JP2013102603A - Semiconductor device and switching regulator using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which easily and more surely suppresses overheating of an internal power supply generating circuit while having an external terminal to which an internal power supply is sent.SOLUTION: The semiconductor device driven by using a supplied external power supply comprises: a first internal power supply generating circuit for generating a first internal power supply using the external power supply; an external terminal to which the first internal power supply is sent; a first thermal shutdown circuit driven using the first internal power supply; and a second thermal shutdown circuit driven using a power supply different from the first internal power supply. The second thermal shutdown circuit stops the operation of the first internal power supply generating circuit when overheating is detected.

Description

  The present invention relates to a semiconductor device having a thermal shutdown circuit and a switching regulator using the same.

  Conventionally, semiconductor devices (such as various ICs [Integrated Circuits]) having a thermal shutdown circuit have been widely used. Generally, a thermal shutdown circuit performs an overheat protection operation for suppressing overheating when overheating is detected. For example, a thermal shutdown circuit provided in the control IC for the switching regulator stops the switching operation when overheating is detected so that the overheating of the switching regulator can be suppressed. According to the thermal shutdown circuit, it is possible to prevent damage to the device due to overheating. In general, the IC is driven by using an external power supply (in this application, “power supply” may be used for power supply power in this application).

  Incidentally, as a driving power source for each circuit in the IC, an internal power source generated using an external power source is used in addition to an external power source supplied from outside the IC. For example, when there is a circuit in the IC that requires a drive power supply with higher accuracy (smaller voltage fluctuation or the like) than the external power supply, a highly accurate internal power supply is generated in the IC and supplied to the circuit. The above-described thermal shutdown circuit often uses a highly accurate internal power supply as a drive power supply so that the overheat protection operation can be performed accurately.

JP 2005-38921 A

  The above-described internal power supply path may be configured to include an external line for connection of a phase compensation capacitor, for example. In this case, by connecting an external capacitor to the external line, it is not necessary to provide the capacitor in the IC, and space saving of the IC is facilitated. In this case, the generated internal power supply is supplied into the IC through a path including an external line. In order to enable connection of such an external line or the like, the IC is provided with an external terminal to which an internal power supply is sent.

  However, in providing such an external terminal, it is necessary to consider a short mode (a situation where a ground fault or the like occurs in the external line). In this regard, an excessive current flows in the short mode, and the internal power generation circuit that generates the internal power may generate excessive heat. In order to prevent such a situation, it is conceivable that the thermal shutdown circuit stops the operation of the internal power generation circuit when overheating of the internal power generation circuit is detected.

  However, if the thermal shutdown circuit is driven by using the internal power supply, there is a possibility that the supply of the internal power supply becomes defective in the short mode and the thermal shutdown circuit does not operate properly. As a result, there arises a problem that overheating of the internal power generation circuit cannot be suppressed.

  In view of the above-described problems, an object of the present invention is to provide a semiconductor device that can easily suppress overheating of an internal power supply generation circuit while having an external terminal to which an internal power supply is sent. Another object of the present invention is to provide a switching regulator using the semiconductor device.

  In order to achieve the above object, a semiconductor device according to the present invention is a semiconductor device that is driven using a supplied external power source, and generates a first internal power source using the external power source. An external terminal to which the first internal power is sent, a first thermal shutdown circuit that is driven using the first internal power supply, and a second thermal shutdown circuit that is driven using a power supply different from the first internal power supply The second thermal shutdown circuit is configured to stop the operation of the first internal power generation circuit when overheating is detected.

  According to this configuration, it is easy to more reliably suppress overheating of the internal power supply generation circuit while having an external terminal to which the internal power supply is sent.

  In the above configuration, a second internal power generation circuit is provided that generates a second internal power using the external power and supplies the second internal power to the semiconductor device only through a path that does not include an external line. The circuit may be driven using the second internal power supply. In the above configuration, the second thermal shutdown circuit may be driven using the external power supply. In the above configuration, the first internal power generation circuit may supply the first internal power to the semiconductor device via an external line connected to the external terminal.

  In the above configuration, the second thermal shutdown circuit monitors the voltage value of the first internal power supply, and detects the overheating of the first internal power supply generation circuit only when the voltage value is equal to or less than a predetermined threshold value. 1 The operation of the internal power generation circuit may be stopped. In the above configuration, the second thermal shutdown circuit may be configured to detect overheating of the first internal power generation circuit using the temperature characteristics of the transistor.

  In the above configuration, a second internal power generation circuit is provided that generates a second internal power using the external power and supplies the second internal power to the semiconductor device only through a path that does not include an external line. The circuit is a circuit that is driven using the external power supply, and uses a buffer circuit to which a voltage of a second internal power supply is input, an output of the buffer circuit, and a temperature characteristic of the transistor, so that the first internal power supply is used. It is good also as a structure provided with the detection circuit which detects overheating of a generation circuit.

