Overcurrent detection circuit, switched capacitor converter, and vehicle

Abstract

To provide an overcurrent detection circuit which can detect overcurrent without efficiency deterioration of a switched capacitor converter.SOLUTION: An overcurrent detection circuit (2) is configured to detect overcurrent of current outputted from a switched capacitor converter (SCC2) having a plurality of capacitors (C1 to C3) and a plurality of switching elements (M1 to M8). The overcurrent detection circuit includes: a first application end (T1) configured so that input voltage of the switched capacitor converter is applied; a second application end (T2) configured so that output voltage of the switched capacitor is applied; and detection parts (R1 to R2, R4 to R7, OP1, IS1, Q1 to Q5, COMP1) configured to detect the overcurrent based on a difference between the output voltage and an integer multiple or reciprocal integer multiple of the input voltage.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The invention disclosed in this specification relates to an overcurrent detection circuit, a switched capacitor converter, and a vehicle.

Background Art

[0002] Conventionally, a switched capacitor converter has been used as a power source (see, for example, Patent Document 1).

[0003] A switched capacitor converter has a plurality of switching element connection nodes, and is configured to appropriately connect capacitors between the connection nodes, and converts an input voltage by DC / DC conversion to generate an output voltage.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] One of the protection functions in a power source is an overcurrent protection function. When providing an overcurrent protection function for a switched capacitor converter, which is a type of power source, it is desired not to cause a decrease in the efficiency of the switched capacitor converter.

Means for Solving the Problems

[0006] An overcurrent detection circuit disclosed herein is configured to detect an overcurrent of the current output from a switched capacitor converter having a plurality of capacitors and a plurality of switching elements. The overcurrent detection circuit includes a first application terminal configured to receive the input voltage of the switched capacitor converter, a second application terminal configured to receive the output voltage of the switched capacitor converter, and a detection unit configured to detect the overcurrent based on the difference between the output voltage and an integer multiple or reciprocal integer multiple of the input voltage.

[0007] A switched-capacitor converter disclosed herein comprises the overcurrent detection circuit having the above configuration, the plurality of capacitors, and the plurality of switching elements.

[0008] The vehicles disclosed herein have a switched-capacitor converter with the above configuration. [Effects of the Invention]

[0009] According to the invention disclosed herein, overcurrent can be detected without causing a decrease in the efficiency of the switched-capacitor converter. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows a comparative example of a switched-capacitor converter. [Figure 2] Figure 2 is a timing chart showing the voltages at various points in the switched-capacitor converter shown in Figure 1. [Figure 3] Figure 3 shows an embodiment of a switched-capacitor converter. [Figure 4] Figure 4 shows an example configuration of an overcurrent detection circuit. [Figure 5] Figure 5 shows an example configuration of a constant current source. [Figure 6] Figure 6 is an external view of the vehicle. [Figure 7]Figure 7 shows the first example of a switched-capacitor converter, which has a different topology from the Dixon type. [Figure 8] Figure 8 shows a second example of a switched-capacitor converter, which has a different topology from the Dixon type. [Figure 9] Figure 9 shows a third example of a switched-capacitor converter, which has a different topology from the Dixon type. [Figure 10] Figure 10 shows a fourth example of a switched-capacitor converter, which has a different topology from the Dixon type. [Modes for carrying out the invention]

[0011] In this specification, a MOS (Metal Oxide Semiconductor) field-effect transistor refers to a field-effect transistor whose gate structure consists of at least three layers: a layer made of a conductor or a semiconductor with low resistance such as polysilicon, an insulating layer, and a P-type, N-type, or intrinsic semiconductor layer. In other words, the gate structure of a MOS field-effect transistor is not limited to a three-layer structure of metal, oxide, and semiconductor.

[0012] In this specification, the reference voltage refers to a voltage that is constant under ideal conditions, and in reality, it is a voltage that may fluctuate slightly due to temperature changes, etc.

[0013] In this specification, constant current refers to a current that is constant under ideal conditions, and in reality, it is a current that may fluctuate slightly due to temperature changes, etc.

[0014] <Switched Capacitor Converter (Comparative Example)> Figure 1 shows a comparative example of a switched capacitor converter (a general configuration to be compared with the embodiment described later). The topology of the switched capacitor converter SCC1 in this comparative example is a Dixon topology. Figure 2 is a timing chart showing the voltages of each part of the switched capacitor converter SCC1.

[0015] The switched capacitor converter SCC1 includes switching elements M1 to M8, capacitors C1 to C3, an output capacitor Cout, a control unit CNT1, a sense resistor RSNS, and an overcurrent detection circuit 1.

