Backup power supply, control method, and control program

Abstract

To suppress the number of components.SOLUTION: A backup power supply includes: an electric double layer capacitor; a first switching element; a coil, one end of which is connected to one end of the first switching element and the other end of which is connected to one end of the electric double layer capacitor; a second switching element, one end of which is connected to the one end of the first switching element; and a control part which, when an input voltage is equal to or more than a first set voltage, performs a control in a first mode to charge the electric double layer capacitor by allowing the first switching element to perform switching operation, and when the input voltage is less than the first set voltage, which performs a control in a second mode to discharge the electric double layer capacitor by allowing the second switching element to perform switching operation. The control part allows the second switching element to perform switching operation, as a synchronous rectification element, in the first mode, and allows the first switching element to perform switching operation, as a synchronous rectification element, in the second mode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a backup power supply, a control method, and a control program. [Background technology]

[0002] Vehicles are equipped with various devices that operate using power from a battery (for example, an auxiliary battery). Patent Document 1 describes a backup power supply device that allows the above-mentioned devices to operate even if the battery becomes unable to output power due to a traffic accident or the like.

[0003] The backup power supply device described in Patent Document 1 shares a coil between the boost circuit and the buck circuit. In other words, the boost circuit and the buck circuit constitute a boost-buck circuit. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6643566 [Overview of the project] [Problems that the invention aims to solve]

[0005] The backup power supply device described in Patent Document 1 includes an output rectifier element connected with the direction from the boost circuit to the terminals as the forward direction, as the current output path from the electric double-layer capacitor to the terminals. However, it is desirable to reduce the number of components.

[0006] The present invention aims to provide a backup power supply device, a control method, and a control program that can reduce the number of components. [Means for solving the problem]

[0007] A backup power supply device according to one aspect of the present invention is: A terminal section having an input terminal, an output terminal, a connection point electrically connected to the output terminal, and an input rectifier element whose anode is electrically connected to the input terminal and whose cathode is electrically connected to the connection point, An electric double-layer capacitor, one end of which is electrically connected to a reference potential, A first switching element, one end of which is electrically connected to the connection point, A coil having one end electrically connected to the other end of the first switching element and the other end electrically connected to the other end of the electric double layer capacitor, A second switching element, one end of which is electrically connected to the other end of the first switching element and one end of the coil, and the other end of which is electrically connected to a reference potential, A control unit performs a first mode of control, in which, when the input voltage input to the input terminal is equal to or greater than a predetermined first set voltage, the first switching element is switched based on the current flowing through the first switching element and the charging voltage of the electric double layer capacitor, thereby operating the first switching element and the coil as a step-down circuit to charge the electric double layer capacitor; and when the input voltage is less than the first set voltage, the second switching element is switched based on the current flowing through the second switching element and the output voltage output from the output terminal, thereby operating the second switching element and the coil as a step-up circuit to discharge the electric double layer capacitor. Equipped with, The control unit, In the first mode, the second switching element is operated as a synchronous rectifier element of the step-down circuit, and in the second mode, the first switching element is operated as a synchronous rectifier element of the step-up circuit. It is characterized by the following:

[0008] In the aforementioned backup power supply device, The control unit, In the first mode, the second switching element is turned off at the timing when the current flowing through the second switching element becomes zero or reverses, and in the second mode, the first switching element is turned off at the timing when the current flowing through the first switching element becomes zero or reverses. It is characterized by the following:

[0009] In the aforementioned backup power supply device, The control unit, The switching frequency of the second mode is set to a higher frequency than the switching frequency of the first mode. It is characterized by the following:

[0010] In the aforementioned backup power supply device, The control unit, A first error amplifier for detecting the error between the charging voltage of the electric double layer capacitor and the target charging voltage of the electric double layer capacitor, A second error amplifier for detecting the error between the output voltage and the target voltage of the output voltage, It has, In the first mode, the first error amplifier is used to control the charging voltage of the electric double-layer capacitor, and in the second mode, the second error amplifier is used to control the output voltage. It is characterized by the following:

[0011] In the aforementioned backup power supply device, The control unit, In the first mode, the switching operation of the first switching element and the second switching element is stopped when the charging voltage of the electric double-layer capacitor exceeds a predetermined second set voltage, and in the second mode, the switching operation of the first switching element and the second switching element is stopped when the output voltage exceeds a predetermined third set voltage. It is characterized by the following:

[0012] In the aforementioned backup power supply device, The control unit, The device includes a sawtooth wave generation circuit for generating a sawtooth wave that determines the switching frequencies of the first switching element and the second switching element, In the first mode, current information of the current flowing through the first switching element is added to the sawtooth wave, and in the second mode, current information of the current flowing through the second switching element is added to the sawtooth wave to perform current mode control. It is characterized by the following:

[0013] In the aforementioned backup power supply device, The control unit, The switching between the first mode and the second mode is performed at the start of the switching cycle. It is characterized by the following:

[0014] One aspect of the present invention is a control method, A control method for a backup power supply device comprising: a terminal section having an input terminal, an output terminal, a connection point electrically connected to the output terminal, and an input rectifier element whose anode is electrically connected to the input terminal and whose cathode is electrically connected to the connection point; an electric double-layer capacitor with one end electrically connected to a reference potential; a first switching element with one end electrically connected to the connection point; a coil with one end electrically connected to the other end of the first switching element and the other end electrically connected to the other end of the electric double-layer capacitor; and a second switching element with one end electrically connected to the other end of the first switching element and one end of the coil, and the other end electrically connected to a reference potential; When the input voltage input to the input terminal is equal to or greater than a predetermined first set voltage, a first mode of control is performed in which the first switching element is switched based on the current flowing through the first switching element and the charging voltage of the electric double layer capacitor, thereby operating the first switching element and the coil as a step-down circuit to charge the electric double layer capacitor. When the input voltage is less than the first set voltage, a second mode of control is performed in which the second switching element is switched based on the current flowing through the second switching element and the output voltage output from the output terminal, thereby operating the second switching element and the coil as a step-up circuit to discharge the electric double layer capacitor. In the first mode, the second switching element is operated as a synchronous rectifier element of the step-down circuit, and in the second mode, the first switching element is operated as a synchronous rectifier element of the step-up circuit. It is characterized by the following:

[0015] A control program according to one embodiment of the present invention is: A control program for a backup power supply device comprising: a terminal section having an input terminal, an output terminal, a connection point electrically connected to the output terminal, and an input rectifier element whose anode is electrically connected to the input terminal and whose cathode is electrically connected to the connection point; an electric double-layer capacitor with one end electrically connected to a reference potential; a first switching element with one end electrically connected to the connection point; a coil with one end electrically connected to the other end of the first switching element and the other end electrically connected to the other end of the electric double-layer capacitor; and a second switching element with one end electrically connected to the other end of the first switching element and one end of the coil, and the other end electrically connected to a reference potential; When the input voltage input to the input terminal is equal to or greater than a predetermined first set voltage, a first mode of control is performed in which the first switching element is switched based on the current flowing through the first switching element and the charging voltage of the electric double layer capacitor, thereby operating the first switching element and the coil as a step-down circuit to charge the electric double layer capacitor. When the input voltage is less than the first set voltage, a second mode of control is performed in which the second switching element is switched based on the current flowing through the second switching element and the output voltage output from the output terminal, thereby operating the second switching element and the coil as a step-up circuit to discharge the electric double layer capacitor. In the first mode, the second switching element is operated as a synchronous rectifier element of the step-down circuit, and in the second mode, the first switching element is operated as a synchronous rectifier element of the step-up circuit. The processing unit is instructed to perform this action. [Effects of the Invention]

