AC-VOLTAGE SENSOR CIRCUIT, INVERTER CIRCUIT, AND POWER SUPPLY CIRCUIT

An AC-voltage sensor circuit is connected to an AC output unit of an inverter circuit. A control circuit and the inverter circuit are isolation-connected. The AC-voltage sensor circuit includes a sense-signal isolation circuit. The inverter circuit and the control circuit are isolation-connected together by the AC-voltage sensor circuit. The AC output unit includes a first line and a second line that are power supply lines. The inverter circuit includes a reference-voltage node. The AC-voltage sensor circuit is configured to output a signal indicating a voltage difference between a “voltage of the first line for the reference-voltage node” and a “voltage of the second line for the reference-voltage node”.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Application JP2022-087815, the content of which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The following disclosure relates to an AC-voltage sensor circuit, an inverter circuit, and a power supply circuit.

2. Description of the Related Art

A power supply circuit from which alternating current (AC) is output requires a sensor circuit for detecting AC voltage that is output from the power supply circuit. Japanese Unexamined Patent Application Publication No. 2018-046622 discloses one example.

SUMMARY OF THE INVENTION

However, even using such an AC-voltage sensor circuit disclosed in Japanese Unexamined Patent Application Publication No. 2018-046622 still has room for improvement.

One aspect of the present disclosure aims to offer an AC-voltage sensor circuit, an inverter circuit, and a power supply circuit that are simpler in circuit configuration than before.

To solve the above problem, an AC-voltage sensor circuit according to one aspect of the present disclosure is an AC-voltage sensor circuit connected to an AC output unit of an inverter circuit. A control circuit and the inverter circuit are isolation-connected. The AC-voltage sensor circuit includes a sense-signal isolation circuit. The inverter circuit and the control circuit are isolation-connected together by the AC-voltage sensor circuit. The AC output unit includes a first line and a second line that are power supply lines. The inverter circuit includes a reference-voltage node. The AC-voltage sensor circuit is configured to output a signal indicating the voltage difference between the “voltage of the first line for the reference-voltage node” and the “voltage of the second line for the reference-voltage node”.

The aspect of the present disclosure can offer an AC-voltage sensor circuit, an inverter circuit, and a power supply circuit that are simpler in circuit configuration than before.

DETAILED DESCRIPTION OF THE INVENTION

Background and Problem of AC-Voltage Sensor Circuit Used in Power Supply Circuit

Power supply circuits that have been increasingly required to be miniaturized require their sensor circuits to be simplified. In particular, the sensor circuit of an inverter circuit from which AC voltage is output tends to be complicated unfortunately. This preferred embodiment discloses one example of simplifying an AC-voltage sensor circuit.

For the sake of document simplification, an “AC-voltage sensor circuit ACS1” for instance will be also expressed merely as “ACS1”.

Main Configuration of AC-Voltage Sensor Circuit ACS1that can Sense AC Voltage Differential

FIG.1illustrates the circuit configuration of a power supply circuit PS1including the AC-voltage sensor circuit ACS1according to one preferred embodiment of the present invention.FIG.1illustrates an inverter circuit INV1connected to an AC output unit ACO1, and the AC-voltage sensor circuit ACS1connected to ACO1. ACO1, which is drawn inside INV1via a wire, is included in INV1in circuit view (i.e., substantially). As illustrated in the drawing, PS1includes ACS1, a control circuit CNT1, a DC-DC converter DDC1, a direct current (DC) input unit DCI1, a first gate driving circuit GDR1, a second gate driving circuit GDR2, and an isolated circuit ISOC1.

The control circuit CNT1is a circuit that controls INV1. The control circuit CNT1is isolation-connected to INV1. In more detail, INV1and CNT1are isolation-connected together by ACS1.

ACS1includes a sense-signal isolation circuit in order to transmit a sense signal with isolation. Further, ACO1includes a first line LIN1and a second line LIN2each of which is a power supply line. LIN1and LIN2are connected to INV1. INV1includes a reference-voltage node GND1.

ACS1is configured to output a signal indicating the voltage difference between the “voltage of LIN1for GND1” and the “voltage of LIN2for GND1”. The signal indicating the voltage difference is input to CNT1. CNT1includes a microcontroller and can receive an analog signal or digital signal and can output an analog signal or digital signal. The entire power supply circuit PS1can be thus controlled.

Isolation connection is connection that allows a signal or electric power to be transmitted though electrical connection is not established. Examples include an optical isolation circuit using a photocoupler, an isolated circuit using an electrostatic-capacitance coupling, and a transformer (transformation) circuit using magnetic coupling. These circuits can prevent leakage current, avoid an electric shock, prevent noise propagation and offer other isolation benefits.

ACS1outputs a signal indicating the difference voltage (differential voltage) between the voltage of LIN1and the voltage of LIN2. The signal indicating the difference voltage can be transmitted to CNT1by the sense-signal isolation circuit of ACS1with isolation. Types of the signal indicating the voltage difference include an analog signal and a digital signal. An example of the digital signal is a delta-sigma modulation signal.

Connection Configuration of AC-Voltage Differential Sensor Including Reference-Voltage Node GND1

As illustrated inFIG.1, ACS1includes a first resistor RS1, a second resistor RS2, a third resistor RS3, a fourth resistor RS4, and an isolation amplifier integrated circuit (IC) ISOA1. ISOA1includes a first signal input terminal INP1, a second signal input terminal INP2, a reference-voltage terminal GNT1, an output terminal DIF1, and the sense-signal isolation circuit.