[0016] The first terminal of the switching element M1 is connected to the positive electrode of the DC voltage source VS1 via the sense resistor RSNS. The negative electrode of the DC voltage source VS1 is connected to the ground potential. The DC voltage source VS1 supplies an input voltage Vin to the first terminal of the switching element M1.

[0017] The second terminal of the switching element M1 is connected to the first terminal of the switching element M2 and the first terminal of the capacitor C3. The second terminal of the switching element M2 is connected to the first terminal of the switching element M3 and the first terminal of the capacitor C2. The second terminal of the switching element M3 is connected to the first terminal of the switching element M4 and the first terminal of the capacitor C1.

[0018] The second terminal of the switching element M4 is connected to the first terminal of the switching element M7, the first terminal of the load LD1, the first terminal of the switching element M6, and the first terminal of the output capacitor Cout. The second terminal of the switching element M7 is connected to the first terminal of the switching element M8, the second terminal of the capacitor C1, and the second terminal of the capacitor C3. The second terminal of the switching element M6 is connected to the first terminal of the switching element M5 and the second terminal of the capacitor C2. The second terminals of the switching element M8, the load LD1, the switching element M5, and the output capacitor Cout are connected to the ground potential.

[0019] The control unit CNT1 controls the switching elements M1, M3, M5, and M7 by the first control signal Φ1 and controls the switching elements M2, M4, M6, and M8 by the second control signal Φ2.

[0020] The control unit CNT1 complementaryly controls the on / off states of switching elements M1, M3, M5, and M7, and switching elements M2, M4, M6, and M8.

[0021] The switching voltage VSW1 switches between the value of Vin and the value of Vin × 3 / 4. The switching voltage VSW1 is generated at the connection node between switching element M1 and switching element M2.

[0022] The switching voltage VSW2 switches between a value of Vin × 3 / 4 and a value of Vin / 2. The switching voltage VSW2 is generated at the connection node between switching element M2 and switching element M3.

[0023] The switching voltage VSW3 switches between the values ​​of Vin / 2 and Vin / 4. The switching voltage VSW3 is generated at the connection node between switching element M3 and switching element M4.

[0024] The switching voltage VSW6 switches between the value of Vin / 4 and 0 (ground potential). The switching voltage VSW6 is generated at the connection node between switching element M5 and switching element M6.

[0025] The switching voltage VSW7 switches between the value of Vin / 4 and 0 (ground potential). The switching voltage VSW7 is generated at the connection node between switching element M7 and switching element M8.

[0026] The output voltage Vout is equal to Vin / 4. The output voltage Vout is generated at the connection node between switching elements M4, M6, and M7. The output voltage Vout is supplied to the load LD1.

[0027] The sense resistor RSNS converts the input current Iin of the switched-capacitor converter SCC1 into a voltage VSNS. The voltage VSNS is supplied to the overcurrent detection circuit 1. The overcurrent detection circuit 1 includes a resistor 11, a capacitor 12, a DC voltage source 13 that outputs a reference voltage VREF, and a comparator 14.

[0028] As the input current Iin is a pulsed current as shown in Figure 2, if the load LD1 is a heavy load, the inrush current at the rising edge of the pulsed current may cause the voltage VSNS to become larger than the reference voltage VREF, potentially leading to false detection of an overcurrent.

[0029] The RC filter, composed of resistor 11 and capacitor 12, smooths the voltage VSNS and prevents false detection of overcurrent. The comparator 14 compares the voltage smoothed by the RC filter with a reference voltage VREF. If the voltage smoothed by the RC filter is greater than or equal to the reference voltage VREF, the comparator 14 detects an overcurrent and sets the overcurrent protection signal OCP to a HIGH level. On the other hand, if the voltage smoothed by the RC filter is less than the reference voltage VREF, the comparator 14 does not detect an overcurrent and sets the overcurrent protection signal OCP to a LOW level.

[0030] If the overcurrent protection signal OCP is at a HIGH level, the control unit CNT1 stops the switching control of switching elements M1 to M8 and performs an overcurrent protection operation that turns off all switching elements M1 to M8.

[0031] The switched-capacitor converter SCC1 suffers from reduced efficiency due to losses in the sense resistor RSNS. Furthermore, the RC filter, composed of resistor 11 and capacitor 12, increases the number of components when it is an external component of the semiconductor integrated circuit device having the control unit CNT1.

[0032] In light of the above considerations, we propose a novel embodiment that can detect overcurrent without causing a decrease in the efficiency of the switched-capacitor converter.

