JP2002051541A - Switching power supply device and semiconductor device for it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve power supply efficiency in a switching power supply by reducing the current loss of a switching element when a load is light as in standby or the like for reducing power consumption. SOLUTION: A control circuit 16 is provided with a comparator 24 for pulse width modulation that receives a load detection voltage Va generated at the end of the side of a control terminal Tc of a resistor 23 at a positive-phase input terminal, and a triangular wave signal TRW at a reverse-phase input terminal and outputs a pulse width determination signal for determining the pulse width of a switching pulse, a switching signal control circuit 25 for adjusting the control voltage of the switching signal based on the pulse width determination signal, and a light load detection circuit 40 for stopping the output of the switching signal to a switching element 12 to the switching signal control circuit 25 when the load detection voltage Va is larger than an upper-limit voltage value Va01, and starting to output the switching signal to the switching signal control circuit 25 when the load detection voltage Va is smaller than a lower-limit voltage value Va02.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply, and more particularly, to a step-down chopper type switching power supply and a semiconductor device for a switching power supply capable of reducing power consumption under a light load.

[0002]

2. Description of the Related Art FIG. 9 shows a circuit configuration of a conventional step-down chopper type switching power supply. As shown in FIG. 9, the conventional switching power supply has an input terminal 10
This is a step-down type chopper type switching power supply device that steps down a DC voltage applied to 1 to a predetermined voltage value by a switching element 102 composed of an N-type MOSFET and a voltage conversion circuit 103 and outputs it to an output terminal 104.

The input terminal 101 has an anode connected to the input terminal 10.
1 and an input capacitor 105 whose cathode is grounded.
Is provided.

A voltage conversion circuit 103 including a diode 103a, a coil 103b, and a capacitor 103c is provided between a source of the switching element 102 and an output terminal 104.

The switching power supply device further comprises a control circuit power supply capacitor 107 having a cathode connected to the source of the switching element 102 and an anode connected to the output side of the output voltage detection circuit 106;
And a control circuit 108 driven by a power supply voltage Vcc generated by the control circuit 07. The operation of the switching element 102 is controlled by a control signal output from the control circuit 108.

The output voltage detecting circuit 106 is configured by connecting in series a zener diode 106a having a cathode connected to the output terminal 104 and a switching diode 106b having a cathode connected to the anode of a control circuit power supply capacitor 107. .

With this configuration, the voltage between both terminals of the control circuit power supply capacitor 107 is output from the output voltage detection circuit 106.
Output terminal 1 depending on the load current supplied from the
04 is reflected.

The control circuit 108 includes the switching element 10
Signal CLK for determining switching frequency
And a maximum duty cycle signal MDC for determining the maximum duty cycle of the switching element 102, and a triangular wave signal TRW for modulating the pulse width of a switching pulse applied to the switching element 102 (hereinafter referred to as PWM control). It has an oscillator 110 for outputting.

The control circuit 108 further includes a shunt regulator 111 which is turned on when the stepped-down power supply voltage Vcc exceeds a predetermined value; , A PWM control comparator 113 that receives a potential between the shunt regulator 111 and a resistor 112 connected to the source of the switching element 102 and outputs a pulse width determination signal as a comparison result
A reset terminal R receives a pulse width determination signal, a set terminal S receives a clock signal CLK, an RS flip-flop 114, and a first input terminal includes a start / stop circuit 115
, A second input terminal receiving the maximum duty cycle signal MDC, a third input terminal receiving an output signal from the RS flip-flop 114, and outputting a calculation result; Circuit 11
And a drive circuit 117 which receives the output signal from the control signal 6 and outputs an inverted signal to the gate of the switching signal.

Between the PWM control comparator 113 and the RS flip-flop 114, one terminal receives a pulse width determination signal, and the other input terminal receives a drain current ID.
An OR circuit 119 receiving an output signal from a drain current detection circuit 118 that detects Further, the input side is connected to the drain of the switching element 102, the output side is connected via a switch between the anode of the control circuit power supply capacitor 107, and the control is performed from the input terminal 101 when the power supply voltage Vcc is lower than the starting voltage. An internal circuit current supply circuit 120 that supplies a power supply current to the circuit 108 is provided.

Hereinafter, the operation of the conventional switching power supply device configured as described above will be described.

First, when a DC voltage is input to the input terminal 101, the internal circuit current supply circuit 120 of the control circuit 108
, A current is supplied to the control circuit power supply capacitor 107, and the power supply voltage Vcc of the control circuit 108 rises. When the power supply voltage Vcc becomes equal to or higher than the activation voltage value of the control circuit 108, the control circuit 108 is activated and the switching element 102
Is started.

Next, when on / off control of the switching element 102 by the control circuit 108 is started, the start / stop circuit 115 stops the supply of current from the drain via the internal circuit current supply circuit 120. When the switching element 102 is turned on, a current flows from the input terminal 101 to the coil 103b of the voltage conversion circuit 103,
The output voltage Vout increases. At this time, the control circuit 108
Since the reference potential Vo is the same as the source of the switching element 102, the reference potential Vo is substantially equal to the input voltage Vin. Therefore, the potential of the anode of the control circuit power supply capacitor 107 is based on the ground terminal of the input voltage Vin. Assuming that the potential is the sum of the input voltage Vin and the power supply voltage Vcc (= Vin
+ Vcc), which is a very high voltage.

At this time, the switching diode 106b of the output voltage detection circuit 106 has a withstand voltage equal to or higher than the input voltage Vin so that the charge of the control circuit power supply capacitor 107 does not move to the output terminal 104, and the recovery characteristic is fast. . Therefore, the value of the power supply voltage Vcc is always the output voltage Vou
No current flows to the output terminal 104 through the output voltage detection circuit 106 while maintaining a potential higher than t.

