JP7396219B2 - Power supplies and lighting equipment - Google Patents

Description

The present disclosure relates to power supplies and lighting fixtures.

Patent Document 1 discloses a power supply device including a boost chopper circuit that improves the power factor of input from a commercial AC power source by switching a switching element. This power supply device includes an input voltage detection section that detects the input voltage of the boost chopper circuit, and an output voltage detection section that detects the output voltage of the boost chopper circuit. The power supply device also includes an error amplifier, a multiplier, a comparator, and a driver circuit. The error amplifier amplifies the difference between the voltage corresponding to the voltage detected by the output voltage detection section and the reference voltage. The multiplier multiplies the output voltage from the error amplifier and the voltage detected by the input voltage detection section. The comparator compares the output signal of the multiplier with a voltage corresponding to the drain current of the switching element. The driver circuit generates a gate signal for the switching element based on the output signal from the comparator. As a result, feedback control is performed so that the output voltage of the boost chopper circuit approaches the set voltage while improving the power factor.

Patent No. 6557460

In the power supply device as shown in Patent Document 1, when the input voltage temporarily fluctuates due to sag or the like, the output of the multiplier also fluctuates. Therefore, overshoot or undershoot may easily occur in the output voltage of the switching circuit.

The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to obtain a power supply device and a lighting fixture that can suppress fluctuations in the output voltage of a switching circuit in response to fluctuations in the input voltage to the switching circuit. do.

A power supply device according to the present disclosure includes a switching circuit that supplies power to a load by turning on and off the switching element, and controlling the on/off of the switching element so that the output voltage of the switching circuit matches a predetermined target value. a control circuit that calculates a feedback voltage by adding or multiplying a bias voltage and a voltage corresponding to the difference between the output voltage of the switching circuit and the target value; The switching element is turned on and off according to a comparison result between the voltage and a voltage corresponding to a current flowing through the switching element, and the bias voltage corresponds to an input voltage waveform to the switching circuit in a steady state. The input voltage waveform to the switching circuit has a peak portion and a valley portion, and the bias voltage is set so that the on-time of the switching element is longer in the peak portion than in the valley portion. The area is set larger than the valley area .
A power supply device according to the present disclosure includes a switching circuit that supplies power to a load by turning on and off the switching element, and controlling the on/off of the switching element so that the output voltage of the switching circuit matches a predetermined target value. a control circuit that calculates a feedback voltage by adding or multiplying a bias voltage and a voltage corresponding to the difference between the output voltage of the switching circuit and the target value; The switching element is turned on and off according to a comparison result between the voltage and a voltage corresponding to a current flowing through the switching element, and the bias voltage corresponds to an input voltage waveform to the switching circuit in a steady state. The control circuit stores a table that associates the input voltage to the switching circuit with the bias voltage, and refers to the table according to the input voltage to the switching circuit to adjust the bias voltage. is updated, and the bias voltage is updated at a cycle longer than the cycle of the input voltage to the switching circuit.

In the power supply device according to the present disclosure, the feedback voltage is calculated by adding or multiplying the voltage corresponding to the difference between the output voltage of the switching circuit and a predetermined target value and the bias voltage. Furthermore, depending on the comparison result between the feedback voltage and the voltage corresponding to the current flowing through the switching element, the on/off of the switching element is controlled so that the output voltage of the switching circuit matches the target value. The bias voltage is a voltage that varies in response to the input voltage waveform to the switching circuit in a steady state. Therefore, it is possible to suppress fluctuations in the input voltage to the switching circuit from being reflected in the feedback voltage. Therefore, fluctuations in the output voltage of the switching circuit can be suppressed with respect to fluctuations in the input voltage to the switching circuit.

1 is a circuit block diagram of a lighting fixture according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating functions of a control circuit according to the first embodiment. FIG. 3 is a diagram showing waveforms of each part of the power supply device according to the first embodiment. FIG. 7 is a diagram illustrating waveforms of a power supply device according to a comparative example. FIG. 3 is a diagram illustrating waveforms of the power supply device according to the first embodiment.

A power supply device and a lighting fixture according to the present embodiment will be described with reference to the drawings. Identical or corresponding components may be given the same reference numerals and repeated descriptions may be omitted.

Embodiment 1.
FIG. 1 is a circuit block diagram of a lighting fixture 100 according to the first embodiment. The lighting fixture 100 includes a power supply device 10 and a load 80. The load 80 includes, for example, a light source. The power supply device 10 turns on the light source. The load 80 is not limited to a light source, and may be any load that can function by being supplied with power from the power supply device 10.

