JP2001037084A - Active filter type switching power source circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power source for making a DC converter to stop surely and safely, when an active filter is stopped. SOLUTION: This active filer type switching power source circuit combines an active filter 1 with a DC converter 3, so as to improve power factor in response to high frequency. The power source circuit comprises an active filter output voltage monitoring means (active filter output voltage monitoring circuit 37) for monitoring the output voltage of the filter 1 and causing the converter 3 to stop surely and safely when the filter 1 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active filter type switching power supply circuit in which an active filter section is combined with a DC converter section to improve a power factor corresponding to a high frequency. The present invention relates to an active filter type switching power supply circuit that can reliably and safely stop a DC converter by operating a voltage monitoring circuit.

[0002]

2. Description of the Related Art In recent years, with the widespread use of electronic equipment using a switching power supply, a harmonic current to a power supply line has increased, causing a failure in other electronic equipment or causing a harmonic failure in a power transmission system or a power distribution system. Regulations are currently being considered to cause this. In order to cope with the harmonic regulation, a power supply circuit is required to have a further improved power factor. As an example, an active filter type switching power supply using an active filter has been proposed. The active filter type switching power supply is a power supply device in which the line consumption current is made a sine wave in phase with the input voltage by appropriately controlling the on-off operation of the switching transistor of the active filter circuit, and the power factor is greatly improved. is there. In this method, since the input current waveform is a sine waveform, the peak value of the input current is reduced, it can cope with a wide input voltage range, the load on the input line equipment of the device is reduced, and the waveform distortion is improved. There are advantages such as reduction of various harmonic disturbances and stabilization of the input voltage, so that the converter circuit can be downsized.

FIG. 7 shows a configuration diagram of a conventional active filter type switching power supply circuit. As shown in FIG. 7, this active filter type switching power supply circuit has an active filter section 1 and a DC converter section 3, and a noise filter section 5 and an input rush current suppression are provided at the input section of the active filter section 1. A circuit 7 is provided. The active filter unit 1 includes a first capacitor 11 connected to the output side of the bridge diode circuit 9,
Active filter control having a first switching FET 13, a second capacitor (input aluminum electrolytic capacitor) 15, a first coil 17, and a first diode 19, and connected to a gate terminal of the first switching FET 13 It has an IC 21. The reference voltage terminal 21 of the active filter control IC 21
Resistors 14, 16, and 18 are connected to a. Also,
The DC converter unit 3 includes a first winding 24 of a transformer 23 connected to an output side of the active filter unit 1.
And second switching FET (converter FET)
And a converter control IC 27 connected to the gate terminal of the converter FET 25. The second winding 29 and the second diode 31 of the transformer 23 are provided on the power supply voltage input terminal 27a side of the converter control IC 27. , And a third capacitor 33, and a fourth capacitor 35 is connected to the abnormality detection terminal 27 b of the converter control IC 27. Transformer 23
The first winding 24, the second winding 29, the third winding
, And an output winding 28 on the secondary side.

Next, the operation of the conventional active filter type switching power supply circuit is such that when an input voltage Vin is applied, the noise filter section 5, the resistor 7a of the input rush current suppressing circuit 7, the bridge diode circuit 9,
The first capacitor 11, the first coil 17, and the first
To the second capacitor 15 via the diode 19 of Vin.
A voltage of x√2 is applied. At this time, the triac 7b of the input rush current suppressing circuit 7 is kept off and the current is supplied through the resistor 7a, so that the input rush current is limited by the resistance value of the resistor 7a. The triac 7b of the input inrush current suppressing circuit 7 is connected to the converter FET2
5, the diode 7c, the resistor 7d, the capacitor 7
e, and becomes conductive, and thereafter supplies current to the active filter unit 1 and the DC converter unit 3 without passing through the resistor 7a.

Next, when the switching of the converter FET 25 is started by the activation of the converter control IC 27, a stable power supply voltage is supplied to the power supply voltage terminal 21C of the active filter control IC 21. IC21 is output terminal 2
1b, a signal is output from the active filter FET
Thirteen switching operations are performed. The output voltage of the active filter (the voltage across the second capacitor 15) is controlled by the booster circuit composed of the first coil 17, the switching FET 13, and the first diode 19.
The resistors 14, 1 based on the reference voltage 21 (terminal 21a)
The DC voltage is boosted to the DC voltage set by 6 and 18. This boosted voltage is smoothed by the second capacitor 15 and D
The current flowing through the first winding 24 and the converter FET 25 of the DC converter unit 3 by being input to the C converter unit 3 becomes input power / converter input voltage (active filter output voltage), so that the active filter unit 1 operates. A lower current flows by an amount corresponding to the boosted voltage when not performed. Further, the input current changes from a current waveform having a narrow conduction angle (a power factor of about 0.6) to a current waveform close to a sine wave due to the active filter operation, so that a lower current flows when the active filter is not operating due to an improvement in the power factor. .
Therefore, the current flowing through the noise filter unit 5, the triac 7b, the bridge diode circuit 9, the first coil 17, and the first diode 19 is also reduced. As described above, the line current consumption is set to a sine wave in phase with the input voltage,
Power factor is greatly improved.

