CN2798158Y

CN2798158Y - Switch electric source apparatus

Info

Publication number: CN2798158Y
Application number: CN 200520200121
Authority: CN
Inventors: 欧振忠
Original assignee: 欧坚
Priority date: 2005-03-02
Filing date: 2005-03-02
Publication date: 2006-07-19
Anticipated expiration: 2015-03-02

Abstract

The utility model relates to a switch power supply apparatus belonging to the technical field of power supply transfer. The pulse transformer is provided with a feedback coil; an integrated circuit of a pulse width controller is provided with an internal oscillator control lead terminal; in addition, the utility model is provided with a zero crossing detection switch circuit which is controlled by the output end potential of the integrated circuit of a pulse width controller and the potential of the feedback coil. When the output end of the integrated circuit of a pulse width controller and resonance signals from the feedback coil have low level, the zero crossing detection switch circuit outputs high level signals to the internal oscillator control lead terminal of the integrated circuit of a pulse width controller by a power supply so that a switch tube is switched on. A quasi-resonance single-end counter activating switch power supply connected by the switch power supply apparatus not only has the characteristics of big power, strong protective capability, high efficiency and small electromagnetic interference, but also has the advantage of low cost.

Description

Switching power unit

Technical field

The utility model relates to the switch power technology field, especially a kind of single-end flyback switching power supply.

Background technology

Existing single-ended reaction type Switching Power Supply is to reach purpose to load output burning voltage by the break-make mode that control is connected on the on-off element in the pulse transformer primary coil in the Switching Power Supply.Switching Power Supply has multiple mode of operation according to the difference of gauge tap element break-make mode; a kind of Switching Power Supply that is operated in the pulse width modulated duty pattern is arranged; the pulse signal of its gauge tap element is that pulsed frequency is certain; the mode of operation that pulse width is adjustable; it is PRC (Pulse Ratio Control) pattern; people have produced a class specially and have adopted this mode of operation to be used for the special IC of gauge tap element; as be provided with internal reference voltage leading-out ends pin (VREF) and internal oscillator external timing resistance; the UC1842 type series integrated circuit of electric capacity exit pin (RC); UC2842 type series integrated circuit; UC3842 type series integrated circuit and UCC3800 series integrated circuit etc.; the big advantage made from this adhesive integrated circuit of single-end flyback switching power supply one is cheap; function admirable, but also have its output power little; efficient is low; the not strong and big shortcoming of electromagnetic interference (EMI) of protective capability.The Switching Power Supply of another kind of mode of operation, phase sixth version in " electronics newspaper " 28 days the 39th September in 2003 " S of a Konka series colour television set switching power supply circuit theory " civilian QRC pattern of introducing as the publication of electronics newspaper office, the signal of its gauge tap element is a modulating frequency and width, and turn-off at on-off element, pulse transformer is after load has discharged electric energy, quasi-resonance mode of operation in the conducting of pulse transformer primary coil resonance potential minimum point, this article is referred to as the quasi-resonance mode of operation, be used to make the integrated circuit of this mode of operation Switching Power Supply common the STRF6658 type arranged, STRG8656 type Switching Power Supply thick film integrated circuit and TEA1507 type, TDA4605 type switch power controller integrated circuit etc., its output power of single-end flyback switching power supply that is connected into this integrated circuit is big, the efficient height, electromagnetic interference (EMI) is little, but integrated circuit price height.There is not at present above-mentioned the former the cheap integrated circuit of employing to make Switching Power Supply as yet with above-mentioned latter's mode of operation and advantage thereof.

Summary of the invention

The utility model provides a kind of switching power unit, and the problem that it mainly solves is to adopt function admirable, the cheap existing integrated circuit that is used for the pulse width adjustable operational modes to make modulating frequency and width quasi-resonance mode of operation and the strong single-end flyback switching power supply device of protective capability.

For achieving the above object, the technical solution adopted in the utility model is: the pulse transformer of this switching power unit is provided with tickler, its pulse width controller integrated circuit is provided with internal oscillator control exit, in addition, it is provided with a zero passage detection on-off circuit, this zero passage detection on-off circuit is controlled by the output terminal current potential of described pulse width controller integrated circuit and the current potential of described tickler, when the resonance signal of described pulse width controller ic output and described tickler feedback is low level, just by the internal oscillator control exit output high level signal of power supply to described pulse width controller integrated circuit, then this pulse width controller integrated circuit output control end output high level makes the switching tube conducting to this zero passage detection on-off circuit.

