JPH0974761A - Switching type constant voltage power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable output voltage even when momentary shutdown of commercial ac supply occurs, by providing a momentary-variation/shutdown countermeasure circuit which keeps output voltage constant when the commercial ac supply is not supplied for a specified period. SOLUTION: A momentary-variation/shutdown countermeasure circuit 7 consists of diodes D1 and D2 and a smoothing capacitor C1 on a system 1 side, and a power-factor improvement circuit 8 consists of a diode D3 on a system 2 side, and, the smoothing capacitor C1 smooths the voltage rectified by a diode bridge DB1, for supplying power to a transformer T1. While a switching FET Q1 is on-state, power is supplied to a load 6 by the charge energy of a secondary side capacitor C2 of a transformer 1, and, while a switching FET Q1 is off-state, the power is supplied to the load 6 by the excitation energy of the transformer 1. At this time, the switching FET Q1 is controlled with a control circuit 5, so that stable voltage is obtained at output terminals 3 and 4 even when input ac voltage Vin is momentary shut down.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching type constant voltage power supply device for producing a DC voltage from a commercial AC voltage.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a configuration of a conventional switching type constant voltage power supply device for a flyback converter including a power factor correction circuit. 1, 2,
Is an AC voltage input terminal, DB1 is a diode bridge that rectifies an AC power supply voltage, T4 is a high frequency transformer, D4 is a diode that rectifies a secondary side output voltage, C2 is a smoothing capacitor, and 3 and 4 are DC voltage output terminals. . A control circuit 5 detects a DC output voltage, compares and amplifies the detected voltage with a built-in reference voltage, and controls a switching FET (electrolytic effect transistor) Q1 so that the output becomes constant. This is an amplifier circuit for driving the high-frequency pulse width modulation circuit and switching FET "Q1". Reference numeral 6 is a load connected between the DC voltage output terminals 3 and 4.

The operation of the switching type constant voltage power supply device having such a configuration will be described.

When the AC power source Vin is connected between the AC voltage input terminals 1 and 2, full-wave rectification is performed by the diode bridge DB1, and by switching the switching FET "Q1", a current flows through the high frequency transformer T4 and power is supplied. Supplied.

During the period when the switching FET "Q1" is turned on and the current is flowing in the high frequency transformer T4, the energy charged in the capacitor C2 on the secondary side of the high frequency transformer T4 causes the DC voltage output terminals 3 and 4 to be mutually connected. Power is supplied to the load 6 connected to.

In the control circuit 5, the DC voltage output terminals 3, 4
The direct current voltage at is detected, the detected voltage is compared and amplified with the built-in reference voltage, and the switching FET "Q1" is controlled so that the output becomes constant.

FIG. 6 shows the voltage waveform and current waveform at point A in FIG. FIG. 6A shows the voltage waveform at point A,
(B) is a current waveform at point A.

The current flowing at the point A is as shown in FIG. 6, and the power factor can be improved by widening the conduction angle of the input current.

[0009]

However, in the above-mentioned conventional example, when the commercial AC power supply is instantaneously interrupted, the high frequency transformer T4 is operated during the instantaneous interruption.
Is not supplied with power and the output voltage drops,
There is a problem that a stable output voltage cannot be obtained.

The present invention has been made in view of the above problems of the above-mentioned conventional technique, and an object of the present invention is to provide a switching type constant voltage power supply device capable of keeping an output voltage constant. It is the one we are trying to provide.

[0011]

In order to achieve the above object, a switching type constant voltage power supply device according to claim 1 is a switching type constant voltage power supply device for producing a direct current voltage from a commercial alternating current voltage, and a commercial alternating current power supply is input. And a power factor correction circuit for improving the power factor by widening the conduction angle of the input current connected to the rectifier circuit for rectifying the commercial AC power supply, and an output voltage when the commercial AC power supply is not supplied for a certain period of time. It is characterized in that it is provided with a momentary change / instantaneous interruption countermeasure circuit for keeping it constant.

In order to achieve the same object, a switching type constant voltage power supply device according to a second aspect is the switching type constant voltage power supply device according to the first aspect, in which a capacitor is used in the circuit for preventing instantaneous change / interruption, When the commercial AC power supply is not supplied for a certain period of time, the output is kept constant by the energy stored in the capacitor.

To achieve the same object, a switching type constant voltage power supply device according to a third aspect is the switching type constant voltage power supply device according to the second aspect, wherein an effective value or a peak voltage value of the output voltage of the rectifier circuit is set. An AC input voltage detection circuit for detecting is provided, energy is not supplied from the capacitor when the commercial AC power supply is normally supplied, and only when the commercial AC power supply is not normally supplied from the capacitor It is characterized by supplying the energy of.

