JP6713834B2 - Power supply and lighting - Google Patents

Description

The present invention relates to a power supply device that supplies power to lighting or the like.

A switching power supply device using a transformer such as a flyback transformer is often used in lighting devices and the like. This type of power supply device detects a voltage value or a current value of a load (lighting device or the like) connected to a secondary winding side of a transformer and detects the primary winding side as described in Patent Document 1, for example. A constant voltage (current) is obtained by feeding back to a control device or the like provided in the control unit to control the switching element.

JP, 2013-69766, A

The output current (output voltage) of the power supply unit has ripples synchronized with switching superimposed on the DC component, and if the timing of feedback is high ripple timing or low ripple timing, it was detected as the average value of the actual current. An error may occur with the current value, and as a result, the accuracy of the output current of the power supply device may decrease.

The present invention aims to solve such problems.

That is, an object of the present invention is to provide a power supply device that can improve the accuracy of output current.

The invention described in claim 1 made to solve the above problems controls a transformer including a primary winding and a secondary winding, a switching element connected to the primary winding, and the switching element. In a power supply device including switching control means, the timing is detected, which is connected to the secondary winding and detects an output current value on the secondary winding side based on a switching waveform on the secondary winding side. A power supply device comprising a current detection unit, wherein the switching control unit controls the switching element based on the output current value detected by the current detection unit.

A second aspect of the present invention is the invention according to the first aspect, wherein the current detecting means detects a period of either one of a high level and a low level per cycle of the switching waveform. The present invention is characterized in that a means is provided, and the center of the period detected by the period detecting means is the timing for detecting the output current value on the secondary winding side.

According to a third aspect of the present invention, in the second aspect of the present invention, the current detection unit is a period of one of a high level and a low level per cycle of the switching waveform by the period detection unit. It is characterized in that the output current value is detected at the timing in the next cycle after the detection.

The invention described in claim 4 is the invention described in claim 2 or 3 , wherein the secondary winding of the transformer includes an auxiliary winding, and the current detection means appears in the auxiliary winding. It is characterized in that the period is detected based on a waveform.

According to a fifth aspect of the present invention, there is provided an illumination unit and the power supply device according to any one of the first to fourth aspects, and power is supplied from the power supply device to the illumination unit. It is a characteristic lighting device.

According to the invention described in claim 1, it is possible to calculate an appropriate timing for feeding back the output current value to the switching control means from the switching waveform on the secondary winding side. Therefore, the difference between the detected current value and the average value of the actual current can be reduced, and the accuracy of the output current can be improved.

According to the invention described in claim 2, the feedback timing can be set to indicate the average value of the output current values. Therefore, it is possible to reduce the influence of ripples and reduce the error from the target current value.

According to the third aspect of the present invention, the output current value can be detected immediately after the period detection means detects the period.

According to the invention described in claim 4, a circuit or the like for lowering the voltage on the secondary winding side is not required for the current detecting means, and the circuit can be simplified and the cost such as the number of parts can be reduced. ..

According to invention of Claim 5, the precision of the electric current supplied to an illuminating part in an illuminating device can be improved. For example, when there are a plurality of illumination units, it is possible to reduce variations in the supplied current. Therefore, it is possible to reduce variations in the brightness and color tone of the illumination unit.

It is a circuit diagram of the power supply device concerning one Embodiment of this invention. 6 is a timing chart showing switching waveforms and current changes on the secondary side of the transformer in the circuit shown in FIG. 1. 3 is a flowchart of the operation of the CPU shown in FIG. 1. 3 is a flowchart of the operation of the CPU shown in FIG. 1. FIG. 2 is a schematic configuration diagram of an LED lighting device including the power supply device shown in FIG. 1.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a circuit diagram of a power supply device according to an embodiment of the present invention.

As shown in FIG. 1, the power supply device 1 includes an IC 2, an FET 3, a photocoupler 4, a CPU 6, an operational amplifier 7, resistors R1, R2, R3, R4, R5, R6, capacitors C1, C2, It includes C3, diodes D1, D2, D3, D4, and a transformer T1. The power supply device 1 is provided with an input + terminal and an input-terminal to which a commercial power source is connected, for example, and an output + terminal and an output-terminal to which a load such as a lighting fixture is connected as an output terminal. ..

