Detection circuit, switch control circuit, power supply circuit

Abstract

The detection circuit of the present invention includes: a temperature voltage generating circuit, which generates a detection voltage corresponding to the temperature based on a specified current when a pulse signal is at a first level, and stops generating the detection voltage when the pulse signal is at a second level; and an output circuit, which outputs a detection signal indicating whether the temperature is higher than a specified temperature based on the detection voltage from the time when the pulse signal becomes the first level and a specified time has passed to the time when the pulse signal becomes the second level.

Description

Technical Field

[0001] The invention relates to a detection circuit, a switch control circuit and a power supply circuit. Background Art

[0002] As a circuit for detecting the temperature in an integrated circuit, there is generally a detection circuit using a diode (for example, Patent Documents 1 to 4).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: U.S. Patent No. 10228294

[0006] Patent Document 2: Japanese Patent Application Publication No. 2014-064392

[0007] Patent Document 3: Japanese Patent Application Publication No. 2017-163741

[0008] Patent Document 4: Japanese Patent Application Publication No. 2017-200386 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] However, in a detection circuit that detects temperature based on the forward voltage of a diode, current always flows through the diode, so although the output of the detection circuit is stable, the power consumption of the detection circuit is large. On the other hand, if the detection circuit is operated intermittently, the output of the detection circuit becomes unstable, but the power consumption of the detection circuit is reduced.

[0011] The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a technology capable of reducing power consumption and stably detecting temperature.

[0012] Technical solutions adopted to solve technical problems

[0013] In order to solve the above-mentioned problem, the detection circuit of the present invention includes: a temperature voltage generating circuit, which generates a detection voltage corresponding to the temperature based on a specified current when the pulse signal is at a first level, and stops generating the detection voltage when the pulse signal is at a second level; and an output circuit, which outputs a detection signal indicating whether the temperature is higher than a specified temperature based on the detection voltage from the time when the pulse signal becomes the first level and a specified time has passed to the time when the pulse signal becomes the second level.

[0014] In the switch control circuit mode of the present invention, the switch control circuit controls the switch of the switch element, and the switch element controls the inductor current flowing through the inductor of the power supply circuit. The switch control circuit includes: a determination circuit, which determines whether the load is a light load; an oscillation circuit, which outputs an oscillation signal for driving the switch element in a first mode when the load is the light load, and driving the switch element in a second mode when the load is not the light load; a drive circuit, which drives the switch element based on the oscillation signal; a pulse generation circuit, which generates a pulse signal; a temperature voltage A generating circuit, wherein when the pulse signal is at a first level, the temperature voltage generating circuit generates a detection voltage corresponding to the temperature based on a specified current, and when the pulse signal is at a second level, the temperature voltage generating circuit stops generating the detection voltage; and an output circuit, wherein after the pulse signal changes to the first level and a specified time has passed, and before the pulse signal changes to the second level, the output circuit outputs a detection signal indicating whether the temperature is higher than a specified temperature based on the detection voltage, and when the oscillation circuit receives the detection signal indicating that the temperature is higher than the specified temperature, the switching element stops the switching action.

[0015] A power supply circuit of the present invention is a power supply circuit for generating an output voltage of a target level on a secondary side, the power supply circuit comprising: a transformer having a primary coil provided on a primary side and a secondary coil provided on a secondary side; a switching element for controlling a current of the primary coil; and a switching control circuit for controlling switching of the switching element, the switching control circuit comprising: an oscillation circuit for outputting an oscillation signal for driving the switching element; a drive circuit for driving the switching element based on the oscillation signal; a pulse generating circuit for generating a pulse signal; a temperature voltage generating circuit for generating a detection voltage corresponding to a temperature based on a prescribed current when the pulse signal is at a first level, and for stopping generating the detection voltage when the pulse signal is at a second level; and an output circuit for outputting a detection signal indicating whether the temperature is higher than a prescribed temperature based on the detection voltage after a prescribed time has passed since the pulse signal has changed to the first level and before the pulse signal has changed to the second level, wherein when the oscillation circuit receives the detection signal indicating that the temperature is higher than the prescribed temperature, the switching element stops switching.

[0016] Effects of the Invention

[0017] According to the present invention, it is possible to provide a technology capable of reducing power consumption and stably detecting temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is a diagram showing an example of the configuration of the switching power supply circuit 10 .

[0019] Figure 2 1 is a diagram showing an example of the structure of the control IC 40 .

[0020] Figure 3 1 is a diagram showing an example of the configuration of the control circuit 60 .

[0021] Figure 4 1 is a diagram showing an example of the configuration of the detection circuit 80 .

[0022] Figure 5 2 is a diagram showing an example of the configuration of the rise delay circuit 94 .

[0023] Figure 6 1 is a diagram showing an example of the operation of the detection circuit 80 when the temperature in the control IC 40 is lower than a predetermined value.

[0024] Figure 7 1 is a diagram showing an example of the operation of the detection circuit 80 when the temperature in the control IC 40 is equal to or higher than a predetermined value.

