Power supply apparatus

A power supply apparatus includes a switch, a converting module and a control module. When the switch operates in an ON state, an input voltage is outputted through the switch to serve as an output voltage. The converting module selectively converts the input voltage into the output voltage. When the power supply apparatus operates in a mode where the switch operates in an OFF state, where the converting module performs the conversion, and where the output voltage is stabilized at a target voltage value, and when a condition associated with the input voltage is met, the control module causes the output voltage to gradually change toward the input voltage.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Chinese Patent Application No. 201610081811.8, filed on Feb. 5, 2016.

FIELD

The disclosure relates to power supply, and more particularly to a power supply apparatus operable in multiple modes.

BACKGROUND

A conventional power supply apparatus receives a DC (direct current) input voltage, and outputs a DC output voltage associated with the input voltage. When the input voltage is greater than a predetermined reference voltage value, the conventional power supply apparatus operates in a first mode to output the input voltage as the output voltage. When the input voltage is less than the reference voltage value, the conventional power supply apparatus operates in a second mode to boost-convert the input voltage into the output voltage and stabilize the output voltage at a predetermined target voltage value. The conventional power supply apparatus directly switches from one of the first and second modes to the other of the first and second modes, and thus endures relatively high current stress. In addition, the conventional power supply apparatus causes each of the input and output voltages to have a relatively large ripple component, and as a result, a system using the conventional power supply apparatus has a relatively short lifetime and relatively poor stability.

SUMMARY

Therefore, an object of the disclosure is to provide a power supply apparatus that can alleviate at least one of the drawbacks of the prior art.

According to the disclosure, the power supply apparatus includes an input terminal, an output terminal, a switch, a converting module and a control module. An input voltage is received at the input terminal. An output voltage is outputted at the output terminal. The switch is coupled between the input and output terminals, and is operable between an ON state and an OFF state based on a first control signal. When the switch operates in the ON state, the input voltage is outputted through the switch to serve as the output voltage. The converting module is coupled between the input and output terminals, and selectively converts the input voltage into the output voltage based on a second control signal. The control module is coupled to the input and output terminals, the switch and the converting module, and generates the first and second control signals based at least on the input and output voltages. The power supply apparatus is operable in at least a first mode, where the first control signal is such that the switch operates in the ON state, and where the second control signal is such that the converting module does not perform the conversion, and a second mode, where the first control signal is such that the switch operates in the OFF state, and where the second control signal is generated based on the output voltage in such a way that the converting module performs the conversion and that the output voltage is stabilized at a predetermined target voltage value. When the power supply apparatus operates in the second mode and a condition associated with the input voltage is met, the control module generates the first control signal in such a way that the switch operates in the OFF state, and generates the second control signal in such a way that the converting module performs the conversion and that the output voltage gradually changes toward the input voltage.

DETAILED DESCRIPTION

Referring toFIGS. 1, 2 and 3, a first embodiment of a power supply apparatus according to the disclosure includes an input terminal1, an output terminal2, a first switch3, a converting module4, a control module5and a capacitor6, is used to receive a DC (direct current) input voltage (Vin) and an input current (Iin) at the input terminal1, and outputs a DC output voltage (Vout) at the output terminal2. The input voltage (Vin) is within a range of between a minimum input voltage value (Vin_min) and a maximum input voltage value (Vin_max), i.e., Vin_min≦Vin≦Vin_max. The capacitor6is coupled between the output terminal2and a reference node (e.g., ground), and filters the output voltage (Vout).

The first switch3is coupled between the input and output terminals1,2, and is operable between an ON state and an OFF state based on a first control signal (CTRL1). When the first switch3operates in the ON state, the input voltage (Vin) is outputted through the first switch3to serve as the output voltage (Vout).

The converting module4is coupled between the input and output terminals1,2, and selectively converts the input voltage (Vin) into the output voltage (Vout) based on a second control signal (CTRL2). In this embodiment, the conversion performed by the converting module4is boost conversion, and the converting module4includes an inductor41, a diode42and a second switch43that are coupled to each other in a Y shape among the input and output terminals1,2and the reference node. The inductor41is coupled to the input terminal1. The diode42has a cathode coupled to the output terminal2. The second switch43is coupled to the reference node, and is operable between an ON state and an OFF state based on the second control signal (CTRL2). As a result, a magnitude of the output voltage (Vout) may be adjusted as desired by control of a duty ratio of the second control signal (CTRL2).

The control module5is coupled to the input and output terminals1,2and the first and second switches3,43, and generates the first and second control signals (CTRL1, CTRL2) based on the input and output voltages (Vin, Vout) and/or on the input current (Iin). In this embodiment, the control module5may be an MCU (micro control unit) programmed to perform operations as described hereinafter.

