JPH11164547A - Power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To take the surest measures to the fault of a smoothing capacitor, by providing a control circuit for switching element for stopping the switching operation of a switching element when the signal level of an inner output from an inner abnormality detection circuit exceeds overcurrent detection level which is previously set. SOLUTION: An overcurrent level is set in a control circuit for switching element 10. When the signal level of inner current ICE, which is supplied from an inner current detection IC3 exceeds the overcorrect level, switching operation of a switching element Q1 is stopped. A DC/DC converter connects a resistor for output current detection R2 connected to the output side of output smoothing capacitors C2-C5, and output current detection IC2 in which a non-inverted input terminal is connected to the input side of a resistor for output current detection R2 and an inverted input terminal to the output side of the resistor for output current detection R2 and detects output current IDC, and it connects the inverted input terminal to the output terminal of an operand amplifier for input current detection IC1 and detects inner current 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a power supply device,
More specifically, the present invention relates to a power supply device which has a protective measure for failure of a smoothing capacitor used for smoothing a DC output voltage.

[0002]

2. Description of the Related Art A step-down DC / D which is a kind of a power supply device.
A C-converter is a conventional step-down DC / DC converter that converts a DC input voltage to a low voltage and outputs the DC output voltage as a DC output voltage.
FIG. 5 shows a basic circuit configuration of the DC converter.

This step-down DC / DC converter comprises an input power supply E for supplying a predetermined input voltage VIN, and an input power supply E
An input capacitor C1 connected in parallel with
An input current detecting resistor R1 connected to the anode of the input current detecting resistor R1, a switching element (FET) Q1 connected after the input current detecting resistor R1, and a non-inverting input terminal on the input side of the input current detecting resistor R1. An inverting input terminal is connected to the output side of the input current detecting resistor R1, and an input current detecting operational amplifier IC1 for detecting an input current IIN, and the switching element Q1 based on the output of the input current detecting operational amplifier IC1.
1 sends a control signal to the gate of
1, a switching element control circuit 20 for performing switching operation, an output rectifying diode D1 for rectifying the switching output of the switching element Q1, and a rectified output from the output rectifying diode D1 to smooth the output voltage VOUT to a load resistor RL. Supply and output current (rated output current) IDC
, And an output smoothing choke coil L1 and output smoothing capacitors C2 to C5. Note that the switching element Q1 drain-source voltage (rated voltage) is VDS
And

The input current I to the switching element Q1 when the rated output current of the step-down DC / DC converter is supplied.
FIG. 6 shows waveforms of IN and the drain-source voltage VDS of the switching element Q1.

In this step-down DC / DC converter, the switching element control circuit 10 causes the signal level of the input current IIN detected by the input current detection operational amplifier IC1 to exceed a preset overcurrent detection level OL. In this case, the operation is performed so that the output current IDC does not exceed the overcurrent detection level OL or the switching operation of the switching element (FET) Q1 is stopped.

[0006]

However, the above-mentioned conventional step-down DC / DC converter has the following problems.

In this step-down DC / DC converter, when the output current I'DC is smaller than the rated output current IDC, the waveform of the output current I'DC and the smoothing capacitor C2
FIG. 7 shows the waveform of the DC current IC flowing when C5 fails.

That is, the conventional step-down DC / D shown in FIG.
In the case of a C converter, as shown in FIG.
When C is small, use smoothing capacitors C2 to C5.
When any or all of the capacitors fail, any or all of the resistance components of the failed smoothing capacitors C2 to C5 (equivalently represented by RC shown by a dotted line in FIG. 5 (actually, capacitors C2 to C5) DC current IC flows through C5).

In this case, an operational amplifier IC for input current detection
1 The overcurrent detection level OL of the input current IIN detected by
Since the input current IIN is not different from the rated current, the switching control of the switching element Q1 by the switching element control circuit 10 is continued, and the smoothing operation is performed until the input current IIN increases to the overcurrent detection level OL. The direct current IC is continuously supplied to any or all of the capacitors C2 to C5. As a result, there is a problem that the smoothing capacitor is heated and smokes.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a power supply device that can provide a thorough countermeasure in the event of a failure of a smoothing capacitor.

[0011]

According to the first aspect of the present invention,
In a power supply device, a DC input voltage is converted into a pulse voltage by a switching operation of a switching element, and the pulse voltage is rectified and smoothed by a rectifying and smoothing circuit including a smoothing capacitor and output as a DC output voltage. An input current detection circuit for detecting a DC input current, an output current detection circuit for detecting a DC output current output from the rectifying and smoothing circuit, and comparing detection outputs of the input current detection circuit and the output current detection circuit; An internal abnormality detection circuit for transmitting an internal output in conjunction with an increase in the detection output of the output current detection circuit due to the failure of the smoothing capacitor; and an internal output from the internal abnormality detection circuit for controlling a switching operation of the switching element. When the signal level exceeds the preset overcurrent detection level, the switching element It is characterized in that a control circuit switching element to stop the etching operation.

