Dc-dc converter, semiconductor integrated circuit for power supply control, and power supply device

Abstract

Provided are: a control circuit (11) that controls a switching element or a transistor connected between a voltage input terminal and a voltage output terminal based on a potential difference between a feedback voltage proportional to an output voltage and a predetermined reference voltage; a current source circuit (15) that flows a predetermined current; a voltage correction circuit (41) that corrects the reference voltage or the feedback voltage; and a switching unit (SW1) that outputs the current of the current source circuit to the voltage output terminal based on a change in an active level of a signal for controlling execution / stop of circuit operation supplied from the outside, the voltage correction circuit determining a voltage correction amount based on information related to a resistance on a load side input from the outside when the current of the current source circuit is output.

Description

Technical Field

[0001] This invention relates to power supply devices for converting DC voltage, and for example to a technology for use in DC-DC converters and semiconductor integrated circuits for power control, wherein the DC-DC converter has the function of compensating for voltage drop in a cable supplying power to a load. Background Technology

[0002] A DC-DC converter using a switching regulator is included as a circuit that converts an input DC voltage to an output DC voltage at different potentials. This switching regulator DC-DC converter comprises: a switching element that applies a DC voltage supplied from a DC power source to an inductor (coil) to allow current to flow through the inductor and thus store energy; a rectifier element that rectifies the current in the inductor during the energy release period when the switching element is turned off; and a control circuit that controls the switching element to be turned on and off. Furthermore, in this switching regulator DC-DC converter, an error amplifier is used to detect the magnitude of the output voltage, and control is performed to extend the on-time of the switching element if the output voltage decreases, and to shorten the on-time if the output voltage increases.

[0003] There exist systems where a power supply device, such as a DC-DC converter, supplies power to a device that becomes a load via a cable. In such systems, if the length of the power supply cable increases, a voltage drop occurs due to the cable's resistance as current flows from the power supply device to the load, making it impossible to guarantee the required power voltage for the load device. Therefore, it is necessary to correct the output voltage on the power supply side. The power supply device consists of a semiconductor integrated circuit (hereinafter referred to as a power IC) and components such as capacitors and resistors connected to the power IC. The semiconductor integrated circuit has built-in switching elements for allowing current to flow through passive components such as inductors, and circuitry for generating signals to control the switching elements to turn on and off at appropriate timings.

[0004] Previously, the output voltage was pre-set high based on the assumption of a voltage drop caused by the power cable, or a circuit for voltage correction was set on the power IC side to detect the cable resistance when the cable was connected to correct the voltage, thereby correcting the output voltage in the DC-DC converter. Specifically, such as Figure 7 As shown, a current sensing resistor Rs is provided in the wiring connected to the power cable 21, and a voltage correction circuit 41 is provided. This voltage correction circuit 41 corrects the reference voltage VREF based on the voltage detected by the current sensing resistor Rs. The reference voltage VREF is a reference voltage compared with the output feedback voltage VFB input to the error amplifier 13 within the power supply IC. Furthermore, in Figure 7In this context, RL is the equivalent resistance of the device that becomes the load, Rc1 and Rc2 are the resistance components of cable 21, and ROVA is the external resistor used for voltage adjustment correction.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-85382

[0008] Patent Document 2: Japanese Patent Application Publication No. 2000-171270 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] After using Figure 7 In the existing DC-DC converters of the power supply IC shown, the voltage applied to the power terminals of the load device remains constant regardless of the output current. However, in this configuration, the voltage correction amount, determined by the resistance values ​​of the output voltage divider resistors Rb1 and Rb2 and the adjustment resistor ROVA, needs to be pre-set. Therefore, the information between the OUT1-OUT2 terminals (the resistance values ​​on the load side) must be considered in advance on the power supply IC side, leading to increased design time. Furthermore, the system designer needs to determine the value of the external adjustment resistor, and since an external resistor is required, the number of system components increases.

[0011] In addition, as an invention that provides an output voltage correction circuit for supplying high-precision voltage to the load device, there is, for example, the invention described in Patent Document 1.

[0012] However, the subject of the invention described in Patent Document 1 is to suppress the ripples that depend on the input voltage, inductor current, switching frequency, inductor value, and the series equivalent parasitic resistance of the output capacitor to keep the output voltage constant, which is different from the subject of this invention. Furthermore, the invention described in Patent Document 1 corrects the reference voltage of the error amplifier based on the output feedback voltage, without correcting the voltage according to the magnitude of the output current, which is different from this invention.

[0013] Furthermore, in systems that supply power to a load device via a cable, for example, Patent Document 2 describes an invention of a power supply circuit that addresses the issue of not needing to adjust the output voltage each time in response to voltage drops caused by cable wiring length. However, in the invention described in Patent Document 2, a power supply voltage level detection circuit is provided in the encoder, which is the load device, and the detected voltage information is sent to the power supply circuit, which increases the burden on the system designer.

[0014] Furthermore, the inventions described in Patent Documents 1 and 2 both require continuous monitoring of the output voltage or the voltage on the load side during the operation of the system.