[0025] Figure 8 : is a figure which shows an example of the structure of the control IC 41.

[0026] Fig. 9 It is a diagram for explaining the operation of the pulse generating circuit 71 . DETAILED DESCRIPTION

[0027] Cross-reference to related applications

[0028] This application claims priority based on Japanese Patent Application No. 2020-017090 filed on February 4, 2020, and cites the contents thereof.

[0029] At least the following matters are clarified from the description of this specification and the drawings.

[0030] ======Present Implementation Method======

[0031] <<<Overview of Switching Power Supply Circuit 10>>>

[0032] Figure 1 1 is a diagram showing a configuration of a switching power supply circuit 10 according to an embodiment of the present invention. The switching power supply circuit 10 is an LLC current resonance converter that generates an output voltage Vout of a target level to a load 11 based on a predetermined input voltage Vin.

[0033] The switching power supply circuit 10 includes capacitors 20 , 21 , 32 , NMOS transistors 22 , 23 , a transformer 24 , a control block 25 , diodes 30 , 31 , a constant voltage circuit 33 , and a light emitting diode 34 .

[0034] The capacitors 20 and 21 stabilize the voltage between the power supply line to which the input voltage Vin is applied and the ground line on the ground side, and remove noise, etc. The input voltage Vin is a DC voltage of a predetermined level.

[0035] The NMOS transistor 22 is a power transistor on the high voltage side, and the NMOS transistor 23 is a power transistor on the low voltage side. In this embodiment, the switching elements use NMOS transistors 22 and 23, but they may also be, for example, PMOS transistors, bipolar transistors, and IGBTs. The NMOS transistors 22 and 23 are equivalent to "switching elements".

[0036] The transformer 24 includes a primary coil L1, secondary coils L2, L3, and an auxiliary coil L4, and the primary coil L1, the secondary coils L2, L3, and the auxiliary coil L4 are insulated from each other. In the transformer 24, a voltage is generated in the secondary coils L2, L3 on the secondary side according to a voltage change across the primary coil L1 on the primary side, and a voltage is generated in the auxiliary coil L4 on the primary side according to a voltage change across the secondary coils L2, L3.

[0037] One end of the primary coil L1 is connected to the source of the NMOS transistor 22 and the drain of the NMOS transistor 23, and the other end is connected to the source of the NMOS transistor 23 via the capacitor 21. The primary coil L1 is equivalent to an "inductor".

[0038] Therefore, when the NMOS transistors 22 and 23 start switching, the voltages of the secondary coils L2 and L3 and the auxiliary coil L4 change. The primary coil L1 and the secondary coils L2 and L3 are electromagnetically coupled with the same polarity, and the secondary coils L2 and L3 and the auxiliary coil L4 are also electromagnetically coupled with the same polarity.

[0039] The control block 25 is a circuit block for controlling the switching of the NMOS transistors 22 and 23 , and the details will be described later.

[0040] The diodes 30 and 31 rectify the voltages of the secondary coils L2 and L3, and the capacitor 32 smoothes the rectified voltages. As a result, a filtered output voltage Vout is generated in the capacitor 32. The output voltage Vout becomes a DC voltage of a target level.

[0041] The constant voltage circuit 33 is a circuit that generates a constant DC voltage and is configured by, for example, a shunt regulator.

[0042] The light emitting diode 34 is an element whose light emission intensity corresponds to the difference between the output voltage Vout and the output of the constant voltage circuit 33, and constitutes a photocoupler together with a phototransistor 57 described later. In this embodiment, when the level of the output voltage Vout increases, the intensity of light emitted by the light emitting diode 34 increases.

[0043] The switching power supply circuit 10 corresponds to a “power supply circuit”.

[0044] <<<Control Block 25>>>

[0045] The control block 25 includes a control IC 40 , capacitors 50 to 53 , resistors 54 and 55 , a diode 56 , and a phototransistor 57 .

[0046] The control IC 40 is an integrated circuit that controls the switching of the NMOS transistors 22 and 23 , and has terminals VCC, GND, FB, IS, HO, and LO.

[0047] The terminal VCC is a terminal to which the power supply voltage Vcc for operating the control IC 40 is applied. The terminal VCC is connected to the capacitor 52 whose one end is grounded and the cathode of the diode 56. Therefore, the capacitor 52 is charged by the current from the diode 56, and the charging voltage of the capacitor 52 is the power supply voltage Vcc for operating the control IC 40. The control IC 40 is started by applying the divided voltage of the input voltage Vin via a terminal not shown in the figure, and operates based on the power supply voltage Vcc after starting.

[0048] The terminal GND is a terminal to which a ground voltage is applied, and is connected to, for example, a housing of a device provided with the switching power supply circuit 10 .

