JP7545370B2 - Power Supplies - Google Patents

Description

The present invention relates to a power supply device that drives a capacitive load.

In recent years, dielectric elastomer actuators have been developed as free-form actuators in various fields such as haptics. Dielectric elastomer actuators are inexpensive to manufacture and are highly efficient at converting electrical energy into mechanical energy.

A dielectric elastomer actuator is a capacitive load with a capacitor structure, which generates a displacement according to the applied voltage. Therefore, it is necessary to apply a voltage according to the displacement to be generated. In other words, driving a capacitive load requires a power supply device that can arbitrarily control the voltage and pass positive and negative currents.

JP 2004-46595 A

The power supply device 10 shown in FIG. 4 is a power supply device with a bridge type output stage that includes a DCDC converter 11 and a DCAC inverter 12. As described above, the power supply device 10 with a bridge type output stage can supply both positive and negative currents, and therefore can ideally drive the capacitive load CL. However, since the DCDC converter 11 and the DCAC inverter 12 are controlled separately, many components such as a control IC are required, and the control is complicated. Furthermore, expensive switching elements and gate drivers are required, which increases costs.

Patent Document 1 proposes a power supply device in which a discharge-type low-speed amplifier and a charge-type high-speed amplifier that operate as voltage followers have their input terminals connected to each other and their output terminals connected to each other. This power supply device operates either the discharge-type low-speed amplifier or the charge-type high-speed amplifier in response to load fluctuations to charge and discharge. Therefore, although this power supply device can pass positive and negative currents, it does not arbitrarily control the voltage.

The present invention was made in consideration of these problems, and its purpose is to provide an inexpensive power supply device that can arbitrarily control the voltage and can supply positive and negative currents.

In order to achieve the above object, the power supply device according to the present invention is configured as follows.
The power supply device of the present invention is a power supply device that drives a capacitive load with an output voltage corresponding to an output voltage command value, and is characterized in comprising: a voltage detection circuit that outputs a detection voltage that is a detection value of the output voltage; a charge supply unit that functions as a voltage source when the output voltage rises and supplies charge to the capacitive load by negative feedback controlling the output voltage so that the detection voltage to which the output voltage command value has been added becomes equal to a first reference voltage; and a charge extraction unit that functions as a current source when the output voltage falls and negative feedback controls an extraction current that extracts charge from the capacitive load so that the detection voltage to which the output voltage command value has been added becomes equal to a second reference voltage that is higher than the first reference voltage.

The power supply device of the present invention applies a single voltage, positive or negative, to the capacitive load. In the case of a positive voltage output power supply, an inexpensive DC-DC converter that operates only in one quadrant and can only discharge an output current can be used as the charge supply unit. This has the effect of providing an inexpensive power supply device that can arbitrarily control the voltage required to drive a capacitive load and can pass positive and negative currents.

1 is a block diagram showing a configuration of an embodiment of a power supply device according to the present invention; 2 is a waveform diagram of each part when a capacitive load is driven only by the charge supply part shown in FIG. 1 . 2 is a waveform diagram of each part when a capacitive load is driven by the power supply device shown in FIG. 1. FIG. 1 is a block diagram showing a configuration of a conventional power supply device.

A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

Referring to FIG. 1, the power supply device 1 of this embodiment includes a charge supply unit 2 and a charge extraction unit 3 that functions as a current source that extracts charge from the capacitive load CL, and the voltage applied to the capacitive load CL is a positive or negative single voltage, and any voltage (DC, sine wave, square wave, etc.) is applied.

The charge supply unit 2 is a DC-DC converter that functions as a voltage source that supplies charge to the capacitive load CL, converting the input voltage Vin from the DC power source E into an output voltage Vout and supplying it to the capacitive load CL. Note that while the charge supply unit 2 shown in FIG. 1 is an example configured as a flyback type switching power supply, it may be configured in other ways, such as a forward type.

The charge supply unit 2 includes a transformer 21, a switching element 22, an output rectifier smoothing circuit 23, a voltage detection circuit 24, a control circuit 25, and a driver 26.

The transformer 21 has a primary winding and a secondary winding, and the polarity of the primary winding and the polarity of the secondary winding are set to be opposite. The primary winding of the transformer 21 is connected between the positive terminal of the DC power source E and the switching element 22. As a result, the DC power source E is applied to the primary winding of the transformer 21 as the input voltage Vin.

