Conversion circuit

The present disclosure provides a conversion circuit including a power supply module, positive and negative input terminals, positive and negative output terminals, a switch, an inductor, input and output capacitors, and a controller. The power supply module converts an AC power for providing three potentials on three power supply terminals respectively. The potential on the first power supply terminal is higher than the potential on the second power supply terminal, which is higher than the potential on the third power supply terminal. The positive and negative input terminals are electrically connected to the first and third power supply terminals respectively, and a voltage therebetween is an input voltage. The negative output terminal is electrically connected to the third power supply terminal. The controller is electrically connected to the positive input terminal, the second power supply terminal and the switch. A voltage across the controller is lower than the input voltage.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to China Patent Application No. 202210066970.6, filed on Jan. 20, 2022, the entire contents of which are incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The present disclosure relates to a conversion circuit, and more particularly to a conversion circuit with the ranges of the input and output voltages not limited by the withstand voltage of the controller.

BACKGROUND OF THE INVENTION

In the circuit structure of the conventional buck converter, since the controller (control IC) needs power for driving, the input voltage of the buck converter is directly connected to the controller for providing the power needed by the controller. Therefore, the voltage across the controller is equal to the input voltage. Due to the certain withstand voltage range of the controller, the range of the input voltage would be limited by the withstand voltage of the controller actually, which causes the range of the output voltage also be limited.

Therefore, there is a need of providing a conversion circuit to obviate the drawbacks encountered from the prior arts.

SUMMARY OF THE INVENTION

It is an objective of the present disclosure to provide a conversion circuit which separates the low-potential terminal of the input and output voltages from the low-potential terminal of the controller, thereby making the input and output voltage independent from the voltage across the controller. Consequently, the ranges of the input and output voltages are greatly improved with taking the withstand voltage of the controller into consideration, thereby enhancing the applicability of the conversion circuit.

In accordance with an aspect of the present disclosure, there is provided a conversion circuit including a power supply module, a positive input terminal, a negative input terminal, a positive output terminal, a negative output terminal, a first switch, a first inductor, an input capacitor, an output capacitor, and a controller. The power supply module has a first power supply terminal, a second power supply terminal, and a third power supply terminal, and is configured to receive and convert an AC power for providing three potentials on the first, second and third power supply terminals respectively. The potential on the first power supply terminal is higher than the potential on the second power supply terminal, and the potential on the second power supply terminal is higher than the potential on the third power supply terminal. The positive input terminal and the negative input terminal are electrically connected to the first power supply terminal and the third power supply terminal respectively. A voltage between the positive input terminal and the negative input terminal is an input voltage. The negative output terminal is electrically connected to the third power supply terminal, and a voltage between the positive output terminal and the negative output terminal is an output voltage. The first switch and the first inductor are coupled in series between the positive input terminal and the positive output terminal. The input capacitor is coupled between the positive input terminal and the negative input terminal. The output capacitor is coupled between the positive output terminal and the negative output terminal. The controller has an input terminal electrically connected to the positive input terminal, a ground terminal electrically connected to the second power supply terminal, and a control terminal electrically connected to the first switch. A voltage across the controller is lower than the input voltage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG.1is a schematic circuit diagram illustrating a conversion circuit according to an embodiment of the present disclosure. As shown inFIG.1, the conversion circuit1includes a power supply module11, a positive input terminal12a, a negative input terminal12b, a positive output terminal13a, a negative output terminal13b, a switch S1, an inductor L1, an input capacitor Cin, an output capacitor Co, and a controller14. The power supply module11has a first power supply terminal P1, a second power supply terminal P2, and a third power supply terminal P3. The power supply module11is configured to receive and convert an AC power VAC for providing three potentials on the first power supply terminal P1, the second power supply terminal P2, and the third power supply terminal P3respectively. The potential on the first power supply terminal P1is higher than the potential on the second power supply terminal P2, and the potential on the second power supply terminal P2is higher than the potential on the third power supply terminal P3. In other words, the first power supply terminal P1and the second power supply terminal P2form a first DC voltage, and the second power supply terminal P2and the third power supply terminal P3form a second DC voltage. The positive input terminal12aand the negative input terminal12bare electrically connected to the first power supply terminal P1and the third power supply terminal P3respectively. The voltage between the positive input terminal12aand the negative input terminal12bis an input voltage Vin which equals the sum of the first and second DC voltages. The negative output terminal13bis electrically connected to the third power supply terminal P3, and the voltage between the positive output terminal13aand the negative output terminal13bis an output voltage Vo. The switch S1and the inductor L1are coupled in series between the positive input terminal12aand the positive output terminal13a. The input capacitor Cin is coupled between the positive input terminal12aand the negative input terminal12b, and the output capacitor Co is coupled between the positive output terminal13aand the negative output terminal13b. The controller14has an input terminal electrically connected to the positive input terminal12a, a ground terminal electrically connected to the second power supply terminal P2, and a control terminal electrically connected to the switch S1. The controller14is configured to control the operation of the switch S1, and the controller14is for example but not limited to a control IC (integrated circuit). Since the potential on the second power supply terminal P2is higher than the potential on the third power supply terminal P3, the voltage between the first power supply terminal P1and the second power supply terminal P2(i.e., the first DC voltage) is lower than the voltage between the first power supply terminal P1and the third power supply terminal P3. Namely, the voltage received by the controller14is lower than the input voltage Vin. The positive output terminal13aand the negative output terminal13bof the conversion circuit1are utilized to supply power to a load15. The load15may be any load requiring constant-current or constant-voltage control. In other words, the current or voltage on the load15is constant.

