Power supply control device

Abstract

To optimize a limiting current for overcurrent protection.SOLUTION: The power supply control device includes a switching control circuit that is provided in a switching power supply device that converts an input voltage into an output voltage through switching of an output transistor and stabilizes the output voltage by performing switching control of the output transistor based on a feedback voltage corresponding to the output voltage, and a temperature detection circuit that detects a target temperature (TMP) in the power supply control device and outputs a signal indicating a detection result of the target temperature. The switching control circuit can execute an overcurrent protection operation for limiting a current flowing through the output transistor to a limit current (ILIM) or less, and adjusts the limit current in accordance with a target temperature.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a power supply control device. [Background technology]

[0002] Switching power supply devices that generate an output voltage from an input voltage are widely used. A power supply control device (power supply IC) is provided in the switching power supply device to control the operation of the switching power supply device. Patent Document 1 listed below is an example of a document disclosing a power supply control device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 166389

[0004] [overview] The power supply control device generates heat during operation, and proper control is required taking into account the temperature inside the power supply control device.

[0005] A power supply control device according to one aspect of the present disclosure is a power supply control device provided in a switching power supply device configured to convert an input voltage into an output voltage through switching of an output transistor, and includes: a switching control circuit configured to stabilize the output voltage by controlling the switching of the output transistor based on a feedback voltage corresponding to the output voltage; and a temperature detection circuit configured to detect a target temperature within the power supply control device and output a signal indicating the detection result of the target temperature to the switching control circuit, wherein the switching control circuit is configured to be able to perform an overcurrent protection operation to limit the current flowing through the output transistor to a limited current or less, and the switching control circuit adjusts the limited current according to the target temperature. [Brief explanation of the drawings]

[0006] [Figure 1]FIG. 1 is an overall configuration diagram of a power supply device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is an external perspective view of a power supply control device according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a timing chart during a normal operation period according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is an explanatory diagram of an overcurrent protection operation according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a diagram showing the internal configuration of a temperature detection circuit according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a timing chart illustrating the operation of the temperature detection circuit according to the embodiment of the present disclosure. [Figure 7] FIG. 7 is a diagram showing the relationship between the output signal of the temperature detection circuit and the limited current in the overcurrent protection operation according to the embodiment of the present disclosure. [Figure 8] FIG. 8 is a timing chart showing the relationship between the output signal of the temperature detection circuit and the limit current in the overcurrent protection operation according to the embodiment of the present disclosure. [Figure 9] FIG. 9 is a circuit diagram of a protection level setting circuit according to an embodiment of the present disclosure. [Figure 10] FIG. 10 is a reference timing chart for the reference power supply device. [Figure 11] FIG. 11 is a timing chart of the power supply device according to the embodiment of the present disclosure. [Figure 12] FIG. 12 is a block diagram of an internal linear regulator according to an embodiment of the present disclosure. [Figure 13] FIG. 13 is a diagram illustrating the relationship between the output signal of the temperature detection circuit and the upper limit current in the internal linear regulator according to the embodiment of the present disclosure. [Figure 14] FIG. 14 is a partial configuration diagram of a modified power supply device according to a third example belonging to the disclosed embodiments.

[0007] [Detailed explanation] Hereinafter, examples of embodiments of the present disclosure will be described in detail with reference to the drawings. In each of the drawings, the same parts are designated by the same reference numerals, and duplicate descriptions of the same parts will be omitted as a general rule. In this specification, for the sake of simplicity, symbols or signs referring to information, signals, physical quantities, functional units, circuits, elements, or components may be used, and the names of the information, signals, physical quantities, functional units, circuits, elements, or components corresponding to the symbols or signs may be omitted or abbreviated.

[0008] First, some terms used in describing the embodiments of the present disclosure will be explained. Ground refers to a reference conductor having an electric potential of 0 V (zero volts) as a reference, or refers to the 0 V potential itself. The reference conductor may be formed using a conductor such as metal. The 0 V potential is sometimes referred to as ground potential. In the embodiments of the present disclosure, a voltage indicated without a particular reference represents a potential seen from ground.

[0009] A level refers to the level (height) of the electric potential, and for any given signal or voltage, a high level has a higher electric potential than a low level. For any given signal or voltage, a rising edge refers to the transition from a low level to a high level, and a falling edge refers to the transition from a high level to a low level.

[0010] For any transistor configured as a FET (field-effect transistor), such as a MOSFET, the on state refers to a state in which the drain and source of the transistor are conductive, and the off state refers to a state in which the drain and source of the transistor are non-conductive (cut-off state). The same applies to transistors not classified as FETs. Unless otherwise specified, MOSFETs are understood to be enhancement-type MOSFETs. MOSFET is an abbreviation for "metal-oxide-semiconductor field-effect transistor." Additionally, unless otherwise specified, the back gate of any MOSFET can be considered shorted to the source.

[0011] Hereinafter, for any transistor, the on-state and off-state may also be simply expressed as on and off. Also, for any transistor, the period during which the transistor is in the on-state is referred to as the on-period, and the period during which the transistor is in the off-state is referred to as the off-period.

[0012] For any signal having a high-level or low-level signal level, the period during which the level of the signal is high is referred to as the high-level period, and the period during which the level of the signal is low is referred to as the low-level period. The same applies to any voltage having a high-level or low-level voltage level.

[0013] The connection between a plurality of parts forming a circuit, such as any circuit element, wiring, node, etc., may be understood to refer to an electrical connection unless otherwise specified.

[0014] When any two voltages to be compared are voltage v1 and v2, "v1>v2" represents that voltage v1 is higher than voltage v2, "v1<v2" represents that voltage v1 is lower than voltage v2, and "v1=v2" represents that the value of voltage v1 is the same as the value of voltage v2. The same applies to other expressions including physical quantities other than voltage.

[0015] FIG. 1 is an overall configuration diagram of a power supply device 1 according to an embodiment of the present disclosure. The power supply device 1 in FIG. 1 includes a power supply control device 2 that controls the operation of the power supply device 1, and as discrete components provided outside the power supply control device 2, includes a coil L1, an output capacitor C1, and feedback resistors R1 and R2. The load LD shown in FIG. 1 is not a component of the power supply device 1 but is provided outside the power supply device 1.

[0016] Figure 2 shows an external perspective view of the power supply control device 2. The power supply control device 2 is an electronic component (semiconductor device) that includes a semiconductor chip having a semiconductor integrated circuit formed on a semiconductor substrate, a housing CS (package) that houses the semiconductor chip, and a plurality of external terminals that are exposed from the housing CS to the outside of the power supply control device 2. The power supply control device 2 is formed by sealing the semiconductor chip in a housing CS made of resin. Note that the number of external terminals of the power supply control device 2 and the type of housing CS of the power supply control device 2 shown in Figure 2 are merely examples, and can be designed as desired.

[0017] The power supply 1 in FIG. 1 is configured as a step-down switching power supply (DC / DC converter) that generates a desired output voltage Vout from an input voltage Vin supplied from a DC voltage source (not shown). The output voltage Vout is generated at an output terminal OUT. That is, the output terminal OUT is the application terminal (terminal to which the output voltage Vout is applied) of the output voltage Vout. The output voltage Vout is supplied to a load LD connected to the output terminal OUT. Except in a transient state, the input voltage Vin and the output voltage Vout are positive DC voltages, and the output voltage Vout is lower than the input voltage Vin. For example, when the input voltage Vin is 12V, the output voltage Vout can be stabilized at a desired positive voltage value (e.g., 3.3V or 5V) less than 12V by adjusting the resistance values ​​of the feedback resistors R1 and R2. The current supplied from the output terminal OUT to the load LD is referred to as the load current Iout. The load current Iout is the output current of the power supply 1. Note that the power supply 1 may be a switching power supply other than a step-down type, such as a step-up or step-down-boost type.