The switching element 22 is, for example, an N-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The drain of the switching element 22 is connected to the primary winding of the transformer 21, and the source of the switching element 22 is connected to the ground terminal. As a result, the input voltage Vin is output to the secondary winding of the transformer 21 during the off period by the on/off operation of the switching element 22 connected via the primary winding of the transformer 21.

The output rectifier smoothing circuit 23 includes a rectifier diode D1 and an output capacitor C1, and the output capacitor C1 is connected between both terminals of the secondary winding of the transformer 21 via the rectifier diode D1. As a result, the AC voltage induced in the secondary winding of the transformer 21 is rectified and smoothed by the output rectifier smoothing circuit 23 and supplied to the capacitive load CL as a DC output voltage Vout.

The voltage detection circuit 24 includes resistors R1 and R2 connected in series between both terminals of the output capacitor C1, and outputs the detection voltage Vdet at the connection point between resistors R1 and R2 to the control circuit 25 as a voltage detection signal of the output voltage Vout.

The detection voltage Vdet is configured to have the output voltage command value Vcont added to it via resistor R3 and input to the control circuit 25. That is, the control circuit 25 adds the output voltage command value Vcont to the detection voltage Vdet and performs negative feedback control to generate an arbitrary output voltage Vout according to the output voltage command value Vcont.

The control circuit 25 includes an error amplifier 27, a comparator 28, and a triangular wave oscillator 29. The inverting input terminal (-) of the error amplifier 27 receives the detection voltage Vdet to which the output voltage command value Vcont has been added, and the non-inverting input terminal (+) of the error amplifier 27 receives the first reference voltage Vref1. The error amplifier 27 outputs an error signal obtained by amplifying the error voltage between the detection voltage Vdet and the first reference voltage Vref1 to the non-inverting input terminal (+) of the comparator 28.

A triangular wave signal from a triangular wave oscillator 29 is input to the inverting input terminal (-) of the comparator 28. The comparator 28 then outputs the result of comparing the error signal from the error amplifier 27 with the triangular wave signal from the triangular wave oscillator 29. The output of the comparator 28 becomes a control signal that controls the on/off of the switching element 22, and is input to the gate of the switching element 22 via the driver 26.

The charge supply unit 2 has a diode-configured output stage, so in the case of a positive voltage output power supply, it can only discharge output current. Therefore, when driving the capacitive load CL using only the charge supply unit 2, it can drive without problems when the voltage rises, but when the voltage drops, it cannot extract the charge accumulated in the capacitive load CL and must rely on natural discharge.

Figure 2 is a waveform diagram of each part when the capacitive load CL is driven only by the charge supply unit 2, where (a) shows the output voltage command value Vcont, (b) shows the output voltage Vout, and (c) shows the detection voltage Vdet. When the capacitive load CL is driven only by the charge supply unit 2, the charge supply unit 2 cannot extract the charge charged in the capacitive load CL when driving a capacitive load CL with a large capacity or when driving at a high frequency. Therefore, as shown in Figures 2(a) and (b), when the output voltage command value Vcont drops, the output voltage Vout cannot be lowered accordingly, and an output voltage Vout similar to the output voltage command value Vcont cannot be obtained. As a countermeasure, the voltage can be lowered by inserting a load resistor in parallel with the capacitive load CL, but this results in unnecessary power consumption.

In this way, when the output voltage command value Vcont (output voltage Vout) drops, the negative feedback control is lost, and the detection voltage Vdet rises without being controlled to the value of the first reference voltage Vref1, as shown in FIG. 2(c). Therefore, the power supply device 1 of this embodiment is equipped with a charge extraction unit 3 that operates when the detection voltage Vdet rises above the first reference voltage Vref1 and functions as a current source that extracts charge from the capacitive load CL.

The charge extraction unit 3 includes a variable impedance element 31, a resistor R4, an error amplifier 32, and an operational amplifier 33. A series circuit consisting of the variable impedance element 31 and resistor R4 is connected in parallel with the capacitive load CL. In this embodiment, the variable impedance element 31 is configured as an N-type MOSFET, but the variable impedance element 31 may be an NPN-type bipolar transistor, etc.