  Further, in the above configuration, a configuration may be employed in which a control signal used for controlling the switching element is generated for use in a switching regulator that performs voltage conversion by switching operation of the switching element. In the above configuration, the first thermal shutdown circuit may be configured to stop the switching operation when the overheating of the switching regulator is detected.

  A switching regulator according to the present invention includes the semiconductor device having the above structure. According to this configuration, it is possible to enjoy the advantages of the semiconductor device configured as described above.

  More specifically, as the configuration, an input voltage is input to one end, the other end is connected to the output terminal, one end is connected to the other end of the inductor, the other end is connected to a ground point, A first switching element that switches between an on state that conducts between both ends and an off state that does not conduct, a capacitor having one end connected to the output terminal and the other end connected to a ground point, and the input voltage input A second switching element having one end connected to the input terminal and the other end connected to one end of the inductor, wherein the second switching element switches between an on state and a non-conductive state. The apparatus may generate a signal used for controlling the first switching element and a signal used for controlling the second switching element as the control signal.

  More specifically, as the above configuration, the second switching element is kept on, and the first switching element performs a switching operation to boost the input voltage and output from the output terminal; and The first switching element may be kept off, and the second switching element may be switched to perform a step-down operation in which the input voltage is stepped down and output from the output terminal.

  More specifically, the first switching element and the second switching element may be MOS transistors. More specifically, as the configuration, the difference between the voltage of the driver provided on the transmission line of the control signal for controlling the second switching element and the voltage of the first power supply terminal of the driver and the voltage of the second power supply terminal is substantially omitted. It is good also as a structure provided with the voltage adjustment circuit kept constant. More specifically, the above configuration may be applied to an in-vehicle power supply device.

  As described above, according to the semiconductor device of the present invention, it is easy to more reliably suppress overheating of the internal power generation circuit while having an external terminal to which the internal power is sent. Further, according to the switching regulator according to the present invention, it is possible to enjoy the advantages of the semiconductor device according to the present invention.

It is a block diagram of the switching regulator which concerns on embodiment of this invention. It is a block diagram of the VL voltage generation circuit which concerns on embodiment of this invention. It is a block diagram of the 1st internal power generation circuit which concerns on embodiment of this invention. It is a block diagram of the 2nd thermal shutdown circuit which concerns on embodiment of this invention.

[Overall configuration of switching regulator]
FIG. 1 is a configuration diagram of a switching regulator (step-up / down switching regulator) 1 according to an embodiment of the present invention. As shown in the figure, the switching regulator 1 includes a regulator IC 10, each switching element (SW1, SW2), a coil (inductor) L1, each diode (D1, D2), each capacitor (C1 to C5), each resistor (R1). , R2), a power input terminal Vin, a voltage output terminal Vout, and the like.

  Each switching element (SW1, SW2) performs a switching operation for switching on / off (conduction / non-conduction between both ends) in accordance with an input control signal. As an example, in the case of a MOS transistor, the switching operation is an operation of switching conduction / non-conduction between the source and the drain in accordance with a control signal input to the gate. In the present embodiment, the switching element SW1 is an N-channel MOSFET and the switching element SW2 is a P-channel MOSFET. However, the present invention is not limited to this.

  The regulator IC 10 includes a first internal power generation circuit 21, a band gap voltage generation circuit 22, a low voltage malfunction prevention circuit 23, a first thermal shutdown circuit 24, a second internal power generation circuit 25, an oscillation circuit 31, and a slope circuit 32. , Soft start circuit 33, error amplifier 34, operational amplifier 35, comparators (36, 37), resistors (38a, 38b), short circuit protection comparator 41, overvoltage protection comparator 42, control circuit 51, A current detection circuit 52, a driver 53, a VL voltage generation circuit 54, a driver 55, and the like are included.

The regulator IC 10 is a semiconductor integrated circuit device (one form of semiconductor device) in which these are integrated. The regulator IC 10 has terminals (T _{1 to} T ₁₃ ) used for connection to the outside in addition to the ground terminal T _GND connected to the ground point.

The terminal T ₁ is connected to the power input terminal Vin. The power input terminal Vin is configured to receive a DC power source V _CC (for example, a power source of 4 to 40 V) from an external battery or the like. Also between the terminals T ₁ and the power input terminal Vin, one end of a capacitor C1, one end of the capacitor C2, and one end of the resistor R1 is connected.

The other end of the capacitor C1 is grounded, the other end of the capacitor C2 is connected to the terminal T _5. The other end of the resistor R1 is connected to the source of the switching element SW2. Note both ends of the resistor R1 are respectively connected to terminals T ₂ and the terminal T _3. The drain of the switching element SW2 is connected to the cathode of the diode D1 and one end of the coil L1. The anode of the diode D1 is grounded.

