JPH08340672A - Switching regulator having overcurrent protection function - Google Patents

Abstract

PURPOSE: To reduce the size of a switching regulator having an overcurrent protection function and improve its reliability by a method wherein a variable resistance element is so designed as to have the resistance value of an overcurrent detection resistor part increased when an input voltage detected by an input voltage detector unit is large and have the resistance value decreased when the input voltage is small. CONSTITUTION: An overcurrent detection resistor part 50 has a variable resistor element Q2 and resistors R10-R40. A current Id which is applied to a switching device Q1 is applied to the variable resistor element Q2 and the resistor R20 through the resistor R10. The resultant voltage V3 at that time is used as a detected value in an overcurrent detection state. Further, an input voltage detector unit 60 has a comparator CO, resistors R50 and R60 and a reference voltage source Vref. An input voltage V1 is divided by the resistors R50 and R60 and compared with the reference voltage of the reference voltage source Vref by a comparator CO. If the divided voltage is not larger than the reference voltage, a voltage by which the element Q2 is turned ON is outputted. If the divided voltage exceeds the reference voltage, a negative voltage or a voltage by which the element Q2 can not be turned ON is outputted. As a result, the operation of the overcurrent protection can be variable and the size reduction and the reliability improvement can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator having an overcurrent protection function for obtaining a DC output from a pulsating current input by using a switching element.

[0002]

2. Description of the Related Art In a conventional switching regulator having an overcurrent protection function, an overcurrent detection resistor for detecting an overcurrent is inserted in a part of a main circuit of the switching regulator, and an overcurrent is generated from a voltage generated in the resistor. I am trying to detect. Such a switching regulator is shown in FIGS. 6 (a) and 6 (b).
Will be described with reference to.

FIG. 6A is a circuit diagram of an isolated switching regulator of an ON / ON control type, in which an input from an AC power source is full-wave rectified by a diode bridge rectifier circuit 10 and smoothed by a capacitor C1. . Input voltage V1
Is applied to a series circuit of a primary winding L1 of a transformer 20 constituting a switching circuit and a switching element Q1 formed of a power semiconductor element (power device) such as a power MOSFET or a MOS type field effect transistor for high power. The switching element Q1 is turned on / off by the control unit 40 at a frequency sufficiently higher than that of the AC power supply, and interrupts the current flowing through the primary winding L1. The output of the chopper circuit obtained from the secondary winding L2 of the transformer 20 is rectified by the diodes D1 and D2 and the choke coil L3.
Is smoothed by the capacitor C2 and converted into a DC output of the voltage V2. The control unit 40 includes a PWM circuit and the like, and changes the duty ratio of the pulse driving of the switching element Q1 so that the output voltage V2 of the reactor wave circuit becomes a predetermined value.

Specifically, when the switching element Q1 is on, a current flows from the rectifier circuit 10 through the switching element Q1 to the transformer primary winding L1 and a voltage is generated at L2. The amount of increase in the current during the ON period is inversely proportional to the input voltage V1 and also proportional to the ON time. When the switching element Q1 is turned off, a current due to the release of energy stored in L3 flows to the secondary side, is rectified and smoothed, and then DC power is supplied to a load (not shown).

In the switching regulator as described above, the overcurrent detection resistor R1 is provided as an overcurrent detection circuit for detecting an overcurrent state. The control unit 40 performs control to reduce the pulse width of the PWM circuit based on the voltage across the resistor R1. As a result, the output voltage and the output current decrease, and an overcurrent protection operation is performed.

Specifically, the current Id flowing through the switching element Q1 is converted into a voltage value by the overcurrent detection resistor R1 and the overcurrent state is detected based on this voltage value. The current Id and the resistor R1 are detected. The voltage across both ends of the waveform has a solid line waveform as shown in the time-dependent change waveform of FIG. When the peak value Ip2 is reached in this waveform, the overcurrent protection operation as described above is started.