[0018] 1 shows an input terminal IN, a switch terminal SW, a ground terminal GND, and a feedback terminal FB as some of the external terminals provided on the power supply control device 2. Other external terminals (e.g., a power good terminal, an enable terminal, etc.) may also be provided on the power supply control device 2.

[0019] The external configuration of the power supply control device 2 will now be described. An input voltage Vin is supplied to an input terminal IN from a DC voltage source (not shown) provided external to the power supply control device 2. A coil L1 is connected in series between a switch terminal SW and an output terminal OUT. That is, a first terminal of the coil L1 is connected to the switch terminal SW, and a second terminal of the coil L1 is connected to the output terminal OUT. The output terminal OUT is also connected to ground via an output capacitor C1. That is, a first terminal of the output capacitor C1 is connected to the output terminal OUT, and a second terminal of the output capacitor C1 is connected to ground. Furthermore, the output terminal OUT is connected to a first terminal of a feedback resistor R1, a second terminal of the feedback resistor R1 is connected to a first terminal of a feedback resistor R2, and a second terminal of the feedback resistor R2 is connected to ground. A feedback voltage Vfb is generated at a connection node between the feedback resistors R1 and R2. The connection node between the feedback resistors R1 and R2 is connected to a feedback terminal FB, thereby inputting the feedback voltage Vfb to the feedback terminal FB. The ground terminal GND is connected to ground. A current flowing through the coil L1 is referred to as a coil current IL. The coil current IL flowing from the switch terminal SW to the output terminal OUT has a positive polarity.

[0020] The following describes the internal configuration of the power supply control device 2. The power supply control device 2 includes an output stage circuit MM, a switching control circuit 10, a temperature detection circuit 20, and an internal power supply circuit 30. In addition to these, the power supply control device 2 is provided with circuits that realize various functions (such as an undervoltage protection circuit, an overvoltage protection circuit, and a reverse current protection circuit), but here we will focus on the circuits MM, 10, 20, and 30.

[0021] The output stage circuit MM includes transistors MH and ML. In the configuration example of FIG. 1, the transistors MH and ML are configured by N-channel MOSFETs. The transistors MH and ML are a pair of switching elements connected in series between the input terminal IN and the ground terminal GND (i.e., ground). The transistor MH functions as an output element (output transistor), and the transistor ML functions as a rectifier element (synchronous rectifier transistor). The transistor MH is provided on a higher potential side than the transistor ML. Specifically, the drain of the transistor MH is connected to the input terminal IN, which is the application terminal of the input voltage Vin, and receives the input voltage Vin. The source of the transistor MH and the drain of the transistor ML are commonly connected to the switch terminal SW. The source of the transistor ML is connected to the ground terminal GND (and therefore to ground). However, a resistor for current detection may be inserted between the source of the transistor ML and the ground terminal GND.

[0022] The switching of the output stage circuit MM is controlled by a switching control circuit 10. In the switching control of the output stage circuit MM, the transistors MH and ML are switched so that they are alternately turned on and off. The switching control of the output stage circuit MM causes a square-wave switch voltage Vsw to appear at the switch terminal SW. The coil L1 and the output capacitor C1 form a rectifying and smoothing circuit that rectifies and smoothes the square-wave switch voltage Vsw that appears at the switch terminal SW to generate the output voltage Vout. The feedback resistors R1 and R2 form a feedback voltage generating circuit that divides the output voltage Vout to generate a feedback voltage Vfb that corresponds to the output voltage Vout. The feedback voltage Vfb is proportional to the output voltage Vout, and the feedback voltage Vfb also rises and falls as the output voltage Vout rises and falls.

[0023] Alternatively, the output voltage Vout itself may be used as the feedback voltage Vfb. In either case, the feedback voltage Vfb is a voltage corresponding to the output voltage Vout. The feedback voltage generating circuit (R1, R2) may be provided within the power supply control device 2. In this case, the feedback terminal FB is connected to the output terminal OUT.

[0024] The gates of the transistors MH and ML are supplied with gate signals GH and GL as drive signals from the switching control circuit 10, respectively, and the transistors MH and ML are turned on and off in response to the gate signals GH and GL. When the gate signal GH is at a high level, the transistor MH is on, and when the gate signal GH is at a low level, the transistor MH is off. Similarly, when the gate signal GL is at a high level, the transistor ML is on, and when the gate signal GL is at a low level, the transistor ML is off.

[0025] Basically, the transistors MH and ML are alternately turned on and off, but sometimes both transistors MH and ML are maintained in the off state. That is, the state of the output stage circuit MM is one of an output high state, an output low state, and a both-off state. In the output high state, the transistor MH is on and the transistor ML is off. In the output low state, the transistor MH is off and the transistor ML is on. In the both-off state, both transistors MH and ML are off. The transistors MH and ML are never on at the same time. In the switching control by the switching control circuit 10, alternately turning the transistors M1 and M2 on and off refers to the concept of both-off states being present between the output low state and the output high state, taking into account dead time, etc. Note that at least one of the transistors MH and ML may be provided external to the power supply control device 2. The entire output stage circuit MM may also be provided external to the power supply control device 2 and connected to the power supply control device 2.

[0026] The switching control circuit 10 is connected to the feedback terminal FB and receives a feedback voltage Vfb. Based on the feedback voltage Vfb, the switching control circuit 10 controls the on / off states of the transistors MH and ML by controlling the levels of the gate signals GH and GL, thereby generating a desired output voltage Vout at the output terminal OUT. A reference voltage Vref having a predetermined positive DC voltage value is generated within the power supply control device 2, and the switching control circuit 10 controls the switching of the output stage circuit MM so that the feedback voltage Vfb matches the reference voltage Vref. When the feedback voltage Vfb matches the reference voltage Vref, the output voltage Vout matches a predetermined target voltage Vtg. In other words, based on the feedback voltage Vfb, the switching control circuit 10 controls the switching of the output stage circuit MM so that the output voltage Vout is stabilized at the target voltage Vtg (so as to reduce the difference between the output voltage Vout and the target voltage Vtg).

[0027] FIG. 3 illustrates switching control during normal operation. During normal operation, switching control is performed without the overcurrent protection operation described below. Note that, during light loads (when the load current Iout is considerably small), there may be times when the coil current IL becomes negative, but here we will assume that the power supply device 1 operates in continuous mode, where the coil current IL is always positive. During the period when the output stage circuit MM is in the output high state, the coil current IL flows between the drain and source of the transistor MH. Therefore, the coil current IL during the on period of the transistor MH is equal to the drain current of the transistor MH. During the period when the output stage circuit MM is in the output low state, the coil current IL flows between the drain and source of the transistor ML.

[0028] During the period when the output stage circuit MM is in the output high state (i.e., the on-state of the transistor MH), the coil current IL gradually increases, and during the period when the output stage circuit MM is in the output low state (i.e., the on-state of the transistor ML), the coil current IL gradually decreases.

[0029] The switching control circuit 10 generates a switching control signal Scnt based on the feedback voltage Vref. The switching control circuit 10 may generate the switching control signal Scnt based on the feedback voltage Vref and the coil current IL. Here, it is assumed that the switching control signal Scnt is a single binary signal having a low level or a high level. However, the switching control signal Scnt may be formed by a combination of a set signal and a reset signal, each of which is a binary signal. The switching control signal Scnt alternately has a low level and a high level. The high-level switching control signal Scnt is a signal that commands to set the state of the output stage circuit MM to the output high state, and the low-level switching control signal Scnt is a signal that commands to set the state of the output stage circuit MM to the output low state. During the normal operation period, the switching control circuit 10 performs switching control according to the switching control signal Scnt. For this reason, the switching control circuit 10 according to the normal operation period sets the output stage circuit MM to the output high state by setting the gate signal GH to the high level and the gate signal GL to the low level during the high-level period of the switching control signal Scnt. The switching control circuit 10 according to the normal operation period sets the output stage circuit MM to the output low state by setting the gate signal GH to the low level and the gate signal GL to the high level during the low-level period of the switching control signal Scnt.

