JP3539129B2 - Capacitor charging device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a capacitor charging device that periodically charges a power capacitor provided in a pulse power supply or the like to a set voltage.
[0002]
[Prior art]
Some pulse power supplies for pulsed laser excitation, pulsed plasma generation, pulse denitration equipment, and the like include a combination of a saturable transformer or a saturable reactor serving as a semiconductor switch and a magnetic switch.
[0003]
This pulse power supply has, for example, the configuration shown in FIG. The capacitor C ₀ is initially charged by the high-voltage charger HDC, and a discharge current is supplied from the capacitor C ₀ to the primary side of the saturable transformer ST by turning on the semiconductor switch SW. in pulse compression, boosted by the voltage doubler generating circuit LC by LC inversion to generate ultrashort pulses by further pulse compression saturable reactors SI ₁ to peaking capacitor C _P and the laser oscillator LH.
[0004]
Here, high-pressure charging device HDC for initial charging of the capacitor C _0, the need to charge the capacitor C ₀ at a high repetition in accordance with the pulse current supply of the high repetition of the laser oscillator LH (for example, 600 pulses / sec) is there. Further, since the voltage of the capacitor C ₀ is a direct effect on output, those high charge voltage accuracy is required.
[0005]
A conventional high-voltage charger for this purpose has a configuration shown in FIG. A DC power supply 1, which is a rectifier or the like that obtains DC from an AC power supply, constitutes a DC power supply for the inverters 2 and 3 that are converted to a voltage form.
[0006]
The inverters 2 and 3 have a configuration in which semiconductor elements such as power transistors and IGBTs and GTOs are bridge-connected as switches S1 to S4, and pulse-width controlled (or pulse-width modulated) AC power is supplied to a resonance capacitor C and a resonance reactor. Output with the resonance frequency determined by L.
[0007]
The output transformers 4 and 5 respectively take out the AC outputs from the inverters 2 and 3 at a fixed ratio. Rectifier circuits 6 and 7 is constituted by a diode bridge connection, and each AC input the output of the transformer 4 and 5 performs the full-wave rectification to obtain a charge output capacitor C ₀ are connected in parallel to the rectifier output.
[0008]
The inverter 2 is for initial charging of the capacitor C _0, the inverter 3 is for fine adjustment charging voltage. These inverters 2 and 3, as shown in FIG. 6, charged to near the set voltage of the capacitor C ₀ being operated both in the initial charging of the capacitor C _0, to set the voltage Thereafter by only the fine adjustment inverter 3 Charge the battery gradually and accurately. Then, the operation of the inverter 3 also is stopped when the charging voltage of the capacitor C ₀ has reached the set voltage.
[0009]
For this reason, the fine-tuning inverter 3 is designed so that the switching frequency is higher and the charging voltage per operation is lower than the initial charging inverter 2.
[0010]
[Problems to be solved by the invention]
In the conventional configuration, in order to charge the capacitor C ₀ to a set voltage, the voltage of the capacitor C ₀ is detected by a voltage detector 8 such as a resistor divider, and the detected voltage is taken into a control circuit 9 and compared with the set voltage. By this coincidence, the control circuit 9 performs the operation stop control of the inverter 3.
[0011]
The charging device HDC and the capacitor C ₀ are connected by the connector 10, and when the connector 10 is left disconnected for disconnection or disconnection for maintenance / inspection of the device or when disconnection occurs, when the operation is started in that state, The inverters 2 and 3 start operating in a no-load state.
[0012]
At this time, the output voltage of the charging device HDC rapidly increases with a large slope (dv / dt). The voltage detector 8 and the control circuit 9 have a detection delay with respect to this sudden increase in voltage, and there is a delay until the inverter operation stop control by overvoltage detection.
