Power supply device

Abstract

A power supply device according to an aspect of the present disclosure comprises: a power supply IC including a switching circuit having a pair of switching elements that are switched in a ratio that matches the circuit characteristics of the output side and that connect an output node to a primary power supply voltage or to ground, and an internal control circuit that controls the switching circuit, the power supply IC having an internal input terminal that accepts input of the primary power supply voltage, an internal output terminal that outputs a square-wave voltage outputted from the switching elements, a tracking terminal that accepts input of a tracking voltage that sets the voltage value of the output voltage, and a feedback terminal that accepts input of a feedback voltage indicating the actual voltage value of the output voltage; an output inductor with one end connected to the internal output terminal; an output capacitor connected to the other end of the output inductor; a tracking grounding circuit capable of grounding the tracking terminal; and a tracking control circuit that controls the tracking grounding circuit.

Description

power supply

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

[0002] Power supply ICs are used that step down a primary power supply voltage to a set voltage and output the stepped-down voltage. One example is a DC / DC converter that includes a power supply IC having a high-side switching element that applies the primary power supply voltage to an output node and a low-side switching element that grounds the output node, and switches the high-side switching element and the low-side switching element in response to the difference between the set voltage and the output voltage. Furthermore, an inductor (coil) and a capacitor (capacitor) that is charged via the inductor are generally connected to the output of the power supply IC. In this case, the output voltage of the capacitor is fed back to the power supply IC, and the high-side switching element and the low-side switching element are controlled to maintain the output voltage of the capacitor at the set voltage (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-78203

[0004] In the DC / DC converter described above, even if the output of the power supply IC is stopped, the output voltage will not drop unless the charge stored in the capacitor is consumed by the load. Depending on the overall device configuration including the load, it may be necessary to quickly drop the output voltage when the primary power supply voltage to the power supply device is cut off.

[0005] A power supply device according to one embodiment of the present disclosure includes a switching circuit having a pair of switching elements that are switched at a ratio that matches the circuit characteristics on the output side and connect the output node to a primary power supply voltage or ground, and an internal control circuit that controls the switching circuit, and is equipped with a power supply IC having an internal input terminal to which the primary power supply voltage is input, an output terminal that outputs a rectangular wave voltage generated by the switching element, a tracking terminal to which a tracking voltage that sets the voltage value of the output voltage is input, and a feedback terminal to which a feedback voltage that indicates the actual voltage value of the output voltage is input, an output inductor having one end connected to the output terminal, an output capacitor connected to the other end of the output inductor, a tracking ground circuit that can ground the tracking terminal, and a tracking control circuit that controls the tracking ground circuit.

[0006] 1 is a circuit diagram of a power supply device according to a first embodiment of the present disclosure, a circuit diagram of a power supply device according to a second embodiment of the present disclosure, and a circuit diagram of a power supply device according to a third embodiment of the present disclosure.

[0007] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that in the following embodiments, similar components will be designated by the same reference numerals, and redundant description may be omitted.

[0008] 1 is a circuit diagram of a power supply device 1 according to a first embodiment of the present disclosure. The power supply device 1 includes a power supply IC 10, an output inductor 21, an output capacitor 22, an output feedback circuit 30, a tracking ground circuit 40, and a tracking control circuit 50. The power supply device 1 also has an input terminal 61 to which a primary power supply voltage (input voltage) Vin is input, an output terminal 62 to which an output voltage Vout is output, and a setting terminal 63 to which a tracking voltage Vtr that sets the voltage value of the output voltage Vout is input.

[0009] The power supply IC 10 includes a switching circuit 11 and an internal control circuit 12 that controls the switching circuit 11. The power supply IC 10 also has an internal input terminal 13 to which a primary power supply voltage Vin is input, an internal output terminal 14 that outputs a rectangular wave voltage Vvr output from the switching circuit 11, a tracking terminal 15 to which a tracking voltage Vtr that sets the voltage value of the output voltage Vout is input, and a feedback terminal 16 to which a feedback voltage Vfb that indicates the voltage value of the actual output voltage Vout is fed back.

