JP5633536B2 - Switching control circuit and switching power supply device - Google Patents

Description

  The present invention relates to an IC switching control circuit used for a switching power supply device and a switching power supply device including the same.

  In the switching power supply device, the switching control IC includes circuits for realizing various functions such as output control operation, start-up operation, overcurrent protection operation, overvoltage protection operation, standby operation, and power factor correction operation. As these functions increase, the switching control IC is highly functionalized.

  In order to set each function of the switching control IC so as to correspond to the operation specification of the application, a plurality of terminals for interface with an external circuit are required for each function. For this reason, when the number of functions to be installed increases, the number of terminals naturally increases. As the number of terminals increases, the switching control IC package becomes larger, leading to an increase in the cost of the IC.

  On the other hand, a switching control IC having a small number of terminals is also required in response to a demand for miniaturization of a switching control IC and a reduction in its mounting area. The number of terminals often used as a switching control IC is 16 pins, and 8 pins are the mainstream when it becomes small. A further miniaturized one is a 4-pin.

  When the number of terminals of the switching control IC is limited, the functions that can be mounted are limited. Therefore, it is necessary to prepare different types of ICs according to each function, and to use them properly depending on the specifications and applications. In this case, the number of IC types increases, and not only the manufacturing process but also the management of the IC is complicated, resulting in an increase in the unit cost of the IC.

  In general, it is unavoidable that the size becomes so large that multifunctionality is required, but in recent years, even a small switching control circuit has increased necessary functions. At present, in order to reduce the cost unit cost of semiconductors such as ICs, it is effective to produce a small number of varieties in large quantities. Further, as the IC package, it is possible to reduce the IC cost unit by configuring the IC package as a small IC with a small number of terminals.

Patent Document 1 describes an invention relating to a switching control IC for the purpose of reducing the number of terminals.
FIG. 1 is a circuit diagram of a switching power supply device disclosed in Patent Document 1. In FIG. In FIG. 1, a switching power supply device 101 includes a transformer 105 having a primary winding 127 and a secondary winding 129, a rectifying / smoothing circuit using a diode 117 and a capacitor 119, a feedback circuit using a Zener diode 121, a photocoupler 113, and a resistor 123. And an integrated circuit 103.

  The integrated circuit 103 is connected to the primary winding 127. The integrated circuit 103 is a switching regulator including an internal switch coupled between the drain D terminal and the source S terminal of the integrated circuit 103.

  In operation, a switch in integrated circuit 103 coordinates the transfer of energy from input 107 to output 109 through transformer 105. A feedback signal from the feedback circuit is input to the integrated circuit 103.

  The multifunction capacitor 111 is connected to the bypass BP terminal of the integrated circuit 103. The multi-function capacitor 111 is used to provide the power supply decoupling function of the integrated circuit 103 during normal operation. Internal circuitry within integrated circuit 103 receives power or bias current from multifunction capacitor 111 and operates the circuit during normal operation while regulating output 109.

  A multifunction capacitor 111 is used to select the parameters / modes of the integrated circuit 103 during the initialization period of the integrated circuit 103. During this initialization period, the parameters / modes of the integrated circuit are selected.

Japanese Patent Laid-Open No. 2007-73954

  The switching power supply device disclosed in Patent Document 1 uses a terminal for realizing a necessary function for setting determination of another function during an initialization period. For this purpose, the parameter / mode of the integrated circuit 103 is selected in accordance with the difference in the rate of increase of the charging voltage during the initialization period by setting the capacitance of the multifunction capacitor.

  As described above, in the configuration in which the parameter / mode setting determination of the switching control IC is performed during the initialization period, the selectable functions are greatly limited. Further, since the component for setting the parameter / mode is only the capacitor, the selection function is limited.

  The object of the present invention is to reduce the restrictions on selectable functions compared to the conventional method of setting parameters / modes depending on the rate of increase in the charging voltage of the capacitor, and to make the existing terminals use the functions together (hidden function). Is to provide a switching control circuit and a small and low-cost switching power supply device in which an increase in the number of terminals is suppressed.

A switching control circuit of the present invention is a switching control circuit including a semiconductor integrated circuit that has a plurality of external terminals and is provided in a power conversion circuit of a switching power supply device to control a switching element,
The plurality of external terminals include a power supply terminal for applying a power supply voltage from the outside to the inside, an input terminal for inputting a voltage signal from the outside to the inside, and an output terminal for outputting a voltage signal from the inside to the outside,
At least one external terminal of the plurality of external terminals is a function / external terminal, and the first operation parameter or the first operation mode information of the power conversion circuit is set based on a signal of the function / external terminal. Or first operating state setting means for performing first control of the switching element;
A voltage induced in an external circuit including at least a resistance element or a semiconductor element connected to the outside of the external terminal for both functions is detected as a determination target signal, and a second of the power conversion circuit is detected according to the determination target signal. Second operation state setting means for setting the operation parameter or the second operation mode information,
Is provided inside the semiconductor integrated circuit.

The first operation parameter and the second operation parameter are signals, information, or power that are given to control a predetermined operation. The first operation mode information and the second operation mode information are information for mainly setting the operation mode.
Then, by selectively connecting the external circuit to the external terminal having both functions, the second operation state setting means is set in advance to set the function of the semiconductor integrated circuit, and the semiconductor integrated circuit is integrated into a plurality of types of semiconductor integrated circuits. Select necessary functions from the circuit so that they can be used.

  The switching power supply device according to the present invention includes the switching control circuit in a power conversion circuit.

  According to the present invention, the existing terminal can be used for setting other functions without affecting the function of the normal operation of the existing terminal. Therefore, the number of IC terminals can be reduced, and the size and cost of the IC can be reduced. In addition, by making the IC multifunctional, it can be applied to a power supply having a wide range of specifications and applications.

1 is a circuit diagram of a switching power supply device disclosed in Patent Document 1. FIG. 1 is a circuit diagram of a PFC converter according to a first embodiment. FIG. FIG. 3 is an example of a specific circuit diagram of a drive signal generation circuit 21 shown in FIG. 2. It is a figure which shows the relationship between the waveform of the signal input into the input voltage detection terminal Vdet, and the oscillation frequency of VCO. It is a circuit diagram of the DC-DC converter which concerns on 2nd Embodiment. 3 is a circuit diagram of a feedback circuit 12. FIG. It is a wave form diagram of output terminal OUT and feedback terminal FB of IC for switching control. It is a figure which shows the example of another external circuit connected to the exterior of the feedback terminal FB. FIG. 10 is a block diagram illustrating an internal configuration of a switching control IC 200 provided in a DC-DC converter according to a third embodiment. It is a circuit diagram of the DC-DC converter which concerns on 4th Embodiment. It is a circuit diagram of the DC-DC converter which concerns on 5th Embodiment. It is a circuit diagram of the DC-DC converter which concerns on 6th Embodiment. It is a circuit diagram of the DC-DC converter which concerns on 7th Embodiment. It is a figure which shows the mode of a change of the lower limit of the triangular wave input into a SYNC terminal. It is a circuit diagram of the PFC converter which concerns on 8th Embodiment. It is the figure which represented the internal structure of IC for switching control as a block. It is a circuit diagram of the DC-DC converter which concerns on 9th Embodiment. It is a figure which shows the transition of the operation mode of the DC-DC converter which concerns on 9th Embodiment. It is a circuit diagram of the DC-DC converter which concerns on 10th Embodiment. It is a block diagram which shows the internal structure of IC for switching control with which the DC-DC converter which concerns on 10th Embodiment is equipped. It is a circuit diagram of the DC-DC converter which concerns on 11th Embodiment. It is a block diagram which shows the internal structure of IC for switching control with which the DC-DC converter which concerns on 11th Embodiment is equipped.

