POWER SUPPLY APPARATUS WITH LIMITED POWER SOURCE CAPABILITY AND METHOD OF CONTROLLING THE SAME

Abstract

A power supply apparatus with limited power source capability includes a power path, a current sensing resistor, a control unit, and a switch. The power path is coupled between a transformer and an output port of the power supply apparatus. The current sensing resistor is disposed on the power path. The control unit is coupled to the current sensing resistor. The switch is disposed on the power path. When the control unit determines that a sense voltage of the current sensing resistor is less than a first threshold value and a signal voltage of the control unit is greater than a second threshold value, the control unit turns off the switch.

Claims

1. A power supply apparatus with limited power source capability, comprising: a power path coupled between a transformer and an output port of the power supply apparatus, a current sensing resistor disposed on the power path, a control unit coupled to the current sensing resistor, and a switch disposed on the power path, wherein when the control unit determines that a sense voltage of the current sensing resistor is less than a first threshold value and a signal voltage of the control unit is greater than a second threshold value, the control unit turns off the switch.

2. The power supply apparatus of claim 1, wherein when the control unit determines that the sense voltage is less than the first threshold value and the signal voltage is greater than the second threshold value for longer than a time threshold, the control unit turns off the switch.

3. The power supply apparatus of claim 1, wherein when the sense voltage is equal to 0 volt and the signal voltage is greater than the second threshold value, the control unit turns off the switch.

4. The power supply apparatus of claim 1, further comprising: a synchronous rectifying circuit coupled to the transformer and the switch, wherein the signal voltage is a node voltage of the synchronous rectifying circuit.

5. The power supply apparatus of claim 4, wherein the synchronous rectifying circuit comprises: a rectifying control unit coupled to a first end of a secondary side of the transformer and the switch, a rectifier switch coupled to the first end, the rectifying control unit, and the switch, or coupled to a second end of the secondary side and the rectifying control unit, and a capacitor coupled to the first end and the rectifying control unit.

6. The power supply apparatus of claim 5, wherein the signal voltage is a voltage of a node where the capacitor and the first end are connected.

7. The power supply apparatus of claim 5, wherein the signal voltage is a voltage of a node where the capacitor and the rectifying control unit are connected.

8. The power supply apparatus of claim 1, wherein the second threshold value is 1.1 volts.

9. The power supply apparatus of claim 2, wherein the time threshold is 500 milliseconds.

10. The power supply apparatus of claim 1, wherein the power supply apparatus has a function of a USB power delivery (USB PD).

11. A method of controlling a power supply apparatus with limited power source capability, the method comprising steps of: comparing a sense voltage of a current sensing resistor of the power supply apparatus with a first threshold value, the current sensing resistor disposed on a power path of the power supply apparatus, comparing a signal voltage provided by a synchronous rectifying circuit of the power supply apparatus with a second threshold value, and turning off a switch disposed on the power path when the sense voltage is less than the first threshold value and the signal voltage is greater than the second threshold value.

12. The method of claim 11, wherein before “turning off the switch”, the method further comprises steps of: determining whether the sense voltage is less than the first threshold value and the signal voltage is greater than the second threshold value for longer than a time threshold, and turning off the switch when the sense voltage is less than the first threshold value and the signal voltage is greater than the second threshold value for longer than the time threshold.

13. The method of claim 11, wherein the method further comprises: turning off the switch when determining that the sense voltage is equal to 0 volt and the signal voltage is greater than the second threshold value.

14. The method of claim 11, wherein the second threshold value is 1.1 volts.

15. The method of claim 12, wherein the time threshold is 500 milliseconds.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0027] The present disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows:

[0028] FIG. 1 is a circuit block diagram of an exemplary power supply apparatus with limited power source capability according to the present disclosure.

[0029] FIG. 2 is a circuit diagram of the exemplary power supply apparatus with limited power source capability according to the present disclosure.

[0030] FIG. 3 is a flowchart of an exemplary method of controlling a power supply apparatus with limited power source capability according to a first embodiment of the present disclosure.

