Detect the device of protection during the circuit abnormal work
Technical field
Detect the device of protection when the present invention relates to a kind of circuit abnormal work, relate in particular to a kind of protective device that is used for the exchange type power control system.
Background technology
Because general isolated form switch mode power all utilizes auxiliary winding to provide control circuit required power supply, (cross as output overload or short circuit, AC supply voltage low etc.) can't operate as normal when the system works condition is unusual for this power supply, and cause control circuit to quit work, system enters constantly the state of start again, existing line design is generally adjusted the energy of accessory power supply or cycle of start again in the following manner, can not burn or damages external equipment because of abnormity of power supply uses to reach power-supply system.
Fig. 1 is existing switch type power supply control circuit figure, IC (integrated circuit) 11 of PWM (pulse modulation) control is with the mode switching transistor Q1 of impulse wave modulation, make the stable voltage of secondary side winding 12 outputs, provide control system required power supply by auxiliary winding 121 simultaneously.The following method of the general employing of existing protection circuit design:
Utilize the resistance R 5 and the diode D1 of auxiliary power circuit to form rectification circuit; Adjust resistance R 3, resistance R 4, resistance R 6, resistance R 7 make the power output maximum of system; Change resistance R 1, resistance R 2, capacitor C 2 are adjusted the circuit start cycle; At output design output current detection circuit; Design other protection circuit.
The shortcoming of this protection circuit design is; because it is very many to influence the factor of this accessory power supply energy size; above-mentioned adjustment will reach optimum state usually must be through constantly test; quite time-consuming and effect is limited, and the output current detection circuit of design can't move when the output short circuit effectively even misoperation takes place when start easily.
Summary of the invention
Detect the control integrated circuit of protection when the objective of the invention is to propose a kind of circuit abnormal work, effectively decision circuitry unusually, when circuit is unusual, can in time detect and provide protection, guaranteeing the safety of system, and cost is lower.
For achieving the above object, when proposing a kind of circuit abnormal work, the present invention detects the device of protection, it is used in the control system, this device comprises a control integrated circuit, this control integrated circuit produces an output voltage signal according to the input voltage signal that control system provides, when this input voltage signal is lower than the default minimum of this control integrated circuit, this control integrated circuit is promptly cut off this output voltage signal, this device also comprises: a testing circuit, lotus root is connected to this control integrated circuit, be used for detecting this output voltage signal, and when this output voltage signal disappears, send an alarm signal; A protective circuit, lotus root is connected to this testing circuit, utilizes this alarm signal to trigger an automatic feedback device or a latch devices, with the safety of protection system.
Detect the device of protection during according to described circuit abnormal work, this input voltage signal is the supply voltage of this control integrated circuit.
When also proposing a kind of circuit abnormal work, the present invention detects the device of protection, it is used in the switch mode power control system, this device comprises a control integrated circuit, this control integrated circuit produces an output voltage signal according to the input voltage signal that the switch mode power control system provides, when this input voltage signal is lower than the default minimum of this control integrated circuit, this control integrated circuit is promptly cut off this output voltage signal, this device also comprises: a testing circuit, lotus root is connected to this control integrated circuit, be used for detecting this output voltage signal, and when this output voltage signal disappears, send an alarm signal; A protective circuit, lotus root is connected to this testing circuit, utilizes this alarm signal to trigger an automatic feedback device or a latch devices, with the safety of protection system.
The method that detects protection during circuit abnormal work that the present invention proposes is used in the control system; this control system comprises a control integrated circuit at least; this control system provides an input voltage signal to this control integrated circuit; this control integrated circuit is according to the variation of this input voltage and output voltage signal comprises the following step:
Detect the output voltage signal of this control integrated circuit; When this output voltage signal disappears, send an alarm signal with trigger protection mechanism.
Detect the method for protection during aforesaid circuit abnormal work, wherein this control system is a kind of switch mode power control system.
Detect the method for protection during aforesaid circuit abnormal work, wherein this control integrated circuit is the control integrated circuit for a kind of exportable reference voltage signal.
Detect the method for protection during aforesaid circuit abnormal work; when wherein this output reference voltage signal input voltage that is this control integrated circuit is lower than the minimum of this control integrated circuit, the output voltage signal that this output reference voltage signal is promptly cut off by this control integrated circuit.
Detect the method for protection during aforesaid circuit abnormal work, wherein this alarm signal is to utilize the variation characteristics of reference voltage signal, is sent with trigger protection mechanism by testing circuit when this control integrated circuit is cut off reference voltage signal.
Detect the method for protection during aforesaid circuit abnormal work, wherein this input voltage is the supply voltage for this control integrated circuit.
Detect the method for protection during aforesaid circuit abnormal work, wherein this alarm signal is to be used for triggering protection mechanisms such as automatic feedback device or latch devices.