  For each embodiment of the present invention, the relationship among the corresponding drawing number, claim number, target terminal name, and function thereof is shown in Tables 1 to 3.

<< First Embodiment >>
FIG. 2 is a circuit diagram of the PFC converter 301 according to the first embodiment.
The PFC converter 301 is an example of the switching control device of the present invention, and includes a switching control IC 201 corresponding to the switching control circuit of the present invention.

  The PFC converter 301 includes input terminals P11 and P12 and output terminals P21 and P22. An AC input power supply Vac, which is a commercial AC power supply, is input to the input terminals P11 to P12, and a load circuit is connected to the output terminals P21 to P22.

  The load circuit is, for example, a DC-DC converter and a circuit of an electronic device that is supplied with power by the DC-DC converter.

  The input stage of the PFC converter 301 is provided with a diode bridge B1 that is a rectifier circuit that full-wave rectifies the AC voltage of the AC input power supply Vac. On the output side of this diode bridge B1, a series circuit of an inductor L1, a switching element Q1, and a current detection resistor R1 is connected. A rectifying and smoothing circuit composed of a diode D1 and a smoothing capacitor C1 is connected in parallel to both ends of the switching element Q1. The inductor L1, the switching element Q1, the diode D1, and the smoothing capacitor C1 constitute a step-up chopper circuit.

The switching control IC 201 includes a power supply terminal VCC, a ground terminal GND, a switching control signal output terminal OUT, an input voltage detection terminal Vdet, a feedback terminal FB, and a current detection terminal IS.
A capacitor C2 for noise removal and voltage stabilization is connected between the power supply terminal VCC and the ground terminal GND of the switching control IC 201.

  Between both ends on the output side of the diode bridge B1, an input voltage detection circuit using resistors R2 and R3 is provided. The output voltage of the input voltage detection circuit is input to the input voltage detection terminal Vdet of the switching control IC 201. An output voltage detection circuit using resistors R4 and R5 is provided between the output terminals P21 and P22. The output voltage of this output voltage detection circuit is input to the feedback terminal FB of the switching control IC 201.

  A resistor R6 is connected between the gate of the switching element Q1 and the output terminal OUT terminal of the switching control IC 201.

  The switching control IC 201 includes a drive signal generation circuit 21 therein. The drive signal generation circuit 21 detects the instantaneous voltage of the AC input power supply based on the input signal of the input voltage detection terminal Vdet. The output voltage is detected by the input signal from the feedback terminal FB. Further, the switching element Q1 is turned on / off at a predetermined switching frequency. This causes the PFC converter 301 to act as a PFC converter.

  FIG. 3 is an example of a specific circuit diagram of the drive signal generation circuit 21 shown in FIG. In FIG. 3, a capacitor Cd and a resistor Rd smooth the voltage at the input voltage detection terminal Vdet. The comparators CMP1 and CMP2 compare the voltage of the capacitor Cd with the reference voltages Vr1 and Vr2, and output a high level or low level signal according to the level relationship. An operational amplifier OP1 and resistors R11, R12, and Ro constitute an adder circuit. The VCO generates a triangular wave signal having a frequency corresponding to the output voltage of the adding circuit.

  The error amplifier EA1 generates an error voltage signal representing an error between the proportional value of the output voltage of the PFC converter and the reference voltage Vr. The multiplier MU multiplies the error voltage signal and the rectified voltage by the diode bridge B1. The diode Dd prevents a backflow from the capacitor Cd to the multiplier MU. The error amplifier EA2 generates an error between the multiplication result by the multiplier MU and the current signal flowing through the diode bridge B1, and outputs the error to the PWM comparator CMP3.

  In the PWM comparator CMP3, the triangular wave signal from the VCO is input to the − terminal, and the signal from the error amplifier EA2 is input to the + terminal. That is, the PWM comparator CMP3 gives the duty pulse corresponding to the current flowing through the diode bridge B1 and the output voltage to the switching element Q1. The duty pulse is a pulse width control signal that continuously compensates for fluctuations in the AC power supply voltage and the DC load voltage at a constant period. With such a configuration, the average value of the current of the inductor L1 is controlled to be similar to the full-wave rectified waveform of the input voltage, and acts as a PFC converter.

  In the first embodiment, the input voltage detection terminal Vdet of the switching control IC 201 is a function / external terminal according to the present invention. Since the control voltage to the VCO changes stepwise according to the voltage of the input voltage detection terminal Vdet, the frequency of the triangular wave signal is switched according to the voltage of the input voltage detection terminal Vdet.

  FIG. 4 is a diagram showing the relationship between the waveform of the signal input to the input voltage detection terminal Vdet and the oscillation frequency of the VCO. When the charging voltage of the capacitor Cd does not exceed Vr1, the oscillation frequency of the VCO is 60 kHz. When the charging voltage of the capacitor Cd exceeds Vr1 and does not exceed Vr2, the oscillation frequency of the VCO is 70 kHz and the charging voltage of the capacitor Cd is In a state exceeding Vr2, the oscillation frequency of the VCO is 80 kHz.

The reference voltages Vr1 and Vr2 of the comparators CMP1 and CMP2 shown in FIG. 3 are determined and the values of the resistors R11, R12, and Ro of the adder circuit are determined so as to satisfy this relationship.
The voltage input to the input voltage detection terminal Vdet changes according to the resistance voltage dividing ratio of the input voltage detection circuit by the resistors R2 and R3 connected to the input voltage detection terminal Vdet. Therefore, the switching frequency can be selected by selecting the value of the resistor R2 or R3 connected to the input voltage detection terminal Vdet. That is, the input voltage detection terminal Vdet serves both as an input terminal for the input voltage waveform to the PFC converter and a setting terminal for the switching frequency.

  It can be similarly applied to a switching control IC having a terminal (Idet) for detecting an inductor current. In other words, the original function of the inductor current detection terminal (Idet) is to input a voltage signal from a circuit for detecting the inductor current, and to compare the average value with a reference voltage (a value corresponding to the average inductor current). The on-time of the switching element is controlled. For example, the switching frequency is switched depending on whether or not the value of the voltage signal input to the inductor current detection terminal (Idet) exceeds a predetermined threshold value.

  In addition to switching the switching frequency, a threshold value at which any of the overcurrent / overload / overvoltage protection operation states can be determined by the peak value of the voltage input to the terminal. Further, a threshold value for shifting from the normal operation to the protective operation and a threshold value for shifting from the protective operation to the normal operation may be determined.

<< Second Embodiment >>
FIG. 5 is a circuit diagram of the DC-DC converter 302 according to the second embodiment.
The DC-DC converter 302 is an example of the switching control device of the present invention, and includes a switching control IC 202 corresponding to the switching control circuit of the present invention.

  The voltage of the DC input power source Vi is input between the input terminals PI (+)-PI (G) of the DC-DC converter 302. Then, a predetermined DC voltage is output to a load connected between the output terminals PO (+) and PO (G) of the DC-DC converter 302.