[0015] The present invention was made in the context described above, and its object is to provide a DC-DC converter, a semiconductor integrated circuit for power control, and a power supply device that can reduce the burden on system designers by eliminating the need to consider the resistance value of the load side in advance.

[0016] Another objective of the present invention is to provide a DC-DC converter, a semiconductor integrated circuit for power control, and a power supply device that enables a constant voltage applied to the power supply terminals of a load device without requiring continuous monitoring of the output voltage or the voltage on the load side during system operation.

[0017] Methods for solving problems

[0018] To achieve the above objectives, the present invention provides a DC-DC converter that converts a DC input voltage supplied from a DC power source to output DC voltages of different potentials. The DC-DC converter comprises:

[0019] The control circuit controls the switching element based on the potential difference between a feedback voltage proportional to the output voltage and a predetermined reference voltage.

[0020] A current source circuit through which a predetermined current flows;

[0021] A voltage correction circuit that corrects the reference voltage or the feedback voltage.

[0022] The voltage correction circuit is configured to determine the voltage correction amount based on information related to the resistance on the load side that is input from the outside when the current source circuit outputs the current, and to correct the reference voltage or the feedback voltage.

[0023] Based on the above structure, since the DC-DC converter has the function of automatically correcting and comparing the reference voltage with the feedback voltage, there is no need to consider the resistance value of the load side in advance for design, which can reduce the burden on the system designer.

[0024] In addition, it is possible to keep the voltage applied to the power terminals of the load device constant without having to continuously monitor the output voltage or the voltage on the load side during system operation.

[0025] Additionally, the information related to the load-side resistance includes the resistance value of the cable or wiring supplying power to the load device or load unit. Furthermore, it is possible to transmit this load-side resistance information from the load device or load unit to the DC-DC converter using a communication device with a standard such as RS485.

[0026] Preferably, a switching unit is provided, which outputs the current of the current source circuit to the voltage output terminal according to the change of the signal supplied from the outside for controlling the execution / stop of the circuit operation to an effective level.

[0027] According to this structure, the current of the current source circuit can be output to the voltage output terminal using an external signal.

[0028] Alternatively, a current-to-voltage conversion element is preferably connected in series with the switching element between the voltage input terminal and the voltage output terminal. The current source circuit outputs current toward the voltage output terminal via the current-to-voltage conversion element. The voltage correction circuit determines the voltage correction amount based on the voltage converted by the current-to-voltage conversion element and corrects the reference voltage or the feedback voltage.

[0029] According to this structure, the voltage correction amount is determined based on the voltage converted by the current-to-voltage conversion element (resistor for current detection) and the reference voltage or feedback voltage is corrected. Therefore, it is not necessary to send the resistance value information of the load side from the load device side, thus reducing the burden on the system designer.

[0030] Furthermore, the voltage correction circuit preferably includes:

[0031] A subtraction circuit that calculates the potential difference between the two terminals of the current-to-voltage conversion element;

[0032] A first voltage-to-current conversion circuit converts the potential difference calculated by the subtraction circuit into current.

[0033] A variable resistor circuit is connected to the first voltage-to-current conversion circuit;

[0034] A second voltage-to-current conversion circuit converts the reference voltage into current.

[0035] The synthesis circuit combines the current converted by the first voltage-to-current conversion circuit and the current converted by the second voltage-to-current conversion circuit to convert it into a voltage, which is then used as the corrected voltage output.

[0036] The variable resistor circuit is configured such that, based on the voltage converted by the current-to-voltage conversion element, the greater the potential difference, the greater the resistance value.

[0037] According to this structure, since it has a variable resistor circuit that automatically determines the voltage correction amount, the system designer does not need to determine the value of the external resistor for adjustment, thus reducing the burden on the system designer. Furthermore, by integrating the variable resistor circuit into the power control IC, the number of components in the DC-DC converter can be reduced.

[0038] In addition, the control circuit preferably includes:

[0039] An error amplifier circuit outputs a voltage corresponding to the potential difference between the voltage divided by the voltage divider circuit connected between the voltage output terminal and the ground point and the reference voltage.

[0040] A logic circuit that generates on / off control signals for the switching element based on the output voltage of the error amplifier circuit.

[0041] Therefore, it is possible to easily design DC-DC converters using existing design assets.

[0042] Another invention of this application is a semiconductor integrated circuit for power control constituting a DC-DC converter. This DC-DC converter turns on and off a switching element connected between a voltage input terminal and an external terminal connected to one terminal of an inductor to rectify the current flowing through the inductor, thereby converting the DC input voltage supplied from a DC power source to output DC voltages of different potentials.

[0043] The power control semiconductor integrated circuit includes:

[0044] The control circuit controls the switching element based on the potential difference between a feedback voltage proportional to the output voltage and a predetermined reference voltage;

[0045] A current source circuit through which a predetermined current flows;

[0046] A switching unit that outputs the current from the current source circuit toward the voltage output terminal;

[0047] A voltage correction circuit that corrects the reference voltage or the feedback voltage;

[0048] External information input terminal, which receives information signals from external sources.

