Power supply device

Abstract

The present invention provides a power supply device that incorporates a comparator circuit in the feedback circuit and employs an optical isolator in the voltage conversion section. [Solution] The power supply device comprises a switching circuit that switches an input voltage and converts it into an output voltage, a power transmission unit that transmits the output voltage to an output stage, an optical isolator connected to the power transmission unit that transmits the voltage signal of the output stage to a feedback circuit while isolating it, and a feedback circuit that generates a control signal for switch control based on the voltage signal input from the optical isolator and outputs it to the switching circuit, wherein the feedback circuit generates the control signal by a comparator circuit that binarizes the input voltage signal.

Description

Technical Field

[0001] The present disclosure relates to a power supply device.

Background Art

[0002] From the viewpoints of miniaturization requirements and widespread use of recent information devices and the like, there is a demand for an inexpensive power supply circuit that is small and can be used in various environments such as high withstand voltage and strong noise. The power supply circuit performs an operation of converting an input voltage into a determined output voltage. Patent Document 1 describes a power supply device provided with an optical feedback circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, simply replacing a magnetic feedback circuit with an optical feedback circuit results in oscillation where the output goes high and low. Therefore, an object of the present disclosure is to provide a power supply device including a comparison circuit in a feedback circuit and employing an optical isolator in a voltage conversion unit.

Means for Solving the Problems

[0005] One embodiment includes a feedback circuit that generates a control signal for switch control based on a voltage signal input from an optical isolator and outputs the control signal to a switching circuit, and the feedback circuit is a power supply device that generates the control signal by a comparison circuit that binarizes the input voltage signal.

Effects of the Invention

[0006] According to the above embodiment, a power supply device is provided that includes a comparator circuit in the feedback circuit and employs an optical isolator in the voltage conversion section. [Brief explanation of the drawing]

[0007] [Figure 1] This is a block diagram showing the circuit configuration of power supply devices related to the technology. [Figure 2] This figure shows the details of the feedback circuit of a power supply device related to the relevant technology. [Figure 3] This is an illustrative diagram of the feedback signal in a magnetic voltage conversion circuit related to the technology. [Figure 4] This is an image diagram of the feedback signal in an optical voltage conversion circuit related to the technology. [Figure 5] This document contains a block diagram showing the circuit configuration of a power supply device related to related technologies and a block diagram showing the circuit configuration of a power supply device according to this disclosure. [Figure 6] This diagram shows a block diagram illustrating the circuit configuration of the power supply device related to this disclosure, and an example of the area occupied by the circuit. [Figure 7] This figure shows an example of the A / D conversion result of a magnetic power supply and the count result of the power supply according to this disclosure. [Figure 8] This figure shows an example of how the output voltage of the power supply device described herein converges. [Figure 9] This figure shows examples of output voltages of power supply devices related to related technologies and output voltages of power supply devices according to this disclosure. [Figure 10] Block diagram showing the circuit configuration of the power supply device related to this disclosure. [Figure 11] Block diagram showing the second circuit configuration of the power supply device relating to this disclosure. [Modes for carrying out the invention]

[0008] (Explanation of related technologies) Figure 1 is a block diagram showing the circuit configuration of a power supply device relating to the related technology. Figure 2 is a diagram showing the details of the feedback circuit of a power supply device relating to the related technology. Figure 3 is a diagram of the feedbacked signal of a magnetic voltage conversion circuit relating to the related technology. Figure 4 is a diagram of the feedbacked signal of an optical voltage conversion circuit relating to the related technology. The power supply device relating to the related technology will be explained with reference to Figures 1 to 4.

[0009] The internal configuration of a power supply device 100 related to the switching power supply method will be described using this as an example. As shown in Figure 1, the power supply device 100 includes a switching circuit 101 that adjusts the power, a power transmission unit 102 which is a transformer, a voltage conversion unit 103, and a feedback circuit 104.

[0010] The switching circuit 101 is a power adjustment circuit and is controlled by the feedback circuit 104. In other words, the switching circuit switches the input voltage and converts it into an output voltage. The power transmission unit 102 consists of a transformer or the like and transmits the energy created by the switching circuit 101. In other words, the power transmission unit 102 transmits the output voltage to the output stage. The output stage has both an output to an external circuit and an output to a voltage conversion circuit.

[0011] The voltage conversion unit 103 transmits the output status to the feedback circuit 104. The feedback circuit 104 monitors the difference between the output and the target value so that the output approaches the target value, and operates the switching circuit so that the difference becomes zero. Specifically, control is performed by adjusting the duty cycle or frequency of the PWM (Pulse Width Modulator). In addition, the power supply unit 100 may require isolation due to safety standards, etc. In that case, isolation is performed between the power transmission unit 102 and the voltage conversion unit 103. There are two types of isolation: magnetic and optical. The magnetic type is realized by mutual induction using coils. The optical type uses a photocoupler that combines a light-emitting element such as an LED (Light Emitting Diode) and a light-receiving element such as a photodiode. The LED emits light in response to the input signal, the light-receiving element receives the light and converts it into an electrical signal.

