Power supply noise reduction circuit and power supply noise reduction method
View Patent ↗To provide a power supply noise reduction circuit and a power supply noise reduction method that do not require circuit elements to be increased in size and do not cause voltage drop in a power supply voltage. A power supply noise reduction circuit 10 that reduces noise included in a constant voltage output that is output from a power supply 2 to a load includes a first resistor 20 that is inserted into a power supply line L 1 extending from the power supply 2 to the load, a filter 31 that is coupled to a load terminal of the first resistor 20 and outputs a first voltage that is obtained by reducing the noise from the constant voltage output, and a unity gain amplifier 32 that drives the first voltage output from the filter 31 and outputs the driven first voltage to the load terminal of the first resistor 20.
1. A power supply noise reduction circuit that reduces noise included in a constant voltage output that is output from a power supply to a load, the power supply noise reduction circuit comprising:
a first resistor that is inserted into a power supply line extending from the power supply to the load;
a low-pass filter that is connected to a load terminal of the first resistor and outputs a first voltage that is obtained by reducing the noise from the constant voltage output, the low-pass filter including a second resistor and a capacitor that are connected in series and also including a bypass line for bypassing the second resistor; and
a unity gain amplifier that drives the first voltage output from the low-pass filter and outputs the driven first voltage to the load terminal of the first resistor,
wherein the low-pass filter is configured to connect the bypass line and bypass the second resistor through a low-pass filter switching unit before the power supply is turned on, wherein the capacitor is charged by turning on the power supply after the bypass line is switched to bypass the second resistor, and wherein after the power supply is turned on and the capacitor is charged the low-pass filter is configured to switch the bypass line to un-bypass the second resistor.
2. The power supply noise reduction circuit according to claim 1 , comprising the filter switching unit that switches the bypass line for bypassing the second resistor before the power supply is turned on.
3. The power supply noise reduction circuit according to claim 1 , comprising a third resistor that decreases an input voltage to the unity gain amplifier through voltage division with the second resistor.
4. The power supply noise reduction circuit according to claim 1 , comprising an amplifier switching unit that switches an output line extending from the unity gain amplifier to a load terminal of the second first resistor on and off.
5. The power supply noise reduction circuit according to claim 3 , wherein the third resistor is coupled between an input terminal of the unity gain amplifier and a ground terminal of the capacitor.
6. A method of power supply noise reduction for reducing noise included in a constant voltage output that is output from a power supply to a load using a power supply noise reduction circuit, wherein the power supply noise reduction circuit comprises:
a first resistor that is inserted into a power supply line extending from the power supply to the load;
a low-pass filter that is connected to a load terminal of the first resistor and outputs a first voltage that is obtained by reducing the noise from the constant voltage output, the low-pass filter including a second resistor and a capacitor that are connected in series;
a unity gain amplifier that drives the first voltage output from the low-pass filter and outputs the driven voltage to the load terminal of the first resistor; and
a filter switching unit that switches a bypass line for bypassing the second resistor, wherein the method comprises:
a bypassing step of switching the bypass line to bypass the second resistor through the low-pass filter switching unit before the power supply is turned on;
a charging step of charging the capacitor by turning on the power supply after the bypassing step; and
a connecting step of switching the bypass line to connect the second resistor through the filter switching unit after the charging step.
7. The method according to claim 6 , wherein the power supply noise reduction circuit comprises an amplifier switching unit that switches an output line extending from the unity gain amplifier to the load terminal of the first resistor on and off;
the output line is switched off by the amplifier switching unit in the bypassing step; and
the output line is switched on by the amplifier switching witching unit in the connecting step.