Voltage amplifier circuit, switching power supply device, and initial setting method for switching power supply device

Abstract

To provide a voltage amplification circuit whose input / output characteristics become a relation of a straight line passing an original point and which facilitates fine adjustment of a gain, a switching power supply using the same, and an initial setting method therefor.SOLUTION: A voltage amplification circuit 22(1) comprises: an operational amplifier 24(1); a first resistor 26(1) which is connected between a Q point and an inverted input terminal; and a second resistor 28(1) which is connected between the inverted input terminal and an output terminal. The voltage amplification circuit also comprises: a third resistor 30(1) which is connected between a P point and a non-inverted input terminal; and a fourth resistor 32(1) whose one end is connected to the non-inverted input terminal. The voltage amplification circuit also comprises: a voltage feedback unit 34(1) by which a feedback voltage k Vzo (k is a coefficient equal to or less than 1) in proportion to an amplification voltage Vzo is generated and applied to the other end of the fourth resistor 32(1). The voltage feedback unit 34(1) changes setting of the coefficient k on the basis of an externally inputted digital signal DS. Input / output characteristics of the voltage amplification circuit 22(1) become a relation of a straight line passing an original point, and an inclination (gain G) of the straight line can be adjusted by changing the setting of the coefficient k from the outside.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a voltage amplifier circuit, a switching power supply device using the same, and an initial setting method for the switching power supply device. [Background technology]

[0002] Conventionally, in switching power supplies, in order to detect the output voltage Vo or the output current Io, a voltage corresponding to the output voltage Vo or a signal obtained by converting the output current Io into a voltage is amplified using a voltage amplifier circuit. For example, FIG. 1 of Patent Document 1 describes a configuration in which a shunt resistor is inserted in the output line of a DC-DC converter and the output current Io is detected by amplifying the voltage across the shunt resistor using a differential amplifier or the like. Also, FIG. 14A of Patent Document 1 describes a technology in which two series resistors are connected to the output terminals of a differential amplifier and the connection of the high-side resistor is switched using a switch to change the output voltage of the differential amplifier (effectively, a technology to change the gain of the differential amplifier).

[0003] Another common technique is to apply a bias voltage Vb to a specific point in a differential amplifier circuit to shift the input / output characteristics, as shown in FIG. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-141538 Summary of the Invention [Problem to be solved by the invention]

[0005] When a voltage amplifier circuit (or a switching power supply device equipped with the same) is mass-produced, there is a problem that variations in the characteristics of internal components can cause individual differences in the gain G of the voltage amplifier circuit. Therefore, in order to detect the output voltage Vo and output current Io with a certain level of accuracy or higher, it is necessary to fine-tune the gain G after assembling the voltage amplifier circuit to correct for individual differences.

[0006] However, the differential amplifier shown in FIG. 1 of Patent Document 1 does not have a function to adjust the gain G. The circuit shown in FIG. 14A of Patent Document 1 switches the gain G of the differential amplifier between two stages, and does not allow fine adjustment of the gain G.

[0007] 7 allows fine adjustment of the input / output characteristics of the differential amplifier circuit by adjusting the bias Vb. However, it is difficult to use this technique as a voltage amplifier circuit for a switching power supply.

[0008] When detecting the output voltage Vo and output current Io in a switching power supply, it is convenient if the input / output characteristics of the voltage amplifier circuit, i.e., the relationship between the input voltage (voltage to be amplified Vzi) and the output voltage (amplified voltage Vzo), is a straight line passing through the origin (Vzo = G Vz1).

[0009] In particular, when it is desired to accurately detect the output current Io from zero amperes to large values, it is preferable that the input / output characteristics be such that the amplified voltage Vzo is exactly zero volts when the output current Io is zero amperes, and that the amplified voltage Vzo is exactly a predetermined finite value when the output current Io is large. However, because the technique shown in Fig. 7 shifts (translates) the line of the input / output characteristics, adjusting and matching the amplified voltage Vzo when the output current Io is large may result in a deviation from the amplified voltage Vzo when the output current Io is zero amperes.

[0010] The same issue applies when you want to accurately detect the output current Vo from zero volts to large values: if you adjust the amplified voltage Vzo when the output voltage Vo is large, there is a possibility that the amplified voltage Vzo when the output voltage Vo is zero volts will be off. Therefore, the technology shown in Figure 7 is difficult to use as a voltage amplifier circuit for a switching power supply.

[0011] The present invention has been made in view of the above-mentioned background art, and has as its object to provide a voltage amplifier circuit in which the input / output characteristics are in a linear relationship passing through the origin and in which fine adjustment of the gain is easy, a switching power supply device using the same, and an initial setting method for the same. [Means for solving the problem]