[0010] The switching circuit 11 may have a well-known configuration having a high-side transistor 111 and its gate driver 112 that apply a primary power supply voltage Vin to an internal output terminal 14 (output node), a low-side transistor 113 that grounds the internal output terminal 14 and its gate driver 114, and a converter controller 115 that inputs drive signals to the high-side transistor 111 and the low-side transistor 113 so as to switch the switching state at a ratio that matches the circuit characteristics on the output side.

[0011] The internal control circuit 12 may be configured to include, for example, a reference voltage circuit 121 that generates a reference voltage Vref from the primary power supply voltage Vin, and a differential amplifier circuit 122 that generates a differential voltage Vdf between the lower of the tracking voltage Vtr and the reference voltage Vref and the feedback voltage Vfb (Vtr-Vfb if the tracking voltage Vtr does not exceed the reference voltage Vref). Note that the reference voltage Vref is generally used to determine the final control voltage, but can be omitted if control is continued using the input voltage Vtr as the reference voltage.

[0012] The output inductor 21 has one end connected to the internal output terminal 14 and the other end connected to the output capacitor 22. The output inductor 21 and the output capacitor 22 are well-known components that smooth the rectangular wave voltage output by the operation of the high-side transistor 111 and the low-side transistor 113. By connecting the output inductor 21 and the output capacitor 22 to the switching circuit 11, a synchronous rectification type DC / DC converter is formed that can generate an output voltage Vout having a desired voltage value from the primary power supply voltage Vin.

[0013] The output feedback circuit 30 generates a feedback voltage Vfb indicating the voltage value of the output voltage Vout by dividing the output voltage Vout, and inputs the generated feedback voltage Vfb to the feedback terminal 16 of the power supply IC 10 .

[0014] The tracking ground circuit 40 is configured to be able to ground the tracking terminal 15. In other words, the tracking ground circuit 40 immediately reduces the tracking voltage Vtr to ground level by discharging the current input from the setting terminal 63 to ground. This reduces the differential voltage Vdf output by the differential amplifier circuit 122, causing the switching circuit 11 to operate to extract the charge stored in the output capacitor 22. The above operation of the switching circuit 11 acts as a boost operation from the output voltage Vout to the primary power supply voltage Vin, allowing power to be regenerated to the primary power supply side. Therefore, by grounding the tracking terminal 15 using the tracking ground circuit 40, the power supply device 1 can quickly reduce the output voltage Vout to ground level.

[0015] The tracking ground circuit 40 of this embodiment is an open-collector output circuit. Specifically, the tracking ground circuit 40 includes, for example, a field-effect transistor 41, the drain (collector) of which is connected to the tracking terminal 15, the source (emitter) of which is grounded, and a drive signal is input to the gate (base) of the transistor 41 from the tracking control circuit 50. To enable the use of a transistor 41 that operates with a relatively small current, a limiting resistor 631 is provided between the setting terminal 63 and the tracking terminal 15, and the tracking ground circuit 40 can be connected downstream of the limiting resistor 631.

[0016] The tracking control circuit 50 outputs a control signal for controlling the tracking ground circuit 40, i.e., turns on and off the gate voltage of the transistor 41. The tracking control circuit 50 is configured to supply a gate current to close the transistor 41 when the voltage of the primary power supply voltage Vin drops. As a specific example, the tracking control circuit 50 can be a logic circuit that inverts a voltage monitor signal of the primary power supply voltage Vin.

[0017] As described above, power supply device 1 can quickly discharge output capacitor 22 by grounding tracking terminal 15, which has almost no capacitance, via tracking ground circuit 40. Therefore, power supply device 1 can quickly reduce output voltage Vout when primary power supply voltage Vin is cut off.

[0018] 2 is a circuit diagram of a power supply device 1A according to a second embodiment of the present disclosure. The power supply device 1A includes a power supply IC 10A, an output inductor 21, an output capacitor 22, an output feedback circuit 30, a tracking voltage generation circuit 70, a tracking ground circuit 40A, and a tracking control circuit 50A. The power supply device 1 also has an input terminal 61 to which a primary power supply voltage Vin is input, an output terminal 62 to which an output voltage Vout is output, and a setting terminal 63 to which a tracking voltage Vtr that sets the voltage value of the output voltage Vout is input.

[0019] The power supply IC 10A includes a switching circuit 11 and an internal control circuit 12A that controls the switching circuit 11. The power supply IC 10A also has an internal input terminal 13, an internal output terminal 14, a tracking terminal 15, a feedback terminal 16, and a soft start terminal 17.