[0016] A backup power supply device, control method, and control program according to one aspect of the present invention have the effect of reducing the number of components. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 shows the configuration of the backup power supply device according to the embodiment. [Figure 2] Figure 2 shows the circuit configuration of the battery voltage drop monitoring unit and the mode switching timing adjustment unit of the backup power supply device according to the embodiment. [Figure 3] Figure 3 shows the circuit configuration of the switching frequency setting section of the backup power supply device according to the embodiment. [Figure 4] Figure 4 shows an example of a sawtooth wave signal and a periodic pulse signal from the backup power supply device of the embodiment. [Figure 5]Figure 5 shows the circuit configuration of the switching current detection unit of the backup power supply device according to the embodiment. [Figure 6] Figure 6 shows the circuit configuration of the current information detection unit of the backup power supply device according to the embodiment. [Figure 7] Figure 7 shows the circuit configuration of the overvoltage detection unit of the backup power supply device according to the embodiment. [Figure 8] Figure 8 shows the circuit configuration of the output voltage error detection unit of the backup power supply device according to the embodiment. [Figure 9] Figure 9 shows an example of the sawtooth wave signal, current information signal, error signal, and main switching control signal of the backup power supply according to the embodiment. [Figure 10] Figure 10 shows the circuit configuration of the drive selection section of the backup power supply device according to the embodiment. [Modes for carrying out the invention]

[0018] Embodiments of the backup power supply, control method, and control program of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments.

[0019] <Embodiment> Figure 1 shows the configuration of the backup power supply device according to the embodiment.

[0020] Backup power supply unit 1 uses the voltage V of battery 2. IN If the input voltage is above a predetermined threshold, the electric double-layer capacitor 3 is charged using the power supplied from the battery 2 via input terminals 1a and 1b.

[0021] The input voltage threshold corresponds to an example of the "first set voltage" in this disclosure.

[0022] Backup power supply unit 1 uses the voltage V of battery 2. INIf the input voltage is below the threshold voltage, the power stored in the electric double-layer capacitor 3 is used to output a DC voltage from output terminal 1c. The power output from output terminal 1c is used to power electronic equipment (not shown).

[0023] Battery 2 is exemplified by, but is not limited to, an auxiliary battery mounted in a vehicle. IN The input voltage threshold is exemplified as 12V or 24V, but is not limited thereto. The input voltage threshold is exemplified as 9V, but is not limited thereto.

[0024] Backup power supply 1 is connected from resistor R1 to resistor R 12 The circuit includes a capacitor C1, an electric double-layer capacitor 3, a step-up / step-down circuit 4, a terminal section 5, and a control unit 10. The step-up / step-down circuit 4 includes switching elements Q1 and Q2 and a coil L1. The terminal section 5 includes input terminals 1a and 1b, an output terminal 1c, and a diode D1.

[0025] Input terminal 1a is electrically connected to the high-potential side of battery 2. Input terminal 1b is electrically connected to the low-potential side of battery 2. The low-potential side of battery 2 is electrically connected to a reference potential. The reference potential is exemplified by, but is not limited to, the ground potential.

[0026] One end of resistor R1 is electrically connected to the high-potential input terminal 1a. The other end of resistor R1 is electrically connected to one end of resistor R2. The other end of resistor R2 is electrically connected to the low-potential input terminal 1b. Resistors R1 and R2 are connected to the voltage V IN The voltage V1 obtained by dividing the voltage by a resistor is output to the control unit 10. In other words, V1 = V IN The formula is ÷(R1+R2)×R2.

[0027] The anode of diode D1 is electrically connected to input terminal 1a. The cathode of diode D1 is electrically connected to node N1.

[0028] Node N1 corresponds to an example of the "connection point" of the present disclosure.

[0029] Diode D1 has a voltage V IN which is the voltage V of node N1 N1 When it is higher, it allows the current to pass from battery 2 to node N1. Diode D1 has a voltage V IN which is N1 When it is lower than the voltage V, it blocks the current flowing from node N1 to battery 2.

[0030] One end of capacitor C1 is electrically connected to node N1. The other end of capacitor C1 is electrically connected to input terminal 1b. Capacitor C1 stabilizes and smoothes the voltage V N1 .

[0031] When the backup power supply device 1 charges the electric double layer capacitor 3, the voltage V N1 is the input voltage, that is, the voltage V IN . When the backup power supply device 1 discharges the electric double layer capacitor 3, the voltage V N1 is the output voltage.

[0032] One end of resistor R3 is electrically connected to node N1. The other end of resistor R3 is electrically connected to one end of resistor R4. The other end of resistor R4 is electrically connected to input terminal 1b. Resistors R3 and R4 output the voltage V2 obtained by resistive voltage division of the voltage V N1 to the control unit 10. That is, V2 = V N1 ÷(R3 + R4)×R4.

[0033] When the backup power supply device 1 charges the electric double layer capacitor 3, the voltage V2 is a voltage proportional to the input voltage, that is, the voltage V IN (= voltage V N1 ). When the backup power supply device 1 discharges the electric double layer capacitor 3, the voltage V2 is a voltage proportional to the output voltage, that is, the voltage V N1 .

[0034] One end of resistor R5 is electrically connected to node N1. The other end of resistor R5 is electrically connected to the drain of switching element Q1. The voltage V6 at one end of resistor R5 and the voltage V7 at the other end of resistor R5 are input to the control unit 10.

[0035] The source of the switching element Q1 is electrically connected to one end of the coil L1. A switching control signal S1 is input to the gate of the switching element Q1 from the control unit 10 via a resistor R6.

[0036] Switching element Q1 corresponds to an example of the "first switching element" in this disclosure.

[0037] In this disclosure, each switching element is assumed to be a MOSFET, but this is not limited to this. Each switching element may also be a silicon power device, GaN power device, SiC power device, IGBT (Insulated Gate Bipolar Transistor), etc.

[0038] Each switching element has a parasitic diode (body diode). A parasitic diode is the pn junction between the back gate and the source and drain of a MOSFET. The parasitic diode can be used as a freewheeling diode to dissipate transient back electromotive force when the transistor is turned off.

[0039] The control unit 10 can detect the current flowing between the drain and source of the switching element Q1 based on the voltage across the resistor R5, that is, the difference between voltage V6 and voltage V7.

[0040] In this embodiment, the backup power supply 1 is provided with a resistor R5, but this disclosure is not limited to this. The control unit 10 may also detect the current flowing between the drain and source of the switching element Q1 based on the voltage between the drain and source of the switching element Q1. In this case, the backup power supply 1 does not need to provide a resistor R5. However, the on-resistance of the switching element Q1 is more susceptible to temperature changes than that of the resistor R5. Therefore, the backup power supply 1 should be provided with a resistor R5 if high precision is required, and the on-resistance of the switching element Q1 should be used if high precision is not required.

[0041] The drain of switching element Q2 is electrically connected to the source of switching element Q1 and one end of coil L1. The source of switching element Q2 is electrically connected to one end of resistor R8. The other end of resistor R8 is electrically connected to input terminal 1b. A switching control signal S2 is input to the gate of switching element Q2 from the control unit 10 via resistor R7.

[0042] Switching element Q2 corresponds to an example of the "second switching element" in this disclosure.