[0012] The present invention provides a voltage amplifier circuit that amplifies the input voltage Vzi to be amplified and outputs an amplified voltage Vzo(≧0), the voltage being generated between point P and point Q in a circuit network, and is obtained by subtracting the voltage Vqg (Vpg≧Vqg≧0) of point Q relative to ground from the voltage Vpg (Vpg≧0) of point P relative to ground, an operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, and outputting an amplified voltage Vzo from the output terminal; a first resistor connected between the point Q and the inverting input terminal; a second resistor connected between the inverting input terminal and the output terminal; a third resistor connected between the point P and the non-inverting input terminal; a fourth resistor having one end connected to the non-inverting input terminal; and a voltage feedback section which generates a feedback voltage k·Vzo (k is a coefficient of 1 or less) which is a voltage with respect to the ground and is proportional to the amplified voltage Vzo, and applies the feedback voltage to the other end of the fourth resistor; the first resistor and the third resistor are resistor elements having the same nominal resistance value, the second resistor and the fourth resistor are resistor elements having the same nominal resistance value, and the voltage feedback unit has a function of performing arithmetic processing based on an externally input digital signal to change the setting of the coefficient k, The relationship between the voltage to be amplified Vzi and the amplified voltage Vzo satisfies Vzo=G·Vzi (G is a positive coefficient), and the value of the coefficient G can be adjusted by externally changing the setting of the coefficient k.

[0013] For example, the voltage feedback unit may include a high-side resistor having one end connected to the output terminal, a low-side resistor connected between the high-side resistor and the ground, an auxiliary circuit connected in parallel with the low-side resistor and consisting of a series circuit of an auxiliary resistor and a switching element, a switching control unit that turns the switching element on and off at a predetermined duty and performs arithmetic processing based on an externally input digital signal to change the duty setting, and a smoothing capacitor connected in parallel with the low-side resistor and across it to generate the feedback voltage k·Vzo that varies depending on the duty, wherein the value of the coefficient k can be changed by changing the duty setting. In this case, the voltage feedback unit may include a voltage buffer, and the feedback voltage k·Vzo generated in the smoothing capacitor may be applied to the other end of the fourth resistor via the voltage buffer. Alternatively, the voltage feedback unit may include an A / D converter that converts the amplified voltage Vzo into a digital signal and outputs it, a calculation unit that performs calculation processing based on the output of the A / D converter and an externally input digital signal to determine the coefficient k and the feedback voltage k·Vzo, and a D / A converter that generates the feedback voltage k·Vzo based on the determination by the calculation unit.

[0014] others, A voltage amplifier circuit that sets a voltage at a point P in a circuit network having a ground as a voltage to be amplified Vzi (Vzi≧0), amplifies the input voltage to be amplified Vzi, and outputs an amplified voltage Vzo (≧0), an operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, and outputting an amplified voltage Vzo from the output terminal; a fifth resistor connected between the point P and the non-inverting input terminal; a sixth resistor connected between the non-inverting input terminal and the ground; a seventh resistor connected between the inverting input terminal and the output terminal; an eighth resistor having one end connected to the inverting input terminal; and a variable resistor circuit connected between the eighth resistor and the ground, The variable resistance circuit has a function of changing the setting of its own effective resistance value Rk by performing arithmetic processing based on an externally input digital signal, and the relationship between the voltage to be amplified Vzi and the amplified voltage Vzo satisfies Vzo=G·Vzi (k is a positive coefficient), and the value of the coefficient G can be adjusted by externally changing the setting of the effective resistance value Rk. There is .

[0015] The variable resistance circuit Eighth resistance a low-side resistor connected between the other end of the resistor and ground; an auxiliary circuit connected in parallel to the low-side resistor and consisting of a series circuit of an auxiliary resistor and a switching element; and a circuit that turns on and off the switching element at a predetermined duty, and performs arithmetic processing based on an externally input digital signal. hand a switching control unit that changes the setting of the duty; and a smoothing capacitor that is connected in parallel to the low-side resistor and generates a DC voltage across both ends that changes according to the value of the duty, Effective It is preferable that the resistance value Rk can be changed by changing the duty setting.

[0016] others, A voltage amplifier circuit that sets a voltage at a point P in a circuit network having a ground as a voltage to be amplified Vzi (Vzi≧0), amplifies the input voltage to be amplified Vzi, and outputs an amplified voltage Vzo (≧0), an operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, the inverting input terminal being connected to the output terminal and outputting an amplified voltage Vzo from the output terminal; a ninth resistor connected between the point P and the non-inverting input terminal; a tenth resistor having one end connected to the non-inverting input terminal; and a variable resistor circuit connected between the other end of the tenth resistor and the ground; the variable resistance circuit has a function of performing arithmetic processing based on an externally input digital signal to change the setting of its own effective resistance value Rk, A voltage amplifier circuit in which the relationship between the voltage to be amplified Vzi and the amplified voltage Vzo satisfies Vzo=G·Vzi (k is a positive coefficient), and the value of the coefficient G can be adjusted by externally changing the setting of the effective resistance value Rk. There is .

[0017] The variable resistance circuit includes a low-side resistor inserted between the tenth resistor and ground, an auxiliary circuit connected in parallel to the low-side resistor and consisting of a series circuit of an auxiliary resistor and a switching element, and a circuit that turns on and off the switching element at a predetermined duty, and performs arithmetic processing based on an externally input digital signal. hand a switching control unit that changes the setting of the duty; and a smoothing capacitor that is connected in parallel to the low-side resistor and generates a DC voltage across both ends that changes according to the value of the duty, Effective It is preferable that the resistance value Rk can be changed by changing the duty setting.

