JPS599460Y2 - Pulse generator for radar equipment - Google Patents

Description

[Detailed description of the invention] This invention reduces the recovery time during SCR switching,
The present invention relates to a pulse generator for a radar device that does not adversely affect images displayed on the radar device.

Pulse generators using SCR are often used in radar equipment to generate driving pulses to be applied to magnetrons, and are generally constructed as shown in FIG.

In FIG. 1, 1 is a DC power supply, and the output voltage of this DC power supply is connected to a pulse forming network via a switch 2 and a charging reactor 3.
rk, hereinafter abbreviated as PFN) 4.

This PFN 4 consists of a capacitor and an inductor, and is a circuit that temporarily stores energy from the DC power supply 1 and converts it into pulse energy.

Further, 6 is an SCR, and this SCR 6 is switched by a trigger pulse from the trigger circuit 7, and the PFN 4
The energy stored in the load 5 will be supplied to the load 5.

That is, in the circuit shown in FIG.
FN4 is applied to charge PFN4, and then the SCR 6 is made conductive by a trigger pulse from the trigger circuit 7, and P
Create a certain closed circuit from FN 4, load 5 and SCR 6,
Discharging the energy stored in the PFN4,
It supplies pulses to the load 5.

In this case, when all the energy stored in the PFN 4 is sent to the load 5 side, the anode current of the SCR 6 becomes zero and becomes less than the holding current, and the SCR 6 recovers the cut-off state, but in reality SC when SCR 6 is conductive
A large amount of carriers are moving in each junction of R6, and even if the anode current becomes less than the holding current, the carriers become accumulated carriers and do not disappear immediately, and the accumulated carriers cause a reverse current. flows.

In other words, as shown in Figure 2, even if the anode current is reduced to zero while the forward current is flowing, the state does not immediately shift to the cutoff state, but the reverse current due to the accumulated carriers described above flows, and there is a delay in recovery of the reverse characteristic. arise.

By the way, this delay time is called recovery time, and the reverse current during this recovery time generates unnecessary spike-like voltage due to the load and circuit inductance, and this spike-like voltage This will have an adverse effect on each element of the circuit or other equipment, and especially in radar equipment, this spike-like voltage will be displayed on the display device and will interfere with observation. Various attempts have been made to remove this spice-like voltage.

For example, it is possible to add an absorption circuit such as a damper circuit to the inductance of a load or circuit that generates a spike voltage, but this method is effective enough even though the circuit structure is complicated and expensive. I can't.

Furthermore, if an SCR with a short recovery time and therefore a small reverse current is used, the generation of voltage spikes can be prevented, but such SCRs are currently difficult to obtain and are extremely expensive.

This invention was made in view of the above circumstances, and SCR
By connecting a diode with a fast recovery time in series with the SCR on the anode side of the SCR, the recovery time of the SCR can be shortened, reverse current can be blocked, and spike-like voltage can be prevented from occurring, which can interfere with radar observation. It is an object of the present invention to provide a pulse generator for a radar device that prevents the

An embodiment of the present invention will be described below with reference to FIG. 3, in which the same parts as in FIG. 1 are denoted by the same reference numerals.

In FIG. 3, 8 is a diode connected in the same direction as the SCR 6 and in series with the SCR.

In general, diodes have a faster recovery time than SCRs, have very little reverse current, and are also inexpensive.

By the way, the rating of the diode 8 is SCR.
Any ordinary diode may be used as long as it can sufficiently withstand the current flowing through the diode 6 or the applied voltage, but it is particularly effective if a diode with a fast recovery time is selected as the high recovery diode.

As shown in FIG. 3, in a pulse generator in which a diode 8 is inserted in series with the SCR 6, the switch 2 is now closed and the energy from the DC power supply 1 is transferred to the PFN 4 via the charging reactor 3. If the SCR 6 is made conductive by the trigger signal from the trigger circuit 7 after charging the PFN 4, the charged charge of the PFN 4 will be transferred through the diode 8 and the SCR 6 since the diode 8 is connected in the forward direction. It is discharged and a pulse is supplied to a load 5, such as a magnetron, of a radar device.

In this way, when all the charges stored in PFN4 are discharged, the anode current of SCR 6 becomes zero, and the SCR
While the forward current is flowing through SCR 6, the carriers generated in SCR 6 will disappear, but in this case, since diode 8 with a fast recovery time is installed in series with SCR 6,
The recombination time of the accumulated carriers in the CR 6, ie the recovery time in which the carriers disappear, is dominated by the recovery time of the diode 8, and the recovery time of the SCR 6 is also very fast.

Therefore, reverse current due to accumulated carriers is also suppressed, and the generation of spike-like voltages to each element of the circuit or other devices can be eliminated.

According to experiments conducted by the present inventor, in the device shown in Fig. 1, the SCR voltage is 500V, and the forward current is IOOA.
When the SCR 6 shuts off under the condition of (peak value), a reverse current of about 10 A (peak value) flows due to the accumulated carriers, which causes a spike voltage.
According to the device of the present invention, in which a diode 8 is inserted in series with the diode 6, the reverse current is suppressed to less than 100 mA (peak value) under the same conditions, and therefore there is almost no spike-like voltage generation in the external circuit. Got the results.

As described above, according to the present invention, by inserting a diode in series with the SCR in a pulse generator for a radar device using an SCR, which has a short recovery time, It immediately eliminates the accumulated carriers in the SCR, suppresses the reverse current when the SCR is cut off, and prevents the generation of spike-like voltages to other circuits or devices, thereby projecting a clear image on the display screen of the radar device. It is possible to provide a pulse generator for a radar device.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing a conventional pulse generator for radar equipment; Fig. 2 is a waveform diagram for explaining the operation of the conventional device shown in Fig. 1; and Fig. 3 shows an embodiment of the present invention. This is a schematic diagram. 6...SCR, 8...Diode.

Claims (1)

[Scope of utility model registration request] In a pulse generator for a radar device that uses an SCR as a switching element to charge and discharge a charge storage circuit to generate a pulse, and uses this pulse as a driving pulse for the radar device, a recovery timer is connected in series to the anode side of the SCR. A pulse generator for radar equipment characterized by inserting a fast diode to suppress unnecessary transient voltage during discharge so as not to interfere with radar equipment observation.