CN201708515U

CN201708515U - Power protection circuit

Info

Publication number: CN201708515U
Application number: CN2010202195196U
Authority: CN
Inventors: 王坚
Original assignee: TCL Corp; Shenzhen TCL New Technology Co Ltd
Current assignee: TCL Corp; Shenzhen TCL New Technology Co Ltd
Priority date: 2010-06-08
Filing date: 2010-06-08
Publication date: 2011-01-12
Anticipated expiration: 2020-06-08

Abstract

The utility model provides a power protection circuit, which comprises a power switch and a control circuit. The control circuit is connected between the enabling end and the signal end of the power switch, and when the power switch detects that the signal end outputs a lower level due to over-current or over-voltage power input, the level of the enabling end of the power switch can be pulled low to cut off the power output of the power switch. Since the USB over-voltage or over-current protection circuit consists of the power switch with over-voltage or over-current output signals and the external control circuit, and the expensive USB controller or microprocessor is replaced by the inexpensive circuit, the utility model realizes the purposes of reducing the cost and simplifying the design. The utility model is suitable for audio-visual products with USB interfaces, such as color televisions, or similar equipment and similar power supply ports.

Description

A kind of power protecting circuit

Technical field

The utility model relates to the power protection of electronic equipment, relates in particular to a kind of power protecting circuit.

Background technology

Many now electronic equipments are colour TV for example; portable multimedia device etc. all with USB interface as basic Peripheral Interface; the USB interface power configuration of standard as shown in Figure 1; it is made up of the power switch RT9711 and the USB controller USB Controller of band over-voltage and over-current output signal; the power input of described power switch RT9711 connects the 5V power supply; signal end FLG meets USB controller USB Controller; Enable Pin EN receives enable signal Chip Enable; earth terminal GND ground connection; power output end VOUT connects the power end VBUS of USB interface; the earth terminal GND ground connection of USB interface; signal end D+ and D-receive data Data; wherein; when over-voltage and over-current appears in power supply; the signal end FLG of power switch RT9711 can export a low level signal and give USB controller USB Controller; control signal of USB controller USB Controller output is turn-offed RT9711; reach the purpose of overvoltage and overcurrent protection; this kind scheme is the USB interface power supply way of standard, and shortcoming is the expensive price of USB controller.Chinese patent CN200820092958.8 has provided a kind of power supply controlling schemes; as shown in Figure 2; described colour TV comprises display screen; loudspeaker arrangement; audio process; microprocessor; overcurrent protective device and USB device; the Enable Pin ENABLE of microcontroller connection overcurrent protective device and signal end FLAG are to provide enable signal and control signal; the power input Vin of overcurrent protective device connects the 5V power supply; power output end Vout is the USB device power supply; earth terminal GND ground connection; adopt the microprocessor of colour TV itself to discern and control the USB power supply in this scheme; the function of serving as the USB controller; its advantage is to reduce cost; shortcoming is two I/O mouths that will take microprocessor; and need cooperate with software, this can't realize under the mcu resource condition of limited.

Summary of the invention

The purpose of this utility model is to provide a kind of scheme, utilizes cheap peripheral cell to constitute the function that control circuit reaches the USB controller, and the power protecting circuit of a cheapness is provided for the USB power supply.

Technical solutions of the utility model are:

The utility model provides a kind of power protecting circuit; comprise power switch and control circuit; wherein; described control circuit is connected between the Enable Pin and signal end of described power switch; detect power supply input overcurrent or overvoltage and during at power switch, the Enable Pin level of power switch is dragged down the power supply output of closing power switch in its signal end output low level.

Described power protecting circuit, wherein, the Enable Pin of described power switch also is connected with the signal end of microprocessor, is controlled its conducting or is closed by microprocessor.

Described power protecting circuit; wherein; described control circuit comprises first and second transistors; first to fourth resistance and first and second electric capacity; the emitter of described the first transistor is connected to the signal end of microprocessor by first resistance; and be directly connected to the Enable Pin of power switch; its collector electrode is by the parallel circuits ground connection of the 3rd resistance and second electric capacity; and directly connect the base stage of transistor seconds; its base stage is connected to the collector electrode of transistor seconds; the grounded emitter of described transistor seconds; base stage connects the collector electrode of the first transistor; collector electrode is connected to the emitter of the first transistor by the parallel circuits of second resistance and first electric capacity, and connects the signal end of power switch by the 4th resistance.

Described power protecting circuit, wherein, described the first transistor is a PNP transistor, described transistor seconds is a NPN transistor.

Described power protecting circuit, wherein, described power switch is the RT9711 power switch, conducting when its Enable Pin is high level, power output end has voltage output, and Enable Pin is closed the output of power output end no-voltage during for low level.

The USB over-voltage over-current protection circuit that the utility model provides; power switch and peripheral control circuit by band over-voltage and over-current output signal constitute; circuit with cheap and simple replaces expensive USB controller or microprocessor; reach reduce cost, the purpose of simplified design, this circuit is fit to audio-visual products or similar devices such as the colour TV of band USB interface and the port of similarly powering uses.

