JPH0228610Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention relates to a power supply device for supplying high voltage to an ion implantation device.

(B) Prior Art A power supply device for an ion implantation device needs to output a low ripple DC high voltage with high-speed followability. Therefore, the primary side current of the transformer is switched at high frequency, the boosted output voltage on the secondary side is rectified and supplied to the ion implanter, and the secondary side output voltage is negatively fed back to the primary side to produce an output voltage. Many methods are used to control the temperature at a constant level.

In this system, a self-excited high-frequency oscillation circuit is often used as the circuit for switching the primary current at high frequency because it has a simple circuit configuration and high conversion efficiency.

However, in the ion implantation apparatus, the load is often short-circuited due to discharge, and the self-excited high-frequency oscillation circuit may be destroyed at this time.

Conventionally, the cause of destruction of self-excited high-frequency oscillation circuits has been thought to be surges due to discharge, and various surge countermeasures have been proposed, but no satisfactory results have been obtained.

(c) Purpose of the invention The purpose of this invention is to prevent damage to the self-excited high-frequency oscillation circuit in a power supply device that includes the self-excited high-frequency oscillation circuit.

(d) Structure of the invention The inventors of this invention conducted intensive research to achieve the above purpose, and as a result, they found that the cause of destruction of self-excited high-frequency oscillation circuits is not surges caused by discharge, but rather load short-circuit conditions. When the primary current increases due to negative feedback, the active element of the self-excited high frequency oscillation circuit enters the saturation region and stops oscillating.
It was discovered that this is because the secondary side output decreases and is fed back negative again, which causes the active element to be further maintained in the saturation region, causing an excessive amount of DC current to continuously flow into the self-excited high-frequency oscillation circuit. Ta. Therefore, when the primary current exceeds a predetermined value,
This idea was completed by configuring the circuit to stop the operation of the self-excited high-frequency oscillation circuit and bring the active elements out of the saturation region.

That is, the power supply device for an ion implanter of this invention is provided with a self-excited high frequency oscillation circuit for switching the primary side current on the primary side of the transformer.
An output detection circuit for detecting the secondary side output is provided on the secondary side, and has two inputs, a voltage corresponding to the output voltage of the output detection circuit applied to one side input, and a voltage applied to the other side input. A power supply device for an ion implanter, further comprising a negative feedback circuit that compares the output voltage with a reference voltage set according to a target output voltage and feeds back the output negatively to the self-excited high frequency oscillation circuit. , the coil is electrically connected in series to the primary side of the transformer, and the contact is connected between the other side input and ground, and is activated when the primary side current is equal to or higher than a predetermined value. The present invention is characterized in that a reed switch is further provided for supplying a control signal to the self-excited high-frequency oscillation circuit in the direction of decreasing the primary current.

In the above, the "predetermined value" may be any value that is larger than the maximum value of the primary current when the active element of the self-excited high-frequency oscillation circuit is in a normal operating region. Preferably, the value is the primary current value when the active element enters the saturation region.

In the above, the purpose of "reducing the primary current" is to force the active element of the self-excited high-frequency oscillation circuit out of the saturation region and into the normal operating region or cutoff region. Therefore, at this time, the negative feedback signal from the output detection circuit is not fed back like during normal operation.

(e) Embodiment 1 shown in FIG. 1 is an embodiment of the power supply device for an ion implantation apparatus of this invention.

The commercial frequency AC supplied from the commercial power supply P via the input switch 2 is passed through the rectifier 3 and the smoothing circuit 4.
converted to direct current. Next, the primary side current of the high frequency high voltage transformer 5 passes through the coil 13 of the reed switch.
Hz), the high frequency high voltage transformer 5 is switched.
A high frequency high voltage is induced on the secondary side of the

This high frequency high voltage is converted into a direct current high voltage by a high voltage rectifier 7 and a high voltage smoothing circuit 8, and the output terminal 1
0 to the ion implanter I.