[0049] The terminal FB is a terminal for generating a feedback voltage Vfb corresponding to the output voltage Vout, and is connected to the capacitor 53 and the phototransistor 57. The capacitor 53 is provided to remove noise between the terminal FB and the ground, and the phototransistor 57 allows a bias current I1 corresponding to the intensity of light emitted by the light emitting diode 34 to flow from the terminal FB to the ground. Therefore, the phototransistor 57 operates as a transistor for generating a sink current.

[0050] The terminal IS is a terminal to which a voltage corresponding to the input power of the switching power supply circuit 10 is applied. Here, a voltage corresponding to the current value of the resonant current of the primary coil L1 is generated at a node where the capacitor 50 and the resistor 54 are connected. In addition, the resistor 55 and the capacitor 51 constitute a low-pass filter. Therefore, a voltage corresponding to the current value of the resonant current of the primary coil L1 and from which the noise component is removed is applied to the terminal IS. The resonant current of the primary coil L1 is equivalent to the "inductor current".

[0051] The current value of the resonant current increases with the input power of the switching power supply circuit 10, and the input power of the switching power supply circuit 10 increases with the power consumed by the load 11. Therefore, the voltage applied to the terminal IS represents a voltage corresponding to the power consumption of the load 11.

[0052] The terminal HO is a terminal for outputting a drive signal Vdr1 for driving the NMOS transistor 22 , and is connected to the gate of the NMOS transistor 22 .

[0053] The terminal LO is a terminal for outputting a driving signal Vdr2 for driving the NMOS transistor 23 , and is connected to the gate of the NMOS transistor 23 .

[0054] <<<Control IC40>>>

[0055] Figure 2 : is a figure which shows the structure of the control IC40. The control IC40 includes a control circuit 60, a pulse generation circuit 70, and a detection circuit 80. Here, the terminals VCC and GND are omitted. The control IC40 is equivalent to a "switch control circuit".

[0056] <<<Control Circuit 60>>>

[0057] Figure 3 6 is a diagram showing the structure of the control circuit 60. The control circuit 60 includes a resistor 61, a determination circuit 62, an oscillation circuit 63, and a drive circuit 64. The resistor 61 pulls up the wiring connected to the terminal FB to the power supply voltage Vdd. The internal power supply circuit (not shown) in the control IC 40 generates the power supply voltage Vdd based on the voltage Vcc applied to the terminal VCC.

[0058] The determination circuit 62 determines whether the load 11 is a light load based on the feedback voltage Vfb and the voltage Vca, and determines switching between the normal mode and the burst mode.

[0059] Here, if the load 11 is a light load, the output voltage Vout rises above the target level. Figure 1 The internal input of the constant voltage circuit 33 constituted by the shunt regulator increases, and in order to make the output constant, a large current flows through the transistor inside the shunt regulator (not shown).

[0060] As a result, a large current also flows through the light emitting diode 34. Then, the phototransistor 57 allows a bias current I1 having a magnitude corresponding to the amplification degree of light emitted from the light emitting diode 34 to flow from the terminal FB to the ground, thereby reducing the feedback voltage Vfb.

[0061] For example, when the input feedback voltage Vfb is lower than the feedback voltage Vfb when the output voltage Vout is at the target level and the input voltage Vca is lower than a predetermined level as a light load reference, the determination circuit 62 determines that the load 11 is a light load and determines to switch to the burst mode.

[0062] The determination circuit 62 determines that the load 11 is not a light load and determines to switch to the normal mode when the feedback voltage Vfb is higher than the feedback voltage Vfb when the output voltage Vout is the target level or the input voltage Vca is higher than a predetermined level as a light load reference.

[0063] The "normal mode" is a mode in which the control circuit 60 continuously drives the NMOS transistors 22 and 23 without stopping, and the "burst mode" is a mode in which the control circuit 60 intermittently drives the NMOS transistors 22 and 23. The burst mode is equivalent to the "first mode" and the normal mode is equivalent to the "second mode".

[0064] When the switching power supply circuit 10 operates in the normal mode, the switching power supply circuit 10 is in a state of not operating in the burst mode. Therefore, when the switching power supply circuit 10 operates in the normal mode, the switching power supply circuit 10 is not operating in the burst mode.

[0065] The oscillation circuit 63 is a voltage-controlled oscillation circuit that outputs an oscillation signal Vosc for switching the NMOS transistors 22 and 23 based on the input feedback voltage Vfb and the determination result from the determination circuit 62 .

[0066] When the determination result from the determination circuit 62 indicates the normal mode, the oscillation circuit 63 outputs the oscillation signal Vosc for continuously driving the NMOS transistors 22 and 23. When the determination result from the determination circuit 62 indicates the burst mode, the oscillation circuit 63 outputs the oscillation signal Vosc for intermittently driving the NMOS transistors 22 and 23.

[0067] The drive circuit 64 drives the NMOS transistors 22 and 23 at the frequency of the oscillation signal Vosc. Specifically, the drive circuit 64 outputs pulse-shaped drive signals Vdr1 and Vdr2 having the frequency of the oscillation signal Vosc and a constant duty ratio (eg, 50%) to the NMOS transistors 22 and 23, respectively.