[0049] The voltage correction circuit is configured to determine the voltage correction amount based on the information signal input from the load side to the external information input terminal when the current source circuit outputs current, and to correct the reference voltage or the feedback voltage.

[0050] Based on the above structure, the power control IC has the function of automatically correcting the reference voltage compared with the feedback voltage based on information from the outside. Therefore, it is not necessary to consider the resistance value information of the load side when designing the DC-DC converter, which can reduce the burden on the system designer. In addition, it is not necessary to continuously detect the output voltage or the voltage on the load side during the operation of the system, so that the voltage applied to the power supply terminal of the load device can be kept constant. Furthermore, the voltage correction amount is determined and the reference voltage or feedback voltage is corrected based on the voltage converted by the current-to-voltage conversion element (current sensing resistor), so it is not necessary to send the resistance value information of the load side from the load device side, thus reducing the burden on the system designer.

[0051] Preferably, the circuit includes: an input terminal for a signal supplied from the outside to control the execution / stopping of circuit operation; and a pair of external information input terminals for inputting the voltage of the two terminals of a current-to-voltage conversion element connected in series with the inductor to the other terminal of the inductor. The switching unit outputs the current of the current source circuit to the terminal of the pair of external information input terminals connected to the connection point of the inductor and the current-to-voltage conversion element according to the change of the signal to an effective level.

[0052] The voltage correction circuit is configured to determine the voltage correction amount based on the difference between the voltages input to the pair of external information input terminals when the current source circuit outputs current, and to correct the reference voltage or the feedback voltage.

[0053] According to this structure, the current from the current source circuit can be directed to the current-voltage conversion element by using the terminal for inputting the voltage converted by the current-voltage conversion element (current sensing resistor), thus reducing the number of external terminals of the IC.

[0054] Furthermore, the voltage correction circuit preferably comprises: a subtraction circuit that calculates the potential difference between the two terminals of the current-to-voltage conversion element; a first voltage-to-current conversion circuit that converts the potential difference calculated by the subtraction circuit into a current; a variable resistor circuit connected to the first voltage-to-current conversion circuit; a second voltage-to-current conversion circuit that converts the reference voltage into a current; and a synthesis circuit that combines the current converted by the first voltage-to-current conversion circuit and the current converted by the second voltage-to-current conversion circuit to convert them into a voltage, and outputs the corrected voltage. The variable resistor circuit is configured such that the larger the potential difference between the voltage converted by the current-to-voltage conversion element and the variable resistor circuit, the larger the resistance value.

[0055] According to this structure, since it has a variable resistor circuit that automatically determines the voltage correction amount, the system designer does not need to determine the value of the external resistor for adjustment, thus reducing the burden on the system designer. Furthermore, by integrating the variable resistor circuit into the power control IC, the number of components in the DC-DC converter can be reduced.

[0056] In addition, the control circuit preferably includes: an error amplifier circuit that outputs a voltage corresponding to the potential difference between the voltage divided by the voltage divider circuit connected between the voltage output terminal and the ground point and the reference voltage; and a logic circuit that generates on / off control signals for the switching element based on the output voltage of the error amplifier circuit.

[0057] Therefore, it is possible to easily design DC-DC converters using existing design assets.

[0058] Invention Effects

[0059] According to the present invention, a DC-DC converter and a semiconductor integrated circuit for power control can be provided. Because it has the function of automatically correcting the reference voltage compared with the feedback voltage, it eliminates the need for prior consideration of the load-side resistance value during design, thus reducing the burden on system designers. Furthermore, it provides a DC-DC converter, a semiconductor integrated circuit for power control, and a power supply device that allows for constant voltage applied to the power supply terminals of the load device without continuously monitoring the output voltage during system operation and while maintaining a constant voltage on the load side. Attached Figure Description

[0060] Figure 1 This is a circuit diagram illustrating one embodiment of the DC-DC converter and power supply semiconductor integrated circuit (power IC) to which the present invention is applied.

[0061] Figure 2 It means Figure 1 The timing diagram shows the changes in the enable signal, the current flowing to the current sensing resistor, and the supply voltage to the load device in the DC-DC converter.

[0062] Figure 3 This is a circuit diagram showing a specific example of the voltage correction circuit within a power supply IC.

[0063] Figure 4A It is a graph showing the relationship between the input voltage of the external terminals SENSP and SENSN in the power supply IC of the embodiment and the output voltage of the voltage correction circuit.

[0064] Figure 4B It is a graph showing the relationship between the input voltage of the external terminals SENSP and SENSN and the output voltage of the DC-DC converter.

[0065] Figure 5 This is a structural diagram showing a modified example of a system to which the present invention is applied.

[0066] Figure 6A It means Figure 5 The timing diagram of the first action timing example of the power supply IC in the system.

[0067] Figure 6B It means Figure 5 The timing diagram of the second action timing example of the power supply IC in the system.