[0007]

In the switching regulator having the above-mentioned overcurrent protection function, for example, when the AC input voltage decreases, the peak value of the current Id flowing through the switching element Q1 increases in inverse proportion to the AC input voltage. Thus, the waveform and the peak value Ip2 are as shown by the broken line in FIG. Specifically, when the fluctuation range of the DC voltage after rectification and smoothing is 105 to 195V, 105V
The peak value at that time reaches twice the peak value at 195V.

When a large current flows through the switching element Q1 as described above, a large stress is applied to the switching element Q1, which accelerates the deterioration of the element and continues to flow for a long time due to an unexpected cause. Was sometimes damaged.

In order to cope with such stress, a large capacity transistor and a large radiator have to be used, which promotes cost increase and size increase. Further, if the overcurrent continues to flow through the switching element Q1, the output voltage may drop, which may adversely affect the load connected to the switching regulator.

The present invention has been made in view of the above problems, and an object thereof is to make the current detection value for overcurrent protection variable with respect to the change of the input voltage, thereby reducing the size and improving the reliability. Another object of the present invention is to provide a switching regulator having an overcurrent protection function.

[0011]

In order to achieve the above object, a switching regulator having an overcurrent protection function of the present invention has an overcurrent protection function of obtaining a DC output from a pulsating current input by using a switching element. In the switching regulator, an overcurrent detection resistor unit that converts the current value flowing in the switching element into a voltage value, and an input voltage detection circuit unit that detects the voltage of the pulsating current input,
The overcurrent detection resistance unit has a variable resistance element, and the variable resistance element increases the resistance value of the overcurrent detection resistance unit when the input voltage detected by the input voltage detection circuit unit is large, and When the input voltage is small, the resistance value is reduced so that the voltage value converted by the overcurrent detection resistor unit does not change significantly depending on the magnitude of the input voltage, or is constant or the amount of change is small. It will be.

[0012] Preferably, the variable resistance element is a power semiconductor element (power device), and the power semiconductor element performs conduction and non-conduction operation or linear operation based on the input voltage detected by the input voltage detection means. It will be done like this.

Further, the power semiconductor element is an M for high power.
OS type field effect transistor, that is, power MOSFET
It is preferable that

More preferably, the variable resistance element is composed of a small power type switching transistor, and the small power type switching transistor is made to conduct and non-conduct based on the input voltage detected by the input voltage detecting means. It will be.

Further, according to the present invention, an overcurrent detecting resistor section for converting a current value flowing in the switching element into a voltage value, an input voltage detecting circuit section for detecting a voltage of the pulsating current input, and the overcurrent detecting resistor section. An overcurrent detection control unit for detecting an overcurrent state by comparing the converted voltage value of the unit and an overcurrent reference voltage, the input voltage detection circuit unit, if the detected input voltage is large, By controlling the output of the overcurrent detection control unit by decreasing the overcurrent reference voltage and increasing the overcurrent reference voltage when the input voltage is low, the switching element increases as the input voltage increases. Therefore, the current flowing through is reduced.

[0016]

When the input voltage detected by the input voltage detection circuit section is high, the resistance value of the overcurrent detection resistance section is increased, and when the input voltage is low, the resistance value is decreased to reduce the resistance. Since the voltage value converted by the resistance portion is constant or the amount of change thereof is small, even if the input voltage changes, the amount of change can be small even if the voltage value is constant or changes. .

Therefore, a large current can be prevented from flowing into the switching element as the input voltage increases, and the operation of the overcurrent protection can be made variable with respect to the change of the input voltage. Further, the power consumption at the time of overcurrent can be suppressed and the heat generation amount can be suppressed without being affected by the magnitude of the input voltage.