To achieve the same object, a switching type constant voltage power supply device according to a fourth aspect is the switching type constant voltage power supply device according to the second aspect, in which an auxiliary winding output for detecting an output voltage of the transformer auxiliary winding is detected. Equipped with a value detection circuit,
Energy is not supplied from the capacitor when the commercial AC power supply is normally supplied, and energy is supplied from the capacitor only when the commercial AC power supply is not normally supplied. To do.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) First, the first embodiment of the present invention will be described.
An embodiment will be described with reference to FIGS. FIG.
FIG. 3 is a block diagram showing a configuration of a switching type constant voltage power supply device for a flyback converter according to a first embodiment of the present invention, in which the same parts as those in FIG. It is attached. In FIG.
5 is different from the configuration shown in FIG.
1, D2, D3 and the capacitor C1 are added. Then, the diodes D1 and D2 and the smoothing capacitor C1 constitute a circuit 7 against instantaneous change / instantaneous interruption. Further, the power factor correction circuit 8 is configured on the side of the system 2 in parallel with the system 1 by the diode D3.

The smoothing capacitor C1 smoothes the voltage rectified by the diode bridge DB1 and supplies power to the transformer T1.

Next, the operation of the switching type constant voltage power supply device having the above configuration will be described.

When an AC power source Vin is connected between the AC voltage input terminals 1 and 2, the diode bridge DB1 performs full-wave rectification, and the output is divided into a system 1 and a system 2. The current flowing in the system 1 is the diode D that blocks the reverse current.
The smoothing capacitor C1 is charged via 1 and electric power is supplied to the transformer T1 via the reverse current blocking diode D2.

The current flowing in the grid 2 supplies power to the transformer T1 via the diode D3 for blocking the reverse current.

During the period when the switching FET "Q1" is turned on and the current is flowing in the transformer T1, the capacitor C2 is provided on the secondary side of the transformer T1 as in the conventional example described above.
The energy charged in the DC voltage output terminal 3,
Power is supplied to a load 6 connected between the four.

When the switching FET "Q1" is turned off and no current flows in the transformer T1, this transformer T1
On the secondary side of the transformer T1, the excitation energy of the transformer T1 smoothes the capacitor C2 through the diode D4 and supplies power to a load (not shown) connected to the DC voltage output terminals 3 and 4.

In the control circuit 5, the DC voltage output terminals 3, 4
The direct-current voltage is detected, the detected voltage is compared and amplified with the built-in reference voltage, the switching FET "Q1" is controlled so that the output becomes constant, and the output voltage is kept constant.

In FIG. 1, when the winding ratio of the first winding N1 and the second winding N2 of the transformer T1 is set to 1: 1, the voltage at A, that is, V (DB1) out, is the AC power supply Vin. During a period (t1, t2, t3 in FIG. 2) larger than 1/2 of the AC peak voltage Vp, the voltage at A occurs at the voltage V2, and the voltage at A, that is, V
During a period (t1 in FIG. 2) in which (DB1) out is smaller than 1/2 of the AC peak voltage Vp of the AC power supply Vin,
A voltage that is half the voltage V1 is generated as the voltage V2.

FIG. 2 shows waveforms of currents flowing at points A, B and C in FIG.

The output voltage of the diode bridge DB1 in FIG. 1 is V (DB1) out, the voltage across the smoothing capacitor C1 is Vc1, and each voltage waveform is shown in FIG. 2 (a). The current waveform at point A in FIG. 1 is shown in FIG. The current waveform at point C in FIG. 1 is shown in FIG. The current waveform at point B in FIG. 1 is shown in FIG.

Next, each current waveform will be described.

In the section t1 of FIG. 2, V (DB1)
In the section where out is higher than 1/2 Vp, in system 1, the voltage across the smoothing capacitor C1 is higher than the voltage at point A, the smoothing capacitor C1 is not charged, and at point B No current is flowing. In the system 2, the voltage on the anode side of the diode D3 is higher than that on the cathode side, and the current shown in FIG. 2 flows.
Therefore, at point A, only the current flowing at point C is flowing.

In the section t2 of FIG. 2, similarly to the section t1, V (DB1) out is a section higher than 1/2 Vp, and the voltage across the smoothing capacitor C1 is A.
The voltage becomes lower than the voltage at the point, the smoothing capacitor C1 is charged, and the charging current shown in FIG. 2D flows through the point B. In the system 2, the voltage on the anode side of the diode D3 is higher than that on the cathode side, and the current shown in (c) of FIG. 2 flows. Therefore, at point A,
A combined current of the currents flowing at points B and C shown in (b) of FIG.