Next, when the switching element 102 changes to the off state, the voltage conversion circuit 10 from the input terminal 101
3 is stopped, the voltage conversion circuit 10
Since the electric energy stored in the coil 103b is supplied to the load connected to the output terminal 104 via the third diode 103a, the output voltage Vout gradually decreases. That is, when the switching element 102 is in the off state, the reference potential Vo of the control circuit 108 drops from the high potential to the low potential, and the output voltage Vout becomes
3a, the breakdown voltage Vz of the Zener diode 12, the forward voltage Vf2 of the switching diode 106b, and the total value of the power supply voltage Vcc (= Vz-Vf1 + Vf2).
+ Vcc), a current flows from the output terminal 10 to the control circuit power supply capacitor 107 via the output voltage detection circuit 106, and as a result, the power supply voltage Vcc rises. Is fed back to the control circuit 108. By this feedback, the time (= pulse width) of the ON state of the next output signal of the switching element 102 is determined. At this time, the diode 103a of the voltage conversion circuit 103 has a withstand voltage almost equal to that of the switching element 102, so that the recovery characteristic is high.

As described above, the power supply voltage V
cc is proportional to the output voltage Vout, and the control circuit 108
Performs the PWM control of the switching element 102 according to the fluctuation of the power supply voltage Vcc, and continuously controls the switching element 102 so that the output voltage Vout becomes a predetermined value.

[0017]

As shown in the timing chart of FIG. 10, the conventional switching power supply device is operated at the time of load change such that the load current Iout is reduced, at the time of no load such as at the time of standby, or at the time of light load. Sometimes, the output voltage Vou
t becomes larger than a predetermined value. Due to the rise of the output voltage Vout, the voltage Va inputted to the positive phase input terminal of the PWM control comparator 113 rises, and the potential difference from the triangular wave signal TRW decreases. As a result, the switching element 102
, The pulse width in the ON state becomes smaller, and the drain current ID flowing through the switching element 102 decreases.

However, in the conventional switching power supply, the drain current I
D continues to flow, and the drain current ID cannot be completely stopped. Therefore, even at the time of no load and light load, the switching operation of the switching element 102 causes power loss due to the drain current ID. Further, as the load becomes smaller, the drain current ID of the switching element 102 becomes smaller.
Power loss and the power loss
There is a problem that it is not possible to save power during standby of the power supply.

An object of the present invention is to solve the above-mentioned conventional problems. It is an object of the present invention to reduce power consumption by reducing current loss of a switching element at a light load such as during standby, and to improve power efficiency in a chopper type switching power supply. Is to be able to improve.

[0020]

In order to achieve the above-mentioned object, the present invention provides a switching power supply which is provided with a power supply for a control means which is detected by an output voltage detecting means and is generated by feedback to the control means. The output of the switching signal to the switching means is stopped based on the voltage.

Specifically, the first switching power supply according to the present invention is based on the premise that the switching power supply changes the duty ratio of the switching pulse according to the load fluctuation of the output voltage. Controlling the operation of the switching means, receiving the output signal from the switching means, converting the first DC voltage into a second DC voltage smaller than the absolute value of the first DC voltage, and outputting the converted second DC voltage; Control means, an output voltage detecting means for detecting a voltage value of the second DC voltage, and feeding back the detected signal to the control means, one electrode is connected to the output side of the output voltage detecting means, and the other electrode is connected to the output side. An electrode connected to the output side of the switching means, and a power supply voltage generating means for generating a power supply voltage of the control means based on the detection signal;
An oscillating unit for generating and outputting a switching signal to be applied to the switching means; and, when the value of the power supply voltage is larger than a reference value, stopping the output of the switching signal to the oscillating unit and setting the power supply voltage value to the reference value. If less than the value
A light load detection unit that starts outputting a switching signal to the oscillation unit.

According to the first switching power supply, when the current consumed at a light load decreases and the second DC voltage which is the output voltage of the device increases, the voltage of the second DC voltage increases. The amount of current fed back from the output voltage detecting means for detecting the value to the control means increases. Here, when the value of the power supply voltage is larger than the reference value, the output of the switching signal to the oscillator is stopped, and when the value of the power supply voltage is smaller than the reference value, the output of the switching signal to the oscillator is stopped. Since the power supply voltage of the control means rises because the light load detection section that starts output is provided, the light load detection section of the control means stops the switching operation of the switching element. Power consumption under load can be reduced. For this reason, it is possible to improve the power supply efficiency in a so-called voltage-mode PWM control switching power supply device configured to change the duty ratio of the switching pulse.

A second switching power supply according to the present invention includes a switching element for receiving a first DC voltage at an input terminal, receiving an output signal from the switching element, and converting the first DC voltage to the first DC voltage. Second smaller than the absolute value of
A voltage conversion circuit for converting the DC voltage into a DC voltage for output, a control circuit for controlling the operation of the switching element, and an output voltage detection for detecting the voltage value of the second DC voltage and feeding back the detected signal to the control circuit A power supply capacitor for a control circuit for generating a power supply voltage for the control circuit, wherein the control circuit comprises a switching element, the anode being connected to the output side of the output voltage detection circuit, the cathode being connected to the output side of the switching element. An oscillator that generates and outputs a switching signal to be applied to a pulse width modulator; a pulse width modulation comparator that compares a pulse width modulation signal output from the oscillator with a detection signal to output a pulse width determination signal; A switching signal control circuit for adjusting a pulse width of the switching signal based on the decision signal; and a switching signal control circuit when the voltage value of the detection signal is larger than the reference voltage value. A light load that stops outputting the switching signal to the switching element to the signal control circuit, and starts outputting the switching signal to the switching signal control circuit when the voltage value of the detection signal is smaller than the reference voltage value. A detection circuit.

According to the second switching power supply, when the current consumed at the time of light load decreases and the second DC voltage which is the output voltage of the device increases, the voltage of the second DC voltage increases. The amount of current fed back from the output voltage detection circuit for detecting the value to the control circuit increases. At this time, when the power supply voltage of the control circuit rises and the voltage value of the detection signal is higher than the reference voltage value, the switching signal output to the switching element is stopped by the switching signal control circuit, so that the switching is performed. The loss in the element is reduced, and the power consumption at light load can be reduced. For this reason, the power supply efficiency in a so-called voltage mode PWM control type switching power supply in which the pulse width is determined by comparing the pulse width modulation signal output from the oscillator with the detection signal as the output feedback signal is improved. be able to.