Above-mentioned zero passage detection on-off circuit can be connected into by switch triode and resistance, diode, on this zero passage detection on-off circuit output terminal, can be connected to isolating diode, in this zero passage detection on-off circuit and branch road that described tickler is connected, be connected to commutation diode.In addition; to the branch road of zero passage detection on-off circuit, also can be connected to an overcurrent protection switch circuit at above-mentioned power supply; the input end of this overcurrent protection switch circuit is connected on the internal reference voltage leading-out ends of the positive pole in self feeding source and described pulse width controller integrated circuit; when the potential difference (PD) of this input end is lower than setting value; be potential difference (PD) between the internal reference voltage leading-out ends of the positive pole in described self feeding source and described pulse width controller integrated circuit when being lower than setting value, the power supply of the described zero passage detection on-off circuit of this overcurrent protection switch circuitry cuts.

In the such scheme; between the over-current detection input end of the positive pole of input rectifying filtering circuit and described pulse width controller integrated circuit, also can be connected to a low-voltage protective switch circuit; the input end of this on-off circuit is connected between the internal reference voltage leading-out ends of anodal and described pulse width controller integrated circuit of described input rectifying filtering circuit; when the potential difference (PD) between the internal reference voltage leading-out ends of the positive pole of described input rectifying filtering circuit and described pulse width controller integrated circuit is higher than setting value; this on-off circuit is just open-minded, to the over-current detection end input high level signal of described pulse width controller integrated circuit.

Owing to adopted such scheme, the utility model and prior art are in than having following beneficial effect:

It can utilize existing pulse width controller integrated circuit; as UC1842/3/4/5; UC2842/3/4/5; UC3842/3/4/5; the pulse width controller integrated circuit of UC3800/1/2/3/4/5 model; add that on the basis of original switching power unit circuit zero cross detection circuit promptly can be made into the switching power unit of modulating frequency and width quasi-resonance (QRC) mode of operation; the single-end flyback switching power supply made from this switching power unit not only has the characteristics that output power is big, protective capability is strong, efficient is high, electromagnetic interference (EMI) is little, but also has advantage of low manufacturing cost.

Description of drawings

Fig. 1 is the circuit theory diagrams of the utility model embodiment one.

Embodiment

The utility model is described in further detail below in conjunction with the accompanying drawing example:

Embodiment shown in Figure 1 is the switching power unit that adopts UC3842 type pulse width modulator integrated circuit to be connected into, and it includes prior art parts such as on-off circuit on input rectifying filtering circuit, pulse width modulator, pulse transformer T and the primary coil N1 thereof, over-current detection circuit.Input rectifying filtering circuit wherein is connected into by fuse FU, rectifier Z, resistance R 1 and capacitor C 1; Pulse width modulator is connected into by UC3842 type pulse width controller integrated circuit (IC) and resistance R 2～R6, capacitor C 2～C5, the 4th pin of pulse width modulator integrated circuit (IC) is an internal oscillator control exit, and the 8th pin of pulse width modulator integrated circuit (IC) is the internal reference voltage leading-out ends; The on-off circuit that is connected on the primary coil N1 of pulse transformer T is made of switching tube Q1, resistance R 7, R8, R9 and capacitor C 8; Resistance R 8, R9, capacitor C 7 are over-current detection circuit; The tickler N2 of pulse transformer T, diode VD1, VD2 and capacitor C 6, C2 constitute the self feeding source, for providing working power after the pulse width modulator starting of oscillation, simultaneously also as the sampled signal for pulse width modulator feedback output voltage; The secondary coil N3 of pulse transformer T, diode VD3, capacitor C 9 output circuits provide power supply for load.

The utility model also is connected to zero passage detection on-off circuit, overcurrent protection switch circuit and low-voltage protective switch circuit on the basis of above-mentioned prior art part.

Zero passage detection on-off circuit wherein, it is frame of broken lines B portion, by diode VD4, VD5 and triode Q2, resistance R 12～R14 is connected into, wherein diode VD4 plays buffer action, diode VD5 plays rectified action, this zero passage detection on-off circuit is controlled by the 6th pin output terminal current potential of pulse width controller integrated circuit (IC) and the current potential of the resonance signal that tickler N2 is fed back, the resonance signal that is fed back as the 6th pin and the tickler N2 of pulse width controller integrated circuit (IC) is low level, when promptly being not enough to allow the Q2 conducting, the zero passage detection on-off circuit can be by 4th pin of power supply to the pulse width controller integrated circuit (IC), promptly to internal oscillator control exit output high level signal, then pulse width controller ic output the 6th pin is exported high level, make switching tube Q1 conducting, thereby realize the quasi-resonance mode of operation.

