Summary of the invention
The present invention is the problems referred to above that will solve prior art, proposes one after input voltage falls (working power power down) in short-term, can provide a delays time to control pulse, forbids that power-supply system or other power consumption equipments shut down in short-term and restart at once.
For solving the problems of the technologies described above, the technical scheme that the present invention proposes is the monostable protection circuit that a kind of power down of design triggers, and comprising: energy-storage module, and its input connects working power, in order to storage operation electric energy; Reference voltage module, connects energy-storage module output, in order to output reference voltage; Power down trigger module, connects power-off signal end and energy-storage module respectively, exports the trigger impulse of after having power down triggering signal; Comparison module, two input connects the output of reference voltage module and power down trigger module respectively, reference voltage and trigger impulse is compared, and exports one in order to control the control impuls of controlled circuit according to comparative result comparison module output.
Comparison module output be connected in series one between controlled circuit in order to amplify the output module of described control impuls.
Above-mentioned energy-storage module comprises and is serially connected in the second diode between working power and ground and the 3rd electric capacity successively, wherein the anode of the second diode connect working power, negative electrode connect the 3rd electric capacity and this tie point as energy-storage module output.
Said reference voltage module can for being serially connected in the 8th resistance between described energy-storage module output and ground and the 9th resistance, and the tie point of the 8th resistance and the 9th resistance exports described reference voltage.
Said reference voltage module also can for being serially connected in the voltage stabilizing chip between described energy-storage module output and ground, and voltage stabilizing chip exports described reference voltage.
Above-mentioned power down trigger module comprises triode, its base stage by series connection the first resistance and the first electric capacity connect described power down triggering signal end, grounded emitter, first diode in parallel and the second resistance between base stage with emitter, be connected in series the 3rd resistance and the 4th resistance between collector electrode with described energy-storage module output, the tie point of the 3rd resistance and the 4th resistance be connected in series the second electric capacity between ground and this tie point exports described trigger impulse.
Above-mentioned comparison module comprises comparator, and its inverting input accesses described trigger impulse, and in-phase input end connects described reference voltage by the 6th resistance, and indirect 5th resistance of in-phase input end and output, output carries described control impuls.
Above-mentioned output module is field effect transistor, and its grid connects the output of described comparison module, source ground, and drain electrode accepts control circuit.
Compared with prior art, the present invention provides a delays time to control pulse after working power power down, forbid that power-supply system or other power consumption equipments shut down in short-term and restart at once, efficiently avoid start timing error, the dysfunction situations such as energy pours in down a chimney appear in power-supply system.And circuit is simple and reliable, only need little pcb board face, components and parts all can adopt general-purpose device at a low price, with low cost, have wide market prospects.
Embodiment
Present invention is disclosed the monostable protection circuit that a kind of power down triggers, referring to Fig. 1, it comprises the energy-storage module, reference voltage module, power down trigger module, the comparison module that are connected to each other.Wherein:
The input of energy-storage module connects working power, in order to storage operation electric energy.When working power is set up, working power is charged to energy-storage module, and after working power power down, energy-storage module provides electric energy only to comparison module, reference voltage module and output module.
Reference voltage module, connects energy-storage module output, in order to output reference voltage.Reference voltage determines the roll over condition exporting delay pulse.
Power down trigger module, connects power-off signal end and energy-storage module respectively, exports the trigger impulse of after having power down triggering signal.It may be noted that power down triggering signal is sent by the power-fail detection circuit of power-supply system or power consumption equipment, when also can be shutdown when both can be power down, send this signal.
Comparison module, two input connects the output of reference voltage module and power down trigger module respectively, reference voltage and trigger impulse is compared, and exports one in order to control the control impuls of controlled circuit according to comparative result comparison module output.Comparison module can be made up of the device of the high input impedance such as amplifier or comparator, reference voltage and trigger impulse is compared and produces monostable delay pulse (i.e. control impuls), and have certain return difference, prevent output jitter.
In the preferred embodiment comparison module output be connected in series one between controlled circuit in order to amplify the output module of described control impuls.Output module also can carry out reversal to control impuls, increases driving force or change the process such as output timing, and the control impuls of amplification can connect the enable control signal interface of the startup of controlled circuit (as power-supply system or power consumption equipment).When control impuls arrives, controlled circuit cannot start, and protection power source system or power consumption equipment short time power down or the horse back again that shuts down are restarted by this, efficiently avoid start timing error.