[0030] If "Vfb < Vref", the switching control circuit 10 generates the switching control signal Scnt so that the output duty of the output stage circuit MM increases. Conversely, if "Vfb > Vref", the switching control circuit 10 generates the switching control signal Scnt so that the output duty of the output stage circuit MM decreases (for example, adjusts the width of the high-level period or the width of the low-level period of the switching control signal Scnt). Thereby, the error between the feedback voltage Vfb and the reference voltage Vref is kept near zero, and as a result, the output voltage Vout is stabilized at the target voltage Vtg. The output duty of the output stage circuit MM is the ratio of the on-period of the transistor MH to the sum of the on-period and the off-period of the transistor MH.

[0031] Any control method may be used to stabilize the output voltage Vout at the target voltage Vtg. The control method for stabilizing the output voltage Vout at the target voltage Vtg may employ a pulse-width modulation method. When the pulse-width modulation method is employed, the switching frequency of the output stage circuit MM (in other words, the frequency of the switching control signal Scnt) is fixed, and the width of the high-level period of the switching control signal Scnt is adjusted to reduce the error between the feedback voltage Vfb and the reference voltage Vref. The control method for stabilizing the output voltage Vout at the target voltage Vtg may employ a constant-on-time control method. When the constant-on-time control method is employed, the width of the high-level period of the switching control signal Scnt is fixed, and the width of the low-level period of the switching control signal Scnt is adjusted to reduce the error between the feedback voltage Vfb and the reference voltage Vref. The control method for stabilizing the output voltage Vout at the target voltage Vtg may employ a pulse-frequency modulation method.

[0032] The switching control circuit 10 is capable of performing an overcurrent protection operation. The overcurrent protection operation will be explained with reference to FIG. 4. As described above, the coil current IL gradually increases during the period when the output stage circuit MM is in the output high state (i.e., the on-state of the transistor MH), and the coil current IL gradually decreases during the period when the output stage circuit MM is in the output low state (i.e., the on-state of the transistor ML). Due to the overcurrent protection operation, the coil current IL (and therefore the drain current of the transistor MH during the on-state of the transistor MH) is limited to the limited current I LIM The switching control circuit 10 for overcurrent protection detects the magnitude of the coil current IL during the ON period of the transistor MH, and determines whether the coil current IL (and therefore the drain current of the transistor MH) during the ON period of the transistor MH is greater than the limit current I LIM As a signal indicating the monitoring result, the switching control circuit 10 outputs an overcurrent protection signal S OCP Generates a limit current I LIM has a positive current value.

[0033] The coil current IL can be detected by any method. For example, the switching control circuit 10 can detect the coil current IL during the on-period of the transistor MH based on the on-resistance of the transistor MH, which is known to the power supply control device 2, and the drain-source voltage of the transistor MH. Alternatively, the coil current IL can be detected by detecting the current flowing through a replica transistor connected in parallel to the transistor MH during the on-period of the transistor MH. Alternatively, for example, a shunt resistor (not shown) can be connected in series to the transistor MH, and the coil current IL can be detected based on the voltage drop across the shunt resistor.

[0034] Overcurrent protection signal S OCP is a binary signal having a high level or a low level. In principle, the switching control circuit 10 outputs the overcurrent protection signal S OCP is set to low level, and the coil current IL (and therefore the drain current of the transistor MH) is limited to the limit current I LIM When the overcurrent protection signal S OCP is set to high level for a short time. The coil current IL is limited to the current I LIM During this period, the switching control circuit 10 outputs the overcurrent protection signal S OCP The switching control circuit 10 sets the output stage circuit MM to the high output state in response to the rising edge of the switching control signal Scnt, and then sets the overcurrent protection signal S OCP When a rising edge occurs in the switching control signal Scnt, the output stage circuit MM is immediately switched from the output high state to the output low state without waiting for the falling edge of the switching control signal Scnt (i.e., without depending on the switching control signal Scnt). After that, when the next rising edge occurs in the switching control signal Scnt, the switching control circuit 10 sets the output stage circuit MM to the output high state again. By this overcurrent protection operation, the coil current IL (and therefore the drain current of the transistor MH) is limited to the limit current I LIM It is limited to the following:

[0035] The temperature detection circuit 20 detects the temperature at the measurement target position and generates a temperature detection signal Stmp corresponding to the temperature at the measurement target position (detected temperature at the measurement target position). The temperature detection signal Stmp is input to the switching control circuit 10. The temperature at the measurement target position is referred to as the target temperature TMP. The temperature detection circuit 20 is provided with a temperature sensor (not shown) for detecting the target temperature TMP. The temperature sensor is disposed at the measurement target position and, in cooperation with a circuit connected to the temperature sensor, outputs a signal corresponding to the target temperature TMP. For example, the temperature sensor is disposed in a position suitable for measuring the temperature of the transistor MH or ML. In this case, the temperature sensor is disposed in close proximity to the transistor MH or ML. The electrical characteristics of the temperature sensor change according to the target temperature TMP. A silicon diode can be used as the temperature sensor, and the target temperature TMP can be detected using the temperature characteristics of the forward voltage of the diode. Instead of the forward voltage of the diode, the base-emitter voltage of a bipolar transistor may be used to detect the target temperature TMP.

[0036] The internal power supply circuit 30 is connected to the input terminal IN and the ground terminal GND, and generates an internal power supply voltage Vreg based on the input voltage Vin. The internal power supply voltage Vreg is a DC voltage lower than the input voltage Vin. Each circuit in the power supply control device 2 (including the switching control circuit 10 and the temperature detection circuit 20) is driven based on the internal power supply voltage Vreg.

[0037] The gate signal GL is a signal referenced to the ground potential, while the gate signal GH is a signal referenced to the potential of the switch terminal SW. A low-level gate signal GH has the potential of the switch terminal SW, and a high-level gate signal GH is a predetermined voltage higher than the potential of the switch terminal SW. This predetermined voltage is greater than the gate threshold voltage of the transistor MH. A well-known bootstrap circuit (not shown) can be used to generate a boost power supply for generating the gate signal GH. The transistor MH may be configured as a P-channel MOSFET, in which case a boost power supply is not required.

[0038] Alternatively, the power supply 1 may employ a diode rectification system. In this case, instead of the transistor ML, a synchronous rectification diode having an anode connected to the ground terminal GND and a cathode connected to the switch terminal SW is provided in the power supply 1 as a rectifying element. In this case, only the transistor MH is turned on and off in the switching control of the output stage circuit MM. In either case, the input voltage Vin is converted to the output voltage Vout by switching the transistor MH (output transistor) between on and off in the switching control of the output stage circuit MM.

[0039] 5 shows the internal configuration of the temperature detection circuit 20. The temperature detection circuit 20 includes a transistor 21, a constant current source 22, comparators 23 and 24, and a voltage generation circuit 25. The transistor 21 is a PNP bipolar transistor.