[0013]
For this reason, when the charging device HDC is started in a no-load state, the output voltage of the charging device suddenly rises above the overvoltage setting voltage level higher than the charging setting voltage due to the voltage detection delay and the delay of the inverter operation stop control. As a result, the rectifier circuits 6 and 7 and the circuit elements of the inverters 2 and 3 may be damaged by overvoltage.
[0014]
An object of the present invention is to provide a charging device that can reliably protect a circuit from overvoltage even when started up in a no-load state.
[0015]
[Means for Solving the Problems]
The present invention is to detect the no-load state early by lowering the overvoltage detection level initially with respect to the sudden rise in voltage when the charging device is started in the no-load state, or to output the voltage during the test operation of the inverter. The circuit is surely protected from overvoltage by detecting a no-load state due to the abnormality described above, and is characterized by the following configuration.
[0016]
(First invention)
The AC output of the LC resonant inverter is rectified, and a power capacitor connected to the rectified output terminal via a connector is charged with the rectified output . When the charged voltage reaches a set value or exceeds an overvoltage detection level. In the capacitor charging device in which the control circuit stops the operation of the inverter when the
Wherein the control circuit, wherein the inverter startup leave low overvoltage detection level, by raising to a final of the overvoltage detection level over time, early overvoltage by no-load state occurs in a disconnected or disconnection of the connector And an overvoltage protection circuit for detecting the overvoltage.
[0017]
(Second invention)
The AC output of the LC resonant inverter is rectified, and a power capacitor connected to the rectified output terminal via a connector is charged with the rectified output . When the charged voltage reaches a set value or exceeds an overvoltage detection level. In the capacitor charging device in which the control circuit stops the operation of the inverter when the
The control circuit includes an overvoltage protection circuit that performs a test operation of the inverter for a short period of time and detects an overvoltage due to a no-load state caused by disconnection or disconnection of the connector from an abnormality of a charging voltage in the test operation. It is characterized by.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention. This figure differs from FIG. 5 in the control circuit 9A. The control circuit 9A takes in the detected voltage from the voltage detector 8 into two comparators CMP1 and CMP2 as a comparison input voltage.
[0019]
The comparator CMP1 detects that the comparison reference voltage corresponding to the charging setting voltage of the capacitor C ₀ is given from the voltage setter VR, the charging voltage of the capacitor C ₀ has reached the set voltage.
[0020]
The comparator CMP2 receives a comparison reference voltage corresponding to the overvoltage set value from the overvoltage pattern generator PG, and detects that the output voltage of the charging device has exceeded the overvoltage set value.
[0021]
Start and stop controller CON performs startup control of the inverter 2, 3 start command, stopping the operation control of the inverter 3 when the comparator CMP1 detects that the capacitor C ₀ is charged to the comparison reference voltage. Further, when the comparator CMP2 detects an overvoltage, the operation stop control of the inverters 2 and 3 is performed.
[0022]
The overvoltage pattern generator PG is activated when the activation / stop control unit CON activates the inverters 2 and 3 to generate an overvoltage pattern, and forms an overvoltage protection circuit together with the comparator CMP2 and the activation / stop control unit CON.
[0023]
In this overvoltage pattern, as shown in FIG. 2A, the overvoltage detection set value increases with time from the start of the inverters 2 and 3, and is maintained at the final set value when it reaches the final set value. . The overvoltage pattern, for example, as shown, is a pattern of raised only high level constant width than the charge characteristics at the initial charging of the capacitor C _0. Further, the overvoltage pattern may increase exponentially.
[0024]
The overvoltage pattern generator PG can be realized by an analog circuit using a CR time constant circuit or the like or a digital circuit using a counter or the like.
[0025]
According to the present embodiment, the overvoltage detection level is initially set low, and is raised to the regular overvoltage detection level with time. Thereby, when the inverters 2 and 3 are started in a no-load state due to disconnection or disconnection of the connector 10 between the charging device HDC and the capacitor C ₀ , the overvoltage detection delay is reduced with respect to a sharp rise in the output. Thus, stop control of the inverters 2 and 3 can be obtained.