The IC2 as a switching control means is a flyback control IC (Integrated Circuit), and has a reference voltage output terminal Vref, a feedback input terminal FB, an FET gate drive output terminal GATE, a primary side (primary winding side) of the transformer T1 and an FET3. It has a sense input terminal SENSE for a current flowing through it, a power supply input terminal VIN, and a ground terminal GND. The IC 2 controls the switching of the FET 3 from the FET gate drive output terminal GATE based on the current value input to the feedback input terminal FB from the CPU 6 described later via the photocoupler 4.

The FET 3 as a switching element is an n-channel field effect transistor in FIG. In the FET3, the drain is connected to the other end of the primary side main winding T11 of the transformer T1, the source is connected to the current sense input terminal SENSE of the IC1 and one end of the resistor R5, and the gate is connected to the GATE terminal of the IC2. There is. The FET3 is switched by being controlled by the FET gate drive output terminal GATE of the IC2, and controls the current flowing through the primary side of the transformer T1.

The photocoupler 4 is a well-known element having a light emitting means such as a light emitting diode on the transmitting side and a light receiving means such as a phototransistor on the receiving side. The photocoupler 4 is a state in which the primary side and the secondary side (secondary winding side) of the transformer T1 are insulated from each other, and the current value output from the analog output terminal DAC of the CPU 6 provided on the secondary side is primary. It is provided for input to the feedback input terminal FB of the IC 2 provided on the side.

The CPU 6 as the current detection unit and the period detection unit is a microcomputer including not only a CPU (Central Processing Unit) but also a ROM (Read Only Memory), a RAM (Random Access Memory), and the control stored in the ROM. Works according to the program. The CPU 6 includes an analog input terminal ADC, an analog output terminal DAC, an input capture terminal IC, a digital input terminal DI, a power supply input terminal VIN, and a ground terminal GND. The CPU 6 detects the high level period of the switching waveform appearing in the secondary auxiliary winding T22 of the transformer T1, and acquires the secondary side output current value of the transformer T1 detected by the operational amplifier 7 from the analog input terminal ADC. Determine the timing. Then, at the determined timing, the output current value on the secondary side is acquired and output to the IC2.

The operational amplifier 7 senses (acquires) the current value (output current value) flowing through the secondary side main winding T21 of the transformer T1. Although the circuit of FIG. 1 is connected to the output-terminal side wiring, it may be connected to the output+terminal side wiring.

The resistor R1 has one end connected to the input+terminal and one end of the primary side main winding T11 of the transformer T1, and the other end connected to the power input terminal VIN of the IC2, the cathode of the diode D2 and one end of the capacitor C2. The resistor R2 has one end connected to the other end of the secondary main winding T21 of the transformer T1, the other end of the capacitor C1 and the-input terminal of the operational amplifier 7, and the other end to the + input terminal and the output-terminal of the operational amplifier 7. It is connected. The resistor R3 has one end connected to the reference voltage output terminal Vref of the IC2 and the other end connected to the feedback input terminal FB of the IC2 and one end of the resistor R4. The resistor R4 has one end connected to the feedback input terminal FB of the IC2 and the other end of the resistor R3, and the other end connected to the receiving side of the photocoupler 4.

The resistor R5 has one end connected to the current sense input terminal SENSE of the IC1 and the source of the FET3, and the other end connected to the ground terminal GND of the IC1, the input-terminal, the other end of the capacitor C2 and the receiving side of the photocoupler 4. ing. The resistor R6 has one end connected to the transmission side of the photocoupler 4 and the other end connected to the analog output terminal DAC of the CPU 6.

