JPH028553Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a chiyoke input type output circuit that has an operation display function as a power supply.
This invention relates to an output circuit for a switching regulator that uses a chiyoke coil having two windings with different numbers of windings and is devised so that a dummy resistor also functions as a current limiting resistor for a light emitting element for displaying operation.

One type of output smoothing circuit in a switching regulator is a chiyoke input type rectifying and smoothing circuit that uses a chiyoke coil and a capacitor as a filter. In the conventional circuit of this type, as shown in Fig. 1, the transformer output of the switching regulator body is rectified by a rectifier circuit 1 consisting of rectifier diodes D1 and D2, and the rectified output is connected to a chiyoke coil L and a capacitor C. A configuration is adopted in which the output is smoothed by a filter consisting of the following, and the output is supplied to the load side. In this case, a dummy resistor R1 is connected in parallel to the capacitor C. The resistance value of this dummy resistor R1 is set to a value such that its power consumption is approximately 5% or more of the output power. The value of 5% here is when the chiyoke coil L has an ideal inductance, and since the inductance is actually a little low, the dummy resistor R1 should have a resistance value that will consume 5% or more of the output power. Must be set to . This dummy resistor R1
This is to prevent the current flowing through the choke coil L from falling below a certain level regardless of the state of the load. If dummy resistance R
1 is missing, or its resistance value is extremely large, and the output is opened, the output current will be zero, and the pulsating current flowing through the chain coil L will cut to zero ampere and become discontinuous, resulting in a very large output ripple. I get used to it. As a result, the switching transistor in the main body of the switching regulator causes intermittent oscillation, resulting in serious drawbacks such as generation of abnormal noise and a significant decrease in reliability. Conversely, if the resistance value of dummy resistor R1 is decreased, the dummy current increases, so the pulsating current flowing through the chiyoke coil L will always be above a certain level, which solves the problem of discontinuous current, but the power loss of dummy resistor R1 increases. becomes extremely large, and especially when designing a power supply device with a large output power, the thermal design of this dummy resistor R1 becomes extremely large-scale.

Furthermore, when it is desired to display the operation of the power supply using a light emitting element such as a light emitting diode, a conventional configuration has been adopted in which a resistor R2 and a light emitting diode D are connected in series, as shown in FIG. In this case, the resistor R2 functions to limit the current of the light emitting diode D, and is the dummy resistor R2 described above.
They are considered to be different from 1 because their resistance values are completely different. In other words, the dummy resistor R1 is defined by the chiyoke coil L, whereas the dummy resistor R1 is
This is because the current limiting resistor R2 is defined by the light emitting diode D. According to the conventional technology, in a power output circuit of the input type having an operation display function, a dummy resistor with low resistance and large power loss and a current limiting resistor for limiting the current of the light emitting diode are separately installed. It was necessary to establish one.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the conventional technology, eliminate any inconveniences such as intermittent oscillation of the switching regulator, and significantly reduce the power loss of the dummy resistor. It has an operation display function that does not cause any heat dissipation problem, and allows the dummy resistor to also serve as a current limiting resistor for the light emitting element for operation display, so that the device can be significantly miniaturized. The purpose of the present invention is to provide a power output circuit.

The present invention, which can achieve such objectives, has devised the chiyoke coil used, and in addition to the main winding used conventionally, an auxiliary winding is provided that is connected to a dummy resistor. The number of turns of the winding is
The number of turns is much larger than that of the main winding, thereby making it possible to minimize the dummy power supply, and a light-emitting element for operation indication is connected in series with the dummy resistor, and the auxiliary winding and the dummy resistor are connected to each other. The light emitting element is configured to be driven by a small amount of dummy power source.