[0043] One end of resistor R9 is electrically connected to the source of switching element Q2 and one end of resistor R8. The voltage V4 from the source of switching element Q2 and one end of resistor R8 is input to the control unit 10 via resistor R9.

[0044] Resistance R 10 One end is electrically connected to the source of the switching element Q2 and one end of the resistor R8. The voltage V5 at the source of the switching element Q2 and one end of the resistor R8 is 10 It is input to the control unit 10 via [this method].

[0045] The control unit 10 can detect the current flowing between the drain and source of the switching element Q2 based on the voltage across the resistor R8, i.e., voltage V4 or voltage V5.

[0046] In this embodiment, the backup power supply 1 is provided with a resistor R8, but this disclosure is not limited to this. The control unit 10 may also detect the current flowing between the drain and source of the switching element Q2 based on the voltage between the drain and source of the switching element Q2. In this case, the backup power supply 1 does not need to provide a resistor R8. However, the on-resistance of the switching element Q2 is more susceptible to temperature changes than that of the resistor R8. Therefore, the backup power supply 1 should be provided with a resistor R8 if high precision is required, and the on-resistance of the switching element Q2 should be used if high precision is not required.

[0047] The other end of coil L1 is electrically connected to one end (high potential side) of electric double-layer capacitor 3. The other end (low potential side) of electric double-layer capacitor 3 is electrically connected to input terminal 1b.

[0048] Resistance R 11 One end is electrically connected to one end of the electric double-layer capacitor 3. Resistor R 11 The other end is a resistor R 12 It is electrically connected to one end of the resistor R. 12 The other end is electrically connected to the other end of electric double-layer capacitor 3. Resistor R 11 and resistor R 12 The voltage V across electric double-layer capacitor 3 is EDLC The voltage V3 obtained by dividing the voltage by a resistor is output to the control unit 10. In other words, V3 = V EDLC ÷(R 11 +R 12 )×R 12 That is the case.

[0049] The control unit 10 controls the step-up / step-down circuit 4 based on voltages V1 to V7.

[0050] In the mode in which the electric double-layer capacitor 3 is charged (hereinafter referred to as "first mode"), the control unit 10 controls the voltage V INThe buck-boost circuit 4 is controlled to step down the voltage and output it to the electric double-layer capacitor 3. In the first mode, the input voltage of the buck-boost circuit 4 is the voltage V IN The output voltage is voltage V EDLC That is the case.

[0051] In the first mode, the control unit 10 operates the switching element Q1 and the coil L1 as a step-down circuit. In the first mode, the control unit 10 also operates the switching element Q1 as the main switching element and the switching element Q2 as a synchronous rectifier element.

[0052] In the mode in which the electric double-layer capacitor 3 is discharged (hereinafter referred to as "second mode"), the control unit 10 controls the voltage V EDLC The step-up / step-down circuit 4 is controlled to boost the voltage and output it to output terminal 1c. In the second mode, the input voltage of the step-up / step-down circuit 4 is voltage V EDLC The output voltage is voltage V N1 That is the case.

[0053] In the second mode, the control unit 10 operates the switching element Q2 and the coil L1 as a boost circuit. In the second mode, the control unit 10 also operates the switching element Q2 as the main switching element and the switching element Q1 as a synchronous rectifier element.

[0054] The control unit 10 includes a battery voltage drop monitoring unit 11, a mode switching timing adjustment unit 12, a switching frequency setting unit 13, a switching current detection unit 14, a current information detection unit 15, an overvoltage detection unit 16, an output voltage error detection unit 17, an on / off control unit 18, a drive selection unit 19, a first level shift unit 20, a second level shift unit 21, and gate drive circuits B1 and B2.

[0055] The battery voltage drop monitoring unit 11 monitors the voltage V1 of the battery 2. INThe system monitors whether the input voltage has fallen below the threshold. The mode switching timing adjustment unit 12, based on the output signal from the battery voltage drop monitoring unit 11, sets a mode signal S representing the first mode or the second mode. MODE This is switched at the beginning of the switching cycle.

[0056] Figure 2 shows the circuit configuration of the battery voltage drop monitoring unit and the mode switching timing adjustment unit of the backup power supply device according to the embodiment.

[0057] The battery voltage drop monitoring unit 11 includes a comparator 31 and a constant voltage source 32. The voltage of the constant voltage source 32 is input to the non-inverting input terminal (+ terminal) of the comparator 31. The voltage of the constant voltage source 32 is a voltage corresponding to the input voltage threshold. Specifically, the voltage of the constant voltage source 32 is ((input voltage threshold) ÷ (R1 + R2) × R2). The voltage V1 is input to the inverting input terminal (- terminal) of the comparator 31.

[0058] The comparator 31 outputs a low-level signal when the voltage V1 is equal to or greater than the voltage of the constant voltage source 32. In other words, the comparator 31 outputs a low-level signal when the voltage V1 is equal to or greater than the voltage of the battery 2. IN If the input voltage is above the threshold, a low-level signal is output.

[0059] On the other hand, the comparator 31 outputs a high-level signal when the voltage V1 is less than the voltage of the constant voltage source 32. In other words, the comparator 31 outputs a high-level signal when the voltage V1 is less than the voltage of the battery 2. IN If the input voltage is below the threshold, a high-level signal is output.

[0060] The mode switching timing adjustment unit 12 includes a D-type flip-flop 41 and a one-shot circuit 42.

[0061] The output signal from comparator 31 is input to terminal D (signal input terminal) of type D flip-flop 41.

[0062] The one-shot circuit 42 receives a periodic pulse signal S representing the switching period. OSC(As described later) At the timing when the level changes from low to high, a one-shot pulse is output to the T terminal (trigger input terminal) of the D-type flip-flop 41.

[0063] The D-type flip-flop 41 captures the output signal of the comparator 31 at the timing when the one-shot pulse input from the one-shot circuit 42 changes from a low level to a high level. The D-type flip-flop 41 receives a mode signal S representing the mode from its inverting output terminal (Q-bar terminal). MODE Outputs.

[0064] Mode signal S MODE A high level indicates the first mode (charging mode), and a low level indicates the second mode (discharging mode).

[0065] Referring again to Figure 1, the switching frequency setting unit 13 receives the mode signal S MODE Based on this, a periodic pulse signal S representing the switching frequency is used. OSC Outputs.

[0066] Figure 3 shows the circuit configuration of the switching frequency setting section of the backup power supply device according to the embodiment.

[0067] The switching frequency setting unit 13 includes NOT gate circuits (inverting circuits) 51 and 61, constant current sources 52, 53, 56 and 57, transfer gate circuits 54, 55, 58, 64 and 65, a capacitor 59, a comparator 60, and constant voltage sources 62 and 63.

[0068] The switching frequency setting unit 13 corresponds to an example of the "sawtooth wave generation circuit" of this disclosure.

[0069] The NOT gate circuit 51 receives the mode signal S MODE The signal is inverted and output to transfer gate circuits 54 and 58. Therefore, transfer gate circuits 54 and 58 receive the mode signal S. MODE When the signal level is high (first mode), it turns off, and the mode signal SMODE It turns on when the level is low (second mode).

[0070] The low-potential side of capacitor 59 is electrically connected to the reference potential.

[0071] The constant current source 52 is electrically connected between the power supply potential VDD and the high-potential side of the capacitor 59.

[0072] One end of the constant current source 53 is electrically connected to the power supply potential VDD. The other end of the constant current source 53 is electrically connected to the high-potential side of the capacitor 59 via the transfer gate circuit 54.

