JPS6352668A - Ripple voltage detection for power circuit - Google Patents

Abstract

PURPOSE:To quickly detect the deterioration of a smoothing capacitor, by detecting ripple voltage with a ripple voltage detection circuit provided in parallel to the smoothing capacitor, and by sounding an alarm or turning off the DC power source if the ripple voltage exceeds a prescribed value. CONSTITUTION:The output of a DC power source 1 is supplied to a load 8 through a choke coil 2, a transformer 6 and a rectification circuit 7. A DC cutoff transistor 5 is controlled by a pulse width control circuit 9 in response to the output voltage. A ripple voltage detection circuit 10 is provided in prallel to a smoothing capacitor 3. By this detection circuit 10 the ripple voltage of the smoothing capacitor 3 is detected. When this detected ripple voltage exceeds the prescribed value, an alarm ALM is sounded or the DC power source 1 is cut off.

Description

[Detailed Description of the Invention] [Summary] This is a ripple voltage detection method that detects the ripple voltage of a smoothing capacitor of a DC power supply on the primary side of a DC-DC converter, and detects when the ripple voltage becomes larger than a predetermined value. If this occurs, an alarm will be generated or the DC power source will be cut off.

(Industrial Application Field) The present invention relates to a ripple voltage detection method applied to a DC power supply used in a DC-DC converter that converts a constant DC voltage into DC voltages of different values and outputs the converted DC voltages.

[Prior Art] A conventional power supply circuit has a configuration shown in FIG. 4(A).

That is, FIG. 4 (1-) shows a power supply circuit consisting of a DC-DC converter, in which a reset diode 4' is connected to a reset winding 61' on the primary side of a transformer 6', and a reset diode 4' is connected to a secondary winding 62' of a transformer 6'.
A DC power supply 1r, a choke coil 2', and a DC intermittent transistor 5' are connected in series to ', and a smoothing capacitor 3' is connected in parallel to the secondary winding 63'.A rectifier circuit 7' and a load are connected to the secondary winding 63'. 8', and further supplies the output voltage of the rectifier circuit 7' to the load 8' and pulse width control circuit 9'.
The signal was fed back to the base of the transistor 5' via the transistor 5'.

With this configuration, the drive signal from the pulse width control circuit 9' (Fig. 4 (B-1)) turns the transistor 5' on and off (Fig. 4 (B-2)), and converts the DC of the DC power supply 1' into AC. Conversion (Fig. 4 (B-3)) L, transformer 6' steps up or steps down the voltage, and the AC obtained on the secondary side is rectified by a rectifier circuit 7' to supply a predetermined stable DC voltage to the load 8. ′
is supplied to.

[Problem that the invention seeks to solve]

As mentioned above, the conventional power supply circuit includes one of the transformers 6'.
The next winding has a smoothing capacitor 3 in parallel with the DC power supply 1'.
′ is connected.

However, this smoothing capacitor 3' is normally formed of an electrolytic capacitor, which deteriorates over time and its impedance may become very large.

When the smoothing capacitor 3' deteriorates, the ripple current increases (FIG. 4, (B-4)), and the ripple voltage also increases accordingly (FIG. 4, (B-5)).

As a result, the choke coil 2' generates heat and the voltage on the negative side becomes unstable, resulting in unstable output.
There is a problem that it becomes useless as a power supply circuit.

[Means for solving problems]

An object of the present invention is to detect deterioration of a smoothing capacitor in a power supply circuit and to prevent malfunction.For this purpose, as shown in FIG.
A DC power supply 1, a choke coil 2, and a DC intermittent transistor 5 are connected in series to the DC power source 1, and a smoothing capacitor 3 is connected in parallel to the rectifier circuit 7 and a load 8 to the secondary winding 63 of the transformer 6. In a power supply circuit configured to feed back the output voltage of the circuit 7 to the DC intermittent transistor 5 via the pulse width control circuit 9, a ripple voltage detection circuit 10 is provided in parallel to the smoothing capacitor 3, and the detection circuit 10 The ripple voltage of the smoothing capacitor 3 is detected, and when the detected ripple voltage exceeds a predetermined value, an alarm ALM is generated or the DC power supply 1 is cut off.

[For production]

As described above, according to the present invention, the ripple voltage detection circuit 10 is provided in parallel with the smoothing capacitor 3, and when a ripple voltage of more than a predetermined value is detected, an alarm is generated, the switch 11 is opened, and the power supply is turned off. cut off.