[0012] As a method of the feedback circuit 104, a digital control method using a microcomputer or the like that facilitates efficiency improvement, load characteristic improvement, etc. has become widespread. The feedback circuit 104 of this method converts the output voltage obtained from the voltage conversion unit 103 into a digital value, numerically calculates the difference from the target value, multiplies by a coefficient to calculate a correction value, and reflects the result in the Duty of PWM.

[0013] As shown in FIG. 2, the feedback circuit 104 includes an A / D (analog-digital) converter 201, a result storage register 202, a target value register 203, a subtraction circuit 204, a subtraction result register 205, a coefficient register 206, and a multiplication circuit 207 for a P (subtraction / multiplication) operation circuit, and a PWM timer 208.

[0014] The operation of the feedback circuit 104 will be described. The feedback line signal which is the output is converted by the A / D converter 201. Next, the difference between the target value and the output is calculated by the subtraction circuit 204. Next, the difference is multiplied by the coefficient by the multiplication circuit 207. The PWM timer 208 is changed according to the multiplication result. The output is changed by changing the PWM timer 208. The feedback circuit 104 is operated so that the difference between the target value and the output becomes zero. As a result, the output voltage becomes stable.

[0015] The area of the feedback circuit 104 is, for example, 828 mm for the voltage conversion unit 103 and the feedback circuit 104 2 , 560 mm for the switching circuit 101 and the power transmission unit 102 2 , and 1388 mm in total 2 .

[0016] The operation of the feedback function will be described while referring to FIG. 3. When the actual output is 0 V with respect to the output target voltage of 5 V, the correction value for the output is calculated as follows. The correction value is the relative amount by which the feedback circuit operates on the switching circuit in order to bring the output closer to the target value. A / D conversion value = 0 Err=5.0-0=5.0 P = Err × A

[0017] Here, Err is the error value, which is the difference between the current value and the target value. P is the correction value. A is a coefficient, which is a fixed value determined by the characteristics of the circuit or controller. If A is 1, then P = 5.

[0018] If the calculated correction amount P is positive, the output is controlled to increase; if it is negative, the output is controlled to decrease. A larger absolute value of P results in a stronger control, while a smaller absolute value results in a weaker control. This is called proportional control.

[0019] In Figure 3, step 1 shows that the correction value is positively corrected by the feedback calculation. Step 2 shows that the positive correction value is reflected in the PWM. Step 3 shows that the output increases due to the increase in PWM. Step 4 shows that the output has risen too high, so it is reduced in the next cycle. Step 5 shows that the output stabilizes. Thus, the output of the power supply 100 and the output voltage of the conversion mechanism are the same.

[0020] Magnetic power supplies used in digital control systems have a linear input-output relationship, allowing for the determination of the deviation from the target value. Therefore, it's possible to calculate a correction value for the deviation and implement feedback to bring the value closer to the target. However, magnetic power supplies are physically large and cannot meet the demands for miniaturization. Furthermore, their low dielectric strength makes them unsuitable for equipment requiring high voltage resistance.

[0021] Optical power supplies are characterized by their small size and high dielectric strength, and are an isolated transmission method that can overcome the aforementioned problems. However, if a magnetic conversion mechanism is directly replaced with an optical conversion mechanism, the output will oscillate, fluctuating between high and low. This is because the input-output relationship of an optical system is a nonlinear characteristic that represents whether the output is higher or lower than the target value, and it is not possible to express the amount of deviation from the target value in the same way as a magnetic system.

[0022] As shown in Figure 4, in the optical power supply, 1 the correction value is corrected to a positive value through feedback calculation. 2 the positive correction value is reflected in the PWM. 3 the output increases due to the increase in PWM. 4 the output voltage of the conversion mechanism immediately sticks high near the target voltage. 5 the maximum negative correction value is calculated for the output voltage of the conversion mechanism in the next cycle. 6 the correction value constantly fluctuates at the limit. 7 the output becomes unstable.

[0023] Optical feedback systems have the characteristic of their output staying high when approaching the target voltage and staying low when below the target voltage. Therefore, if the feedback circuit of related technology is used as is, the correction amount will fluctuate between the maximum and minimum values, causing the actual output to waver around the target value and oscillate instead of converging.

[0024] (Description of the power supply according to Embodiment 1) For clarity of explanation, the following descriptions and diagrams have been omitted and simplified as appropriate. Furthermore, each element shown in the diagrams as a functional block performing various processes can, for example, be composed of a CPU (Central Processing Unit), memory, and other circuits in hardware terms, and implemented in software terms by a program loaded into memory. Therefore, these functional blocks can be implemented by hardware, software running on the hardware, or a combination thereof. Note that identical elements are denoted by the same reference numeral in each diagram, and redundant explanations have been omitted where necessary.

