Optical-control driving circuit for high utility power

1. Field of the Invention

The present disclosure relates to an optical-controlled driving circuit for high utility power; in particular, to an optical-controlled driving circuit that adapts to environments with high utility power where high voltages, large currents and severe surges are concerned.

2. Description of Related Art

Usually, an SCR (Silicon-Controlled Rectifier; SCR) can be used as a switch to control utility power. However, while the reference point of a control signal from a system terminal is common-grounded, the reference point of the thyristors of the SCR is not. Therefore, an SCR driving circuit needs to be isolated, and this is often implemented by transformer isolation or optical-controlled isolation. The transformer isolation may have high driving loss and poor pulse driving performance. Particularly, the pulse driving makes the resistance between the cathode and the anode of the SCR varies like a pulse wave. In this case, under a working condition with a large utility current, the SCR will be damaged due to its resistance variation, which decreases the operation efficiency of the SCR driving circuit.

Considering the high operation efficiency required of SCR driving circuits, the optical-controlled isolation becomes another option. However, the maximum voltage drop of a thyristor is usually 800V due to restrictions of power density and packaging of power source elements, thus limiting the high-voltage tolerance and the reaction to severe surges of a thyristor. Accordingly, there is a need in the art for a new SCR driving circuit that can adjust its driving current according to the voltage of a utility power and that can adapt to environments with high utility power where high voltages, large currents and severe surges are concerned.

To solve the above problems (e.g., high driving loss cause due to the transformer isolation, or damage to the SCR due to discontinuous driving currents), the present disclosure provides an optical-controlled driving circuit that adapts to a high utility power environment with high voltages, large currents and severe surges, and has advantages such as a high operation efficiency and a quick and dynamic response.

The optical-controlled driving circuit in the present disclosure can work under a high utility power environment with high voltages, large currents and surges, and includes an optical-controlled switch circuit, a SCR with optical-controlled driver and a main circuit. The optical-controlled switch circuit includes an optical-controlled component and a first switching transistor, and receives a switch signal. The optical-controlled component and the first switching transistor are connected in serial, and the optical-controlled component has at least four terminals. The SCR with optical-controlled driver receives a utility power, and is coupled to the optical-controlled switch circuit. The SCR with optical-controlled driver includes a second switching element, a third switching element, a first diode, a second diode, a third diode and a fourth diode. A cathode of the third switching element is coupled to an anode of the second switching element, and receives the utility power. A cathode of the first diode is coupled to a gate of the second switching element, and an anode of the first diode is coupled to a third terminal of the optical-controlled component. A cathode of the second diode is coupled to a gate of the third switching element, and an anode of the second diode is coupled to the anode of the first diode. A cathode of the third diode is coupled to the anode of the second switching element, and an anode of the third diode is coupled to a fourth terminal of the optical-controlled component. A cathode of the fourth diode is coupled to an anode of the third switching element, and an anode of the fourth diode is coupled to the anode of the third diode. The main circuit is coupled to the SCR with optical-controlled driver, and has an A terminal, a B terminal and a ground terminal. The A terminal of the main circuit is coupled to the cathode of the second switching element, and the B terminal is coupled to the anode of the third switching element.

For further understanding of the present disclosure, reference is made to the following detailed description illustrating the embodiments of the present disclosure. The description is only for illustrating the present disclosure, not for limiting the scope of the claim.

Embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which:

FIG. 1 shows a block diagram of an SCR with an optical-controlled driving circuit according to one embodiment of the present disclosure;

FIG. 2 shows a circuit diagram of an SCR with an optical-controlled driving circuit according to one embodiment of the present disclosure;

FIG. 3 is a circuit diagram showing the optical-controlled driving circuit in FIG. 2 works under a positive half cycle of the utility power; and

FIG. 4 is a circuit diagram showing the optical-controlled driving circuit in FIG. 2 works under a negative half cycle of the utility power.

The aforementioned illustrations and following detailed descriptions are exemplary for the purpose of further explaining the scope of the present disclosure. Other objectives and advantages related to the present disclosure will be illustrated in the subsequent descriptions and appended drawings. In these drawings, like references indicate similar elements.