The other end of the coil L1 is connected to the anode of the diode D2 and the drain of the switching element SW1. The source of the switching element SW1 is grounded. The cathode of the diode D2 is connected to one end of the capacitor C3 and the voltage output terminal Vout. The output voltage V _O of the switching regulator 1 is output from the voltage output terminal Vout. The other end of the capacitor C3 is grounded.

The gate of the switching element SW2 is connected to the terminal T _4, a gate of the switching element SW1 is connected to the terminal T _7. Resistor R2 is a resistor used for frequency adjustment of the rectangular wave oscillation circuit 31 generates one end the other end is connected to the terminal T ₁₁ is grounded. Capacitor C4 is a capacitor used for phase compensation of an internal power supply V _REG which mainly below, one end of the other end is connected to the terminal T ₁₂ is grounded. A voltage V _FB corresponding to the output voltage V _O is input to the terminal T ₉ . The terminal T ₉ and the terminal T ₁₀ is connected via a such as an external capacitor.

The first internal power supply generation circuit 21 is connected to the terminal T ₁₃ of the terminal T ₁₂ and the enable signal is input, generates a DC of the internal power supply V _REG to be used in the regulator for the IC 10 (the first internal power supply) . The internal power supply V _REG is generated using a DC power supply V _CC and an internal power supply V _ref described later so that the accuracy of the voltage value and the like is higher than that of the DC power supply V _CC . The internal power supply V _REG is used as a drive power supply for the first thermal shutdown circuit 24 and the driver 55.

The first internal power supply generation circuit 21 sends the internal power supply V _REG which generated the terminal T _12. Thus, the first internal power supply generation circuit 21 is once sent an internal power supply V _REG, via a connected external line terminals T ₁₂ (transmission lines provided IC10 external regulator) to IC10 external regulator After that, it is pulled into the regulator IC 10. For example, the internal power supply V _REG sent to the external line returns to the regulator IC 10 via the terminal T ₆ and is input to the power supply terminal of the driver 55. A phase compensation capacitor C4 is connected to the external line.

As described above, in the regulator IC 10, at least a part of the transmission line of the internal power supply V _REG is provided outside the regulator IC 10, and the phase compensation capacitor C 4 is externally attached. Is easy. The configuration of the first internal power supply generation circuit 21 will be described in detail again.

The bandgap voltage generation circuit 22 receives the internal power supply V _REG from the first internal power supply generation circuit 21 and generates a bandgap voltage using this. The band gap voltage is generated so as to be more stable than the voltage of the internal power supply V _REG by using the band gap of the semiconductor, and is used in each part in the regulator IC 10.

The low-voltage malfunction prevention circuit 23 is a circuit that exhibits a UVLO [Under Voltage Lock Out] function in the regulator IC 10. The low-voltage malfunction prevention circuit 23 prevents the regulator IC 10 from being turned on, for example, when a DC power source V _CC having a certain voltage or higher is not inputted, in order to prevent malfunction caused by the input voltage being too low.

The first thermal shutdown circuit 24 is a circuit that prevents thermal runaway of the switching regulator 1 due to overheating (excessive temperature rise). For example, the first thermal shutdown circuit 24 continuously detects the temperature using a temperature sensor, and when the detected temperature exceeds the upper limit value, the switching operation of each switching element (SW1, SW2) is stopped. To. From the viewpoint of the operation accuracy of the first thermal shutdown circuit 24, the power supply for driving the first thermal shutdown circuit 24 is not the DC power supply V _CC but the internal power supply V _REG with higher accuracy such as the voltage value. .

The second internal power supply generation circuit 25 generates a DC internal power supply V _ref (second internal power supply) used in the regulator IC 10 by using the DC power supply V _CC . The internal power supply V _ref is generated as an internal power supply different from the internal power supply V _REG so that the accuracy of the voltage value and the like is higher than that of the DC power supply V _CC and is supplied to the first internal power supply generation circuit 21 and the like. . Unlike the internal power supply V _REG , the internal power supply V _ref is supplied into the regulator IC 10 only through a path that does not include an external line.

  The oscillation circuit 31 generates a rectangular wave voltage having a constant frequency and sends it to the subsequent stage side. Note that the frequency of the rectangular wave can be adjusted using the resistor R2. In addition, the slope circuit 32 performs processing for inclining the rising edge (or falling edge) of the rectangular wave voltage generated by the oscillation circuit 31, and the processed voltage (the sawtooth wave or a voltage having a waveform equivalent thereto). Is output to the non-inverting input terminal of each comparator (36, 37).