The detection voltage Vdet to which the output voltage command value Vcont has been added is input to the non-inverting input terminal (+) of the error amplifier 32, and the second reference voltage Vref2 is input to the inverting input terminal (-) of the error amplifier 32. The second reference voltage Vref2 is set to a value higher than the first reference voltage Vref1, which is the reference for the error voltage with respect to the detection voltage Vdet, in the charge supply unit 2. The error amplifier 32 outputs an error signal obtained by amplifying the error voltage between the detection voltage Vdet and the second reference voltage Vref2 to the non-inverting input terminal (+) of the operational amplifier 33.

The inverting input terminal (-) of the operational amplifier 33 is connected to the connection point between the variable impedance element 31 and resistor R4, and receives a current detection signal obtained by converting the pull-out current I_dscg flowing through the variable impedance element 31 into a voltage by resistor R4. The operational amplifier 33 then outputs the result of comparing the error signal from the error amplifier 32 with the current detection signal. The output of the operational amplifier 33 becomes a control signal that controls the current of the variable impedance element 31, and is input to the gate of the variable impedance element 31.

Figure 3 is a waveform diagram of each part when a capacitive load CL is driven by a power supply device 1 equipped with a charge supply unit 2 and a charge extraction unit 3, where (a) shows the output voltage command value Vcont, (b) shows the output voltage Vout, (c) shows the extraction current I_dscg, and (d) shows the detection voltage Vdet. When a capacitive load CL is driven by a power supply device 1 equipped with a charge supply unit 2 and a charge extraction unit 3, the charge stored in the capacitive load CL can be extracted by the charge extraction unit 3 when driving a capacitive load CL with a large capacity or when driving at a high frequency. Therefore, as shown in Figures 3(a) and (b), when the output voltage command value Vcont drops, the output voltage Vout can be lowered accordingly.

With the above configuration, the charge supply unit 2 monitors the detection voltage Vdet to which the output voltage command value Vcont is added using the first reference voltage Vref1, and when the voltage rises (period X, when the output voltage Vout is lower than the output voltage command value Vcont), it operates as a voltage source using the first reference voltage Vref1 to supply charge to the capacitive load CL. That is, when the voltage rises, the charge supply unit 2 negatively feedback controls the output voltage Vout so that the detection voltage Vdet is equal to the first reference voltage Vref1, as shown in FIG. 3(d), to supply charge to the capacitive load CL. At this time, since the detection voltage Vdet is lower than the second reference voltage Vref2, the charge extraction unit 3 does not operate, as shown in FIG. 3(c).

The charge extraction unit 3 monitors the detection voltage Vdet to which the output voltage command value Vcont has been added using a second reference voltage Vref2 higher than the first reference voltage Vref1, and when the voltage drops (period Y, when the output voltage Vout is higher than the output voltage command value Vcont), it operates as a current source using the second reference voltage Vref2 to extract charge from the capacitive load CL. That is, when the voltage drops, the charge extraction unit 3 performs negative feedback control of the extraction current I_dscg so that the detection voltage Vdet becomes equal to the second reference voltage Vref2, as shown in Figures 3(c) and (d), to extract charge from the capacitive load CL. At this time, the detection voltage Vdet is higher than the first reference voltage Vref1, so the charge supply unit 2 does not operate.

As a result, when the voltage rises, the charge supply unit 2 is negatively feedback controlled by the first reference voltage Vref1, and when the voltage falls, the charge extraction unit 3 is negatively feedback controlled by the second reference voltage Vref2, and the operation of the charge supply unit 2 and the operation of the charge extraction unit 3 are automatically switched. Note that since the second reference voltage Vref2 of the charge extraction unit 3 is greater than the first reference voltage Vref1 of the charge supply unit 2, when switching between the operation of the charge supply unit 2 and the charge extraction unit 3, there is hysteresis and the charge supply unit 2 and the charge extraction unit 3 do not operate simultaneously, making it less susceptible to noise malfunctions.

The smaller the difference between the second reference voltage Vref2 and the first reference voltage Vref1, the smoother the switching between the operation of the charge supply unit 2 and the operation of the charge extraction unit 3. However, the smaller the difference between the second reference voltage Vref2 and the first reference voltage Vref1, the higher the risk of malfunction due to noise, etc. Therefore, taking these factors into consideration, the values of the second reference voltage Vref2 and the first reference voltage Vref1 are set appropriately.