[0031] FIG. 4 is a flowchart of an exemplary method of controlling a power supply apparatus with limited power source capability according to a second embodiment of the present disclosure.

DETAILED DESCRIPTION

[0032] Reference will now be made to the drawing figures to describe the present disclosure in detail. It will be understood that the drawing figures and exemplified embodiments of present disclosure are not limited to the details thereof.

[0033] FIG. 1 illustrates a circuit block diagram of a power supply apparatus with limited power source capability according to the present disclosure. The power supply apparatus with limited power source capability (hereinafter “power supply apparatus”) includes a power path P.sub.O, a current sensing resistor R.sub.CS, a control unit CON.sub.PD, and a switch Q.sub.P. The power path P.sub.O is coupled between a transformer T.sub.R and an output port S.sub.O of the power supply apparatus. As shown in FIG. 1, the power path P.sub.O is a path for delivering power from the secondary side of the transformer T.sub.R to the output port S.sub.O of the power supply apparatus. In the present disclosure, the power supply apparatus has a function of USB power delivery (USB PD). Therefore, the control unit CON.sub.PD is a USB PD (power delivery) controller, and the communication, feedback control, protection control, and/or other functions can be performed by the control unit CON.sub.PD.

[0034] The current sensing resistor R.sub.CS is disposed on the power path P.sub.O. The control unit CON.sub.PD is coupled to the current sensing resistor R.sub.CS. The switch Q.sub.P is disposed on the power path P.sub.O to provide a protection function by turning off the switch Q.sub.P. By turning on or turning off the switch Q.sub.P, the power supply apparatus can output power or not. That is, when the switch Q.sub.P is turned on, the power supply apparatus outputs power through the power path P.sub.O to the output port S.sub.O; when the switch Q.sub.P is turned off, the power supply apparatus does not output power.

[0035] Specifically, when the control unit CON.sub.PD determines that a sense voltage V.sub.RCS of the current sensing resistor R.sub.CS is less than a first threshold value V.sub.TH1 and a signal voltage V.sub.IC1 of the control unit CON.sub.PD is greater than a second threshold value V.sub.TH2, the control unit CON.sub.PD turns off the switch Q.sub.P so that no power will be outputted from the power supply apparatus. The second threshold value V.sub.TH2 is, for example but not limited to, 1.1 volts. The sense voltage V.sub.RCS is generated when a current flows through the current sensing resistor R.sub.CS, so the sense voltage V.sub.RCS indicates the magnitude of the current flowing through the current sensing resistor R.sub.CS if the resistance of the current sensing resistor R.sub.CS is fixed. That is, the greater the sense voltage V.sub.RCS, the greater the current flowing through the current sensing resistor R.sub.CS; the smaller the sense voltage V.sub.RCS, the smaller the current flowing through the current sensing resistor R.sub.CS. Therefore, if the sense voltage V.sub.RCS is less than the first threshold value V.sub.TH1, it may mean that the power supply apparatus does not output power at the moment, or circuits related to the current sensing resistor R.sub.CS are abnormal, for example, a short-circuit condition occurs on the current sensing resistor R.sub.CS, or the power supply apparatus is in a short-circuit protection test or an LPS test.

[0036] Moreover, the magnitude of the signal voltage V.sub.IC1 is related to the output power (output load) of the power supply apparatus, so the greater the signal voltage V.sub.IC1, the greater the output power of the power supply apparatus; the smaller the signal voltage V.sub.IC1, the smaller the output power of the power supply apparatus. The control unit CON.sub.PD simultaneously determines whether the sense voltage V.sub.RCS of the current sensing resistor R.sub.CS is less than the first threshold value V.sub.TH1 and the signal voltage V.sub.IC1 is greater than the second threshold value V.sub.TH2, and if both conditions are met, the control unit CON.sub.PD determines that the current sensing resistor R.sub.CS of the power supply apparatus may be short-circuited but the power supply apparatus still continuously outputs current to the load. In other words, the power supply apparatus may be in the short-circuit protection test or the LPS test, and therefore the control unit CON.sub.PD immediately turns off the switch Q.sub.P so that no power will be outputted from the power supply apparatus.