Hereinafter, the present invention will be explained in more detail based on the drawings. FIG. 2 is a circuit diagram showing an embodiment of the present invention. This circuit consists of a rectifier diode D connected to the transformer of the switching regulator body.
This is a chiyoke input type output circuit comprising a rectifying circuit 1 made up of components 1 and D2, and a smoothing circuit made up of a chiyoke coil L and a capacitor C connected thereto. Here, the points that are significantly different from the prior art are firstly the structure of the chiyoke coil L and secondly the location where the light emitting element for displaying the operation is connected. The choke coil L has a structure including a main winding n1 that supplies an output to the load side via a capacitor C, and an auxiliary winding n2 whose number of turns is much greater than the number of turns of the main winding n1. The main winding n1 may be a general main winding for supplying current to the load side, and is a thick winding similar to the conventional one. On the other hand, the auxiliary winding N2 only needs to have a current capacity that allows the dummy current to flow, so it may be a thin wire, and as described above, it is wound more than the number of turns of the main winding n1. To give an example of the number of turns, the main winding n1 has about 10 turns, while the auxiliary winding n2 has about 100 turns. The auxiliary winding n2, the dummy resistor R, and a light emitting element for displaying operation, such as a light emitting diode D, are connected in series, and the series circuit is connected in parallel to the load. In this embodiment, the winding starts of the main winding n1 and the auxiliary winding n2 are commonly connected and connected to one end of the rectifier circuit 1, and the other end of the auxiliary winding n2 is connected to the light emitting diode D via a dummy resistor R. The cathode end of the light emitting diode D is connected to the anode end of the rectifier circuit 1.
This configuration is connected to the other end of the

For example, if we consider designing a 50W (5V, 10A) power supply, a conventional circuit configuration would require a dummy resistor with a power consumption of 2.5W (0.5A); The number of turns of the chiyoke coil is
However, if this circuit is used (the number of turns of the main winding n1 is 10 turns, and the number of turns of the auxiliary winding n2 is
100 turns), the dummy resistor R should be 0.25W (0.05A). In short, the power loss of the dummy resistor R can be reduced to 1/10 of that of the prior art. In addition, the current value of 0.05A in this case is a value suitable for the current that drives the light emitting diode D, so as mentioned above, by inserting the light emitting diode D in series with the dummy resistor R, the dummy resistor R also functions as a current limiting resistor for the light emitting diode D. This greatly simplifies the heat dissipation design of the dummy resistor R, and makes it possible to obtain a large margin for preventing intermittent oscillation of the switching transistor just by slightly increasing the power consumption of the dummy resistor. This means that the number of resistors that conventionally required two resistors can be reduced to one, which brings about an extremely convenient result. In other words, in the circuit configuration of the present invention, the problem is the product of the number of turns of the chiyoke coil and the current flowing through it.Therefore, in the present invention, the dummy current is reduced by increasing the number of turns, and the loss in the dummy resistor is reduced. In addition, the loss of the dummy resistor is further reduced by incorporating a light emitting element for operation display in series. In fact, prototype experiments have confirmed that a small dummy power supply is effective. Normally, for a power supply with an output voltage of about 5V, the efficiency is at best
It is said that the efficiency is 72-75%, but by applying the present invention, it is possible to improve the efficiency to nearly 80%.

It should be noted that although the above embodiment has a half-wave rectification type output smoothing circuit, it goes without saying that the present invention can also be applied to a full-wave rectification type output smoothing circuit as shown in FIG. stomach. Since the basic idea is the same as that of the previous embodiment, corresponding parts are given the same reference numerals and description thereof will be omitted.

Since the present invention is a power output circuit with an operation display function configured as described above, the power loss of the dummy resistor can be significantly reduced, and the heat dissipation device can also be simplified, making it possible to significantly downsize the device. In addition, by slightly increasing the power loss in the dummy resistor, a large margin can be taken to prevent the switching transistor from causing intermittent oscillation, which greatly improves the reliability of the switching regulator. can be improved to
There is no need to add a special current-limiting resistor to drive the light-emitting element for operation display, and the circuit is extremely simple, making it possible to manufacture high-quality switching regulators with high efficiency, and has extremely practical effects. It's large.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the prior art, FIG. 2 is a circuit diagram showing one embodiment of the present invention, and FIG. 3 is a circuit diagram showing still another embodiment of the present invention. 1... Rectifier circuit, L... Chi York coil, C...
...Capacitor, R1, R2...Dummy resistor, D...
...Light emitting diode, n1...Main winding, n2...Auxiliary winding.

Claims (1)

[Scope of utility model registration request] In the power output circuit, the power output circuit includes a rectifying circuit, a smoothing circuit made up of a chiyork coil and a capacitor connected to the rectification circuit, and a light emitting element for displaying operation connected in parallel with a load. The main winding supplies an output to the load side, and the auxiliary winding has a number of turns greater than the number of turns of the main winding, and the series circuit includes the auxiliary winding, a dummy resistor, and a light emitting element for indicating operation. 1. A power output circuit having an operation display function, characterized in that: is connected in parallel with a load.