JP2600224Y2 - Switching power supply - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention relates to an AC / DC module and a DC / DC module which are provided separately.
The present invention relates to a switching power supply device having a control terminal for externally controlling the supply of a DC output voltage to a / DC module.

[0002]

2. Description of the Related Art Conventionally, in a switching power supply for converting an AC voltage from a commercial power supply to a predetermined DC output voltage, an AC / DC converter for converting an AC input voltage to a DC input voltage.
Module and DC /
By dividing the DC module and the DC module respectively, the DC / D
There is known a C module that is made smaller and thinner.

FIG. 2 shows an example of a circuit diagram of such a switching power supply device. In FIG.
C module, 2 is a DC / DC module, AC
The AC input voltage Vi1 from the commercial power supply 3 is supplied between the input terminals + VIN1 and -VIN1 of the / DC module 1.
The AC input voltage Vi1 is rectified and smoothed by the rectifier circuit 4 such as a diode bridge and the smoothing capacitor 5, and the DC input voltage Vi is applied between the output terminals + VOUT1 and -VOUT1.
Output as 2. Further, between the input terminal + VIN1 and the rectifier circuit 4, a current limiting resistor 6, a triac 7 connected to both ends of the resistor 6, and a triac starting circuit 8 for supplying a drive signal to the gate of the triac 7 are provided. An inrush current prevention circuit 9 composed of The inrush current prevention circuit 9 keeps the triac 7 in the off state until the AC input voltage Vi1 reaches a predetermined voltage level, thereby reducing the inrush current when the power is turned on.
On the other hand, when the AC input voltage Vi1 exceeds a predetermined voltage level, the triac 7 is turned on via the triac starting circuit 8 in order to reduce the power loss due to the resistor 6, whereby the triac is turned on in a steady state. The input current is caused to flow through 7.

The output terminal of the AC / DC module 1 + VOU
T1, -VOUT1 and input terminal of DC / DC module 2 +
VIN2 and -VIN2 are connected to each other, and the DC input voltage Vi2 is applied to the primary winding of the transformer 11 constituting the DC / DC module 2 and the MOS as a switching element.
It is applied to a series circuit with the type FET12. And FET
By switching 12, the voltage induced in the secondary winding of the transformer 11 passes through the rectifying / smoothing circuit 13 and becomes a DC output voltage Vo from the output terminals + VOUT2, −VOUT2 to the load 14.
And the fluctuation of the DC output voltage Vo is detected by the voltage detection circuit 15, and the amount of the change is insulated and transmitted to the phototransistor 17 via the light emitting diode 16 of the photocoupler. At this time, the control circuit 18 controls the pulse conduction width of the drive signal supplied to the FET 12 based on the output signal of the phototransistor 17, whereby a stable DC output voltage Vo is obtained.

The control circuit 18 includes an on / off control circuit.
The ON / OFF control circuit 19 is provided with an external control terminal CNT. And
The on / off control circuit 19, when the control terminal CNT and the input terminal -VIN2 are in a short-circuit state, as shown by a chain line in FIG.
The DC output voltage Vo is supplied to the load 14, while the control terminal C
When NT and the input terminal -VIN2 are open, the pulse of the drive signal is forcibly stopped to cut off the supply of the DC output voltage Vo. That is, the control terminal CNT and the input terminal −V
By short-circuiting or opening between IN2, the supply of the DC output voltage Vo can be externally controlled.

[0006]

In the above prior art, when the commercial power supply 3 is turned on, the DC / DC module 2 starts up with the DC input voltage Vi2 being low. When an excessive current flows in, particularly when a breaker or a fuse is provided in the DC / DC module 2 for overcurrent protection, these elements are easily damaged. At the same time, AC / DC
Since an excessive current is also generated on the input side of the module 1, the resistor 6 constituting the inrush current prevention circuit 9 generates heat, which is dangerous.

Therefore, the present invention solves the above problems,
Provided is a switching power supply device that can effectively use a control terminal of a DC / DC module and prevent an excessive current from flowing into an input side of the DC / DC module in a state where a DC input voltage is low. Aim.

[0008]

According to the present invention, there is provided an AC / DC module for converting an AC input voltage to a DC input voltage, and a DC / DC module connected to the AC / DC module for supplying a stable DC output voltage. Wherein the DC / DC module has a control terminal for externally controlling the supply of the DC output voltage, and the AC / DC module has a voltage detection circuit for detecting the input voltage. And a detection terminal connected to the output side of the voltage detection circuit, wherein the voltage detection circuit controls the control terminal of the DC / DC module via the detection terminal until the input voltage reaches a predetermined level. Thus, the supply of the DC output voltage is stopped.

[0009]

With the above arrangement, the voltage detection circuit of the AC / DC module can prevent the DC output voltage from being supplied from the DC / DC module until the DC input voltage from the AC / DC module reaches a predetermined level. The DC / DC module is controlled by the control terminal via the detection terminal. This effectively prevents the excessive current from flowing into the input side of the DC / DC module when the DC input voltage is low by effectively using the control terminal of the DC / DC module that controls the supply of the DC output voltage from outside. it can.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the same portions as those in the circuit diagram of FIG. 2 in the conventional example are denoted by the same reference numerals, and detailed description of the common portions will be omitted. In the figure,
Output terminal in AC / DC module 1 + VOUT1, -VOU
A voltage detection circuit for detecting the DC input voltage Vi2 between T1
The detection result of the voltage detection circuit 21 is supplied as a detection signal to the base of the transistor 22 as a switch. The emitter of the transistor 22 is connected to the output terminal -VOUT1 and the external detection terminal ENA connected to the control terminal CNT of the DC / DC module 2 is connected to the emitter of the transistor 22. , The configuration is exactly the same as that of FIG.