[0025] Figure 5 is a block diagram showing the circuit configuration of a power supply device relating to related technology and a block diagram showing the circuit configuration of a power supply device relating to this disclosure. Figure 6 is a block diagram showing the circuit configuration of a power supply device relating to this disclosure and a diagram showing an example of the area occupied by the circuit. Figure 7 is a diagram showing an example of the A / D conversion result of a magnetic power supply device and the count result of a power supply device relating to this disclosure. Figure 8 is a diagram showing an example of the output voltage of a power supply device relating to this disclosure converging. Figure 9 is a diagram showing an example of the output voltage of a power supply device relating to related technology and the output voltage of a power supply device relating to this disclosure. The power supply device relating to Embodiment 1 will be described with reference to Figures 5 to 9. The power supply device relating to Embodiment 1 is connected to, for example, the power supply of a display device. The power supply device may be used in other electrical appliances.

[0026] As shown in Figure 5, the power supply unit 500 according to Embodiment 1 differs from the power supply unit 100 according to related technologies in that it includes an optical voltage conversion unit 501 and a feedback circuit 502. The optical voltage conversion unit 501 is connected to the power transmission unit 102 and includes an optical isolator that transmits the voltage signal of the output stage to the feedback circuit 502 while isolating it. As mentioned above, the optical isolator includes a combination of a light-emitting element and a light-receiving element. The feedback circuit 502 generates a control signal for switch control based on the voltage signal input from the optical isolator and outputs it to the switching circuit.

[0027] Furthermore, the feedback circuit 502 includes an A / D converter 503, a comparison circuit 504, a counter circuit 505, a P (subtraction / multiplication) arithmetic circuit comprising a result storage register 506, a target value register 507, a subtraction circuit 508, a subtraction result register 509, a coefficient register 510, and a multiplication circuit 511, and a PWM timer 512.

[0028] The output of the voltage conversion unit 501, which has passed through a general A / D converter 503, is evaluated by a comparison circuit 504. The comparison circuit 504 uses a comparator to binarize the output for evaluation. The results of the binary comparison are counted by a counter circuit 505 and integrated over the feedback period to obtain the difference relative to the target value. By inputting this result into an existing feedback circuit, a stable output can be obtained.

[0029] As shown in Figure 6, the A / D converter 503 converts the output analog signal into a digital signal. The comparison circuit 504 binarizes the output digital signal and makes a judgment. The counter circuit 505 counts the comparison results determined by the binarization. The counter circuit counts, for example, 3 positives, 4 negatives, etc. The result storage register 506 stores the counted result. The target value register 507 stores the target value, so the subtraction circuit 508 subtracts the counted result from the target value. The result of the subtraction is stored in the subtraction result register 509. A coefficient A specific to the circuit is stored in the coefficient register 510, so the multiplication circuit 511 multiplies the difference by the multiplier of coefficient A. The result of the multiplication is output to the PWM timer 512, which generates a control signal to control the switch. The control signal is transmitted to the switching circuit 101, which controls the output.

[0030] In this way, the count value is used as the difference from the target value. Furthermore, binary judgment is performed, the number of judgments is increased, and fluctuations in the output are detected by integrating the feedback period time.

[0031] As a result, the area of ​​the power supply unit 500 in this embodiment is 272 mm², comprising the voltage conversion unit 501 and the feedback circuit 502. 2 , with the switching circuit 101 and power transmission section 102, 560 mm 2 , total 832mm 2 The area of ​​the power supply unit 500 in this embodiment is 1388 mm², compared to the power supply unit 100 of the related technology. 2 It will become smaller than that.

[0032] As shown in Figure 7, the magnetic A / D conversion results yield analog values ​​of 5V, 10V, 5V, and 0V. The count result of this disclosure is expressed as the total number of count values ​​over a certain period. For example, in the first period, there are 5 high (H) and 5 low (L), so a value of 5V is obtained. In the next period, there are 10 highs, so a value of 10V is obtained. In the next period, there are 5 highs and 5 lows, so a value of 5V is obtained. In the next period, there are 10 lows, so a value of 0V is obtained. Thus, the magnetic method and the method of this disclosure yield the same value. The count is calculated by taking the time average.

[0033] The determination of whether it is high or low is done using a 12-bit A / D converter. 12-bit = 4095 = 10V 0 = 0V Therefore, we determine whether it is greater than or equal to 2048 or less. The count value for the first period was L because the first measurement was 2048 or less, the second measurement was L, and so on... After 10 measurements, it is calculated that there were 5 H and 5 L.