[0068] Figure 7 This is a circuit diagram illustrating an example of the structure of an existing DC-DC converter and power IC. Detailed Implementation

[0069] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0070] Figure 1 This describes one embodiment of the invention when applied to a switch-controlled DC-DC converter (DC power supply device). While not specifically limited, Figure 1 The components forming the circuit surrounded by the solid line A are formed on a semiconductor chip, constituting a semiconductor integrated circuit (IC). In addition, the circuit to the left of the output terminals OUT1 and OUT2 is formed on a substrate such as a printed wiring board, and the output terminals OUT1 and OUT2 are connected to the IC or components on the substrate through printed wiring formed on the substrate.

[0071] The DC-DC converter of this embodiment comprises a power control semiconductor integrated circuit (hereinafter referred to as power IC) 10, an inductor (coil) L1, a smoothing capacitor C1, a current sensing resistor Rs, and a smoothing capacitor C2. The power control semiconductor integrated circuit 10 has a built-in switching element for allowing current to flow to the outside and a control circuit for generating a signal to control the switching element to be turned on and off at an appropriate timing. One terminal of the inductor (coil) L1 is connected to the external terminal SW of the power IC 10; the smoothing capacitor C1 is connected between the other terminal of the inductor L1 and the ground point (the ground terminal PGND of the IC); the current sensing resistor Rs is connected in series with the inductor L1 between the external terminal SW and the voltage output terminal OUT1; and the smoothing capacitor C2 is connected between the voltage output terminal OUT1 and the ground point.

[0072] Furthermore, the DC-DC converter in this embodiment has a voltage output terminal OUT2, which is connected to the same grounding point as the grounding terminal PGND of the power supply IC 10. One end of the cable 21 is connected to the voltage output terminals OUT1 and OUT2, and the other end is connected to the voltage input terminals CN1 and CN2 of the device 22 that serves as the load, supplying DC voltage to the load via the cable 21. Resistors Rc1 and Rc2 represent the resistive components of the cable 21, and RL represents the equivalent resistance (load resistance) of the load device 22. In addition, the series resistors Rb1 and Rb2 connected between the voltage output terminal OUT1 and the grounding point are bleed resistors used to input the voltage VFB obtained by dividing the output voltage Vout of the DC-DC converter to the feedback terminal FB of the power supply IC 10.

[0073] The power supply IC 10 consists of a switching transistor M1, a synchronous rectifier transistor M2, a logic circuit 11, drive circuits 12A and 12B, an error amplifier 13, and a reference voltage supply circuit 14. The switching transistor M1, as a switching element composed of an N-channel MOSFET (field-effect transistor), is connected between the power input terminal VIN, which is supplied with a DC voltage from a DC power source such as a battery, and the external terminal SW. It is driven by allowing current to flow through the inductor L1. The synchronous rectifier transistor M2 is connected between the external terminal SW and the ground terminal PGND. The logic circuit 11 is a control circuit used to generate signals to control the switching on and off of the transistors M1 and M2. The drive circuits 12A and 12B drive the transistors M1 and M2 to switch on and off using the switching control signals generated by the logic circuit 11. The inverting input terminal of the error amplifier 13 is connected to the feedback terminal FB. The reference voltage supply circuit 14 is used to supply a reference voltage VREF' applied to the non-inverting input terminal of the error amplifier 13. The power supply voltage of the driver circuit 12A is the voltage BS after the internal voltage VDD of the IC is increased.

[0074] Additionally, the power supply IC 10 includes: external terminals SENSP and SENSN for receiving the voltage across the two terminals of the current sensing resistor Rs; a constant current source 15 and a switching element SW1 connected in series between the internal power supply voltage terminal Vcc and the external terminal SENSP; and an external terminal PEN for receiving an enable signal EN to activate the power supply IC 10. This enable signal EN is input to the logic circuit 11, which generates a control signal CS that temporarily activates the switching element SW1 when the effective level of the enable signal EN rises to a high level. On the other hand, a switching element SW2 is also provided between the voltage input terminals CN1 and CN2 of the load device 22, which short-circuit CN1 and CN2 via the enable signal EN.

[0075] Therefore, when switching elements SW1 and SW2 are turned on, as Figure 2 As shown in (B), the current Ibias flows temporarily from the constant current source 15 through the external terminal SENSP and the current sensing resistor Rs.

[0076] Furthermore, through the aforementioned current Ibias output from the external terminal SENSP, such as Figure 2 During period T1 (C), the voltage between output terminals OUT1-OUT2 changes, and the voltage generated by the voltage drop in the current sensing resistor Rs is input to the external terminals SENSP and SENSN. At this time, the voltage generated by the voltage drop in the current sensing resistor Rs depends on the resistive component of cable 21 and the equivalent resistance RL of load device 22, thus reflecting the resistance value on the load side.