The capacitor C1 has one end connected to the cathode of the diode D1 and the output + terminal, and the other end connected to the other end of the secondary side main winding T21 of the transformer T1, the − input terminal of the operational amplifier 7, and one end of the resistor R2. There is. One end of the capacitor C2 is connected to the cathode of the diode D2, the other end of the resistor R1 and the power input terminal VIN of the IC2, and the other end of the capacitor C2 is the other end of the primary auxiliary winding T12 of the transformer T1, the other end of the resistor R5, IC2 Is connected to the ground terminal GND, the input-terminal, and the receiving side of the photocoupler 4. The capacitor C3 has one end connected to the cathode of the diode D3 and the power supply input terminal VIN of the CPU 6, and the other end of the capacitor C3. The other end of the secondary auxiliary winding T22 of the traverse T1, the transmission side of the photocoupler 4, and the ground terminal GND of the CPU 6. It is connected to the.

The diode D1 has an anode connected to one end of the secondary side main winding T21 of the transformer T1, and a cathode connected to one end of the capacitor C1 and an output+terminal. The diode D2 has an anode connected to one end of the primary side auxiliary winding T12 of the transformer T1, and a cathode connected to one end of the capacitor C2, the other end of the resistor R1 and the power input terminal VIN of the IC1.

The diode D3 has an anode connected to one end of the secondary auxiliary winding T22 of the transformer T1 and an anode of the diode D4, and a cathode connected to one end of the capacitor C3 and the power input terminal VIN of the CPU 6. The diode D4 has an anode connected to one end of the secondary auxiliary winding T22 of the transformer T1 and an anode of the diode D3, and a cathode connected to the input capture terminal IC and the digital input terminal DI of the CPU 6.

The transformer T1 is a flyback transformer having a main winding and an auxiliary winding on both the primary side and the secondary side. That is, in the transformer T1, the primary side main winding T11 and the primary side auxiliary winding T12 form a primary winding, and the secondary side main winding T21 and the secondary side auxiliary winding T22 form a secondary winding. I am configuring.

The primary side main winding T11 has one end connected to the input+terminal and one end of the resistor R1, and the other end connected to the drain of the FET3. The primary side auxiliary winding T12 has one end connected to the anode of the diode D2, and the other end connected to the other end of the capacitor C2, the other end of the resistor R5, the ground terminal GND of IC2, the input-terminal, and the receiving side of the photocoupler 4. It is connected. The secondary side main winding T21 (secondary winding) has one end connected to the anode of the diode D1 and the other end connected to the other end of the capacitor C1, one end of the resistor R2, and the negative input terminal of the operational amplifier 7. .. The secondary side auxiliary winding T22 has one end connected to the anode of the diode D3 and the anode of the diode D4, and the other end connected to the other end of the capacitor C3, the ground terminal GND of the CPU 6 and the transmission side of the photocoupler 4. ..

Next, the operation of the circuit described above will be described. When the FET3 is turned on by the IC2, a switching current flows through the primary side main winding T11 of the transformer T1 and electric energy is converted into magnetic energy. At this time, no current flows in the secondary side of the transformer T1 due to the polarities of the diodes D1 and D3, and magnetic energy is stored in the insulating transformer T1. After that, when the FET3 is turned off, the magnetic energy accumulated in the transformer T1 during the ON period of the FET3 is re-converted into electric energy and is discharged from the secondary side of the transformer T1 to charge the capacitors C1 and C3. In this way, the FET 3 is periodically turned on/off to generate a DC voltage insulated from the primary side on the secondary side of the transformer T1, and a DC voltage generated across the capacitor C1 is applied to the load. Is applied to the load to operate.

The CPU 6 acquires the output current value flowing through the secondary side (load side) of the transformer T1 detected by the operational amplifier 7, and feeds back the value to the IC 2 via the photocoupler 4. The IC 2 controls the switching of the FET 3 based on the fed back current value so that the current value becomes a predetermined target value.

FIG. 2 is a timing chart showing switching waveforms and current changes on the secondary side of the transformer T1 in the circuit shown in FIG. The upper part of FIG. 2 shows the switching waveform and the change in voltage, and the lower part shows the waveform of the output current on the secondary side of the transformer T1.

When the switching waveform changes as shown in FIG. 2, the output current on the secondary side of the transformer T1 becomes a waveform in which ripples are superimposed on the DC component as shown by the solid line in the lower part of FIG. The broken line in the lower part of FIG. 2 is a waveform showing the average of the output current (solid line). As is clear from FIG. 2, if this average current value can be fed back to the IC2, the switching control of the FET3 is performed in the IC2 so as to match the average current value with the target value, and the accuracy of the output current value is improved.