[0034] As shown in Figure 8, the output converges to the target value. If the counter value of the binary judgment result is positive, as in 1, the P operation circuit is calculated to lower the output, as in 2. If the output is lowered too much in the next unit of time, as in 3, it moves to raise it. Repeating this process, the output converges to be close to the target value, as in 4.

[0035] As shown in Figure 9, the waveform of the FB (Feedback) voltage in related technologies that use the A / D conversion value of a microcontroller directly as feedback repeatedly fluctuates between minimum and maximum values ​​and is not stable. When the A / D conversion value of a microcontroller is input to a comparator, the waveform of the FB voltage in this disclosure converges.

[0036] The above configuration provides a power supply device that includes a comparator circuit in the feedback circuit and employs an optical isolator in the voltage conversion section.

[0037] (Description of the power supply according to Embodiment 2) Figure 10 is a block diagram showing the circuit configuration of the power supply device according to this disclosure. Figure 11 is a block diagram showing the second circuit configuration of the power supply device according to this disclosure. The power supply device according to Embodiment 2 will be described with reference to Figures 10 and 11.

[0038] The feedback circuit 502 of the power supply unit 500 according to Embodiment 1 shown in Figure 10 operates by integrating the results of the A / D converter 503 over the feedback period. In this case, since the A / D converter conversion takes about 1 μs, a response time of about 50 μs was required.

[0039] This means that even if the delay outside the feedback circuit 104 were zero, it would be impossible to respond for 50 μs. Therefore, even if the output exceeds the target value, the output cannot be corrected until the next cycle, and a corresponding ripple occurs in the resulting output, as shown in the lower part of Figure 10.

[0040] As shown in Figure 11, since it is sufficient to produce a binary output, the feedback circuit 1101 of the power supply according to Embodiment 2 replaces the A / D converter 503 and comparison circuit 504 with a combination of a comparator and a D / A (digital-to-analog) converter 1102.

[0041] The comparator converts the signal into two values ​​based on the magnitude of its output. The D / A converter outputs a reference voltage to the comparator for binary determination. The counter circuit 505 counts the H or L signals output from the comparator.

[0042] The comparator operates at 50 ns compared to the A / D converter's speed of 1 μs, making it 20 times faster. This allows for a shorter response time to the PWM timer, reducing the ripple from 100 mVp-p to 5 mVp-p as shown in the table, and minimizing the output voltage fluctuation.

[0043] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of Symbols]

[0044] 100 Power supply unit, 101 Switching circuit, 102 Power transmission unit, 103 Voltage conversion unit, 104 Feedback circuit, 201 A / D converter, 202 Result storage register, 203 Target value register, 204 Subtraction circuit, 205 Subtraction result register, 206 Coefficient register, 207 Multiplication circuit, 208 PWM timer, 500 Power supply unit, 501 Voltage conversion unit, 502 Feedback circuit, 503 A / D converter, 504 Comparison circuit, 505 Counter circuit, 506 Result storage register, 507 Target value register, 508 Subtraction circuit, 509 Subtraction result register, 510 Coefficient register, 511 Multiplication circuit, 512 PWM timer, 1101 Feedback circuit, 1102 Comparator and D / A converter

Claims

1. A switching circuit that controls the input voltage with a switch to convert it into an output voltage, A power transmission unit that transmits the output voltage to the output stage, An optical isolator connected to the power transmission section transmits the voltage signal of the output stage to the feedback circuit while isolating it, The system includes a feedback circuit that generates a control signal for controlling the switch based on the voltage signal input from the optical isolator and outputs it to the switching circuit, The feedback circuit is a power supply that generates the control signal by a comparison circuit that binarizes the input voltage signal.

2. The aforementioned feedback circuit is A / D conversion circuit that converts the aforementioned voltage signal into a digital signal, The comparison circuit that determines the binary value of the digital signal, The power supply device according to claim 1, further comprising a counter circuit for counting the comparison results of the comparison circuit.

3. The aforementioned feedback circuit is The comparison circuit and D / A conversion circuit that binarize the voltage signal, The power supply device according to claim 1, further comprising a counter circuit for counting the binarized voltage signal.

4. The aforementioned feedback circuit further, A result storage register for storing the count result of the counter circuit, A target value register for storing the target value of the aforementioned count, A subtraction circuit that subtracts the count result from the target value, A subtraction result register for storing the result of the subtraction, A coefficient register for storing the multiplier for the subtraction, A multiplication circuit that multiplies the result of the subtraction by the multiplier, The power supply device according to claim 2 or 3, further comprising a PWMTimer that converts the result of the multiplication circuit into a PWM (Pulse Width Modulator) control signal.

5. The power supply device according to claim 1, wherein the optical isolator is a combination of a light-emitting element and a light-receiving element.

6. A power supply device according to claim 1, connected to a display device.

Images