[0068] The drive circuit 64 sets a dead time to prevent the NMOS transistors 22 and 23 from being turned on at the same time, and changes the drive signal Vdr1 and the drive signal Vdr2 in a complementary manner.

[0069] Here, for example, when operating in the normal mode, if the level of the output voltage Vout rises above the target level, the feedback voltage Vfb decreases, so the frequency of the oscillation signal Vosc increases. As a result, the output voltage Vout of the switching power supply circuit 10 as an LLC current resonance converter decreases.

[0070] On the other hand, if the level of the output voltage Vout drops below the target level, the feedback voltage Vfb rises, so the frequency of the oscillation signal Vosc decreases. As a result, the output voltage Vout of the switching power supply circuit 10 rises. Therefore, the switching power supply circuit 10 can generate the output voltage Vout of the target level.

[0071] The same operation is performed when operating in the burst mode. For example, when the oscillation circuit 63 detects the signal OTP from the detection circuit 80 (described later), the oscillation signal Vosc is stopped. When the oscillation signal 63 receives the signal OTP, the switching power supply circuit 10 stops the switching operation, the NMOS transistor 22 and the NMOS transistor 23 stop operating, and the power supply to the load 11 is stopped.

[0072] <<<<Pulse generating circuit 70>>>>

[0073] Figure 2 The pulse generating circuit 70 is a circuit that outputs a pulse signal pulse to a detection circuit 80 (described later) based on a specified signal. For example, the pulse generating circuit 70 generates a pulse signal pulse having a constant duty cycle based on an output signal of a ring oscillator or other oscillation signals, and the period during which the pulse signal pulse is at a high level (hereinafter referred to as "H" level) accounts for, for example, 10% of one cycle.

[0074] <<<<Structure of detection circuit 80>>>>

[0075] Figure 4 Detection circuit 80 is a diagram showing a configuration of detection circuit 80. Detection circuit 80 is a circuit for detecting the temperature in control IC 40. Detection circuit 80 includes temperature voltage generation circuit 81 and output circuit 82.

[0076] The temperature voltage generating circuit 81 includes a diode 91, a constant current source 92 to which a voltage Vcc is applied and which generates a forward current Id flowing through the diode 91, and a switch 93 for intermittently passing the forward current Id through the diode 91. Intermittently passing the forward current Id through the diode 91 can suppress the heating of the diode 91 itself and can detect the temperature with high accuracy.

[0077] The diode 91 corresponds to a "temperature detection element," and the forward current Id corresponds to a "predetermined current." As the "temperature detection element," a polysilicon resistor that can be used as a temperature sensor may be used, for example, in addition to a diode.

[0078] When the pulse signal pulse is at the "H" level, the temperature voltage generating circuit 81 causes the forward current Id to flow through the diode 91, and generates the forward voltage VF of the diode 91 corresponding to the temperature as the detection voltage. On the other hand, when the pulse signal pulse is at a low level (hereinafter referred to as the "L" level), the temperature voltage generating circuit 81 stops generating the forward voltage VF.

[0079] The forward voltage VF of the diode 91 has a negative temperature characteristic, and when the temperature in the control IC 40 rises, the forward voltage VF decreases. On the other hand, when the temperature in the control IC 40 drops, the forward voltage VF increases.

[0080] The constant current source 92 is a temperature-compensated constant current source, and causes a predetermined forward current Id to flow through the diode 91 independently of the temperature in the control IC 40. Specifically, the constant current source 92 generates a current using a reference voltage circuit (not shown), and operates as a temperature-compensated constant current source.

[0081] The switch 93 is turned on when the pulse signal pulse from the pulse generating circuit 70 is at the "H" level, and supplies the forward current Id flowing from the constant current source 92 to the diode 91. On the other hand, when the pulse signal pulse is at the "L" level, the switch element 93 is turned off, and the forward current Id stops flowing through the diode 91.

[0082] The output circuit 82 outputs a detection signal indicating whether the temperature is higher than the "predetermined temperature To (e.g., 140°C)" after the pulse signal pulse from the pulse generating circuit 70 is at the "H" level and the "predetermined time Tp" has passed, and before the pulse signal pulse changes to the "L" level. That is, the output circuit 82 is a circuit that compares the forward voltage VF from the temperature voltage generating circuit 81 with the high reference voltage VREF1 and the low reference voltage VREF2 corresponding to the "predetermined temperature To", and outputs the comparison result comp as the signal OTP. The output circuit 82 includes a rise delay circuit 94, a hysteresis comparator 95, and an AND gate circuit 96. The signal OTP is equivalent to the "detection signal".

[0083] like Figure 5As shown, the rising delay circuit 94 includes a resistor 101, a capacitor 102, an inverter 103, an NMOS transistor 104, a comparator 105 and an inverter 106. The resistor 101 and the capacitor 102 form an integrating circuit for integrating the pulse signal pulse, delaying the rising edge of the pulse signal pulse by a "predetermined time Tp".