The soft start circuit 33 is a circuit that exhibits a soft start function in order to prevent an overshoot of the output voltage V _O and generation of an inrush current. The soft start circuit 33 supplies an appropriate voltage to the error amplifier 34 when the switching regulator 1 is started up so that the output voltage V _O gradually rises. The soft start circuit 33 operates based on the signal SS received from the overcurrent detection circuit 52, for example. The soft start circuit 33 is connected with a capacitor C5 for setting a soft start time. Capacitor C5 has one end connected to the soft start circuit 33 via the terminal T _8, the other end is grounded.

The error amplifier 34 receives the voltage V _FB at the inverting input terminal and the predetermined voltage V _{1 at} the non-inverting input terminal, and outputs a voltage corresponding to the difference in voltage value between the input terminals. When the switching regulator 1 is started, the output voltage of the soft start circuit 33 is given priority as the voltage input to the non-inverting input terminal of the error amplifier 34. The output side of the error amplifier 34, with which is connected to the inverting input terminal of the operational amplifier 35 through a resistor 38a, and is connected to the inverting input terminal and the terminal T ₁₀ of the comparator 37.

The operational amplifier 35 receives the predetermined voltage V _{2 at} the non-inverting input terminal and outputs a voltage corresponding to the difference in voltage value between the input terminals. The output side of the operational amplifier 35 is connected to the inverting input terminal of the comparator 36, and is connected between the resistor 38a and the inverting input terminal of the operational amplifier 35 via the resistor 38b. It can be seen that the resistor 38a, the resistor 38b, and the operational amplifier 35 form an inverting amplifier. Each comparator (36, 37) outputs a voltage corresponding to the comparison result of the voltage value of each input terminal to the control circuit 51.

The short circuit protection comparator 41 receives a voltage V _{FB at} a non-inverting input terminal and a predetermined voltage V _{3 at} an inverting input terminal, and outputs a comparison result of these voltages as a signal SCP for short circuit protection. The overvoltage protection comparator 42 receives the voltage V _{FB at the} non-inverting input terminal and the predetermined voltage V _{4 at the} inverting input terminal, and outputs a comparison result of these voltages as an overvoltage protection signal OVP.

The control circuit 51 performs PWM control of each switching element (SW1, SW2) based on a signal received from each comparator (36, 37). More specifically, the control circuit 51 outputs a control signal S1 for controlling the switching operation of the switching element SW1 according to the output signal of the comparator 36. Control signal S1, through the driver 55 and the terminal T _7, is input to the switching element SW1.

  When the control signal S1 is at the H (High) level, the switching element SW1 is turned on, and when the control signal S1 is at the L (Low) level, the switching element SW1 is turned off. Thus, the switching operation of the switching element SW1 is performed according to the duty of the output signal of the comparator 36.

Further, the control circuit 51 outputs a control signal S2 for controlling the switching operation of the switching element SW2 in accordance with the output signal of the comparator 37. Control signal S2, via the driver 53 and the terminal T _4, is input to the switching element SW2. Thus, the driver 53 is provided in the transmission line of the control signal S2 that connects the control circuit 51 and the switching element SW2.

  When the control signal S2 is at the H level, the switching element SW2 is turned off, and when the control signal S2 is at the L level, the switching element SW2 is turned on. Thus, the switching operation of the switching element SW2 is performed according to the duty of the output signal of the comparator 37.

Overcurrent detection circuit 52 detects the value of current flowing through the resistor R1 based on the voltage of the terminal T ₂ and the terminal T _3. The overcurrent detection circuit 52 outputs an overcurrent detection signal to the control circuit 51 when the detected value exceeds a predetermined upper limit value (that is, when an overcurrent is detected). Note that the control circuit 51 performs an operation (overcurrent protection operation) for preventing a problem caused by the overcurrent according to the overcurrent detection signal.

The first power supply terminal of the driver 53 is connected to the terminal T _1, the DC power supply V _CC is input. The VL voltage generation circuit 54 is connected to the second power supply terminal of the driver 53 and the terminal T ₅ , generates a voltage VL obtained by reducing the voltage of the DC power supply V _CC by a constant voltage Vs, and outputs the second power supply of the driver 53. Supply to the terminal. The voltage Vs is a voltage having an appropriate magnitude as the driving voltage of the driver 53 (the difference between the voltage of the first power supply terminal and the voltage of the second power supply terminal).

FIG. 2 shows the configuration of the VL voltage generation circuit 54. In the VL voltage generation circuit 54, each Zener diode (54a, 54b) and the current source 54c are provided in series between the input terminal of the DC power supply V _CC and the ground point. The sum of the Zener voltages of the respective Zener diodes (54a, 54b) is set to the voltage Vs, and the current source 54c is set to flow the current I necessary for generating the voltage VL.

According to the VL voltage generation circuit 54, a voltage VL (= V _CC −Vs) is generated between each Zener diode (54 a, 54 b) and the current source 54 c and supplied to the second power supply terminal of the driver 53. Note that the configuration of the VL voltage generation circuit 54 is not limited to the above-described configuration, and may be another configuration.

