Background technology
In modern industry is produced, all very high to load power supply reliability General Requirements, particularly essential industry load, the voltage dip of the even several cycles of short time power failure all likely causes parturient paresis, causes heavy losses to enterprise.How to improve the power supply reliability to load, play the performance of the relay of protection control action and playing the part of considerable role.By analysis, in order to improve the operate time of the degree of load power supply reliability being depended on to relaying protection.Concerning speed-sensitive switch, depend primarily on pull up time the operate time of relaying protection.Therefore, reduce pull up time as far as possible, improve load power supply reliability, the fault and the power-off time that reduce system are very necessary.
Relay is a kind of electronic control device, it has control system (claim not only input circuit) and by control system (but also claiming output loop), conventionally be applied in automatic control circuit, it is actually the one " automatic switch " of removing to control larger electric current with less electric current.Its action principle is in the time that input variable (as voltage, electric current) reaches setting, makes the electrical equipment of controlled output circuit conducting or disconnection.
In existing relay product, mainly contain electromagnetic type and solid state.At present, electromagnetic relay is widely used in industrial production.It has many good qualities, as: low residual output voltage, many group contacts and normally-open normally-close contact, leakage current and AC and DC compatibilities etc. can be provided.But also there are many shortcomings in it, as: maximum switching frequency limited (5-10Hz), response speed slow (reaching tens ms levels), operating voltage, electric current and maintain that voltage, electric current are identical to control power consumption high, usually above 200mW, switch motion can not Complete Synchronization, current practice poor performance and connect and need interface etc. with digital loop greatly.Its structural representation as shown in Figure 1.
Along with the extensive use of relay in industrial production, can not use at some occasion electromagnetic relay especially, as: require low in energy consumption and digital circuitry directly compatible, require that control response speed is fast, power factor (PF) is very low and guarantee the application scenarios such as switch is stable, solid-state relay has the trend that replaces traditional electrical magnetic relay, because solid-state relay has many advantages, as: control low in energy consumption, conventionally 10-50mW, can to realize synchro switch, life-span long, be electromagnetic relay 50-100 doubly, response time (us level) and with digital circuit compatibility etc. soon.But also there is shortcomings in it, as: having residual output voltage 1-1.6V, output can only be AC or DC, can not compatibility, inapplicable little output signal, have leakage current and only have single contact etc.Its structural representation as shown in Figure 2.
For this reason, can utilize the advantage of electromagnetic relay and solid-state relay, abandon both shortcomings, develop a kind of low-power consumption, fast response time, be of great significance with the brand-new relay tool of digital circuit compatibility and output AC and DC compatibility
Summary of the invention
The purpose of this utility model is take the control technology of power electronic device as basis, and a kind of control drive circuit of protecting with relay is provided, and takes effectively to control and reduces pull up time and power consumption.During relay closes a floodgate, realize the quick-response excitation of relay control coil; During relay separating brake, realize the quick de-excitation of relay control coil; Maintain close stage at relay, reduce the exciting current of relay control coil.
The technical solution of the utility model: protection of the present utility model comprises and drives main circuit and control circuit thereof with the accessory drive of relay; drive main circuit by diode D1, D2 and two unidirectional bridge rectifiers that switch transistor T 1, T2 and DC power supply E form; the output of unidirectional bridge rectifier connects relay coil JL, and control circuit comprises with two switch transistor T 1, T2 and divides other first control circuit being connected and second control circuit.
Described first control circuit comprises timer, the output of timer is connected to the input of the first comparator and the second comparator, the output of the first comparator and the second comparator is connected to the input of logical AND circuit, the output of logical AND circuit connects the selecting side of selector switch, the output of selector switch connects a PWM and forms circuit, and the output that a PWM forms circuit connects the first shaping circuit and an IGBT drive circuit successively; Second control circuit comprises second timer, and the output of second timer connects the 2nd PWM and forms circuit, and the output that the 2nd PWM forms circuit connects the second shaping circuit and the 2nd IGBT drive circuit successively.
The control end of described selector switch is connected with duty cycle pulse generator and first timer.
Advantage of the present utility model: compare with the control circuit of electromagnetic relay and solid state relay, control circuit provided by the utility model and the control strategy adopting can reduce the power consumption of pull up time and control circuit greatly, can and export AC and DC compatibility with digital circuit compatibility, control circuit is simple and reliable, and control strategy is simply easy to implement.
Embodiment
Below with reference to accompanying drawing, the preferred embodiments of the present invention are described in detail; Should be appreciated that preferred embodiment is only for the present invention is described, rather than in order to limit the scope of the invention.
Fig. 1 is circuit theory schematic diagram of the present utility model: the accessory drive of protection of the present utility model relay comprises driving main circuit and control circuit thereof; it drives main circuit by diode D1, D2 and two unidirectional bridge rectifiers that switch transistor T 1, T2 and DC power supply E form; the output of unidirectional bridge rectifier connects relay coil JL, and control circuit comprises with two switch transistor T 1, T2 and divides other first control circuit being connected and second control circuit.
Fig. 2 is control circuit principle schematic: described first control circuit comprises timer, the output of timer is connected to the input of the first comparator and the second comparator, the output of the first comparator and the second comparator is connected to the input of logical AND circuit, the output of logical AND circuit connects the selecting side of selector switch, the output of selector switch connects a PWM and forms circuit, and the output that a PWM forms circuit connects the first shaping circuit and an IGBT drive circuit successively; Second control circuit comprises second timer, and the output of second timer connects the 2nd PWM and forms circuit, and the output that the 2nd PWM forms circuit connects the second shaping circuit and the 2nd IGBT drive circuit successively.The control end of described selector switch is connected with duty cycle pulse generator and first timer.