An alternating current power supply AC is connected to the input terminal 71 of the power supply device 10 . A load 80 is connected to the output end 72 of the power supply device 10 . The power supply device 10 includes an input filter circuit 1 , an input voltage detection circuit 2 , a switching circuit 3 , an output voltage detection circuit 5 , and a control section 6 .

The input filter circuit 1 includes a fuse 11, an AC capacitor 12, and a diode bridge 13. Fuse 11 is provided to protect against overcurrent. Diode bridge 13 is provided to convert alternating current to direct current. The output of diode bridge 13 is connected to switching circuit 3. The low potential side of the output of the diode bridge 13 is connected to a ground terminal.

The switching circuit 3 is composed of an isolated flyback converter circuit. The primary side and secondary side of the switching circuit 3 are separated. The switching circuit 3 improves the power factor of the input from the AC power supply AC by switching the switching elements. A voltage obtained by rectifying an alternating current voltage is input to the switching circuit 3 . The switching circuit 3 converts power shared from an alternating current power supply AC, which is a commercial power supply, into power suitable for the load 80. The control section 30 controls the switching circuit 3.

In the switching circuit 3, a capacitor 31 is connected in parallel with the output of the diode bridge 13. The positive electrode of the capacitor 38 , one end of the resistor 37 , and one end of the primary side of the transformer 33 are connected to the positive electrode of the capacitor 31 . A cathode of a diode 39 is connected to the negative electrode of the capacitor 38 and the other end of the resistor 37. The anode of the diode 39 is connected to the other end of the primary side of the transformer 33. Capacitor 38, resistor 37, and diode 39 form a snubber circuit that absorbs transient high potentials associated with switching.

A first terminal of a switching element 35 is connected in series to the other end of the primary side of the transformer 33 . A second terminal of the switching element 35 is connected to the negative electrode of the capacitor 31 via a resistor 36. A control terminal of the switching element 35 is connected to the control section 30 . The control terminal is a terminal for switching between the first and second terminals.

The switching element 35 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). When the switching element 35 is a MOSFET, the first terminal is a drain terminal, the second terminal is a source terminal, and the control terminal is a gate terminal. In the switching element 35, a first terminal is electrically connected to the transformer 33, a second terminal is electrically connected to a grounding terminal, and a control terminal is electrically connected to the control section 30.

The control unit 30 has a driver for switching control. The control section 30 drives the switching element 35. A resistor 41 is connected to the positive electrode of the capacitor 31 . The control unit 30 is supplied with power from a capacitor 31 via a resistor 41.

A photocoupler 65 is connected to the control section 30 . A photocoupler 65 is provided to input information on the secondary side of the transformer 33 to the control unit 30.

Resistor 36 is provided to detect the drain current of switching element 35. The resistor 36 is connected between the source terminal of the switching element 35 and the ground terminal. One end of the resistor 36 is connected to the control section 30. Thereby, the source voltage of the switching element 35 is input to the control section 30, and the control section 30 can detect the drain current.

An anode of a diode 34 is connected to one end of the flyback winding on the secondary side of the transformer 33 . The diode 34 is connected in series to the secondary side of the transformer 33 and is provided to transmit a stable voltage to the output side. The cathode of the diode 34 is connected to the positive electrode of the electrolytic capacitor 32 . The negative electrode of the electrolytic capacitor 32 is connected to a ground terminal.

In the grounding path of the switching circuit 3, the primary and secondary sides of the transformer 33 are insulated by a capacitor 40.

The control unit 6 includes a microcomputer 62 and a regulator 61. Regulator 61 is provided to stabilize the voltage. Regulator 61 generates voltage Vcc from the voltage of electrolytic capacitor 32. Voltage Vcc is supplied to microcomputer 62 as a power source.

A series circuit of a resistor 63 and a capacitor 64 is connected between the FB terminal and the ground terminal of the microcomputer 62. A photocoupler 65 is connected in parallel with the capacitor 64. The voltage output from the FB terminal of the microcomputer 62 is filtered by a resistor 63 and a capacitor 64, and transmitted to the primary side via a photocoupler 65. The primary side of the photocoupler 65 is connected to the control section 30. The control unit 30 receives a feedback voltage, which will be described later, from the microcomputer 62 via the photocoupler 65.

The input voltage detection circuit 2 detects the input voltage to the switching circuit 3. The input voltage detection circuit 2 includes resistors 21 and 22 connected in series, and a photocoupler 23 connected in parallel with the resistor 22. Input voltage detection circuit 2 is connected in parallel with capacitor 31. The output of the photocoupler 23 is transmitted to the microcomputer 62. Thereby, the microcomputer 62 detects the input voltage Vin to the switching circuit 3.