[0077] The reference voltage supply circuit 14 includes: a voltage correction circuit 41, which generates a correction voltage VOVA based on the input voltages of the external terminals SENSP and SENSN to correct the reference voltage applied to the non-inverting input terminal of the error amplifier 13; a synthesis unit 42, which synthesizes the voltage VOVA generated by the voltage correction circuit 41 with a reference voltage VREF, and supplies the corrected reference voltage to the error amplifier 13; and a variable resistor circuit VR, which adjusts the voltage correction amount of the voltage correction circuit 41. Therefore, as... Figure 2 The period T2 of (C) changes as shown by the dashed line without voltage correction, but changes as shown by the solid line with voltage correction. Furthermore, the voltage correction amount of the voltage correction circuit 41 becomes the magnitude corresponding to the resistance value of the load resistor RL.

[0078] Figure 3 An example of the specific circuit structure of the voltage correction circuit 41 described above is shown.

[0079] like Figure 3 As shown, the voltage correction circuit 41 of this embodiment includes: a subtraction circuit 44, which is composed of input resistors R1 and R2, an operational amplifier AMP1, and a feedback resistor R3; a voltage-to-current conversion circuit 45, which is composed of a buffer amplifier AMP2 whose output of the subtraction circuit 44 is input to a non-inverting input terminal and a MOS transistor M3 whose output of the amplifier AMP2 is applied to a gate terminal; and a current mirror circuit (M4, M5) 46, through which a current proportional to the current flowing in the MOS transistor M3 flows. The subtraction circuit 44 receives the voltages of the external terminals SENSP and SENSN via the input resistors R1 and R2, thereby outputting a voltage corresponding to the potential difference ΔV between the terminals SENSP and SENSN. The voltage-to-current conversion circuit 45 introduces a current corresponding to ΔV by converting this voltage into a current.

[0080] Furthermore, in the voltage correction circuit 41 of this embodiment, a variable resistor circuit VR for adjusting the voltage correction amount is connected between the source terminal of the aforementioned MOS transistor M3 and the ground point, and a resistor adjustment circuit 47 is also included. This resistor adjustment circuit 47 generates a signal to adjust the resistance value ROVA of the variable resistor circuit VR based on the voltage of the external terminals SENSP and SENSN. The variable resistor circuit VR is configured, for example, to have multiple trapezoidal resistors and switching elements connected in parallel or series with each resistor. The switching elements are selectively turned on according to the signal from the resistor adjustment circuit 47, thereby changing the resistance value.

[0081] A register is provided in the resistor adjustment circuit 47 to store information about a signal used to adjust the resistance value ROVA obtained by temporarily allowing the current Ibias to flow through the current sensing resistor Rs when the enable signal EN rises. Alternatively, the signal for adjusting the resistance value ROVA of the variable resistor circuit VR can be provided from an external source (e.g., a load device). When the adjustment signal (information) for the variable resistor circuit VR is provided from an external source, an external terminal for inputting the adjustment signal to the power supply IC 10 is required. Alternatively, both the resistor adjustment circuit 47 and the external terminal for inputting the adjustment signal can be provided; in this case, the adjustment signal from the external source can be prioritized, or either one can be selected.

[0082] Additionally, the synthesis unit 42 includes: a voltage-to-current conversion circuit 48, which consists of a buffer amplifier AMP3 whose reference voltage VREF is input to the non-inverting input terminal as a reference and a MOS transistor M6 whose gate terminal is applied with the output of the amplifier AMP3; and a current mirror circuit (M7, M8) 49, through which a current proportional to the current flowing in the MOS transistor M6 flows, and the drain terminal of the MOS transistor M6 is connected to the ground point via a resistor R5.

[0083] Then, the drain current of the MOS transistor M8, which constitutes the output side of the current mirror circuit 49, and the drain current of the MOS transistor M5, which constitutes the output side of the current mirror circuit 46, which constitutes the voltage correction circuit 41, are combined at node N1 and flow through resistor R5. This generates and outputs a combined voltage, which is the sum of the corrected voltage VOVA and the reference voltage VREF. This voltage is configured to be input as the reference voltage VREF'. Figure 1 The non-inverting input terminal of the error amplifier 13.

[0084] Figure 4A The relationship between the potential difference ΔV between external terminals SENSP and SENSN and the corrected voltage VOVA is shown. According to... Figure 4AAs can be seen, in the circuit of this embodiment, the correction voltage VOVA is set to be proportional to the potential difference ΔV between the external terminals SENSP and SENSN, and the larger the resistance value ROVA of the variable resistor VR, the larger the slope.

[0085] exist Figure 1 In the DC-DC converter of the above embodiment shown, when the current flowing through the current sensing resistor Rs increases, thereby increasing the potential difference ΔV between the external terminals SENSP and SENSN, the reference voltage VREF' input to the error amplifier 13 becomes high, and the logic circuit 11 causes the on-time of the switching transistors M1 and M2 to change. As a result, as... Figure 4B As shown, the greater the potential difference ΔV between the external terminals SENSP and SENSN, the higher the output voltage Vout of the DC-DC converter, and the voltage VLOAD supplied to the voltage input terminal CN1 of the load device 22 is controlled to be approximately constant.