[0040] The base and collector of transistor 21 are shorted together and connected to ground. The emitter of transistor 21 is connected to node 26. Constant current source 22 operates based on the internal power supply voltage Vreg and supplies a constant current Icc from the application terminal of the internal power supply voltage Vreg to node 26. The constant current Icc flows to ground through transistor 21. The voltage at node 26 is referred to as voltage Vtmp. Voltage Vtmp is the base-emitter voltage of transistor 21 when constant current Icc flows as the emitter current of transistor 21. Transistor 21 functions as the temperature measuring element described above and is placed at the measurement target position. Therefore, the temperature of transistor 21 is equal to target temperature TMP. Due to the temperature characteristics of transistor 21, as target temperature TMP increases, voltage Vtmp decreases, and as target temperature TMP decreases, voltage Vtmp increases.

[0041] The comparators 23 and 24 operate based on the internal power supply voltage Vreg. Each of the comparators 23 and 24 has an inverting input terminal, a non-inverting input terminal, and an output terminal. The inverting input terminals of the comparators 23 and 24 are connected to a node 26 and receive a voltage Vtmp. The non-inverting input terminal of the comparator 23 receives a voltage Vtmp.PRETSD is supplied to the non-inverting input terminal of the comparator 24, and the voltage V TSD is supplied.

[0042] Comparator 23 converts voltage Vtmp to voltage V PRETSD Compared with the voltages Vtmp and V PRETSD Signal S according to the level relationship of PRETSD The signal S is output from its output terminal. PRETSD is "Vtmp <V PRETSD " has a high level during the period when "Vtmp>V PRETSD " has a low level during the period when "Vtmp=V PRETSD When " is established, the signal S PRETSD has a high level or a low level. The comparator 24 converts the voltage Vtmp into a voltage V TSD Compared with the voltages Vtmp and V TSD Signal S according to the level relationship of TSD The signal S is output from its output terminal. TSD is "Vtmp <V TSD " has a high level during the period when "Vtmp>V TSD " has a low level during the period when "Vtmp=V TSD When " is established, the signal S TSD The temperature detection signal Stmp has a high level or a low level. PRETSD and S TSD and therefore the signal S PRETSD and S TSD is input to the switching control circuit 10. Also, the signal S PRETSD and S TSD is also input to the voltage generating circuit 25.

[0043] The voltage generating circuit 25 operates based on the internal power supply voltage Vreg and outputs a voltage V PRETSD and supplies a voltage V to the non-inverting input terminal of the comparator 24. TSD The voltage generating circuit 25 divides the internal power supply voltage Vreg using a ladder resistor to generate the voltage V PRETSD and V TSDcan be generated. The voltage generation circuit 25 adjusts the voltages V PRETSD and V TSD so that a hysteresis characteristic is imparted in the comparison by the comparators 23 and 24.

[0044] Referring to FIG. 6, the operation of the temperature detection circuit 20 will be described, including the content of the hysteresis characteristic. The voltage generation circuit 25 sets the voltage Va or the voltage (Va + ΔV1) with respect to the voltage V PRETSD . The voltage (Va + ΔV1) is higher than the voltage Va by the voltage ΔV1. The voltage ΔV1 is the hysteresis width imparted in the comparison by the comparator 23 and has a predetermined positive voltage value. The voltage generation circuit 25 sets the voltage Vb or the voltage (Vb + ΔV2) with respect to the voltage V TSD . The voltage (Vb + ΔV2) is higher than the voltage Vb by the voltage ΔV2. The voltage ΔV2 is the hysteresis width imparted in the comparison by the comparator 24 and has a predetermined positive voltage value. The voltage Va is higher than the voltage Vb. In FIG. 6, a state where "Va > Vb + ΔV2" is satisfied is illustrated, but with respect to the voltage Va and the voltage (Vb + ΔV2), any of "Va > Vb + ΔV2", "Va = Vb + ΔV2", and "Va < Vb + ΔV2" may be satisfied. However, in any case, the voltage (Va + ΔV1) is higher than the voltage (Vb + ΔV2). Typically, for example, "Vb < Vb + ΔV2 = Va < Va + ΔV1" may be satisfied.

[0045] The values of the voltages Va, Vb, ΔV1, and ΔV2 are designed such that when the target temperature TMP coincides with the predetermined threshold temperature T PRETSD , the voltage Vtmp coincides with the voltage Va, and when the target temperature TMP coincides with the predetermined threshold temperature T TSD , the voltage Vtmp coincides with the voltage Vb, and when the target temperature TMP coincides with the predetermined threshold temperature (T TSD -ΔT1), the voltage Vtmp coincides with the voltage (Vb + ΔV2), and when the target temperature TMP coincides with the predetermined threshold temperature (T PRETSD -ΔT2), the voltage Vtmp coincides with the voltage (Va + ΔV1).

[0046] The threshold temperature T TSD is the threshold temperature TPRETSD Higher than the threshold temperature (T PRETSD -ΔT2) is the threshold temperature T PRETSD The temperature ΔT2 is a temperature equivalent of the hysteresis width given in the comparison of the comparator 23, and has a predetermined positive value in units of temperature. TSD -ΔT1) is the threshold temperature T TSD The temperature ΔT1 is a temperature equivalent of the hysteresis width applied in the comparison by the comparator 24, and has a predetermined positive value in units of temperature. PRETSD and the threshold temperature (T TSD -ΔT1) and "T PRETSD >T TSD -ΔT1”, “T PRETSD =T TSD -ΔT1” and “T PRETSD <T TSD -ΔT1” can be established. In either case, however, the threshold temperature (T TSD -ΔT1) is the threshold temperature (T PRETSD -ΔT2). Typically, for example, "T PRETSD -ΔT2 <T PRETSD =T TSD -ΔT1 <T TSD ” as a specific numerical example. TSD , T PRETSD can be set to 175° C. and 150° C., respectively, and the temperatures ΔT1 and T2 can be set to 25° C. Of course, the technology according to the present disclosure is not limited to these numerical examples.

[0047] As time progresses, it is assumed that times t0, t1, t2, t3, t4, t5, and t6 occur in this order. It is assumed that the target temperature TMP rises monotonically from time t0 to time t3, and then drops monotonically from time t3 to time t6. At time t0 and before time t0, the power supply control device 2 is in an initial state. The state immediately after the power supply control device 2 is started can be considered to be the initial state. In the initial state, the voltage generation circuit 25 generates a voltage V PRETSD Set the voltage Va for the voltage V TSD In the initial state, the target temperature TMP is set to the threshold temperature (T PRETSD-ΔT2), lower than that. In the initial state, "Vtmp > Va = V PRETSD " and "Vtmp > Vb = V TSD " hold, so the signals S PRETSD and S TSD both have low levels.

[0048] During the rising process of the target temperature TMP between times t0 and t3, at time t1 as the boundary, the state changes from "TMP < T PRETSD " holding to "TMP > T PRETSD " holding. Therefore, by switching the state of "Vtmp > Va" to "Vtmp < Va" at time t1 as the boundary, a rising edge occurs in the signal S PRETSD at time t1. The voltage generation circuit 25 switches the voltage V PRETSD from voltage Va to voltage (Va + ΔV1) in response to the rising edge of the signal S PRETSD at time t1.

[0049] After that, as the target temperature TMP further rises, at time t2 as the boundary, the state changes from "TMP < T TSD " holding to "TMP > T TSD " holding. Therefore, by switching the state of "Vtmp > Vb" to "Vtmp < Vb" at time t2 as the boundary, a rising edge occurs in the signal S TSD at time t2. The voltage generation circuit 25 switches the voltage V TSD from voltage Vb to voltage (Vb + ΔV2) in response to the rising edge of the signal S TSD at time t2. After that, at time t3 as the boundary, the change direction of the temperature TMP reverses from the rising direction to the falling direction.