From the above descriptions, the conversion circuit1of the present disclosure separates the low-potential terminal of the input voltage Vin and the output voltage Vo (i.e., the third power supply terminal P3) from the low-potential terminal of the controller14(i.e., the second power supply terminal P2), thereby making the input voltage Vin and the output voltage Vo independent from the voltage across the controller14. Consequently, the ranges of the input voltage Vin and the output voltage Vo are greatly improved with taking the withstand voltage of the controller14into consideration, thereby enhancing the applicability of the conversion circuit1. In addition, since the output range increases, the range of the load that can be driven becomes larger. Therefore, the number of the conversion circuits is reduced, the control complexity is reduced, and the cost for the components required for control is reduced.

In an embodiment, the conversion circuit1further includes a diode D1. The cathode of the diode D1is coupled between the switch S1and the inductor L1, and the anode of the diode D1is coupled to the negative output terminal13b. The conversion circuit1in this embodiment may include a buck converter. In an embodiment, the switch S1is a PMOS (P-type metal-oxide-semiconductor field-effect transistor), and the source, gate and drain of the switch S1are coupled to the positive input terminal12a, the control terminal of the controller14, and the inductor L1respectively. It is noted that the potential on the cathode of the diode D1in the buck converter is variable. If the switch S1is NMOS, a complicated driver is required. Therefore, in this embodiment, the switch S1is implemented by PMOS to simplify the driver, and the switch S1is turned on and off through controlling the voltage level between the source and gate of the switch S1.

In the present disclosure, the power supply module11is configured to receive and convert the AC power VAC for providing three potentials on the first power supply terminal P1, the second power supply terminal P2, and the third power supply terminal P3respectively. The main purpose of the power supply module11is to generate the terminals with three different potentials. The power supply module11has various kinds of possible implementations. Three implementations of the power supply module11are exemplified as follows, but the power supply module11is not limited thereto.

In an embodiment, as shown inFIG.2, the power supply module11ais a two-stage converter including an AC-DC converter111and a DC-DC converter112. The AC-DC converter111receives the AC power VAC and converts the AC power VAC into a DC power. The AC-DC converter111may be any known power conversion circuit. In the application with high power, the AC-DC converter111may be a power factor correction circuit. The DC-DC converter112is electrically connected to the AC-DC converter111, the first power supply terminal P1, the second power supply terminal P2, and the third power supply terminal P3. The DC-DC converter112receives the DC power from the AC-DC converter111and provides three potentials to the first power supply terminal P1, the second power supply terminal P2, and the third power supply terminal P3through converting the DC power.