According to the VL voltage generation circuit 54, an appropriate drive voltage is supplied to the driver 53 regardless of voltage fluctuations of the DC power supply V _CC , and an excessive voltage is prevented from being applied to the driver 53. Thus, the VL voltage generation circuit 54 serves as a voltage adjustment circuit that keeps the difference between the voltage of the first power supply terminal and the voltage of the second power supply terminal of the driver 53 substantially constant.

[Basic operation of switching regulator]
Next, the basic operation of the switching regulator 1 will be described. The operation mode of the switching regulator 1 is basically the step-up mode in which the step-up operation is performed when the output voltage V _O is smaller than the target voltage, and the step-down mode in which the step-down operation is performed when the output voltage V _O is larger than the target voltage.

  In the boost mode, the output voltage of the error amplifier 34 is constantly higher than the output voltage of the slope circuit 32. Therefore, in the boost mode, the voltage output from the comparator 37 is constantly at the L level, and the switching element SW2 is constantly turned on.

  When the output voltage of the operational amplifier 35 is larger than the output voltage of the slope circuit 32, the output voltage of the comparator 36 becomes L level. Conversely, when the output voltage of the comparator circuit 36 is smaller than the output voltage of the slope circuit 32, the output voltage of the comparator 36 is H. Become a level. As a result, the output voltage of the comparator 36 varies in level, and the switching element SW1 is switched on / off according to the level variation.

When the switching element SW1 is turned on, magnetic energy is accumulated in the coil L1, and conversely, when the switching element SW1 is turned off, the magnetic energy accumulated in the coil L1 is released. In the step-up mode, the switching and switching of the switching element SW1 are repeated, whereby the magnetic energy is repeatedly stored and released in the coil L1. As a result of such a boosting operation, the voltage of the DC power supply V _CC is boosted to become the output voltage V _O and is output from the voltage output terminal Vout.

  On the other hand, in the step-down mode, the output voltage of the operational amplifier 35 is constantly higher than the output voltage of the slope circuit 32. Therefore, in the step-down mode, the voltage output from the comparator 36 is constantly at the L level, and the switching element SW1 is constantly turned off.

  When the output voltage of the error amplifier 34 is larger than the output voltage of the slope circuit 32, the output voltage of the comparator 37 becomes L level. Conversely, when the output voltage of the error circuit 34 is smaller than the output voltage of the slope circuit 32, the output voltage of the comparator 37 is Becomes H level. As a result, the output voltage of the comparator 37 varies in level, and the switching element SW2 is turned on / off in accordance with the level variation.

When the switching element SW2 is turned on, magnetic energy is accumulated in the coil L1, and conversely, when the switching element SW2 is turned off, the magnetic energy accumulated in the coil L1 is released. In the step-down mode, the switching and switching of the switching element SW2 are repeated, whereby the magnetic energy is repeatedly stored and released in the coil L1. As a result of such a step-down operation, the voltage of the DC power supply V _CC is stepped down to the output voltage V _O and output from the voltage output terminal Vout. The switching regulator 1 can also be an operation mode in a step-up / step-down mode in which the step-up operation and the step-down operation are switched.

[Configuration of first internal power generation circuit, etc.]
Next, the configuration and the like of the first internal power generation circuit 21 described above will be described in more detail. FIG. 3 is a configuration diagram of the first internal power supply generation circuit 21. The first internal power generation circuit 21 includes a P-channel MOSFET 21a, resistors (21b, 21c), an operational amplifier 21d, and a second thermal shutdown circuit 21e, and has a buffer circuit configuration as shown in FIG. Yes.

P-channel MOSFET21a has a source connected to the input terminal of the DC power supply V _CC, the drain is connected to one end and the terminal T ₁₂ of the resistor 21b. The gate of the P-channel MOSFET 21a is connected to the output terminal of the operational amplifier 21d. The other end of the resistor 21b is connected to the non-inverting input terminal of the operational amplifier 21d and grounded via the resistor 21c. The operational amplifier 21d uses the DC power supply V _CC as a drive power supply, and the voltage of the internal power supply _Vref is input to the inverting input terminal. The first internal power supply generation circuit 21 by this arrangement generates an internal power supply V _REG as a substantially constant voltage is output to the terminal T _12.

  The second thermal shutdown circuit 21e is provided separately from the first thermal shutdown circuit 24, and performs an overheat protection operation that suppresses overheating of the first internal power supply generation circuit 21. More specifically, the second thermal shutdown circuit 21e outputs an operation stop signal SD for stopping the operation of the operational amplifier 21d when detecting the overheating of the first internal power generation circuit 21, and the first internal power generation circuit 21. Stop the operation.