  A capacitor Cr, an inductor Lr, a primary winding np of the transformer T, a first switching element Q1, and a current detection resistor R7 are connected in series between the input terminals PI (+)-PI (G). The series circuit is configured. The first switching element Q1 is composed of an FET, the drain terminal is connected to the primary winding np of the transformer T, and the source terminal is connected to the current detection resistor R7.

  A second series circuit in which a second switching element Q2, a capacitor Cr, and an inductor Lr are connected in series is configured at both ends of the primary winding np of the transformer T.

  In the secondary windings ns1 and ns2 of the transformer T, a first rectifying and smoothing circuit including diodes Ds and Df and a capacitor Co is configured. The first rectifying / smoothing circuit performs full-wave rectification on the AC voltage output from the secondary windings ns1 and ns2, smoothes it, and outputs it to the output terminals PO (+)-PO (G).

  A rectifying and smoothing circuit including a diode D3 and a capacitor C3 is connected to the drive winding nb of the transformer T. A DC voltage obtained by the rectifying and smoothing circuit is supplied as a power supply voltage between the GND terminal and the VCC terminal of the switching control IC 202.

  The switching control IC 202 outputs a rectangular wave signal from the OUT terminal to the drive circuit 11. The drive circuit 11 alternately controls on / off of the first switching element Q1 and the second switching element Q2. However, a dead time period is provided so that Q1 and Q2 do not turn on simultaneously.

  A resistor R8 is connected to the current detection terminal IS of the switching control IC 202 so that the voltage drop of the current detection resistor R7 is input.

  A feedback circuit 12 is provided between the output terminals PO (+) and PO (G) and the switching control IC 202. The feedback circuit 12 generates a feedback signal by comparing the divided value of the voltage between the output terminals PO (+) and PO (G) with a reference voltage, and feeds back a feedback voltage to the feedback terminal FB of the switching control IC 202 in an insulated state. Is a circuit for inputting.

  A capacitor C4 and a Zener diode D4 are connected between the feedback terminal FB and the ground terminal. The Zener diode D4 is an external circuit that is selectively connected.

  FIG. 6 is a circuit diagram of the feedback circuit 12. Between the output terminals PO (+)-PO (G), a series circuit including a shunt regulator SR, a resistor Rs and a light emitting element of a photocoupler PC and a voltage dividing circuit including resistors Ro1 and Ro2 are connected. Further, a light receiving element of the photocoupler PC is connected between the feedback terminal FB and the ground terminal GND of the switching control IC 202. A constant current circuit is connected to the feedback terminal FB inside the switching control IC 202.

  The feedback circuit 12 operates in such a relationship that the voltage at the feedback terminal FB decreases as the output voltage to the output terminals PO (+) and PO (G) becomes higher than the set voltage.

FIG. 7 is a waveform diagram of the output terminal OUT and the feedback terminal FB of the switching control IC. The internal configuration and operation of the switching control IC 202 in FIG. 5 will be described with reference to FIGS.
The drive signal generation circuit 22 turns on / off the first switching element Q1 and the second switching element Q2 via the drive circuit 11 at a predetermined switching frequency. Thereby, the DC-DC converter 302 operates as a current resonance converter.

  During normal operation other than overcurrent operation, the voltage fed back from the feedback circuit 12 does not exceed the Zener voltage of the Zener diode D4. Therefore, during normal operation, the drive signal generation circuit 22 detects the output voltage from the input signal of the feedback terminal FB, and controls the frequency of the rectangular wave signal output to the output terminal OUT so that this voltage is constant. Thereby, the output voltage of the DC-DC converter 302 is stabilized.

  When the voltage of the feedback terminal FB exceeds 3.3 V over a time exceeding 800 ms, the overcurrent detection circuit 23 regards it as an overcurrent operation state (overload state). After the elapse of 800 ms, the delay circuit 24 turns on the switch SW in the switching control IC 202 to set the voltage at the feedback terminal FB to 0V. As a result, the drive signal generation circuit 22 stops switching of the switching elements Q1, Q2.

  Thereafter, when 3200 ms elapses, the delay circuit 24 turns off the switch SW and releases the voltage of the feedback terminal FB from the 0V clamp. Since the constant current circuit 25 is connected to the feedback terminal FB via the resistor Rc, when the Zener diode D4 is not connected to the feedback terminal FB, the external capacitor C4 rises to the voltage of the power supply voltage terminal VCC of 5.3V. Then, the voltage of the feedback terminal FB exceeds 5V. On the other hand, if, for example, a Zener diode D4 having a Zener voltage of 3.9 V is connected to the feedback terminal FB, the voltage of the feedback terminal FB does not exceed the Zener voltage 3.9 V.

  The return / latch determination circuit 26 detects the voltage of the feedback terminal FB 50 μs after the switch SW is turned off, and stops the drive signal generation circuit 22 when the voltage is higher than 5V. That is, latching is performed while the switching operation is stopped. On the other hand, when the voltage is lower than 5 V, the drive signal generation circuit 22 operates to automatically return to the switching operation state.

  With the above operation, when the Zener diode D4 is not connected to the feedback terminal FB, the latch operation mode is set, and when the Zener diode D4 is connected to the feedback terminal FB, the automatic return operation mode is set.

  For example, if the voltage of the feedback terminal FB is detected and set to operate as follows, the automatic return method and the latch method can be switched.

0.4V to 3.3V: Range of control operation by feedback voltage 3.3V: Range of overcurrent protection operation (automatic return (hiccup) method)
5.0V ~: Range of overcurrent protection operation (latch method)
In this way, it is not necessary to provide two types of switching control ICs, the latch method and the automatic return method, as the overcurrent protection function of the DC-DC converter 302. Therefore, the number of stocks can be reduced, standardization of parts can be promoted, and costs can be reduced.

  In addition, since it is not necessary to have a dedicated IC terminal for switching between the latch method and the automatic return method, it is possible to reduce the size of the IC. Further, by effectively using the terminals of the IC, it is possible to increase the functionality of the IC.

  Further, the latch method and the automatic return method can be switched only by connecting a Zener diode as a peripheral circuit to the terminal of the IC. For this reason, there is no adverse effect on the normal operation of the IC.

  Further, by combining the functions related to the terminals of the IC, the functions can be hidden, and imitation of the IC can be prevented.

FIG. 8 is a diagram illustrating an example of another external circuit connected to the outside of the feedback terminal FB. In the example of FIG. 8, an external circuit including an operational amplifier OP1, a reference voltage generation circuit Vr, a resistor R13, a capacitor C13, and a transistor Q3 is connected to the feedback terminal FB. The operational amplifier OP1, the reference voltage generation circuit Vr, and the transistor Q3 operate as a constant voltage circuit. The resistor R13 and the capacitor C13 act as a filter circuit for preventing malfunction due to a noise component superimposed on the voltage of the feedback terminal FB.
As described above, an active element such as an operational amplifier or a transistor may be provided in the external circuit.

  Note that the present invention can be similarly applied not only in the case of an overcurrent operation but also in the case of selecting switching between an automatic return method and a latch method in an overvoltage state.

<< Third Embodiment >>
FIG. 9 is a block diagram showing the internal configuration of the switching control IC 200 provided in the DC-DC converter according to the third embodiment. This FIG. 9 is also referred to in another embodiment shown later.

  In FIG. 9, when the standby mode is ON (the hidden function of standby mode ON / OFF is performed at the ZT terminal described later), the maximum blanking frequency setting circuit 230 determines the maximum blanking frequency according to the voltage of the feedback terminal FB. Set the ranking frequency. Further, the maximum blanking frequency setting circuit 230 reads the voltage of the feedback terminal FB when starting the converter. Here, a case where the read value is equal to or lower than a predetermined voltage will be described.

