JPH07106059B2 - Power supply - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power supply device that drives a plurality of circuit blocks by a single power supply path.

[Prior Art] As a power supply device incorporating a general switching power supply unit, there is a device as shown in FIG.

Frequency by an inverter composed of switching power supply unit by the rectifying unit D ₁ and the control circuit input DC voltage rectified and smoothed by the capacitor C ₂ to switching drive the high-frequency transformer Tr ₁ and the transistor Q _1, the transistor Q ₁ (not shown) The voltage is converted into a voltage, and the DC voltage is restored again by a DC smoothing circuit composed of a rectifier D ₂ , a choke coil L ₁ and a capacitor C ₃ connected to the output winding N ₂ of the high frequency transformer Tr ₁ .

The rectifier D ₁ is intended to receive electric power from a commercial power supply via the series circuit of the temperature fuse TF embedded resistor R ₁ constituting the current fuse F and the inrush current suppression circuit, resistor R ₁
Is triac T ₁ is connected in parallel to the gate signal of the TRIAC T ₁ using the voltage of the feedback winding N ₃ of the high-frequency transformer Tr ₁ to. A resistor R ₂ and a capacitor C ₁ connected in parallel with the feedback winding N ₃ form a filter for stabilizing the gate signal.

Here, when the power is turned on, the input current to the switching power supply unit passes through the path I ₁ , and the inrush current to the capacitor C _{2 is changed} to the resistor.
It is suppressed by R ₁ . The switching power source unit when coming up the potential across the capacitor C ₂ starts to operate, the primary winding N ₁ in accordance with the switching of the transistor Q ₁
A current flows through the output winding and a voltage is also generated in the output winding N ₃ . Due to this voltage, the triac T ₁ becomes conductive, and the path of the input current of the switching power supply unit shifts to I ₂ . This allows
The resistor R ₁ has a loss only at start-up, and has no loss during normal operation.

The branched separate circuit S ₁ is supplied with power from the connection point of the current fuse F and the resistor R ₁ .

[Problems to be Solved by the Invention] By the way, in this conventional power supply device, when a short circuit occurs between D and S due to a failure of the transistor Q _{1 or} the like, the high frequency transformer Tr ₁ stops oscillating and the feedback winding N ₃ No voltage is generated. Therefore, the triac T ₁ becomes non-conductive and the resistor
Large current flows through R ₁ . Therefore, the loss of the resistor R ₁ increases and the temperature rises. When this temperature exceeds a certain value, the temperature fuse TF built in the resistor R ₁ is blown and the power supply to the switching power supply unit is cut off. Since the fusing current IF of the current fuse F has a relation of IF> (V _AC / R ₁ ), it does not blow in the above failure mode. V _AC is the commercial power supply voltage.

In this case, although the function of the switching power supply unit is stopped, the branched separate circuit S ₁ maintains the normal state, so that it is difficult for the entire device to recognize the failure, or there is a risk of a secondary failure.

The present invention has been made in view of the above points, and an object thereof is to provide a power supply device that shuts off all the power supplies in the device when the switching power supply unit is abnormal.

[Means for Solving the Problems] In order to achieve the above object, the present invention uses an input power supply path branched into a plurality of systems, and uses a triac and an inrush current suppressing resistor in one of the branch paths. In a power supply device having a switching power supply unit that is supplied with power via a parallel circuit with a rush current suppressing circuit, a temperature detecting element that is thermally coupled to the rush current suppressing resistor and is in an open state when the temperature exceeds a certain temperature. Is inserted in the input power supply path before the branch point.

[Operation] In the present invention, when the inrush current suppressing resistor is overheated when the switch power supply unit is abnormal, the temperature detecting element thermally coupled to the inrush current suppressing resistor is opened to stop all power supply. You can do it.

[Examples] The present invention will be described below with reference to Examples.

FIG. 1 shows an embodiment circuit of the present invention. In this embodiment, only a rush current suppressing resistor R ₁ is connected in parallel to a triac T ₁ , and the rush current suppressing resistor R ₁ is thermally coupled. The temperature fuse TF, which is the temperature detecting element, is inserted and connected between the current fuse F and the branch point. The other configurations are the same as those of the conventional example, and the description thereof will be omitted.

Next, the operation of the embodiment circuit transistor Q ₁ is between becomes failure D-S is explained when a short circuit state.

Now when the short circuit occurs as described above, the high frequency transformer Tr ₁
Oscillation stops and no voltage is generated in the feedback winding N ₃ .
Therefore, the triac T ₁ becomes non-conductive, and a large current flows through the inrush current suppressing resistor R ₁ . For this reason, the loss of the inrush current suppressing resistor R ₁ increases and the temperature rises. When this temperature exceeds a certain level, the temperature fuse TF is blown and the power supply to all circuits is stopped.

EFFECTS OF THE INVENTION The present invention has an input power supply path branched into a plurality of systems as described above, and one of the branch paths is provided with a triac and a rush current suppressing circuit using a rush current suppressing resistor in parallel. In a power supply device having a switching power supply unit that receives power supply via a circuit, a temperature detection element that is thermally coupled to the inrush current suppressing resistor and is in an open state at a certain temperature or higher is input before the branch point. Since it is inserted in the power supply path, it is possible to cut off the power supply to all circuits in the same device when an abnormality occurs in the switching power supply, so it is easy to recognize the failure and the possibility of a secondary failure. There is an effect that can be cut off.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional example. V _AC is a commercial power supply voltage, T ₁ is a triac, R ₁ is a resistor for suppressing inrush current, Q ₁ is a transistor, Tr ₁ is a high frequency transformer, S ₁ is another circuit, and TF is a thermal fuse.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Norihi Shiraiwa 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (56) References: 1-86476 (JP, U) 1-162782 (JP, U)

Claims (1)

[Claims] 1. An input power supply path branches into a plurality of systems,
In a power supply device having a switching power supply unit that receives power supply through a parallel circuit of a triac in one of its branch paths and an inrush current suppression circuit using a resistor for inrush current suppression, the inrush current suppression resistor A power supply device, characterized in that a temperature detection element that is thermally coupled to the container and is in an open state when the temperature exceeds a certain temperature is inserted in an input power supply path before the branch point.