[0086] Regarding the on / off control method of the switching transistors M1 and M2 in the logic circuit (switching control circuit) 11 of the power supply IC in this embodiment, various control methods have been proposed in the past, such as those described in Japanese Patent Application Publication No. 2012-139023. In the DC-DC converter of this embodiment, the logic circuit 11 can be constructed using a known control method, so the description of specific examples is omitted.

[0087] In the logic circuit 11 of the power IC in this embodiment, in addition to controlling the on / off state of the switching transistors M1 and M2, as described above, it also includes logic for generating a control signal that causes the current Ibias to temporarily flow through the current detection resistor Rs when the enable signal EN rises, and a timer is set to start the original switching control after the resistance value of the variable resistor VR is adjusted. Alternatively, logic for starting the switching control by receiving the adjustment end signal from the resistor adjustment circuit 47 can be set instead of the timer.

[0088] As described above, in this embodiment, when the enable signal EN rises, the current Ibias temporarily flows through the current sensing resistor Rs to obtain the resistance value information on the load side. The DC-DC converter automatically determines and adjusts the correction amount for the reference voltage, thus reducing the research steps required in the past for adjusting peripheral components at the DC-DC converter side during design. Furthermore, while the resistance value of the power cable 21 used in system construction may have deviations, the DC-DC converter in this embodiment also includes correction for the resistance value deviation of the power cable 21, thus having the advantage of not needing to consider component deviations. Moreover, the power IC of this embodiment has a built-in resistor for voltage correction adjustment, therefore... Figure 7Compared to conventional power ICs, the DC-DC converter shown can reduce the number of components. Conventional power ICs include a voltage correction adjustment resistor as an external component.

[0089] (Modified Example)

[0090] Next, use Figure 5 and Figure 6A and Figure 6B A variation of the DC-DC converter (power IC) described above will be explained.

[0091] like Figure 5 As shown, in this modified example, communication units 120 and 220, which are capable of performing serial communication according to a communication standard such as RS485, are respectively provided in the power supply device 100 and the load device 200, which include the DC-DC converter 110, so that information related to the resistance on the load side can be sent (feedback) from the load device 200 to the power supply device 100.

[0092] In addition, the power IC constituting the power supply device 100 and Figure 1 Similarly, the power supply IC 10 shown is configured to include a constant current source 15, a switching element SW1, and a voltage correction circuit 41, in which the reference voltage supplied to the error amplifier 13 is corrected.

[0093] On the other hand, the load device 200 includes, for example, an AD conversion circuit (ADC) 210 that converts the information (analog value) of the load-side resistance obtained by dividing the voltage of the voltage input terminal CN1 using series resistors Rb3 and Rb4 into a digital value; and a communication unit 220 that outputs the converted digital value from terminals CN3 and CN4.

[0094] Furthermore, in this modified example, it is not necessary to provide a current sensing resistor Rs in the power supply device 100; instead, it is replaced in the power supply IC of the DC-DC converter 110. Figure 3 The external terminals SENSP and SENSN are shown, and a pair of terminals P1 and P2 are provided for inputting information (serial data) from the load device 200 side via communication cable 23. The voltage correction circuit 41 is configured to receive information (serial data) from the load device 200 side. Figure 3 The circuit shown has removed the voltage-to-current conversion circuit 45, which consists of subtraction circuit 44, buffer amplifier AMP2, and MOS transistor M1. Furthermore, the resistor adjustment circuit 47 is configured to adjust the resistance value ROVA of the variable resistor circuit VR based on data supplied from the load device 200 side.

[0095] The communication unit 220 of the load device 200 consists of a converter 221 that performs parallel / serial conversion and a serial port (driver) 222, and the communication unit 120 of the power supply device 100 consists of a converter 121 that performs serial / parallel conversion and a serial port (receiver) 122. Each communication unit 120 and 220 can also be configured to perform bidirectional communication.

[0096] Figure 6A , Figure 6B This is a timing example representing the voltage correction operation in this variation.

[0097] Figure 6A , Figure 6B In Figure 6A Similar to the embodiment described above, when the enable signal EN rises, the switching element SW1 is turned on, causing current from the constant current source 15 to flow to the power cable. This sends information about the resistance detected at the load side (including the resistance component of the cable) to the power supply device 100. The power supply IC uses the received information (feedback signal) to perform voltage correction. In this configuration, the correction voltage VOVA generated in the voltage correction circuit 41 is corrected once and changes when the enable signal EN rises.

[0098] on the other hand, Figure 6B The system is configured to periodically send information (feedback signal) related to the resistance on the load side from the load device 200 to the power supply device 100 during system operation, and the power supply IC uses the received information to perform voltage correction. In this configuration, the correction voltage VOVA generated in the voltage correction circuit 41 varies according to the voltage VLOAD at the voltage input terminal CN1 of the load device 200.

[0099] The timing for sending information related to the resistance on the load side from the load device 200 to the power supply device 100 can be either the timing by which the power supply IC of the power supply device 100 periodically turns on the internal switching element SW1 to allow current from the constant current source 15 to flow to the power cable, or it can be a different timing mechanism. If a different timing mechanism is used, the constant current source 15 and the switching element SW1 are not required in the power supply IC. Alternatively, the power supply IC of the power supply device 100 can be configured to allow selection of... Figure 6A The timing and Figure 6B Which of the timing parameters shown performs voltage correction?