[0033] <Switched Capacitor Converter (Embodiment)> Figure 3 shows an embodiment of the switched capacitor converter. The switched capacitor converter SCC2 of this embodiment differs from the switched capacitor converter SCC1 described above in that it has an overcurrent detection circuit 2 instead of a sense resistor RSNS and an overcurrent detection circuit 1, but is otherwise basically the same as the switched capacitor converter SCC1 described above.

[0034] In a switched-capacitor converter, under no-load conditions, the output voltage is expressed as an integer multiple or an integer reciprocal multiple of the input voltage. In the switched-capacitor converter SCC2, under no-load conditions, the output voltage Vout is 1 / 4 of the input voltage Vin.

[0035] In a switched-capacitor converter, the switching elements are controlled in an open loop without feedback control. Therefore, in a switched-capacitor converter, the output voltage Vout decreases in accordance with the output current Iout. In the switched-capacitor converter SCC2, when there is a load, the following equation (1) holds between the output voltage Vout, the input voltage Vin, and the output current Iout. Vout = Vin / 4 - Rout × Iout …(1)

[0036] When the control unit CNT1 operates the switching elements M1 to M8 at a low switching frequency Fsw, the following equation (2) holds true. The effective capacitance value Cep of the switched-capacitor converter SCC2 can be calculated using the method disclosed, for example, in Michael D. Seeman and Seth R. Sanders, “Analysis and Optimization of Switched-Capacitor DC-DC Converters” (IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 23, NO. 2, MARCH 2008). Rout ≈ 1 / (Cep × Fsw) …(2)

[0037] Since the relationship in equation (1) above holds, the overcurrent detection circuit 2 detects the overcurrent of the output current Iout based on the difference between the output voltage Vout and the reciprocal integer multiple of the input voltage Vin. The overcurrent detection circuit 2 can detect overcurrent without providing a sense resistor RSNS. Therefore, the overcurrent detection circuit 2 can detect overcurrent without causing a decrease in the efficiency of the switched-capacitor converter SCC2.

[0038] Figure 4 shows an example configuration of the overcurrent detection circuit 2. The overcurrent detection circuit 2 shown in Figure 4 includes resistors R1 to R6, an operational amplifier OP1, P-channel type MOS field-effect transistors Q1 to Q3, N-channel type MOS field-effect transistors Q4 and Q5, a constant current source IS51, a comparator COMP1, a first application terminal T1, and a second application terminal T2. The power supply voltage VCC for the overcurrent detection circuit 2 shown in Figure 4 can be, for example, the input voltage Vin.

[0039] The voltage divider circuit, composed of resistors R1 and R2, divides the input voltage Vin applied to the first application terminal T1 to generate a voltage with the value Vin / (4N). The value of N is adjusted by the respective resistance values ​​of resistors R1 and R2. The voltage of Vin / (4N) output from this voltage divider circuit is supplied to the non-inverting input terminal of operational amplifier OP1. The output terminal of operational amplifier OP1 is connected to the inverting input terminal of operational amplifier OP1. As a result, operational amplifier OP1 operates as a buffer amplifier.

[0040] The voltage Vin / (4N) output from op-amp OP1 is supplied to the series circuit of resistors R3 and R4. Specifically, the voltage Vin / (4N) output from op-amp OP1 is supplied to the connection node between resistors R3 and R4.

[0041] The first and second current mirror circuits supply a current corresponding to the constant current Ib output from the constant current source IS1 to the series circuit of resistors R3 and R4. The first current mirror circuit is composed of MOS field-effect transistors Q1 to Q3. The second current mirror circuit is composed of MOS field-effect transistors Q4 and Q5.

[0042] A voltage equal to Vin / (4N)-VREF / N is supplied from the connection node between resistor R4 and MOS field-effect transistor Q5 to the inverting input terminal of comparator COMP1. The value of VREF / N can be adjusted by the constant current Ib and the resistance value of resistor R4.

[0043] The voltage divider circuit, composed of resistors R5 and R6, divides the output voltage Vout applied to the second application terminal T2 to generate a voltage of value Vout / N. The value of N is adjusted by the respective resistance values ​​of resistors R5 and R6. The Vout / N voltage output from this voltage divider circuit is supplied to the non-inverting input terminal of comparator COMP1.

[0044] When the difference between the input voltage Vin and the output voltage Vout widens to VREF (threshold), the overcurrent protection signal OCP output from comparator COMP1 becomes HIGH. If the overcurrent protection signal OCP is at HIGH, control unit CNT1 stops the switching control of switching elements M1 to M8 and performs an overcurrent protection operation that turns off all switching elements M1 to M8.