In the second switching power supply device, the reference voltage value is an upper limit voltage value as a reference for stopping the output of the switching signal, and a lower voltage value lower than the upper limit voltage value as a reference for starting the output of the switching signal. Is preferably set to With this configuration, for example, when the output of the switching signal to the switching element is stopped, the value of the second DC voltage decreases, and conversely, the voltage value of the detection signal also decreases. Here, when the detection signal becomes equal to or lower than the upper limit voltage value, the light load detection circuit immediately starts outputting the switching signal to the switching signal control circuit, so that the output suspension period of the switching signal can hardly be set. By providing a hysteresis characteristic which is a time difference until the detection signal becomes smaller than the lower limit voltage value lower than the upper limit voltage value, the output stop period of the switching signal can be reliably set.

It is preferable that the second switching power supply further includes a detection voltage changing means for changing the detection voltage value by variably setting the upper limit voltage value or the lower limit voltage value. By doing so, the load current value during standby can be optimized, so that the degree of freedom in selecting a system incorporating the present apparatus can be increased.

In the second switching power supply, it is preferable that the output voltage detection circuit detects the second DC voltage when the switching signal is off. With this configuration, control using the high-speed switching frequency becomes easy, and the second DC voltage that is the output voltage can be controlled with high accuracy.

In the second switching power supply, it is preferable that the output voltage detection circuit includes a series connection circuit of an output voltage setting element and a diode. In this case, the second DC voltage value can be easily set or changed simply by replacing the output voltage setting element such as a Zener diode or the like. realizable.

In the second switching power supply, it is preferable that the polarity of the second DC voltage is negative. This makes it possible to easily cope with a system requiring a negative control voltage source.

In the second switching power supply, it is preferable that the value of the first DC voltage is approximately 100 V or more and the value of the second DC voltage is approximately 25 V or less. With this configuration, when the first DC voltage that is the input voltage is converted from the commercial AC power and input, the cost can be reduced,
Downsizing and higher performance are more remarkable.

In the second switching power supply device, the switching element and the control circuit are arranged such that the input terminal and the output terminal of the switching element and the input terminal on the anode side of the power supply capacitor for the control circuit in the control circuit become the external connection terminal. Preferably, they are housed in one package. With this configuration, the switching element and the control circuit can be handled as one package, so that the number of components of the power supply main body can be reduced and the size of the switching power supply can be reduced.

In the second switching power supply device, the switching element and the control circuit are arranged such that the input terminal and the output terminal of the switching element and the input terminal on the anode side of the control circuit power supply capacitor in the control circuit are external connection terminals. It is preferable that they are formed integrally on one semiconductor substrate. With this configuration, since the switching element and the control circuit can be integrated into one chip, the number of components can be significantly reduced, and the size of the switching power supply device can be reduced.

A switching power supply semiconductor device according to the present invention includes a switching element for receiving a first DC voltage at an input terminal and a first element for receiving an output signal from the switching element.
A voltage conversion circuit that converts the DC voltage of the first DC voltage into a second DC voltage smaller than the absolute value of the first DC voltage and outputs the second DC voltage, a control circuit that controls the operation of the switching element, and a voltage of the second DC voltage An output voltage detection circuit that detects a value and feeds back the detected signal to the control circuit; an anode connected to the output side of the output voltage detection circuit; a cathode connected to the output side of the switching element; The present invention is directed to a switching power supply semiconductor device for controlling a switching power supply device having a power supply capacitor for a control circuit to generate, the switching power supply semiconductor device including a switching element and a control circuit, and the control circuit applying to the switching element. An oscillator that generates and outputs a switching signal is compared with a pulse width modulation signal output from the oscillator and a detection signal to determine a pulse width. A pulse width modulation comparator for outputting a signal; a switching signal control circuit for adjusting a pulse width of the switching signal based on the pulse width determination signal; and a switching circuit when the voltage value of the detection signal is larger than the reference voltage value. A light load that stops outputting the switching signal to the switching element to the signal control circuit, and starts outputting the switching signal to the switching signal control circuit when the voltage value of the detection signal is smaller than the reference voltage value. A detection circuit.

According to the semiconductor device for a switching power supply of the present invention, when the current consumed at the time of light load decreases and the second DC voltage which is the output voltage of the device rises, the second DC voltage increases. The amount of current that is fed back from the output voltage detection circuit that detects the voltage value to the control circuit increases. At this time, when the power supply voltage of the control circuit rises and the voltage value of the detection signal is higher than the reference voltage value, the switching signal output to the switching element is stopped by the switching signal control circuit, so that the switching is performed. The loss in the element is reduced, and the power consumption at light load can be reduced. For this reason, a power supply of a semiconductor device used in a so-called voltage mode PWM control type switching power supply device in which a pulse width is determined by comparing a pulse width modulation signal output from an oscillator with a detection signal which is an output feedback signal. Efficiency can be improved.

In the semiconductor device for a switching power supply according to the present invention, the reference voltage value is lower than an upper limit voltage value serving as a reference for stopping the output of the switching signal and a lower limit value lower than an upper limit voltage value serving as a reference for starting the output of the switching signal. It is preferably set to a voltage value.

The semiconductor device for a switching power supply of the present invention preferably further comprises a detection voltage varying means for changing a detection voltage value by variably setting an upper limit voltage value or a lower limit voltage value.

In the semiconductor device for a switching power supply of the present invention, it is preferable that the output voltage detecting circuit detects the second DC voltage when the switching signal is in an off state.

In the semiconductor device for a switching power supply of the present invention, it is preferable that the output voltage detection circuit includes a series connection circuit of an output voltage setting element and a diode.

In the switching power supply semiconductor device of the present invention, it is preferable that the polarity of the second DC voltage is negative.

In the semiconductor device for a switching power supply of the present invention, it is preferable that the value of the first DC voltage is approximately 100 V or more and the value of the second DC voltage is approximately 25 V or less.

In the semiconductor device for a switching power supply of the present invention, the switching element and the control circuit are the input terminal and the output terminal of the switching element, and the input terminal on the anode side of the control circuit power supply capacitor in the control circuit is the external connection terminal. It is preferable that they are housed in one package as described above. With this configuration, the switching element and the control circuit can be handled as one package,
The number of parts of the semiconductor device body can be reduced, and the size of the entire switching power supply device can be reduced.

In the semiconductor device for a switching power supply of the present invention, the switching element and the control circuit are the input terminal and the output terminal of the switching element, and the input terminal on the anode side of the control circuit power supply capacitor in the control circuit is the external connection terminal. As described above, it is preferable to be formed integrally on one semiconductor substrate.