[0020] The internal control circuit 12A may be configured to include a reference voltage circuit 121 that generates a reference voltage Vref, a soft start circuit 123 that generates a soft start voltage Vss that rises slowly when the primary power supply voltage Vin is input to the power supply IC 10A, and a differential amplifier circuit 122 that generates a differential voltage Vdf between the feedback voltage Vfb and the lower of the tracking voltage Vtr and the soft start voltage Vss (within a range not exceeding the reference voltage Vref).

[0021] The soft start circuit 123 includes a constant current circuit 1231 that outputs a constant charging current when the primary power supply voltage Vin is input, and is connected to a soft start capacitor 171 that is charged by the charging current via a soft start terminal 17, and generates a soft start voltage Vss as the terminal voltage of the soft start capacitor 171. The constant current circuit 1231 can be configured to adjust the current supplied from the reference voltage circuit 121.

[0022] The tracking voltage generating circuit 70 is connected to the tracking terminal 15 and generates the tracking voltage Vtr. Specifically, the tracking voltage generating circuit 70 of this embodiment is configured as a regulator that generates the tracking voltage Vtr from the primary power supply voltage Vin, and the tracking voltage Vtr is determined by its resistance value.

[0023] The tracking ground circuit 40A of this embodiment is a push-pull output circuit that connects the output to ground or a predetermined potential. Such a tracking ground circuit 40A can be constructed, for example, using an IC that uses CMOS as the output interface, and therefore can be implemented relatively inexpensively. The tracking ground circuit 40A of this embodiment is connected to the tracking terminal 15 via a limiting diode 42. The limiting diode 42 prevents the tracking voltage Vtr from increasing due to the current output from the tracking ground circuit 40A. Therefore, the inclusion of the limiting diode 42 broadens the selection of ICs that can be used as the tracking ground circuit 40A.

[0024] The tracking control circuit 50A can be configured using other components of the IC that configures the tracking ground circuit 40A. This allows the power supply device 1A to be relatively inexpensive. In a power supply device 1A configured so that the tracking voltage Vtr and the soft-start voltage Vss are input to the differential amplifier circuit 122, the tracking control circuit 50A may ground the tracking terminal 15 via the tracking ground circuit 40A a certain time after the output of the constant current circuit 1231 is stopped when the output of the output voltage Vout is stopped, for example, when the input of the primary power supply voltage Vin is interrupted or when a signal such as an abnormal signal is input. This allows the output voltage Vout to be reduced in accordance with the soft-start voltage Vss immediately after the output stop process begins, thereby suppressing inrush current from the output capacitor 22 to the switching circuit 11 of the power supply IC 10A, and the tracking voltage Vtr to be reduced to ground level when the soft-start capacitor 171 has discharged to a certain extent, thereby quickly completing the discharge of the output capacitor 22.

[0025] The power supply device 1A of this embodiment includes a power supply IC 10A having a soft start circuit 123, which suppresses the rise speed of the output voltage Vout and prevents excessive inrush current. Furthermore, when the output voltage Vout falls, the power supply device 1A uses the tracking ground circuit 40A to reduce the tracking voltage Vtr to the ground level, thereby quickly reducing the output voltage Vout.

[0026] 3 is a circuit diagram of a power supply device 1B according to a third embodiment of the present disclosure. The power supply device 1B includes a power supply IC 10B, an output inductor 21, an output capacitor 22, an output feedback circuit 30, a tracking voltage generation circuit 70B, a tracking ground circuit 40, and a tracking control circuit 50.

[0027] The power supply IC 10B may be configured to include a reference voltage circuit 121 that generates a reference voltage Vref, a differential amplifier circuit 122 that generates a differential voltage Vdf between the tracking voltage Vtr and the feedback voltage Vfb, and a constant current circuit 124 that outputs a constant charging current to the tracking terminal 15 when the primary power supply voltage Vin is input to the power supply IC 10B.

[0028] The tracking voltage generating circuit 70B has a soft start capacitor 71 that is connected to the tracking terminal 15 and that generates a terminal voltage that becomes the tracking voltage Vtr by being charged by a charging current output from the constant current circuit 124.