[0018] The present invention also provides The above voltage amplifier circuit a power conversion circuit that converts an input voltage into a DC output voltage Vo and outputs the converted voltage; and a control circuit that controls the operation of the power conversion circuit, wherein the voltage amplifier circuit is connected so that the output voltage Vo of the power conversion circuit becomes the voltage to be amplified Vzi, and the amplified voltage Vzo output by the voltage amplifier circuit is used to control the power conversion circuit as a detection signal for the output voltage Vo.

[0019] The present invention also provides an initial setting method for this switching power supply, which includes measuring the value of the amplified voltage Vzo when a known voltage Vzi to be amplified is input to the voltage amplifier circuit, externally adjusting the setting of the coefficient G so that the value of the amplified voltage Vzo falls within a specified range, and rewriting the program of the voltage amplifier circuit so that the state after adjustment becomes the default setting.

[0020] The present invention also provides The above voltage amplifier circuita power conversion circuit that converts an input voltage into a DC output voltage Vo and outputs the converted voltage; a current detection resistor through which a voltage drop occurs when an output current Io output from the power conversion circuit to a load flows; and a control circuit that controls the operation of the power conversion circuit, wherein the voltage amplifier circuit is connected so that the voltage drop occurring in the current detection resistor becomes the voltage to be amplified Vzi, and the amplified voltage Vzo output by the voltage amplifier circuit is used to control the power conversion circuit as a detection signal for the output current Io.

[0021] The present invention also provides an initial setting method for this switching power supply, which includes measuring the value of the amplified voltage Vzo when a known voltage Vzi to be amplified is input to the voltage amplifier circuit, externally adjusting the setting of the coefficient G so that the value of the amplified voltage Vzo falls within a specified range, and rewriting the program of the voltage amplifier circuit so that the state after adjustment becomes the default setting. [Effects of the Invention]

[0022] The voltage amplifier circuit of the present invention has an input / output characteristic that is a straight line passing through the origin, and the gain can be easily fine-tuned. Voltage feedback section ) performs arithmetic processing based on digital signals to adjust the gain, so a highly intelligent voltage amplifier circuit can be obtained. Voltage feedback section ) is connected to ground, it is possible to minimize the effects of noise entering through the signal lines for digital signal input.

[0023] By using the voltage amplifier circuit with the excellent performance described above, the switching power supply device of the present invention can detect the output voltage or output current with high accuracy and can be used for various controls. Furthermore, by executing the initial setting method for the switching power supply device of the present invention, individual differences in gain G caused by variations in the characteristics of the internal components of the voltage amplifier circuit can be corrected by rewriting the program, making it easy to achieve the desired performance. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a circuit diagram showing a first embodiment of a switching power supply device according to the present invention; [Figure 2] 2A is a circuit diagram showing the voltage amplifier circuit (first embodiment of the voltage amplifier circuit of the present invention) in FIG. 1, and FIG. 2B is a graph showing the input / output characteristics of this voltage amplifier circuit. [Figure 3] 3A is a circuit diagram showing a specific internal configuration of the voltage feedback section in FIG. 2, and FIG. 3B is a graph showing changes in the effective resistance value Rk and coefficient k when the duty D is changed. [Figure 4] 1 is a circuit diagram showing one embodiment of a switching power supply device; [Figure 5] 5A is a circuit diagram showing one form of the voltage amplifier circuit in FIG. 4, and FIG. 5B is a graph showing the input / output characteristics of this voltage amplifier circuit. [Figure 6] 5A is a circuit diagram showing a modified example of the voltage amplifier circuit in FIG. 4, and FIG. 5B is a graph showing the input / output characteristics of this voltage amplifier circuit. [Figure 7] 1A is a circuit diagram showing a conventional differential amplifier circuit, and FIG. 1B is a graph showing the input / output characteristics of this differential amplifier circuit. DETAILED DESCRIPTION OF THE INVENTION

[0025] <Switching power supply device 10 and voltage amplifier circuits 22(1), 22(2) of the first embodiment> A first embodiment of a switching power supply and a voltage amplifier circuit of the present invention will now be described with reference to Figures 1 to 3. A switching power supply 10 of this embodiment includes a power conversion circuit 14 that converts an input voltage supplied from an input power supply 12 into a DC output voltage Vo and outputs the converted voltage, and a control circuit 18 that controls the operation of the power conversion circuit 14. The switching power supply 10 also includes a current detection resistor 20 through which a voltage drop occurs when an output current Io that is output from the power conversion circuit 14 to a load 16 flows, and voltage amplifier circuits 22(1) and 22(2) of the first embodiment.

[0026] When the high-voltage side of the two output terminals of the power conversion circuit 14 is designated as point P1 and the low-voltage side as point Q1, the output voltage Vo generated between point P1 and point Q1 becomes the voltage to be amplified Vzi(1), and the voltage amplifier circuit 22(1) amplifies this to generate an amplified voltage Vzo(1) and outputs it to the control circuit 18. The amplified voltage Vzo(1) is then used to control the power conversion circuit 14 as a detection signal for the output voltage Vo.