[0050] During the falling process of the target temperature TMP between times t3 and t6, at time t4 as the boundary, the state changes from "TMP > T TSD -ΔT1" holding to "TMP < T TSD -ΔT1" holding. Therefore, by switching the state of "Vtmp < Vb + ΔV2" to "Vtmp > Vb + ΔV2" at time t4 as the boundary, at time t4, the signal S TSDA falling edge occurs in signal S at time t4. The voltage generation circuit 25 switches the voltage V TSD from the voltage (Vb + ΔV2) to the voltage Vb in response to the falling edge of signal S TSD at time t4.

[0051] Subsequently, as the target temperature TMP further decreases, at time t5, the state switches from the state where "TMP > T PRETSD -ΔT2" holds to the state where "TMP < T PRETSD -ΔT2" holds. Therefore, by switching from the state where "Vtmp < Va + ΔV1" holds to the state where "Vtmp > Va + ΔV1" holds at time t5, a falling edge occurs in signal S PRETSD at time t5. The voltage generation circuit 25 switches the voltage V PRETSD from the voltage (Va + ΔV1) to the voltage Va in response to the falling edge of signal S PRETSD at time t5.

[0052] During the rising process of the target temperature TMP between times t0 and t3, the output signals (S PRETSD and S TSD ) from the temperature detection circuit 20 to the switching control circuit 10 show the high - low relationship between the target temperature TMP and the threshold temperature T PRETSD , and the high - low relationship between the target temperature TMP and the threshold temperature T TSD . During the falling process of the target temperature TMP between times t3 and t6, the output signals (S PRETSD and S TSD ) from the temperature detection circuit 20 to the switching control circuit 10 show the high - low relationship between the target temperature TMP and the threshold temperature (T TSD -ΔT1), and the high - low relationship between the target temperature TMP and the threshold temperature (T PRETSD -ΔT2).

[0053] When a rising edge occurs in signal S PRETSD starting from the initial state, the state where signal S PRETSD has a high level and signal S TSD has a low level means that the target temperature TMP is higher than the threshold temperature T PRETSD and higher than the threshold temperature T TSDThis corresponds to the first temperature state, which is lower than the first temperature state. TSD When the rising target temperature TMP reaches the threshold temperature T TSD This signal indicates that the TSD After switching to high level, the signal S PRETSD and S TSD and are both at a high level when the target temperature TMP is below the threshold temperature T TSD After rising above the threshold temperature (T TSD This corresponds to the second temperature state where the temperature is kept higher than the reference temperature (-ΔT1). TSD When the target temperature TMP is lower than the threshold temperature (T TSD -ΔT1) is detected. TSD is switched to a low level, followed by the signal S PRETSD When the target temperature TMP is lower than the threshold temperature (T PRETSD -ΔT2).

[0054] The switching control circuit 10 outputs a signal S TSD is at a high level, a thermal shutdown operation (hereinafter referred to as a TSD operation) is performed. In the TSD operation, the switching control circuit 10 stops the switching control of the output stage circuit MM and sets the output stage circuit MM to a double-off state. The main cause of the rise in the target temperature TMP is the switching loss in the output stage circuit MM that accompanies the switching control. Therefore, by stopping the switching control, the target temperature TMP is expected to stop rising and fall, thereby protecting the power supply control device 2. In recent years, there has been a growing demand for a higher input voltage Vin, which tends to lead to increased heat generation.

[0055] Although stopping switching control by TSD operation is important for protecting the power supply control device 2, stopping switching control causes a sudden drop in the output voltage Vout, which can have a negative impact on various downstream circuits (including the load LD) that use the output voltage Vout. For this reason, it is preferable to avoid performing TSD operation as much as possible. After the output voltage Vout drops to 0V, switching control is resumed as the target temperature TMP drops, causing the output voltage Vout to rise, and the resumption of switching control may cause the TSD operation to function again, causing the output voltage Vout to drop to 0V again, and this may be repeated (making the operation of the system including the power supply device 1 unstable). On the other hand, switching loss in the output stage circuit MM becomes particularly large under circumstances in which overcurrent protection operation is activated. For this reason, the limit current I in overcurrent protection operation LIM If the limit current I is set low, the target temperature TMP will not rise as easily and the TSD operation will not occur as easily. LIM Setting the value low all the time leads to a reduction in the current supply capacity of the power supply device 1.

[0056] Considering these circumstances, the switching control circuit 10 limits the current I LIM The switching control circuit 10 adjusts (dynamically changes) the limit current I as the target temperature TMP increases. LIM This will make it less likely that the TSD will stop switching control.

[0057] Figure 7 shows the signal S PRETSD and the limiting current I LIM Specifically, the switching control circuit 10 controls the signal S PRETSD During the low level period of LIM Current value I LIM1 (i.e., limit current I LIM The value of I LIM1 The switching control circuit 10 receives the signal S PRETSD During the high level period of LIM Current value I LIM2 (i.e., limit current I LIMThe value of I LIM2 Here, the current value I LIM2 is the current value I LIM1 For example, the current value I LIM1 is 2A (amperes), and the current value I LIM2 is 1.5A. However, "I LIM2 LIM1 As long as " is true, the current value I LIM1 and I LIM2 is arbitrary. Signal S TSD During the high level period of I, switching control is stopped by the TSD operation, and the limit current I LIM is invalid (not defined).

[0058] In the example shown in FIG. 6, the switching control circuit 10 controls the limit current I LIM In the process of increasing the target temperature TMP, the switching control circuit 10 changes the target temperature TMP to the threshold temperature T PRETSD (for example, 150°C) below which the limit current I LIM Current value I LIM1 (for example, 2A), and the target temperature TMP is set to the threshold temperature T PRETSD Higher than the threshold temperature T TSD (for example, 175°C) LIM Current value I LIM2 (for example, 1.5A), and the target temperature TMP is set to the threshold temperature T TSD When the target temperature TMP reaches the threshold temperature T TSD When the voltage exceeds the threshold, the TSD function stops switching control.

[0059] When the target temperature TMP rises, the target temperature TMP reaches the threshold temperature T TSD After the TSD operation is performed by exceeding the target temperature TMP, the switching control circuit 10 detects whether the target temperature TMP is below the threshold temperature (T TSD -ΔT1), the TSD operation continues to stop switching control. TSD ​When the target temperature TMP becomes lower than the threshold temperature (T −ΔT1), the switching control circuit 10 stops the TSD operation and resumes the switching control of the output stage circuit MM. TSD -ΔT1) is lower than the threshold temperature (T PRETSD -ΔT2), the limiting current I LIM Current value I LIM2 (for example, 1.5A) and the target temperature TMP reaches the threshold temperature (T PRETSD -ΔT2) and the limit current I LIM Current value I LIM1 (e.g., 2A).

[0060] Figure 9 shows the limit current I LIM 1 shows a protection level setting circuit 11, which is a circuit for changing the value of in two stages. The protection level setting circuit 11 is provided in the switching control circuit 10. It may also be understood that the protection level setting circuit 11 is provided outside the switching control circuit 10. The protection level setting circuit 11 includes a constant current source 11a, resistors 11b and 11c, and a transistor 11d. The transistor 11d is an N-channel MOSFET.

[0061] The constant current source 11a operates based on the input voltage Vin, and supplies a constant current from the application terminal of the input voltage Vin to the node 11e. The first terminal of the resistor 11b is connected to the node 11e, and the second terminal of the resistor 11b is connected to the first terminal of the resistor 11c and the drain of the transistor 11d. The second terminal of the resistor 11c and the source of the transistor 11d are connected to the ground. In other words, the transistor 11d is connected in parallel to the resistor 11c. A signal S PRETSD is entered.