[0029] In this embodiment, the tracking ground circuit 40 grounds the tracking terminal 15 via an adjustment resistor 43. The adjustment resistor 43 slows down the falling speed of the tracking voltage Vtr and protects the power supply IC 10 from discharge current. In this embodiment, the tracking ground circuit 40 is connected to the tracking terminal 15 via the adjustment resistor 43, but the source of the transistor 41 may also be connected to ground via the adjustment resistor 43.

[0030] In power supply 1B of this embodiment, tracking voltage Vtr rises and falls as a result of charging and discharging soft-start capacitor 71. When tracking ground circuit 40 is not used, the decrease in tracking voltage Vtr due to the discharge of soft-start capacitor 71 occurs relatively slowly due to the current consumption of differential amplifier circuit 122. However, this decrease can be made more rapid by grounding the output terminal of soft-start capacitor 71 using tracking ground circuit 40. In power supply 1B of this embodiment as well, tracking control circuit 50 may adjust the discharge current by activating tracking ground circuit 40 in response to an appropriate trigger, such as a drop in primary power supply voltage Vin, a drop in a voltage different from Vin, or an abnormal system state, and grounding tracking terminal 15 via adjustment resistor 43.

[0031] The following supplementary notes are further provided regarding the above-described embodiment and modifications. (Supplementary Note 1) The power supply device (1, 1A, 1B) includes a switching circuit (11) having a pair of switching elements (111, 113) that are switched at a ratio in accordance with the circuit characteristics on the output side and connect an output node to a primary power supply voltage or ground, and an internal control circuit (12, 12A, 12B) that controls the switching circuit (11), and is equipped with a power supply IC (10, 10A, 10B) having an internal input terminal (13) to which the primary power supply voltage is input, an internal output terminal (14) that outputs a rectangular wave voltage output from the switching element, a tracking terminal (15) to which a tracking voltage that sets the voltage value of the output voltage is input, and a feedback terminal (16) to which a feedback voltage that indicates the voltage value of the actual output voltage is input, an output inductor (21) one end of which is connected to the internal output terminal (14), an output capacitor (22) connected to the other end of the inductor (21), a tracking ground circuit (40, 40A) that can ground the tracking terminal (15), and a tracking control circuit (50, 50A) that controls the tracking ground circuit (40, 40A).

[0032] (Supplementary Note 2) In the power supply device (1A) of Supplementary Note 1, the internal control circuit (12A) may have a soft start circuit (123) including a constant current circuit (1231) that outputs a constant charging current, connected to a soft start capacitor (171) that is charged by the charging current, and that generates a soft start voltage that is the terminal voltage of the soft start capacitor (171), and a differential amplifier circuit (122) that generates a differential voltage between the lower of the tracking voltage and the soft start voltage and the feedback voltage.

[0033] (Supplementary Note 3) The power supply device (1B) of Supplementary Note 1 may further include a tracking voltage generation circuit (70B) connected to the tracking terminal (15) and generating a tracking voltage, the internal control circuit (12B) having a constant current circuit (124) that outputs a constant charging current when a primary power supply voltage is input, and the tracking voltage generation circuit (70B) having a soft start capacitor (71) that generates a terminal voltage that is the tracking voltage by being charged with the charging current.

[0034] (Appendix 4) In the power supply device (1A, 1B) of Appendix 2 or 3, when the tracking control circuit (50, 50A) stops outputting the output voltage, the tracking control circuit (50, 50A) may ground the tracking terminal (15) by the tracking ground circuit (40, 40A) a certain time after the output of the constant current circuit (1231, 124) has stopped.

[0035] (Supplementary Note 5) In the power supply device (1, 1B) of any one of Supplementary Notes 1 to 4, the tracking ground circuit (40) may be an open collector output circuit.

[0036] (Supplementary Note 6) In the power supply device (1B) of Supplementary Note 5, the tracking ground circuit may ground the tracking terminal (15) via a resistor.

[0037] (Supplementary Note 7) In the power supply device (1A) of any one of Supplementary Notes 1 to 4, the tracking ground circuit (40A) may be a push-pull output circuit.

[0038] (Supplementary Note 8) In the power supply device (1A) of Supplementary Note 7, the tracking ground circuit (40A) may be connected to the tracking terminal (15) via a diode (42).