Referring to the preferred embodiment shown in Fig. 2, energy-storage module comprises and is serially connected in the second diode D2 between working power VCCP and ground and the 3rd electric capacity C3 successively, wherein the anode of the second diode connect working power, negative electrode connect the 3rd electric capacity and this tie point as energy-storage module output.Energy-storage module and the unidirectional isolation of working power, so-called unidirectional isolation refers to that energy-storage module is connected by diode with working power, only absorbs energy from working power, and not to release energy to other circuit being connected on working power.
Referring to the preferred embodiment shown in Fig. 2, reference voltage module is be serially connected in the 8th resistance between described energy-storage module output and ground and the 9th resistance, and the tie point of the 8th resistance and the 9th resistance exports described reference voltage.The terminal of reference voltage is Vref, and the 8th resistance and the 9th resistance are not drawn.
Referring to the preferred embodiment shown in Fig. 2, reference voltage module is be serially connected in the voltage stabilizing chip between described energy-storage module output and ground, and voltage stabilizing chip exports described reference voltage.The terminal of reference voltage is Vref, and voltage stabilizing chip is not drawn.
Referring to the preferred embodiment shown in Fig. 2, power down trigger module comprises triode Q1, its base stage by series connection the first resistance R1 and the first electric capacity C1 connect described power down triggering signal end (input terminal of triggering signal is Trigger), grounded emitter, first diode D1 in parallel and the second resistance R2 between base stage with emitter, be connected in series the 3rd resistance R3 and the 4th resistance R4 between collector electrode with described energy-storage module output, the tie point of the 3rd resistance and the 4th resistance be connected in series the second electric capacity C2 between ground and this tie point exports described trigger impulse.
Referring to the preferred embodiment shown in Fig. 2, comparison module comprises comparator U1, its inverting input accesses described trigger impulse (namely connecting the tie point of R3, R4), in-phase input end meets described reference voltage V ref by the 6th resistance R6, the indirect 5th resistance R5 of in-phase input end and output, output carries described control impuls.
Referring to the preferred embodiment shown in Fig. 2, output module is field effect transistor Q2, and its grid connects the output of described comparison module, source ground, and drain electrode accepts control circuit.
Fig. 3 shows the oscillogram of preferred embodiment, above a line be power down triggering signal, below a line be control impuls.
Below in conjunction with Fig. 2 and Fig. 3 in detail, this circuit working principle is described in detail.In figure, D1 and C3 forms energy-storage module, and VCCP is working power, and its to fall with input power and power down.Voltage identification after diode D1 isolates is VCC.Vref is the constant reference voltage produced by devices such as electric resistance partial pressure or voltage stabilizing chips by VCC.Q1, R1, C1, D1, R2, R3, R4, C2 form power down circuits for triggering, and U1, R6, R5 form comparison module, and Q2 forms output module.Trigger signal is the high level signal that in power-supply system or power consumption equipment, power-fail detection circuit exports, and at this level from the low rising edge uprised, by conducting Q1 once, then turns off.After Q1 conducting to the C2 electric discharge of comparison module once, when C2 voltage is lower than U1 in-phase end voltage, U1 exports high level, and makes the Q2 conducting of output circuit, and control impuls is low level.After C2 electric discharge, VCC is charged to C2 by R4, and C2 voltage is raised, and when C2 voltage is higher than U1 in-phase end voltage, U1 output low level, namely output circuit Q2 pipe turns off.As shown in Figure 3, wherein low level time T is determined by the time constant of R4, C2 the A point output waveform of Q2, and the voltage amplitude of time delayed signal is determined by external circuit.The A point of Q2 is connected for starting enable control interface with power-supply system or power consumption equipment, forbids that power-supply system or power consumption equipment restart, thus ensure enough resetting times in T time.
Be more than the embodiment of the control impuls of an output low level of this patent, remove Q2(and namely remove output module), the control impuls directly exporting high level also belongs to this patent protection range.
Above embodiment is only and illustrates, non-ly provides constraints.Anyly do not depart from the application's spirit and category, and to its equivalent modifications of carrying out or change, among the right that all should be contained in the application.