[0045] Here, the accuracy of the VREF value can be improved by configuring the constant current source IS1 as shown in Figure 5. The constant current source IS1 in the configuration shown in Figure 5 includes an operational amplifier OP2, an N-channel MOS field-effect transistor Q6, and a resistor R7.

[0046] A constant voltage Vb is supplied to the non-inverting input terminal of the operational amplifier OP2. The constant voltage Vb is a high-precision constant voltage, such as a bandgap reference voltage. The output terminal of the operational amplifier OP2 is connected to the gate of the MOS field-effect transistor Q6. The inverting input terminal of the operational amplifier OP2 is connected to the source of the MOS field-effect transistor Q6 and the first terminal of resistor R7. The second terminal of resistor R7 is connected to ground potential.

[0047] The value of the constant current Ib output from the constant current source IS1 in the configuration shown in Figure 5 can be expressed by equation (3) below. In equation (3) below, Ib is the value of the constant current Ib, Vb is the value of the constant voltage Vb, and R9 is the resistance value of resistor R9. Ib = Vb / R9 …(3)

[0048] If the resistance value of resistor R4 is R, then the above VREF can be expressed by equation (4) below. Therefore, by matching the characteristics of resistors R7 and R3, the accuracy of the above VREF is improved, and thus the accuracy of overcurrent detection is improved. Note that, for example, the characteristics of resistors R7 and R3 can be matched by forming them using the same manufacturing process. VREF = Vb × R / R7 …(4)

[0049] <Examples of application> Figure 6 is an external view of vehicle X. In this configuration example, vehicle X is equipped with various electronic devices X11 to X18 that operate using voltage supplied from a battery (not shown). Note that the mounting positions of the electronic devices X11 to X18 in this figure may differ from those in reality for illustrative purposes.

[0050] Electronic device X11 is an engine control unit that performs engine-related controls (such as injection control, electronic throttle control, idle control, oxygen sensor heater control, and auto cruise control).

[0051] Electronic device X12 is a lamp control unit that controls the on / off state of lights such as HID (high-intensity discharged lamps) and DRL (daytime running lamps).

[0052] Electronic device X13 is a transmission control unit that performs control related to the transmission.

[0053] The electronic device X14 is a braking unit that performs control related to the motion of the vehicle X (such as ABS [anti-lock brake system] control, EPS [electric power steering] control, and electronic suspension control).

[0054] Electronic device X15 is a security control unit that controls the operation of door locks, burglary alarms, and other devices.

[0055] Electronic equipment X16 consists of electronic components that are installed in vehicle X at the factory as standard equipment or manufacturer options, including wipers, power door mirrors, power windows, dampers (shock absorbers), power sunroof, and power seats.

[0056] Electronic equipment X17 is an electronic device that can be optionally installed in vehicle X as a user option, such as an in-vehicle A / V (audio / visual) device, a car navigation system, and an ETC (electronic toll collection system).

[0057] Electronic equipment X18 is a type of electronic equipment equipped with high-voltage motors, such as automotive blowers, oil pumps, water pumps, and battery cooling fans.

[0058] Furthermore, the switched-capacitor converter SCC2 described above can be incorporated into any of the electronic devices X11 to X18. Also, the applications of the switched-capacitor converter SCC2 are not limited to power supplies installed in vehicles X; for example, they could also be used as power supplies in industrial equipment.

[0059] <Other> The structure of the invention can be modified in various ways, in addition to the embodiments described above, without departing from the spirit of the invention. The embodiments described above should be considered in all respects to be illustrative and not restrictive, and the technical scope of the present invention is indicated by the claims, not by the description of the embodiments described above, and should be understood to include all modifications that fall within the meaning and scope equivalent to the claims.

[0060] For example, in a switched capacitor converter SCC2, the arrangement of the DC voltage source VS1 and the load LD1 may be swapped. When the arrangement of the DC voltage source VS1 and the load LD1 is swapped, the voltage supplied from the switched capacitor converter SCC2 to the load LD1 (the output voltage of the switched capacitor converter SCC2) becomes greater than the voltage supplied from the DC voltage source VS1 to the switched capacitor converter SCC2 (the input voltage of the switched capacitor converter SCC2). In this case, the overcurrent detection circuit should be configured to detect overcurrent based on the difference between the output voltage of the switched capacitor converter SCC2 and an integer multiple of the input voltage of the switched capacitor converter SCC2.

[0061] The overcurrent detection circuit described above can also be applied to switched-capacitor converters, which have a different topology than the Dixon type. Examples of switched-capacitor converters with a different topology from the Dixon type include the switched-capacitor converters shown in Figures 7 to 10.