Under the control of the control module5, the power supply apparatus is operable in at least one of a first mode, where the first control signal (CTRL1) is such that the first switch3operates in the ON state, and where the second control signal (CTRL2) is such that the second switch43operates in the OFF state (i.e., the converting module4does not perform the conversion), and a second mode, where the first control signal (CTRL1) is such that the first switch3operates in the OFF state, and where the second control signal (CTRL2) is generated based on the output voltage (Vout) in such a way that the second switch43alternates between the ON and OFF states (i.e., the converting module4performs the conversion) and that the output voltage (Vout) is stabilized at a predetermined target voltage value (Vtarget). In this embodiment, the target voltage value (Vtarget) is greater than the minimum input voltage value (Vin_min).

As shown inFIG. 2, when the power supply apparatus operates in the second mode and a first condition associated with the input voltage (Vin) is met, the control module5generates the first control signal (CTRL1) in such a way that the first switch3operates in the OFF state, and generates the second control signal (CTRL2) in such a way that the second switch43alternates between the ON and OFF states (i.e., the converting module4performs the conversion) and that the output voltage (Vout) gradually changes (e.g., changes at a predetermined slope) toward the input voltage (Vin). In practice, the control module5may compare the output voltage (Vout) and the input voltage (Vin) so as to adjust the duty ratio of the second control signal (CTRL2), causing the output voltage (Vout) to gradually change toward the input voltage (Vin). As a result, the power supply apparatus operates neither in the first mode nor in the second mode. In this embodiment, the first condition is met when the input voltage (Vin) has been greater than a predetermined reference voltage value (Vref), which is greater than the minimum input voltage value (Vin_min) and less than the maximum input voltage value (Vin_max) and the target voltage value (Vtarget), for a predetermined delay time (Tdelay). Moreover, in this embodiment, when the power supply apparatus operates in the second mode and the first condition is met, the second control signal (CTRL2) is generated based on one of the output voltage (Vout) and the input current (Iin) in such a way that the output voltage (Vout) gradually decreases (e.g., decreases at the predetermined slope) so as to approach the input voltage (Vin). It should be noted that, in other embodiments, the first condition may be irrelevant to the delay time (Tdelay).

As shown inFIG. 2, when a difference between the input and output voltages (Vin, Vout) decreases to a predetermined gap voltage value (Vgap), the control module5generates the first and second control signals (CTRL1, CTRL2) in such a way that the power supply apparatus enters the first mode. It should be noted thatFIG. 2depicts a circumstance where the power supply apparatus has a zero processing time. In reality, the processing time of the power supply apparatus would not be zero. Therefore, when the difference between the input and output voltages (Vin, Vout) decreases to the gap voltage value (Vgap), the power supply apparatus does not enter the first mode right away; and when the power supply apparatus enters the first mode, the difference between the input and output voltages (Vin, Vout) would have decreased to be less than the gap voltage value (Vgap). In this embodiment, the gap voltage value (Vgap) is predetermined to be sufficient that the difference between the input and output voltages (Vin, Vout) is zero upon the entrance of the power supply apparatus into the first mode.

As shown inFIG. 3, when the power supply apparatus operates in the first mode and a second condition associated with the input voltage (Vin) is met, the control module5generates the first control signal (CTRL1) in such a way that the first switch3operates in the OFF state, and generates the second control signal (CTRL2) in such a way that the second switch43alternates between the ON and OFF states (i.e., the converting module4performs the conversion) and that the output voltage (Vout) gradually changes (e.g., changes at a predetermined slope) toward the target voltage value (Vtarget). In practice, the control module5may compare the output voltage (Vout) and the target voltage value (Vtarget) so as to adjust the duty ratio of the second control signal (CTRL2), causing the output voltage (Vout) to gradually change toward the target voltage value (Vtarget). In this embodiment, the second condition is met when the input voltage (Vin) is less than the reference voltage value (Vref); and when the power supply apparatus operates in the first mode and the second condition is met, the second control signal (CTRL2) is generated based on one of the output voltage (Vout) and the input current (Iin) in such a way that the output voltage (Vout) gradually increases (e.g., increases at the predetermined slope) from a predetermined minimum voltage value (Vmin), which is greater than or equal to the reference voltage value (Vref) and less than the target voltage value (Vtarget), so as to approach the target voltage value (Vtarget). It is noted that, when the minimum voltage value (Vmin) is greater than the reference voltage value (Vref), the output voltage (Vout) may directly jump from the reference voltage value (Vref) to the minimum voltage value (Vmin) within a very short time as shown inFIG. 3since the capacitor6causes the output voltage (Vout) to change continuously.