  The ZT voltage detection circuit 226 detects that the voltage of the drive winding nb of the transformer T has been inverted based on the voltage of the ZT terminal and gives a trigger to the one-shot circuit 240. The maximum blanking frequency setting circuit 230 By setting the output to the low level, the output of the AND gate 231 becomes the low level, the blanking time during which the OUT terminal maintains the low level is determined, and as a result, the switching frequency is determined.

  When the feedback terminal FB voltage exceeds 1 V, the upper limit frequency is, for example, 250 kHz, and a switching frequency equal to or lower than this frequency is determined according to the voltage of the feedback terminal FB. When the voltage of the feedback terminal FB is 1 V or less, the switching frequency is set to 250 kHz or less, which is the upper limit frequency, according to the blanking time. In this embodiment, the voltage of the feedback terminal FB is 0.4 V and 1 kHz.

  When the voltage at the feedback terminal FB is 1 V or less, the maximum blanking frequency setting circuit 230 in FIG. 9 determines the voltage at the feedback terminal FB from 1 V to 0.4 V according to the blanking time. The blanking frequency is set so as to change linearly from 250 kHz to 1 kHz. For this reason, the load becomes lighter, and the switching frequency decreases as the voltage at the feedback terminal FB decreases, so that a standby mode for reducing the switching frequency is set. As a result, it is possible to cope with a reduction in loss at a light load.

On the other hand, when the maximum blanking frequency setting circuit 230 reads the voltage of the feedback terminal FB at the time of starting the converter, it is as follows.
In FIG. 9, when the voltage of the feedback terminal FB is 1 V or less, the maximum blanking frequency setting circuit 230 causes an oscillation period in which oscillation continues for a change from 1 V to 0.4 V in the voltage of the feedback terminal FB. The ratio of the stop period during which the switching operation stops is changed, and the ratio of the oscillation period is set to change linearly from 1 to 0. For this reason, as the load becomes lighter and the voltage at the feedback terminal FB decreases, the ratio of the oscillation period decreases and the intermittent oscillation standby mode is set. As a result, it is possible to cope with a reduction in loss at a light load.

<< Fourth Embodiment >>
FIG. 10 is a circuit diagram of a DC-DC converter 304 according to the fourth embodiment.
The DC-DC converter 304 is an example of the switching control device of the present invention, and includes a switching control IC 200 corresponding to the switching control circuit of the present invention.

  The voltage of the DC input power source Vi is input between the input terminals PI (+)-PI (G) of the DC-DC converter 304. Then, a predetermined DC voltage is output to a load connected between the output terminals PO (+)-PO (G) of the DC-DC converter 304.

  The difference from the switching power supply device of the second embodiment shown in FIG. 5 is that the configuration of the switching control IC 200 and an external circuit by a resistor Rss and a capacitor Css are connected between the soft start terminal SS and the ground GND. This is the point.

  In FIG. 10, the original function of the soft start terminal SS of the switching control IC 200 is a terminal for performing a soft start operation. Soft start is control that gradually increases the ON width of the output pulse for driving the switching elements Q1 and Q2 when the converter is started. The soft start speed is set by the time constant of the external circuit connected to the soft start terminal SS. Specifically, a constant current circuit is connected inside the soft start terminal SS, and a charging time constant for the capacitor Css is determined by the capacity of an external capacitor Css with respect to the soft start terminal SS.

  The internal configuration of the switching control IC 200 is as shown in FIG. In FIG. 9, when the one-shot circuit 240 sets the flip-flop 213, the Q output signal of the flip-flop 213 is output as a high-level gate control voltage to the OUT terminal via the AND gate 214 and the driver 215.

The CT generator circuit 241 outputs the ramp waveform voltage after the output of the AND gate 214 becomes high level. The comparator 212 resets the flip-flop 213 when the output voltage of the CT generator circuit 241 exceeds the lowest voltage among the voltages input to the three (−) terminals. As a result, the voltage at the OUT terminal is returned to the low level.
By repeating the above, the output voltage of the OUT terminal is changed to a rectangular wave shape.

  A constant current circuit CCC1 is connected to the soft start terminal SS. As shown in FIG. 10, by connecting the capacitor Css to the soft start terminal SS, the voltage of the soft start terminal SS becomes equal to the charging voltage of the capacitor Css. As the voltage of the soft start terminal SS rises, the timing at which the output of the comparator 212 is inverted is delayed, and the ON time of the switching element is gradually increased. This causes a soft start operation.

  As shown in FIG. 10, by externally attaching a resistor Rss to the soft start terminal SS, the voltage of the soft start terminal SS is determined according to the resistance value of the resistor Rss when the capacitor Css is fully charged.

  During the soft start period, among the voltages input to the three (−) terminals of the comparator 212, the output voltage of the resistance voltage dividing circuit 216 is the lowest, so the soft start operation is performed as described above. When the soft start operation is completed, the output voltage of the resistance voltage dividing circuit 224 becomes the lowest state among the voltages input to the three (−) terminals of the comparator 212. Therefore, switching is performed according to the voltage applied to the feedback terminal FB. The on-time of the element is determined. When the voltage of the feedback terminal FB exceeds the voltage applied to the SS terminal determined by the resistance value of the external resistor Rss (voltage value of 3.3 V or less in the resistance voltage dividing circuit 225), the comparator 212 Since the voltage applied to the SS terminal is the lowest among the voltages input to the three (−) terminals, the on-time is controlled not to be longer than that, and the maximum on-time or the maximum A duty ratio is set.

  The first overcurrent protection selection circuit 217 uses, for example, 4V as a threshold value, and if the voltage of the soft start terminal SS exceeds 4V, the first overcurrent detection circuit 222 is activated by enabling the AND gate 218. Enable output. The first overcurrent detection circuit 222 sets the output to a high level when the voltage at the IS terminal exceeds 0.3 V, and starts the timer operation of the overcurrent protection timer 219. The overcurrent protection timer 219 causes the timer latch 221 to be latched via the OR gate 220 when the output of the first overcurrent detection circuit 222 becomes high level and continues for 50 ms. The timer latch 221 stops switching of the switching element for 3.2 s. Thus, the first overcurrent protection is performed.

  With the above configuration, the maximum on-time or the maximum time ratio is set by the resistance value of the external resistor Rss.

  Note that, when the overcurrent state becomes so large that the voltage at the IS terminal exceeds 0.4V, the output of the second overcurrent detection circuit 223 becomes high level, and the switching operation is forcibly stopped.

<< Fifth Embodiment >>
FIG. 11 is a circuit diagram of a DC-DC converter 305 according to the fifth embodiment.
The DC-DC converter 305 is an example of the switching control device of the present invention, and includes a switching control IC 200 corresponding to the switching control circuit of the present invention.

  The voltage of the DC input power source Vi is input between the input terminals PI (+)-PI (G) of the DC-DC converter 305. Then, a predetermined DC voltage is output to a load connected between the output terminals PO (+)-PO (G) of the DC-DC converter 305.

  The difference from the switching power supply of the second embodiment shown in FIG. 5 is the configuration of the switching control IC 200 and the point that an external circuit is connected between the polarity detection terminal ZT and the ground GND by a capacitor Cz. .