[0027] Furthermore, when the high-voltage side of both ends of the current detection resistor 20 is defined as point P2 and the low-voltage side as point Q2, the voltage drop across the current detection resistor 20 that occurs between point P2 and point Q2 becomes the voltage to be amplified Vzi(2), and the voltage amplifier circuit 22(2) amplifies this to generate an amplified voltage Vzo(2) and outputs it to the control circuit 18. The amplified voltage Vzo(2) is then used to control the power conversion circuit 14 as a detection signal for the output current Io.

[0028] The internal configurations of the voltage amplifier circuits 22(1) and 22(2) are similar, so the configuration of the voltage amplifier circuit 22(1) will be mainly described here.

[0029] The voltage amplifier circuit 22(1) is a type of so-called differential amplifier circuit, and as shown in FIG. 2(a), it sets the voltage Vzi (Vzi≧0) to be amplified as the voltage obtained by subtracting the voltage Vqg (Vpg≧Vqg≧0) at point Q1 relative to ground from the voltage Vpg (Vpg≧0) at point P1 relative to ground, and amplifies the input voltage Vzi to be amplified and outputs the amplified voltage Vzo (≧0).

[0030] The voltage amplifier circuit 22(1) includes an operational amplifier 24(1) having an inverting input terminal, a non-inverting input terminal, and an output terminal, and outputting an amplified voltage Vzo(1) from the output terminal. A first resistor 26(1) (resistance value R1) is connected between point Q1 and the inverting input terminal, and a second resistor 28(1) (resistance value R2) is connected between the inverting input terminal and the output terminal. A third resistor 30(1) (resistance value R1) is connected between point P1 and the non-inverting input terminal, one end of a fourth resistor 32(1) (resistance value R2) is connected to the non-inverting input terminal, and a voltage feedback unit 34(1) is connected between the other end of the fourth resistor 32(1) and the output terminal.

[0031] The voltage feedback unit 34(1) is a block that generates a feedback voltage k·Vzo (k is a coefficient of 1 or less), which is a voltage with respect to ground and is proportional to the amplified voltage Vzo, and applies this to the other end of the fourth resistor 32(1). The coefficient k is set by default based on the duty D, which will be described later, and the setting of the coefficient k can be changed by performing arithmetic processing based on an externally input digital signal DS.

[0032] 3(a), the voltage feedback section 34(1) includes a high-side resistor 36(1) (resistance value Ra) connected at one end to the output terminal of the operational amplifier 24(1), and a low-side resistor 38(1) (resistance value Rb) connected between the high-side resistor 36(1) and ground. An auxiliary circuit 44(1) consisting of a series circuit of an auxiliary resistor 40(1) (resistance value Rc) and a switching element 42(1) is connected to both ends of the low-side resistor 38(1).

[0033] A switching control unit 46(1) that turns the switching element 42(1) on and off is connected to the drive terminal of the switching element 42(1). The switching control unit 46(1) turns the switching element 42(1) on and off with a default duty D, but also has the function of changing the setting of the duty D by performing arithmetic processing based on an externally input digital signal DS.

[0034] A smoothing capacitor 48(1) is connected in parallel to both ends of the low-side resistor 38(1), and generates a DC feedback voltage k·Vzo that changes according to the value of the duty cycle D. Furthermore, a voltage buffer 50(1) is provided, which applies the feedback voltage k·Vzo generated in the smoothing capacitor 48(1) to the other end of the fourth resistor 32(1).

[0035] Next, the operation of the voltage amplifier circuit 22(1) will be described. The input / output characteristics of the voltage amplifier circuit 22(1) are expressed by a straight line passing through the origin, as shown in equation (1). The gain G in equation (1) is determined based on equations (2) to (4). Here, Rk in equations (3) and (4) is the effective resistance value obtained by combining the resistance values ​​of the low-side resistor 40(1) [resistance value Rb] and the auxiliary resistor 40(1) [resistance value Rc]. Vzo(1)=G·Vzi(1) (1) G = (R2 ÷ R1) k (2) k = Rk ÷ (Ra + Rk) (3) Rk=Rb / / (Rc÷D) (4) As shown in equation (2), the gain G and the coefficient k are approximately directly proportional to each other, so the gain G can be adjusted by changing the coefficient k. Furthermore, as shown in equation (3), the coefficient k can be adjusted by changing the effective resistance value Rk. And, as shown in equation (4), the value of the effective resistance value Rk can be adjusted by changing the duty cycle D.

[0036] The upper graph in Figure 3(b) is a graph of equation (4). For example, when D = 100%, the switching element 42(1) is fixed to ON, so Rk = Rb / / Rc. When D = 0%, the switching element 42(1) is fixed to OFF, so Rk = Rb. Therefore, by changing the duty D within the range of 0 to 100%, the effective resistance value Rk can be changed within the range of Rb to (Rb / / Rc).

[0037] The lower graph in Figure 3(b) shows the relationship between the coefficient k and the duty cycle D when the effective resistance value Rk in equation (4) is substituted into equation (3). As can be seen from this graph, by changing the duty cycle D in the range of 0 to 100%, the coefficient k can be adjusted in the range of Rb÷(Ra+Rb) to (Rb / / Rc)÷[Ra+(Rb / / Rc)].

[0038] From the above, the input / output characteristics of the voltage amplifier circuit 22(1) are a straight line passing through the origin, as shown in FIG. 2(b), and the slope of the line (gain G) can be adjusted by changing the duty D.

