CN2438273Y

CN2438273Y - Circuit for detecting power supply voltage cut-in point

Info

Publication number: CN2438273Y
Application number: CN 00235612
Authority: CN
Inventors: 卢世彬
Original assignee: Micon Design Tech Co Ltd
Current assignee: Micon Design Tech Co Ltd
Priority date: 2000-06-12
Filing date: 2000-06-12
Publication date: 2001-07-04
Anticipated expiration: 2010-06-12

Abstract

A circuit for detecting the switching point of power supply voltage is composed of a voltage divider for receiving a power supply voltage, dividing it into a reference voltage, an upper limit voltage and a lower limit voltage, a comparator for comparing the upper limit voltage with the lower limit voltage and outputting them, and a Schmitt trigger circuit for receiving the signals from the first and second comparators and outputting a high-potential signal when the reference voltage is higher than the upper limit voltage and outputting a low-potential signal when the reference voltage is lower than the lower limit voltage as the reset signal of external control circuit, can effectively prevent the uncertain level state caused by insufficient voltage level and power clutter interference.

Description

Detect supply voltage cutting point circuit

The utility model is kind of a detection supply voltage cutting point circuit, You Zhiqi has the function that produces an electronic signal in response to the variation of supply voltage, can be used as replacement (RESET) the signal input of a microcontroller chip, be subjected to mains voltage level deficiency or power supply noise signal with the effect of avoiding this control chip and disturb and produce uncertain level state.

Because the technology day of semiconductor integrated circuit is also flourishing, its application is day by day extensive, various control circuits mostly occur with the form of microchip, and the control circuit of microchip has suitable sensitiveness for the supply voltage of importing usually, when the supply voltage of input produces noise signal interference or voltage level deficiency, to make this control circuit produce the state of uncertain level, if this control circuit is when controlling an important device or having dangerous device, the uncertain level state of this kind can make control program confusion or mistake, so should do one's utmost to avoid the generation of this kind state; So its solution is the testing circuit of design one supply voltage, before this power supply input control circuit, measured earlier, if the action of a signal with this control circuit do replacement (RESET) appears sending in advance when significantly changing in supply voltage, make it reply the state that initial condition forms uncertain level to avoid influenced by mains fluctuations; Yet the testing circuit of general supply voltage, or title is protective circuit, normally produce a changeless definite value reference voltage, this reference voltage is set at usually can be for the minimum voltage of control circuit regular event, make this reference voltage compare, when supply voltage is lower than this reference voltage, produce reset signal and give this control circuit person with supply voltage two; Though yet this kind circuit has the certain protection effect, but for slight voltage oscillation, its voltage may can be lower than reference voltage sometimes in the extremely short time, but revert on the reference voltage immediately, this kind voltage oscillation may be for this control circuit did not influence, and the action that this kind protective circuit is still reset, and control program interrupted, if the slight voltage instability phenomenon of this kind is too much, then will make control circuit often be in the state that interrupts replacement, the function that causes this control circuit to fail to bring into normal play on the contrary; Based on this kind reason, then generally on this kind protective circuit, can be designed a filter circuit again, in order to the unsettled phenomenon filtering of the supply voltage of blink, and suppress the generation of its reset signal, to avoid the above-mentioned replacement effect that voltage disturbance was caused that does not influence the control circuit normal function; But thus, the design of its protective circuit will be complicated more, and therefore cost also increases.

In view of this, the applicant is after thinking and actual test, finish the utility model eventually and " detect supply voltage cutting point circuit ", main purpose is to provide a kind of and detects mains voltage variations and send the circuit of a reset signal, and is not enough and to the control circuit person of impacting to avoid voltage level.

A purpose more of the present utility model is, a kind of effectively filtering interference that slight supply voltage shakiness is produced is provided, and can makes control circuit carry out operate as normal.

For realizing above purpose, the utility model utilizes a bleeder circuit, one comparison circuit and a Shi Mite circuit, the power supply power supply area is divided into a reference power source, one upper limit power supply and the pressure of once rationing the power supply, this reference voltage can be changed with supply voltage, when being higher than upper voltage limit, this reference voltage can export the high-potential voltage signal, and when being lower than upper voltage limit, can export this reference voltage the low-potential voltage signal, and can utilize the reset signal of this signal as an outer core control circuit, can reach the uncertain level state that prevents that voltage level deficiency and power supply interference from being caused effectively.

In order further understanding to be arranged, do one below with reference to each accompanying drawing and describe in detail characteristics of the present utility model and structural feature.

Fig. 1 is a circuit block diagram of the present utility model.

Fig. 2 is a most preferred embodiment detailed circuit diagram of the present utility model.

Fig. 3 is that reference voltage of the present utility model, upper voltage limit and lower voltage limit change schematic diagram.