[0043]

(First Embodiment) A first embodiment of the present invention.
An embodiment will be described with reference to the drawings.

FIG. 1 shows a schematic circuit configuration of a step-down chopper type switching power supply according to the first embodiment. As shown in FIG. 1, the switching power supply device according to the present embodiment is configured such that a positive first DC voltage, which is applied to an input terminal 11 and is obtained by rectifying an AC voltage of a commercial AC power supply, is formed of an N-type MOSFET. This is a step-down chopper type switching power supply device that steps down to a second DC voltage having a predetermined voltage value by a switching element 12 and a voltage conversion circuit 13 and outputs the voltage to an output terminal 14.

The input terminal 11 is provided with an input capacitor 15 whose anode is connected to the input terminal 11 and whose cathode is grounded.

Further, in the switching power supply according to the present embodiment, the cathode is connected to the source terminal T of the switching element 12.
s, and the control circuit power supply capacitor 17 whose anode is connected to the control terminal Tc which is the input terminal of the control circuit 16.
And an output voltage detection circuit 18 whose input side is connected to the output terminal 14 and whose output side is connected to the control terminal Tc.

Here, the control circuit 16 is driven by a power supply voltage Vcc generated by a control circuit power supply capacitor 17, and the switching element 12 is controlled by a control signal output from the control circuit 16.

Further, the present switching power supply device has a configuration in which the switching element 12 and the control circuit 16 can be integrated,
For example, it is also characterized in that it can be housed in one package or formed monolithically on a semiconductor substrate. A region surrounded by a broken line as a reference numeral 19 in FIG. 1 is an integrated formation region that can be integrally formed, and an end of the integrated formation region 19 is connected to a drain of the switching element 12. A drain terminal TD;
There are provided at least three input / output terminals as external connection terminals: a source terminal Ts connected to the source of the switching element 12 and a control terminal Tc connected to the anode of the control circuit power supply capacitor 17.

When housed in one package, the switching element 12 and the control circuit 16 are not necessarily formed on one semiconductor substrate, but are formed on separate substrates. Is also good.

The voltage conversion circuit 13 includes a diode 131 having an anode grounded and a cathode connected to the source terminal Ts;
It comprises a coil 132 connected in series between the cathode of the diode 131 and the output terminal 14, and a capacitor 133 whose cathode is grounded and whose anode is connected to the output side of the coil 132.

The output voltage detecting circuit 18 comprises a Zener diode 181 having a cathode connected to the output terminal 14 as an output voltage setting element, and a switching diode 182 having a cathode connected to the control terminal Tc, which are connected in series. ing. With this configuration, the voltage between both terminals of the control circuit power supply capacitor 17 fluctuates according to the load current supplied from the output voltage detection circuit 18, and the load state of the output terminal 14 is reflected. Further, by configuring the output voltage detection circuit 18 as a series connection circuit in which a switching diode 182 and a voltage drop type element such as a Zener diode 181 and a resistor are combined, only by replacing the voltage drop type element, The output voltage can be easily set and changed, and the ease of use as in a linear regulator can be realized.

The control circuit 16 includes a clock signal CLK having a switching frequency of the switching element 12, for example, a switching frequency of about 100 kHz, a maximum duty cycle signal MDC for determining the maximum duty cycle of the switching element 12,
An oscillator 21 that generates and outputs a triangular wave signal TRW for performing PWM control of a switching pulse applied to the control terminal Tc, and a power supply voltage Vcc applied to the control terminal Tc is reduced via a resistor. Reference voltage Vco
As described above, the shunt regulator 22 generates and outputs the PWM control current Icc.

The control circuit 16 includes a resistor 23 having one end connected to the source terminal Ts and the other end connected to the output side of the shunt regulator 22, and a PWM control current Icc.
Receives the load detection voltage Va generated at the other end of the resistor 23 at the positive-phase input terminal, receives the triangular wave signal TRW at the negative-phase input terminal, and outputs a pulse width determination signal for determining the pulse width of the switching pulse. For pulse width modulation (PWM
Control) a comparator 24, a switching signal control circuit 25 for adjusting the control voltage of the switching signal based on the pulse width determination signal, and a load detection voltage Va having an upper limit voltage value Va01.
When the load detection voltage Va is smaller than the lower limit voltage value Va02, the output of the switching signal to the switching element 12 is stopped for the switching signal control circuit 25. Light load detection circuit 4 for starting output of switching signal
0.

Further, the control circuit 16 has a drain terminal V
An internal circuit current supply circuit 29 connected between D and the control terminal Vc to supply a start-up current to the control circuit 16
A start / stop circuit 30 connected to the output side of the internal circuit current supply circuit 29 via a switch to control the operation of the switching signal control circuit 25 when the control circuit 16 starts or stops, and a drain of the drain terminal TD. A drain current detection circuit 31 for detecting a current VD is provided between a pulse width modulation comparator 24 and a switching signal control circuit 25. One input terminal receives a pulse width determination signal, and the other input terminal An OR circuit 32 for receiving an output signal from the current detection circuit 31.

The switching signal control circuit 25 receives an output signal of the light load detection circuit 40 at a set terminal S, receives an output signal of an OR circuit 32 at a reset terminal R, and an RS flip-flop circuit 26 at a first input terminal. An output signal of the start / stop circuit 30 is received, and an oscillator 21 is connected to a second input terminal.
Receiving the maximum duty cycle signal MDC from the third
A NAND circuit 27 receiving an output signal from the in-phase output terminal Q of the RS flip-flop circuit 26 at an input terminal thereof,
A gate driver 28 that receives an output signal of the AND circuit 27 and outputs a control signal obtained by inverting and amplifying the received output signal.

The light load detection circuit 40 receives the light load detection reference voltage Va0 at the positive phase input terminal, receives the load detection voltage Va at the negative phase input terminal, and outputs the received load detection voltage Va as the light load detection reference voltage Va0. A light load detection comparator that outputs a low level comparison result signal when equal to or exceeds this, and outputs a high level comparison result signal when the received load detection voltage Va is smaller than the light load detection reference voltage Va0. 41, and an AND circuit 42 which receives a comparison result signal from the load detection comparator 41 at one input terminal and receives a clock signal CLK from the oscillator 21 at the other input terminal.