In the following descriptions, terms refers to switches include switch elements, but in practice the switch elements are not restricted by IGBT, BJT, MOS, CMOS, JFET or MOSFET. Also, terms, including “first”, “second”, “third”, “first switch transistor”, “fourth switching transistor”, “first capacitor”, “second capacitor”, “first diode”, “second diode” . . . , are for distinguishing one element from another element without a specific sequence. Therefore, in one embodiment, there may be a first switching transistor and a fourth switching transistor but no second switching transistor.

Terms “first end” and “second end”, “upper end” or “lower end”, “right end” and “left end”, “primary end” and “secondary end” or the like are for distinguishing one end from another end, one end of an element from another end of the same element, or one element from another element, but not indicate any sequence or element positions. Also, terms “and/or” include any and all combinations of one or more of the associated listed items.

To improve the disadvantages of a conventional SCR (Silicon-Controlled Rectifier; SCR) driving circuit (e.g., high driving loss due to transformer isolation, or damage to the SCR due to discontinuous driving currents), the present disclosure provides an optical-controlled driving circuit that adapts to a high utility power environment with high voltages, large currents and severe surges, and has advantages such as a high operation efficiency and a quick and dynamic response.

The optical-controlled driving circuit shown in FIG. 1 includes an optical-controlled switch circuit 10 , an SCR with optical-controlled driver 20 and a main circuit 30 . The main circuit 30 can be a converter. The optical-controlled switch circuit 10 receives a switch signal SCRIO, and the turning on and off of the optical-controlled switch circuit 10 is controlled by the switch signal SCRIO. The SCR with optical-controlled driver 20 receives a utility power, is coupled to the optical-controlled switch circuit 10 , and works according to the on and off of the optical-controlled switch circuit 10 . The main circuit 30 is coupled to the SCR with optical-controlled driver 20 , and the SCR with optical-controlled driver 20 controls the main circuit 30 .

As shown in FIG. 2 , the optical-controlled switch circuit 10 includes an optical-controlled component 12 and a first switching transistor Q 1 . The optical-controlled component 12 and the first switching transistor Q 1 are connected in serial. The optical-controlled component 12 at least has four terminals and includes at least two optical-controlled thyristors, such as the first optical-controlled thyristor U 1 and the second optical-controlled thyristor U 2 which are connected in serial. The first terminal of the optical-controlled component 12 receives a direct power VCC. The drain of the first switching transistor Q 1 is coupled to the second terminal of the optical-controlled component 12 , the source of the first switching transistor Q 1 is grounded, and the gate of the first switching transistor Q 1 receives the switch signal SCRIO.

It should be noted that, both of the first optical-controlled thyristor U 1 and the second optical-controlled thyristor U 2 have four ends. As shown in FIG. 2 , the first end of the first optical-controlled thyristor U 1 is the first terminal of the optical-controlled component 12 . The second end of the second optical-controlled thyristor U 2 is the second terminal of the optical-controlled component 12 . The third end of the first optical-controlled thyristor U 1 is the third terminal of the optical-controlled component 12 . The fourth end of the optical-controlled thyristor U 2 is the fourth terminal of the optical-controlled component 12 . The first end of the first optical-controlled thyristor U 1 receives the direct power VCC, and the third end of the first optical-controlled thyristor U 1 is coupled to the SCR with optical-controlled driver 20 . The first end of the second optical-controlled thyristor U 2 is coupled to the second end of the first optical-controlled thyristor U 1 , and the second end of the second optical-controlled thyristor U 2 is coupled to the drain of the first switching transistor Q 1 . The third end of the second optical-controlled thyristor U 2 is coupled to the fourth end of the first optical-controlled thyristor U 1 , and the fourth end of the second optical-controlled thyristor U 2 is coupled to the SCR with optical-controlled driver 20 .

In one embodiment, the optical-controlled switch circuit 10 further includes a voltage regulating element ZD 1 , a first capacitor C 1 , a first resistor R 1 and a second resistor R 2 . The cathode of the voltage regulating element ZD 1 receives the switch signal SCRIO, and the anode of the voltage regulating element ZD 1 is coupled to the gate of the first switching transistor Q 1 . The first capacitor C 1 and the second resistor R 2 are connected in parallel. The first end of the first capacitor C 1 (the upper end of the first capacitor C 1 in FIG. 2 ) is also coupled to the gate of the first switching transistor Q 1 , and the second end of the first capacitor C 1 (the lower end of the first capacitor C 1 in FIG. 2 ) is coupled to the source of the first switching transistor Q 1 . Due to the connection relationships among the voltage regulating element ZD 1 , the first capacitor C 1 and the second resistor R 2 , the switch signal SCRIO can be transmitted to the first switching transistor Q 1 . One end of the first resistor R 1 receives the direct power VCC, and the other end of the first resistor R 1 is coupled to the first terminal of the optical-controlled component 12 (i.e. the first end of the first optical-controlled thyristor U 1 ). The first resistor R 1 is a current limiting resistor.