[0100] The invention described above is based on specific embodiments, but the invention is not limited to the above embodiments. For example, in the above embodiments, the reference voltage is corrected by a voltage correction circuit, but the feedback voltage can also be corrected.

[0101] Furthermore, in the above embodiment, a MOS transistor is shown as the transistor constituting the power supply IC10, but a bipolar transistor can also be used instead of a MOS transistor. Additionally, in the above embodiment, the application of the present invention to a synchronous rectification DC-DC converter is described, but the present invention can also be applied to a converter using a diode instead of a MOS transistor. Figure 1 A DC-DC converter using asynchronous rectification with switching transistor M2.

[0102] Furthermore, in the above embodiments, as an application example, a system for supplying DC power from a power supply device to a device that becomes a load was described. However, the present invention can also be applied, for example, to a system consisting of a servo driver and an encoder, where a power supply function for the encoder is provided on the servo driver side, and the power supply is controlled (corrected) by feeding back information related to the resistance on the load side from the encoder to the servo driver.

[0103] Industrial applications

[0104] In the above embodiments, the present invention was described as being applied to a DC-DC converter with a switching control method. However, the present invention can also be applied to a linear regulator that continuously controls a transistor disposed between the voltage input terminal and the output terminal based on the feedback voltage from the output side to maintain the output voltage at a constant level.

[0105] Furthermore, while the above embodiments describe the application of the present invention to a buck DC-DC converter, the present invention can also be applied to boost or buck-boost DC-DC converters. Moreover, the present invention can be employed regardless of control methods such as voltage-mode control, current-mode control, or hysteresis control.

[0106] Explanation of reference numerals in the attached figures

[0107] 10……Power supply semiconductor integrated circuit (power IC), 11……Logic circuit (control circuit), 12A, 12B……Driver circuit, 13……Error amplifier, 14……Reference voltage supply circuit, 15……Constant current source, 21……Power supply line, 22……Load device, 41……Voltage correction circuit, 42……Synthesis unit, 44……Subtraction circuit, 45, 48……Voltage-to-current conversion circuit, 46, 49……Current mirror circuit, 47……Resistor adjustment circuit, VR……Variable resistor circuit, L1……Inductor (coil), M1……Switching transistor (switching element) for inductor driving.

Claims

1. A DC-DC converter that converts a DC input voltage supplied from a DC power source to output DC voltages of different potentials. Its features are, The DC-DC converter has the following features: The control circuit controls the switching element based on the potential difference between a feedback voltage proportional to the output voltage and a predetermined reference voltage. A current source circuit through which a predetermined current flows; as well as A voltage correction circuit that corrects the reference voltage or the feedback voltage. The voltage correction circuit is configured to determine the voltage correction amount based on information related to the resistance on the load side that is input from the outside when the current source circuit outputs the current, and to correct the reference voltage or the feedback voltage.

2. The DC-DC converter according to claim 1, characterized in that, The DC-DC converter includes a switching unit that outputs current from the current source circuit to the voltage output terminal based on the change of an externally supplied signal for controlling the execution / stop of circuit operation to an effective level.

3. The DC-DC converter according to claim 1 or 2, characterized in that, A current-to-voltage conversion element is connected in series with the switching element between the voltage input terminal and the voltage output terminal. The current from the current source circuit is output to the voltage output terminal via the current-to-voltage conversion element. The voltage correction circuit is configured to determine the voltage correction amount based on the voltage converted by the current-to-voltage conversion element, and to correct the reference voltage or the feedback voltage.

4. The DC-DC converter according to claim 3, characterized in that, The voltage correction circuit includes: A subtraction circuit that calculates the potential difference between the two terminals of the current-to-voltage conversion element; A first voltage-to-current conversion circuit converts the potential difference calculated by the subtraction circuit into current. A variable resistor circuit is connected to the first voltage-to-current conversion circuit; A second voltage-to-current conversion circuit converts the reference voltage into current; The synthesis circuit combines the current converted by the first voltage-to-current conversion circuit and the current converted by the second voltage-to-current conversion circuit to convert it into a voltage, which is then used as the corrected voltage output. The variable resistor circuit is configured such that, based on the voltage converted by the current-to-voltage conversion element, the greater the potential difference, the greater the resistance value.

5. The DC-DC converter according to claim 1 or 2, characterized in that, The control circuit includes: An error amplifier circuit, the output of which is the voltage corresponding to the potential difference between the voltage divided by the voltage divider circuit connected between the voltage output terminal and the ground point and the reference voltage; and A logic circuit that generates on / off control signals for the switching element based on the output voltage of the error amplifier circuit.