In the section t3 of FIG. 2, V (DB1) out is higher than 1/2 Vp as in the section t1, and in the system 1, the voltage across the smoothing capacitor C1 is the voltage at the point A. Higher than that, the smoothing capacitor C1 is not charged, and no current flows to the point B.
In the system 2, the voltage on the anode side of the diode D3 is higher than that on the cathode side, and the current shown in (c) of FIG. 2 flows. Therefore, at point A, only the current flowing at point C is flowing.

In the section t4 of FIG. 2, V (DB1)
In the section where out is lower than 1/2 Vp, in system 1, the voltage at both ends of the smoothing capacitor C1 is higher than the voltage at point A, the smoothing capacitor C1 is discharged, and the current at point B is Is not flowing. In system 2,
The cathode side of the diode D3 is higher in voltage than the anode side, and no current flows to the point C as shown in FIG. 2 (c). Therefore, no current flows at point A.

As described above, during the period in which the input AC current is constantly supplied, the input current as shown in FIG. 2B is supplied to the circuit, and a stable output voltage can be obtained.

Even if the input AC power source is momentarily cut off for a short period of time, as described above, the conduction angle of the input current is widened to improve the power factor and the smoothing capacitor C1 holds energy. Therefore, by releasing this energy, the input of the transformer T1 can be maintained, and a constant voltage is always applied to the DC voltage output terminals 3, 4
Can be supplied to

The conduction angle of the current flowing through the circuit can be adjusted by changing the winding ratio of the first winding N1 and the second winding N2 of the transformer T1.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
The embodiment will be described with reference to FIG. FIG. 3 is a block diagram showing a configuration of a switching type constant voltage power supply device of a flyback converter according to a second embodiment of the present invention. In FIG. 3, the same parts as those in FIG. It is attached. 3 is different from FIG. 1 in that the reverse current blocking diode D2 is removed from the configuration of FIG. 1 and an AC input voltage detection circuit 9 and a switch element 10 are added to the configuration of FIG.

The AC input voltage detection circuit 9 is a circuit for detecting the effective value of the full-wave rectified AC input voltage which is the output of the diode bridge DB1, and according to the detected value,
It outputs a signal for controlling ON / OFF of the switch element 10. The switch element 10 is off in a steady state in which a correct input voltage is always supplied, and the smoothing capacitor C1 and the transformer T2 are not electrically connected.

Next, the operation of the switching type constant voltage power supply device having the above configuration will be described.

When an AC power source Vin is connected between the AC voltage input terminals 1 and 2, full-wave rectification is performed by the diode bridge DB1 and the output is a diode D3 for backflow prevention.
Power is supplied to the transformer T2 via the.

The switching FET "Q1" is turned on, energy is stored in the transformer T2, and the switching FE
When T "Q1" is off, its energy is diode D4
Power is supplied to the load 6 connected between the DC voltage output terminals 3 and 4 via.

In the control circuit 5, the DC voltage output terminals 3, 4
The direct-current voltage is detected, the detected voltage is compared and amplified with the built-in reference voltage, the switching FET "Q1" is controlled so that the output becomes constant, and the output voltage is kept constant.

The AC input voltage detection circuit 9 detects the effective value of the full-wave rectified input voltage, and switches the switch element 10 when the effective value of the commercial AC voltage, which is the AC input voltage, drops below a certain value. By turning on and supplying the energy charged in the smoothing capacitor C1 to the transformer T2, a stable output is supplied to the DC voltage output terminals 3 and 4 even when a voltage drop or momentary interruption of the commercial AC power supply occurs. can do.

In this way, by removing the large-capacity capacitor from the commercial AC rectifier circuit load, the conduction angle of the input current can be widened and the power factor can be improved, and the energy held in the smoothing capacitor C1 should just happen. , Even if the commercial input voltage drops for a short time or is interrupted for a short time,
By releasing the energy held in the smoothing capacitor C1, the input of the transformer T2 can be maintained, and a constant output voltage can be supplied to the DC voltage output terminals 3 and 4 at all times.

(Third Embodiment) Next, the third embodiment of the present invention will be described.
The embodiment will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration of a switching constant voltage power supply device for a flyback converter according to a third embodiment of the present invention. In FIG. 4, the same parts as those in FIG. It is attached. 4 is different from FIG. 3 in that the AC input voltage detection circuit 9 is deleted from the configuration of FIG. 3 and the auxiliary winding output voltage value detection circuit 11, the rectifying diode D5 and the smoothing capacitor C3 are added to the configuration of FIG. That is added.

The switch element 10 is off in a steady state where a correct input voltage is always supplied, and the smoothing capacitor C1 and the transformer T3 are not electrically connected.