[0062] The voltage at node 11e is V OCP Signal S PRETSDDuring the low level period of the transistor 11d, the transistor 11d is off. During the off period of the transistor 11d, the constant current from the constant current source 11a flows to the ground through the resistors 11b and 11c, and the sum of the voltage drops occurring at the resistors 11b and 11c is the voltage V OCP Signal S PRETSD During the high level period of the transistor 11d, the transistor 11d is on. During the on period of the transistor 11d, the constant current from the constant current source 11a flows to the ground through the resistor 11b and the channel of the transistor 11d, and the sum of the voltage drops generated by the resistor 11b and the on resistance of the transistor 11d is the voltage V OCP Here, the on-resistance of the transistor 11d is much smaller than that of the resistor 11c and can be considered to be zero. PRETSD Voltage V during the low level period OCP Compared to signal S PRETSD The voltage V during the high level period OCP is low.

[0063] During the ON period of the transistor MH, the switching control circuit 10 generates a comparative voltage (for example, a voltage (Vin-Vsw)) proportional to the coil current IL as a voltage V OCP Compared with the former voltage, the latter voltage is V OCP When it detects that the current has risen to OCP A rising edge is generated in the overcurrent protection signal S OCP In response to the rising edge of the current I, the output stage circuit MM is switched from the high output state to the low output state by the overcurrent protection operation. LIM1 is signal S PRETSD Voltage V during the low level period OCP The current value I LIM2 is signal S PRETSD The voltage V during the high level period OCP That is, the voltage V OCP The comparison voltage (for example, voltage (Vin-Vsw)) to be compared with is the coil current IL with a current value I LIM1 When the signal S PRETSD Voltage V during the low level period OCP and the coil current IL becomes the current value ILIM2 When the signal S PRETSD The voltage V during the high level period OCP matches.

[0064] Figure 10 shows a reference timing chart for the reference power supply. Unlike power supply 1, the reference power supply has a limited current I LIM The value of is always the current value I LIM1 In the reference timing chart of the reference power supply device, the average value of the coil current IL increases while the output voltage Vout is maintained near the target voltage Vtg, and the target temperature TMP rises accordingly. In the reference timing chart of FIG. 10, the coil current IL is fixed at the limit current I LIM (=I LIM1 ) without the target temperature TMP reaching the threshold temperature T TSD When this voltage reaches 0 V, switching control is stopped and the output voltage Vout drops rapidly to 0 V. The average value of the coil current IL refers to the average value of the coil current IL in each switching period of the output stage circuit MM.

[0065] 11 shows a timing chart of the power supply device 1. In the timing chart of FIG. 11, the average value of the coil current IL increases while the output voltage Vout is maintained near the target voltage Vtg, and the target temperature TMP rises in conjunction with this. As the target temperature TMP rises, PRETSD When the limit current I LIM The value of is the current value I LIM1 to the current value I LIM2 As a result, the overcurrent protection function is activated more easily. In the example of Figure 11, the limit current I LIM The value of is the current value I LIM1 to the current value I LIM2 After that, in each switching period, the inductor current IL (the drain current of the transistor MH during the on-period of the transistor MH) is reduced to the limit current I LIM (=I LIM2), the output stage circuit MM is switched from the high output state to the low output state regardless of the switching control signal Scnt. Therefore, in comparison with the reference timing chart of FIG. 10, the amount of heat generated in the output stage circuit MM decreases, and the target temperature TMP reaches the threshold temperature T TSD As a result, the output voltage Vout does not drop rapidly due to TSD operation.

[0066] However, during the period in which the overcurrent protection operation is repeatedly performed, the output duty of the output stage circuit MM becomes lower than the duty according to the switching control signal Scnt, and the output voltage Vout may become somewhat lower than the target voltage Vtg. If a circuit for monitoring the output voltage Vout is provided in the power supply device 1, it is possible to detect a drop in the output voltage Vout and thereby determine that the temperature of the power supply control device 2 is rising ("TMP>T"). PRETSD The power supply control device 2 may be provided with an output monitoring circuit (not shown) that detects whether the output voltage Vout is normal based on the feedback voltage Vfb, and may also be provided with a power good terminal (not shown) as one of the external terminals. The output monitoring circuit outputs an error signal from the power good terminal that becomes active when the error between the output voltage Vout and the target voltage Vtg based on the feedback voltage Vfb becomes greater than a certain level. A processor or the like connected to the power good terminal receives the active error signal and can recognize that the output voltage Vout is abnormal, and can also detect the possibility that the temperature of the power supply control device 2 is rising ("TMP>T PRETSD " possibility that

[0067] FIG. 12 shows the configuration of the internal linear regulator 31. The internal linear regulator 31 is provided in the internal power supply circuit 30 (see FIG. 1) and generates the internal power supply voltage Vreg by stepping down the input voltage Vin. The internal linear regulator 31 may be an LDP (Low Drop Out) regulator. The internal linear regulator 31 includes a transistor 31a and a gate control circuit 31b. In the configuration example of FIG. 12, the transistor 31a is a P-channel MOSFET. However, an N-channel MOSFET may also be used as the transistor 31a. The transistor 31a is a transistor (insertion transistor) inserted in series between the application terminal of the input voltage Vin and the application terminal of the internal power supply voltage Vreg. Specifically, the source of the transistor 31a is connected to the application terminal of the input voltage Vin and receives the input voltage Vin. The drain of the transistor 31a is connected to the application terminal of the internal power supply voltage Vreg. In other words, the voltage at the drain of the transistor 31a is the internal power supply voltage Vreg.

[0068] The gate control circuit 31b is connected to the source, drain, and gate of the transistor 31a. Based on the internal power supply voltage Vreg (i.e., the voltage at the drain of the transistor 31a), the gate control circuit 31b controls the gate potential of the transistor 31a so that the internal power supply voltage Vreg coincides with a predetermined internal target voltage Vreg_tg. Although not shown, a capacitor is provided between the wiring to which the internal power supply voltage Vreg is applied and ground. Each circuit (including the switching control circuit 10 and the temperature detection circuit 20) that operates based on the internal power supply voltage Vreg draws its own consumption current from the wiring to which the internal power supply voltage Vreg is applied.

[0069] The gate control circuit 31b operates to lower the gate potential of the transistor 31a when "Vreg < Vreg_tg" holds, and to raise the gate potential of the transistor 31a when "Vreg > Vreg_tg" holds. The lowering of the gate potential of the transistor 31a brings about an increase in the internal power supply voltage Vreg through an increase in the drain current of the transistor 31a, and the raising of the gate potential of the transistor 31a brings about a decrease in the internal power supply voltage Vreg through a decrease in the drain current of the transistor 31a. As a result, the internal power supply voltage Vreg is maintained near the internal target voltage Vreg_tg.

[0070] An overcurrent protection function is also provided for the internal linear regulator 31. That is, the gate control circuit 31b can execute a second overcurrent protection operation that limits the drain current of the transistor 31a to the upper limit current I UL described below. The gate control circuit 31b can increase the drain current of the transistor 31a by lowering the gate potential of the transistor 31. However, when the drain current of the transistor 31a increases to the upper limit current I UL even if "Vreg < Vreg_tg", the lowering of the gate potential of the transistor 31 is stopped, thereby limiting the drain current of the transistor 31a to the upper limit current I UL described below.

[0071] It is possible that an input voltage Vin exceeding the input voltage range defined in the specifications of the power supply control device 2 may be supplied to the power supply control device 2. For example, consider a case where the specifications of the power supply control device 2 stipulate that the input voltage Vin must be 48 V or less, but the input voltage Vin is temporarily or steadily set to 60 V. Assuming that the drain current of the transistor 31a is constant, the loss generated by the transistor 31a increases when the input voltage Vin is 60 V compared to when the input voltage Vin is 48 V, and the heat generated by the transistor 31a may exceed the allowable limit. Alternatively, even if the input voltage Vin is within the specified range, there is a concern that the current consumption of a circuit operating based on the internal power supply voltage Vreg may become excessively large for some reason, resulting in the heat generated by the transistor 31a exceeding the allowable limit.