In practice, the direct power VCC is from 10V to 20V. The switch signal SCRIO, which is a pulse signal (that may be at high level or low level), controls the optical-controlled component 12 . The optical-controlled switch circuit 10 shown in FIG. 10 is a circuit that controls the SCR in an optical manner; however, how the switch circuit controls the SCR in the present disclosure is not restricted.

The SCR with optical-controlled driver 20 in FIG. 2 receives a utility power, and includes a second switching transistor Q 2 , a third switching element Q 3 , a first diode D 1 , a second diode D 2 , a third diode D 3 and a fourth diode D 4 . The cathode of the second switching transistor Q 2 is coupled to the first end of the main circuit 30 (the upper end of the main circuit 30 in FIG. 2 ), and the cathode of the third switching transistor Q 3 is coupled to the anode of the second switching transistor Q 2 and receives the utility power. The cathode of the first diode D 1 is coupled to the gate of the second switching transistor Q 2 , and the anode of the first diode D 1 is coupled to the third terminal of the optical-controlled component 12 . The cathode of the second diode D 2 is coupled to the gate of the third switching element Q 3 , and the anode of the second diode D 2 is coupled to the anode of the first diode D 1 . The cathode of the third diode D 3 is coupled to the anode of the second switching transistor Q 3 , which indicates that the third diode D 3 receives the utility power, and the anode of the diode D 3 is coupled to the fourth terminal of the optical-controlled component 12 . The cathode of the fourth diode D 4 is coupled to the anode of the third switching element Q 3 and is coupled to the second end of the main circuit 30 (the lower end of the main circuit 30 in FIG. 2 ), and the anode of the fourth diode D 4 is coupled to the anode of the third diode D 3 .

In one embodiment, the SCR with optical-controlled driver 20 further includes a second capacitor C 2 , a third capacitor C 3 , a seventh resistor R 7 and an eighth resistor R 8 . The second capacitor C 2 and the seventh resistor R 7 are connected in parallel. A first end of the second capacitor C 2 (i.e. the upper end of the second capacitor C 2 shown in FIG. 2 ) is coupled to the cathode of the second switching element Q 2 , and a second end of the second capacitor C 2 (i.e. the lower end of the second capacitor C 2 shown in FIG. 2 ) is coupled to the gate of the second switching element Q 2 . The third capacitor C 3 and the eighth resistor R 8 are connected in parallel. A first end of the third capacitor C 3 (i.e. the upper end of the third capacitor C 3 shown in FIG. 2 ) is coupled to the cathode of the third switching element Q 3 , and a second end of the third capacitor C 3 (i.e. the lower end of the third capacitor C 3 shown in FIG. 2 ) is coupled to the gate of the third switching element Q 3 .

In other embodiments, the SCR with optical-controlled driver may include a third equalizing resistor R 3 , a fourth equalizing resistor R 4 , a fifth resistor R 5 and a sixth resistor R 6 . A first end of the third equalizing resistor R 3 (i.e. the upper end of the third equalizing resistor R 3 shown in FIG. 2 ) is coupled to the third terminal of the optical-controlled component 12 , and a second end of the third equalizing resistor R 3 (i.e. the lower end of the third equalizing resistor R 3 shown in FIG. 2 ) is coupled to a first end of the fourth equalizing resistor R 4 and a fifth terminal of the optical-controlled component 12 . The fifth terminal of the optical-controlled component 12 is a node between the fourth end of the first optical-controlled thyristor U 1 and the third end of the second optical-controlled thyristor U 2 . A second end of the fourth equalizing resistor R 4 (i.e. the lower end of the fourth equalizing resistor R 4 shown in FIG. 2 ) is coupled to the fourth terminal of the optical-controlled component 12 . A first end of the fifth resistor R 5 (i.e. the left end of the fifth resistor R 5 shown in FIG. 2 ) is coupled to the gate of the second switching transistor Q 2 , and a second end of the fifth resistor R 5 (i.e. the right end of the fifth resistor R 5 shown in FIG. 2 ) is coupled to the cathode of the first diode D 1 . A first end of the sixth resistor R 6 (i.e. the left end of the sixth resistor R 6 shown in FIG. 2 ) is coupled to the gate of the third switching element Q 3 , and a second end of the sixth resistor R 6 (i.e. the right end of the sixth resistor R 6 shown in FIG. 2 ) is coupled to the cathode of the second diode D 2 .