Description of drawings

Fig. 1 is the USB power configuration figure of standard;

Fig. 2 discerns and controls the theory diagram of USB power supply over-voltage over-current protection with single-chip microcomputer;

The circuit diagram of Fig. 3 the utility model power protecting circuit better embodiment.

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.

Please referring to Fig. 4; the utility model power protecting circuit better embodiment comprises power switch RT9711 and control circuit; described power switch RT9711 comprises Enable Pin EN; signal end FLG; earth terminal GND; power input VIN and power output end VOUT; the power input VIN of described power switch RT9711 and power output end VOUT are used for the USB voltage of input and output+5V; described control circuit comprises: transistor T 1 and T2; resistance R 1～R4 and capacitor C 1 and C2; described transistor T 1 is a PNP transistor; its emitter E is connected to the CONT end of microprocessor MCU on the one hand by resistance R 1; be directly connected to the Enable Pin EN of power switch RT9711 on the other hand; its collector electrode C is on the one hand by the parallel circuits ground connection of resistance R 3 with capacitor C 2; be directly connected to the base stage B of transistor T 2 on the one hand; its base stage B is directly connected to the collector electrode C of transistor T 2; described transistor T 2 is a NPN transistor; its emitter E ground connection; base stage B connects the collector electrode C of transistor T 1; collector electrode C is connected to the emitter E of transistor T 1 on the one hand by the resistance R 2 and the parallel circuits of capacitor C 1, be connected to the signal end FLG of power switch RT9711 on the other hand by resistance R 4.

Its course of work is as follows: the signal end CONT of microprocessor MCU links to each other with the Enable Pin EN of power switch RT9711; by the conducting of the control signal power controlling switch RT9711 of microprocessor MCU output with close; signal end CONT output high level power switch RT9711 in the season conducting of described microprocessor MCU; its power output end VOUT has voltage output; output low level power switch RT9711 in season turn-offs; the output of its power output end VOUT no-voltage; described control circuit is by transistor T 1 and T2; elements such as resistance R 1～R4 and capacitor C 1 and C2 constitute; form a ghyristor circuit; when power switch RT9711 inside detects power supply input overcurrent or overvoltage is arranged; the transistor turns of its inside; low level of output on signal end FLG; for providing base current, transistor T 1 makes its conducting by resistance R 4; then allow transistor T 2 also follow conducting; ghyristor circuit conducting and locking that transistor T 1 and T2 are connected into; the Enable Pin EN of power switch RT9711 drawn by high level be low level; in case occur low level on the Enable Pin EN; the effect of power protection is played in the off voltage output immediately of the internal switch of power switch RT9711.

The USB over-voltage over-current protection device that the utility model better embodiment provides; power switch RT9711 and peripheral control circuit by band over-voltage and over-current output signal constitute; circuit with cheap and simple replaces expensive USB controller or microprocessor; reach reduce cost, the purpose of simplified design; the audio-visual productss such as colour TV that this circuit is fit to the band USB interface use; can certainly be applied to similar devices and the port use of similarly powering, be not limited to protect the USB power supply of 5V.

Should be understood that; the above only is a better embodiment of the present utility model; not in order to limit protection range of the present utility model; for those of ordinary skills; any modification of being done according to the above description, be equal to and replace and improvement etc., all should be included within the protection range of the present utility model.

Claims

1. power protecting circuit; comprise power switch and control circuit; it is characterized in that: described control circuit is connected between the Enable Pin and signal end of described power switch; detect power supply input overcurrent or overvoltage and during at power switch, the Enable Pin level of power switch is dragged down the power supply output of closing power switch in its signal end output low level.

2. power protecting circuit according to claim 1 is characterized in that the Enable Pin of described power switch also is connected with the signal end of microprocessor, is controlled its conducting or is closed by microprocessor.

3. power protecting circuit according to claim 2; it is characterized in that; described control circuit comprises first and second transistors; first to fourth resistance and first and second electric capacity; the emitter of described the first transistor is connected to the signal end of microprocessor by first resistance; and be directly connected to the Enable Pin of power switch; its collector electrode is by the parallel circuits ground connection of the 3rd resistance and second electric capacity; and directly connect the base stage of transistor seconds; its base stage is connected to the collector electrode of transistor seconds; the grounded emitter of described transistor seconds; base stage connects the collector electrode of the first transistor; collector electrode is connected to the emitter of the first transistor by the parallel circuits of second resistance and first electric capacity, and connects the signal end of power switch by the 4th resistance.

4. power protecting circuit according to claim 3 is characterized in that, described the first transistor is a PNP transistor, and described transistor seconds is a NPN transistor.

5. according to the described power protecting circuit of arbitrary claim in the claim 1 to 4, it is characterized in that described power switch is the RT9711 power switch; conducting when its Enable Pin is high level; power output end has voltage output, and Enable Pin is closed the output of power output end no-voltage during for low level.