[0072] The gate control circuit 31b can execute a second overcurrent protection operation to prevent the heat generation of the transistor 31a from exceeding the allowable amount. However, the allowable amount of heat generation of the transistor 31a depends on the amount of heat generated by other circuits in the power supply control device 2 and the ambient temperature of the power supply control device 2, which are reflected in the target temperature TMP.

[0073] Taking this into consideration, the gate control circuit 31b controls the upper limit current I UL The gate control circuit 31b adjusts (dynamically changes) the upper limit current I as the target temperature TMP increases. UL It is preferable to decrease the signal S step by step. This prevents the temperature of the internal linear regulator 31 (particularly the transistor 31a) from becoming excessively high, thereby protecting the internal linear regulator 31 and the power limiting device 2. Specifically, the signal S PRETSD is supplied to the gate control circuit 31b, and the signal S PRETSD Depending on the upper limit current I UL is variably set.

[0074] Figure 13 shows the signal S PRETSD and upper limit current I UL The gate control circuit 31b controls the signal S PRETSD During the low level period, the upper limit current IUL Current value I UL1 (i.e., upper limit current I UL The value of I UL1 The gate control circuit 31b receives the signal S PRETSD During the high level period, the upper limit current I UL Current value I UL2 (i.e., upper limit current I UL The value of I UL2 Here, the current value I UL2 is the current value I UL1 For example, the current value I UL1 is 0.1A (ampere), and the current value I UL2 is 0.07A. However, "I UL2 UL1 As long as " is true, the current value I UL1 and I UL2 is optional.

[0075] <<First Example>> A first embodiment of the power supply device 1 will be described. As the target temperature TMP increases, the limit current I LIM As mentioned above, the limit current I decreases in two stages as the target temperature TMP increases. LIM may be decreased in three or more stages.

[0076] For example, when the target temperature TMP is rising and the target temperature TMP is lower than the lower limit of the first temperature range, the switching control circuit 10 LIM The value of I LIM1 When the target temperature TMP is within the first temperature range, the limit current I LIM The value of I LIM2 When the target temperature TMP is within the second temperature range, the limit current I LIM The value of I LIM3 When the target temperature TMP is higher than the upper limit of the second temperature range, the TSD operation may be performed. LIM1 >I LIM2 >I LIM3 Therefore, as the target temperature TMP rises, the limit current I​LIM The upper limit of the second temperature range is the threshold temperature T TSD As the target temperature TMP increases, the limit current I LIM The same applies when decreasing by four or more stages.

[0077] <<Second Example>> A second embodiment of the power supply device 1 will be described. As the target temperature TMP increases, the upper limit current I UL As mentioned above, the upper limit current I UL may be decreased in three or more stages.

[0078] For example, when the target temperature TMP is rising and the target temperature TMP is lower than the lower limit of the first temperature range, the gate control circuit 31b controls the upper limit current I UL The value of I UL1 When the target temperature TMP is within the first temperature range, the upper limit current I UL The value of I UL2 When the target temperature TMP is within the second temperature range, the upper limit current I UL The value of I UL3 Here, the second temperature range is higher than the first temperature range, and UL1 >I UL2 >I UL3 Therefore, as the target temperature TMP rises, the upper limit current I UL The upper limit of the second temperature range is the threshold temperature T TSD As the target temperature TMP rises, the upper limit current I UL The same applies when decreasing by four or more stages.

[0079] <<Third Example>> A third embodiment of the power supply device 1 will now be described.

[0080] Although the power supply 1 in FIG. 1 is a step-down switching power supply (switching regulator), the power supply 1 may also be a step-up switching power supply. A step-up switching power supply generates an output voltage Vout higher than the input voltage Vin by boosting the input voltage Vin. FIG. 14 is a partial configuration diagram of the power supply 1 when the power supply 1 is a step-up switching power supply. When the power supply 1 is a step-up switching power supply, as shown in FIG. 14, a first end of the coil L1 is connected to the input voltage Vin application terminal (the terminal to which the input voltage Vin is applied), a second end of the coil L1 is connected to the drain of the transistor MH and the source of the transistor ML, the source of the transistor MH is connected to ground, and the drain of the transistor ML is connected to the output terminal OUT and also to ground via the output capacitor C1. A switching control circuit 10 controls the switching of the output stage circuit MM (transistors MH and ML are alternately turned on and off) so that the feedback voltage Vfb coincides with the reference voltage Vref. 14, the transistor ML serving as a rectifying element may be replaced with a synchronous rectifying diode having an anode connected to the drain of the transistor MH and a cathode connected to the output terminal OUT. In either case, the output transistor (MH) is switched between on and off during switching control of the output stage circuit MM, thereby generating an output voltage Vout based on the current (IL) flowing through the coil L1. The power supply device 1 may be a step-up / step-down switching power supply device.

[0081] The power supply device 1 can be mounted in any electrical device, such as an electrical component mounted in a vehicle such as an automobile, a computer, a home appliance, or an industrial device.

[0082] With respect to any signal or voltage, the relationship between the high level and the low level thereof may be reversed without prejudice to the above-mentioned gist.

[0083] The channel types of the FETs (field effect transistors) shown in the above embodiments are merely examples, and the channel type of any FET may be changed between P-channel and N-channel types without departing from the spirit of the above.

[0084] Any of the transistors described above may be any type of transistor, provided that no disadvantages arise. For example, any of the transistors described above as MOSFETs may be replaced with junction field effect transistors (FETs), insulated gate bipolar transistors (IGBTs), or bipolar transistors, provided that no disadvantages arise. Any of the transistors has a first electrode, a second electrode, and a control electrode. In an FET, one of the first and second electrodes is the drain, the other is the source, and the control electrode is the gate. In an IGBT, one of the first and second electrodes is the collector, the other is the emitter, and the control electrode is the gate. In a bipolar transistor that is not an IGBT, one of the first and second electrodes is the collector, the other is the emitter, and the control electrode is the base.

[0085] The embodiments of the present disclosure can be modified in various ways as appropriate within the scope of the technical ideas set forth in the claims. The above-described embodiments are merely examples of the present disclosure, and the meanings of the terms of the present disclosure and each constituent element are not limited to those described in the above-described embodiments. The specific numerical values ​​shown in the above description are merely examples, and as a matter of course, they can be changed to various numerical values.

[0086] <<Additional Notes>> A supplementary note will be provided for the present disclosure, the specific configuration examples of which have been shown in the above-described embodiments.

[0087] A power supply control device according to one aspect of the present disclosure is a power supply control device (2) provided in a switching power supply device (1) configured to convert an input voltage (Vin) into an output voltage (Vout) through switching of an output transistor (MH), and includes a switching control circuit (10) configured to stabilize the output voltage by controlling the switching of the output transistor based on a feedback voltage (Vfb) corresponding to the output voltage, and a control circuit (110) configured to detect a target temperature (TMP) in the power supply control device and output signals (Stmp, S) indicating the detection result of the target temperature. PRETSD , S TSD a temperature detection circuit (20) configured to output a temperature signal (I ) to the switching control circuit, and the switching control circuit limits the current flowing through the output transistor to a limit current (I LIM ) or less, and the switching control circuit is configured to adjust the limited current in accordance with the target temperature (first configuration).