As a result, the light load detection comparator 41 is
When the load detection voltage Va is equal to or exceeds the light load detection reference voltage Va0, a low level comparison result signal is output.
Output of the switching pulse to is stopped. vice versa,
When the load detection voltage Va is lower than the light load detection reference voltage Va0, the light load detection comparator 41 outputs a high-level comparison result signal, so that the gate driver 28 outputs the switching pulse to the switching element 12 by the gate driver 28. Start.

Here, the voltage value of the light load detection reference voltage Va0 of the light load detection comparator 41 is
From the upper limit voltage value Va01 to the lower limit voltage value Va02 when the comparison result signal Vb from
When the comparison result signal Vb transitions from the low level to the high level, the lower limit voltage value Va02 is preferably reset to the upper limit voltage value Va01. By doing so, the period during which the value of the load detection voltage Va exceeds the value of the light load detection reference voltage Va0 can be extended, so that the period during which the output of the control signal from the gate driver 28 is stopped can be reliably set.

The drain detection circuit 31 sends a reset signal to the RS flip-flop circuit 26 of the switching signal control circuit 25 to stop the switching operation of the switching element 12 when the drain current ID exceeds a predetermined value. Circuit.

As described above, the switching power supply according to the present embodiment compares the voltage value of the triangular wave signal TRW with the value of the load detection voltage Va to change the duty ratio of the switching pulse, that is, in the so-called voltage mode. P
The WM control method is adopted.

The present switching power supply has an input voltage Vin
Although there is no restriction on the voltage value of the output voltage Vout, as an example, the value of the input voltage Vin is set to, for example, 100 V to
When the output voltage Vout is about 25 V and the integrated voltage is about 25 V, the number of parts of the switching power supply device can be greatly reduced by accommodating the integrated formation region 19 in one package or further by making it one chip. Since the size of the switching power supply unit can be reduced, the size, the performance, and the cost can be reduced.

The switching element 12 has an N-type MOS
Although an FET is used, an NPN-type bipolar transistor may be used instead.

Hereinafter, the operation of the switching power supply device configured as described above will be described with reference to the drawings.

FIG. 2 shows the operation timing of the switching power supply according to the present embodiment. First, until the control circuit 16 is started, the start / stop circuit 30 includes the internal circuit current supply circuit 29 and the control circuit power supply capacitor 17.
The switch is closed to connect the anode.

Next, when the input voltage Vin is applied to the input terminal 11, a current flows from the internal circuit current supply circuit 29 to the anode of the control circuit power supply capacitor 17, and the control circuit 1
6, the power supply voltage Vcc rises. When the power supply voltage Vcc becomes equal to or higher than the activation voltage of the control circuit 16, the shunt regulator 22 becomes conductive and the control circuit 16 becomes operable.
The start / stop circuit 30 opens the switch to cut off the connection between the internal circuit current supply circuit 29 and the control circuit power supply capacitor 17.

Next, as shown in FIG. 2, for example, when a load fluctuation occurs in which the load current Iout decreases as in a standby state, the power supply to the load becomes excessive and the output voltage V
The voltage of out rises slightly. Due to the rise of the output voltage Vout, a current is supplied from the output voltage detection circuit 16 to the anode of the control circuit power supply capacitor 17, and the power supply voltage Vcc
Also rises. When the value of the increased power supply voltage Vcc becomes equal to or higher than the voltage value determined by the reference voltage Vco of the shunt regulator 22, the PWM control current Icc flows through the resistor 23 via the shunt regulator 22.

Since the light load detection voltage Va is increased by the PWM control current Icc, the light load detection voltage Va is received by the positive phase input terminal and the triangular wave signal TRW is received by the negative phase input terminal. The period during which the comparator 24 outputs the high-level pulse width determination signal is extended. As a result, the period during which the RS flip-flop circuit 26 receives the high-level pulse width determination signal at the reset terminal R, that is, the reset signal, becomes longer. As a result, FIG.
As shown at the time of the load change, the PWM in which the period during which the drain current VD is equal to the input voltage Vin gradually increases, the period during which the drain current ID flows gradually, and the OFF state of the switching element 12 gradually increases. Control works.

Further, when the load detection voltage Va rises and becomes equal to or higher than the upper limit reference voltage value Va01 of the light load detection reference voltage Va0 in the light load detection comparator 41, the light load detection state is established. The comparison result signal Vb output from 41 changes from the high level to the low level.
Accordingly, the output signal of the AND circuit 42 changes to a low level, and the switching operation of the switching element 12 stops.

At this time, the voltage value of the light load detection reference voltage Va0 of the light load detection comparator 41 is set from the upper limit voltage value Va01 to the lower limit voltage value Va02.

Next, as shown at the time of no load and light load in FIG. 2, when the switching operation by the switching element 12 is stopped and the switching element 12 is turned off, the drain current ID flows through the switching element 12. Disappears. As a result, power is not supplied to the coil 132 of the voltage conversion circuit 13, so that power is supplied only to the output terminal 14 from the capacitor 133, and the output voltage V
out gradually decreases. As a result, the power supply voltage Vcc of the control circuit 16 also gradually decreases, so that the load detection voltage Va also gradually decreases.

At this time, although the load detection voltage Va gradually decreases, the voltage of the light load detection reference voltage Va0 of the light load detection comparator 41 is reduced so that the switching operation by the switching element 12 is not immediately restarted. By setting the value to a lower limit voltage value Va02 lower than the upper limit voltage value Vao1, a hysteresis characteristic is given.

When the output voltage Vout further decreases and the load detection voltage Va becomes lower than or equal to the lower limit voltage value Va02, the comparison result signal Vb of the light load detection comparator 41 transitions from a low level to a high level. Element 12
Is restarted. At this time, the voltage value of the light load detection reference voltage Va0 in the light load detection comparator 41 is reset from the lower limit voltage value Va02 to the upper limit voltage value Va01.

Next, when the switching operation by the switching element 12 is restarted, the current flowing through the switching element 12 becomes larger than the current value when the light load is detected. Because
The output voltage Vout increases again, and the load detection voltage Va also increases. As a result, when the load detection voltage Va becomes equal to or higher than the upper limit voltage value Va01 of the light load detection reference voltage Va0 and the light load state is detected, the switching operation of the switching element 12 stops.