[0073] Mode signal S MODE When the mode signal S is at a high level (first mode), the transfer gate circuit 54 is turned off. Therefore, the capacitor 59 is charged only by the constant current source 52. MODE When the mode signal S is low (second mode), the transfer gate circuit 54 turns on. Therefore, the capacitor 59 is charged by both constant current sources 52 and 53. In other words, the capacitor 59 is charged by the mode signal S MODE The charging current changes depending on the signal value, which in turn changes the rate at which the voltage rises.

[0074] The voltage at the high-potential side of capacitor 59 corresponds to the sawtooth wave signal S. SAW That is the case.

[0075] The inverting input terminal (- terminal) of comparator 60 is electrically connected to the high-potential side of capacitor 59. The non-inverting input terminal (+ terminal) of comparator 60 is electrically connected to constant voltage source 62 via transfer gate circuit 64 and to constant voltage source 63 via transfer gate circuit 65.

[0076] The transfer gate circuit 64 is turned on when the output signal of the comparator 60 is high level, and turned off when the output signal of the comparator 60 is low level.

[0077] The NOT gate circuit 61 inverts the output signal of the comparator 60 and outputs it to the transfer gate circuits 55 and 65. Therefore, the transfer gate circuits 55 and 65 are in the off state when the output signal of the comparator 60 is high level, and in the on state when the output signal of the comparator 60 is low level.

[0078] Comparator 60 outputs a high-level signal if the voltage across capacitor 59 is less than the reference voltage (voltage from constant voltage source 62 or 63). When the output signal of comparator 60 is high-level, the transfer gate circuit 64 is turned on, and the voltage from constant voltage source 62 is input as the reference voltage to the non-inverting input terminal of comparator 60.

[0079] Comparator 60 outputs a low-level signal when the voltage across capacitor 59 is equal to or greater than the reference voltage (voltage from constant voltage source 62 or 63). When the output signal of comparator 60 is low-level, the transfer gate circuit 65 is turned on, and the voltage from constant voltage source 63 is input as the reference voltage to the non-inverting input terminal of comparator 60.

[0080] In other words, the reference voltage of comparator 60 is different when it changes from a low level to a high level and when the output signal changes from a high level to a low level.

[0081] The output signal of comparator 60 is a periodic pulse signal S OSC That is the case.

[0082] One end of the transfer gate circuit 55 is electrically connected to the high-potential side of the capacitor 59.

[0083] The constant current source 56 is electrically connected between the other end of the transfer gate circuit 55 and the reference potential.

[0084] One end of the transfer gate circuit 58 is electrically connected to the other end of the transfer gate circuit 55.

[0085] The constant current source 57 is electrically connected between the transfer gate circuit 58 and the reference potential.

[0086] Mode signal S MODE When the mode signal S is at a high level (first mode), the capacitor 59 is discharged solely by the constant current source 56. MODE When the mode signal S is low (second mode), the transfer gate circuit 58 turns on. Therefore, the capacitor 59 is discharged by both constant current sources 56 and 57. In other words, the capacitor 59 is discharged by the mode signal S MODE The discharge current changes depending on the signal value, which in turn changes the rate at which the voltage drops.

[0087] In summary, capacitor 59 controls the mode signal S MODE When the signal level is high (first mode), charging and discharging occur at a relatively slow speed. Therefore, the sawtooth wave signal S SAW and periodic pulse signal S OSC The frequency becomes relatively lower.

[0088] On the other hand, capacitor 59 receives the mode signal S MODE When the signal is at a low level (second mode), it charges and discharges at a relatively fast speed. Therefore, the sawtooth wave signal S SAW and periodic pulse signal S OSC The frequency becomes relatively higher.

[0089] Figure 4 shows an example of a sawtooth wave signal and a periodic pulse signal from the backup power supply device of the embodiment.

[0090] Sawtooth wave signal S SAW The sawtooth wave signal S begins to rise from timing t0. SAW The rate of increase depends on the current values ​​of the constant current sources 52 and 53. Periodic pulse signal S OSC This becomes high at timing t0.

[0091] Periodic pulse signal S OSC This is a sawtooth wave signal S SAW Voltage V 100 The periodic pulse signal S becomes low at timing t1 when it reaches (the voltage of the constant voltage source 62). OSC When the voltage becomes low, the reference voltage becomes voltage V 100 (voltage of constant voltage source 62) to voltage V 101 Switches to (voltage of constant voltage source 63). Sawtooth wave signal S SAW The sawtooth wave signal S begins to decline from timing t1. SAW The speed of the descent depends on the current values ​​of the constant current sources 56 and 57.

[0092] Periodic pulse signal S OSC This is a sawtooth wave signal S SAW Voltage V 101 At timing t2, when it reaches this point, the signal becomes high level. Periodic pulse signal S OSC When the level becomes high, the reference voltage becomes voltage V 101 From voltage V 100 Switches to: Sawtooth wave signal S SAW It begins to rise from timing t2.

[0093] Referring again to Figure 1, the first level shift unit 20 level shifts voltages V6 and V7 to ground level voltage and outputs it to the switching current detection unit 14.

[0094] The switching current detection unit 14 detects, based on the voltages after voltages V6 and V7 have been level-shifted, that the current flowing through resistor R5, i.e., the drain-source current of switching element Q1, has reached zero or reversed.

[0095] Furthermore, the switching current detection unit 14 detects, based on the voltage V4, that the current flowing through the resistor R8, i.e., the drain-source current of the switching element Q2, has reached zero or reversed.

[0096] In the first mode, the switching current detection unit 14 issues an inversion detection signal S when the current flowing between the drain and source of the switching element Q2, which is a synchronous rectifier element, reaches zero or inverts. REV This is output to the on / off control unit 18.

[0097] Furthermore, in the second mode, the switching current detection unit 14 signals an inversion detection signal S when the current flowing between the drain and source of the switching element Q1, which is a synchronous rectifier element, reaches zero or inverts. REV This is output to the ON / OFF control unit 18.

[0098] Figure 5 shows the circuit configuration of the switching current detection unit of the backup power supply device according to the embodiment.

[0099] The switching current detection unit 14 includes comparators 121 and 122, transfer gate circuits 123 and 124, and a NOT gate circuit 125.

[0100] The inverting input terminal (- terminal) of comparator 121 is electrically connected to the reference potential. The output signal of the first level shift unit 20 is input to the non-inverting input terminal (+ terminal) of comparator 121. If the output signal of the first level shift unit 20 is greater than zero, comparator 121 outputs a high-level signal, and if the output signal of the first level shift unit 20 is zero or less, it outputs a low-level signal.

[0101] The inverting input terminal (- terminal) of comparator 122 is electrically connected to a reference potential. Voltage V4 is input to the non-inverting input terminal (+ terminal) of comparator 122. Comparator 122 outputs a high-level signal when voltage V4 is greater than zero, and outputs a low-level signal when voltage V4 is less than or equal to zero.

[0102] The NOT gate circuit 125 receives the mode signal S MODE The signal is inverted and output to the transfer gate circuit 124.

[0103] The transfer gate circuit 123 outputs the output signal of the comparator 121 as the inversion detection signal S MODE when the mode signal S REV is at a high level.

[0104] The transfer gate circuit 124 outputs the output signal of the comparator 122 as the inversion detection signal S MODE when the mode signal S REV is at a low level.

[0105] Referring to FIG. 1 again, the second level shifter 21 level-shifts the voltages V6 and V7 to the voltage of the ground level and outputs them to the current information detector 15.