[0039] When switching power supply devices 10 are mass-produced, individual differences occur in gain G due to variations in the characteristics of the internal components of voltage amplifier circuit 22(1). Therefore, it is advisable to implement the following initial setting method (one embodiment of the initial setting method for a switching power supply device of the present invention) in the manufacturing process of switching power supply device 10.

[0040] First, a known voltage to be amplified Vzi(1) is input to the voltage amplifier circuit 22(1), and the value of the amplified voltage Vzo(1) at that time is measured. If the value of the amplified voltage Vzo(1) is within a specified range, the initial setup process is complete. However, if it is not within the specified range, a digital signal DS is sent to the switching control unit 46(1), and the duty D setting is adjusted so that the value of the amplified voltage Vzo(1) is within the specified range. Then, the program of the switching control unit 46(1) is rewritten so that the adjusted duty D becomes the default setting. By performing this initial setup process for each voltage amplifier circuit 22(1), individual differences in gain G can be reliably corrected.

[0041] So far, the configuration, operation, and initial setting method of the voltage amplifier circuit 22(1) have been explained, but the same applies to the voltage amplifier circuit 22(2).

[0042] As described above, the input / output characteristics of the voltage amplifier circuits 22(1) and 22(2) are linearly related through the origin, and fine adjustment of the gain is easy. Furthermore, the gain-adjusting voltage feedback unit 34(1) adjusts the gain by performing arithmetic processing based on a digital signal, resulting in highly intelligent voltage amplifier circuits 22(1) and 22(2). Furthermore, because the voltage feedback unit 34(1) is configured to be connected to ground, the effects of noise entering the voltage amplifier circuits 22(1) and 22(2) through the signal line for inputting the digital signal DS can be minimized.

[0043] By using the excellent performance voltage amplifier circuits 22(1) and 22(2), the switching power supply device 10 can detect the output voltage Vo and output current Io with high accuracy and can be used for various controls. Furthermore, by executing the above initial setting method, individual differences in gain G caused by variations in the characteristics of the internal components of the voltage amplifier circuits 22(1) and 22(2) can be corrected by rewriting the program, making it possible to easily achieve the desired performance.

[0044] Voltage feedback unit 34(1) is a block that receives Vzo as input and outputs feedback voltage k·Vzo, and is characterized by a configuration in which the coefficient k is adjusted by changing the on / off duty D of switching element 42(1). This configuration means that the part of switching control unit 46(1) that performs digital arithmetic processing (arithmetic unit) is provided within a digital processor, but has the advantage that feedback voltage k·Vzo can be generated with high resolution even when an inexpensive general-purpose digital processor is used.

[0045] Alternatively, the voltage feedback section can be configured as a combination of an A / D converter, a calculation section, and a D / A converter. In this case, the coefficient k used in the calculation section is directly adjusted (changed), which has the advantage of eliminating the need for discrete components such as the switching element 42(1). However, care must be taken when increasing the resolution of the feedback voltage k·Vzo, as this will require a very expensive high-speed digital processor.

[0046] < Switching power supply 52 and voltage amplifier circuits 54(1), 54(2)> next, Switching Power Supply and voltage amplifier circuit A form of 4 and 5. Here, the same components as those in the switching power supply device 10 described above are given the same reference numerals and the description thereof will be omitted.

[0047] This form As shown in FIG. 4, the switching power supply device 52 includes the same power conversion circuit 14, control circuit 18, and current detection resistor 20 as those described above, but the voltage amplifier circuits 22(1) and 22(2) are replaced with new voltage amplifier circuits 54(1) and 54(2).

[0048] The voltage amplifier circuit 54(1) uses the high-voltage side of the two output terminals of the power conversion circuit 14 as point P1 and the low-voltage side as ground, and the output voltage Vo generated at point P1 becomes the voltage to be amplified Vzi(1), which is amplified to generate an amplified voltage Vzo(1) and output to the control circuit 18. The amplified voltage Vzo(1) is then used to control the power conversion circuit 14 as a detection signal for the output voltage Vo.

[0049] The voltage amplifier circuit 54(2) uses the high-voltage side of the current detection resistor 20 as point P2 and the low-voltage side as ground, and the voltage drop across the current detection resistor 20 that occurs at point P2 becomes the voltage to be amplified Vzi(2), which is amplified to generate an amplified voltage Vzo(2) and output to the control circuit 18. The amplified voltage Vzo(2) is then used to control the power conversion circuit 14 as a detection signal for the output current Io.

[0050] The internal configurations of the voltage amplifier circuits 54(1) and 54(2) are similar, so the configuration of the voltage amplifier circuit 54(1) will be mainly described here.

[0051] The voltage amplifier circuit 54(1) is a type of so-called inverting amplifier circuit, and as shown in FIG. 5(a), the voltage at point P1 with respect to ground is the voltage to be amplified Vzi (Vzi≧0), and the input voltage to be amplified Vzi is amplified and output as an amplified voltage Vzo (≧0).