6. A semiconductor integrated circuit for power control constituting a DC-DC converter, the DC-DC converter turning on and off a switching element connected between a voltage input terminal and an external terminal connected to one terminal of an inductor to rectify the current flowing through the inductor, thereby converting a DC input voltage supplied from a DC power supply to output DC voltages of different potentials. Its features are, The power control semiconductor integrated circuit includes: The control circuit controls the switching element based on the potential difference between a feedback voltage proportional to the output voltage and a predetermined reference voltage; A current source circuit through which a predetermined current flows; A switching unit that outputs the current from the current source circuit to the voltage output terminal; A voltage correction circuit that corrects the reference voltage or the feedback voltage; and External information input terminal, which receives information signals from external sources. The voltage correction circuit is configured to determine the voltage correction amount based on an information signal related to the resistance on the load side, which is input from the load side to the external information input terminal when the current source circuit outputs current, and to correct the reference voltage or the feedback voltage.

7. The semiconductor integrated circuit for power control according to claim 6, characterized in that, The power control semiconductor integrated circuit includes: Input terminals for signals supplied from the outside to control the execution / stopping of circuit operations; and A pair of external information input terminals are provided to input the voltage between the two terminals of a current-to-voltage conversion element connected in series with the inductor to the other terminal of the inductor. The switching unit outputs the current from the current source circuit to the terminal of the pair of external information input terminals connected to the connection point of the inductor and the current-to-voltage conversion element, based on the change of the signal towards the effective level. The voltage correction circuit is configured to determine the voltage correction amount based on the voltage difference input to the pair of external information input terminals when the current source circuit outputs current, and to correct the reference voltage or the feedback voltage.

8. The semiconductor integrated circuit for power control according to claim 7, characterized in that, The voltage correction circuit includes: A subtraction circuit that calculates the potential difference between the two terminals of the current-to-voltage conversion element; A first voltage-to-current conversion circuit converts the potential difference calculated by the subtraction circuit into current. A variable resistor circuit is connected to the first voltage-to-current conversion circuit; A second voltage-to-current conversion circuit converts the reference voltage into current; The synthesis circuit combines the current converted by the first voltage-to-current conversion circuit and the current converted by the second voltage-to-current conversion circuit to convert it into a voltage, which is then used as the corrected voltage output. The variable resistor circuit is configured such that, based on the voltage converted by the current-to-voltage conversion element, the greater the potential difference, the greater the resistance value.

9. The semiconductor integrated circuit for power control according to any one of claims 6 to 8, characterized in that, The control circuit includes: An error amplifier circuit, the output of which is the voltage corresponding to the potential difference between the voltage divided by the voltage divider circuit connected between the voltage output terminal and the ground point and the reference voltage; and A logic circuit that generates on / off control signals for the switching element based on the output voltage of the error amplifier circuit.

10. A power supply device that converts a DC input voltage supplied from a DC power source to output DC voltages of different potentials, characterized in that, The power supply device includes: The control circuit controls the switching element or voltage control transistor connected between the voltage input terminal and the voltage output terminal based on the potential difference between the feedback voltage, which is proportional to the output voltage, and the predetermined reference voltage. A current source circuit through which a predetermined current flows; as well as A voltage correction circuit that corrects the reference voltage or the feedback voltage. The voltage correction circuit is configured to determine the voltage correction amount based on information related to the resistance on the load side that is input from the outside when the current source circuit outputs the current, and to correct the reference voltage or the feedback voltage.

11. The power supply device according to claim 10, characterized in that, The power supply device includes a switching unit that outputs current from the current source circuit to the voltage output terminal based on the change of an externally supplied signal for controlling the execution / stop of circuit operation to an effective level.

12. The power supply device according to claim 10 or 11, characterized in that, A current-to-voltage conversion element is connected in series with the switching element or voltage control transistor between the voltage input terminal and the voltage output terminal. The current from the current source circuit is output to the voltage output terminal via the current-to-voltage conversion element. The voltage correction circuit is configured to determine the voltage correction amount based on the voltage converted by the current-to-voltage conversion element, and to correct the reference voltage or the feedback voltage.

13. The power supply device according to claim 12, characterized in that, The voltage correction circuit includes: A subtraction circuit that calculates the potential difference between the two terminals of the current-to-voltage conversion element; A first voltage-to-current conversion circuit converts the potential difference calculated by the subtraction circuit into current. A variable resistor circuit is connected to the first voltage-to-current conversion circuit; A second voltage-to-current conversion circuit converts the reference voltage into current; and The synthesis circuit combines the current converted by the first voltage-to-current conversion circuit and the current converted by the second voltage-to-current conversion circuit to convert it into a voltage, which is then used as the corrected voltage output. The variable resistor circuit is configured such that, based on the voltage converted by the current-to-voltage conversion element, the greater the potential difference, the greater the resistance value.

14. The power supply device according to claim 10 or 11, characterized in that, The control circuit includes: An error amplifier circuit, the output of which is the voltage corresponding to the potential difference between the voltage divided by the voltage divider circuit connected between the voltage output terminal and the ground point and the reference voltage; and A logic circuit that generates on / off control signals for the switching element based on the output voltage of the error amplifier circuit.

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