The variable resistance element is a power MOSF.
In the case of a power semiconductor element such as ET, the power semiconductor element performs conducting and non-conducting operations, or linear operation (linear operation) based on the input voltage detected by the input voltage detecting means, thereby changing the input voltage. Since it is possible to follow the change in mV unit, it is possible to perform highly accurate linear operation and conductive and non-conductive operation. Therefore, the voltage for detecting the overcurrent state can be controlled with high accuracy to a predetermined value or within a predetermined range.

The input voltage detection circuit unit reduces the overcurrent reference voltage when the input voltage detected by the input voltage detection circuit unit is large, and the overcurrent reference voltage when the input voltage is small. To increase. As a result, the output of the overcurrent detection control unit is controlled so that the current flowing through the switching element becomes smaller as the input voltage increases, so that the switching element has a larger current as the input voltage increases. Can be prevented, and the operation of the overcurrent protection can be made variable with respect to the change of the input voltage. Further, the power consumption at the time of overcurrent can be suppressed and the heat generation amount can be suppressed without being affected by the magnitude of the input voltage.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a switching regulator having an overcurrent protection function according to the present invention will be described with reference to FIGS. 1 to FIG. 4 and the above-mentioned FIG.
The following points are different from the conventional configuration shown in (a).

In the first embodiment, FIG.
In place of the overcurrent detection resistor R1 in the circuit shown in (a), an overcurrent detection resistor section 50 is provided and an input voltage detection circuit section 60 is added.

Except for the above differences, the structure is basically the same as that of the conventional example shown in FIG. 6A, and therefore these differences will be mainly described. In the switching regulator having the overcurrent protection function shown in FIG. 1A, the output is 5V-10A and the operating current value of the overcurrent protection is 12A.

The overcurrent detection resistor section 50 is a variable resistance element Q2.
And the respective resistors R10 to R40, the current Id flowing through the switching element Q1 flows through the resistor 10 to the variable resistance element Q2 and the resistance R20, and the variable resistance element Q at this time.
2 and the combined voltage V3 as the overcurrent detection voltage determined by the combined resistance R70 of the resistors R10 and R20 are the detection values for detecting the overcurrent detection state. Then, as in the conventional case, the control unit 40 is configured to perform the overcurrent protection operation based on the detected value.

The input voltage detection circuit unit 60 includes a comparator CO, resistors R50 and R60, and a reference voltage source Vre.
f and has an input voltage V1 of resistance R50 and resistance R
The voltage is divided by 60, and the divided voltage and the reference voltage source Vre
The reference voltage of f is compared by the comparator CO. This comparator C
When the divided voltage of the variable resistance element Q2 of the overcurrent detection resistance unit 50 is equal to or lower than the reference voltage, O becomes O.
While outputting the voltage for N, when the reference voltage is exceeded, a negative voltage or a voltage at which Q2 cannot be turned on is output.

The output signal of the comparator CO is configured to be input to the gate terminal of the variable resistance element Q2 via the resistor R40, and this output signal is used to output the variable resistance element Q2.
Performs conducting and non-conducting operations (switching operations).

Specifically, the AC input voltage V of FIG.
As shown in the characteristic diagram of each circuit element with respect to in (AC), the combined resistance R is set at the boundary of the AC input voltage Vin (AC) of approximately 150V.
70 changes stepwise, and accordingly, the combined voltage V3 has a triangular characteristic and falls within a predetermined small range. As a result, the current Id flowing through the switching element Q1 is linearly (linearly) reduced during the operation of the overcurrent protection. It is supposed to be.

More specifically, the AC input voltage Vin (AC) is 150
In the range up to V, the variable resistance element Q2 maintains the ON state because the comparator CO outputs a positive voltage, and as a result, the combined resistance R
70 is a relatively low constant value, and AC input voltage Vin (AC)
In the range of over 150 V, the comparator CO outputs a negative voltage, so that the variable resistance element Q2 is kept in the OFF state. As a result, the combined resistance R70 is kept at a relatively high constant value.

Here, in order to compare the heat generation amount of the circuit element at the time of the operation of the overcurrent protection between the conventional example of FIG. 6A and the present example, the switching element Q1 and the diode D are compared.
The power consumption of 1 and D2 was measured. Table 1 shows the results.