It should be noted that, in the above descriptions, the first diode D 1 , the second diode D 2 , the third diode D 3 and the fourth diode D 4 are rectifier diodes. The fifth resistor R 5 , the seventh resistor R 7 and the second capacitor C 2 are taken as a driving circuit of the second switching transistor Q 2 , and the sixth resistor R 6 , the eighth resistor R 8 and the third capacitor R 3 are taken as a driving circuit of the third switching element Q 3 . The optical-controlled component 12 can be implemented by one optical-controlled thyristor or by a plurality of optical-controlled thyristors connected in serial (e.g., the first optical-controlled thyristor U 1 and the second optical-controlled thyristor U 2 ), depending on the voltage value of the utility power. To equally divide the voltage drop caused by the optical-controlled component 12 , the first optical-controlled thyristor U 1 and the third equalizing resistor R 3 are connected in parallel and the second optical-controlled thyristor Us and the fourth equalizing resistor R 4 are connected in parallel. However, the way by which the voltage drop caused by the optical-controlled component 12 is equally divided is not restricted. Also, in other embodiments, the voltage drop caused by the optical-controlled component 12 can be divided unequally.

In FIG. 2 , the main circuit 30 is coupled to the SCR with optical-controlled driver 20 . The main circuit 30 has an A terminal (shown by “A” in FIG. 2 ), a B terminal (shown by “B” in FIG. 2 ) and a ground terminal. The A terminal of the main circuit 30 is coupled to the cathode of the second switching element Q 2 , and the B terminal of the main circuit 30 is coupled to the anode of the third switching element Q 3 . The main circuit 30 includes a first DC-DC converter 31 and a second DC-DC converter 32 . A first end of the first DC-DC converter 31 is the A terminal of the main circuit 30 , and a second end of the first DC-DC converter 31 is the ground terminal of the main circuit 30 . A first end of the second DC-DC converter 32 is the B terminal of the main circuit 30 , and a second end of the second DC-DC converter 32 is the ground terminal of the main circuit 30 .

The first DC-DC converter 31 includes a first inductor L 1 , a fourth switching transistor Q 4 , a fifth diode D 5 , a fourth capacitor C 4 and a sixth capacitor C 6 . A first end of the first inductor L 1 (i.e. the left end of the first inductor L 1 shown in FIG. 2 ) is coupled to the cathode of the second switching transistor Q 2 , and a second end of the first inductor L 1 (i.e. the right end of the first inductor L 1 shown in FIG. 2 ) is coupled to the drain of the fourth switching transistor Q 4 . The source of the fourth switching transistor Q 4 is coupled to the ground terminal of the main circuit 30 . The anode of the fifth diode D 5 is coupled to the second the first inductor L 1 , and the cathode of the fifth diode D 5 is coupled to a first end of the sixth capacitor C 6 (i.e. the upper end of the sixth capacitor C 6 shown in FIG. 2 ). A second end of the sixth capacitor C 6 (i.e. the lower end of the sixth capacitor C 6 shown in FIG. 2 ) is coupled to the ground terminal of the main circuit 30 . A first end of the fourth capacitor C 4 (i.e. the upper end of the fourth capacitor C 4 shown in FIG. 2 ) is coupled to the first end of the first inductor L 1 , and a second end of the fourth capacitor C 4 (i.e. the lower end of the fourth capacitor C 4 shown in FIG. 2 ) is coupled to the ground terminal of the main circuit 30 .