The voltage at the output terminal 10 is divided by the voltage dividing resistor circuit 9 and applied to one side input 12a of the differential amplifier circuit 12. The other side input 12b of the differential amplifier circuit 12
A reference voltage set according to the target output voltage is applied to the output setting variable resistor 11.

The output of the differential amplifier circuit 12 supplies a base current to the high frequency transistor 6 through the resistor 14, but the voltage at one input 12a is higher than the voltage at the other input 1.
When the voltage becomes larger than 2b, the base current is reduced,
When it becomes small, the base current is increased. Therefore, the voltage at the output terminal 10 is controlled to be constant despite fluctuations in the load current.

Since the current value of the coil 13 of the reed switch is set to be sufficiently larger than the normal primary side current value,
Normally not activated. Therefore, the contact 13' of the reed switch is connected between the other input 12b of the differential amplifier circuit 12 and ground, but it does not participate in normal operation at all.

The normal primary current value is, for example, 15A, and the current value of the coil 13 of the reed switch is, for example, 20A.

When the ion implanter discharges and enters a load short-circuit condition, the voltage at the output terminal 10 drops significantly, so the differential amplifier circuit 12 attempts to significantly increase the base current. However, if the base current is increased too much at this time, the high frequency transistor 6 enters the saturation region and becomes continuously energized. Therefore, the high frequency high voltage transformer 5 no longer induces a secondary voltage, and the voltage at the output terminal 10 does not rise even if the discharge of the ion implanter stops, and the high frequency transistor 6 is stuck in a continuously energized state.

Conventionally, this caused the high frequency transistor 6 to continue to be overloaded, leading to its destruction.

However, in this device 1, when the base current is increased excessively and the primary current becomes excessive, a moving current flows through the coil 13 of the reed switch, closing its contact 13'. Then, the differential amplifier circuit 12
Since the other side input 12b of the differential amplifier circuit 12 is grounded, the differential amplifier circuit 12 attempts to set the base current to 0 and the voltage at the output terminal 10 to 0. Therefore, the high frequency transistor 6 comes out of the saturated state and moves toward the cutoff state. Therefore, the primary current decreases,
The closed state of the reed switch contact 13' is no longer maintained and returns to the open state. As a result, the original reference voltage is applied to the other side input 12b of the differential amplifier circuit 12, so that the base current is supplied again. Since the discharge has stopped, the high frequency transistor 6 returns to its normal operating state.

(F) Effects of the invention According to the power supply device for an ion implanter of this invention, the self-excited high frequency oscillation circuit can be prevented from being destroyed and can be restarted automatically.
Safety is high and maintenance management is extremely easy.

Furthermore, since it uses a reed switch,
It has low power consumption and excellent insulation, so there is no need to worry about surge transfer. Furthermore, the configuration is simple, small, and lightweight, and is also suitable in terms of responsiveness.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of one embodiment of the power supply device for an ion implanter of this invention. 1... Power supply device for ion implanter, 5... High frequency high voltage transformer, 6... High frequency transistor, 9
... Voltage dividing circuit, 10 ... Output terminal, 11 ... Output setting variable resistor, 12 ... Differential amplifier circuit, 13
...Reed switch coil, 13'...Reed switch contact, P...Commercial power supply, I...Ion implantation device.

Claims (1)

[Scope of Claim for Utility Model Registration] A self-excited high frequency oscillation circuit for switching the primary current is provided on the primary side of the transformer, an output detection circuit is provided on the secondary side for detecting the secondary side output, 2. a voltage corresponding to the output voltage of the output detection circuit, which has two inputs and is applied to one input of the output detection circuit;
The output is compared with the reference voltage set according to the target output voltage applied to the other side input.
A power supply device for an ion implanter further comprising a negative feedback circuit that provides negative feedback to the self-excited high-frequency oscillation circuit, comprising a coil and a contact, the coil being electrically connected in series to the transformer on a primary side. and its contact is connected between the other side input and ground, and is activated when the primary side current is equal to or higher than a predetermined value to provide a control signal in the direction of reducing the primary side current to the self-excited high frequency oscillation circuit. A power supply device for an ion implanter, further comprising a reed switch.