[0029]

[Table 1] As shown in Table 1, conventionally, both the switching element Q1 and the diodes D1 and D2 have an AC input voltage Vin (AC).
Power consumption doubles when the voltage doubles from 100V to 200V
That is, the amount of heat generated is doubled. On the other hand, in the present application, even if the AC input voltage Vin (AC) is doubled, the power consumption, that is, the heat generation amount is almost the same. From this, it was confirmed that the present embodiment can suppress the heat generation amount of the circuit to a predetermined value without being affected by the input voltage, as compared with the conventional example.

Next, a modification of this embodiment will be described. Combined resistance R7 against fluctuation of AC input voltage Vin (AC)
In changing the resistance value of 0, in the above-described first embodiment, the resistance value is changed stepwise.
In this modification, an amplifier (op-amp) is used in place of the comparator CO of the input voltage detection circuit unit 60 to linearly change the configuration.

Specifically, the AC input voltage V of FIG.
As shown in the characteristic diagram of each circuit element with respect to in (AC), the combined resistance R70 increases linearly as the AC input voltage Vin (AC) increases, and the current Id flowing through the switching element Q1 increases linearly as a result. As a result, the combined voltage V3 has a constant value.

Also in this modification, the above-mentioned Table 1 is used.
Similarly, even when the AC input voltage Vin (AC) is doubled, the power consumption, that is, the heat generation amount is almost the same. From this, it was confirmed that the present embodiment can suppress the heat generation amount of the circuit to a predetermined value without being affected by the input voltage, as compared with the conventional example.

In the above-described first embodiment and its modification, a power semiconductor element (power device) composed of a high power MOS type field effect transistor, that is, a power MOSFET is used as the variable resistance element Q2. The resistance value of the combined resistance R70 can be changed by following the change of the input voltage V1 in units of mV by conducting and non-conducting operations of this power MOSFET or by linear operation (linear operation), and to detect an overcurrent state. It was possible to control the combined voltage V3 of (1) with a high precision within a predetermined value or within a predetermined range.

The circuit configuration of the combined resistor R70 can be modified in various ways as shown in FIGS. 2 (a) and 2 (b) in addition to those shown in the first embodiment and its modification. In the figure (a), the resistor R10 is connected in series to the variable resistance element Q2, and in the figure (b), the resistor R10 is connected to the variable resistance element Q2.
A resistor R20 is connected in parallel to a circuit in which 10 is connected in series.

Furthermore, by appropriately setting the operating characteristics of the circuit, the combined voltage V3 for detecting the overcurrent state can be set within an arbitrary constant value or within a predetermined range.

Furthermore, when changing the resistance value of the combined resistance R70, it is based on the AC input voltage Vin (AC), but it is not limited to this and can be changed based on various parameters. Regarding the load, parameters related to the operating environment such as internal temperature and humidity or the operating state such as damage to parts can be considered. As the circuit configuration, as shown in FIG. 3A, a control means A for outputting a control signal based on the temperature of the circuit and a control means B for outputting a control signal based on the state of the load are used. A and B are OR-connected between the output terminal of the comparator CO and the gate terminal of the resistance element Q2. In this configuration, with respect to the temperature control means A, as shown in FIG.
The resistance value of 70 is adjusted to linearly increase or decrease the current Id flowing through the switching element Q1. As a result, the combined voltage V for detecting the overcurrent state is detected.
3 can be controlled.

Next, another modification of the above-described first embodiment will be described. In this modification, the combined resistor R70 in the circuit diagram of FIG. 1A is configured as shown in the circuit diagram of FIG. 4A. In FIG. 4A, the resistance R
The connection point between 20a and R20 is connected to the switching transistor Q1 and the resistor R is used as an overcurrent detection resistor.
20 only, the high power type power MOSFE of FIG.
A low power type switching transistor is used as the variable resistance element Q3 in place of Q2 made of T. Further, the connection point between the resistors R20a and 20b is connected to the control unit 4 of FIG.
A combined voltage V3 that is connected to 0 and detects an overcurrent state is applied.