Fig. 4 is that supply voltage and the utility model output signal relation with the time is schematic diagram among Fig. 3.

Reference data in the accompanying drawing:

(10) bleeder circuit (20) comparison circuit (21) first comparators

(22) second comparator (30) Shi Mite circuit

, be the detailed circuit diagram of a circuit block diagram of the present utility model and a most preferred embodiment now simultaneously with reference to Figure 1 and Figure 2.It mainly is to include a bleeder circuit (10), a comparison circuit (20) and a Shi Mite circuit (30); Wherein:

This bleeder circuit (10) is to receive a supply voltage (VDD), and this supply voltage divided into a reference voltage (VR), a upper voltage limit (VH) and ration the power supply pressure (VL) once and export, and it should be noted that these three dividing potential drops will change synchronously with this supply voltage (VDD) work;

This comparison circuit (20) is to include first comparator (21) and second comparator (22) at least; Make the positive input terminal of this first comparator (21) receive the upper voltage limit that this bleeder circuit (10) exported and its negative input end receives the reference voltage that this bleeder circuit (10) is exported, and comparative result is exported as a signal; And the positive input terminal of this second comparator (22) receives the lower voltage limit that this bleeder circuit (10) exported and its negative input end receives the reference voltage that this bleeder circuit (10) is exported, and also comparative result is exported as a signal; And this Shi Mite circuit (30) is one to have the circuit that Shi Mite triggers function, with first comparator (21) of accepting this comparison circuit (20) output signal with second comparator (22), its function is, an exportable high potential signal when this reference voltage is higher than upper voltage limit, and reference voltage exportable low-potential signal when being lower than lower voltage limit.

During application, can be simultaneously with reference to Fig. 3 and shown in Figure 4, its Fig. 3 represents the variation of reference voltage (VR), upper voltage limit (VH) and lower voltage limit (VL), and Fig. 4 is that expression is with the supply voltage (VDD) of time and the state of output signal (VO); As seen from the figure, the amplitude of variation of this reference voltage (VR) is comparatively near the form of supply voltage (VDD), it is a magnitude of voltage with supply voltage (VDD) variation, the reference voltage that has fixed value with general protective circuit differs widely, this upper voltage limit (VH) and lower voltage limit (VL) then can optionally be adjusted, as when being set at the critical voltage value of regular event of a core control circuit, then output signal (VO) can be used as the reset signal of this core control circuit; In the time of on reference voltage (VR) is positioned at upper voltage limit (VH), represent that this supply voltage (VDD) is to remain on the magnitude of voltage of normal running, so its output signal (VO) will be exported the signal of a high potential, and be changed to lower voltage limit (VL) when following when reference voltage (VR), represent that this supply voltage (VDD) is magnitude of voltage following that has been lower than normal running, and be the state of voltage level deficiency, to make the signal of output signal (VO) output one electronegative potential, and then the action that impels this core circuit to reset, to guarantee the normal of its action; In addition, for the slight oscillatory regime of supply voltage (VDD), when not being lower than this lower voltage limit (VL) if its moment is lower than this upper voltage limit (VH), or be higher than this lower voltage limit (VL) and when not being higher than this upper voltage limit (VH), neither meeting exerts an influence to output signal (VO), so therefore have the effect of filter circuit (FILTER), can avoid the slightly influencer of vibration of voltage.

It more than is the description of most preferred embodiment of the present utility model, be understood that, more than explanation is as descriptive and nonrestrictive, its scope is limited by claims fully, and those skilled in the art can put before not leaving the utility model scope and do many improvement and change.

Claims

1. A circuit for detecting the cut-in point of power supply voltage, which can be used as the input of control signals of other core control circuits, is characterized in that it includes at least a voltage divider circuit, a comparison circuit and a Schmidt circuit, wherein,

The voltage dividing circuit receives a power supply voltage and divides the power supply voltage into a reference voltage, an upper limit voltage and a lower limit voltage for output, and the three voltages will change synchronously with the power supply voltage;

The comparison circuit at least includes a first comparator and a second comparator; the positive input terminal of the first comparator receives the upper limit voltage output by the voltage divider circuit, and the negative input terminal receives the voltage output by the voltage divider circuit. Output the reference voltage, and output the comparison result as a signal; and the positive input terminal of the second comparator receives the lower limit voltage output by the voltage divider circuit, and its negative input terminal receives the reference voltage output by the voltage divider circuit , and output the comparison result as a signal;

The Schmitt circuit is a circuit with a Schmitt trigger function to receive the output signals of the first comparator and the second comparator of the comparison circuit, and can output a high voltage signal when the reference voltage is higher than the upper limit voltage , and when the reference voltage is lower than the lower limit voltage, a low potential signal can be output.