[0084] The inverter 103 and the NMOS transistor 104 constitute a discharge circuit for discharging the charge accumulated in the capacitor 102. When the pulse signal pulse is at "L" level, the inverter 103 and the NMOS transistor 104 discharge the capacitor 102 and reduce the voltage applied to the inverting input terminal of the comparator 105.

[0085] The comparator 105 compares the voltage at one end of the capacitor 102 with the reference voltage VREF3 and outputs the comparison result. The comparison result is inverted by the inverter 106 and becomes a delayed pulse signal pulse_d.

[0086] The rising delay circuit 94 corresponds to a “signal output circuit”, and the delayed pulse signal pulse_d corresponds to a “predetermined signal”.

[0087] Here, the "predetermined time Tp" is determined by a time constant calculated based on the resistance value of the resistor 101 and the capacitance value of the capacitor 102. The "predetermined time Tp" is longer than the "first period Ta" from when the pulse signal pulse becomes "H" level to when the forward current Id is provided to generate a detection voltage corresponding to the temperature in the control IC 40, and the "second period Tb" from when the pulse signal pulse becomes "H" level to when the comparison result comp of the hysteresis comparator 95 (described later) is output.

[0088] Refer again Figure 4 , the hysteresis comparator 95 is activated when the pulse signal pulse becomes "H" level, compares the forward voltage VF from the temperature voltage generating circuit 81 with the high reference voltage VREF1 and the low reference voltage VREF2, and outputs the comparison result comp. When the forward voltage VF is higher than the high reference voltage VREF1, the hysteresis comparator 95 outputs a signal of "L" level, and conversely, when the forward voltage VF is lower than the low reference voltage VREF2, the hysteresis comparator 95 outputs a signal of "H" level. The hysteresis comparator 95 is equivalent to a "comparison circuit", and the high reference voltage VREF1 and the low reference voltage VREF2 are equivalent to "reference voltages corresponding to a specified temperature".

[0089] The AND gate circuit 96 obtains the logical sum of the delayed pulse signal pulse_d and the comparison result comp from the hysteresis comparator 95, and outputs the comparison result comp as the signal OTP only when the delayed pulse signal pulse_d is at the "H" level. The AND gate circuit 96 is equivalent to a "logic circuit".

[0090] <<<<Operation of the Pulse Generating Circuit 70 and the Detecting Circuit 80>>>>

[0091] The pulse generating circuit 70 generates a pulse signal pulse that oscillates at a fixed frequency regardless of whether the switching power supply circuit 10 operates in the “normal mode” or the “burst mode”.

[0092] Figure 6 1 is a diagram showing the operation of the detection circuit 80 when the temperature in the control IC 40 is lower than the "predetermined temperature To (e.g., 140°C)" and the signal OTP does not reach the "H" level. The pulse signal pulse is generated by the pulse generation circuit 70 and oscillates at a fixed frequency. After the pulse signal pulse is input to the output circuit 82, a delayed pulse signal pulse_d delayed by the "predetermined time Tp" is generated. When the pulse signal pulse is at the "L" level, the generated delayed pulse signal pulse_d is at the "L" level.

[0093] At time t0, the pulse signal pulse of the "H" level is input to the output circuit 82. At this time, in the temperature voltage generating circuit 81, the switch 93 is turned on, so the forward current Id is supplied to the diode 91 by the constant current source 92. Then, the hysteresis comparator 95 starts to start. The case where the logic level of the pulse signal pulse is the "H" level is equivalent to the case where the pulse signal is the "first level".

[0094] At time t1, the forward current Id becomes a predetermined value, and the constant current source 92 supplies the predetermined forward current Id to the diode 91. As a result, the forward voltage VF of the diode 91 becomes a voltage corresponding to the temperature in the control IC 40. The "first period Ta" until the forward current Id becomes a predetermined value and the diode 91 becomes a voltage corresponding to the temperature, that is, the time t0 to t1 corresponds to the "first period".

[0095] For example, at time t2, after the hysteresis comparator 95 is activated, the hysteresis comparator 95 compares the forward voltage VF from the temperature voltage generating circuit 81 with the high reference voltage VREF1 and the low reference voltage VREF2, and outputs the comparison result comp. The "second period Tb" from t0 to t2 until the hysteresis comparator 95 outputs the comparison result comp corresponds to the "second period".

[0096] At time t3 after a predetermined time Tp after time t0, the delayed pulse signal pulse_d reaches the "H" level. At this time, the pulse signal pulse is at the "H" level, a predetermined forward current Id flows through the diode 91, and the hysteresis comparator 95 outputs a comparison result comp.

[0097] Then, the hysteresis comparator 95 compares the forward voltage VF from the temperature voltage generating circuit 81 with the high reference voltage VREF1 and the low reference voltage VREF2, and outputs the comparison result comp to the AND gate circuit 96. Since the delayed pulse signal pulse_d is at the "H" level and the forward voltage VF of the diode 91 is higher than the high reference voltage VREF1, the AND gate circuit 96 outputs the signal OTP at the "L" level.