[0088] This makes it difficult for the target temperature to rise to a level that requires stopping switching control. As a result, adverse effects associated with stopping switching control are less likely to occur, which contributes to stable operation of subsequent circuits.

[0089] In the power supply control device according to the first configuration, the switching control circuit may be configured (second configuration) to reduce the limit current in stages as the target temperature increases.

[0090] In the power supply control device according to the second configuration, the switching control circuit is configured to: PRETSD ), the first current value (I LIM1 ), and when the target temperature is higher than the first threshold temperature but below a predetermined second threshold temperature (T TSD ), a second current value (I LIM2) and performs a thermal shutdown operation to stop the switching control when the target temperature is higher than the second threshold temperature (third configuration).

[0091] By setting the limit current to a relatively small second current value when the target temperature is higher than the first threshold temperature but lower than the second threshold temperature, the target temperature is less likely to rise to a level that requires stopping switching control. As a result, adverse effects associated with stopping switching control are less likely to occur. This contributes to stable operation of subsequent circuits.

[0092] In the power supply control device according to the third configuration, in the process of increasing the target temperature, an output signal (S PRETSD , S TSD ) the relationship in height between the target temperature and the first threshold temperature and the relationship in height between the target temperature and the second threshold temperature may be indicated (fourth configuration).

[0093] In the power supply control device according to the third or fourth configuration, the switching control circuit performs the thermal shutdown operation when the target temperature exceeds the second threshold temperature through an increase in the target temperature, and then performs the thermal shutdown operation when the target temperature reaches a predetermined third threshold temperature (T TSD -ΔT1), the switching control is continued to be stopped, and the target temperature is lower than the third threshold temperature but is equal to or lower than a predetermined fourth threshold temperature (T PRETSD -ΔT2), the second current value is set for the limit current, and the first current value is set for the limit current when the target temperature is lower than the fourth threshold temperature (fifth configuration).

[0094] In the power supply control device according to the fifth configuration, in the process of decreasing the target temperature, an output signal (S PRETSD , S TSD) to indicate the high / low relationship between the target temperature and the third threshold temperature and the high / low relationship between the target temperature and the fourth threshold temperature.

[0095] In the power supply control device according to any of the above first to sixth configurations, the switching control circuit may be configured to alternately turn on and off the output transistor in the switching control, and when the current flowing through the output transistor reaches the limit current while the output transistor is being controlled to be on in the switching control, to switch off the output transistor by the overcurrent protection operation (seventh configuration).

[0096] The power supply control device according to any one of the first to seventh configurations includes an internal linear regulator (31) configured to generate an internal power supply voltage (Vreg) by stepping down the input voltage, the internal linear regulator adjusting the internal power supply voltage by controlling a gate potential of an insertion transistor (31 a) inserted in series between an application terminal of the input voltage and an application terminal of the internal reference voltage, and the internal linear regulator adjusting the current flowing through the insertion transistor by controlling an upper limit current (I UL ) or less, and the internal linear regulator may be configured to adjust the upper limit current in accordance with the target temperature (eighth configuration).

[0097] This makes it possible to prevent the temperature of the internal linear regulator from becoming excessively high.

[0098] In the power supply control device according to the eighth configuration, the internal linear regulator may be configured to reduce the upper limit current in stages as the target temperature increases (ninth configuration).

[0099] This prevents the temperature of the internal linear regulator from becoming excessively high.

[0100] In the power supply control device according to any of the first to ninth configurations, the temperature detection circuit may be configured (tenth configuration) to detect the target temperature using a temperature measuring element (21) whose electrical characteristics change depending on the target temperature. [Explanation of symbols]

[0101] 1 Power supply (switching power supply) 2 Power supply control device CS chassis L1 coil C1 Output capacitor R1, R2 feedback resistors LD load IN input terminal OUT output terminal SW Switch terminal GND Ground terminal FB Feedback terminal Vin Input voltage Vout Output voltage Vsw Switch voltage Vfb Feedback voltage Vref Reference voltage Vreg Internal power supply voltage IL Coil current Iout Load current MM output stage circuit MH, ML transistors 10 Switching control circuit 11 Protection level setting circuit 11a constant current source 11b, 11c resistor 11d transistor 20 Temperature detection circuit 21 Transistor 22 Constant current source 23, 24 Comparator 25 Voltage generation circuit 30 Internal power circuit 31 Internal Linear Regulator 31a Transistor (insertion transistor) 31b Gate control circuit GH, GL gate signals Stmp temperature sensor output signal Vtmp, V TSD V PRETSD V OCP Electric pressure S TSD S PRETSD Signal TMP target temperature T TSD T PRETSD Yinhe temperature

Claims

1. A power supply control device provided in a switching power supply device configured to convert an input voltage into an output voltage through switching of an output transistor, a switching control circuit configured to stabilize the output voltage by controlling the switching of the output transistor based on a feedback voltage corresponding to the output voltage; a temperature detection circuit configured to detect a target temperature in the power supply control device and output a signal indicating the detection result of the target temperature to the switching control circuit; the switching control circuit is configured to be able to perform an overcurrent protection operation of limiting a current flowing through the output transistor to a limited current or less; The switching control circuit adjusts the limit current in response to the target temperature. , power control device.

2. The switching control circuit reduces the limit current stepwise as the target temperature increases. The power supply control device according to claim 1 .

3. The switching control circuit sets a first current value for the limit current when the target temperature is lower than a predetermined first threshold temperature during a rise in the target temperature, sets a second current value for the limit current that is smaller than the first current value when the target temperature is higher than the first threshold temperature but lower than a predetermined second threshold temperature, and performs a thermal shutdown operation to stop the switching control when the target temperature is higher than the second threshold temperature. The power supply control device according to claim 2 .

4. During the process of the target temperature rising, an output signal from the temperature detection circuit to the switching control circuit indicates the relationship between the target temperature and the first threshold temperature and the relationship between the target temperature and the second threshold temperature. The power supply control device according to claim 3 .

5. The switching control circuit performs the thermal shutdown operation when the target temperature exceeds the second threshold temperature through an increase in the target temperature, and then, in a process of decreasing the target temperature, continues to stop the switching control if the target temperature is higher than a predetermined third threshold temperature, sets the second current value for the limit current if the target temperature is lower than the third threshold temperature but higher than a predetermined fourth threshold temperature, and sets the first current value for the limit current if the target temperature is lower than the fourth threshold temperature. The power supply control device according to claim 3 .

6. During the process of decreasing the target temperature, an output signal from the temperature detection circuit to the switching control circuit indicates a relationship between the target temperature and the third threshold temperature and a relationship between the target temperature and the fourth threshold temperature. The power supply control device according to claim 5 .

7. The switching control circuit alternately turns on and off the output transistor in the switching control, and when the current flowing through the output transistor reaches the limit current while the output transistor is being controlled to be on in the switching control, switches off the output transistor through the overcurrent protection operation.

7. The power supply control device according to claim 1.

8. an internal linear regulator configured to generate an internal power supply voltage by stepping down the input voltage; the internal linear regulator adjusts the internal power supply voltage by controlling a gate potential of an insertion transistor inserted in series between an application terminal of the input voltage and an application terminal of the internal reference voltage; the internal linear regulator is configured to be able to perform another overcurrent protection operation of limiting a current flowing through the insertion transistor to an upper limit current or less; The internal linear regulator adjusts the upper limit current according to the target temperature.

7. The power supply control device according to claim 1.

9. The internal linear regulator gradually reduces the upper limit current as the target temperature increases. The power supply control device according to claim 8 .

10. The temperature detection circuit detects the target temperature using a temperature measuring element whose electrical characteristics change depending on the target temperature.

7. The power supply control device according to claim 1.

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