[0062] The overcurrent detection circuit (2) described above is an overcurrent detection circuit configured to detect overcurrents in the current output from a switched capacitor converter (SCC2) having a plurality of capacitors (C1 to C3) and a plurality of switching elements (M1 to M8), and has the following configuration (first configuration): a first application terminal (T1) configured to receive the input voltage of the switched capacitor converter, a second application terminal (T2) configured to receive the output voltage of the switched capacitor converter, and a detection unit (R1 to R2, R4 to R7, OP1, IS1, Q1 to Q5, COMP1) configured to detect the overcurrent based on the difference between the output voltage and an integer multiple or an integer reciprocal multiple of the input voltage.

[0063] The overcurrent detection circuit of the first configuration described above can detect overcurrent without causing a decrease in the efficiency of the switched-capacitor converter.

[0064] In the overcurrent detection circuit of the first configuration described above, the detection unit may have a first voltage divider circuit configured to generate a voltage divider of the output voltage, and a second voltage divider circuit configured to generate a voltage divider of the input voltage, and may be configured to detect the overcurrent based on the difference between the output of the first voltage divider circuit and the output of the second voltage divider circuit (second configuration).

[0065] The overcurrent detection circuit of the second configuration described above can process a smaller voltage, thus enabling miniaturization and cost reduction of the overcurrent detection circuit.

[0066] In the overcurrent detection circuit of the first or second configuration described above, the detection unit may have a configuration (third configuration) in which it detects the overcurrent when the difference between the output voltage and an integer multiple or reciprocal integer multiple of the input voltage is greater than or equal to a threshold, and includes a constant current source configured to output a constant current flowing through the first resistor by applying a constant voltage to the first resistor, and a second resistor (R3) configured to supply a current corresponding to the constant current, and the threshold is determined by the voltage drop across the second resistor.

[0067] The overcurrent detection circuit of the third configuration described above can improve the accuracy of overcurrent detection by matching the characteristics of the first resistor and the second resistor.

[0068] The switched-capacitor converter (SCC2) described above has a configuration (fourth configuration) comprising an overcurrent detection circuit in any of the first to third configurations described above, the plurality of capacitors, and the plurality of switching elements.

[0069] The switched-capacitor converter in the fourth configuration described above can detect overcurrent without causing a decrease in efficiency.

[0070] The vehicle (X) described above has a configuration (the fifth configuration) that includes a switched-capacitor converter as described in the seventh configuration above.

[0071] The vehicle with the fifth configuration described above can detect overcurrent without causing a decrease in the efficiency of the switched-capacitor converter. [Explanation of Symbols]

[0072] 1, 2 Overcurrent detection circuit 11 Resistors 12 Capacitors 13 DC voltage source 14 Comparator RSNS Sense Resistance C1~C3 Capacitors Cout output capacitor CNT1 Control Unit COMP1 Comparator IS1 constant current source LD1 load M1~M8 Switching Elements OP1~OP2 Operational Amplifiers Q1-Q6 MOS field-effect transistors R1~R17 Resistors SCC1, SCC2 Switched Capacitor Converters T1~T2 1st~2nd application end VS1 DC voltage source X Vehicle X11~X18 Electronic equipment

Claims

1. Multiple capacitors, An overcurrent detection circuit configured to detect overcurrents in the current output from a switched capacitor converter having a plurality of switching elements, A first application terminal configured to receive the input voltage of the switched capacitor converter, A second application terminal configured to receive the output voltage of the switched capacitor converter, The system includes a detection unit configured to detect the overcurrent based on the difference between the output voltage and an integer multiple or the reciprocal of an integer multiple of the input voltage, The detection unit is The overcurrent is detected when the difference between the output voltage and an integer multiple or reciprocal integer multiple of the input voltage is greater than or equal to a threshold. A constant current source including a first resistor, configured to output a constant current flowing through the first resistor by applying a constant voltage to the first resistor, A second resistor configured to supply a current corresponding to the constant current, It has, An overcurrent detection circuit in which the threshold value is determined by the voltage drop across the second resistor.

2. The detection unit is A first voltage divider circuit configured to generate a voltage divider of the output voltage, It includes a second voltage divider circuit configured to generate a voltage divider of the input voltage, The overcurrent detection circuit according to claim 1, configured to detect the overcurrent based on the difference between the output of the first voltage divider circuit and the output of the second voltage divider circuit.

3. An overcurrent detection circuit according to claim 1 or claim 2, The aforementioned plurality of capacitors, A switched-capacitor converter having the aforementioned plurality of switching elements.

4. A vehicle having the switched-capacitor converter described in claim 3.

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