[0098] At time t4, when the pulse signal pulse changes to the "L" level, the delayed pulse signal pulse_d also changes to the "L" low level. When the delayed pulse signal pulse_d changes to the "L" low level, the level of the signal OTP output by the AND gate circuit 96 is maintained at the "L" level. The situation where the logic level of the pulse signal pulse is the "L" level is equivalent to the situation where the pulse signal is the "second level".

[0099] At time t5, the pulse signal pulse changes to the "H" level, and the operation from time t0 to time t5 is repeated.

[0100] As shown above, in this embodiment, only when the pulse signal pulse is at the "H" level, the constant current source 92 provides the forward current Id to the diode 91. Moreover, the temperature is detected only when the pulse signal pulse_d after the pulse signal pulse is delayed by the "predetermined time Tp" is at the "H" level. Thus, the power consumption can be reduced and the temperature can be stably detected.

[0101] Figure 7 1 is a diagram showing the operation of the detection circuit 80 when the temperature in the control IC 40 is above the "predetermined temperature To (for example, 140° C.)" and the signal OTP becomes "H" level. Figure 6 The situation is generated in the same way.

[0102] At time t10, the pulse signal pulse of the "H" level is input to the output circuit 82. At this time, in the temperature voltage generating circuit 81, the switch 93 is turned on, so that the forward current Id is supplied from the constant current source 92 to the diode 91. Then, the hysteresis comparator 95 starts to operate.

[0103] At time t11, the forward current Id reaches a predetermined value, and the constant current source 92 supplies the predetermined forward current Id to the diode 91. As a result, the forward voltage VF of the diode 91 reaches a voltage corresponding to the temperature in the control IC 40.

[0104] For example, at time t12, after the hysteresis comparator 95 is activated, the hysteresis comparator 95 compares the forward voltage VF from the temperature voltage generating circuit 81 with the high reference voltage VREF1 and the low reference voltage VREF2, and outputs a comparison result comp.

[0105] At time t13 after a "predetermined time Tp" has passed from time t10, the delayed pulse signal pulse_d becomes "H" level. At this time, the pulse signal pulse is "H" level, a predetermined forward current Id flows through the diode 91, and the hysteresis comparator 95 outputs a comparison result comp of "H" level.

[0106] Then, the hysteresis comparator 95 compares the forward voltage VF from the temperature voltage generating circuit 81 with the high reference voltage VREF1 and the low reference voltage VREF2, and outputs the comparison result comp to the AND gate circuit 96. Since the delayed pulse signal pulse_d is at the "H" level and the forward voltage VF of the diode 91 is lower than the low reference voltage VREF2, the AND gate circuit 96 outputs the signal OTP at the "H" level.

[0107] At time t14, when the pulse signal pulse changes to "L" level, the delayed pulse signal pulse_d also changes to "L" level. When the delayed pulse signal pulse_d changes to "L" level, the AND gate circuit 96 outputs the signal OTP of "L" level.

[0108] At time t15, the pulse signal pulse changes to the "H" level, and then the operation from time t10 to time t15 is repeated.

[0109] As described above, if the temperature in the control IC 40 is detected after the “predetermined time Tp” based on the pulse signal pulse, the detection circuit 80 can reduce power consumption and stably detect the temperature.

[0110] In the above description, the case where the control IC 40 used for the LLC current resonance type converter includes the detection circuit 80 is described. However, the detection circuit 80 may be used for a control IC that controls a converter other than the LLC current resonance type converter.

[0111] ===Modification Example===

[0112] Figure 84 is a diagram showing a configuration of a control IC 41 when a pulse generating circuit 71 generates a pulse signal pulse based on a signal Vosc. The control IC 41 may be used instead of the control IC 40 . Figure 8 In, with Figure 2 Identical objects are provided with the same reference symbols.

[0113] The pulse generating circuit 71 outputs the pulse signal pulse of “H” level when detecting the rising edge of the signal Vosc, for example, and outputs the pulse signal pulse of “L” level when detecting the rising edge of the signal Vosc three times, for example.

[0114] When the pulse signal pulse is at the “L” level, the pulse generating circuit 71 , for example, continues to output the pulse signal pulse at the “L” level until, for example, at least nine rising edges of the signal Vosc are detected.

[0115] Then, when the pulse generating circuit 71 detects the rising edge of the signal Vosc, for example, it again outputs the pulse signal pulse of the “H” level based on the rising edge of the signal Vosc.

[0116] Reference Fig. 9 , describing the operation of the pulse generating circuit 71 when generating the pulse signal pulse based on the signal Vosc with a period corresponding to the signal Vosc.

[0117] First, explain Fig. 9 How does the pulse generating circuit 71 operate when the switching power supply circuit 10 operates in the "normal mode"?

[0118] At time t20, when the pulse generating circuit 71 detects the rising edge of the signal Vosc, for example, it outputs the pulse signal pulse of "H" level. At time t21, when the rising edge of the signal Vosc is detected three times after time t20, for example, the pulse generating circuit 71 outputs the pulse signal pulse of "L" level.