As shown inFIG. 3, when the output voltage (Vout) reaches the target voltage value (Vtarget), the control module5generates the first and second control signals (CTRL1, CTRL2) in such a way that the power supply apparatus enters the second mode.

In view of the above, the power supply apparatus of this embodiment has the following advantages:

1. With the control module5operating in the corresponding specific manner as described above when the power supply apparatus operates in the second mode and the first condition is met, the power supply apparatus draws a relatively small inrush current and thus endures relatively low current stress when switching from the second mode to the first mode.

2. With the control module5operating in the specific manner as described above when the power supply apparatus operates in the first mode and the second condition is met, the output voltage (Vout) increases relatively slowly to the target voltage value (Vtarget) and thus the power supply apparatus endures relatively low current stress when the power supply apparatus switches from the first mode to the second mode.

3. Operation of the control module5when the power supply apparatus operates in the second mode and the first condition is met, and operation of the control module5when the power supply apparatus operates in the first mode and the second condition is met causes the power supply apparatus to continuously draw energy at the input terminal1, so each of the input and output voltages (Vin, Vout) has a relatively small ripple component, and thus a system using the power supply apparatus has a relatively long lifetime and relatively good stability.

4. With the delay time (Tdelay), undesired switching of the power supply apparatus from the second mode to the first mode when the input voltage (Vin) is not stable or contains noise can be prevented.

Referring toFIGS. 4, 5 and 6, a second embodiment of a power supply apparatus according to the disclosure is a modification of the first embodiment, and differs from the first embodiment in that:

1. The conversion performed by the converting module4′ is buck conversion, and the converting module4′ includes a second switch44, an inductor45and a diode46that are coupled to each other in a Y shape among the input and output terminals1,2and the reference node. The second switch44is coupled to the input terminal1and further to the control module5′, and is operable between an ON state and an OFF state based on the second control signal (CTRL2). The inductor45is coupled to the output terminal2. The diode46has an anode coupled to the reference node.

2. The target voltage value (Vtarget) is less than the maximum input voltage value (Vin_max).

3. The first condition is met when the input voltage (Vin) has been less than the reference voltage value (Vref), which is greater than the minimum input voltage value (Vin_min) and the target voltage value (Vtarget) and less than the maximum input voltage value (Vin_max), for the predetermined delay time (Tdelay). It should be noted that, in other embodiments, the first condition may be irrelevant to the delay time (Tdelay).

4. When the power supply apparatus operates in the second mode and the first condition is met, the second control signal (CTRL2) is generated based on one of the output voltage (Vout) and the input current (Iin) in such a way that the output voltage (Vout) gradually increases (e.g., increases at a predetermined slope) so as to approach the input voltage (Vin).

5. The second condition is met when the input voltage (Vin) is greater than the reference voltage value (Vref).

6. When the power supply apparatus operates in the first mode and the second condition is met, the second control signal (CTRL2) is generated based on one of the output voltage (Vout) and the input current (Iin) in such a way that the output voltage (Vout) gradually decreases (e.g., decreases at a predetermined slope) from a predetermined maximum voltage value (Vmax), which is less than or equal to the reference voltage value (Vref) and greater than the target voltage value (Vtarget), so as to approach the target voltage value (Vtarget). It is noted that, when the maximum voltage value (Vmax) is smaller than the reference voltage value (Vref), the output voltage (Vout) may directly jump from the reference voltage value (Vref) to the maximum voltage value (Vmax) within a very short time as shown inFIG. 6since the capacitor6causes the output voltage (Vout) to change continuously.

In view of the above, the power supply apparatus of this embodiment has the following advantages:

1. With the control module5′ operating in the prescribed manner when the power supply apparatus operates in the second mode and the first condition is met, the power supply apparatus draws a relatively small inrush current and thus endures relatively low current stress when switching from the second mode to the first mode.

2. With the control module5′ operating in the manner described above when the power supply apparatus operates in the first mode and the second condition is met, the output voltage (Vout) decreases relatively slowly to the target voltage value (Vtarget) and thus the power supply apparatus endures relatively low current stress when the power supply apparatus switches from the first mode to the second mode.

3. Operation of the control module5′ when the power supply apparatus operates in the second mode and the first condition is met, and operation of the control module5′ when the power supply apparatus operates in the first mode and the second condition is met causes the power supply apparatus to continuously draw energy at the input terminal1, so each of the input and output voltages (Vin, Vout) has a relatively small ripple component, and thus a system using the power supply apparatus has a relatively long lifetime and relatively good stability.

4. With the delay time (Tdelay), undesired switching of the power supply apparatus from the second mode to the first mode when the input voltage (Vin) is not stable or contains noise can be prevented.