[0052] The voltage amplifier circuit 54(1) includes an operational amplifier 56(1) having an inverting input terminal, a non-inverting input terminal, and an output terminal, and outputting an amplified voltage Vzo(1) from the output terminal. A fifth resistor 58(1) [resistance value R5] is connected between point P1 and the non-inverting input terminal, and a sixth resistor 60(1) [resistance value R6] is connected between the non-inverting input terminal and ground. A seventh resistor 62(1) [resistance value R7] is connected between the inverting input terminal and the output terminal. One end of an eighth resistor 64(1) [resistance value R8] is connected to the inverting input terminal, and a variable resistor circuit 66(1) is connected between the other end of the eighth resistor 64(1) and ground.

[0053] The variable resistance circuit 66(1) is a circuit whose own resistance value (effective resistance value Rk) changes. The effective resistance value Rk is set as a default based on the duty D described below, and the setting of the effective resistance value Rk can be changed by performing arithmetic processing based on an externally input digital signal DS.

[0054] The internal configuration of the variable resistance circuit 66(1) will be described. The variable resistance circuit 66(1) includes a low-side resistor 68(1) [resistance value Rb] connected between the other end of the eighth resistor 64(1) and ground, and an auxiliary circuit 74(1) consisting of a series circuit of an auxiliary resistor 70(1) [resistance value Rc] and a switching element 72(1) is connected to both ends of the low-side resistor 68(1).

[0055] A switching control unit 76(1) that turns the switching element 72(1) on and off is connected to the drive terminal of the switching element 72(1). The switching control unit 76(1) turns the switching element 72(1) on and off with a default set duty D, but also has a function of changing the setting of duty D by performing arithmetic processing based on an externally input digital signal DS. A smoothing capacitor 78(1) that smoothes the voltage across the low-side resistor 68(1) to convert it into a DC voltage is connected in parallel to both ends of the low-side resistor 68(1).

[0056] Next, the operation of the voltage amplifier circuit 54(1) will be described. The input / output characteristics of the voltage amplifier circuit 54(1) are expressed by a straight line passing through the origin, as shown in equation (5). The gain G in equation (5) is determined based on equations (6) and (7). Vzo(1)=G·Vzi(1) (5) G=[1+R7÷(R8+Rk)]·R6÷(R5+R6) (6) Rk=Rb / / (Rc÷D) (7) As shown in equation (6), the gain G can be adjusted by changing the effective resistance Rk. Also, as shown in equation (7), the effective resistance Rk is a combined value of the resistances of the low-side resistor 68(1) [resistance Rb] and the auxiliary resistor 70(1) [resistance Rc], and can be adjusted by changing the duty D.

[0057] The upper graph in FIG. 3(b) explained above is a graph of equation (4), and equation (7) also has a similar graph. For example, when D=100%, switching element 72(1) is fixed to ON, so Rk=Rb / / Rc. Also, when D=0%, switching element 72(1) is fixed to OFF, so Rk=Rb. Therefore, by changing the duty D within the range of 0 to 100%, the effective resistance value Rk can be changed within the range of Rb to (Rb / / Rc).

[0058] From the above, the input / output characteristics of the voltage amplifier circuit 54(1) are represented by a straight line passing through the origin as shown in FIG. 5(b), and the slope of the line (gain G) can be adjusted by changing the duty D.

[0059] When switching power supply devices 52 are mass-produced, individual differences occur in gain G due to variations in the characteristics of the internal components of voltage amplifier circuit 54(1). Therefore, it is advisable to implement the same initial setting method as described above (one embodiment of the initial setting method for a switching power supply device of the present invention) in the manufacturing process of switching power supply device 52.

[0060] First, a known voltage to be amplified Vzi(1) is input to the voltage amplifier circuit 54(1), and the value of the amplified voltage Vzo(1) is measured. If the value of the amplified voltage Vzo(1) is within a specified range, the initial setup process is complete. However, if it is not within the specified range, a digital signal DS is sent to the switching control unit 76(1), and the duty D setting is adjusted so that the value of the amplified voltage Vzo(1) is within the specified range. Then, the program of the switching control unit 76(1) is rewritten so that the adjusted duty D becomes the default setting. By performing this initial setup process for each voltage amplifier circuit 54(1), individual differences in gain G can be reliably corrected.

[0061] So far, the configuration, operation, and initial setting method of the voltage amplifier circuit 54(1) have been explained, but the same applies to the voltage amplifier circuit 54(2).

[0062] As explained above, This form The voltage amplifier circuits 54(1), 54(2) and the switching power supply device 52 can also provide the same effects as the voltage amplifier circuits 22(1), 22(2) and the switching power supply device 10 described above.

[0063] < Other forms , modified examples etc. The voltage amplifier circuit of the present invention is not limited to the above embodiment. For example, the voltage amplifier circuit 22(1) is provided with a voltage buffer 50(1). However, if the impedance on the side of the fourth resistor 32(1) seen from the output terminal of the voltage buffer 50(1) is sufficiently higher than the impedance on the side of the smoothing capacitor 48(1) seen from the input terminal of the voltage buffer 50(1), equations (1) to (4) hold even if the voltage buffer 50(1) is omitted (short-circuit removed). Therefore, the voltage buffer 50(1) can be eliminated if the relationship between the impedances of the upstream and downstream stages satisfies certain conditions. The same applies to the voltage amplifier circuit 22(2).