As described above, while the light load detection reference voltage Va0 of the light load detection comparator 41 detects the light load state, the load detection voltage Va exceeds the upper limit voltage value Va01 every time it is detected. It is set to the lower limit voltage value Va02. In the lower limit voltage value Va02, the upper limit voltage value Va0
Since the setting is reset to 1, while the light load is detected, the switching control for turning on and off the switching element 12 is in an intermittent oscillation state in which the stop and restart of the output of the switching signal are alternately repeated.

Here, the intermittent oscillation state refers to a state where a state where a switching pulse is applied to the gate of the switching element 12 and a state where the switching pulse is not applied appear alternately. The output voltage Vout applied to the output terminal 14 is
It gradually decreases during the stop period of the switching pulse in the intermittent oscillation state.
4 depending on the load current Iout. That is, as the load current Iout of the output terminal 14 decreases, the output voltage Vou
t decreases slowly.

The switching stop period in the intermittent oscillation state becomes longer as the load current Iout becomes smaller.
That is, the switching operation of the switching element 12 decreases as the load becomes lighter.

As described above, according to the first embodiment, low power consumption and high power efficiency can be realized in the switching power supply of the voltage mode PWM control method.

(Modification of First Embodiment) A modification of the first embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows a schematic circuit configuration of a step-down chopper type switching power supply according to a modification of the first embodiment. In FIG. 3, the same components as those shown in FIG.

The switching power supply according to this modification is
As shown in FIG. 3, in the light load detection circuit 40, the comparison result signal Vb from the light load detection comparator 41 is subjected to an OR operation with the clock signal CLK of the oscillator 21.
Instead of inputting to the set terminal S of the RS flip-flop circuit 26 through the ND circuit 42, the NAND circuit 2
7 is directly input. This allows AND
Since the circuit 42 is not required, the size can be further reduced.

The operation as a switching power supply is the same as that of the first embodiment, and the light load detection comparator 41
However, when the light-load state of the output terminal 14 is detected by the load detection voltage Va, the high-level comparison result signal Vb transitions to the low level, so that the output signal of the NAND circuit 27 becomes the high level. Thereby, the gate driver 28
Becomes low level, the switching operation of the switching element 12 stops. As a result, as in the first embodiment, when the light load state is detected, the switching element 12 sets the light load detection comparator 41.
Upper limit voltage value Va0 of light load detection reference voltage Va0 set to
Since intermittent oscillation occurs between 1 and the lower limit voltage value Va02, low power consumption and high power supply efficiency can be realized.

(Second Embodiment) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 4 shows a schematic circuit configuration of a step-down chopper type switching power supply according to the second embodiment. In FIG. 4, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 4, a light load detection circuit 40 includes a reference voltage source 43 for generating a light load detection reference voltage Va0.
Is provided, and the positive-phase input terminal of the light load detection comparator 41 is connected to the reference voltage source 43.

Further, this switching power supply device is connected at one end to the positive-phase input terminal of the light load detection comparator 42 via a light load detection voltage adjusting terminal TR provided at the end of the integrated formation region 19. In addition, a light load detection voltage adjusting resistor 51 is provided as detection voltage variable means having the other end connected to the source terminal Ts.

As described above, according to the present embodiment, since the light load detection voltage adjusting resistor 51 capable of variably setting the light load detection reference voltage Va0 is provided, the light load detection voltage adjusting resistor 51 is provided. By properly adjusting the resistance of
The load current Iout at the time when the switching operation of the switching element 12 stops and restarts can be optimally adjusted according to the load required during standby. as a result,
Even if the switching element 12 and the control circuit 16 are integrated into one chip, the upper limit voltage value Va01 or the lower limit voltage value Va02 of the light load detection reference voltage Va0 in the light load detection circuit 40 is set according to the use of the power supply device. Be able to change.

Although the light load detection voltage adjusting resistor 51 is provided outside the integrated formation region 19 in the present embodiment, it may be provided inside the integrated formation region 19. When the light load detection voltage adjusting resistor 51 is provided in the integrated formation region 19, the resistance value may be adjusted by a trimming technique such as a laser trimming method.

(Third Embodiment) Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 5 shows a schematic circuit configuration of a step-down chopper type switching power supply according to the third embodiment. 5, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 5, the control circuit 16 according to the present embodiment is integrally formed with an overvoltage protection circuit 61 for detecting an overvoltage state of the power supply voltage Vcc by the gate of a P-type MOSFET constituting the shunt regulator 22. Region 19
An overheat protection circuit 62 for detecting an overheat state of the (= substrate);
These output signals are sent to a set terminal S via an OR circuit 63.
RS flip-flop circuit 64 which receives a trigger signal at the time of restart and protection RS flip-flop circuit 6
And a restart trigger circuit 65 for outputting the reset signal R to the reset terminal R of the switching signal control circuit 25.
7 is input.

As described above, in the switching power supply according to the present embodiment, when the overvoltage state and the overheat state of the control circuit 16 are detected, the switching element of the switching signal control circuit 25 is controlled by the overvoltage protection circuit 61 or the overheat protection circuit 62. 12, the switching operation can be stopped, and the switching operation can be restarted by the restart trigger circuit 65.

Therefore, as in the first embodiment, the present switching power supply and the electronic equipment incorporating the switching power supply can be reliably protected while improving the efficiency of the switching power supply and miniaturizing the apparatus. Become like

In the third embodiment, the reference voltage source 43 and the light load detection voltage adjusting resistor 51 according to the second embodiment may be provided.

(Modification of Third Embodiment) Hereinafter, a modification of the third embodiment of the present invention will be described with reference to the drawings.

FIG. 6 shows a schematic circuit configuration of a step-down chopper type switching power supply according to a modification of the third embodiment. 6, the same components as those shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

A switching power supply according to this modification is
As shown in FIG. 6, in the light load detection circuit 40, the comparison result signal Vb from the light load detection comparator 41 is subjected to an OR operation with the clock signal CLK of the oscillator 21.
Instead of inputting the signal to the set terminal S of the RS flip-flop circuit 26 via the ND circuit 42, the NAND
The input is made to the circuit 27. This allows AND
Since the circuit 42 is not required, the size can be further reduced.

