The utility model content
The purpose of this utility model is to provide a kind of switching power circuit, is intended to solve existing switching power circuit burns out components and parts easily when voltage instability problem.
The utility model is achieved in that a kind of switching power circuit, comprises current rectifying and wave filtering circuit, and alternating voltage is carried out exporting the electric energy power supply behind the rectifying and wave-filtering; Also comprise:
Voltage detecting circuit, whether the alternating voltage that detects input is higher than set point;
Drive circuit is connected with described voltage detecting circuit, when the alternating voltage of input is higher than set point, and output drive signal;
Relay, its input is connected to the output of described drive circuit, works under the driving of described drive signal; Its output is connected to the input of described current rectifying and wave filtering circuit by load.
Another purpose of the present utility model is to provide a kind of television set that adopts above-mentioned switching power circuit.
In the switching power circuit that the utility model embodiment provides, when detecting overtension, by relay with alternating voltage by the load dividing potential drop, make that the voltage in the input rectifying filter circuit is no more than set point, the components and parts in the protective circuit are not burnt out.
Embodiment
In order to make the purpose of this utility model, technical scheme and advantage clearer,, the utility model is further elaborated below in conjunction with drawings and Examples.Should be appreciated that specific embodiment described herein only in order to explanation the utility model, and be not used in qualification the utility model.
In the switching power circuit that the utility model embodiment provides, when detecting overtension, by relay with alternating voltage by the load dividing potential drop, make that the voltage in the input rectifying filter circuit is no more than set point, the components and parts in the protective circuit are not burnt out.
The switching power circuit that the utility model embodiment provides is mainly used in the TV set power, and its circuit for convenience of explanation, only shows the part relevant with the utility model as shown in Figure 1, and details are as follows.
Switching power circuit comprises: the voltage detecting circuit 1 of Lian Jieing, drive circuit 2, relay 3, load 4 and current rectifying and wave filtering circuit 5 successively, wherein, whether the alternating voltage that voltage detecting circuit 1 detects input is higher than set point, if not, then alternating voltage directly inputs to current rectifying and wave filtering circuit 5 by the normally-closed contact a of relay 3, output electric energy power supply after current rectifying and wave filtering circuit 5 rectifying and wave-filterings are handled; If; drive circuit 2 output drive signals then; the normally-closed contact a of relay 3 disconnects; normally opened contact b conducting, alternating voltage inputs to current rectifying and wave filtering circuit 5 by load 4 again through behind the normally opened contact b of relay 3, like this; when alternating voltage is too high; by load 4 dividing potential drops, make that the voltage in the input rectifying filter circuit 5 is no more than set point, the components and parts in the protection subsequent conditioning circuit are not burnt out.As an embodiment of the present utility model, the ordinary incandescent lamp bubble is adopted in load 4, can reduce cost, and then can calculate according to the power of television set as for the bulb of selecting much power.
In the utility model embodiment, drive circuit 2 comprises: the first divider resistance R1, the second divider resistance R2, current-limiting resistance R3 and transistor Q; Wherein, the first divider resistance R1 and the second divider resistance R2 are connected in series, and current-limiting resistance R3 is connected to the end A that is connected in series of the first divider resistance R1 and the second divider resistance R2, and the non-end B that is connected in series of the first divider resistance R1 is connected with voltage detecting circuit 1; The non-end C ground connection that is connected in series of the second divider resistance R2; The base stage of transistor Q is connected with current-limiting resistance R3, grounded emitter, and collector electrode is connected to the input of relay 3.
As an embodiment of the present utility model, drive circuit 2 also comprises: voltage stabilizing circuit 21, and its first end is connected with voltage detecting circuit 1; Its second end ground connection, its 3rd end is connected with relay 3; Being used to export stable voltage provides power supply for relay 3.
As an embodiment of the present utility model, drive circuit 2 also comprises: rectification filtering module 22, be connected to the non-of first divider resistance and be connected in series between end B and the voltage detecting circuit 1, the alternating voltage that voltage detecting circuit 1 is exported carries out exporting behind the rectifying and wave-filtering.And rectification filtering module 22 further comprises: diode D0 that is connected in series and capacitor C 0, the non-end that is connected in series of diode D0 is connected with voltage detecting circuit 1, the non-end ground connection that is connected in series of capacitor C 0, the end that is connected in series of diode D0 and capacitor C 0 are connected to the non-end B that is connected in series of first divider resistance.
As an embodiment of the present utility model, drive circuit 2 also comprises: sustained diode 3, be connected between the 3rd end of the emitter of transistor Q and voltage stabilizing circuit 21, and guarantee current paths.
The operation principle of the switching power circuit that the utility model embodiment provides now is described in detail in detail in conjunction with Fig. 1: voltage detecting circuit 1 detects the alternating voltage of input, when the alternating voltage of input is lower than 220V, the normally-closed contact a conducting of relay 3, the direct input that input voltage is connected to current rectifying and wave filtering circuit 5; When the alternating voltage of input is higher than 220V, drive circuit 2 is started working, behind alternating voltage process rectification filtering module 22 filter rectifications of input, carry out dividing potential drop by the first divider resistance R1 and the second divider resistance R2, make the voltage of holding A to order that is connected in series of win the divider resistance R1 and the second divider resistance R2 be higher than the base stage of transistor Q and the voltage difference between the emitter, at this moment, transistor Q conducting, drive the normally opened contact b conducting of relay 3, the alternating voltage of input carries out dividing potential drop by a load 4 behind the normally opened contact b of relay 3, input to the input of current rectifying and wave filtering circuit 5 then.Can not surpass 220V through overload 4 voltage after partial, can guarantee that like this components and parts that input in current rectifying and wave filtering circuit 5 and the subsequent conditioning circuit are not burnt out.
In the switching power circuit that the utility model embodiment provides, when detecting overtension, by relay with alternating voltage by the load dividing potential drop, make that the voltage in the input rectifying filter circuit is no more than set point, the components and parts in the protective circuit are not burnt out.
The above only is preferred embodiment of the present utility model; not in order to restriction the utility model; all any modifications of within spirit of the present utility model and principle, being done, be equal to and replace and improvement etc., all should be included within the protection range of the present utility model.