Output voltage detection circuit 5 detects the output voltage of switching circuit 3. The output voltage detection circuit 5 is composed of resistors 51 and 52 connected in series. The output voltage detection circuit 5 is connected in parallel with the electrolytic capacitor 32. The divided voltage values of the resistors 51 and 52 are input to the microcomputer 62. Thereby, the microcomputer 62 detects the output voltage Vout of the switching circuit 3.

FIG. 2 is a diagram illustrating the functions of control circuit 60 according to the first embodiment. In this embodiment, as an example, a multiplier control method is adopted in which the on-time of switching is controlled for each switching.

The control circuit 60 is formed from a microcomputer 62 and a control section 30. The microcomputer 62 includes a CPU that performs various calculations, a memory, and a timer. Values and programs used for calculations by the CPU are written in advance in the memory. The memory is composed of, for example, non-volatile memory. Further, the functions of the microcomputer 62 may be realized by dedicated hardware. Furthermore, some of the functions of the microcomputer 62 may be realized by dedicated hardware, and some may be realized by software or firmware.

The control unit 30 can also be configured with a microcomputer or dedicated hardware. Furthermore, some of the functions of the control unit 30 may be realized by dedicated hardware, and some may be realized by software or firmware. Further, the control circuit 60 may be configured from a single microcomputer or a control device such as hardware.

The microcomputer 62 has an amplifier 62a. The output voltage Vout is input to one input of the amplifier 62a via a resistor 62b. A reference power supply 62c is connected between the other input of the amplifier 62a and the ground terminal GND. A series circuit of a capacitor 62d and a resistor 62e is connected between one input and the output of the amplifier 62a. The output of amplifier 62a is connected to one input of amplifier 62f. A signal from the oscillator is input to the other input of the amplifier 62f. Amplifier 62a, resistor 62b, capacitor 62d, resistor 62e, and amplifier 62f constitute an error amplifier. The error amplifier outputs a voltage corresponding to the difference between the output voltage Vout of the switching circuit 3 and a predetermined target value. Here, the predetermined target value corresponds to the voltage of the reference power source 62c. In the microcomputer 62, the error amplifier is virtually constructed by a program.

Furthermore, the microcomputer 62 has a computing unit 62g. The arithmetic unit 62g calculates the feedback voltage FB by adding or multiplying a voltage corresponding to the difference between the output voltage Vout and the target value and a bias voltage, which will be described later. In the microcomputer 62, the arithmetic unit 62g is virtually constructed by a program. The computing unit 62g is also called a multiplier.

Feedback voltage FB is output from the FB terminal of microcomputer 62 and input to control section 30 . Note that in FIG. 2, some of the circuit components shown in FIG. 1 are omitted.

The control unit 30 has a comparator 30a. Comparator 30a compares feedback voltage FB with a voltage corresponding to the current flowing through switching element 35. In this embodiment, the current flowing through the switching element 35 is the drain current Id.

A drive circuit 30b is connected to the output of the comparator 30a. The drive circuit 30b controls on/off of the switching element 35 in accordance with the comparison result of the comparator 30a so that the output voltage Vout of the switching circuit 3 matches the target value.

From the above, constant voltage feedback of the switching circuit 3, which is an isolated flyback circuit, is realized. The control circuit 60 of this embodiment controls on/off of the switching element 35 so that the output voltage of the switching circuit 3 matches a predetermined target value. The switching circuit 3 supplies power to the load 80 by turning the switching element 35 on and off.

FIG. 3 is a diagram showing waveforms of each part of the power supply device 10 according to the first embodiment. The microcomputer 62 stores a table 62h that associates the input voltage Vin with the bias voltage. The table 62h is written in the memory space of the microcomputer 62 in advance. The microcomputer 62 refers to the table 62h and determines the bias voltage according to the input voltage Vin to the switching circuit 3.

The microcomputer 62 uses the input voltage detection circuit 2 to detect, for example, the period of the input voltage Vin. The period of the input voltage Vin is, for example, 50 Hz or 60 Hz. The table 62h is set, for example, for each cycle of the input voltage Vin. The microcomputer 62 selects a table corresponding to the period of the input voltage Vin. The waveform of the bias voltage set in the table 62h is formed from a sine wave having the period of the input voltage Vin to the switching circuit 3, as shown in FIG. The bias voltage in this embodiment has a waveform consisting of a continuous half period of a sine wave. That is, the bias voltage has a full-wave rectified waveform.

When the microcomputer 62 detects the phase of the input voltage Vin that is synchronized with the phase of the sine wave set in the table 62h, the microcomputer 62 determines the bias voltage from the table read according to the input voltage Vin of the switching circuit 3.