As described above, this embodiment provides a power supply device 1 that drives a capacitive load CL with an output voltage Vout that corresponds to an output voltage command value Vcont, and includes a voltage detection circuit 24 that outputs a detection voltage Vdet that is a detection value of the output voltage Vout, a charge supply unit 2 that functions as a voltage source when the output voltage command value Vcont rises and supplies charge to the capacitive load CL by negative feedback controlling the output voltage Vout so that the detection voltage Vdet to which the output voltage command value Vcont has been added becomes equal to the first reference voltage Vref1, and a charge extraction unit 3 that functions as a current source when the output voltage command value Vcont falls and performs negative feedback control of an extraction current I_dscg that extracts charge from the capacitive load CL so that the detection voltage Vdet to which the output voltage command value Vcont has been added becomes equal to a second reference voltage Vref2 that is higher than the first reference voltage Vref1.
With this configuration, when the output voltage Vout applied to the capacitive load CL is a single voltage, either positive or negative, and the power supply is a positive voltage output power supply, an inexpensive DCDC converter that operates only in one quadrant and can only discharge an output current can be used as the charge supply unit 2. Therefore, it is possible to provide an inexpensive power supply device that can arbitrarily control the voltage required to drive the capacitive load CL and can pass positive and negative currents.

Furthermore, in this embodiment, the charge supply unit 2 includes an error amplifier 27 for charge supply (error amplifier for charge supply) in which the detection voltage Vdet to which the output voltage command value Vcont has been added is input to an inverting input terminal (-) and a first reference voltage Vref1 is input to a non-inverting input terminal (+), and negative feedback controls the output voltage based on an error signal (error signal for charge supply) output from the error amplifier 27, and the charge extraction unit 3 includes an error amplifier 32 (error amplifier for charge extraction) in which the detection voltage Vdet to which the output voltage command value Vcont has been added is input to a non-inverting input terminal (+) and a second reference voltage Vref2 is input to an inverting input terminal (-), and negative feedback controls the extraction current I_dscg based on the error signal (error signal for charge extraction) output from the error amplifier 32.
With this configuration, the charge supply unit 2 and the charge extraction unit 3 do not operate simultaneously, and the operation of the charge supply unit 2 and the operation of the charge extraction unit 3 are automatically switched, making it possible to make the output voltage Vout follow the output voltage command value Vcont even when driving a capacitive load CL with a large capacity or when driving at a high frequency.

It is clear that the present invention is not limited to the above-described embodiments, and that each embodiment may be modified as appropriate within the scope of the technical concept of the present invention. Furthermore, the number, position, shape, etc. of the above-described components are not limited to the above-described embodiments, and may be any number, position, shape, etc. that is suitable for implementing the present invention. The same components are denoted by the same reference numerals in each drawing.

1, 10 Power supply device 2 Charge supply section 3 Charge extraction section 11 DCDC converter 12 DCAC inverter 21 Transformer 22 Switching element 23 Output rectifier smoothing circuit 24 Voltage detection circuit 25 Control circuit 26 Driver 27 Error amplifier 28 Comparator 29 Triangular wave oscillator 31 Variable impedance element 32 Error amplifier 33 Operational amplifier C1 Output capacitor CL Capacitive load D1 Rectifier diode E DC power supplies R1 to R4 Resistor

Claims (3)

A power supply device that drives a capacitive load with an output voltage according to an output voltage command value,
a voltage detection circuit that outputs a detection voltage that is a detection value of the output voltage;
a charge supply unit that functions as a voltage source when the output voltage increases and that performs negative feedback control of the output voltage so that the detection voltage to which the output voltage command value is added becomes equal to a first reference voltage, and supplies charge to the capacitive load;
a charge extraction unit that functions as a current source when the output voltage drops, and performs negative feedback control on an extraction current that extracts charge from the capacitive load so that the detection voltage to which the output voltage command value is added becomes equal to a second reference voltage that is higher than the first reference voltage. the charge supply unit includes a charge supply error amplifier, the detection voltage to which the output voltage command value has been added is input to an inverting input terminal, and the first reference voltage is input to a non-inverting input terminal, and performs negative feedback control of the output voltage based on a charge supply error signal output from the charge supply error amplifier;
2. The power supply device according to claim 1, wherein the charge extraction unit includes an error amplifier for charge extraction, the detection voltage to which the output voltage command value has been added being input to a non-inverting input terminal, and the second reference voltage being input to an inverting input terminal, and negative feedback controls the extraction current based on a charge extraction error signal output from the error amplifier for charge extraction. The power supply device according to claim 1 or 2, characterized in that the charge supply unit is a DC-DC converter that operates only in one quadrant.

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