Overcurrent protection switch circuit wherein; it is frame of broken lines A portion; by triode Q2 and resistance R 11; R12 is connected into; this overcurrent protection switch circuit is connected on the branch road of self feeding source positive best zero passage detection on-off circuit; its input end is connected on the positive pole in self feeding source and the 8th pin of pulse width controller integrated circuit (IC); be on the internal reference voltage leading-out ends; when this Switching Power Supply is transshipped when serious; the voltage that the self feeding source provides can reduce; when it is low to moderate a certain setting value; be that the potential difference (PD) of the reference potential that provides of self feeding source the 8th pin anodal and the pulse width controller integrated circuit (IC) is when being lower than setting value; the power supply of the described zero passage detection on-off circuit of this overcurrent protection switch circuitry cuts; make its zero passage detection disabler; this Switching Power Supply is returned to the adjustable mode of operation of low frequency pulse width; be PRC (Pulse Ratio Control) pattern, output power descends.If do not need overload protection or be provided with the overload protection of other form, then this overcurrent protection switch circuit also can omit in other embodiments.

Low-voltage protective switch circuit wherein; it is connected between the 3rd pin of the positive pole of input rectifying filtering circuit output terminal and pulse width controller integrated circuit (IC) over-current detection input end; it is frame of broken lines C portion; by triode Q4; resistance R 15; R16 and capacitor C 10 are connected into; when the potential difference (PD) between the 8th pin of the positive pole of input rectifying filtering circuit and described pulse width controller integrated circuit (IC) is higher than setting value; this low-voltage protective switch circuit is just open-minded; improve pulse width controller integrated circuit (IC) the 3rd pin current potential, thereby the conducting electric current by pulse-width controlled ic output limit switch pipe Q1.If do not need low-voltage variation or be provided with the low-voltage variation of other form, then this low-voltage protective switch circuit also can omit in other embodiments.

Claims

1. switching power unit, its pulse transformer is provided with tickler, its pulse width controller integrated circuit is provided with internal oscillator control exit, it is characterized in that: it is provided with a zero passage detection on-off circuit, this zero passage detection on-off circuit is controlled by the output terminal current potential of described pulse width controller integrated circuit and the current potential of described tickler, when the resonance signal of described pulse width controller ic output and described tickler feedback was low level, this zero passage detection on-off circuit was just by the internal oscillator control exit output high level signal of power supply to described pulse width controller integrated circuit.

2. switching power unit according to claim 1 is characterized in that: described zero passage detection on-off circuit is connected into by switch triode and resistance, diode; On this zero passage detection on-off circuit output terminal, be connected to isolating diode, in this zero passage detection on-off circuit and branch road that described tickler is connected, be connected to commutation diode.

3. switching power unit according to claim 1 and 2; it is characterized in that: to the branch road of zero passage detection on-off circuit, be connected to an overcurrent protection switch circuit at described power supply; the input end of this overcurrent protection switch circuit is connected on the internal reference voltage leading-out ends of the positive pole in self feeding source and described pulse width controller integrated circuit; when the potential difference (PD) between the internal reference voltage leading-out ends of the positive pole in described self feeding source and described pulse width controller integrated circuit is lower than setting value, cut off the power supply of described zero passage detection on-off circuit.

4. switching power unit according to claim 1 and 2; it is characterized in that: it the positive pole of input rectifying filtering circuit and the over-current detection input end of described pulse width controller integrated circuit between be connected to a low-voltage protective switch circuit; the input end of this low-voltage protective switch circuit is connected between the internal reference voltage leading-out ends of anodal and described pulse width controller integrated circuit of described input rectifying filtering circuit; when the potential difference (PD) between the internal reference voltage leading-out ends of the positive pole of described input rectifying filtering circuit and described pulse width controller integrated circuit is higher than setting value; this low-voltage protective switch circuit is just open-minded, to the over-current detection end input high level signal of described pulse-width controlled integrated circuit.

5. switching power unit according to claim 3; it is characterized in that: it the positive pole of input rectifying filtering circuit and the over-current detection input end of described pulse width controller integrated circuit between be connected to a low-voltage protective switch circuit; the input end of this low-voltage protective switch circuit is connected between the internal reference voltage leading-out ends of anodal and described pulse width controller integrated circuit of described input rectifying filtering circuit; when the potential difference (PD) between the internal reference voltage leading-out ends of the positive pole of described input rectifying filtering circuit and described pulse width controller integrated circuit is higher than setting value; this low-voltage protective switch circuit is just open-minded, to the over-current detection end input high level signal of described pulse-width controlled integrated circuit.