The microcomputer 62 calculates the output voltage from the error amplifier and the bias voltage, and inputs the resultant feedback voltage FB to the control unit 30. The control unit 30 compares the feedback voltage FB and the drain current Id of the switching element using a comparator 30a, and inputs the comparison result to the switching circuit 3 as the switching on time. In FIG. 3, the signal input to the switching element 35 is shown as a voltage Vg.

A bias voltage update period is preset in the memory of the microcomputer 62. The update period is a period that is sufficiently slower than the AC cycle of the commercial power source. The microcomputer 62 manages the update period using a timer and updates the bias voltage when the update period has elapsed.

FIG. 4 is a diagram illustrating waveforms of a power supply device according to a comparative example. FIG. 5 is a diagram illustrating waveforms of the power supply device 10 according to the first embodiment. Note that the waveforms shown in FIGS. 4 and 5 are expanded with respect to the AC cycle of the AC power supply AC. Further, the comparative example differs from the present embodiment in that the feedback voltage FB is obtained by multiplying the output of the error amplifier by the input voltage Vin.

When the voltage of the AC power source AC increases, the input voltage Vin detected by the input voltage detection circuit 2 also increases in synchronization.

In the comparative example, the feedback voltage FB obtained by multiplying the output of the error amplifier by the input voltage Vin increases in accordance with the input voltage Vin. The drain current Id increases according to the feedback voltage. Therefore, the output voltage Vout also increases. As a result, the output voltage Vout becomes larger than the target value. Therefore, the error amplifier is controlled to reduce the feedback voltage FB. The drain current Id decreases in accordance with the decreased feedback voltage FB. Therefore, the output voltage Vout decreases and matches the voltage of the reference power supply 62c again.

In this manner, when the input voltage Vin increases in the comparative example, the output voltage Vout also temporarily increases. In other words, there was a risk that so-called overshoot would occur.

On the other hand, in this embodiment, the feedback voltage FB is calculated by calculating the output voltage from the error amplifier and the bias voltage which is a table value. The table values are not affected by temporary fluctuations in the input voltage Vin. Therefore, the feedback voltage FB does not increase due to a temporary increase in the AC power supply AC. Since the feedback voltage FB does not rise, the drain current Id also does not rise. Therefore, the output voltage Vout also does not increase.

In this manner, in this embodiment, even if the input voltage Vin temporarily fluctuates due to sag or the like, it is possible to prevent overshoot or undershoot from occurring in the output voltage Vout. Therefore, fluctuations in the output voltage Vout of the switching circuit 3 can be suppressed with respect to fluctuations in the input voltage Vin to the switching circuit 3.

Further, when the input voltage Vin is not detected and the arithmetic unit 62g is not used, overshoot or undershoot due to fluctuations in the input voltage Vin does not occur. However, the input current tends to be distorted with respect to the input voltage Vin, and the power factor may decrease. In contrast, in the present embodiment, it is possible to suppress fluctuations in the output voltage Vout with respect to fluctuations in the input voltage Vin to the switching circuit 3 while suppressing a decrease in the power factor.

The input voltage Vin corresponds to a voltage obtained by rectifying the voltage of an alternating current power supply AC. Therefore, the steady state input voltage Vin can be easily replaced with a sine wave. Therefore, the table 62h can be easily generated. Note that the steady state refers to a state in which there is no temporary fluctuation such as sag.

Further, the bias voltage is updated at a cycle longer than the cycle of the input voltage Vin to the switching circuit 3. Thereby, the bias voltage can be updated stably.

The control circuit 60 of the present embodiment calculates the feedback voltage FB by adding or multiplying the voltage corresponding to the difference between the output voltage Vout of the switching circuit 3 and the target value and the bias voltage. Further, the control circuit 60 controls on/off of the switching element 35 according to a comparison result between the feedback voltage FB and the voltage corresponding to the current flowing through the switching element 35. The control circuit 60 is not limited to the configuration shown in FIG. 2 as long as it can realize these functions.

Further, the waveform of the bias voltage in this embodiment is similar to the waveform of the input voltage Vin to the switching circuit 3 in a steady state. In other words, the bias voltage is a voltage corresponding to a voltage obtained by rectifying an alternating current voltage in a steady state. As a modification of this example, the waveform of the bias voltage is not limited to a sine wave, and may be different from the waveform of the input voltage Vin. The bias voltage may vary in accordance with the input voltage waveform to the switching circuit 3 in a steady state. In other words, the bias voltage may be set so that the peak portions of the input voltage waveform to the switching circuit 3 are larger than the valley portions of the input voltage waveform.