[0037] In another embodiment, one condition that the control unit CON.sub.PD determines that the sense voltage V.sub.RCS is less than the first threshold value V.sub.TH1 may be a condition that the sense voltage V.sub.RCS is equal to 0 volt. Therefore, when the sense voltage V.sub.RCS is equal to 0 volt and the signal voltage V.sub.IC1 is greater than the second threshold value V.sub.TH2, the control unit CON.sub.PD turns off the switch Q.sub.P so that no power will be outputted from the power supply apparatus.

[0038] Another embodiment of the present disclosure includes that the control unit CON.sub.PD further determines a time condition. Specifically, when the control unit CON.sub.PD determines that the sense voltage V.sub.RCS is less than the first threshold value V.sub.TH1 and the signal voltage V.sub.IC1 is greater than the second threshold value V.sub.TH2 for longer than a time threshold T.sub.TH, the control unit CON.sub.PD turns off the switch Q.sub.P so that no power will be outputted from the power supply apparatus. In one embodiment, the time threshold T.sub.TH is, for example but not limited to, 500 milliseconds. Therefore, the time condition is introduced to avoid false triggering of the protection mechanism of turning off the switch Q.sub.P if both the voltage conditions are met due to transient abnormal (unexpected) circuit operations.

[0039] As shown in FIG. 1, the power supply apparatus further includes a synchronous rectifying circuit SR. The synchronous rectifying circuit SR is coupled to the transformer T.sub.R and the switch Q.sub.P. The signal voltage V.sub.IC1 is a node voltage of the synchronous rectifying circuit SR.

[0040] FIG. 2 illustrates a circuit diagram of the exemplary power supply apparatus with limited power source capability according to the present disclosure. The synchronous rectifying circuit SR includes a rectifying control unit, a rectifier switch, and a capacitor. The synchronous rectifying circuit SR is provided to convert an AC voltage into a DC voltage for the output of the power supply apparatus. The rectifying control unit CON.sub.SR is coupled to a non-grounding end of the secondary side of the transformer T.sub.R and the switch Q.sub.P. The rectifier switch Q.sub.SR is coupled to the non-grounding end, the rectifying control unit CON.sub.SR, and the switch Q.sub.P. The capacitor C.sub.SR is coupled to the non-grounding end and the rectifying control unit CON.sub.SR.

[0041] In one embodiment, the signal voltage V.sub.IC1 is a voltage of a node where the switch Q.sub.SR, the capacitor C.sub.SR, and the non-grounding end are commonly connected, i.e., a node voltage of a first node P1 shown in FIG. 2. Therefore, when the control unit CON.sub.PD determines that the sense voltage V.sub.RCS is less than the first threshold value V.sub.TH1 and the signal voltage V.sub.IC1 (i.e., the node voltage of the first node P1) is greater than the second threshold value V.sub.TH2, the control unit CON.sub.PD turns off the switch Q.sub.P so that no power will be outputted from the power supply apparatus. Specifically, the node voltage of the first node P1 is adjusted to a voltage level suitable for the operation of the control unit CON.sub.PD by an adjustment circuit 10 with rectification and voltage division functions. Therefore, the adjusted voltage level is provided to the control unit CON.sub.PD, such as a first pin of the control unit CON.sub.PD shown in FIG. 1.

[0042] In one embodiment, the signal voltage V.sub.IC1 is a voltage of a node where the capacitor C.sub.SR and the rectifying control unit CON.sub.SR are connected, i.e., a node voltage of a second node P2 shown in FIG. 2. Therefore, when the control unit CON.sub.PD determines that the sense voltage V.sub.RCS is less than the first threshold value V.sub.TH1 and the signal voltage V.sub.IC1 (i.e., the node voltage of the second node P2) is greater than the second threshold value V.sub.TH2, the control unit CON.sub.PD turns off the switch Q.sub.P so that no power will be outputted from the power supply apparatus. Specifically, the node voltage of the second node P2 is adjusted to a voltage level suitable for the operation of the control unit CON.sub.PD by an adjustment circuit 10 with rectification and voltage division functions. Therefore, the adjusted voltage level is provided to the control unit CON.sub.PD, such as a first pin of the control unit CON.sub.PD shown in FIG. 1.