As described above, miniaturization, low power consumption, and high power supply efficiency can be realized while having a reliable protection function.

(Fourth Embodiment) Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings.

FIG. 7 shows a schematic circuit configuration of a step-down chopper type switching power supply according to the fourth embodiment. In FIG. 7, the same components as those shown in FIG.

As shown in FIG. 5, in the switching power supply according to the fourth embodiment, the configuration of the voltage conversion circuit 13A is the same as that of the switching power supply shown in FIG.
Configuration is different.

That is, the voltage conversion circuit 13 A is connected in series so that the diode 131 is connected between the source terminal Ts and the output terminal 14 and the cathode thereof is connected to the source terminal Ts, and the coil 132 is connected in parallel with the capacitor 133. And is connected to the cathode of the diode 131.

By adopting such a configuration of the voltage conversion circuit 13A, the polarity of the input terminal 11 can be changed without changing the polarity.
Since the polarity of the output terminal 14 can be negative,
Even in a system requiring a negative control voltage source (step-down power supply), a negative voltage source can be realized without changing the configuration of each circuit on the integrated formation area 19 having the switching element 12 and the control circuit 16. .

In the fourth embodiment, the reference voltage source 43 and the light load detection voltage adjusting resistor 51 according to the second embodiment may be provided.

Further, the overvoltage protection circuit 61, the overheat protection circuit 62, the OR circuit 63, and the protection R shown in the third embodiment.
S flip-flop circuit 64 and restart trigger circuit 65
May be provided.

(Modification of Fourth Embodiment) Hereinafter, a modification of the fourth embodiment of the present invention will be described with reference to the drawings.

FIG. 8 shows a schematic circuit configuration of a step-down chopper switching power supply according to a modification of the fourth embodiment. 8, the same components as those shown in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted.

A switching power supply according to this modification is
As shown in FIG. 8, in the light load detection circuit 40, a logical sum of the comparison result signal Vb from the light load detection comparator 41 and the clock signal CLK of the oscillator 21 is calculated.
Instead of inputting the signal to the set terminal S of the RS flip-flop circuit 26 via the ND circuit 42, the NAND
The input is made to the circuit 27. This allows AND
Since the circuit 42 is not required, the size can be further reduced.

As described above, it is possible to realize a negative voltage source capable of achieving downsizing, low power consumption, and high power supply efficiency without changing the circuit configuration of the positive control circuit 16.

In each of the embodiments and the modified examples, the switching power supply device has been described as a non-continuous mode in which the output power from the output terminal 14 is not reflected. However, the same applies to the continuous mode in which the output power is reflected. The effect of can be obtained.

[0110]

According to the switching power supply device of the present invention, when the value of the power supply voltage of the control circuit is larger than the reference value, the output of the switching signal to the oscillating section is stopped, and the value of the power supply voltage becomes the reference value. When the power supply voltage of the control unit increases, the light load detection unit of the control unit includes the light load detection unit that starts outputting the switching signal to the oscillation unit when the value is smaller than the value. Since the switching operation is stopped, loss in the switching means is reduced, power consumption at light load can be reduced, and power efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing a step-down chopper type switching power supply device according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing an operation state of the step-down chopper switching power supply according to the first embodiment of the present invention.

FIG. 3 is a schematic circuit diagram showing a step-down chopper switching power supply according to a modification of the first embodiment of the present invention;

FIG. 4 is a schematic circuit diagram showing a step-down chopper type switching power supply device according to a second embodiment of the present invention.

FIG. 5 is a schematic circuit diagram showing a step-down chopper type switching power supply according to a third embodiment of the present invention.

FIG. 6 is a schematic circuit diagram showing a step-down chopper switching power supply according to a modification of the third embodiment of the present invention.

FIG. 7 is a schematic circuit diagram showing a step-down chopper switching power supply according to a fourth embodiment of the present invention.

FIG. 8 is a schematic circuit diagram showing a step-down chopper switching power supply according to a modification of the fourth embodiment of the present invention.

FIG. 9 is a schematic circuit diagram showing a conventional step-down chopper type switching power supply device.

FIG. 10 is a timing chart illustrating an operation state of a conventional step-down chopper type switching power supply device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Input terminal 12 Switching element (switching means) 13 Voltage conversion circuit (voltage conversion means) 13A Voltage conversion circuit (voltage conversion means) 131 Diode 132 Coil 133 Capacitor 14 Output terminal 15 Input capacitor 16 Control circuit (Control means) 17 Control circuit Power supply capacitor (power supply voltage generation means) 18 Output voltage detection circuit (output voltage detection means) 181 Zener diode (output voltage setting element) 182 Switching diode 19 Integrated formation area 21 Oscillator (oscillator) 22 Shunt regulator 23 Resistor 24 Pulse width modulation comparator 25 switching signal control circuit 26 RS flip-flop circuit 27 NAND circuit 28 gate driver 29 internal circuit current supply circuit 30 start / stop circuit 40 light load detection circuit (light load detection circuit) 41) Light load detection comparator 42 AND circuit 43 Reference voltage source 51 Light load detection voltage adjustment resistor (detection voltage varying means) 61 Overvoltage protection circuit 62 Overheat protection circuit 63 OR circuit 64 Protection RS flip-flop circuit 65 Restart trigger circuit Ts Source terminal TD Drain terminal Tc Control terminal TR Light load detection voltage adjustment terminal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Yo Shiomi, 1-1, Yukicho, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. (72) Inventor: Naohiko Moroda 1-1-1, Yukicho, Takatsuki, Osaka, Japan (72) Inventor Tetsuji Yamashita 1-1, Yukicho, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. F-term (reference) 5F038 AV02 AV03 AV04 AV05 AV06 BG02 BG04 BG06 BH15 BH16 DF08 EZ20 5H730 AA14 AS01 AS04 AS05 AS23 BB13 BB15 BB57 DD04 EE59 FD01 FF02 FG05 VV02 ZZ05 ZZ12

Claims (19)