[0106] In the case of the first mode, the current information detector 15 detects the current information of the drain-source current of the switching element Q1 which is the main switching element.

[0107] In the case of the second mode, the current information detector 15 detects the current information of the drain-source current of the switching element Q2 which is the main switching element.

[0108] FIG. 6 is a diagram showing the circuit configuration of the current information detector of the backup power supply device of the embodiment.

[0109] The current information detector 15 includes a first voltage-current converter 71, diodes 72, 75 and 79, a resistor 73, a second voltage-current converter 74, a NOT gate circuit 77, transfer gate circuits 76 and 80, and a third voltage-current converter 78.

[0110] The first voltage-current converter 71 converts the voltage of the sawtooth wave signal S SAW into a current and outputs it.

[0111] The anode of diode 72 is electrically connected to the first voltage-current conversion unit 71. The cathode of diode 72 is electrically connected to one end of resistor 73. The connection point between the cathode of diode 72 and one end of resistor 73 is node N2. The other end of resistor 73 is electrically connected to a reference potential.

[0112] The voltage at node N2 corresponds to the current information signal S. CINFO That is the case.

[0113] The second voltage-to-current conversion unit 74 converts the voltages V6 and V7, after level shifting, into current and outputs it.

[0114] The anode of diode 75 is electrically connected to the second voltage-current conversion unit 74. The cathode of diode 75 is electrically connected to node N2.

[0115] The transfer gate circuit 76 is electrically connected between the anode of the diode 75 and the reference potential.

[0116] The NOT gate circuit 77 receives the mode signal S MODE The signal is inverted and output to the transfer gate circuit 76. Therefore, the transfer gate circuit 76 outputs the mode signal S MODE When the signal level is high (first mode), it turns off, and the mode signal S MODE It turns on when the level is low (second mode).

[0117] When the transfer gate circuit 76 is in the off state, the output current of the second voltage-current conversion unit 74 flows to node N2 via the diode 75. When the transfer gate circuit 76 is in the on state, the output current of the second voltage-current conversion unit 74 flows to the reference potential.

[0118] The third voltage-to-current conversion unit 78 converts the voltage V5 into a current and outputs it.

[0119] The anode of the diode 79 is electrically connected to the third voltage-current conversion unit 78. The cathode of the diode 79 is electrically connected to the node N2.

[0120] The transfer gate circuit 80 is electrically connected between the anode of the diode 79 and the reference potential.

[0121] The transfer gate circuit 80 is in the on state when the mode signal S MODE is at a high level (first mode), and is in the off state when the mode signal S MODE is at a low level (second mode). [[ID=1十四]]

[0122] When the transfer gate circuit 80 is in the on state, the output current of the third voltage-current conversion unit 78 flows to the reference potential. When the transfer gate circuit 80 is in the off state, the output current of the third voltage-current conversion unit 78 flows to the node N2 via the diode 79.

[0123] Summarizing the above, when the mode signal S MODE is at a high level (first mode), the sum of the output current of the first voltage-current conversion unit 71 and the output current of the second voltage-current conversion unit 74 flows through the node N2. That is, the current information signal S CINFO becomes a signal in which the information of the drain-source current of the switching element Q1, which is the main switching element, is added to the sawtooth wave signal S SAW .

[0124] On the other hand, when the mode signal S MODE is at a low level (second mode), the sum of the output current of the first voltage-current conversion unit 71 and the output current of the third voltage-current conversion unit 78 flows through the node N2. That is, the current information signal S CINFO becomes a signal in which the information of the drain-source current of the switching element Q2, which is the main switching element, is added to the sawtooth wave signal S SAW .

[0125] Referring to FIG. 1 again, the overvoltage detection unit 16, in the first mode, the output voltage of the buck-boost circuit 4 (voltage VEDLC If an overvoltage is detected, an overvoltage detection signal S OVP Outputs.

[0126] In the second mode, the overvoltage detection unit 16 detects the output voltage (voltage V) of the step-up / step-down circuit 4. N1 If an overvoltage is detected, an overvoltage detection signal S OVP Outputs.

[0127] Figure 7 shows the circuit configuration of the overvoltage detection unit of the backup power supply device according to the embodiment.

[0128] The overvoltage detection unit 16 includes a comparator 101, constant voltage sources 102 and 103, transfer gate circuits 104, 105, 106 and 107, and a NOT gate circuit 108.

[0129] Comparator 101 corresponds to an example of the "overvoltage protection circuit" described herein.

[0130] The inverting input terminal (- terminal) of comparator 101 is electrically connected to constant voltage source 102 via transfer gate circuit 104, and is also electrically connected to constant voltage source 103 via transfer gate circuit 105.

[0131] The voltage of the constant voltage source 102 is the output voltage (Voltage V) of the step-up / step-down circuit 4 in the first mode. EDLC The voltage corresponds to a predetermined first overvoltage threshold, which is the overvoltage threshold of ). For details, the voltage of the constant voltage source 102 is ((first overvoltage threshold) ÷ (R 11 +R 12 )×R 12 )

[0132] The voltage of the constant voltage source 103 is the output voltage (Voltage V) of the step-up / step-down circuit 4 in the second mode. N1 This is the voltage corresponding to a predetermined second overvoltage threshold, which is the overvoltage threshold of ). More specifically, the voltage of the constant voltage source 103 is ((second overvoltage threshold) ÷ (R3 + R4) × R4).

[0133] The first overvoltage threshold corresponds to an example of the "second set voltage" in this disclosure. The second overvoltage threshold corresponds to an example of the "third set voltage" in this disclosure.

[0134] The NOT gate circuit 108 receives the mode signal S MODE The signal is inverted and output to transfer gate circuits 105 and 107.

[0135] The transfer gate circuit 104 receives the mode signal S MODE When the signal is at a high level (first mode), it turns on, and the mode signal S MODE It turns off when it is at a low level (second mode).

[0136] The transfer gate circuit 105 receives the mode signal S MODE When the signal is at a high level (first mode), it turns off, and the mode signal S MODE It turns on when the level is low (second mode).

[0137] Voltage V3 is input to the non-inverting input terminal (+ terminal) of comparator 101 via transfer gate circuit 106. Additionally, voltage V2 is input to the non-inverting input terminal of comparator 101 via transfer gate circuit 107.

[0138] The transfer gate circuit 106 receives the mode signal S MODE When the signal is at a high level (first mode), it turns on, and the mode signal S MODE It turns off when it is at a low level (second mode).

[0139] The transfer gate circuit 107 receives the mode signal S MODE When the signal is at a high level (first mode), it turns off, and the mode signal S MODE It turns on when the level is low (second mode).

[0140] In summary, in the first mode, the comparator 101 is activated when the voltage V3 is greater than or equal to the voltage of the constant voltage source 102, that is, when the voltage V3 is greater than or equal to the output voltage of the step-up / step-down circuit 4. EDLC If the value is above the first overvoltage threshold, a high-level overvoltage detection signal S is issued. OVP It outputs the following. Also, in the second mode, the comparator 101 outputs the voltage V2 when the voltage V2 is greater than or equal to the voltage of the constant voltage source 103, that is, the voltage V which is the output voltage of the step-up / step-down circuit 4. N1 If the value is above the second overvoltage threshold, a high-level overvoltage detection signal S is issued. OVP Outputs.

[0141] Referring again to Figure 1, the output voltage error detection unit 17 detects the output voltage (voltage V) of the step-up / step-down circuit 4 in the first mode. EDLC Error signal S represents the error between the target voltage and the error signal S. ERR Outputs.

