The synchronous galvanometer circuit of electromagnetic oven
Technical field
The utility model relates to a kind of testing circuit, especially relates to a kind of synchronous galvanometer circuit for electromagnetic oven.
Background technology
The synchronous galvanometer circuit of existing electromagnetic oven comprises rectifier bridge heap, choke induction, filter capacitor, induction drum, resonant capacitance, voltage comparator, high withstand voltage resistance and electric capacity etc. as shown in Figure 1.The characteristics of this circuit are that component number is many, volume is big, circuit structure is complicated.And, because the component number that needs is more relatively, and cause its cost height, volume is big and reliability is low, in addition because the circuit structure complexity, interference free performance is wayward, hardware design is debugged and maintenance difficulty is big, thereby requires exploitation debugging and maintenance personal must have higher technical merit.
The utility model content
Be to solve prior art problems, the utility model proposes that a kind of circuit structure is simple, the accuracy height of current tracking signal, the synchronous galvanometer circuit of electromagnetic oven that antijamming capability is stronger.
The utility model adopts following technical scheme to realize: the synchronous galvanometer circuit of a kind of electromagnetic oven, comprise: rectifier circuit, the choke induction that is connected the rectifier circuit output and filter capacitor, the induction coil that is connected in series with choke induction, and the resonant capacitance in parallel with induction coil; Colelctor electrode is connected the power transistor of induction coil and resonant capacitance common port, grounded emitter; Be connected sampling capacitance and Zener diode between the colelctor electrode of power transistor and the ground; And the common port of sampling capacitance and Zener diode couples the switching device control circuit, and a control end of this switching device control circuit connects the grid of power transistor.
Wherein, the negative electrode of Zener diode connects the negative electrode of diode, and the anode of diode connects external power source VCC by a resistance, and the anode of diode connects the switching device control circuit.
Wherein, the switching device control circuit is single-chip microcomputer, and an one control end connects the grid of power transistor by a resistance.
Compared with prior art, the utlity model has following beneficial effect:
The utility model can obtain the limit of power transistor IGBT1 both end voltage by the electric current reversal point that catches resonant capacitance C3 and induction coil L2, control power transistor IGBT1 in the low limit conducting of voltage by this signal so, just can reach the soft switching purposes of power transistor, thereby the minimizing loss, and increase reliability.
Description of drawings
Fig. 1 is the schematic diagram of existing synchronous galvanometer circuit;
Fig. 2 is the schematic diagram of the synchronous galvanometer circuit of the utility model.
The specific embodiment
As shown in Figure 2, in one embodiment, the synchronous galvanometer circuit that the utility model proposes comprises: input ac voltage is carried out the rectifier circuit that rectification is handled, one of the wherein output serial connection of this rectifier circuit is used for controlling the choke induction L1 of mutation current, between two outputs of rectifier circuit, connect filter capacitor C1, filter capacitor C1 and described choke induction L1 collocation is carried out filtering to the output voltage of rectifier circuit; The induction coil L2 that is connected in series with choke induction L1, and the resonant capacitance C3 in parallel with induction coil L2; And induction coil L2 is connected the colelctor electrode (C) of power transistor IGBT1 with the common port of resonant capacitance C3, and emitter stage (E) ground connection of this power transistor IGBT1, grid (G) connect the switching device control circuit; The colelctor electrode of power transistor IGBT1 is by sampling capacitance C2, Zener diode Z1 ground connection, and wherein, the other end of sampling capacitance C2 connects the negative electrode of Zener diode Z1, and the anode of Zener diode Z1 connects ground; The current signal that sampling capacitance C2 adopts is sent to the switching device control circuit, is conducting when hanging down limit by voltage between the CE of switching device control circuit control power transistor IGBT1, thereby reduces loss, and increase reliability.
Wherein, the negative electrode of Zener diode Z1 connects the negative electrode of diode D1, and the anode of diode D1 connects external power source VCC by resistance R 1, and the anode of diode D1 connects the switching device control circuit.
In a preferred embodiment, the switching device control circuit is the microcontroller of chip microcontroller, and an one control end connects the grid of power transistor IGBT1 by resistance.
When power transistor IGBT1 is off state, when flow in the described induction coil L2 electric current to from left to right (be shown in Figure 2 in, circuit is flowed to the direction of sampling capacitance C2 by described filter capacitor C1) time, electric current is flowed among described resonant capacitance C3 and the sampling capacitance C2 by described induction coil L2, this moment Zener diode Z1 reverse breakdown, its negative electrode is output as high level.When current direction among the described induction coil L2 is when (flowing to the extremely direction of described filter capacitor C1 by sampling capacitance C2) from right to left, electric current is flowed among the described induction coil L2 by described resonant capacitance C3 and sampling capacitance C2, this moment Zener diode Z1 forward conduction, its cathode voltage is low level.
Along with the change of the sense of current, the cathode voltage of Zener diode Z1 is also just exported corresponding level and is changed, and can predict the electric current reversal point thus.When the current value of described resonant capacitance C3 was zero, the voltage between CE the two poles of the earth of power transistor IGBT1 culminated.Because the electric current of described resonant capacitance C3 comes from described induction coil L2, and the sense of current of inductance can not suddenly change, and can obtain the electric current reversal point and be current zero-crossing point, the voltage at described resonant capacitance C3 two ends arrives limit simultaneously.
From the above, can obtain the limit of the voltage at described power transistor IGBT1 two ends by the electric current reversal point that catches described resonant capacitance C3 and described induction coil L2.Therefore, control described power transistor IGBT1 in the low limit conducting of voltage by this current signal, just can reach the soft switching purposes of power device, thereby reduce loss, and increase reliability.
The above only is preferred embodiment of the present utility model; not in order to limit the utility model; all any modifications of within spirit of the present utility model and principle, doing, be equal to and replace and improvement etc., all should be included within the protection domain of the present utility model.