JPH0118662B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device that can supply power to a load for a certain period of time when power input is cut off, and particularly aims to utilize stored power without waste.

Some conventional power supply devices have a structure in which a certain amount of energy is stored in a built-in capacitor during steady operation, and when the power input is cut off, the energy from the capacitor is supplied to the load for a certain period of time from this point onwards. . For example, an amplifier that mutates the circuit when the power input is cut off, a tape recorder that drives a motor or plunger to energize a mechanism to a predetermined position, a security device that notifies an abnormality, and programs and data that are being processed. This type of power supply device is used in a variety of devices, such as a computer, which has the function of saving data into memory and switching to a device that backs up the memory.

However, many of these power supply devices have circuit configurations in which when the energy stored in the capacitor is discharged, it is consumed by resistance components other than the load and is wasted as heat. The drawback was that the capacitance of the above-mentioned capacitor had to be increased to compensate.

The present invention aims to efficiently utilize the energy stored in a capacitor, and is characterized by providing a transistor that bypasses a resistive component inserted in series with a load.
An embodiment of the present invention will be described below based on the drawings.

The drawing shows a power supply for a device with one load that is to be powered by an internal capacitor when the power input is interrupted. 1 is a transformer whose power input is AC, 2 is a bridge rectifier circuit consisting of four diodes, and 3 is a smoothing capacitor. A voltage E ₁ containing ripples is supplied to both ends of this smoothing capacitor 3 . This voltage E ₁ is the first voltage that does not need to be supplied with power when the power input is cut off.
is the predetermined voltage applied to the load 4.

The anode of a first diode 5 is connected to the positive voltage terminal of the smoothing capacitor 3, and a capacitor 6 is connected between the cathode of this diode 5 and the ground.
is connected. Letting the anode of the diode 5 be a point and the cathode be a point B, the potential of the b point will be V _F from the point a due to the forward voltage drop of the diode 5.
A voltage of E ₁ −V _F is supplied to the capacitor 6. One end of the resistor 7 and the emitter of the PNP transistor 8 are connected to point b.
The other end of the resistor 7 and the collector of the transistor 8 are connected to the collector of a transistor 9 for constant voltage control. 10 is a Zener diode connected to the base of transistor 9; 11 is a capacitor for improving the ripple rate of the output voltage from transistor 9; 12 is a Zener diode 10 connected between the base of transistor 9 and the point b. This is a resistor that supplies the Zener current of and the base current of transistor 9. A second load 13 is supplied with the output voltage E ₂ of the transistor 9, and to which the energy of the capacitor 6 is supplied when the power input is cut off, as will be described later.

Here, the resistor 7 is not particularly necessary to obtain the voltage E ₂ of the second load, but without this resistor 7, a transistor 9 with a large power dissipation would be required, and a heat sink would also be necessary. It will be very large. Therefore, normally the unnecessary part is resistor 7
This configuration reduces the load on the transistor 9. However, the power consumed by this resistor 7 is essentially wasteful, and especially when the power of the capacitor 6 is supplied to the load 13 when the power input is cut off as described later, the power consumed by this resistor 7 is directly This will reduce the efficiency of using power from the capacitor 6. Therefore, in the present application, the emitter and collector of the transistor 8 are connected to each terminal of the resistor 7. Between the base of the transistor 8 and point a (anode of the diode 5),
A resistor 14 and a second diode 15 in a forward direction from its base toward point a are connected in series.

In the above configuration, the steady operation will be explained first. When the power input is normally applied, the output of the bridge rectifier circuit 2 is smoothed by the smoothing capacitor 3 (voltage E ₁ ), and is supplied to point b (voltage E ₁ −V _F ) via the diode 5. . Furthermore, this output is made into a constant voltage by a transistor 9 via a resistor 7 from point b, and is supplied to a load 13 as an output of voltage _E1 .

At this time, the potential difference between point a and point b is V _F
Therefore, the transistor 8 is in a cut-off state, and all the power supplied to point b is consumed between the resistor 7 and the load 13. Note that the voltage E ₁ is directly supplied to the load 4 from point a. Further, a predetermined charge is stored in the capacitor 6.

Next, a case where power input is cut off will be explained. This state occurs due to a power outage on the AC power supply side or when the AC input to the transformer 1 of this embodiment is cut off by a safety device (not shown) in the event of an accident in another device. When this power supply input is cut off, when the potential at point a decreases and the potential difference between points b and a exceeds V _F +V _BE (V _BE is the base-emitter voltage of transistor 8), transistor 8 conducts and the voltage is stored in capacitor 6. The energy that has been used is supplied to the transistor 9 and the load 13 via the transistor 8.
In other words, almost no current flows through the resistor 7, and wasteful consumption of power can be prevented.

Note that the first diode 5 prevents the energy of the capacitor 6 from being supplied to the load 4 when the power supply input is cut off, and the load 4 is immediately turned off.

The second diode 15 also prevents the transistor 8 from malfunctioning due to ripples in the output voltage at point a during normal operation.If this diode 15 is a Zener diode, fluctuations in the load 4 can be prevented. It can operate accurately even in extremely large cases.

According to the above configuration, the energy stored in the capacitor 6 can be supplied to the load 13 without wasting it in the resistor 7, and the energy utilization efficiency will not be reduced, especially under extremely severe conditions such as after the power input is cut off. It has a very big effect. Since energy is used efficiently in this way, a capacitor with a small capacitance can be used to obtain the necessary energy, which allows the device to be made smaller by taking up less space and can be configured at a lower cost. is possible.

As is clear from the above embodiments, according to the present invention, by providing a transistor that bypasses the resistive component inserted in series with the load when the power supply input is cut off, the energy stored in the capacitor is transferred to the resistor. It is possible to provide an excellent power supply device that does not waste energy by components, that is, increases the efficiency of energy use, and also reduces the capacitance of the capacitor, contributing to lower costs and miniaturization of equipment. It is something.

[Brief explanation of drawings]

The drawing is a circuit configuration diagram showing an embodiment of the power supply device of the present invention. 2... Bridge rectifier circuit, 3... Smoothing capacitor, 5... First diode, 6... Capacitor, 7... Resistor, 8... Transistor, 13...
Second load, 14...resistor, 15...second diode.

Claims (1)

[Claims] 1. A first diode connected in the forward direction to the output of the rectifying and smoothing circuit, a capacitor connected between the cathode of the first diode and the ground,
a first resistor having one end connected to the cathode and generating a voltage to the load at the other end; and an emitter connected to the first resistor.
a PNP transistor connected to the cathode of the diode and having its collector connected to the load side of the first resistor; and a PNP transistor connected between the PNP transistor and the anode of the first diode in the forward direction from the base. 1. A power supply device comprising a series circuit of a second diode and a second resistor.