[Claims] 1. A switching power supply device for changing a duty ratio of a switching pulse according to a load change of an output voltage, wherein: a switching means for receiving a first DC voltage;
Voltage converting means for converting the DC voltage of the first DC voltage into a second DC voltage smaller than the absolute value of the first DC voltage and outputting the second DC voltage; control means for controlling the operation of the switching means; and the second DC voltage Output voltage detecting means for detecting a voltage value of the output voltage and returning a detected signal to the control means; one electrode connected to the output side of the output voltage detecting means, and the other electrode connected to the output side of the switching means. Power supply voltage generation means for generating a power supply voltage for the control means based on the detection signal, wherein the control means generates and outputs a switching signal to be applied to the switching means; and When the value of the voltage is larger than the reference value, the output of the switching signal to the oscillation unit is stopped,
A switching power supply device comprising: a light load detection unit that starts outputting the switching signal to the oscillation unit when the value of the power supply voltage is smaller than a reference value. 2. A switching element for receiving a first DC voltage at an input terminal, and receiving the output signal from the switching element and receiving the first DC voltage.
A voltage conversion circuit that converts the DC voltage of the first DC voltage to a second DC voltage smaller than the absolute value of the first DC voltage and outputs the second DC voltage; a control circuit that controls the operation of the switching element; and the second DC voltage An output voltage detection circuit that detects a voltage value of the output voltage and returns a detected detection signal to the control circuit; an anode is connected to an output side of the output voltage detection circuit; a cathode is connected to an output side of the switching element; A control circuit power supply capacitor for generating a power supply voltage of the control circuit, wherein the control circuit generates and outputs a switching signal to be applied to the switching element; and a pulse width modulation output from the oscillator. A pulse width modulation comparator for comparing a signal with the detection signal and outputting a pulse width determination signal; and a pulse signal for the switching signal based on the pulse width determination signal. A switching signal control circuit that adjusts a pulse width, and when the voltage value of the detection signal is larger than a reference voltage value, stops outputting the switching signal to the switching element with respect to the switching signal control circuit,
A switching power supply, comprising: a light load detection circuit that starts outputting the switching signal to the switching signal control circuit when a voltage value of the detection signal is smaller than a reference voltage value. apparatus. 3. The reference voltage value includes an upper limit voltage value serving as a reference for stopping output of the switching signal and a lower limit voltage value lower than the upper limit voltage value serving as a reference for starting output of the switching signal. The switching power supply according to claim 2, wherein the switching power supply is set. 4. The switching power supply according to claim 3, further comprising a detection voltage changing unit that changes the detection voltage value by variably setting the upper limit voltage value or the lower limit voltage value. apparatus. 5. The switching power supply according to claim 2, wherein the output voltage detection circuit detects the second DC voltage when the switching signal is in an off state. 6. The switching power supply according to claim 2, wherein the output voltage detection circuit includes a series connection circuit of an output voltage setting element and a diode. 7. The switching power supply according to claim 2, wherein the polarity of the second DC voltage is negative. 8. The value of the first DC voltage is approximately 100 V
4. The switching power supply according to claim 2, wherein the value of the second DC voltage is approximately 25 V or less. 9. The switching element and the control circuit, wherein an input terminal and an output terminal of the switching element, and an input terminal on the anode side of the control circuit power supply capacitor in the control circuit become an external connection terminal. Claim 2 which is accommodated in one package
9. The switching power supply device according to any one of 8. 10. The switching element and the control circuit, wherein an input terminal and an output terminal of the switching element, and an input terminal on the anode side of the control circuit power capacitor in the control circuit are external connection terminals. The switching power supply device according to any one of claims 2 to 9, wherein the switching power supply device is formed integrally on one semiconductor substrate. 11. A switching element that receives a first DC voltage at an input terminal, and a second element that receives an output signal from the switching element and reduces the first DC voltage smaller than the absolute value of the first DC voltage. A voltage conversion circuit for converting the DC voltage into a DC voltage and outputting the converted DC voltage; a control circuit for controlling the operation of the switching element; A voltage detection circuit, the anode is connected to the output side of the output voltage detection circuit,
A switching power supply semiconductor device for controlling a switching power supply device having a cathode connected to an output side of the switching element and a control circuit power supply capacitor for generating a power supply voltage of the control circuit, wherein the switching power supply semiconductor An apparatus includes the switching element and the control circuit, wherein the control circuit generates and outputs a switching signal applied to the switching element; a pulse width modulation signal output from the oscillator; and the detection signal. And a pulse width modulation comparator that outputs a pulse width determination signal; a switching signal control circuit that adjusts the pulse width of the switching signal based on the pulse width determination signal; and a voltage value of the detection signal. Is larger than the reference voltage value, the switching signal control circuit It stops outputting the switching signal to the switching element,
A switching power supply, comprising: a light load detection circuit that starts outputting the switching signal to the switching signal control circuit when a voltage value of the detection signal is smaller than a reference voltage value. For semiconductor devices. 12. The reference voltage value includes an upper limit voltage value serving as a reference for stopping output of the switching signal and a lower limit voltage value lower than the upper limit voltage value serving as a reference for starting output of the switching signal. The semiconductor device for a switching power supply according to claim 11, wherein the setting is set. 13. The switching power supply according to claim 12, further comprising a detection voltage changing unit that changes the detection voltage value by setting the upper limit voltage value or the lower limit voltage value variably. For semiconductor devices. 14. The semiconductor device for a switching power supply according to claim 11, wherein the output voltage detection circuit detects the second DC voltage when the switching signal is in an off state. 15. The semiconductor device for a switching power supply according to claim 11, wherein said output voltage detection circuit includes a series connection circuit of an output voltage setting element and a diode. 16. The switching power supply semiconductor device according to claim 11, wherein the polarity of the second DC voltage is negative. 17. The value of the first DC voltage is approximately 100
13. The semiconductor device for a switching power supply according to claim 11, wherein the voltage is not less than V and the value of the second DC voltage is not more than about 25 V. 18. The switching element and the control circuit, wherein an input terminal and an output terminal of the switching element, and an input terminal on the anode side of the power supply capacitor for the control circuit in the control circuit are external connection terminals. 12. The package according to claim 11, wherein the package is housed in one package.
The semiconductor device for a switching power supply according to any one of claims 17 to 17. 19. The switching element and the control circuit, wherein an input terminal and an output terminal of the switching element, and an input terminal on the anode side of the control circuit power capacitor in the control circuit are external connection terminals. The semiconductor device for a switching power supply according to any one of claims 11 to 18, wherein the semiconductor device is integrated on one semiconductor substrate.