The comparison result between the feedback voltage FB obtained by adding or multiplying the bias voltage and the drain current Id corresponds to the on-time of the switching element 35. In other words, the bias voltage affects the on-time of the switching element 35. Therefore, the bias voltage may be set so that the on-time of the switching element 35 is longer at the peak portions of the input voltage waveform than at the valley portions.

The technical features described in this embodiment may be used in combination as appropriate.

1 input filter circuit, 2 input voltage detection circuit, 3 switching circuit, 5 output voltage detection circuit, 6 control unit, 10 power supply, 11 fuse, 12 capacitor, 13 diode bridge, 21 resistor, 22 resistor, 23 photocoupler, 30 Control unit, 30a Comparator, 30b Drive circuit, 31 Capacitor, 32 Electrolytic capacitor, 33 Transformer, 34 Diode, 35 Switching element, 36 Resistor, 37 Resistor, 38 Capacitor, 39 Diode, 40 Capacitor, 41 Resistor, 51 Resistor, 52 Resistor , 60 control circuit, 61 regulator, 62 microcomputer, 62a amplifier, 62b resistor, 62c reference power supply, 62d capacitor, 62e resistor, 62f amplifier, 62g arithmetic unit, 62h table, 63 resistor, 64 capacitor, 65 photocoupler, 71 input End, 72 Output end, 80 Load, 100 Lighting equipment, AC AC power supply

Claims (9)

A switching circuit that supplies power to a load by turning on and off a switching element;
a control circuit that controls on/off of the switching element so that the output voltage of the switching circuit matches a predetermined target value;
Equipped with
The control circuit calculates a feedback voltage by adding or multiplying a bias voltage and a voltage corresponding to the difference between the output voltage of the switching circuit and the target value, and the feedback voltage and the voltage flowing to the switching element are controlling on/off of the switching element according to a comparison result of a voltage corresponding to the current;
The bias voltage varies in response to an input voltage waveform to the switching circuit in a steady state ,
The input voltage waveform to the switching circuit has a peak portion and a valley portion,
The power supply device is characterized in that the bias voltage is set to be larger in the peak portions than in the valley portions so that the on time of the switching element is longer in the peak portions than in the valley portions. The control circuit stores a table that associates the input voltage to the switching circuit with the bias voltage, and refers to the table according to the input voltage to the switching circuit to determine the bias voltage. The power supply device according to claim 1. A voltage obtained by rectifying an alternating current voltage is input to the switching circuit,
The power supply device according to claim 1 or 2, wherein the bias voltage is a voltage corresponding to a voltage obtained by rectifying the alternating current voltage in a steady state. 4. The power supply device according to claim 1, wherein the waveform of the bias voltage is formed from a sine wave having a period of the input voltage to the switching circuit . an output voltage detection circuit that detects the output voltage of the switching circuit;
an input voltage detection circuit that detects an input voltage to the switching circuit;
Equipped with
The control circuit includes:
an error amplifier that outputs a voltage corresponding to the difference between the output voltage of the switching circuit and the target value;
an arithmetic unit that calculates the feedback voltage by adding or multiplying the voltage corresponding to the difference and the bias voltage;
a comparator that compares the feedback voltage and a voltage corresponding to the current flowing through the switching element;
a drive circuit that controls on/off of the switching element so that the output voltage of the switching circuit matches the target value according to the comparison result of the comparator;
The power supply device according to any one of claims 1 to 4 , characterized by comprising: A switching circuit that supplies power to a load by turning on and off a switching element;
a control circuit that controls on/off of the switching element so that the output voltage of the switching circuit matches a predetermined target value;
Equipped with
The control circuit calculates a feedback voltage by adding or multiplying a bias voltage and a voltage corresponding to the difference between the output voltage of the switching circuit and the target value, and the feedback voltage and the voltage flowing to the switching element are controlling on/off of the switching element according to a comparison result of a voltage corresponding to the current;
The bias voltage varies in response to an input voltage waveform to the switching circuit in a steady state,
The control circuit stores a table that associates the input voltage to the switching circuit with the bias voltage, and updates the bias voltage by referring to the table according to the input voltage to the switching circuit,
A power supply device characterized in that the bias voltage is updated at a cycle longer than a cycle of the input voltage to the switching circuit. 7. The power supply device according to claim 1, wherein the switching circuit is an isolated flyback converter circuit, and a primary side and a secondary side are separated. The power supply device according to any one of claims 1 to 7 , wherein the control circuit includes a microcomputer. The power supply device according to any one of claims 1 to 8 ,
the load;
Equipped with
the load has a light source;
A lighting fixture, wherein the power supply device lights up the light source.

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