JP2792117B2 - Power supply - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device suitable for use in a short-circuited load such as an electron beam gun.

[Conventional technology]

FIG. 4 shows a conventional power supply circuit using a thyristor power regulator. In the figure, 1 is a single-phase AC power supply (voltage v ₀ ), 2 is a thyristor power regulator, A and B are thyristors connected in antiparallel to each other, 3 is a step-up transformer,
Is a single-phase full-wave rectifier, 5 is a reactor, 6 is a capacitor,
7 is a DC load. 8A and 8B are voltage dividing resistors, and 9 is a voltage commander. Voltage command V ^* sent by voltage command device 9 and resistance
8B is a voltage across v _f is input to the error amplifier 10, both deviation ε is input to a phase angle controller 11. The phase angle controller 11 sends the gate signals G _A and G _B to the gates of the thyristors A and B, respectively.

In this arrangement, thyristor A, B conducts receives the gate signal G _A, G _B alternately, the thyristor power regulator 2 delivers an AC voltage v ₁ as shown in FIG. 5 (a). Assuming that the control angles of the thyristors A and B are α and β, respectively, the output of the thyristor power regulator 2 can be adjusted by increasing or decreasing the control angles α and β. The output of the thyristor power regulator 2 is supplied to a full-wave rectifier 4 via a transformer 3, where it is converted to direct current, then smoothed by a smoothing circuit comprising a reactor 5 and a capacitor 6 and fed to a direct current load 7. You.

In this case, if the control angle alpha = beta, the average value is 0 the voltage v _1, it becomes a voltage v ₁ is full AC, thyristor A
If the control angles α and β are slightly different from each other due to the variation in the characteristics of the control angle B and the characteristic of B, for example, if the control angle is small, for example, if α <β, the positive side will be an alternating current including a DC component. As is well known, when the transformer 3 is applied with a complete AC having no DC component, the magnetic flux in the forward direction and the magnetic flux in the reverse direction are generated alternately and equally, so that no residual magnetic flux occurs. When the state of α <β continues, the residual magnetic flux in the positive direction increases with each cycle, and the core of the transformer 3 saturates and the current i ₁ rapidly increases, resulting in a magnetic bias. .

When the DC load 7 is a load that short-circuits at a high voltage like an electron beam gun, a large current flows due to the short-circuit.
If the control angles α and β are slightly different, the above-mentioned magnetization tends to occur, and it is necessary to reliably and promptly eliminate this.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and has as its object to provide a power supply device capable of reliably preventing the transformer from being magnetized.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an averaging circuit for detecting an average value of one cycle of the current transmitted by the thyristor power regulator, and the point of the thyristor power regulator is adjusted so that the output of the averaging circuit becomes zero. According to a second aspect of the present invention, when the thyristor power regulator includes a thyristor and a diode connected in anti-parallel to the thyristor, one of the positive and negative average value circuits is provided. Output is cut off.

[Action]

According to the present invention, when a DC component is generated in the output of the thyristor power regulator, the ignition phase of the antiparallel thyristor is advanced or delayed by an angle corresponding to the DC component, and the control angles of the two are adjusted to be equal. You.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 11 denotes a three-phase AC power supply, and reference numeral 12 denotes a three-phase thyristor power regulator, which comprises an R-phase power regulator 2R, an S-phase power regulator 2S, and a T-phase power regulator 2T. 13 is a three-phase transformer and 14 is a three-phase full-wave rectifier. 21R, 21S, 21T are averaging circuits (integrating circuits), each of which is a current detector (DC
CT) The phase current i _R output by the R-phase power regulator 2R, S-phase power regulator 2S, and T-phase power regulator 2T via 20R, 20S, 20T,
i _S and i _T are input. 22R, 22S and 22T are clamp circuits. _{26 RA, 26 RB, 26 SA} , 26 SB, 26 TA, 26 TB is a phase angle controller, the deviation ε between the aforementioned voltage command V ^* and the voltage feedback v _f, respectively clamp circuits 22R, 22S,
Signals ε _RA , ε _RB , ε _SA , ε _SB , ε corrected with 22T output
_TA, epsilon _TB is input. 23A, 24A, 25A are subtractors, 23B,
24B and 25B are adders. G _RA and G _RB are R phase power regulator 2R
Gate signals for thyristors A and B, G _SA and G _SB are S
Gate signals for the thyristors A and B of the phase power regulator 2S, G _TA and G _TB are gate signals for the thyristors A and B of the T-phase power regulator 2T.