[0142] In the second mode, the output voltage error detection unit 17 detects the output voltage (voltage V) of the step-up / step-down circuit 4. N1 Error signal S represents the error between the target voltage and the error signal S. ERR Outputs.

[0143] Figure 8 shows the circuit configuration of the output voltage error detection unit of the backup power supply device according to the embodiment.

[0144] The output voltage error detection unit 17 includes error amplifiers (operational amplifiers) 81 and 85, constant voltage sources 82 and 86, resistors 83 and 87, capacitors 84 and 88, transfer gate circuits 89 and 90, and a NOT gate circuit 91.

[0145] The voltage from the constant voltage source 82 is input to the non-inverting input terminal (+ terminal) of the error amplifier 81. The voltage from the constant voltage source 82 is the output voltage (voltage V) of the step-up / step-down circuit 4 in the second mode. N1 This is the voltage corresponding to the target voltage of ). For details, the voltage of the constant voltage source 82 is ((Voltage V N1 The formula is (target voltage) ÷ (R3 + R4) × R4).

[0146] A voltage V2 is input to the inverting input terminal (- terminal) of the error amplifier 81. Negative feedback is applied between the inverting input terminal and the output terminal of the error amplifier 81 by a resistor 83 and a capacitor 84. The error amplifier 81 outputs a voltage corresponding to the voltage difference between the voltage of the constant voltage source 82 and the voltage V2.

[0147] The voltage from the constant voltage source 86 is input to the non-inverting input terminal (+ terminal) of the error amplifier 85. The voltage from the constant voltage source 86 is the output voltage (V) of the step-up / step-down circuit 4 in the first mode. EDLC This is the voltage corresponding to the target voltage of ). For details, the voltage of the constant voltage source 86 is ((Voltage V EDLC (Target voltage)÷(R) 11 +R 12 )×R 12 )

[0148] A voltage V3 is input to the inverting input terminal (- terminal) of the error amplifier 85. Negative feedback is applied between the inverting input terminal and the output terminal of the error amplifier 85 by a resistor 87 and a capacitor 88. The error amplifier 85 outputs a voltage corresponding to the voltage difference between the voltage of the constant voltage source 86 and the voltage V3.

[0149] The NOT gate circuit 91 receives the mode signal S MODE The signal is inverted and output to the transfer gate circuit 89. Therefore, the transfer gate circuit 89 outputs the mode signal S MODE When the signal level is high (first mode), it turns off, and the mode signal S MODE It turns on when the level is low (second mode).

[0150] The transfer gate circuit 90 receives the mode signal S MODE It turns on when the mode signal S is at a high level (first mode), and MODE It turns off when it is at a low level (second mode).

[0151] In summary, the output voltage error detection unit 17 detects the mode signal S MODEWhen the error signal S is at a high level (first mode), a voltage corresponding to the difference between voltage V3 and the voltage of the constant voltage source 86 is generated. ERR It outputs as follows: In other words, the output voltage error detection unit 17 detects the voltage V, which is the output voltage of the step-up / step-down circuit 4. EDLC Error signal S corresponding to the voltage difference between the target voltage (e.g., 3V) and the target voltage. ERR Outputs.

[0152] On the other hand, the output voltage error detection unit 17 detects the mode signal S MODE When the voltage is low (second mode), the voltage corresponding to the difference between the voltage V2 and the voltage of the constant voltage source 82 is set to the error signal S. ERR It outputs as follows: In other words, the output voltage error detection unit 17 detects the voltage V, which is the output voltage of the step-up / step-down circuit 4. N1 Error signal S corresponding to the voltage difference between the target voltage (e.g., 12V) and the target voltage. ERR Outputs.

[0153] Referring again to Figure 1, the on / off control unit 18 controls the periodic pulse signal S OSC , inversion detection signal S REV , current information signal S CINFO Overvoltage detection signal S OVP and error signal S ERR Based on this, the main switching control signal S for controlling the main switching element. SW1 , and a synchronous rectification switching control signal S for controlling the synchronous rectification element. SW2 This is output to the drive selection unit 19.

[0154] In the first mode, the on / off control unit 18 controls the switching of switching element Q1, and during a portion of the period when switching element Q1 is off, it turns on switching element Q2. In other words, the on / off control unit 18 operates switching element Q1 as the main switching element and switching element Q2 as a synchronous rectifier element, performing synchronous rectification control.

[0155] In the second mode, the on / off control unit 18 controls the switching of switching element Q2, and also turns on switching element Q1 during a portion of the period when switching element Q2 is off. In other words, the on / off control unit 18 operates switching element Q2 as the main switching element and switching element Q1 as a synchronous rectifier element, performing synchronous rectification control.

[0156] The on / off control unit 18 controls the main switching control signal S SW1 , and synchronous rectification switching control signal S SW2 The frequency of the periodic pulse signal S OSC Adjust to the frequency. Periodic pulse signal S OSC The frequency is higher in the second mode than in the first mode. In other words, the main switching control signal S SW1 , and synchronous rectification switching control signal S SW2 The frequency is higher in the second mode than in the first mode.

[0157] The on / off control unit 18 controls the main switching element and the synchronous rectifier element so that the output voltage of the step-up / step-down circuit 4 approaches the target voltage. Error signal S ERR In the first mode, the voltage V is the output voltage of the step-up / step-down circuit 4. EDLC This is a signal corresponding to the voltage difference between the current voltage and the target voltage. Error signal S ERR In the second mode, the voltage V is the output voltage of the step-up / step-down circuit 4. N1 This is a signal corresponding to the voltage difference between the current voltage and the target voltage.

[0158] The on / off control unit 18 receives the inversion detection signal S REV When the signal reaches a high level, the synchronous rectifier element is controlled to turn off. In other words, in the first mode, the on / off control unit 18 controls the inversion detection signal S. REV When the signal reaches a high level, the switching element Q2, which is a synchronous rectifier element, is controlled to turn off. In addition, in the second mode, the on / off control unit 18 receives the inversion detection signal S REV When the signal reaches a high level, the switching element Q1, which is a synchronous rectifier element, is controlled to be turned off.

[0159] The on / off control unit 18 receives the overvoltage detection signal S OVP If the voltage reaches a high level, the main switching element and the synchronous rectifier element will be shut down.

[0160] The on / off control unit 18 receives a sawtooth wave signal S SAW The current information signal S is obtained by adding the drain-source current of the main switching element to this signal. CINFO Based on this, the main switching element and the synchronous rectifier element are controlled in current mode.

[0161] Figure 9 shows an example of the sawtooth wave signal, current information signal, error signal, and main switching control signal of the backup power supply according to the embodiment.

[0162] Figure 9(a) shows the sawtooth wave signal S SAW When no drain-source current is applied to the main switching element, i.e., in the case of voltage mode control, the main switching control signal S SW1 This is a diagram.

[0163] The on / off control unit 18 receives a sawtooth wave signal S SAW The timing when the rise begins 10 In this case, the main switching control signal S SW1 To raise the level.

[0164] The on / off control unit 18 receives a sawtooth wave signal S SAW Error signal S ERR The timing reached 11 In this, the main switching control signal S SW1 Lower the level.

[0165] Figure 9(b) shows the sawtooth wave signal S SAW When a drain-source current is applied to the main switching element, that is, in the case of current-mode control, the main switching control signal S SW1 This is a diagram.

