High voltage amplifier
The high voltage amplifier includes: an input circuit configured to amplify an input signal and connected to a positive-electrode-side level shift circuit and a negative-electrode-side level shift circuit; a high-voltage output circuit including a positive-electrode-side output circuit configured to amplify a signal from the positive-electrode-side level shift circuit and a negative-electrode-side output circuit configured to amplify a signal from the negative-electrode-side level shift circuit; a feedback circuit which feeds back an output signal from the high-voltage output circuit to the input signal; a detection circuit configured to detect currents of the positive-electrode-side and negative-electrode-side output circuits, and an offset adjustment circuit configured to increase an offset amount of the negative-electrode-side level shift circuit to a negative side when a current of the positive-electrode-side output circuit increases, and increase an offset amount of the positive-electrode-side level shift circuit to a positive side when a current of the negative-electrode-side output circuit increases.
1 . A high voltage amplifier comprising:
an input circuit configured to amplify an input signal;
a positive-electrode-side level shift circuit configured to shift an input amplified signal from the input circuit to a positive side;
a negative-electrode-side level shift circuit configured to shift the input amplified signal to a negative side;
a high-voltage output circuit including a positive-electrode-side output circuit configured to amplify a positive-electrode-side level shift signal from the positive-electrode-side level shift circuit and a negative-electrode-side output circuit configured to amplify a negative-electrode-side level shift signal from the negative-electrode-side level shift circuit; and
a feedback circuit configured to feed back a high-voltage output signal from the high-voltage output circuit to the input signal, wherein
the high voltage amplifier comprises
a positive-electrode-side current detection circuit configured to detect a current that flows to the positive-electrode-side output circuit,
a negative-electrode-side current detection circuit configured to detect a current that flows to the negative-electrode-side output circuit,
a positive-electrode-side offset adjustment circuit configured to perform adjustment to increase an offset amount of the positive-electrode-side level shift circuit to a positive side when a negative-electrode-side detected current of the negative-electrode-side current detection circuit increases, and
a negative-electrode-side offset adjustment circuit configured to perform adjustment to increase an offset amount of the negative-electrode-side level shift circuit to a negative side when a positive-electrode-side detected current of the positive-electrode-side current detection circuit increases,
an output terminal to which a load is connected is provided between the positive-electrode-side output circuit and the negative-electrode-side output circuit,
the positive-electrode-side current detection circuit is disposed upstream or downstream of the positive-electrode-side output circuit,
the negative-electrode-side current detection circuit is disposed upstream or downstream of the negative-electrode-side output circuit, and
the positive-electrode-side current detection circuit and the negative-electrode-side current detection circuit are electrically insulated from the positive-electrode-side offset adjustment circuit and the negative-electrode-side offset adjustment circuit.
2 . The high voltage amplifier according to claim 1 , wherein
the positive-electrode-side current detection circuit outputs a positive-electrode-side current detection signal when the positive-electrode-side detected current exceeds a positive-electrode-side limit value,
the negative-electrode-side current detection circuit outputs a negative-electrode-side current detection signal when the negative-electrode-side detected current exceeds a negative-electrode-side limit value,
the positive-electrode-side offset adjustment circuit performs adjustment to increase the offset amount of the positive-electrode-side level shift circuit to a positive side in response to the negative-electrode-side current detection signal, and
the negative-electrode-side offset adjustment circuit performs adjustment to increase the offset amount of the negative-electrode-side level shift circuit to a negative side in response to the positive-electrode-side current detection signal.
3 . The high voltage amplifier according to claim 1 , wherein
the positive-electrode-side offset adjustment circuit performs adjustment to increase the offset amount of the positive-electrode-side level shift circuit to a positive side when at least one of the positive-electrode-side detected current and the negative-electrode-side detected current increases, and
the negative-electrode-side offset adjustment circuit performs adjustment to increase the offset amount of the negative-electrode-side level shift circuit to a negative side when at least one of the positive-electrode-side detected current and the negative-electrode-side detected current increases.