The second DC-DC converter 32 includes a second inductor L 2 , a fifth switching transistor Q 5 , a sixth diode D 6 , a fifth capacitor C 5 and a seventh capacitor C 7 . A first end of the second inductor L 2 (i.e. the left end of the second inductor L 2 shown in FIG. 2 ) is coupled to the anode of the third switching element Q 3 . The drain of the fifth switching transistor Q 5 is coupled to the ground terminal of the main circuit 30 , and the source of the fifth switching transistor Q 5 is coupled to a second end of the second inductor L 2 (i.e. the right end of the second inductor L 2 shown in FIG. 2 ). The cathode of the sixth diode D 6 is coupled to the second end of the second inductor L 2 . A first end of the fifth capacitor C 5 (i.e. the lower end of the fifth capacitor C 5 shown in FIG. 2 ) is coupled to the first end of the second inductor L 2 , and a second end of the fifth capacitor C 5 (i.e. the upper end of the fifth capacitor C 5 shown in FIG. 2 ) is coupled to the ground terminal of the main circuit 30 . A first end of the seventh capacitor C 7 (i.e. the lower end of the seventh capacitor C 7 shown in FIG. 2 ) is coupled to the anode of the sixth diode D 6 , and a second end of the seventh capacitor C 7 (i.e. the upper end of the seventh capacitor C 7 shown in FIG. 2 ) is coupled to the ground terminal of the main circuit 30 .

In this embodiment, the main circuit 30 is implemented by a high frequency DC-DC converter using an SCR (Silicon Controlled Rectifier; SCR). However, it is not limited thereto.

FIG. 3 is a circuit diagram showing the optical-controlled driving circuit in FIG. 2 working under a positive half cycle of the utility power, and FIG. 4 is a circuit diagram showing the optical-controlled driving circuit in FIG. 2 working under a negative half cycle of the utility power. As shown in FIG. 3 , when the optical-controlled driving circuit works under a positive half cycle of the utility power, the current provided by the utility power flows through the third diode D 3 , the second optical-controlled thyristor U 2 , the first optical-controlled thyristor U 1 , the first diode D 1 , the fifth resistor R 5 , the seventh resistor R 7 and finally to the first DC-DC converter 31 of the main circuit 30 . When the switch signal SCRIO is at high level, the resistances of the first optical-controlled thyristor U 1 and the second optical-controlled thyristor U 2 drop from a high resistance value to zero. As a result, the voltage drop of the seventh resistor R 7 increases so that the second switching transistor Q 2 is turned on and the voltage drop between the anode and the cathode of the second switching transistor Q 2 decreases to a normal turn-on voltage. The voltage drop of the seventh resistor R 7 maintains at a steady driving voltage of the SCR. The driving current of the SCR is provided by the utility power, which is a continual power, so that the damage rate of the SCR will be low when the SCR is in the on state.

As shown in FIG. 4 , when the optical-controlled driving circuit works under a negative half cycle of the utility power, the current provided by the utility power flows through the fourth diode D 4 , the second optical-controlled thyristor U 2 , the first optical-controlled thyristorU 1 , the second diode D 2 , the eighth resistor R 8 , and finally to the second DC-DC converter 32 . When the switch signal SCRIO is at high level, the resistances of the first optical-controlled thyristor U 1 and the second optical-controlled thyristor U 2 drop from a high resistance value to zero. As a result, the voltage drop of the eighth resistor R 8 increases so that the third switching transistor Q 3 is turned on and the voltage drop between the anode and the cathode of the third switching transistor Q 3 decreases to a normal turn-on voltage. The voltage drop of the eighth resistor R 8 maintains at a steady driving voltage of the SCR. The driving current of the SCR is provided by the utility power, which is a continual power, so that the damage rate of the SCR will be low when the SCR is in the on state.

In the present disclosure, the turn-on resistance of the SCR is continuous by virtue of the SCR with optical-controlled driver, so that when the SCR works under a light load, the SCR being in the on state can have a lower damage rate and a better operation efficiency.

According to the above embodiments, the present disclosure provides an optical-controlled driving circuit that can adjust the driving current according to the voltage of the utility power. Furthermore, the optical-controlled driving circuit can work under a high utility power environment with high voltages, large currents and severe surges, and thus has better operation efficiency. The circuit structure of the optical-controlled driving circuit is reliable, and can be used in a DC converter using the SCR as a switch element for increasing the operation efficiency when the DC converter works under a light load.

Therefore, the optical-controlled driving circuit provided by the present disclosure improves on the conventional SCR driving circuit. The optical-controlled driving circuit provided by the present disclosure can work under a high utility power environment with high voltages, large currents and severe surges and helps to increase the operation efficiency of a DC converter.

The descriptions illustrated supra set forth simply the preferred embodiments of the present disclosure; however, the characteristics of the present disclosure are by no means restricted thereto. All changes, alterations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the present disclosure delineated by the following claims.