Therefore, deterioration of the smoothing capacitor 3 can be quickly discovered.
Furthermore, it has become possible to prevent malfunctions in the power supply circuit.

〔Example〕

The invention will now be explained by way of example with reference to the accompanying drawings.

FIG. 2 is a diagram showing an embodiment of the present invention. The embodiment shown in FIG. 2 differs from the conventional one in that a ripple voltage detection circuit 10 is provided.

This ripple voltage detection circuit 10 includes a capacitor 101,
106, resistors 102, 103, 107, a variable resistor 104, and a transistor 108.

The ripple voltage of the smoothing capacitor 3 is detected by the capacitor 101 and the resistor 102, and the transistor 108 detects that the ripple voltage exceeds a predetermined value.
The relay is activated when the voltage exceeds 05.

In addition, the rectifier circuit 7 on the secondary side is well known,
It is composed of diodes 71 and 72, a choke coil 73, and a capacitor 74.

Hereinafter, the operation of the embodiment shown in FIG. 2 having the above configuration will be explained as follows.
This will be explained based on the diagram.

First, a drive signal is input from the pulse width control circuit 9 to the base of the transistor 5 (FIG. 3(A)).

When this drive signal is rHJ, the transistor 5 is turned on, and when it is rLJ, it is turned off (FIG. 3(B)).

FIG. 3(B) shows the voltage between the collector and base of the transistor 5.

As the transistor 5 turns on and off (FIG. 3(B)), a collector current flows through the primary winding 62 (FIG. 3(C)).

When the smoothing capacitor 3 deteriorates, the collector current (
A ripple current of approximately the same magnitude as that shown in FIG. 3(C)) flows (FIG. 3(D)), and a ripple voltage appears across the capacitor 3 (FIG. 3(E)).

Here, the impedance of the capacitor 101 is Z1°.

is much larger than the resistance R1゜2 of the resistor 102, that is, Z
,. l 〉〉If RI02, smoothing capacitor 3
The ripple voltage appearing across the terminal can be taken out by the resistor 102 (FIG. 3(F)).

When the voltage regulated across this resistor 102 exceeds the voltage VIIE between the base and emitter of the transistor 108 (FIG. 3(F)), the transistor 108 turns on and collector current flows through the resistor 107 (FIG. 3(F)). Figure (G)).

As the collector current (Fig. 3 (G)) is interrupted, the capacitor 106 is repeatedly charged and discharged (Fig. 3 (H)), and the voltage of the capacitor 106 is
When the touching voltage VRL□ of 5 is exceeded, the relay operates, its contact (r7!1) 12 closes, and an alarm ALM is generated. Alternatively, a switch 11 that operates in conjunction with the relay coil (RLI) 105 may be provided, and the power supply 1 may be cut off by opening the switch 11.

〔Effect of the invention〕

As described above, according to the present invention, a ripple voltage detection circuit is provided in parallel with the smoothing capacitor 3, and when a ripple voltage is detected, an alarm can be generated or the power can be cut off.

Therefore, deterioration of the smoothing capacitor can be quickly discovered and malfunctions of the power supply circuit can be prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing an embodiment of the invention, FIG. 3 is an explanatory diagram of the operation of the present invention, and FIG. 4 is an explanatory diagram of the prior art. DESCRIPTION OF SYMBOLS 1... DC power supply, 2... Choke coil, 3... Smoothing capacitor, 4... Reset diode, 5... DC intermittent transistor, 6... Buck-boost transformer, 7... - Rectifier circuit, 8... Load, 9... Pulse width control circuit, 10... Ripple voltage detection circuit.

Claims (1)

[Claims] A DC power supply (1), a choke coil (2), and a DC intermittent transistor (5) are connected in series to the primary winding (62) of the buck-boost transformer (6), and a smoothing capacitor is connected in parallel to the primary winding (62) of the buck-boost transformer (6). (3) and also connect the rectifier circuit (7) and load (8) to the secondary winding (63) of the transformer (6).
) in which the output voltage of the circuit is fed back to the DC intermittent transistor (5) via the pulse width control circuit (9), a ripple voltage detection circuit (10) connected in parallel to the smoothing capacitor (3). The detection circuit (10) detects the ripple voltage of the smoothing capacitor (3), and if the detected ripple voltage exceeds a predetermined value, an alarm (ALM) is generated or the DC power supply ( 1) A ripple voltage detection method for a power supply circuit, which is characterized by cutting off.