  Usually, the polarity detection terminal ZT is used to detect that the polarity of the winding voltage of the transformer T is reversed. A signal input from the drive winding nb of the transformer T to the polarity detection terminal ZT is an ON / OFF pulse voltage. This is based on polarity reversal of the winding voltage.

  Here, the voltage peak value of the pulse voltage input to the polarity detection terminal ZT is set by determining the turn ratio between the primary winding np and the drive winding nb of the transformer T or providing a resistance voltage dividing circuit. Is done.

  As shown in FIG. 9, a ZT voltage detection circuit 226 is connected to the ZT terminal of the switching control IC 200. The ZT voltage detection circuit 226 detects that the voltage of the drive winding nb of the transformer T has been inverted based on the voltage at the ZT terminal, and gives a trigger to the one-shot circuit 240.

  A standby mode selection circuit 227 is connected to the ZT terminal of the switching control IC 200. The standby mode selection circuit 227 stops the output signal from the OUT terminal by outputting a low level signal to the AND gate 229 if the voltage at the ZT terminal is equal to or higher than a threshold value (eg, 3.3 V). . Thus, the standby mode is set. If it is less than 3.3V, the standby mode is canceled.

  Further, since the signal input to the polarity detection terminal ZT is a pulse signal, the standby mode may be turned ON when 4 pulses of 3.3V or more are counted. As a result, malfunction due to noise can be prevented.

<< Sixth Embodiment >>
FIG. 12 is a circuit diagram of a DC-DC converter 306 according to the sixth embodiment.
The DC-DC converter 306 is an example of the switching control device of the present invention, and includes a switching control IC 200 corresponding to the switching control circuit of the present invention.

  In the DC-DC converter according to the sixth embodiment, the IS terminal of the switching control IC 200 has a function other than current detection (overcurrent detection).

  The internal configuration of the switching control IC 200 is as shown in FIG. In FIG. 9, the second overcurrent detection circuit 223 connected to the IS terminal performs overcurrent protection when the voltage at the IS terminal becomes a voltage corresponding to the overcurrent state. The Q1 off-time voltage detection circuit 228 detects whether or not the voltage at the IS terminal exceeds a threshold value when the switching element Q1 is off, and operates the second function.

  In FIG. 9, when the voltage of the IS terminal becomes an overcurrent state exceeding 0.4V, the output of the second overcurrent detection circuit 223 becomes high level and the switching operation is forcibly stopped.

  A constant current circuit CCC2 and a resistor R228 are connected to the IS terminal. When the switching element Q1 is in the OFF state, a current flows through the internal resistor R228 and the external resistors R8 and R7. Therefore, the voltage at the IS terminal is a voltage drop across the resistors R7 and R8.

  The Q1 off-time voltage detection circuit 228 receives the output signal Szt of the ZT voltage detection circuit 226 as a timing signal, and compares the voltage at the IS terminal with a threshold value during a period in which Q1 is off. For example, when the threshold value is exceeded, a high level is output to the AND gate 218 to enable the first overcurrent protection mode.

  Therefore, by determining the resistance value of one or both of the external resistors R8 and R7, the state of the Q1 off-time voltage detection circuit 228 can be determined.

  Similarly, the present invention can be similarly applied to a switching control IC having an overvoltage protection terminal (OVP). The original function of the overvoltage protection terminal (OVP) is to detect that the output voltage to the load has become an overvoltage and suppress the increase in the output voltage. When the terminal voltage of the overvoltage protection terminal (OVP) exceeds a set voltage that is higher than the normal range, a circuit that holds the OUT terminal at a low level and immediately stops the output of the overvoltage is provided in the switching control IC. Provide.

<< Seventh Embodiment >>
FIG. 13 is a circuit diagram of a DC-DC converter 307 according to the seventh embodiment.
The DC-DC converter 307 is an example of the switching control device of the present invention, and includes a switching control IC 207 corresponding to the switching control circuit of the present invention.

  In the DC-DC converter according to the seventh embodiment, the SYNC terminal of the switching control IC 207 has a function other than the oscillation synchronization function.

  A frequency synchronization signal is input from the synchronization signal generation circuit 13 to the SYNC terminal. In this example, a triangular wave is input. The internal oscillation circuit 27 oscillates in synchronization with the peak of the triangular wave. The switching element Q1 is turned on at the rising edge of the rectangular wave signal output from the oscillation circuit 27, and the switching element Q2 is controlled to be turned on after a predetermined on-time has elapsed.

  The internal selection circuit 28 selects validity / invalidity of other functions depending on whether or not the lower limit value of the voltage (triangular wave signal) input to the SYNC terminal exceeds a predetermined threshold value. For example, ON / OFF of the standby mode is selected. If the lower limit value is equal to or higher than the threshold voltage, the selection circuit 28 enables the standby mode operation circuit 29. The standby mode operation circuit 29 performs the standby mode operation as shown in the third embodiment when the FB voltage at the time of light load is low.

  FIG. 14 is a diagram illustrating a change in the lower limit value of the triangular wave input to the SYNC terminal. Since the lower limit value of the triangular wave (1) exceeds the threshold voltage Vth, the standby mode becomes effective. Further, since the lower limit value of the triangular wave (2) does not reach the threshold voltage Vth, the standby mode is invalidated.

  The lower limit voltage of the triangular wave input to the SYNC terminal is determined by the resistance values of the external resistors R9 and R10. That is, ON / OFF of the standby mode is selected according to the resistance values of the external resistors R9 and R10.

  In addition, you may comprise so that another function may be selected according to the frequency band of the triangular wave of a SYNC terminal. For example, the selection circuit 28 shown in FIG. 13 counts the period of the triangular wave with a clock and selects another function depending on whether or not the count value exceeds a threshold value.

  Other functions are not limited to ON / OFF selection in the standby mode, but may be configured to select, for example, latch / automatic return during protection operation.

<< Eighth Embodiment >>
FIG. 15 is a circuit diagram of a PFC converter 308 according to the eighth embodiment.
The switching control device 308 includes a switching control IC 208 corresponding to the switching control circuit of the present invention.

  The switching control device 308 includes a step-up chopper circuit including a diode bridge DB, a switching element Q1, a diode D1, and a capacitor Co. The switching control IC 208 receives the detection voltage from the output voltage detection circuit by the resistors R21 and R22 at the feedback terminal FB, and performs on / off control of the switching element Q1 with a rectangular wave signal output from the OUT terminal. The COMP terminal is connected to an external resistor R24 and a capacitor C24 for compensating the feedback gain and phase.

FIG. 16 is a block diagram showing the internal configuration of the switching control IC 208.
In order to stabilize the output voltage, an error amplifier 411 that amplifies the difference between the voltage of the output voltage detection signal input to the feedback terminal FB and the reference voltage is provided in the switching control IC 208. The COMP terminal is connected to the output of the error amplifier 411, and the gain of the error amplifier 411 and the phase of the output signal are set by a resistor R24 and a capacitor C24 externally attached to the COMP terminal.

  A standby mode operation circuit 412 is connected to the COMP terminal. A constant current circuit CCC3 is connected via the switch 413. The switch 413 is turned on at startup. The standby mode operation circuit 412 enters a standby mode if the voltage at the COMP terminal is equal to or higher than a predetermined threshold voltage. That is, the output of the rectangular wave from the OUT terminal is stopped.

<< Ninth embodiment >>
FIG. 17 is a circuit diagram of a DC-DC converter 309 according to the ninth embodiment.
The DC-DC converter 309 includes a switching control IC 209 corresponding to the switching control circuit of the present invention.