The detection protective device during from above-mentioned circuit abnormal work as can be seen; the present invention triggers latch circuit and promptly can play protective effect to power supply from motional feedback circuit by the output voltage signal that detects control integrated circuit; when start, also can prevent misoperation; compared with prior art; need not the various parameters that are provided with of time-consuming adjustment circuit, and the efficient height, effect is obvious; simple in structure, cost is lower.
Be described in further detail below in conjunction with the device of accompanying drawing the detection protection of the present invention's proposition.
Description of drawings
Fig. 1 is the control circuit figure of prior art;
Fig. 2 is the most preferred embodiment that adopts the latch protective circuit;
Fig. 3 is the most preferred embodiment that adopts automatic feedback protection circuit;
Fig. 4 is the most preferred embodiment that adopts other circuits for triggering.
Embodiment
Can find out according to Fig. 2, when the input voltage Vcc of control IC is lower than the default minium operation voltage of control integrated circuit, the reference voltage Vref of control IC 11 output can be reduced to electronegative potential by high potential moment, the transistor Q2 conducting of testing circuit mouth at this moment, the output electronegative potential is to latch (Latch) circuit 14, the exportable block signal 21 of latch circuit, the pinning system, system must turn off the back of its power supply and just can restart, but as do not get rid of unusual, only start again behind the power cutoff, system will repeat said process, pin once more.
According to Fig. 3 as can be seen, when the input voltage Vcc of control IC is lower than the default minium operation voltage of control integrated circuit, the reference voltage Vref of control IC 11 output can be reduced to electronegative potential by high potential moment, MOS (metal-oxide semiconductor (MOS)) the transistor Q2 conducting of testing circuit mouth at this moment, via D2 and R8 feedback (Feedback) signal operating voltage Vcc is reduced respectively, cause control integrated circuit 31 to be closed, and after Q2 ends, restart, whether be closed once more and then will look unusual condition and whether get rid of.
Because this reference voltage signal must just occur after control integrated circuit starts, and the present invention uses this signal to come the initialization testing circuit, so design of the present invention can not produce misoperation when system boot.
With reference to Fig. 4, the operation principle of this circuit is to utilize circuit to take place when unusual, and reference voltage signal can instantaneous trip and still have remaining voltage on the circuit, so just can trigger Q1 and produce a signal enabling protective circuit (for example latch devices or automatic feedback device).Wherein R1 and R2 be exactly because of this feedback voltage may be when the circuit normal operation greater than reference voltage signal, so must carry out dividing potential drop to guarantee not and can misoperation take place when the circuit normal operation to this feedback voltage.
The present invention is topmost to be characterised in that; the reference voltage Vref of utilizing control IC 11 to export is done the detection resources of control system fault; cooperate simple circuit that system implementation is protected; with low cost but high to the protection reliability of the detection of line signal and system safety, be difficult for misoperation or produce fault.
With regard to the application of reality, above-mentioned control IC can be a kind of PWM control IC, and for example model is 3842 or 3843; Be example now with output overload or short circuit, owing in general transformer isolation type transducer, all use auxiliary winding 121 that the power supply of control circuit is provided, and owing to should assist the energy of winding 121 and the proportional relation of energy of output, so when output VO causes its voltage to descend because of overload or short circuit or is zero, auxiliary winding 121 can't normally provide the power supply of control circuit, control in the circuit then will be closed because of operating voltage is not enough, as starting shooting again according to its design that starts circuit, but, form periodic switching on and shutting down if abnormality was not got rid of yet and then will be caused shutting down once more this moment.Design of the present invention promptly is behind system's normal boot-strap; when all generations " unusually " cause control IC 11 shutdown; be trigger signals with control IC 11 reference voltage Vref moment reductions (its upset speed (slew rate) is decided on IC and external circuit); trigger the various protection circuits (comprising testing circuit 13 at least reaches as the protection circuit of latch circuit 14 with level after motional feedback circuit 31 grades) of back level, control system is implemented protection.
Aforesaid " undesired " shutdown comprises: AC supply voltage is low excessively, output overload or short circuit and control circuit fault etc. are non-normally closes the control IC that is caused through AC power and shuts down unusually.
The design of general control IC, its reference voltage all is according to above-mentioned operating voltage size the characteristic that start/shutdown (High/Low) moment switches (High table start shooting Low show to shut down) to be set, so design of the present invention can be widely applicable in the various control system.
Among the present invention, the design of testing circuit and structure are all quite simple, help to shorten the system research development time; The design that simultaneously also is fit to put into control IC.
The present invention still utilizes rectifier, resistor, electric capacity and changeover module to carry out the abnormality detection and the protection of power-supply system; promptly with general isolated form (isolated) transducer (converter) power circuit when condition of work is unusual; the phenomenon of the reference voltage pop-off of the control IC of control circuit is judged unusual condition for detecting, and implements locking (latch), feedback (Auto-recovery) or other protection automatically immediately to design easy circuit.
The present invention can appoint and executes ingenuity and modify arbitrarily by being familiar with this professional those of ordinary skill, but does not all break away from the scope that claim is protected.