The transformer T3 is obtained by adding an auxiliary winding to the transformer T2 of FIG. 3, and the auxiliary winding output voltage value detection circuit 11 is provided at the auxiliary winding output through the rectifying diode D5 and the smoothing capacitor C3. It is connected. The auxiliary winding output voltage value detection circuit 11 is a circuit that detects the auxiliary winding output voltage value of the transformer T3 and outputs a signal for turning on the switch element 10 when the detected voltage value becomes a certain value or less. is there.

Next, the operation of the switching type constant voltage power supply device having the above configuration will be described.

When an AC power source Vin is connected between the AC voltage input terminals 1 and 2, full-wave rectification is performed by the diode bridge DB1, and the output is a reverse current blocking diode D3.
Power is supplied to the transformer T3 via the.

The switching FET "Q1" is turned on, energy is stored in the transformer T3, and the switching FE
When T "Q1" is off, its energy is diode D4
Power is supplied to the load 6 connected between the DC voltage output terminals 3 and 4 via.

In the control circuit 5, the DC voltage output terminals 3, 4
The direct-current voltage is detected, the detected voltage is compared and amplified with the built-in reference voltage, the switching FET "Q1" is controlled so that the output becomes constant, and the output voltage is kept constant.

The auxiliary winding output voltage value detection circuit 9 detects the output voltage value of the auxiliary winding of the transformer T3, and when the detected voltage value falls below a certain value, the switch element 10 is detected.
Is turned on and the energy charged in the smoothing capacitor C1 is supplied to the transformer T3, so that a stable output can be provided to the DC voltage output terminals 3 and 4 even when the voltage of the commercial AC power supply drops or a momentary interruption occurs. Can be supplied.

In this way, by removing the large-capacity capacitor from the commercial AC rectifier circuit load, the conduction angle of the input current can be widened and the power factor can be improved, and the energy held in the smoothing capacitor C1 should just happen. , Even if the commercial input voltage drops for a short time or is interrupted for a short time,
By releasing the energy held in the smoothing capacitor C1, the input of the transformer T3 can be maintained, and a constant output voltage can be always supplied to the DC voltage output terminals 3 and 4.

[0052]

As described above in detail, according to the switching type constant voltage power supply device of the present invention, even if the commercial input voltage drops for a short period of time or is interrupted for a short time, measures against instantaneous change / interruption can be obtained. By releasing the energy stored in the circuit, it is possible to maintain the input power of the transformer, and it is possible to constantly supply a constant output to the load.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a switching type constant voltage power supply device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a waveform of each part in the switching constant voltage power supply device.

FIG. 3 is a block diagram showing a configuration of a switching type constant voltage power supply device according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a switching type constant voltage power supply device according to a third embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional switching type constant voltage power supply device.

FIG. 6 is a diagram showing a waveform of each part in the conventional switching type constant voltage power supply device.

[Explanation of symbols]

 1 Commercial AC voltage input terminal 2 Commercial AC voltage input terminal 3 DC voltage output terminal 4 DC voltage output terminal 5 Control circuit 6 Load 7 Instantaneous change / interruption countermeasure circuit 8 Power factor improvement circuit 9 AC input voltage detection circuit 10 Switch element 11 Auxiliary winding output voltage detection circuit DB1 Diode bridge D1 Reverse current blocking diode D2 Reverse current blocking diode D3 Reverse current blocking diode D4 Rectifying diode D5 Rectifying diode C1 Smoothing capacitor C2 Smoothing capacitor C3 Smoothing capacitor T1 High frequency transformer T2 High frequency transformer T3 High frequency transformer Q1 Switching FET

Claims (4)

[Claims] 1. A switching type constant voltage power supply device for generating a direct current voltage from a commercial alternating current voltage, wherein a power is provided by widening a conduction angle of an input current connected to a rectifier circuit for rectifying the commercial alternating current power supply as an input. A switching type constant voltage power supply comprising a power factor correction circuit for improving the power factor and a circuit for preventing momentary change / interruption that keeps the output voltage constant when the commercial AC power supply is not supplied for a certain period. apparatus. 2. A capacitor is used for the circuit for preventing momentary change / interruption, and the output is kept constant by the energy stored in the capacitor when the commercial AC power supply is not supplied for a certain period of time. 1. The switching type constant voltage power supply device according to 1. 3. An AC input voltage detection circuit for detecting an effective value or a peak voltage value of an output voltage of the rectifier circuit,
Energy is not supplied from the capacitor when the commercial AC power supply is normally supplied, and energy is supplied from the capacitor only when the commercial AC power supply is not normally supplied. The switching type constant voltage power supply device according to claim 2. 4. An auxiliary winding output value detection circuit for detecting an output voltage of a transformer auxiliary winding is provided, and energy is not supplied from the capacitor when the commercial AC power supply is normally supplied. 3. The switching type constant voltage power supply device according to claim 2, wherein energy is supplied from the capacitor only when the commercial AC power supply is no longer normally supplied.