[0039] (Supplementary Note 9) In the power supply device of Supplementary Note 7, the tracking ground circuit may be connected to the tracking terminal via a resistor.

[0040] Although the present disclosure has been described in detail above, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the present disclosure or the gist of the present disclosure derived from the content of the claims and their equivalents. Furthermore, these embodiments can also be implemented in combination.

[0041] For example, in the power supply devices of the various embodiments, the tracking ground circuit may be either an open-collector circuit or a push-pull output circuit. Therefore, a tracking ground circuit having a push-pull output may be connected via an adjustable resistor to a tracking terminal connected to a tracking voltage setting circuit having a soft-start capacitor. Furthermore, if the voltage range of the internal control circuit and the voltage range of the output voltage are the same, the undivided temporary power supply voltage and output voltage may be used as the reference voltage and feedback voltage.

[0042] In the power supply device of the present disclosure, the open collector circuit that constitutes the tracking ground circuit can be a single transistor or a circuit whose output is an open collector, such as a comparator with a transistor, a photocoupler, an integrated circuit, etc.

[0043] 1, 1A, 1B Power supply device 10, 10A, 10B Power supply IC 11 Switching circuit 111 High-voltage side transistor 112, 114 Gate driver 113 Low-voltage side transistor 115 Converter controller 12, 12A Internal control circuit 121 Reference voltage circuit 122 Differential amplifier circuit 123 Soft start circuit 1231, 124 Constant current circuit 13 Internal input terminal 14 Internal output terminal 15 Tracking terminal 16 Feedback terminal 17 Soft start terminal 171, 71 Soft start capacitor 21 Output inductor 22 Output capacitor 30 Output feedback circuit 40, 40A Tracking ground circuit 41 Transistor 42 Limiting diode 43 Adjustment resistor 50, 50A Tracking control circuit 61 Input terminal 62 Output terminal 63 Setting terminal 631 Limiting resistor 70, 70B Tracking voltage generation circuit

Claims

1. A power supply device comprising: a switching circuit having a pair of switching elements which are switched at a ratio according to the circuit characteristics on the output side and which connect an output node to a primary power supply voltage or ground; and an internal control circuit which controls the switching circuit, the power supply IC having an internal input terminal to which the primary power supply voltage is input, an internal output terminal which outputs a rectangular wave voltage output from the switching elements, a tracking terminal to which a tracking voltage which sets a voltage value of an output voltage is input, and a feedback terminal to which a feedback voltage which indicates an actual voltage value of the output voltage is input; an output inductor connected to the internal output terminal; an output capacitor connected to the output inductor; a tracking ground circuit capable of grounding the tracking terminal; and a tracking control circuit which controls the tracking ground circuit.

2. The power supply device according to claim 1, wherein said internal control circuit comprises: a soft start circuit including a constant current circuit that outputs a constant charging current, to which a soft start capacitor charged by said charging current is connected, and that generates a soft start voltage which is the terminal voltage of said soft start capacitor; and a differential amplifier circuit that generates a differential voltage between the feedback voltage and the lower of said tracking voltage and said soft start voltage.

3. The power supply device according to claim 1, further comprising a tracking voltage generation circuit connected to said tracking terminal and generating said tracking voltage, said internal control circuit having a constant current circuit which outputs a constant charging current, and said tracking voltage generation circuit having a soft start capacitor which generates a terminal voltage which becomes said tracking voltage by being charged by said charging current.

4. A power supply device as described in claim 2 or 3, wherein when the tracking control circuit stops outputting the output voltage, the tracking control circuit grounds the tracking terminal via the tracking ground circuit a certain time after the output of the constant current circuit is stopped.

5. A power supply device according to any one of claims 1 to 4, wherein the tracking ground circuit is an open collector output circuit.

6. The power supply device according to claim 5, wherein said tracking ground circuit grounds said tracking terminal through a resistor.

7. A power supply device according to any one of claims 1 to 4, wherein the tracking ground circuit is a push-pull output circuit.

8. The power supply device of claim 7, wherein said tracking ground circuit is connected to said tracking terminal through a diode.

9. The power supply device according to claim 7 or 8, wherein the tracking ground circuit is connected to the tracking terminal via a resistor.

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