According to the present invention, an input current detection circuit detects a DC input current supplied to the switching element, and an output current detection circuit detects a DC output current output from the rectifying / smoothing circuit to detect an internal abnormality. The detection circuit compares the detection output of the input current detection circuit with the detection output of the DC output current detection circuit, and sends out an internal output that is linked to an increase in the detection output of the output current detection circuit due to the failure of the smoothing capacitor. When the element control circuit stops the switching operation of the switching element when the signal level of the internal output from the internal abnormality detection circuit exceeds a preset overcurrent detection level, a failure in the smoothing capacitor occurs. When this occurs, the switching operation of the switching element in this power supply device stops immediately, The Le, is prevented that heat and smoke during the smoothing capacitor failure, fault countermeasure is thorough.

According to a second aspect of the present invention, a DC input voltage is converted into a pulse voltage by a switching operation of a switching element, and the pulse voltage is rectified and smoothed by a rectifying and smoothing circuit including a smoothing capacitor and output as a DC output voltage. In the power supply device, an input current detection circuit using a resistor and an operational amplifier for detecting a DC input current supplied to the switching element, and a resistor and an operational amplifier for detecting a DC output current output from the rectifying and smoothing circuit are used. The output current detecting circuit compares the detected output of the input current detecting circuit with the detected output of the output current detecting circuit, and sends out an internal output linked to an increase in the detected output of the output current detecting circuit due to the failure of the smoothing capacitor. An abnormality detection circuit, which controls a switching operation of the switching element, and outputs a signal from the internal abnormality detection circuit. When the signal level of the part output exceeds the overcurrent detection level set in advance, is characterized in that it has a switching element control circuit for stopping the switching operation of the switching element.

According to the present invention, the same operation as in the first aspect of the present invention is achieved by using a configuration in which a resistor and an operational amplifier are used as an input current detecting circuit and a resistor and an operational amplifier are used as an output current detecting circuit. Can be.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS.

FIG. 1 is a circuit diagram showing a configuration of a step-down DC-DC converter which is a power supply device according to an embodiment of the present invention.

This step-down DC / DC converter has a predetermined input voltage VIN like the conventional DC / DC converter.
, An input capacitor C1 connected in parallel with the input power E, an input current detection resistor R1 connected to the anode of the input power E, and an input current detection resistor R1
Switching element (FET) Q1 connected to the subsequent stage of 1
A non-inverting input terminal is connected to the input side of the input current detecting resistor R1 and an inverting input terminal is connected to the output side of the input current detecting resistor R1 to detect an input current IIN. ) The switching element Q1 based on IC1 and the output of the operational amplifier IC1 for detecting the input current.
Control signal to the gate of the switching element Q1
, A rectifying diode D1 for rectifying the switching output of the switching element Q1, and smoothing the rectified output from the output rectifying diode D1 to supply the output voltage VOUT to the load resistor RL. Output current (rated output current) IDC
, And an output smoothing choke coil L1 and output smoothing capacitors C2 to C5.

In the present embodiment, the overcurrent level OX shown in FIGS. 2 to 4 is set in the switching element control circuit 10, and the signal level of the internal current IC3 supplied from the internal current detection IC3 is excessive. When the current level exceeds OX, the switching operation of the switching element Q1 is stopped.

Further, as shown in FIG. 1, the DC / DC converter of the present embodiment comprises an output current detecting resistor R2 connected to the output side of output smoothing capacitors C2 to C5,
A non-inverting input terminal is provided on the input side of the output current detection resistor R2.
An output current detection IC2 for detecting an output current IDC by connecting an inverting input terminal to the output side of the output current detection resistor R2;
An inverting input terminal is connected to an output terminal of the input current detecting operational amplifier IC1, an inverting input terminal is connected to an output terminal of the output current detecting IC2, and an internal current I3 is detected to provide the switching element control circuit 10 with. An internal current detection IC3 as an internal abnormality detection circuit to be transmitted is provided.

The input current detection resistor R1 and the input current detection IC1 constitute an input current detection circuit, and the output current detection resistor R2 and the output current detection IC2 constitute an output current detection circuit. .

The operation of the DC / DC converter having the above configuration will be described below.

The input current I to the switching element Q1 when the rated output current of this step-down DC / DC converter is supplied.
Internal current I detected by IN and internal current detection IC3
The waveform of 3 is shown in FIG. When the output current I'DC is smaller than the rated output current IDC, the waveform of the output current I'DC and the internal current I detected by the internal current detection IC 3
FIG. 3 shows the waveform of FIG.