[0064] The voltage amplifier circuit 54(1) can be replaced with a modified voltage amplifier circuit 80(1) shown in FIG. 6(a). The voltage amplifier circuit 80(1) is , similar to the voltage amplifier circuit 54(1), is a type of non-inverting amplifier circuit, and as shown in FIG. 6(a), the voltage at point P1 relative to ground is the voltage to be amplified Vzi (Vzi≧0), and the input voltage to be amplified Vzi is amplified and output as the amplified voltage Vzo (≧0).

[0065] The voltage amplifier circuit 80(1) includes an operational amplifier 82(1) having an inverting input terminal, a non-inverting input terminal, and an output terminal, and outputs an amplified voltage Vzo(1) from the output terminal. A ninth resistor 84(1) [resistance value R9] is connected between point P1 and the non-inverting input terminal, and the input terminal and output terminal are connected. In addition, a tenth resistor 86(1) [resistance value R10] is connected to the non-inverting input terminal, and a variable resistance circuit 66(1) is connected between the other end of the tenth resistor 86(1) and ground.

[0066] The variable resistance circuit 66(1) is similar to the variable resistance circuit 66(1) in FIG. 5(a), and the effective resistance value Rk is set as a default based on the duty D. The switching control unit 76(1) performs arithmetic processing based on the digital signal DS, thereby enabling the setting of the effective resistance value Rk to be changed.

[0067] To explain the operation of the voltage amplifier circuit 80(1), the input / output characteristics of the voltage amplifier circuit 80(1) are expressed by a straight line passing through the origin, as shown in equation (8). The gain G in equation (8) is determined based on equations (9) and (10). Vzo(1)=G·Vzi(1) (8) G = (R10 + Rk) ÷ (R9 + R10 + Rk) (9) Rk=Rb / / (Rc÷D) (10) As shown in equation (9), the gain G can be adjusted by changing the effective resistance Rk, and as shown in equation (7), the value of the effective resistance Rk can be adjusted by changing the duty D.

[0068] The upper graph in FIG. 3(b) explained above is a graph of equation (4), and equation (10) also has a similar graph. For example, when D=100%, switching element 72(1) is fixed to ON, so Rk=Rb / / Rc. Also, when D=0%, switching element 72(1) is fixed to OFF, so Rk=Rb. Therefore, by changing the duty D within the range of 0 to 100%, the effective resistance value Rk can be changed within the range of Rb to (Rb / / Rc).

[0069] From the above, the input / output characteristics of the voltage amplifier circuit 80(1) are represented by a straight line passing through the origin as shown in Figure 6(b), and the gain G, which is the slope of the line, can be adjusted by changing the duty D. Therefore, even if the voltage amplifier circuit 54(1) is replaced with the voltage amplifier circuit 80(1), the same effects can be obtained.

[0070] Furthermore, it goes without saying that the voltage amplifier circuit of the present invention is highly versatile and can be used for purposes other than switching power supplies.

[0071] The switching power supply device of the present invention is not limited to the above embodiment. For example, in the case of the switching power supply device 10, two sets of voltage amplifier circuits with the same configuration are mounted to detect the output voltage Vo and the output current Io. Among the above voltage amplifier circuits 22(1), 54(1), and 80(1), , including a voltage amplifier circuit 22(1) Two sets may be selected and installed. Also, if only one of the output voltage Vo and output current Io is to be detected, a voltage amplifier circuit 22(1) Only one set needs to be installed.

[0072] The initial setting method for the switching power supply device of the present invention is not limited to the above embodiment. For example, in the above description, it was stated that "duty D is set as a default in the switching control unit 46(1)." However, it is not necessarily required to set it as a default. For example, when performing the initial setting work, the initial duty D may be set by a digital signal from an external device, and the duty D after adjustment may be set by the switching control unit 46(2). It may be written into the program of 46(1). [Explanation of symbols]

[0073] 10,52 Switching power supply 14 Power Conversion Circuit 18 Control circuit 20 Current detection resistor 22(1), 22(2), 54(1), 54(2), 80(1) Voltage amplifier circuit 24(1),56(1),82(1) Op-amp 26(1) First resistance 28(1) Second resistor 30(1) Third resistance 32(1) Fourth resistor 34(1) Voltage feedback section 36(1) High-side resistor 38(1),68(1) Low side resistor 40(1),70(1) Auxiliary resistor 42(1),72(1) Switching element 44(1),74(1) Auxiliary circuit 46(1),76(1) Switching control section 48(1),78(1) Smoothing capacitor 50 Voltage Buffer 58(1) Fifth resistance 60(1) Sixth resistance 62(1) Seventh Resistance 64(1) Eighth Resistance 66(1) Variable Resistor Circuit 84(1) Ninth Resistance 86(1) Tenth Resistance D Duty G Gain Io output current k coefficient Rk Effective resistance Vo output voltage Vzi(1), Vz1(2) Voltage to be amplified Vzo(1), Vzo(2) Amplified voltage