  The voltage of the DC input power source Vi is input between input terminals PI (+)-PI (G) of the DC-DC converter 309. Then, a predetermined DC voltage is output to a load connected between the output terminals PO (+)-PO (G) of the DC-DC converter 309.

  A capacitor Cr, an inductor Lr, a primary winding np of the transformer T, a first switching element Q1, and a current detection resistor R7 are connected in series between the input terminals PI (+)-PI (G). The series circuit is configured. The first switching element Q1 is composed of an FET, the drain terminal is connected to the primary winding np of the transformer T, and the source terminal is connected to the current detection resistor R7.

  A second series circuit in which a second switching element Q2, a capacitor Cr, and an inductor Lr are connected in series is configured at both ends of the primary winding np of the transformer T.

  In the secondary windings ns1 and ns2 of the transformer T, a first rectifying and smoothing circuit including diodes Ds and Df and a capacitor Co is configured. The first rectifying / smoothing circuit performs full-wave rectification on the AC voltage output from the secondary windings ns1 and ns2, smoothes it, and outputs it to the output terminals PO (+)-PO (G).

  A rectifying and smoothing circuit including a diode D3 and a capacitor C3 is connected to the first drive winding nb of the transformer T. A DC voltage obtained by the rectifying and smoothing circuit is supplied as a power supply voltage between the GND terminal and the VCC terminal of the switching control IC 209.

  The switching control IC 209 outputs a rectangular wave signal from the OUT terminal to the drive circuit 11. The drive circuit 11 alternately controls on / off of the first switching element Q1 and the second switching element Q2. However, a dead time period is provided so that Q1 and Q2 do not turn on simultaneously.

  A resistor R8 is connected to the current detection terminal IS of the switching control IC 209 so that the voltage drop of the current detection resistor R7 is input.

  A feedback circuit 12 is provided between the output terminals PO (+) and PO (G) and the switching control IC 202. The feedback circuit 12 generates a feedback signal by comparing the divided value of the voltage between the output terminals PO (+) and PO (G) with a reference voltage, and feeds back a feedback voltage to the feedback terminal FB of the switching control IC 202 in an insulated state. Is a circuit for inputting.

  The configuration of the feedback circuit 12 is the same as that shown in FIG. 6 in the second embodiment. The feedback circuit 12 operates in such a relationship that the voltage at the feedback terminal FB decreases as the output voltage to the output terminals PO (+) and PO (G) becomes higher than the set voltage.

  In the switching control IC 209, a drive signal generation circuit 22 that generates a drive signal corresponding to the feedback signal input to the feedback terminal FB is provided in order to stabilize the output voltage. Further, a control system selection circuit 30 is provided that detects the voltage of the feedback signal input to the feedback terminal FB and selects a control system based on the voltage. For example, if the voltage of the feedback signal input to the feedback terminal FB is a voltage corresponding to the normal load, the control method selection circuit 30 controls the drive signal generation circuit 22 to operate in the constant voltage control mode. If the voltage at the feedback terminal FB is a voltage corresponding to an overload, the control method selection circuit 30 controls the drive signal generation circuit 22 to operate in the constant power control mode. Further, if overload occurs, the mode shifts to the constant current control mode.

  FIG. 18 is a diagram showing the transition of the operation mode. If the output current is in the range of 0 to Id, constant voltage control is performed so that the output voltage maintains a constant voltage Vc. Constant power control is performed so that the output power is constant when the output current is in the range of Id to Ic. When the output voltage reaches Vd and the output current reaches Ic, constant current control is performed so that the output current becomes a constant current Ic.

  When the output current fluctuates in the range of 0 to Id, the output voltage is maintained at Vc if the voltage (voltage of the feedback signal) input to the feedback terminal FB is in the range of 0.4V to 3.3V. If the voltage of the feedback terminal FB exceeds 3.3V, that is, if the output current exceeds Id, the maximum on-time is limited, the output power is limited to a constant value, and the output voltage is suppressed. When the voltage at the feedback terminal FB exceeds 3.5 V, the on-time is controlled to be reduced so that the output current is kept at Ic.

<< Tenth Embodiment >>
FIG. 19 is a circuit diagram of a DC-DC converter 310 according to the tenth embodiment.
The DC-DC converter 310 is an example of the switching control device of the present invention, and includes a switching control IC 210 corresponding to the switching control circuit of the present invention.

  The voltage of the DC input power source Vi is input between the input terminals PI (+)-PI (G) of the DC-DC converter 310. Then, a predetermined DC voltage is output to a load connected between the output terminals PO (+)-PO (G) of the DC-DC converter 310.

  Between the input terminals PI (+)-PI (G), the primary winding np of the transformer T, the switching element Q1, and the current detection resistor R7 are connected in series. The switching element Q1 is composed of an FET, the drain terminal is connected to the primary winding np of the transformer T, and the source terminal is connected to the current detection resistor R7.

  A rectifying / smoothing circuit including a diode Ds and a capacitor Co is configured in the secondary winding ns of the transformer T. This rectifying / smoothing circuit performs full-wave rectification on the AC voltage output from the secondary winding ns, smoothes it, and outputs it to the output terminals PO (+)-PO (G).

  A rectifying and smoothing circuit including a diode D3 and a capacitor C3 is connected to the first drive winding nb of the transformer T. A DC voltage obtained by this rectifying / smoothing circuit is supplied as a power supply voltage between the GND terminal and the VC terminal of the switching control IC 210.

  The switching control IC 210 outputs a rectangular wave signal from the OUT terminal to the switching element Q1.

  A voltage drop of the current detection resistor R7 is input to the current detection terminal IS of the switching control IC 210.

  A feedback circuit is provided between the output terminals PO (+) and PO (G) and the switching control IC 210. This feedback circuit is connected between a series circuit including a shunt regulator SR, a resistor Rs, and a light emitting element of a photocoupler PC, a voltage dividing circuit including resistors Ro1 and Ro2, and a feedback terminal FB and a ground terminal GND of the switching control IC 210. And a light receiving element of the photocoupler PC.

FIG. 20 is a block diagram showing an internal configuration of the switching control IC 210 provided in the DC-DC converter according to the tenth embodiment.
In FIG. 20, the output signal of the oscillation circuit 512 is output from the OUT terminal via an AND gate 513 and an output driver 514. When the comparator 511 detects that the voltage at the OUT terminal is equal to or higher than a predetermined value, the comparator 511 outputs a control signal to the oscillation circuit 512 to switch the switching frequency. For example, when the voltage at the OUT terminal is equal to or higher than a predetermined value, the switching frequency is lowered by 10 kHz as compared with the case where the voltage is lower than the predetermined value.

  Therefore, an external circuit may be connected to the OUT terminal, and the circuit may be configured to change the voltage at the OUT terminal by switching the external circuit. The switching frequency can be selected by switching the external circuit.

  Since the voltage at the OUT terminal is determined by the power supply voltage applied to the output driver 514, the power supply voltage may be switched by an external circuit connected to another terminal. In addition, the switching frequency is not limited to be selected by the voltage at the OUT terminal as described above, but the switching frequency may be selected by the voltage at another terminal. For example, when the switching frequency is selected according to the voltage applied to the power supply terminal VC, a comparator is provided for detecting whether or not a predetermined threshold voltage is exceeded within the input voltage specification range. The control signal is supplied to the oscillation circuit 512 by the output of

  Similarly, the switching frequency selection function can be configured in the same manner at the ON / OFF terminals. Furthermore, the switching frequency selection function can be configured similarly at the Valm terminal.