In the DC / DC converter having the above configuration, as shown in FIG. 3, when the output current I'DC is smaller than the rated output current IDC, the output current detection IC is used.
The waveform of the output current I'DC detected by the internal current detection IC3 and the waveform of the internal current I3 detected by the internal current detection IC3 are as shown in FIG. 3, and the signal level of the internal current I3 output from the internal current detection IC3 is It does not reach the overcurrent detection level OL.

In this state, the smoothing capacitors C2 to C2
5, any one or all of the failed smoothing capacitors C2 to C5 (equivalently represented by RC shown by a dotted line in FIG. 1 (actually, the capacitor C2 To C5), a DC current IC flows as shown in FIG.

As a result, the potential of the non-inverting input terminal of the output current detection IC2 rises, and the detection current output from the output current detection IC2 also increases, thereby outputting from the internal current detection IC3. As shown in FIG. 4, the internal current changes from I3 before the failure to I'3, and the signal level of the internal current I'3 exceeds the overcurrent detection level OX.

Thus, the switching element control circuit 10 stops the switching control of the switching element Q1. The smoothing capacitor C that has failed in this way
DC current IC does not flow to any or all of 2 to C5, so that smoke caused by overheating of the smoothing capacitor can be prevented and burning can be avoided.

In the above-described embodiment, the case where four smoothing capacitors C2 to C5 are used has been described. However, it is needless to say that the number of smoothing capacitors is not particularly limited.

The present invention is applicable to various power supply circuits using a smoothing capacitor in a rectifying and smoothing circuit.

[0029]

According to the present invention described above, a countermeasure against a failure of the internal smoothing capacitor can be surely executed regardless of the magnitude of the DC output current. Can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a DC-DC converter according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of an input current to a switching element and an internal current detected by an internal current detection IC when a rated output current is supplied in the DC-DC converter of the present embodiment.

FIG. 3 is a waveform diagram of an input current to a switching element and an internal current detected by an internal current detection IC when a small output current is supplied in the DC-DC converter of the present embodiment.

FIG. 4 is a diagram illustrating an input current to a switching element, a DC current flowing through a smoothing capacitor, and an internal current detecting IC when a small output current is supplied and a smoothing capacitor fails in the DC-DC converter of the present embodiment; It is a waveform diagram of an internal current.

FIG. 5 is a circuit diagram showing a configuration of a conventional DC-DC converter.

FIG. 6 is a waveform diagram of an input current to a switching element and a drain-source voltage of the switching element when a rated output current is supplied in a conventional DC-DC converter.

FIG. 7 is a waveform diagram showing an input current to a switching element and a DC current flowing through a smoothing capacitor when a small output current is supplied and a smoothing capacitor fails in a conventional DC-DC converter.

[Explanation of symbols]

 10 Control circuit for switching element E Input power supply R1 Input current detecting resistor R2 Input current detecting resistor RL Load resistance IC1 Input current detecting operational amplifier IC2 Output current detecting operational amplifier IC3 Internal current detecting Q1 Switching element D1 Output rectifying diode C2 Smoothing capacitor L1 Output smoothing choke coil

Claims (2)

[Claims] 1. A power supply device for converting a DC input voltage into a pulse voltage by a switching operation of a switching element, rectifying and smoothing the pulse voltage by a rectifying and smoothing circuit including a smoothing capacitor, and outputting the DC voltage as a DC output voltage. An input current detection circuit for detecting a DC input current supplied to the element, an output current detection circuit for detecting a DC output current output from the rectifying and smoothing circuit, and detection outputs of the input current detection circuit and the output current detection circuit And an internal abnormality detection circuit that sends out an internal output linked to an increase in the detection output of the output current detection circuit due to the failure of the smoothing capacitor; and controls the switching operation of the switching element and detects the internal abnormality. When the signal level of the internal output from the circuit exceeds a preset overcurrent detection level, Power supply, characterized in that it comprises a switching element control circuit for stopping the switching operation of the quenching element. 2. A power supply apparatus for converting a DC input voltage into a pulse voltage by a switching operation of a switching element, rectifying and smoothing the pulse voltage by a rectifying and smoothing circuit including a smoothing capacitor, and outputting the DC voltage as a DC output voltage. An input current detection circuit using a resistor and an operational amplifier for detecting a DC input current supplied to the element; an output current detection circuit using a resistor and an operational amplifier for detecting a DC output current output from the rectifying and smoothing circuit; An internal abnormality detection circuit that compares detection outputs of an input current detection circuit and an output current detection circuit and sends out an internal output that is linked to an increase in the detection output of the output current detection circuit due to a failure of the smoothing capacitor; The switching operation of the switching element is controlled, and the signal level of the internal output from the internal abnormality detection circuit is controlled. When but exceeding the overcurrent detection level set in advance, the power supply apparatus characterized by and a control circuit switching element to stop the switching operation of the switching element.