[0006]

However, in the conventional active filter type switching power supply circuit shown in FIG. 7, an abnormality such as a component failure occurs in the active filter unit 1 and the active filter unit 1 operates. Is stopped, only the DC converter unit 3 may continue to operate. In this case, the active filter unit 1 does not reduce the current, so that the input current becomes the capacitor input current as shown in FIG. And greatly increases beyond the normal current shown in FIG.
As a result, the converter FET which is the primary side power element
25, a current (FIG. 5) which is much larger than the normal current (FIG. 3) flows through the bridge diode circuit 9, the input aluminum electrolytic capacitor 15, the first winding 24, etc. The deviation of the rating leads to damage and the operation of the switching power supply circuit stops. However, depending on the case, there may be a case where a component is ignited or smoked without a safety stop. In addition, as shown in FIG. 8, a method of adding a temperature protection element (TH1) to each of the above-mentioned components to safely stop the components is conceivable. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to operate an active filter output voltage monitoring circuit when an active filter is stopped to reliably stop a DC converter safely. It is an object of the present invention to provide an active filter type switching power supply circuit which can be used.

[0007]

In order to achieve the above object, the present invention is directed to an active filter type in which an active filter section is combined with a DC converter section to improve a power factor corresponding to a high frequency. In the switching power supply circuit, the output voltage of the active filter unit is monitored, and when the active filter unit is stopped, the DC voltage is monitored.
An active filter output voltage monitoring means for securely stopping the converter unit safely is provided. According to a second aspect of the present invention, the active filter output voltage monitoring means monitors a boosted voltage by detecting a voltage at a middle point of a voltage dividing resistor of an active filter output voltage setting circuit of the active filter section. It is characterized by. According to the first aspect of the present invention, the DC converter can be safely stopped when the active filter is stopped. According to the second aspect of the present invention, a general Zener diode having a lower Zener voltage can be used as the Zener diode of the active filter output voltage monitoring means.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an active filter type switching power supply circuit embodying the present invention.
As shown in FIG. 1, this active filter type switching power supply circuit has an active filter section 1 and a DC converter section 3 and an active filter output voltage monitoring circuit for monitoring the output voltage of the active filter section 1. 37. A noise filter 5 and an input rush current suppression circuit 7 are provided at the input of the active filter 1. The configurations of the active filter unit 1 and the DC converter unit 3 are the same as the configurations shown in FIG. That is, the active filter unit 1 includes the first capacitor 11 connected to the output side of the bridge diode circuit 9 and the first switching F
ET 13, a second capacitor (input aluminum electrolytic capacitor) 15, a first coil 17, and a first diode 19.
Filter control IC connected to the gate terminal
21. The resistors 14, 16, and 18 are connected to a reference voltage terminal 21a of the active filter control IC 21 as an active filter output voltage setting circuit. Further, the DC converter unit 3 includes a transformer 2 connected to an output side of the active filter unit 1.
3 first winding 24 and second switching FET
(Converter FET) 25 and a converter control IC 27 connected to the base terminal of the converter FET 25. The second winding 29 of the transformer 23 is connected to the power supply voltage input terminal 27a of the converter control IC 27. A second diode 31 and a third capacitor 33 are provided, and a fourth capacitor 35 is connected to the abnormality detection terminal 27b of the converter control IC 27.

Next, the active filter output voltage monitoring circuit (active filter output voltage monitoring means) 37, which is the gist of the present invention, is used to detect the abnormality of the output side of the second diode 31 of the DC converter section 3 and the converter control IC 27. The first transistor 39 and the first resistor 41 provided between the detection terminal 27b and the second resistor 43 and the second transistor provided between the base terminal of the first transistor 39 and the ground. 45, the output side of the second diode 31 and the second transistor 45
A third resistor 47 provided between the base terminal of the active filter unit 1 and a third resistor 47 provided between the base terminal of the second transistor 45 and the ground. A Zener diode 51 and a fourth resistor 53 provided between the output side of the diode 19 and the base terminal of the third transistor 49;
It has a fifth resistor 55 and a fourth capacitor 57 provided between the base terminal of the third transistor 49 and the ground. Here, regarding the operations of the active filter unit 1 and the DC converter unit 3,
The operation of the active filter output voltage monitoring circuit 37, which is the gist of the present invention, will be described because it has already been described in the section of the prior art.