However, since the CPU 6 does not know the timing at which the IC 2 performs switching control of the FET 3, if the timing at which the current value to be fed back is acquired is the timing with a high ripple or the timing with a low ripple, the IC 2 is based on a value different from the actual average value. Therefore, the accuracy of the output current deteriorates.

Therefore, in the present embodiment, the CPU 6 observes the switch waveform on the secondary side, and determines the appropriate feedback timing based on the waveform. Specifically, the voltage waveform of the secondary side auxiliary winding T22 of the transformer T1 is acquired as a switching waveform at the input capture terminal IC and the digital input terminal DI via the diode D4. Then, the high-level period t1 per cycle of the switching waveform is calculated (see FIG. 2). The period t1 may be calculated from the rising and falling timings of the switching waveform detected by the input capture terminal IC, or the period in which the digital input terminal DI is recognized as a high level may be calculated by a timer or the like.

When the high-level period t1 of the switching waveform is calculated, 1/2 of the period t1 is calculated, and the time t1/2 after the transition to the high level is taken as the output current value acquisition timing. That is, the center of the detected high level period is the timing for detecting the output current value on the secondary winding side.

The ripple appearing in the output current is synchronized with the switching as shown in FIG. Therefore, after t1/2 has passed since the high level, as is apparent from FIG. 2, the timing becomes the intersection of the solid line and the broken line, which is the average value of the output current values (timing with small ripple). Therefore, by obtaining and feeding back the output current value at this timing, the IC2 can perform switching control based on the average current value, and the accuracy of the output current value can be improved.

In the above description, it is assumed that t1/2 has elapsed after changing to the high level, but a low level period may be calculated and 1/2 of the low level period may be set as the acquisition timing of the output current value. ..

The operation of the CPU 6 described above is summarized in the flowcharts of FIGS. 3 and 4. The flowchart of FIG. 3 shows the operation for detecting t1/2 described above. In the flowchart of FIG. 3, in step S11, the CPU 6 acquires the switching waveform from the secondary auxiliary winding T22 of the transformer T1 at the input capture terminal IC and the digital input terminal DI. Next, in step S12, the CPU 6 calculates the high level period t1 of the acquired switching waveform. Then, in step S13, the CPU 6 calculates t1/2. This is repeated thereafter. It should be noted that the repetition may be performed every predetermined time (once in a plurality of cycles, every few seconds, every few minutes, etc.) without performing each time.

Next, a flow chart of the current value detection and feedback operation of FIG. 4 will be described. In the flowchart of FIG. 4, in step S21, the CPU 6 determines whether or not t1/2 has been calculated according to the flowchart of FIG. 3, and if it has been calculated, in step S22, the CPU 6 raises the switching waveform. It is judged whether or not it is detected. Next, if a rising edge is detected in step S22, the CPU 6 determines in step S23 whether or not t1/2 has elapsed, and if so, the current value (output current value) is output from the operational amplifier 7 in step S24. The obtained current value is fed back (FB) to the IC 2 in step S25.

Since this embodiment operates as in the flowchart of FIG. 4, when t1 is calculated in the first cycle of the switching waveform in FIG. 2, for example, the current value is acquired from the next cycle at a timing using the t1. .. That is, the current value is acquired at the timing based on the t1 in the cycle next to the time when t1 is calculated. The current value may be acquired in a later cycle instead of the next cycle, but it is preferable to acquire the current value in the next cycle in consideration of a change in current due to a load.

FIG. 5 shows a schematic configuration diagram of an LED lighting device 100 including the power supply device 1 shown in FIG. The LED lighting device 100 includes a power supply device 1, a commercial AC power supply 10, and an LED module 20.

The commercial AC power supply 10 is connected to the input + terminal and the input − terminal of the power supply device 1 and supplies AC power to the power supply device.