[0043] However, it is not limited to detecting the node voltage of the first node P1 or the second node P2 for the control unit CON.sub.PD to determine if the signal voltage V.sub.IC1 is less than the first threshold value V.sub.TH1. A node voltage of any node in the synchronous rectifying circuit SR that varies with the output current can be used.

[0044] In particular, the rectifier switch Q.sub.SR of the synchronous rectifying circuit SR is not limited to be arranged at the high side of the secondary side circuit, i.e., a current output side of the secondary side circuit shown in FIG. 2, that is, the rectifier switch Q.sub.SR may be arranged at the low side, i.e., a current return side. Therefore, whether the switch Q.sub.SR is arranged at the high side or the low side, it is suitable for the abovementioned controls of the power supply apparatus with limited power source capability.

[0045] FIG. 3 illustrates a flowchart of an exemplary method of controlling a power supply apparatus with limited power source capability according to a first embodiment of the present disclosure. A power path P.sub.O between an output port S.sub.O of the power supply apparatus and a transformer is provided. The power supply apparatus includes a current sensing resistor R.sub.CS, a control unit CON.sub.PD, and a switch Q.sub.P. The method includes the following steps. First, under a normal load operation (S11), comparing a sense voltage V.sub.RCS of the current sensing resistor R.sub.CS with a first threshold value V.sub.TH1 (S12). Afterward, comparing a signal voltage Vici of the control unit CON.sub.PD with a second threshold value V.sub.TH2 (S13). Afterward, determining whether the sense voltage V.sub.RCS is less than the first threshold value V.sub.TH1 and the signal voltage V.sub.IC1 is greater than the second threshold value V.sub.TH2 (S14). Finally, turning off the switch Q.sub.P (S15) when the sense voltage V.sub.RCS is less than the first threshold value V.sub.TH1 and the signal voltage V.sub.IC1 is greater than the second threshold value V.sub.TH2.

[0046] In another embodiment, one condition that determining that the sense voltage V.sub.RCS is less than the first threshold value V.sub.TH1 may be a condition that the sense voltage V.sub.RCS is equal to 0 volt. Therefore, turning off the switch Q.sub.P (S15) when the sense voltage V.sub.RCS is equal to 0 volt and the signal voltage V.sub.IC1 is greater than the second threshold value V.sub.TH2 so that no power will be outputted from the power supply apparatus.

[0047] FIG. 4 illustrates a flowchart of another exemplary method of controlling a power supply apparatus with limited power source capability according to a second embodiment of the present disclosure. The major difference between the FIG. 4 and the FIG. 3 is that the former further includes determining a time condition after the step (S14), that is, determining whether the sense voltage V.sub.RCS is less than the first threshold value V.sub.TH1 and the signal voltage V.sub.IC1 is greater than the second threshold value V.sub.TH2 for longer than a time threshold T.sub.TH (S14′). If both the voltage conditions are met, that is, the result in the step (S14) is “YES” and the time condition is met, that is, the result in the step (S14′) is “YES”, the switch Q.sub.P is turned off (S15) so that no power will be outputted from the power supply apparatus. On the contrary, if one of the both voltage conditions is not met, that is, the result in the step (S14) is “NO”, or the time condition is not met, that is, the result in the step (S14′) is “NO”, the step (S12) and the step (S13) are performed again.

[0048] Accordingly, the present disclosure provides the power supply apparatus with limited power source capability and the method of controlling the same to achieve precise overcurrent or overpower protections for the power supply apparatuses with larger output power by acquiring and determining node voltages related to the output power (output load) of the power supply apparatus, and controlling the power supply apparatus with simple circuit design to meet the LPS standards.

[0049] Although the present disclosure has been described with reference to the preferred embodiment thereof, it will be understood that the present disclosure is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the present disclosure as defined in the appended claims.