temperature as Assuming Tjmax, the threshold temperature Tset (A, n) is
Tset (A, n) = [Tset (A, n−1) + {Tjmax−ΔTj (A, n)}] / 2
5. The control circuit of the drive circuit IC according to claim 4, wherein One or more semiconductor switching elements for driving the actuator are built in, a temperature measuring element is built in, and an output signal of the temperature measuring element is monitored to detect a junction temperature Tj ( Hereinafter, in a method of controlling a drive circuit IC configured to be able to estimate a temperature Tj),
In accordance with each of a plurality of control conditions, a control signal is given to the semiconductor switching element to determine a deviation ΔTj of the temperature Tj with respect to a state before and after driving the actuator,
A threshold temperature Tset for determining whether or not the actuator can be driven according to the deviation ΔTj is obtained for each control condition, and stored in a storage unit.
Comparing the temperature Tj measured before driving the actuator with the threshold temperature Tset determined for the corresponding control condition;
When it is predicted that Tj> Tset, the control method for the drive circuit IC is characterized in that the actuator is driven instead of a control condition that can satisfy the condition Tj ≦ Tset.   7. The drive according to claim 6, wherein when Tj> Tset is predicted, the pattern of the control signal applied to the semiconductor switching element is changed so that the condition Tj ≦ Tset can be satisfied. Control method of circuit IC.   When it is predicted that Tj> Tset, the waiting time from when the drive of the actuator is stopped to when it is restarted is extended so that the condition Tj ≦ Tset can be satisfied. Item 7. A driving circuit IC control method according to Item 6.   9. The drive circuit IC according to claim 6, wherein the threshold temperature Tset is obtained based on a threshold temperature previously obtained for the same control condition and a deviation ΔTj of the temperature. Control method. Assuming that the control condition is A, the threshold temperature Tset obtained at the n-th time is Tset (A, n), the temperature deviation obtained at the n-th time is ΔTj (A, n), and the rated temperature is Tjmax, the threshold temperature Tset (A, n)
Tset (A, n) = [Tset (A, n−1) + {Tjmax−ΔTj (A, n)}] / 2
10. The method of controlling a drive circuit IC according to claim 9, wherein

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