[0026]
These relationships are as shown in FIG. 3, the output voltage to start the inverter 2 without load rises rapidly as characteristic A, it exceeds the overvoltage detection level at an early time t _1, the state Can stop the inverter with the characteristic B delayed by a certain time T _D even if there is a detection delay or a delay in the inverter stop control. In the time t _2, the actual output voltage (characteristic A) to stop the inverter 2 and 3 at the maximum value following the state of the overvoltage, to protect the circuit of the charging device HDC from overvoltage.
[0027]
FIG. 2B shows an overvoltage detection pattern for explaining another embodiment of the present invention. Before starting the inverters 2 and 3, only the inverter 3 for fine adjustment is subjected to a test operation for a short time, and then the parallel operation of the inverters 2 and 3 and the independent operation of the inverter 3 are performed as in the related art.
[0028]
In this operation pattern, the overvoltage pattern generator PG generates a low overvoltage level in accordance with the output voltage of the inverter 3 for the test operation of the fine adjustment inverter 3.
[0029]
Thus, if the fine adjustment inverter 3 is in a no-load state during the test operation, the output voltage rises abnormally, and this rise in output voltage can be detected as an overvoltage.
[0030]
That is, in the present embodiment, the inverter for fine adjustment is experimentally operated before the start of the inverters 2 and 3, and when the output voltage becomes abnormally high in this operation, it is detected as a no-load state. The abnormal voltage at this time does not exceed the overvoltage level of the circuit, and the detection can detect the abnormal voltage and stop the restart of the inverters 2 and 3 to protect the circuit.
[0031]
In the above embodiments, the case where the capacitor C ₀ is applied to the device that performs the initial charging and the fine adjustment charging by the inverters 2 and 3 is shown. It has the same effect.
[0032]
【The invention's effect】
As described above, according to the present invention, it is possible to early detect the no-load state by initially lowering the overvoltage detection level with respect to a sharp rise in voltage when starting in the no-load state, or in the test operation of the inverter. Since a no-load state is detected due to an abnormal output voltage, the circuit can be reliably protected from overvoltage even if the connector is forgotten or disconnected.
[Brief description of the drawings]
FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention.
FIG. 2 is an overvoltage detection pattern in the embodiment.
FIG. 3 is a time relationship of overvoltage detection in the embodiment.
FIG. 4 is an example of a pulse power supply.
FIG. 5 shows a conventional circuit example.
FIG. 6 shows charging characteristics of a capacitor C ₀ .
[Explanation of symbols]
2 ... Inverter for initial charging 3 ... Inverter for fine adjustment 6, 7 ... Rectifier 8 ... Voltage detector 9, 9A ... Control circuit CMP1, CMP2 ... Comparator PG ... Overvoltage pattern generator CON ... Start / stop control unit

Claims (2)

The AC output of the LC resonant inverter is rectified, and a power capacitor connected to the rectified output terminal via a connector is charged with the rectified output . When the charged voltage reaches a set value or exceeds an overvoltage detection level. In the capacitor charging device in which the control circuit stops the operation of the inverter when the
Wherein the control circuit, wherein the inverter startup leave low overvoltage detection level, by raising to a final of the overvoltage detection level over time, early overvoltage by no-load state occurs in a disconnected or disconnection of the connector A charging device for a capacitor, comprising: an overvoltage protection circuit for detecting an overvoltage. The AC output of the LC resonant inverter is rectified, and a power capacitor connected to the rectified output terminal via a connector is charged with the rectified output . When the charged voltage reaches a set value or exceeds an overvoltage detection level. In the capacitor charging device in which the control circuit stops the operation of the inverter when the
The control circuit includes an overvoltage protection circuit that performs a test operation of the inverter for a short period of time and detects an overvoltage due to a no-load state caused by disconnection or disconnection of the connector from an abnormality of a charging voltage in the test operation. A charging device for a capacitor, characterized in that:

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