Next, the operation of the above configuration will be described. Immediately after the commercial power supply 3 is turned on, the triac drive circuit 8 turns off the triac 7, thereby limiting the inrush current generated in the input terminal + VIN1 line by the resistor 6. On the other hand, the voltage detection circuit 21 stops supplying the detection signal to the base of the transistor 22 until the DC input voltage Vi2 reaches a predetermined voltage level, and maintains the transistor 22 in an off state. At this time, the connection between the detection terminal ENA in the AC / DC module 1 and the output terminal -VOUT1 is in a non-conductive state, and the connection between the control terminal CNT and the input terminal -VIN2 of the DC / DC module 2 is opened. The pulse is forcibly stopped by the ON / OFF control circuit 19, and the supply of the DC output voltage Vo is stopped. That is, in this state, the DC / DC module 2 itself has not been activated, and the flow of excessive current from the AC / DC module 1 is prevented. Also, due to some abnormality,
Even when the voltage level of the AC input voltage Vi1 decreases,
The voltage detection circuit 21 detects the drop of the DC input voltage Vi2, immediately turns off the transistor 22, and sets the DC / DC
The operation of the module 2 is forcibly stopped.

On the other hand, when the AC input voltage Vi1 rises and exceeds a predetermined voltage level after the commercial power supply 3 is turned on, the triac 7 is turned on by a drive signal from the triac starter circuit 8, and the triac 7 is turned on from the input terminal + VIN1. Input current flows through the rectifier circuit 4 through the triac 7. When the DC input voltage Vi2 reaches a predetermined voltage level, the voltage detection circuit 21 supplies a detection signal to the base of the transistor 22 to turn on the transistor 22. At this time, a conduction state is established between the detection terminal ENA in the AC / DC module 1 and the output terminal-VOUT1, and DC
/ DC module 2 control terminal CNT and input terminal -VIN
The control circuit 18 uses a phototransistor
The pulse conduction width of the drive signal supplied to the FET 12 is controlled on the basis of the output signal of the DC / DC converter 17.
A current flows into the DC module 2 and a predetermined DC output voltage Vo is supplied to the load 14.

As described above, according to the above embodiment, AC /
The voltage detection circuit 21 of the DC module 1 detects the DC input voltage V
Until i2 reaches a predetermined level, the DC / DC module 2 controls the DC / DC control via the control terminal CNT via the detection terminal ENA so that the DC output voltage Vo is not supplied.
Controls module 2. Thereby, the DC output voltage V
DC / DC module 2 for externally controlling the supply of i2
Of the DC input voltage Vi by effectively utilizing the control terminal CNT of
2 can prevent an excessive current from flowing into the input side of the DC / DC module 2 in a low state.

When the DC input voltage Vi2 is low, the voltage detection circuit 21 of the AC / DC module 1
Control terminal CNT and input terminal of DC / DC module 2-
Since the VIN2 is opened and the operation of the DC / DC module 2 is forcibly stopped, an excessive input current is prevented from flowing into the DC / DC module 2 when the commercial power supply 3 is turned on. In addition, it is possible to prevent elements such as a breaker and a fuse for overcurrent protection from being damaged by an excessive current. At the same time, the occurrence of excessive current on the input side of the AC / DC module 1 is also suppressed, and it is possible to prevent the resistor 6 constituting the inrush current prevention circuit 9 from generating heat.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, in the embodiment, the DC output voltage Vo is supplied when the control terminal CNT and the input terminal -VIN2 are short-circuited. However, when the control terminal CNT is opened, the DC output voltage Vo is reduced. The voltage may be supplied, and the configurations of the voltage detection circuit 21 and the transistor 22 may be changed as appropriate. Further, a configuration may be employed in which the AC / DC module 1 is miniaturized by externally attaching the smoothing capacitor 5. Further, the detection terminal ENA may be used as a terminal for detecting an abnormality of the AC input voltage Vin1.

[0016]

According to the present invention, there is provided an AC / DC module for converting an AC input voltage into a DC input voltage, and a D which is connected to the AC / DC module and supplies a stable DC output voltage.
A switching power supply device having a control terminal for externally controlling the supply of the DC output voltage, wherein the AC / DC module controls the supply of the input voltage. A detection terminal connected to an output side of the voltage detection circuit, wherein the voltage detection circuit is connected to the DC / DC converter via the detection terminal until the input voltage reaches a predetermined level. The control terminal of the DC module is configured to stop the supply of the DC output voltage. The control terminal of the DC / DC module is effectively used, and the input of the DC / DC module is performed when the DC input voltage is low. It is possible to provide a switching power supply device capable of preventing an excessive current from flowing to the side.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a switching power supply device showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of a switching power supply device showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC / DC module 2 DC / DC module 3 Commercial power supply 21 Voltage detection circuit CNT control terminal ENA detection terminal

Claims (1)

(57) [Scope of request for utility model registration] 1. An AC / DC module for converting an AC input voltage into a DC input voltage, and a DC / DC module connected to the AC / DC module for supplying a stable DC output voltage are provided separately. Said D
The C / DC module supplies the DC output voltage
The AC / DC module detects the input voltage in a switching power supply device having a control terminal for controlling the input voltage.
Voltage detection circuit connected to the output side of this voltage detection circuit
The voltage detection circuit is connected to the input terminal.
Until the force voltage reaches a predetermined level, through the detection terminal
The DC terminal is controlled by the control terminal of the DC / DC module.
A switching power supply device configured to stop supply of a force voltage .