The effect of the each device of first control circuit is summarized as follows: the first timer is for the measurement of time; Comparator, for measured time and reference value are compared, when higher than this value, is exported high level.Otherwise, output low level; Logical AND is for the computing of the "AND" of two conditions; Selector switch is selected control signal for the operation result by logical AND, in the time that the time of the first timer is greater than 0.03s and is less than 0.05s, selector switch is selected the output signal of variable duty ratio pulse generator, and other times are selected the output signal of first timer; First timer is for generation of one with the control signal that preset time, point changed, and during the time is 0-0.01s, output low level, during the time is 0.01-0.05s, exports high level, when the time is greater than after 0.05s, and output low level again; The one PWM forms circuit and forms PWM pulse width modulated wave by control signal, and its carrier frequency is 10kHz; The first shaping circuit, for improving the edge characteristic of PWM pulse width modulated wave, improves its steepness; The one IGBT drive circuit, for providing suitable grid voltage to IGBT, guarantees the reliable turn-on and turn-off of IGBT.
Second control circuit is identical with the effect of the corresponding each device of first control circuit.Just maintain period of contact at relay, there is no the duty cycle adjustment part of first control circuit.
The technical measures that the utility model is taked are described as follows:
(1) the required DC power supply of the utility model, the voltage of needed DC power supply should be greater than relay control coil and normally work time, the voltage and current that the nargin of required DC power supply can bear according to relay control coil is selected.
(2) the utility model adopts switch transistor T 1, T2 are full-control type power electronic switch, and as IGBT, MOSFET etc., the heap(ed) capacity that its capacity can bear according to the capacity of DC power supply and relay control coil is determined.
(3) the utility model also can be applicable to the relay of AC excitation.
As shown in the figure: during relay closes a floodgate: this one-phase needs relay control coil electric current to rise rapidly, realizes the quick-response excitation of control coil.Close a floodgate after order when providing, switch transistor T 1, T2 conducting simultaneously, DC power supply E is added on relay control coil by switch transistor T 1, T2, and now the exciting current direction of control coil is to A by B.Simulation result demonstration, reaching maximum exciting current required time is 10ms, exciting current climbing speed is 100A/s, thereby has realized the rapid combined floodgate of relay.
Relay maintains period of contact: this one-phase remains closed in order to maintain relay contact, and required exciting current is less than the exciting current of relay adhesive.By taking certain control strategy, allow switching tube T2 conducting always, and switch transistor T 1 is according to certain duty ratio conducting.Therefore, the voltage being added on control coil JL is DE, and E is direct voltage, and D is duty ratio, and duty ratio is 50%. in actual applications, and concrete duty ratio can remain closed needed size of current according to switch and determine.Simulation result demonstration, is kept closed for maintaining relay contact JK, and required exciting current only needs 50% of maximum exciting current, thereby has reduced the power consumption of control relay circuit.
During relay separating brake: the electric current that this one-phase need to flow through control coil declines rapidly, realize the quick de-excitation of control coil.When providing after separating brake order, cancel rapidly the driving pulse of switch transistor T 1, T2, control coil electric current is through two diode D1, D2 and DC power supply E afterflow, the voltage that is now added in control coil JL two ends is negative direct voltage, thereby the rapid decrease speed of the exciting current that causes control coil JL, now the exciting current direction of control coil JL is still by B to A, but the electromotive force of control coil A end is held higher than B.Show by result, by maintaining electric current, to drop to zero required time be 1ms to relay, and exciting current fall off rate is 5000A/s, has realized quick de-excitation, thereby has realized the rapid separating brake of relay.
Fig. 3 is the voltage of relay control coil and the electric current oscillogram in each stage: in order to reduce pull up time and power consumption, the technical measures that the utility model is taked are as follows:
(1) during relay closes a floodgate
In the scope of the voltage and current can bear at relay control coil, sufficiently high direct voltage is provided as far as possible, and object is to increase relay control coil exciting current, improves the climbing speed of exciting current, realize the rapid excitation of relay control coil, reduce the closing time of relay.By simulation analysis, reaching maximum exciting current required time is 10ms, and exciting current climbing speed is 100A/s.Therefore, greatly reduced the closing time of relay.
(2) relay maintains period of contact
In order to reduce the power consumption of relay, maintain period of contact at relay and take suitably to reduce to be added in the control voltage on control coil, reduce the exciting current of relay control coil.Only need to guarantee that the dynamic and static contact of relay can remain closed, and so just can reduce the power consumption of relay drive circuit.By simulation analysis, be kept closed for maintaining relay, required exciting current only needs 50% of maximum exciting current.Therefore, greatly reduced the power consumption of control relay circuit.
(3) during relay separating brake
In order to reach the opening time that reduces relay, the control strategy of taking is to remove rapidly the forward voltage that is added in control coil, in the voltage range can bear at relay control coil, and apply high as far as possible reverse voltage, to the rapid degaussing of control coil, improve the fall off rate of control coil exciting current.By simulation analysis, by maintaining electric current, to drop to zero required time be 1ms to relay, and exciting current fall off rate is 5000A/s.Therefore, greatly reduced the opening time of relay.