[0119] When the pulse signal pulse is at the “L” level, the pulse generating circuit 71 , for example, continues to output the pulse signal pulse at the “L” level until, for example, at least nine rising edges of the signal Vosc are detected.

[0120] At time t22 , when the pulse generating circuit 71 detects, for example, a rising edge of the signal Vosc, it outputs the pulse signal pulse of the “H” level again, and repeats the operation from time t20 to time t21 .

[0121] Next, explain Fig. 9 How does the pulse generating circuit 71 operate when the switching power supply circuit 10 operates in the "burst mode"?

[0122] At time t23, the pulse generating circuit 71 outputs an "H" level pulse signal pulse when detecting a rising edge of the signal Vosc, for example. At time t24, the pulse generating circuit 71 outputs an "L" level pulse signal pulse when detecting a rising edge of the signal Vosc, for example, three times after time t23.

[0123] When the pulse signal pulse is at the “L” level, the pulse generating circuit 71 , for example, continues to output the pulse signal pulse at the “L” level until, for example, at least nine rising edges of the signal Vosc are detected.

[0124] At time t25, when the pulse generating circuit 71 detects the rising edge of the signal Vosc, for example, it outputs the pulse signal pulse of the "H" level again and repeats the operation of time t23 to t24. That is, the pulse generating circuit 71 outputs the pulse signal pulse of the "H" level based on the timing of the signal Vosc.

[0125] As described above, in the "burst mode" and the "normal mode", when the NMOS transistor 22 and the NMOS transistor 23 perform switching operations, a pulse signal pulse is generated. Moreover, the period of the pulse signal pulse when the switching power supply circuit 10 operates in the "burst mode" is greater than the period of the pulse signal pulse when the switching power supply circuit 10 operates in the "normal mode".

[0126] ===Summary===

[0127] The switching power supply circuit 10 of the present embodiment has been described above. If the temperature in the control IC 40 is detected after the "predetermined time Tp" based on the pulse signal pulse, the detection circuit 80 can reduce power consumption and stably detect the temperature.

[0128] Furthermore, when the forward current Id flows through the temperature detection element, a highly accurate detection result can be obtained by using the constant current source 92 that can flow the temperature-compensated forward current Id.

[0129] Furthermore, by intermittently passing the forward current Id through the diode 91 , it is possible to suppress the heat generation of the diode 91 itself and detect the temperature with high accuracy.

[0130] Furthermore, the output circuit 82 has a rising delay circuit 94, which can delay the rising timing of the pulse signal pulse by a predetermined time. The predetermined time is a waiting time for the constant current source 92 to flow the forward current Id, or a waiting time for the hysteresis comparator 95 to output the comparison result comp.

[0131] By making the predetermined time longer than the time required for the constant current source 92 and the hysteresis comparator 95 to reach stable operation, the accuracy of temperature detection can be improved.

[0132] Furthermore, the detection circuit 80 is used in the switch control circuit used in the power supply circuit, thereby preventing malfunction due to heat.

[0133] Furthermore, by setting the period of the pulse signal pulse to a predetermined period, even when the load is light, the temperature in the control IC 40 can be measured. Thus, even when unexpected heat is generated, the temperature is always detected at a predetermined period, so that even when the load is light, the control IC 40 can be prevented from malfunctioning.

[0134] Furthermore, by generating the pulse signal pulse based on the cycle of the oscillation signal that is the basis of the drive signal for driving the NMOS transistors 22 and 23 , it is possible to realize temperature detection that takes into account heat generated by load fluctuations.

[0135] The above-mentioned embodiments are for facilitating understanding of the present invention, and are not intended to limit the present invention. In addition, the present invention can be changed or improved without departing from the gist thereof, and the present invention naturally includes its equivalents.

[0136] Description of symbols

[0137] 10 Switching power supply circuit

[0138] 11 Load

[0139] 20, 21, 32, 50-53, 102 capacitors

[0140] 22, 23, 104 NMOS transistors

[0141] 24 Transformer

[0142] 25 Control Block

[0143] 30, 31, 56, 91 diodes

[0144] 33 Constant voltage circuit

[0145] 34 LEDs

[0146] 40, 41 Control IC

[0147] 54, 55, 61, 101 resistors

[0148] 57 Photodiode

[0149] 60 Control circuit

[0150] 62 Decision circuit

[0151] 63 Oscillator Circuit

[0152] 64 drive circuit

[0153] 70, 71 Pulse generation circuit

[0154] 80 Detection circuit

[0155] 81 Temperature voltage generation circuit

[0156] 82 Output circuit

[0157] 92 Constant current source

[0158] 93 Switch

[0159] 94 Rise Delay Circuit

[0160] 95 Hysteresis Comparator

[0161] 105 Comparator

[0162] 96 AND Gate Circuit

[0163] 103, 106 Inverter.