In the above configuration, the variable resistance element Q3 is for determining the voltage division ratio of the combined resistance R70 including the resistances R20, 20a, 20b and the variable resistance element Q3, and as a result, as shown in FIG. The characteristic of each circuit element as shown in the characteristic diagram of each circuit element with respect to the AC input voltage Vin (AC) of b) is obtained.

The composite resistance R70 changes into a triangular wave shape (not shown) at the boundary of the AC input voltage Vin (AC) of approximately 150 V,
As shown in FIG. 4 (b), the combined voltage V3 as a voltage for detecting overcurrent detection becomes a triangular wave accordingly and falls within a predetermined small range. As a result, the current Id and the voltage V4 flowing through the switching element Q1 become linear. It is getting smaller.

More specifically, the AC input voltage Vin (AC) is 150
In the range up to V, the variable resistance element Q3 maintains the ON state because the comparator CO outputs a positive voltage, and as a result, the combined resistance R
70 decreases linearly and the AC input voltage Vin (AC) is 150V
In the range exceeding, the variable resistance element Q3 is turned off because the comparator CO outputs a negative voltage, resulting in the combined resistance R70.
Will rise once and then decrease linearly. The combined voltage V3 also changes in a similar locus in accordance with the change in the combined resistance R70, whereby the current Id and the voltage V3 decrease linearly.

Further, the comparator C of the input voltage detection circuit section 60
By using an amplifier instead of O, as shown in FIG. 4C, the combined resistance R70 and the voltage V3 maintain a constant state with respect to an increase in the AC input voltage Vin (AC), and the combined resistance R70 and the voltage V3 are combined. Current I flowing through resistor V4 and switching element Q1
It decreases linearly with d.

Further, by adopting the configuration shown in FIG. 4D, the overcurrent detection voltage input to the control unit 40 may be directly controlled by the variable resistance element Q3.

Also in the present modified example described above, as in the case of Table 1 described above, even if the AC input voltage Vin (AC) is doubled, the power consumption, that is, the amount of heat generation is almost the same. From this, it was confirmed that the present embodiment can suppress the heat generation amount of the circuit to a predetermined value without being affected by the input voltage, as compared with the conventional example.

Therefore, a large current Id can be prevented from flowing into the switching element Q1 as the input voltage V1 increases, and the operation of overcurrent protection can be made variable with respect to the change of the input voltage. Further, the power consumption at the time of overcurrent can be suppressed and the amount of heat generation can be suppressed without being affected by the magnitude of the input voltage V1.

Next, a second embodiment of the present invention will be described with reference to FIGS. 5 (a) to 5 (c). In this embodiment, FIG.
As shown in (a), an overcurrent detection control unit 40a is arranged in the control unit 40, and this overcurrent detection control unit 40a includes an error amplifier A and a reference voltage source Vref1.

The overcurrent detection resistor section 50 includes resistors R20 and R20a connected in series, and these resistors R20 and R20 are connected.
A composite voltage V3 is generated across both ends of 20a, and the input voltage detection circuit section 60 has the same configuration as that of the first embodiment, but the output of the comparator CO is used as the variable reference voltage Vref '.

The error amplifier A includes an input voltage detection circuit section 6
An overcurrent reference voltage Vr, which is a combination of the variable reference voltage Vref ′ of 0 and the voltage of the reference voltage source Vref1, and a combined voltage V3 of the overcurrent detection resistor unit 50 are applied. The error amplifier A compares the composite voltage V3 with the overcurrent reference voltage Vr to detect an overcurrent state, and the PW provided in the control unit 40.
The ON time of the switching element Q1 is narrowed down by the M circuit,
Prevent overcurrent condition.