The second thermal shutdown circuit 21e is driven not by using the internal power supply _VREG as a drive power supply but by using the DC power supply _Vcc and the internal power supply _Vref . FIG. 4 shows a configuration diagram of the second thermal shutdown circuit 21e. As shown in the figure, the second thermal shutdown circuit 21e includes an operational amplifier 71, a current source 72, a switch 73, a VREG voltage monitoring circuit 74, resistors (75 to 79), and transistors (80, 81). Yes. The transistor 80 is an NPN type bipolar transistor, and the transistor 81 is a PNP type bipolar transistor.

In the operational amplifier 71, the voltage of the internal power supply _Vref is input to the non-inverting input terminal, and the output terminal of the operational amplifier 71 is connected to the inverting input terminal. In the operational amplifier 71, a DC power supply V _CC is input to a first power supply terminal, and a second power supply terminal is grounded via a current source 72 and a switch 73.

As a result, the operational amplifier 71 is driven by being supplied with the driving power when the switch 73 is closed, but is not driven when the switch 73 is open because the driving power is not supplied. The opening / closing of the switch 73 is controlled by the VREG voltage monitoring circuit 74. VREG voltage monitoring circuit 74 monitors the voltage value of the internal power supply V _REG, close the switch 73 when the voltage value is below a predetermined threshold V.alpha, and otherwise open the switch 73.

Note threshold Vα is set to the lower limit of the normal region in the voltage value of the internal power supply V _REG. As a result, the switch 73 is normally opened. However, when the voltage value of the internal power supply V _REG is abnormally lowered due to, for example, a short mode (a situation where a ground fault occurs in the external line), the switch 73 is Closed.

  The resistor 75 has one end connected to the output terminal of the operational amplifier 71 and the other end connected to one end of the resistor 76. The other end of the resistor 76 is connected to the base of the transistor 80 and grounded via the resistor 77. The resistor 78 has one end connected to the output terminal of the operational amplifier 71 and the other end connected to the base of the transistor 81 and the collector of the transistor 80.

  The emitter of the transistor 80 is grounded. The transistor 81 has an emitter connected to the output terminal of the operational amplifier 71 and a collector grounded via a resistor 79. The collector of the transistor 81 is connected to the output terminal of the operation stop signal SD. When the voltage of the collector of the transistor 81 is equal to or higher than a predetermined value, this voltage is output to the operational amplifier 21d as the operation stop signal SD.

In the second thermal shutdown circuit 21e, the operational amplifier 71 is connected so as to perform negative feedback, and forms a buffer circuit to which the voltage of the internal power supply _Vref is input. A detection circuit 90 having resistors (75 to 79) and transistors (80, 81) is formed on the rear side of the buffer circuit.

The detection circuit 90 is formed to detect overheating of the first internal power supply generation circuit 21 using the output of the buffer circuit and the temperature characteristics of the transistor 80. More specifically, the transistor 80 has a temperature characteristic (about −2 mV / ° C.) of the base emitter voltage V _be . The detection circuit 90 does not output the operation stop signal SD in the normal temperature region where the first internal power supply generation circuit 21 is not overheated, and the abnormal temperature region where the first internal power supply generation circuit 21 is overheated. Is set to output an operation stop signal SD.

That is, in the normal temperature region, the transistor 80 does not conduct sufficiently between the collector and the emitter because the base emitter voltage V _be is large. Therefore, the collector-emitter of the transistor 81 is hardly conducted, and the operation stop signal SD is not output. However, as the temperature rises, the base emitter voltage V _be decreases, and when the temperature reaches the abnormal temperature region, the collector-emitter of the transistor 80 is sufficiently conducted and the collector-emitter of the transistor 81 is also conducted. The operation stop signal SD is output.

As described above, the first internal power generation circuit 21 has a second thermal shutdown circuit that prevents overheating of the first internal power generation circuit 21 as a unique thermal shutdown circuit that is driven using a power supply different from the internal power supply V _REG. A shutdown circuit 21e is provided. The configuration forms of the first internal power generation circuit 21 and the second thermal shutdown circuit 21e described above are examples, and other configuration forms may be used.

Note that the operation accuracy of the thermal shutdown circuit depends on the accuracy of the voltage used. Further, the internal power supply V _ref has a lower voltage level than the internal power supply V _REG , and the voltage accuracy tends to deteriorate. Therefore, the second thermal shutdown circuit 21e that operates using the internal power supply V _ref is likely to have poorer operation accuracy than the first thermal shutdown circuit 24 that operates using the internal power supply _VREG . Therefore, the second thermal shutdown circuit 21e is not preferably used as a substitute for the first thermal shutdown circuit 24, and is used only as an auxiliary position of the first thermal shutdown circuit 24. For example, the second thermal shutdown circuit 21e is used as a circuit corresponding to only the short mode or the like.