[0166] Signal 111 indicates the drain-source current of the main switching element. Current information signal SCINFO This is a sawtooth wave signal S SAW This is the signal with signal 111 added to it.

[0167] The on / off control unit 18 receives the current information signal S CINFO The timing when the rise begins 20 In this, the main switching control signal S SW1 To raise the level.

[0168] The on / off control unit 18 receives the current information signal S CINFO Error signal S ERR The timing reached 21 In this, the main switching control signal S SW1 Set to a low level. Main switching control signal S SW1 When the signal level drops to a low level, the main switching element turns off, causing signal 111 to drop to a low level.

[0169] Referring again to Figure 1, the drive selection unit 19 receives the mode signal S MODE If it is at a high level (first mode), the main switching control signal S SW1 The signal is output to the gate drive circuit B1, and the synchronous rectification switching control signal S SW2 This is output to gate drive circuit B2.

[0170] The drive selection unit 19 receives the mode signal S MODE When it is at a low level (second mode), the main switching control signal S SW1 The signal is output to gate drive circuit B2, and the synchronous rectification switching control signal S SW2 This is output to gate drive circuit B1.

[0171] Figure 10 shows the circuit configuration of the drive selection section of the backup power supply device according to the embodiment.

[0172] The drive selection unit 19 includes AND gate circuits (logical conjunction circuits) 131, 132, 134, and 135, OR gate circuits (logical disjunction circuits) 133 and 136, and a NOT gate circuit 137.

[0173] The NOT gate circuit 137 receives the mode signal S MODE The result is inverted and output to one input terminal of AND gate circuit 132 and one input terminal of AND gate circuit 134.

[0174] One input terminal of the AND gate circuit 131 receives a mode signal S MODE The following is input, and the main switching control signal S is input to the other input terminal. SW1 The following is entered.

[0175] The other input terminal of the AND gate circuit 132 is connected to a synchronous rectification switching control signal S SW2 The following is entered.

[0176] The other input terminal of the AND gate circuit 134 is connected to the main switching control signal S SW1 The following is entered.

[0177] One input terminal of the AND gate circuit 135 receives a mode signal S MODE The following is input: the other input terminal receives a synchronous rectification switching control signal S SW2 The following is entered.

[0178] The output signal of the AND gate circuit 131 is input to one input terminal of the OR gate circuit 133, and the output signal of the AND gate circuit 132 is input to the other input terminal.

[0179] The OR gate circuit 133 receives the mode signal S MODE If it is at a high level (first mode), the main switching control signal S SW1 This is output to gate drive circuit B1.

[0180] The OR gate circuit 133 receives the mode signal S MODE When it is at a low level (second mode), the synchronous rectification switching control signal S SW2 This is output to gate drive circuit B1.

[0181] The output signal of the AND gate circuit 134 is input to one input terminal of the OR gate circuit 136, and the output signal of the AND gate circuit 135 is input to the other input terminal.

[0182] The OR gate circuit 136 receives the mode signal S MODE When it is at a high level (first mode), the synchronous rectification switching control signal S SW2 This is output to gate drive circuit B2.

[0183] The OR gate circuit 136 receives the mode signal S MODE When it is at a low level (second mode), the main switching control signal S SW1 This is output to gate drive circuit B2.

[0184] Referring again to Figure 1, the gate drive circuit B1 receives the mode signal S MODE If it is at a high level (first mode), the main switching control signal S SW1 The amplified switching control signal S1 is output to the gate of the switching element Q1.

[0185] The gate drive circuit B1 receives the mode signal S MODE When it is at a low level (second mode), the synchronous rectification switching control signal S SW2 The amplified switching control signal S1 is output to the gate of the switching element Q1.

[0186] The gate drive circuit B2 receives the mode signal S MODE When it is at a high level (first mode), the synchronous rectification switching control signal S SW2 The amplified switching control signal S2 is output to the gate of the switching element Q2.

[0187] The gate drive circuit B2 receives the mode signal S MODE When it is at a low level (second mode), the main switching control signal S SW1 The amplified switching control signal S2 is output to the gate of the switching element Q2.

[0188] (effect) [1] The backup power supply device described in Patent Document 1 controls only the second switching element during discharge, and does not control (does not operate) the first switching element. In other words, the backup power supply device described in Patent Document 1 performs asynchronous rectification.

[0189] On the other hand, the backup power supply device 1 of the embodiment controls the switching of the switching element Q2 during discharge (second mode), and turns on the switching element Q1 for a portion of the period when the switching element Q2 is off. In other words, the backup power supply device 1 of the embodiment operates the switching element Q1 as a synchronous rectifier element and performs synchronous rectification.

[0190] As a result, the backup power supply device 1 of this embodiment does not require an output rectifier element compared to the backup power supply device described in Patent Document 1, thereby reducing the number of components.

[0191] The backup power supply device described in Patent Document 1 controls only the first switching element during charging, and does not control (does not operate) the second switching element, allowing it to function as a diode. In other words, the backup power supply device described in Patent Document 1 performs asynchronous rectification.

[0192] On the other hand, the backup power supply device 1 of the embodiment controls the switching element Q1 during charging (first mode), and turns on the switching element Q2 for a portion of the period when the switching element Q1 is off. In other words, the backup power supply device 1 of the embodiment operates the switching element Q2 as a synchronous rectifier element and performs synchronous rectification.

[0193] As a result, the backup power supply device 1 of this embodiment can suppress losses and improve efficiency compared to the backup power supply device described in Patent Document 1.

[0194] [2] In the backup power supply device 1 of the embodiment, when in discontinuous current operation (light load), if the synchronous rectifier element remains on, a reverse current will flow, and energy will be regenerated to the input side, resulting in a decrease in efficiency. Also, in the backup power supply device 1 of the embodiment, when the charging voltage of the electric double layer capacitor 3 rises, the regenerated energy becomes larger than the charging energy, and it becomes impossible to charge up to the target voltage. Therefore, the backup power supply device 1 of the embodiment turns off the synchronous rectifier element at the timing when the coil L1 sweeps out energy and the current between the drain and source of the synchronous rectifier element becomes zero or reverses, that is, at the timing when the reverse detection signal S REV becomes high level. Thereby, the backup power supply device 1 of the embodiment can suppress the reverse current and suppress the decrease in efficiency. Also, the backup power supply device 1 of the embodiment can charge the charging voltage of the electric double layer capacitor 3 up to the target voltage.

[0195] [3] The backup power supply device 1 of the embodiment can charge while limiting the charging current in the first mode. However, in the backup power supply device 1 of the embodiment, in the second mode, since it has to supply power while boosting the power required by the electronic device, a large current can flow in the circuit.

[0196] Therefore, if the switching frequency setting unit 13 keeps the switching frequency in the second mode the same as in the first mode, the size of the coil L1 has to be increased. On the other hand, in the backup power supply device 1 of the embodiment, in the first mode, it is desirable not to increase the switching frequency too much from the perspective of noise suppression.

[0197] Thus, the switching frequency setting unit 13 sets the switching frequency in the second mode to be higher than the switching frequency in the first mode. Thereby, the backup power supply device 1 of the embodiment can suppress the size of the coil L1 and suppress noise.

[0198] [4] In the first mode, the backup power supply 1 of the embodiment has the voltage V of the electric double layer capacitor 3, which is the output voltage of the step-up / step-down circuit 4. EDLC Control is performed based on the voltage difference between the current voltage and the target voltage (specifically, based on voltage V3). In the second mode, the backup power supply 1 of this embodiment controls the voltage V3, which is the output voltage of the step-up / step-down circuit 4. N1 Control is performed based on the voltage difference between the current voltage and the target voltage (specifically, based on voltage V2).