In general, the active filter unit 1
Requires that the voltage across the second capacitor (input aluminum electrolytic capacitor) 15 be set to Vin × √2 + 10 V or more. Therefore, if the input voltage upper limit of the active filter type switching power supply circuit is 135
In the case of Vac, the voltage must be raised to about 201 Vdc or more by the active filter unit 1. When the voltage across the input aluminum electrolytic capacitor 15 is set to 210 Vdc, the input aluminum electrolytic capacitor 15 operates during the operation of the active filter unit 1. The voltage across the electrolytic capacitor 15 has a DC voltage waveform as shown in FIG. This active filter unit 1
In the operation of the active filter output voltage monitoring circuit 37 during the operation of the above, the Zener diode 51 is turned on by the voltage shown in FIG. 2, whereby the third transistor 49 is turned on, and the second and first transistors 49 are turned on. Transistors 45 and 39 are turned off and the converter control IC
27 operates normally. Here, the fifth resistor 55 is used.
In addition, the time constant of the fourth capacitor 57 prevents a malfunction of the active filter output voltage monitoring circuit 37 when the power is turned on. Next, when the active filter section 1 is stopped due to some abnormality, the voltage between both ends of the input aluminum electrolytic capacitor 15 is, as shown in FIG.
Vin × √2, which is a waveform in which general charge and discharge are repeated. Here, if the input voltage is 135 Vac, the voltage across the input aluminum electrolytic capacitor 15 is 191 Vdc
Approximately 20 Vdc lower than 210 Vdc at the time of the active filter operation, whereby the Zener diode 51 turns off, the third transistor 49 turns off,
The second and first transistors 45 and 39 are turned on, the converter control IC 27 is latched, and the DC converter unit 3 comes to a safe stop.

Next, a second embodiment of the active filter type switching power supply circuit according to the present invention will be described with reference to FIG. In the second embodiment, as shown in FIG. 6, a resistor 1 is an active filter output voltage setting circuit.
The midpoint A of the voltage dividing resistors 14, 16 of 4, 16, and 18 is monitored, and the other configuration operations are the same as those of the first embodiment shown in FIG. That is, the output side of the Zener diode 51 is connected to the midpoint A in order to monitor the midpoint A. With the above configuration, a general Zener diode having a lower Zener voltage can be used as the Zener diode 51.

[0012]

As described above, according to the present invention, the active filter output voltage monitoring circuit for securely stopping the DC converter section safely when the active filter section is stopped is provided, so that the entire power supply circuit can be prevented from being damaged.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an active filter type switching power supply circuit embodying the present invention.

FIG. 2 is a waveform diagram of a voltage across the input aluminum electrolytic capacitor when the active filter unit shown in FIG. 1 operates.

FIG. 3 is a waveform diagram of an input current to a DC converter unit when an active filter unit operates.

FIG. 4 is a waveform diagram of a voltage across the input aluminum electrolytic capacitor when the active filter unit shown in FIG. 1 operates.

FIG. 5 is a waveform diagram of an input current to the DC converter when the active filter is stopped.

FIG. 6 is a configuration diagram of a second embodiment of the active filter type switching power supply circuit according to the present invention.

FIG. 7 is a configuration diagram of a conventional active filter type switching power supply circuit.

FIG. 8 is a configuration diagram of another conventional active filter type switching power supply circuit.

[Explanation of symbols]

1. Active filter section 3. DC converter section 5. Noise filter section
7 input rush current suppressing circuit, 9 bridge diode circuit, 11 first capacitor, 13 first switching FET, 14, 16, 18 ...
Resistance, 15: second capacitor (input aluminum electrolytic capacitor), 17: first coil, 1
9: first diode, 21: active filter control IC, 23: transformer, 24: first winding, 25
... second switching FET (converter FET), 2
6: third winding 27: converter control IC 28: output winding
29 ... second winding, 31 ... second diode,
33 ... third capacitor, 35 ... fourth capacitor, 37 ... active filter output voltage monitoring circuit (active filter output voltage monitoring means), 39 ... first
Transistors 41, the first resistor, 4
3 ... second resistor, 45 ... second transistor, 47 ... third resistor,
49: third transistor, 51: Zener diode, 53: fourth resistor, 55: fifth resistor, 57: fourth capacitor.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G066 EA03 5H730 AA18 BB14 BB23 BB57 CC04 DD04 EE02 EE08 FD01 VV01 XC09 XX02 XX11 XX22 XX33 XX42 5H740 BA12 BB08 BC06 NN01

Claims (2)

[Claims] 1. A method for improving a power factor corresponding to a high frequency.
An active filter type switching power supply circuit combining an active filter unit with a C converter unit,
An active filter type switching power supply circuit, comprising: active filter output voltage monitoring means for monitoring an output voltage of the active filter section and securely stopping the DC converter section safely when the active filter section is stopped. 2. The active filter output voltage monitoring means monitors a boosted voltage by detecting a voltage at a middle point of a voltage dividing resistor of an active filter output voltage setting circuit of the active filter section. An active filter type switching power supply circuit according to claim 1.