LIN1is connected to INP1via RS1, LIN2is connected to INP2via RS2, and GND1is connected to GNT1. Furthermore, INP1is connected to GND1via RS3. INP2is connected to GND1via RS4. The voltage of LIN1can be lowered by RS1and RS3and input to INP1. The voltage of LIN2can be lowered by RS2and RS4and input to INP2.

The signal indicating the voltage difference is output from the output terminal DIF1of ISOA1. ISOA1adjacent to INP1and ISOA1adjacent to DIF1are electrically isolated. To indicate this isolation, the circuit symbol of ISOA1illustrated inFIG.1is shown separately as two blocks: right and left blocks. Such ISOA1can detect the difference voltage between LIN1and LIN2with reference to GND1. In other words, ACS1can detect the difference voltage between LIN1and LIN2with reference to GND1. An isolation amplifier IC having one signal input terminal uses GNT1connected to LIN1or LIN2, and hence, common grounding, which will be described later on, cannot be achieved.

Common Grounding of Isolated Gate Driving Circuit Through Reference-Voltage Node Connection

The first gate driving circuit GDR1including a drive-signal isolation circuit, and the second gate driving circuit GDR2including a drive-signal isolation circuit are connected to INV1. GDR1and GDR2are partly connected to GND1. To be more specific, the reference-voltage terminals of GDR1and GDR2adjacent to INV1are connected to GND1. INV1and CNT1are isolation-connected together by the drive-signal isolation circuit of GDR1and the drive-signal isolation circuit of GDR2.

GDR1and GDR2are connected to transistors, which will be described later on. GDR1and GDR2are ICs provided with a drive-signal isolation circuit using a photocoupler. The dotted-line symbols within the circuit diagrams of GDR1and GDR2inFIG.1indicate that the ICs are isolated inside.

In PS1, common-grounding connection is established where all the ICs, i.e., ISOA1, GDR1and GDR2, are connected to GND1. A power supply (not shown) that is supplied to all the ICs can be a common power supply (not shown) in this case. This can simplify the sensor's circuit configuration including the commonization of a power supply (not shown). Furthermore, all the circuits connecting INV1and CNT1together are provided with an isolated circuit, thus establishing isolation connection between INV1and CNT1.

Another method is connecting GNT1of ISOA1to LIN1or LIN2to detect AC voltage. The circuit configuration including ACS1is unfortunately complicated in this case because common grounding between the ground terminals of respective GDR1and GDR2is difficult.

Connection Configuration Between Inverter Circuit and AC-Voltage Sensor Circuit

As illustrated inFIG.1, INV1includes a first coil COI1, a second coil COI2, a first transistor TRN1, a second transistor TRN2, a third transistor TRN3, a fourth transistor TRN4, and an input capacitor CAP1. The negative electrode of CAP1is connected to GND1. The series circuit of the first transistor TRN1and second transistor TRN2is connected in parallel to CAP1. The connection node between TRN1and TRN2is connected to LIN1via the first coil COI1. The series circuit of the third transistor TRN3and fourth transistor TRN4is connected in parallel to CAP1. The connection node between TRN3and TRN4is connected to LIN2via the second coil COI2. This inverter circuit, although including two coils: COI1and COI2, can include one of them.

TRN1or TRN2is connected to GDR1.FIG.1illustrates, by way of example only, a circuit configuration where TRN1and TRN2are both connected to GDR1. At least one of TRN1and TRN2needs to be connected to GDR1. CNT1drives TRN1or TRN2via GDR1. REC1or REC2is connected to GDR2.FIG.1illustrates, by way of example only, a circuit configuration where REC1and REC2are both connected to GDR2. At least one of REC1and REC2needs to be connected to GDR2. CNT1drives REC1or REC2via GDR2.

CNT1can drive two transistors via GDR1. A single transistor and a single gate driving circuit may be connected on a one-to-one basis by increasing the number of gate driving circuits.

A typical inverter circuit performs a circuit operation where the voltage of LIN1and the voltage of LIN2do not both coincide with GND1. Hence, the differential voltage between LIN1and LIN2needs to be detected in order to detect AC voltage accurately. However, the commonization of a power supply (not shown) is unfortunately difficult in a conventional differential-voltage detecting circuit because it is difficult to connect the AC voltage sensor to the reference-voltage node. Using ACS1according to the present disclosure can solve these problems.

As illustrated inFIG.1, the power supply circuit PS1is configured such that a DC input unit DCI1, DDC1, INV1, and ACO1are sequentially connected from the input of its power supply toward the output of the same. DDC1, connected to INV1, is connected to CNT1via the isolated circuit ISOC1.

INV1is connected to DDC1without isolation. CNT1is isolation-connected to DDC1. DDC1is controlled by CNT1via the isolated circuit ISOC1. That is, the circuits connecting CNT1to “INV1and DDC1” are all isolated circuits. Using ACS1in PS1having such a circuit configuration enables a differential voltage signal to be transmitted to CNT1with isolation. Furthermore, one CNT1can control both INV1and DDC1with isolation.

It should be noted that each of the foregoing numeric values is a mere example. It is also noted that to adjust circuit operations, a resistor can be added on a wire in the circuit diagram as appropriate, or a capacitor can be added between wires in the circuit diagram as appropriate.