[Others]
As described above, the regulator IC 10 is a semiconductor device that is driven using the supplied DC power supply V _CC (external power supply), generates the internal power supply V _REG using the DC power supply V _CC, and is connected to the external line. A first internal power supply generation circuit 21 that supplies the regulator IC 10 through a path including the internal power supply V _REG and a circuit that is driven using the internal power supply V _REG , and performs an operation of suppressing the overheat when an overheat is detected. A second thermal shutdown circuit that is provided separately from the first thermal shutdown circuit 24 and the first thermal shutdown circuit 24 and stops the operation of the first internal power generation circuit 21 when it detects an overheat of the first internal power generation circuit 21 And a circuit 21e. Note that the regulator IC 10 is provided with a terminal T ₁₂ (external terminal) to which the internal power supply V _REG is sent. By connecting an external line to the terminal T ₁₂ , the internal power supply V _REG can be drawn to the outside. It is possible.

The second thermal shutdown circuit 21e is driven using a power supply different from the internal power supply _VREG . Therefore, according to the regulator IC 10, it is easy to more reliably suppress overheating of the first internal power supply generation circuit 21 while supplying the internal power supply V _REG via a path including an external line. .

That is, in the short mode, for example, the first internal power generation circuit 21 generates excessive heat, and there is a possibility that a problem may occur in the supply of the internal power _VREG . But in this situation, the second thermal shutdown circuit 21e is for driving with a separate power supply from the internal power supply V _REG, it is possible to drive the impact of this problem without being almost. Therefore, the second thermal shutdown circuit 21e operates properly even in such a situation, and it is possible to suppress overheating of the first internal power supply generation circuit 21.

In the present embodiment, the regulator IC 10 generates the internal power supply V _ref using the DC power supply V _CC and supplies the internal power supply _Vref into the regulator IC 10 only through a path not including the external line. includes also 25, second thermal shutdown circuit 21e is configured to drive by using an internal power source V _ref and the DC power supply V _CC. However, the second thermal shutdown circuit 21e may be driven by using only one of the internal power supply V _ref and the DC power supply V _CC or using a power supply other than these.

The second thermal shutdown circuit 21e monitors the voltage value of the internal power supply V _REG in the VREG voltage monitoring circuit 74. The second thermal shutdown circuit 21e operates the first internal power generation circuit 21 when detecting the overheating of the first internal power generation circuit 21 only when the voltage value of the internal power supply V _REG is equal to or less than the threshold value Tα. Is supposed to stop. Note that, in a situation where the voltage value of the internal power supply V _REG exceeds the threshold value Tα, the switch 73 is opened, and such an overheat protection operation is not performed.

That is, the normal overheat protection operation in the switching regulator 1 is performed by the first thermal shutdown circuit 24. The second thermal shutdown circuit 21e performs the overheat protection operation only in a situation such as a short mode (the first thermal shutdown circuit 24 does not operate properly due to a supply failure of the internal power supply _VREG ).

As described above, the second thermal shutdown circuit 21e plays an auxiliary role of the first thermal shutdown circuit 24, and it is easy to have a relatively simple configuration. However, the form of the second thermal shutdown circuit 21e is not limited to this, and for example, an overheat protection operation may be performed regardless of the voltage value of the internal power supply _VREG .

  In the above embodiment, the semiconductor device used for the switching regulator (regulator IC 10) is taken as an example, but the semiconductor device according to the present invention is not limited to this. The semiconductor device according to the present invention includes various forms such as a control IC for controlling various electric devices.

Further, the switching regulator 1 includes a regulator IC 10, a coil L <b> 1 whose one end is input with the voltage of the DC power supply V _CC and the other end is connected to the voltage output terminal Vout, and one end connected to the other end of the coil L <b> 1. The other end is connected to the grounding point, one end is connected to the switching element SW1 that switches between the on state that conducts between both ends and the off state that does not conduct, and the voltage output terminal Vout, and the other end is connected to the grounding point. One end is connected to the connected capacitor C3 and the power input terminal Vin to which the voltage of the DC power supply V _CC is input, and the other end is connected to one end of the coil L1. A switching element SW2 whose state is switched.

  The regulator IC 10 generates a control signal S1 used for controlling the switching element SW1 and a control signal S2 used for controlling the switching element SW2. The switching regulator 1 performs a step-up operation and a step-down operation using these control signals.

  The switching regulator 1 is suitable for a vehicle-mounted power supply device, and can be widely applied to power supply devices for various electric devices. When applied to an in-vehicle power supply device, the switching regulator 1 is used, for example, in a form in which an in-vehicle battery is connected to the power input terminal Vin and an in-vehicle electric device is connected to the voltage output terminal Vout.

  The configuration of the present invention can be variously modified in addition to the above embodiment without departing from the spirit of the invention. That is, the above-described embodiment is an example in all respects and should not be considered as limiting, and the technical scope of the present invention is not the description of the above-described embodiment, but the claims. It should be understood that all modifications that come within the meaning and range of equivalents of the claims are included.