Claims

1. A detection circuit, characterized in that: include: a temperature voltage generating circuit, wherein when the pulse signal is at a first level, the temperature voltage generating circuit generates a detection voltage corresponding to the temperature based on a specified current, and when the pulse signal is at a second level, the temperature voltage generating circuit stops generating the detection voltage; as well as an output circuit that outputs a detection signal indicating whether the temperature is higher than a predetermined temperature based on the detection voltage after a predetermined time has passed since the pulse signal changes to the first level and before the pulse signal changes to the second level, The output circuit comprises: a signal output circuit that outputs a prescribed signal after the pulse signal changes to the first level and the prescribed time has passed and before the pulse signal changes to the second level; a comparison circuit that is activated when the pulse signal becomes the first level, compares the detection voltage with a reference voltage corresponding to the specified temperature, and outputs a comparison result; and The logic circuit outputs the comparison result as the detection signal when outputting the prescribed signal.

2. The detection circuit according to claim 1, characterized in that: The temperature voltage generating circuit comprises: A constant current source generating the specified current; a temperature sensing element; and A switch starts to provide the specified current to the temperature detection element when the pulse signal is at the first level, and stops providing the specified current when the pulse signal is at the second level.

3. The detection circuit according to claim 2, characterized in that: The temperature detection element is a diode.

4. The detection circuit according to claim 1, characterized in that: The predetermined time is longer than a first period from when the pulse signal changes to the first level to when the predetermined current is supplied to generate the detection voltage corresponding to the temperature, and a second period from when the pulse signal changes to the first level to when the comparison result is output.

5. A switch control circuit for controlling the switching of a switch element, wherein the switch element controls an inductor current flowing through an inductor of a power supply circuit, wherein the switch control circuit is characterized in that it comprises: a determination circuit for determining whether the load is a light load; an oscillation circuit, the oscillation circuit outputting an oscillation signal, the oscillation signal being used to drive the switch element in a first mode when the load is the light load, and to drive the switch element in a second mode when the load is not the light load; a driving circuit configured to drive the switching element based on the oscillation signal; A pulse generating circuit, the pulse generating circuit generating a pulse signal; a temperature voltage generating circuit, wherein when the pulse signal is at a first level, the temperature voltage generating circuit generates a detection voltage corresponding to the temperature based on a specified current, and when the pulse signal is at a second level, the temperature voltage generating circuit stops generating the detection voltage; as well as an output circuit that outputs a detection signal indicating whether the temperature is higher than a predetermined temperature based on the detection voltage after a predetermined time has passed since the pulse signal changes to the first level and before the pulse signal changes to the second level, When the oscillation circuit receives the detection signal indicating that the temperature is higher than the predetermined temperature, the switching element stops the switching action. The output circuit comprises: a signal output circuit that outputs a prescribed signal after the pulse signal changes to the first level and the prescribed time has passed and before the pulse signal changes to the second level; a comparison circuit that is activated when the pulse signal becomes the first level, compares the detection voltage with a reference voltage corresponding to the specified temperature, and outputs a comparison result; and The logic circuit outputs the comparison result as the detection signal when outputting the prescribed signal.

6. The switch control circuit according to claim 5, characterized in that: The pulse generating circuit generates the pulse signal at a predetermined period.

7. The switch control circuit according to claim 5, characterized in that: The pulse generating circuit generates the pulse signal based on the oscillation signal with a period corresponding to the period of the oscillation signal, In the first mode and the second mode, the pulse signal is generated when the switching element performs the switching operation.

8. A power supply circuit comprising: A transformer having a primary coil disposed on a primary side and a secondary coil disposed on a secondary side; a switching element, the switching element controlling the current of the primary coil; as well as a switch control circuit, the switch control circuit controlling the switch of the switch element, The power supply circuit generates an output voltage of a target level on the secondary side, characterized in that: The switch control circuit comprises: an oscillation circuit, the oscillation circuit outputting an oscillation signal for driving the switching element; a driving circuit configured to drive the switching element based on the oscillation signal; A pulse generating circuit, the pulse generating circuit generating a pulse signal; a temperature voltage generating circuit, which generates a detection voltage corresponding to the temperature based on a specified current when the pulse signal is at a first level, and stops generating the detection voltage when the pulse signal is at a second level; and an output circuit that outputs a detection signal indicating whether the temperature is higher than a predetermined temperature based on the detection voltage after a predetermined time has passed since the pulse signal changes to the first level and before the pulse signal changes to the second level, When the oscillation circuit receives the detection signal indicating that the temperature is higher than the predetermined temperature, the switching element stops the switching action. The output circuit comprises: a signal output circuit that outputs a prescribed signal after the pulse signal changes to the first level and the prescribed time has passed and before the pulse signal changes to the second level; a comparison circuit that is activated when the pulse signal becomes the first level, compares the detection voltage with a reference voltage corresponding to the specified temperature, and outputs a comparison result; and The logic circuit outputs the comparison result as the detection signal when outputting the prescribed signal.

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