[0199] However, problems can arise if the input side of a single error amplifier is switched using the two voltages mentioned above during mode switching. In other words, since the input voltage of the error amplifier is switched to a completely different voltage level during mode switching, the output voltage of the error amplifier before mode switching and the output voltage of the error amplifier after mode switching will be completely different voltages. Consequently, response delays or unstable operation of the error amplifier's output voltage may occur.

[0200] Therefore, the output voltage error detection unit 17 (see Figure 8) is equipped with two error amplifiers 81 and 85, and switches the output sides of error amplifiers 81 and 85 when switching modes. As a result, error amplifiers 81 and 85 continuously output output voltages corresponding to their respective input voltages (even when not being used for control), which suppresses response delays and unstable operation during mode switching.

[0201] [5] Unlike an error amplifier, a comparator can switch the input voltage to a different voltage level. Therefore, the overvoltage detection unit 16 (see Figure 7) is equipped with one comparator 101 and switches the input voltage of the comparator 101 according to the mode. That is, in the first mode, the voltage of the electric double layer capacitor 3 V EDLC The voltage V3 obtained by dividing the voltage by a resistor is input to the comparator 101. In the second mode, the output voltage V N1 The voltage obtained by dividing the voltage using resistors is switched on the input side of comparator 101.

[0202] As a result, the backup power supply unit 1 of this embodiment can detect overvoltage in both the first and second modes using a single comparator 101, thereby suppressing the circuit.

[0203] [6] Generally, current mode control allows for easier phase compensation than voltage mode control, and it is possible to set the response to be higher (increase the frequency gain). Therefore, the on / off control unit 18 receives the current information signal S CINFO It employs current mode control that takes this into account. However, the current detection point differs between the first mode and the second mode.

[0204] Therefore, the current information detection unit 15 (see Figure 6) detects the sawtooth wave signal S SAW The current information applied is switched depending on the mode. Specifically, in the first mode, the current information detection unit 15 detects the current information of the current flowing between the drain and source of the main switching element, switching element Q1. In the second mode, the current information detection unit 15 detects the current information of the current flowing between the drain and source of the main switching element, switching element Q2.

[0205] As a result, the backup power supply unit 1 of this embodiment can achieve current mode control in either the first mode or the second mode.

[0206] [7] The first mode and the second mode are completely different controls. Therefore, if a mode switch is performed in the middle of a switching cycle, it will result in abnormal operation, even though it is only one switching cycle.

[0207] Therefore, the mode switching timing adjustment unit 12 (see Figure 2) adjusts the mode change condition, i.e., the voltage V, in the middle of the switching cycle. IN Even if the relative magnitudes of the input voltage threshold change, the start of the next switching cycle, i.e., the periodic pulse signal S OSC Wait until the rise time of the mode signal S MODE Switching this setting allows the backup power supply unit 1 of this embodiment to suppress the abnormal operation described above.

[0208] <Note> In this embodiment, the control unit 10 is configured with hardware circuitry, but this disclosure is not limited thereto. The control unit 10 may also be configured with a processing unit (CPU (Central Processing Unit), DSP (Digital Signal Processor), etc.) and a program.

[0209] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0210] 1. Backup power supply 2 batteries 3. Electric double-layer capacitor 4. Step-up / Step-down Circuit 5 Terminal section 10 Control Unit 11. Battery voltage drop monitoring unit 12 Mode switching timing adjustment section 13 Switching frequency setting section 14 Switching current detection unit 15 Current Information Detection Unit 16 Overvoltage detection unit 17 Output voltage error detection unit 18 On / Off Control Unit 19 Drive Selection Section 20. First Level Shift Section 21 Second Level Shift Section Q1, Q2 switching elements L1 coil

Claims

1. A terminal section having an input terminal, an output terminal, a connection point electrically connected to the output terminal, and an input rectifier element whose anode is electrically connected to the input terminal and whose cathode is electrically connected to the connection point, An electric double-layer capacitor, one end of which is electrically connected to a reference potential, A first switching element, one end of which is electrically connected to the connection point, A coil having one end electrically connected to the other end of the first switching element and the other end electrically connected to the other end of the electric double layer capacitor, A second switching element, one end of which is electrically connected to the other end of the first switching element and one end of the coil, and the other end of which is electrically connected to a reference potential, A control unit comprising an on / off control unit, a battery voltage drop monitoring unit, a mode switching timing adjustment unit, a switching frequency setting unit, a switching current detection unit, and a current information detection unit, Equipped with, The on / off control unit performs a first mode of control, in which, when the battery voltage input to the input terminal is equal to or greater than a predetermined first set voltage, it switches the first switching element based on the current flowing through the first switching element and the charging voltage of the electric double layer capacitor, thereby operating the first switching element and the coil as a step-down circuit to charge the electric double layer capacitor, and when the charging voltage of the electric double layer capacitor becomes equal to or greater than a predetermined second set voltage, it stops the switching operation of the first switching element and the second switching element; and when the battery voltage is less than the first set voltage, it switches the second switching element based on the current flowing through the second switching element and the output voltage output from the output terminal, thereby operating the second switching element and the coil as a step-up circuit to discharge the electric double layer capacitor, and when the output voltage becomes equal to or greater than a predetermined third set voltage, it stops the switching operation of the first switching element and the second switching element. The battery voltage drop monitoring unit monitors whether the battery voltage has dropped below a first set voltage based on the voltage obtained by resistively dividing the battery voltage, and outputs a high-level signal if the battery voltage is below the first set voltage, and outputs a low-level signal if the battery voltage is at or above the first set voltage. The mode switching timing adjustment unit switches the mode signal representing control of the first mode or the second mode based on the level signal output from the battery voltage drop monitoring unit at the timing of the beginning of the switching cycle, such that when the level signal is high, it represents control of the first mode, and when the level signal is low, it represents control of the second mode. The switching frequency setting unit outputs a periodic pulse signal representing the switching frequency to the on / off control unit based on the mode signal. In the first mode, the switching current detection unit outputs an inversion detection signal to the on / off control unit when the current flowing through the second switching element included in the boost circuit reaches zero or reverses; and in the second mode, the switching current detection unit outputs an inversion detection signal when the current flowing through the first switching element included in the boost circuit reaches zero or reverses. The current information detection unit detects the current of the first switching element in the first mode, and detects the current of the second switching element in the second mode, and outputs the current information signal to the on / off control unit. The on / off control unit switches modes based on the periodic pulse signal, the inversion detection signal, and the current information signal, so that in the first mode, the first switching element operates as the main switching element and the second switching element operates as the synchronous rectifier element of the step-down circuit, and in the second mode, the second switching element operates as the main switching element and the first switching element operates as the synchronous rectifier element of the step-up circuit. A backup power supply device characterized by the following features.

2. One end of the first switching element is electrically connected to the connection point via a resistor, The control unit, It comprises a first level shift section and a second level shift section, The first level shift unit level shifts the voltage across the resistor to the ground level voltage and outputs it to the switching current detection unit, detecting the current flowing through the resistor as the current flowing through the first switching element. The second level shift unit level shifts the voltage across the resistor to the ground level voltage and outputs it to the current information detection unit, detecting the current flowing through the resistor as the current flowing through the first switching element. The backup power supply device according to claim 1, characterized in that...

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