  The present invention can be used for a power supply device of various electric devices.

1 Switching regulator 10 Regulator IC (semiconductor device)
21 First internal power generation circuit 21a P-channel MOSFET
21b, 21c Resistance 21d Operational amplifier 21e Second thermal shutdown circuit 22 Band gap voltage generation circuit 23 Low voltage malfunction prevention circuit 24 First thermal shutdown circuit 25 Second internal power generation circuit 31 Oscillation circuit 32 Slope circuit 33 Soft start circuit 34 Error amplifier 35 operational amplifier 36, 37 comparator 38a, 38b resistor 41 short circuit protection comparator 42 overvoltage protection comparator 51 control circuit 52 overcurrent detection circuit 53 driver 54 VL voltage generation circuit 55 driver 71 operational amplifier 72 current source 73 switch 74 VREG Voltage monitoring circuit 75-79 Resistance 80, 81 Transistor C1-C5 Capacitor D1, D2 Diode L1 Coil SW1 Switching element SW2 Switching element R1, R2 Resistance ₁ through T ₁₃ terminals T _GND ground terminal Vin power input terminal Vout voltage output terminal

Claims (15)

A semiconductor device that is driven by using an external power supply,
A first internal power generation circuit that generates a first internal power using the external power;
An external terminal to which the first internal power is sent;
A first thermal shutdown circuit driven using a first internal power supply;
A second thermal shutdown circuit that is driven using a power source different from the first internal power source,
The second thermal shutdown circuit
A semiconductor device characterized in that the operation of the first internal power generation circuit is stopped when overheating is detected. A second internal power generation circuit that generates a second internal power supply using the external power supply and supplies the second internal power supply to the semiconductor device only through a path that does not include an external line;
The second thermal shutdown circuit
The semiconductor device according to claim 1, wherein the semiconductor device is driven using a second internal power supply. The second thermal shutdown circuit
The semiconductor device according to claim 1, wherein the semiconductor device is driven by using the external power source.   The first internal power generation circuit supplies the first internal power to the semiconductor device via an external line connected to the external terminal. The semiconductor device described. The second thermal shutdown circuit
Monitor the voltage value of the first internal power supply,
5. The operation of the first internal power generation circuit is stopped when overheating of the first internal power generation circuit is detected only in a situation where the voltage value is equal to or less than a predetermined threshold value. A semiconductor device according to any one of the above. The second thermal shutdown circuit
The semiconductor device according to claim 1, wherein overheating of the first internal power generation circuit is detected using a temperature characteristic of the transistor. A second internal power generation circuit that generates a second internal power supply using the external power supply and supplies the second internal power supply to the semiconductor device only through a path that does not include an external line;
The second thermal shutdown circuit
A circuit that is driven using the external power supply, and a buffer circuit to which a voltage of the second internal power supply is input;
A detection circuit for detecting overheating of the first internal power generation circuit using the output of the buffer circuit and the temperature characteristics of the transistor;
The semiconductor device according to claim 6, further comprising: Used in switching regulators that perform voltage conversion by switching operation of switching elements,
8. The semiconductor device according to claim 1, wherein a control signal used for controlling the switching element is generated. The first thermal shutdown circuit
9. The semiconductor device according to claim 8, wherein when the overheating of the switching regulator is detected, the switching operation is stopped.   A switching regulator comprising the semiconductor device according to claim 8. An inductor in which an input voltage is input to one end and the other end is connected to an output terminal;
A first switching element having one end connected to the other end of the inductor, the other end connected to a ground point, and switching between an on state in which the both ends are conductive and an off state in which the both ends are not conductive;
A capacitor having one end connected to the output terminal and the other end connected to a ground point;
A second switching element having one end connected to the input terminal to which the input voltage is input, the other end connected to one end of the inductor, and switching between an on state and a non-conducting off state between the both ends; With
The semiconductor device includes:
11. The switching regulator according to claim 10, wherein a signal used for controlling the first switching element and a signal used for controlling the second switching element are generated as the control signal. A step-up operation for boosting the input voltage and outputting the voltage from the output terminal by maintaining the second switching element on and causing the first switching element to perform a switching operation;
A step-down operation in which the input voltage is stepped down and output from the output terminal by keeping the first switching element off and causing the second switching element to perform a switching operation;
The switching regulator according to claim 11, wherein:   The switching regulator according to claim 12, wherein the first switching element and the second switching element are MOS transistors. A driver provided in a transmission line of a control signal for controlling the second switching element;
A voltage adjustment circuit for maintaining a substantially constant difference between the voltage of the first power supply terminal and the voltage of the second power supply terminal of the driver;
The switching regulator according to claim 13, further comprising:   The switching regulator according to any one of claims 10 to 14, wherein the switching regulator is applied to an in-vehicle power supply device.