Claims

1. A voltage amplifier circuit which amplifies the input voltage Vzi to be amplified and outputs an amplified voltage Vzo (≧0), wherein the voltage Vzi (Vzi≧0) is a voltage generated between a point P and a point Q in a circuit network, the voltage Vpg (Vpg≧0) at the point P relative to ground minus the voltage Vqg (Vpg≧Vqg≧0) at the point Q relative to ground, an operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, and outputting an amplified voltage Vzo from the output terminal; a first resistor connected between the Q point and the inverting input terminal; a second resistor connected between the inverting input terminal and the output terminal; a third resistor connected between the P point and the non-inverting input terminal; a fourth resistor having one end connected to the non-inverting input terminal; and a voltage feedback section which generates a feedback voltage k·Vzo (k is a coefficient of 1 or less) which is a voltage with respect to the ground and is proportional to the amplified voltage Vzo, and applies the feedback voltage to the other end of the fourth resistor; the first resistor and the third resistor are resistor elements having the same nominal resistance value, and the second resistor and the fourth resistor are resistor elements having the same nominal resistance value; the voltage feedback unit has a function of performing arithmetic processing based on an externally input digital signal to change the setting of the coefficient k, the relationship between the voltage to be amplified Vzi and the amplified voltage Vzo satisfies Vzo=G·Vzi (G is a positive coefficient), and the value of the coefficient G can be adjusted by externally changing the setting of the coefficient k; the voltage feedback section includes: a high-side resistor having one end connected to the output terminal; a low-side resistor connected between the high-side resistor and the ground; an auxiliary circuit connected in parallel to the low-side resistor and consisting of a series circuit of an auxiliary resistor and a switching element; a switching control section which turns the switching element on and off at a predetermined duty and performs arithmetic processing based on an externally input digital signal to change the setting of the duty; and a smoothing capacitor connected in parallel to the low-side resistor and which generates, across both ends, the feedback voltage k·Vzo which changes in accordance with the value of the duty, A voltage amplifier circuit, characterized in that the value of the coefficient k can be changed by changing the setting of the duty.

2. 2. The voltage amplifier circuit according to claim 1, wherein the voltage feedback section has a voltage buffer, and the feedback voltage k·Vzo generated in the smoothing capacitor is applied to the other end of the fourth resistor through the voltage buffer.

3. A voltage amplifier circuit which amplifies the input voltage Vzi to be amplified and outputs an amplified voltage Vzo (≧0), the voltage being generated between point P and point Q in a circuit network, and which is the voltage Vpg (Vpg≧0) of point P relative to ground minus the voltage Vqg (Vpg≧Vqg≧0) of point Q relative to ground, an operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, and outputting an amplified voltage Vzo from the output terminal; a first resistor connected between the Q point and the inverting input terminal; a second resistor connected between the inverting input terminal and the output terminal; a third resistor connected between the P point and the non-inverting input terminal; a fourth resistor having one end connected to the non-inverting input terminal; and a voltage feedback section which generates a feedback voltage k·Vzo (k is a coefficient of 1 or less) which is a voltage with respect to the ground and is proportional to the amplified voltage Vzo, and applies the feedback voltage to the other end of the fourth resistor; the first resistor and the third resistor are resistor elements having the same nominal resistance value, and the second resistor and the fourth resistor are resistor elements having the same nominal resistance value; the voltage feedback unit has a function of performing arithmetic processing based on an externally input digital signal to change the setting of the coefficient k, the relationship between the voltage to be amplified Vzi and the amplified voltage Vzo satisfies Vzo=G·Vzi (G is a positive coefficient), and the value of the coefficient G can be adjusted by externally changing the setting of the coefficient k; The voltage feedback unit comprises an A / D converter that converts the amplified voltage Vzo into a digital signal and outputs it, a calculation unit that performs calculation processing based on the output of the A / D converter and an externally input digital signal to determine the coefficient k and the feedback voltage k·Vzo, and a D / A converter that generates the feedback voltage k·Vzo based on the determination by the calculation unit.

4. a power conversion circuit for converting an input voltage into a DC output voltage Vo and outputting the converted voltage; and a control circuit for controlling the operation of the power conversion circuit; the voltage amplifier circuit is connected so that the output voltage Vo of the power conversion circuit becomes the amplified voltage Vzi, and the amplified voltage Vzo output by the voltage amplifier circuit is used to control the power conversion circuit as a detection signal for the output voltage Vo.

5. 5. The method for initializing a switching power supply according to claim 4, a setting of the coefficient G externally adjusted so that the value of the amplified voltage Vzo falls within a specified range; and a program for the voltage amplifier circuit is rewritten so that the state after adjustment becomes a default setting.

6. a power conversion circuit that converts an input voltage into a DC output voltage Vo and outputs the converted voltage; a current detection resistor through which a voltage drop occurs when an output current Io that is output from the power conversion circuit to a load flows; and a control circuit that controls the operation of the power conversion circuit, the voltage amplifier circuit is connected so that the voltage drop occurring across the current detection resistor becomes the amplified voltage Vzi, and the amplified voltage Vzo output by the voltage amplifier circuit is used to control the power conversion circuit as a detection signal for the output current Io.

7. 7. The method for initializing a switching power supply according to claim 6, a setting of the coefficient G externally adjusted so that the value of the amplified voltage Vzo falls within a specified range; and a program for the voltage amplifier circuit is rewritten so that the state after adjustment becomes a default setting.

Images