  In FIG. 20, the notation of the ON / OFF terminal and the Valm terminal is omitted. The ON / OFF terminal is a terminal having a function of stopping the output of a pulse from the OUT terminal by lowering the ON / OFF terminal potential to the ground level. The Valm terminal is a terminal capable of notifying that the operation of the power supply is abnormal by raising the potential of the Valm terminal to a high level, for example, when the operation of the IC is in an overvoltage state or an overcurrent state. It is.

<< Eleventh Embodiment >>
FIG. 21 is a circuit diagram of a DC-DC converter 311 according to the eleventh embodiment.
The DC-DC converter 311 is an example of the switching control device of the present invention, and includes a switching control IC 211 corresponding to the switching control circuit of the present invention.

  The voltage of the DC input power source Vi is input between the input terminals PI (+)-PI (G) of the DC-DC converter 311. Then, a predetermined DC voltage is output to a load connected between the output terminals PO (+)-PO (G) of the DC-DC converter 311.

  Between the input terminals PI (+)-PI (G), the primary winding np of the transformer T, the switching element Q1, and the current detection resistor R7 are connected in series. The switching element Q1 is composed of an FET, the drain terminal is connected to the primary winding np of the transformer T, and the source terminal is connected to the current detection resistor R7.

  A rectifying / smoothing circuit including a diode Ds and a capacitor Co is configured in the secondary winding ns of the transformer T. This rectifying / smoothing circuit performs full-wave rectification on the AC voltage output from the secondary winding ns, smoothes it, and outputs it to the output terminals PO (+)-PO (G).

  A rectifying and smoothing circuit including a diode D3 and a capacitor C3 is connected to the first drive winding nb of the transformer T. A DC voltage obtained by this rectifying / smoothing circuit is supplied as a power supply voltage between the GND terminal and the VC terminal of the switching control IC 210.

  The switching control IC 211 outputs a rectangular wave signal from the OUT terminal to the switching element Q1.

  A voltage drop of the current detection resistor R7 is input to the current detection terminal IS of the switching control IC 211.

A feedback circuit is provided between the output terminals PO (+) and PO (G) and the switching control IC 211. This feedback circuit is connected between a series circuit including a shunt regulator SR, a resistor Rs, and a light emitting element of a photocoupler PC, a voltage dividing circuit including resistors Ro1 and Ro2, and a feedback terminal FB and a ground terminal GND of the switching control IC 210. And a light receiving element of the photocoupler PC.
An external circuit composed of the VC voltage detection circuit 14 and the transistor Q4 is connected to the VREF terminal.

FIG. 22 is a block diagram showing an internal configuration of the switching control IC 211 provided in the DC-DC converter according to the eleventh embodiment.
In FIG. 22, the first function of the VREF terminal is to output a reference voltage to the outside. The second function of the VREF terminal is a function for selecting whether to perform a latch operation or an automatic return when an overcurrent is detected.

  The selection circuit 515 reads the voltage at the VREF terminal when a startup signal is output from the startup circuit 517. If this voltage exceeds a predetermined threshold value, the overcurrent automatic recovery circuit is enabled, and if it is less than the threshold value, the overcurrent latch circuit is enabled.

  For example, the operation start voltage of the switching control IC 211 is 10V, and the rated voltage is 15V. When the VREF terminal voltage immediately after startup is detected, the VC terminal voltage at this time is around 10V. The VC voltage detection circuit 14 shown in FIG. 21 turns on the transistor Q4 when the VC terminal voltage is 12 V or less. Therefore, when the VC terminal voltage is 12 V or less, the VREF terminal is at the GND potential. Immediately after startup, the voltage at the VC terminal is around 10 V, so the VREF terminal is at the GND potential and the automatic return mode is selected. If the external circuit is not connected to the VREF terminal, the reference voltage is output to the VREF terminal even immediately after activation of the switching control IC 211, so that the latch operation mode is selected. In other words, either the latch operation mode or the automatic return mode can be selected depending on the presence or absence of an external circuit.

<< Other embodiments >>
Although several types of converters have been described in the embodiments described above, the primary side of the converter is not limited to the current resonance type. The secondary side may be a forward type other than the flyback type. Also, it can be applied to a half bridge type, a full bridge type, and the like.

OUT ... output terminals Q1, Q2 ... switching elements Q3, Q4 ... transistor SR ... shunt regulator SS ... soft start terminal SW ... switch T ... transformer Vdet ... input voltage detection terminal ZT ... polarity detection terminal 11 ... drive circuit 12 ... feedback circuit 13 ... Synchronization signal generation circuit 14 ... VC voltage detection circuits 21, 22 ... Drive signal generation circuit 23 ... Overcurrent detection circuit 24 ... Delay circuit 25 ... Constant current circuit 26 ... Latch discrimination circuit 27 ... Oscillation circuit 28 ... Selection circuit 29 ... Standby Mode operation circuit 30... Control system selection circuit 200 to 202... Switching control IC
204 ... IC for switching control
207 to 211 ... IC for switching control
227 ... Standby mode selection circuit 301, 302 ... PFC converters 304 to 311 ... DC-DC converter

Claims (33)