In this configuration, when the control angles α and β of the thyristors A and B forming a pair of the R-phase power regulator 2R, the S-phase power regulator 2S, and the T-phase power regulator 2T are equal, the average value circuits 21R and 21S ,
Since the output of 21T is zero, the deviation ε is input to the phase angle controllers 26 _RA , 26 _RB , 26 _SA , 26 _SB , 26 _TA , and 26 _TB without correction.

Now, the control angle α of the thyristor A constituting the R-phase power regulator 2R is slightly deviated from the control angle β of the thyristor B, and α
If <β, the output of the positive polarity + C
_R appears. Therefore, ε _RA is given by ε, where k is a constant.
-K · C _R next, epsilon _RB is a ε + k · C _R, as shown in FIG. 2, the control angle α increases by equivalent Δθ [k · C _R], the control angle β decreases by Δθ Then, the gate signals _GRA and _GRB are corrected so that the control angles of the thyristors A and B become equal. The same applies when the control angles of the thyristors A and B of the S-phase power regulator 2S and the T-phase power regulator 2T become unequal.

Although the thyristor power regulators 2R to 2T in the above embodiment include thyristors A and B, the present invention can be applied to a case where the thyristors A and the diodes D are provided as shown in FIG.

The clamp circuits 27R, 27S, and 27T in this configuration have a characteristic that the direction in which the control angle α increases, that is, the direction in which the voltage decreases, is positive, and the negative input is cut off. 29R, 29
S and 29T are phase angle controllers, each of which has a gate signal G
_RA, G _SA, sends a G _TA thyristors A of R-phase power regulator 2R, thyristors A of S-phase power regulator 2S, the gate of the thyristor A T-phase power regulator 2T.

〔The invention's effect〕

As described above, the present invention detects the DC component of the current output from the thyristor power regulator from the average value of one cycle and corrects the input of the phase angle controller of each thyristor according to the average value. When the average value becomes a finite value, the control angle of the thyristor is quickly adjusted so that the time integral of the current in the positive half cycle and the time integral in the negative half cycle become equal. Even when the load is a short-circuit load such as an electron beam gun, the transformer can be surely prevented from being demagnetized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the above embodiment, FIG. 3 is a circuit diagram showing a second embodiment of the present invention, FIG. FIG. 5 is a circuit diagram showing a conventional power supply circuit, and FIG. 5 is an output waveform diagram of a thyristor power regulator in the above-described conventional example. 2R to 2T: power regulator, 13: three-phase transformer, 14: full-wave rectifier, 7: load, 9: voltage commander, 10: error amplifier, 12: three-phase thyristor power adjustment Container, 21R ~ 21T ……
Average value circuit, 22R ~ 22T ... Clamp circuit, 26 _RA ~ 26 _TB ... Phase angle controller, 27R ~ 27T ... Clamp circuit, 29R ~ 29T ... Phase angle controller,

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02M 7/00-7/40 G05F 1/455

Claims (2)

(57) [Claims] 1. A power supply apparatus comprising: a thyristor power regulator whose phase is controlled; a transformer for transforming an output of the thyristor power regulator; and a rectifier for converting an output of the transformer to DC and supplying power to a load. A power supply device comprising: an average value circuit for detecting an average value of a current sent by a power regulator; and a feedback control of a firing phase of each thyristor so that an output of the average value circuit becomes zero. 2. A thyristor power regulator comprising a thyristor and a diode connected in anti-parallel to the thyristor, wherein one of the positive and negative outputs of the averaging circuit is cut off. Power supply.