In an embodiment, the DC-DC converter112may adopt an isolated converter (e.g., LLC resonant converter) or a non-isolated converter.FIG.3schematically shows an implementation of the DC-DC converter ofFIG.2. As shown inFIG.3, in this embodiment, the DC-DC converter112includes an inductor L2, a switch S2, a switch S3, a diode D2, a diode D3, a capacitor C1, and a capacitor C2. The first terminal of the inductor L2is electrically connected to the AC-DC converter111. The anode and cathode of the diode D2are electrically connected to the second terminal of the inductor L2and the first power supply terminal P1respectively. The cathode and anode of the diode D3are electrically connected to the AC-DC converter111and the third power supply terminal P3respectively. The switches S2and S3are connected in series between the anode of diode D2and the cathode of diode D3. The capacitors C1and C2are connected in series between the cathode of diode D2and the anode of diode D3. The node between the switches S2and S3and the node between the capacitors C1and C2are both electrically connected to the second power supply terminal P2. In this embodiment, the DC-DC converter112is a conversion circuit with positive and negative bus outputs. If the second power supply terminal P2is regarded as a reference terminal, the first power supply terminal P1has a positive potential, and the third power supply terminal P3has a negative potential.

In an embodiment, as shown inFIG.4, a part of the power supply module11bincludes a center-tapped transformer113and a rectifier circuit116. The center-tapped transformer113includes a primary winding114and a secondary winding115coupled to each other. The primary winding114is utilized to receive an AC signal AC. The secondary winding115has a first secondary terminal115a, a second secondary terminal115b, and a third secondary terminal115c. The rectifier circuit116is electrically connected to the first secondary terminal115a, the second secondary terminal115b, the third secondary terminal115c, the first power supply terminal P1, the second power supply terminal P2, and the third power supply terminal P3. The rectifier circuit116receives the AC signal transmitted by the transformer through the secondary winding115, and rectifies the received AC signal. Thereby, the rectifier circuit116provides a first DC voltage between the first power supply terminal P1and the second power supply terminal P2and provides a second DC voltage between the second power supply terminal P2and the third power supply terminal P3. It is noted thatFIG.4shows only a part of the power supply module11b, the primary winding114may be coupled to at least one changeover switch (not shown), and the primary winding114is allowed to receive the AC signal AC through turning on or off the at least one changeover switch. In other words, the circuit shown inFIG.4may replace the secondary-side circuit of the conventional isolated converter to provide three power supply terminals.

FIG.5schematically shows an implementation of the center-tapped transformer and the rectifier circuit ofFIG.4. The circuit in this embodiment is utilized to replace the secondary-side circuit of the conventional flyback converter. In this embodiment, the rectifier circuit116includes a diode D4, a diode D5, a capacitor C3, and a capacitor C4. The anode and cathode of the diode D4are electrically connected to the first secondary terminal115aand the first power supply terminal P1respectively. The cathode and anode of the diode D5are electrically connected to the third secondary terminal115cand the third power supply terminal P3respectively. The capacitors C3and C4are connected in series between the cathode of diode D4and the anode of diode D5. The node between the capacitors C3and C4is electrically connected to the second secondary terminal115band the second power supply terminal P2.

In an embodiment, as shown inFIG.6, the power supply module11cincludes a first converter117and a second converter118. The first converter117and the second converter118are configured to receive the AC power VAC, and provide three potentials to the first, second and third power supply terminals through converting the AC power VAC. In specific, the first and second converters117and118may be implemented by conventional power conversion circuits, and the output voltages thereof are serially connected to form the first power supply terminal P1, the second power supply terminal P2, and the third power supply terminal P3. The first output terminal117aof the first converter117is electrically connected to the first power supply terminal P1. The second output terminal117bof the first converter117and the first output terminal118aof the second converter118are electrically connected to the second power supply terminal P2. The second output terminal118bof the second converter118is electrically connected to the third power supply terminal P3. In other words, the first converter117receives and converts the AC power VAC to provide a first DC voltage between the first power supply terminal P1and the second power supply terminal P2, and the second converter118receives and converts the AC power VAC to provide a second DC voltage between the second power supply terminal P2and the third power supply terminal P3. The output of the power supply module11cis formed by the first DC voltage and the second DC voltage connected in series.

In conclusion, the present disclosure provides a conversion circuit which separates the low-potential terminal of the input and output voltages from the low-potential terminal of the controller, thereby making the input and output voltage independent from the voltage across the controller. Consequently, the ranges of the input and output voltages are greatly improved with taking the withstand voltage of the controller into consideration, thereby enhancing the applicability of the conversion circuit. In addition, since the output range increases, the range of the load that can be driven becomes larger. Therefore, the number of the conversion circuits is reduced, the control complexity is reduced, and the cost for the components required for control is reduced.

While the disclosure has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the disclosure needs not be limited to the disclosed embodiment.