A switching control circuit comprising a semiconductor integrated circuit having a plurality of external terminals and provided in a power conversion circuit of a switching power supply device to control a switching element,
The semiconductor integrated circuit is an analog semiconductor integrated circuit having no program function,
The plurality of external terminals include a power supply terminal for applying a power supply voltage from the outside to the inside, an input terminal for inputting a voltage signal from the outside to the inside, and an output terminal for outputting a voltage signal from the inside to the outside,
At least one external terminal of the plurality of external terminals is a function / external terminal, and the first operation parameter or the first operation mode information of the power conversion circuit is set based on a signal of the function / external terminal. Or first operating state setting means for performing first control of the switching element;
A voltage induced in an external circuit including at least a resistance element or a semiconductor element connected to the outside of the external terminal for both functions is detected as a determination target signal, and a second of the power conversion circuit is detected according to the determination target signal. Second operation state setting means for setting the operation parameter or the second operation mode information,
In the semiconductor integrated circuit ,
In the first operation state setting means, the normal circuit operation of the power conversion circuit is set,
In the second operating state setting means, by Rukoto selectively the external circuit is connected to the functional multiplexed external pin, the function of selectively the semiconductor integrated circuit is set in advance from the provided functions,
The semiconductor integrated circuit can be used by selecting a function necessary for the power conversion circuit, so that the function set by the second operation state setting means can be adapted to each power conversion circuit. A switching control circuit. One of the signals input to the function / external terminal is an output voltage detection signal input from the power conversion circuit by the operation of the switching control circuit,
The first operation state setting means sets an operation parameter for output voltage stabilization control according to the output voltage detection signal,
The second operation state setting means is configured to output the second operation parameter or the second parameter other than stabilization of the output voltage according to the determination target signal in a period other than the power conversion operation of the power conversion circuit. The switching control circuit according to claim 1, wherein setting of operation mode information or second control of the switching element is performed. One of the signals input to the function combined external terminal is a current detection signal generated by a current flowing through the power conversion circuit due to the operation of the switching control circuit,
The first operation state setting means sets an operation parameter or an operation mode for overcurrent control according to the current detection signal,
The second operation state setting unit is configured to convert the power conversion other than the overcurrent control according to the determination target signal in a period unnecessary for the operation of the power conversion circuit in an on period or an off period of the switching element. 2. The switching control circuit according to claim 1, wherein setting of a second operation parameter or second operation mode information of the circuit or second control of the switching element is performed. One of the signals input to the function / external terminal is a waveform signal of the input power supply voltage,
The first operating state setting means performs a first control of the switching element according to the waveform signal,
The said 2nd operation state setting means sets the switching frequency of the said switching element of the said power converter circuit according to the comparison result of the voltage peak value of the said determination object signal, and a reference voltage. Switching control circuit. One of the signals input to the function / external terminal is a frequency setting signal that determines the frequency of the voltage pulse output from the output terminal in order to operate the switching control circuit,
The first operating state setting means determines the frequency of the voltage pulse output from the external terminal for both functions according to the voltage maximum value of the frequency setting signal,
The second operation state setting means includes the second operation parameter or the second operation mode information other than the operation for determining the frequency according to a comparison result between the minimum voltage value of the determination target signal and a reference voltage. The switching control circuit according to claim 1, wherein setting or second control of the switching element is performed. One of the signals input to the function / external terminal is a pulse width setting signal that determines a pulse width of a voltage pulse output from the output terminal to operate the switching control circuit,
The first operation state setting means determines the pulse width of the voltage pulse output from the function / external terminal according to the pulse width setting signal in the startup time from the start of operation of the power conversion circuit to the steady operation. Set
The second operation state setting means is configured to set the second operation parameter or the second operation mode information other than the setting of the pulse width according to the determination target signal during the steady operation of the power conversion circuit. Alternatively, the switching control circuit according to claim 1, wherein the second control of the switching element is performed. One of the signals input to the function / external terminal is a voltage pulse output control signal that determines the start or stop of the voltage pulse output from the function / external terminal in order to operate the switching control circuit. ,
The first operation state setting means determines the start or stop of a voltage pulse output from the function-external terminal according to the voltage pulse output control signal,
The switching control circuit according to claim 1, wherein the second operation state setting means sets a switching frequency of the switching element in accordance with the determination target signal. One of the signals input to the function combined external terminal is an overvoltage detection signal indicating whether or not the voltage output from the power conversion circuit is an overvoltage,
The first operation state setting means performs an overvoltage protection operation according to the overvoltage detection signal,
2. The switching according to claim 1, wherein the second operation state setting unit immediately stops the output of an overvoltage in response to the determination target signal when the overvoltage detection signal exceeds a set voltage higher than a normal range. Control circuit. One of the signals input to the function combined external terminal is a compensation signal for compensating the gain and phase of the feedback signal voltage output from the power conversion circuit by the operation of the switching control circuit,
The first operating state setting means compensates the gain and phase of the feedback signal voltage according to the compensation signal,
The second operation state setting means is configured to output a feedback signal voltage corresponding to the compensation signal in accordance with the determination target signal before starting the operation of the power conversion circuit or in a startup time from the operation start to the steady operation. 2. The switching control circuit according to claim 1, wherein the switching control circuit performs setting of the second operation parameter or second operation mode information other than gain and phase compensation or second control of the switching element. One of the signals input to the function / external terminal is a polarity inversion timing indicating that the polarity of the current flowing through the inductor or transformer of the power conversion circuit or the voltage generated is changed by the operation of the switching control circuit. Signal,
The first operation state setting means controls the switching control circuit according to the polarity inversion timing signal,
The second operation state setting means includes a second operation parameter other than the control of the switching control circuit according to the polarity inversion timing signal according to a comparison result between the voltage peak value of the determination target signal and a reference voltage. The switching control circuit according to claim 1, wherein setting of second operation mode information or second control of the switching element is performed. The signal output from the external terminal for both functions is a switching element control signal for controlling the voltage of the control terminal of the switching element in order to operate the switching control circuit,
The first operation state setting means provides the switching element control signal to the switching element,
The switching control circuit according to claim 1, wherein the second operation state setting unit sets a switching frequency of the switching element in accordance with the determination target signal. The signal output from the external terminal for both functions is a reference voltage signal generated for operating the switching control circuit,
The first operating state setting means outputs the reference voltage signal;
The second operation state setting means sets the second operation parameter or second operation mode information other than the output of the reference voltage signal according to the determination target signal before the operation of the power conversion circuit is started. The switching control circuit according to claim 1, wherein the switching control circuit performs second control of the switching element. The signal output from the function / external terminal is an operation state signal indicating whether or not the operation state of the power conversion circuit is normal,
The first operation state setting means outputs the operation state signal;
The switching control circuit according to claim 1, wherein the second operation state setting unit sets a switching frequency of the switching element in accordance with the determination target signal.   The switching control circuit according to claim 1, further comprising a current supply circuit therein, wherein the current supply circuit supplies current to the function / external terminal to which the external circuit is connected.   The switching control circuit according to claim 1, wherein the semiconductor element is a Zener diode.   The switching control circuit according to claim 1, wherein the semiconductor element is a transistor.   The switching control circuit according to claim 1, wherein the semiconductor element is an operational amplifier.   The switching control circuit according to claim 1, wherein the second operating parameter is a switching frequency of the switching element.   The switching control circuit according to claim 1, wherein the second operation parameter is a limit value of a maximum value or a minimum value of a switching frequency of the switching element.   The second operation parameter is a threshold value for determining an overload state based on an overcurrent detection signal generated by a current flowing through the power conversion circuit due to an operation of the switching control circuit. The switching control circuit according to any one of the above.   The second operation parameter is a threshold value for determining an overvoltage state based on an overvoltage detection signal indicating whether or not the voltage output from the power conversion circuit is an overvoltage. A switching control circuit according to claim 1.   The switching control circuit according to claim 1, wherein the second operation parameter is a start threshold value for determining start of the power conversion circuit or a stop threshold value for determining stop of the power conversion circuit.   The switching control circuit according to claim 1, wherein the second operation parameter is a limit value of an on-time of the switching element.   The switching control circuit according to claim 1, wherein the second operation parameter is a limit value of a time ratio of a pulse for driving the switching element.   The switching control circuit according to any one of claims 1 to 17, wherein the second operation mode information is information relating to an output control method of the power conversion circuit.   18. The switching control circuit according to claim 1, wherein the second operation mode information is information relating to an operation mode distinction in an overload state.   18. The switching control circuit according to claim 1, wherein the second operation mode information is information relating to an operation mode distinction in an overvoltage state.   18. The switching control circuit according to claim 1, wherein the second operation mode information is information relating to distinction between operation modes in a light load state.   The switching control circuit according to claim 25, wherein the output control method is any one of constant output voltage control, constant output current control, and constant output power control.   27. The switching control circuit according to claim 26, wherein the operation mode in the overload state is either an automatic return mode in which an oscillation period and a stop period are repeated or a latch mode in which oscillation is stopped.   28. The switching control circuit according to claim 27, wherein the operation mode in the overvoltage state is either an automatic return mode in which an oscillation period and a stop period are repeated or a latch mode in which oscillation is stopped.   The operation mode in the light load state is either an intermittent oscillation mode in which an oscillation period and a stop period are repeated, or a frequency reduction mode in which the switching frequency of the switching element is reduced to operate in a discontinuous current mode. The switching control circuit described.   A switching power supply device comprising the power conversion circuit including the switching control circuit according to claim 1.

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