The comparator CO of the input voltage detection circuit section 60 is
When the detected input voltage V1 is large, the variable reference voltage V
While ref 'is reduced to reduce the overcurrent reference voltage Vr, when the input voltage V1 is low, the overcurrent reference voltage Vr is reduced.
Operates to increase r. As a result, even if the input voltage V1 increases, the current Id flowing through the switching element Q1 decreases.

In the above configuration, as shown in FIG. 4B, the variable reference voltage Vref 'changes stepwise at the boundary of the AC input voltage Vin (AC) of about 150V, and accordingly the switching element. As a result of the current Id flowing through Q1 decreasing linearly, the combined voltage V3 decreases linearly.

More specifically, the AC input voltage Vin (AC) is 150
In the range up to V, since the comparator CO outputs a positive voltage, the overcurrent reference voltage Vr maintains a relatively large constant value, and in the range where the AC input voltage Vin (AC) exceeds 150V, the comparator CO is negative. The variable resistance element Q2 is turned off to output voltage
Keep the state of. As a result, the current Id and the combined voltage V3 decrease linearly.

Further, the comparator C of the input voltage detection circuit section 60
By using an amplifier instead of O, the reference voltage Vref 'may be linearly reduced as the AC input voltage Vin (AC) increases, as shown in FIG. 5 (c). In this case, as a result of the current Id flowing through the switching element Q1 decreasing linearly, the combined voltage V3 decreases linearly.

Further, the reference voltage Vref1 may be provided outside the control unit 40 instead of being provided inside the overcurrent detection control unit 40a.

In the second embodiment described above, as in the case of Table 1 described above, even if the AC input voltage Vin (AC) is doubled, the power consumption, that is, the amount of heat generation is almost the same.
From this, it was confirmed that the present embodiment can suppress the heat generation amount of the circuit to a predetermined value without being affected by the input voltage, as compared with the conventional example.

Therefore, a large current can be prevented from flowing into the switching element Q1 as the input voltage V1 increases, and the operation of overcurrent protection can be made variable with respect to the change of the input voltage. Further, the power consumption at the time of overcurrent can be suppressed and the amount of heat generation can be suppressed without being affected by the magnitude of the input voltage V1.

In the first and second embodiments described above, a current transformer may be appropriately used for detecting the current Id flowing through the switching element Q1.

The present invention can be applied not only to the ON / ON single-stone circuit system but also to various switching systems such as the ON / OFF system, the two-stone system, and the four-stone system.

[0057]

As described above, in the switching regulator having the overcurrent protection function of the present invention,
A large current can be prevented from flowing into the switching element as the input voltage increases, and the operation of overcurrent protection can be made variable with respect to changes in the input voltage. Also,
The heat generation amount of the circuit at the time of overcurrent can be suppressed to a predetermined value without being affected by the magnitude of the input voltage. For this reason,
A radiator such as a heat sink can be downsized or omitted and can be made inexpensive.

Further, since the heat generation of the circuit element, which is the cause of the unstable circuit operation, can be reduced, the reliability of the switching regulator is improved, and the countermeasure against the heat generation of the circuit element need not be taken into consideration as compared with the conventional case, so that the degree of freedom in design is large. Become.

Further, the overcurrent detection resistor section has a power M.
When a power semiconductor element such as an OSFET is provided, the power semiconductor element is made conductive and non-conductive or linearly operated on the basis of the input voltage detected by the input voltage detecting means, and the input voltage is changed in units of mV. Since it is possible to follow changes, it is possible to perform highly accurate linear operation and conducting and non-conducting operations, and highly reliable overcurrent detection can be performed.

[Brief description of drawings]

FIG. 1 shows a switching regulator having an overcurrent protection function according to a first embodiment of the present invention, (a) is a circuit diagram, and (b) and (c) are operation characteristic diagrams of the circuit of (a). .