The LED module 20 as a lighting unit is a lighting fixture having an LED (light emitting diode) as a light emitting element. The LED module 20 is connected to the output + terminal and the output − terminal of the power supply device 1 and operates as a load to which power is supplied from the power supply device 1. There may be a plurality of LED modules 20.

According to this embodiment, the timing for detecting the output current value on the secondary winding side is determined based on the switching waveform of the secondary auxiliary winding T22 that is connected to the secondary auxiliary winding T22 of the transformer T1. The IC 2 controls the FET 3 based on the output current value detected by the CPU 6. By doing so, an appropriate timing for feeding back the output current value to the IC2 can be calculated from the switching waveform on the secondary winding side. Therefore, the difference between the detected current value and the average value of the actual current can be reduced, and the accuracy of the output current can be improved. Further, the CPU 6 detects the high level period based on the switching waveform that appears in the secondary side auxiliary winding T22. By doing so, a circuit or the like for reducing the voltage on the secondary side for the CPU 6 becomes unnecessary, so that the circuit can be simplified and the cost such as the number of parts can be reduced.

Further, the CPU 6 detects the high level period of the switching waveform and detects the output current value on the secondary winding side at the center of the detected period, that is, at t1/2. By doing so, the average of the high ripple value and the low ripple value can be used as the feedback timing. As the ripple changes linearly from a high value to a low value or from a low value to a high value as shown in Fig. 2, it is possible to feed back the average value of the current that fluctuates due to the ripple and reduce the effect of the ripple. Therefore, the error from the target current value can be reduced.

Since the switching waveform may change during the high level period, the average value of the output current values is more reliably used as the acquisition timing by detecting the high level period and determining the detection timing of the output current value. be able to.

Further, since the output current value is detected using t1/2 from the cycle next to the cycle in which t1/2 of the switching waveform is calculated, the output current value can be detected immediately after the calculation of t1/2.

Further, since the LED lighting device 100 including the commercial AC power supply 10 and the LED module 20 is provided with the power supply device 1, the accuracy of the current supplied to the LED module 20 in the LED lighting device 100 can be improved. For example, when there are a plurality of LED lighting devices 100, it is possible to reduce variations in the supplied current. Therefore, it is possible to reduce variations in the brightness and color tone of the LED module 20.

In the circuit shown in FIG. 1, the auxiliary winding T22 is provided on the secondary side of the transformer T1, and the period t1 is calculated based on the switching waveform appearing in the auxiliary winding T22. Need not be provided, and in that case, the period t1 may be calculated based on the switching waveform appearing in the main winding T21.

The present invention is not limited to the above embodiment. That is, a person skilled in the art can carry out various modifications according to the conventionally known knowledge without departing from the gist of the present invention. As long as such a modification still has the configuration of the power supply device of the present invention, it is of course included in the scope of the present invention.

1 power supply device 2 IC (switching control means)
3 FET (switching element)
6 CPU (current detection means, period detection means)
20 LED module (illumination part)
T1 transformer T11 primary side main winding (primary winding)
T21 Secondary side main winding (secondary winding)
T22 Secondary side auxiliary winding (auxiliary winding)

Claims (5)

In a power supply device comprising a transformer including a primary winding and a secondary winding, a switching element connected to the primary winding, and a switching control means for controlling the switching element,
A current detection unit that is connected to the secondary winding and determines a timing for detecting an output current value on the secondary winding side based on a switching waveform on the secondary winding side;
The switching control means controls the switching element based on the output current value detected by the current detection means,
A power supply device characterized by the above. The current detecting means includes a period detecting means for detecting one of a high level period and a low level period per one cycle of the switching waveform, and the center of the period detected by the period detecting means is the secondary winding. The power supply device according to claim 1, wherein the timing is for detecting an output current value on the line side. The current detection means detects the output current value at the timing in the next cycle when the period detection means detects one of a high level and a low level per cycle of the switching waveform. The power supply device according to claim 2. The secondary winding of the transformer includes an auxiliary winding,
The power supply device according to claim 2 or 3 , wherein the current detection unit detects the period based on a waveform that appears in the auxiliary winding. An illumination unit and the power supply device according to any one of claims 1 to 4,
A lighting device, wherein power is supplied from the power supply device to the lighting unit.

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