4 . The high voltage amplifier according to claim 3 , wherein
the positive-electrode-side current detection circuit outputs a positive-electrode-side current detection signal when the positive-electrode-side detected current exceeds a positive-electrode-side limit value,
the negative-electrode-side current detection circuit outputs a negative-electrode-side current detection signal when the negative-electrode-side detected current exceeds a negative-electrode-side limit value,
the positive-electrode-side offset adjustment circuit performs adjustment to increase the offset amount of the positive-electrode-side level shift circuit to a positive side in response to at least one of the positive-electrode-side current detection signal and the negative-electrode-side current detection signal, and
the negative-electrode-side offset adjustment circuit performs adjustment to increase the offset amount of the negative-electrode-side level shift circuit to a negative side in response to at least one of the positive-electrode-side current detection signal and the negative-electrode-side current detection signal.
5 . The high voltage amplifier according to claim 3 , wherein
the positive-electrode-side current detection circuit outputs a positive-electrode-side current detection signal to the negative-electrode-side offset adjustment circuit when the positive-electrode-side detected current exceeds a first limit value, and outputs the positive-electrode-side current detection signal to the positive-electrode-side offset adjustment circuit when the positive-electrode-side detected current exceeds a second limit value,
the negative-electrode-side current detection circuit outputs a negative-electrode-side current detection signal to the positive-electrode-side offset adjustment circuit when the negative-electrode-side detected current exceeds the first limit value, and outputs the negative-electrode-side current detection signal to the negative-electrode-side offset adjustment circuit when the negative-electrode-side detected current exceeds the second limit value,
the positive-electrode-side offset adjustment circuit performs adjustment to increase the offset amount of the positive-electrode-side level shift circuit to a positive side in response to at least one of the positive-electrode-side current detection signal and the negative-electrode-side current detection signal, and
the negative-electrode-side offset adjustment circuit performs adjustment to increase the offset amount of the negative-electrode-side level shift circuit to a negative side in response to at least one of the positive-electrode-side current detection signal and the negative-electrode-side current detection signal.
6 . The high voltage amplifier according to claim 1 , wherein
the positive-electrode-side current detection circuit includes a first current detection circuit and a second current detection circuit connected in series,
the negative-electrode-side current detection circuit includes a third current detection circuit and a fourth current detection circuit connected in series,
the positive-electrode-side offset adjustment circuit adjusts the offset amount of the positive-electrode-side level shift circuit based on a first output signal from the first current detection circuit and a third output signal from the third current detection circuit, and
the negative-electrode-side offset adjustment circuit adjusts the offset amount of the negative-electrode-side level shift circuit based on a second output signal from the second current detection circuit and a fourth output signal from the fourth current detection circuit.
7 . The high voltage amplifier according to claim 6 , wherein
the first current detection circuit outputs a first detection signal when a first detected current detected by the first current detection circuit exceeds a first limit value,
the second current detection circuit outputs a second detection signal when a second detected current detected by the second current detection circuit exceeds a second limit value,
the third current detection circuit outputs a third detection signal when a third detected current detected by the third current detection circuit exceeds a third limit value,
the fourth current detection circuit outputs a fourth detection signal when a third detected current detected by the fourth current detection circuit exceeds a fourth limit value,
the positive-electrode-side offset adjustment circuit increases the offset amount of the positive-electrode-side level shift circuit to a positive side in response to the first detection signal or the third detection signal, and
the negative-electrode-side offset adjustment circuit increases the offset amount of the negative-electrode-side level shift circuit to a negative side in response to the second detection signal or the fourth detection signal.
8 . The high voltage amplifier according to claim 1 , wherein
the positive-electrode-side offset adjustment circuit adjusts the offset amount of the positive-electrode-side level shift circuit by changing a gain of the positive-electrode-side level shift circuit, and
the negative-electrode-side offset adjustment circuit adjusts the offset amount of the negative-electrode-side level shift circuit by changing a gain of the negative-electrode-side level shift circuit.
9 . The high voltage amplifier according to claim 1 , wherein
a maximum output voltage from the output terminal is equal to or higher than 200 V and lower than 1000 V.