FIG. 2 shows a modified example of the combined resistance 60 of the first embodiment according to the present invention, (a) is a circuit diagram in which a resistance R10 is connected in series to a variable resistance element Q2, and (b) is a resistance to the variable resistance element Q2. R
It is a circuit diagram which connected resistance R20 in parallel to the circuit which connected 10 in series.

FIG. 3 shows a modification of the first embodiment according to the present invention,
(A) is a circuit diagram, (b) is an operation characteristic diagram of the circuit of (a).

FIG. 4 shows another modification of the first embodiment according to the present invention,
(A) is a circuit diagram, (b) and (c) are operation characteristic diagrams of the circuit of (a), and (d) is a modification of the circuit of (a).

FIG. 5 shows a switching regulator having an overcurrent protection function according to a second embodiment of the present invention, (a) is a circuit diagram, and (b) and (c) are operating characteristic diagrams of the circuit of (a). .

FIG. 6 shows a conventional switching regulator having an overcurrent protection function, (a) is a circuit diagram, and (b) is an operation characteristic diagram of the circuit of (a).

[Explanation of symbols]

10 diode bridge rectifier circuit 20 transformer 40 control unit 40a overcurrent detection control unit 50 overcurrent detection resistor unit 60 input voltage detection circuit unit Q1 switching element Q2, Q3 variable resistance element A error amplifier R70 combined resistance CO comparator V1 DC input voltage V3 Composite voltage Vref Reference voltage Vref 1 Reference voltage source Vref 'Variable reference voltage Vr Overcurrent reference voltage Vin (AC) AC input voltage D1, D2 Diode Id Current flowing in switching element Q1

Claims (5)

[Claims] 1. A switching regulator having an overcurrent protection function for obtaining a DC output from a pulsating current input by using the switching element (Q1),
1) is provided with an overcurrent detection resistance section (50) for converting a current value flowing into a voltage value and an input voltage detection circuit section (60) for detecting a voltage of the pulsating current input, and the overcurrent detection resistance section (50). 5
0) has a variable resistance element (Q2, Q3), and when the input voltage detected by the input voltage detection circuit section (60) is large, the variable resistance element (Q2, Q3) is the overcurrent detection resistance section. By increasing the resistance value of (50) and decreasing the resistance value when the input voltage is small, the voltage value converted by the overcurrent detection resistance unit (50) is larger than the input voltage. A switching regulator having an overcurrent protection function, which is constant or does not change much depending on the size of the switching regulator. 2. The variable resistance element is a power semiconductor element (Q
2), wherein the power semiconductor element (Q2) is configured to perform a conducting and non-conducting operation or a linear operation based on the input voltage detected by the input voltage detecting means (60). A switching regulator having an overcurrent protection function according to item 1. 3. The power semiconductor device (Q2) has a power M.
The switching regulator having an overcurrent protection function according to claim 2, wherein the switching regulator is an OSFET. 4. The variable resistance element comprises a low power type switching transistor (Q3), and the low power type switching transistor (Q3) is turned on or off based on the input voltage detected by the input voltage detection means (60). The switching regulator having an overcurrent protection function according to claim 1, wherein the switching regulator is configured to conduct. 5. A switching regulator having an overcurrent protection function for obtaining a DC output from a pulsating current input by using the switching element (Q1),
1) An overcurrent detection resistor section (50) for converting a current value flowing into the voltage value, an input voltage detection circuit section (60) for detecting a voltage of the pulsating current input, and the overcurrent detection resistance section (50). And an overcurrent detection control section (40a) for detecting an overcurrent state by comparing the converted voltage value of 1 above with an overcurrent reference voltage, and the input voltage detection circuit section (60) When the input voltage is large, the overcurrent reference voltage is decreased, and when the input voltage is small, the overcurrent reference voltage is increased to control the output of the overcurrent detection control unit (40a). The switching element (Q
A switching regulator having an overcurrent protection function, characterized in that the current flowing through 1) is reduced.