Voltage conversion circuit, conversion method and LED control circuit using the same

Abstract

The present invention provides a voltage conversion circuit, a conversion method and an LED control circuit using the same. The voltage conversion circuit includes a charge pump circuit and a drive circuit. The AC input is passed through a rectifier bridge to obtain an input voltage. The charge pump circuit receives the input voltage. The drive circuit is connected to the output end of the charge pump circuit to control the working state of the charge pump circuit to adjust the output voltage or output current. The voltage conversion circuit of the present invention has a wide range of applications and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of power electronics, and in particular to a voltage conversion circuit, a conversion method, and an LED control circuit using the same. Background Technology

[0002] The schematic diagram of the existing voltage conversion circuit is as follows: Figure 1 As shown, the AC voltage is rectified to obtain the input voltage VIN. Capacitor C1 is used to filter out large ripples in the input voltage. The positive terminal of the LED receives the input voltage VIN, and the negative terminal is connected to the LED driver circuit. Because the minimum value of the input voltage VIN is less than the normal operating voltage of the LED, while its maximum value is much larger than the normal operating voltage of the LED, the efficiency of the input voltage application is low, and the application range is narrow. Summary of the Invention

[0003] The purpose of this invention is to provide a voltage conversion circuit, a conversion method, and an LED control circuit using the same, to solve the problem of low input voltage utilization efficiency in the prior art.

[0004] To achieve the above objectives, the present invention provides a voltage conversion circuit, including a charge pump circuit and a drive circuit. An AC input is rectified by a rectifier bridge to obtain an input voltage. The charge pump circuit receives the input voltage. The drive circuit is connected to the output terminal of the charge pump circuit and controls the operating state of the charge pump circuit to adjust the output voltage or output current.

[0005] Optionally, the charge pump circuit includes a first capacitor and a second capacitor. The two ends of the first capacitor are respectively connected to the two output terminals of the rectifier bridge. When the second capacitor is charging, the input voltage charges the second capacitor. The first capacitor and the second capacitor are connected in series to discharge to the load.

[0006] When the output voltage or output current is less than the corresponding threshold, extend the charging time of the second capacitor and shorten the discharging time of the second capacitor; or increase the charging and discharging frequency of the charge pump circuit; or increase the charging and discharging current of the charge pump circuit.

[0007] When the output voltage or output current exceeds the corresponding threshold, shorten the charging time of the second capacitor and extend the discharging time of the second capacitor; or, reduce the charging and discharging frequency of the charge pump circuit; or, reduce the charging and discharging current of the charge pump circuit.

[0008] Optionally, the second capacitor is charged with a first current and discharged with a second current.

[0009] Optionally, the charge pump circuit further includes a first switching transistor and a second switching transistor;

[0010] When the input voltage charges the second capacitor, the first switch is turned off and the second switch is turned on; when the second capacitor discharges, the first switch is turned on and the second switch is turned off, and the first capacitor and the second capacitor are connected in series.

[0011] Optionally, the charge pump circuit further includes a first current source and a second current source, wherein the first current source outputs a first current and the second current source outputs a second current.

[0012] Optionally, the charge pump circuit further includes a first diode and a second diode. The first terminal of the first switching transistor is connected to the high-potential terminal of the first capacitor, the first terminal of the second switching transistor is connected to the low-potential terminal of the first capacitor, the second terminals of the first and second switching transistors are connected, the first terminal of the second capacitor is connected to the common terminal of the first and second switching transistors, the second terminal of the second capacitor is connected to the cathode of the first diode and the anode of the second diode, the anode of the first diode is connected to the high-potential terminal of the first capacitor, and the cathode of the second diode is connected to the high-potential output terminal of the charge pump circuit.

[0013] Optionally, the charge pump circuit further includes a first diode and a second diode. The first terminal of the first switch is connected to the low-potential terminal of the first capacitor, the first terminal of the second switch is connected to the high-potential terminal of the first capacitor, the second terminals of the first switch and the second switch are connected, the first terminal of the second capacitor is connected to the common terminal of the first and second switches, the second terminal of the second capacitor is connected to the anode of the first diode and the cathode of the second diode, the cathode of the first diode is connected to the low-potential terminal of the first capacitor, and the anode of the second diode is connected to the low-potential output terminal of the charge pump circuit.

[0014] Optionally, the charge pump circuit further includes a first diode and a second diode. A first current source and a first switching transistor are connected in series to form a first series circuit. A second current source and a second switching transistor are connected in series to form a second series circuit. The first terminal of the first series circuit is connected to the high-potential terminal of the first capacitor. The first terminal of the second series circuit is connected to the low-potential terminal of the first capacitor. The second terminal of the first series circuit and the second terminal of the second series circuit are connected together. The first terminal of the second capacitor is connected to the common terminal of the first series circuit and the second series circuit. The second terminal of the second capacitor is connected to the cathode of the first diode and the anode of the second diode. The anode of the first diode is connected to the high-potential terminal of the first capacitor. The cathode of the second diode is connected to the high-potential output terminal of the charge pump circuit.

[0015] Optionally, the charge pump circuit further includes a first diode and a second diode. The first capacitor is connected in parallel across the rectifier bridge. A first current source and a first switching transistor are connected in series to form a first series circuit. A second current source and a second switching transistor are connected in series to form a second series circuit. The first terminal of the first series circuit is connected to the low-potential terminal of the first capacitor. The first terminal of the second series circuit is connected to the high-potential terminal of the first capacitor. The second terminal of the first series circuit is connected to the second terminal of the second series circuit. The first terminal of the second capacitor is connected to the common terminal of the first and second series circuits. The second terminal of the second capacitor is connected to the anode of the first diode and the cathode of the second diode. The cathode of the first diode is connected to the low-potential terminal of the first capacitor. The anode of the second diode is connected to the low-potential output terminal of the charge pump circuit.

[0016] The present invention also provides a voltage conversion method in which an AC input is rectified by a rectifier bridge to obtain an input voltage, a charge pump circuit receives the input voltage, and a drive circuit is connected to the output terminal of the charge pump circuit to control the working state of the charge pump circuit to adjust the output voltage.

[0017] Optionally, the charge pump circuit includes a first capacitor and a second capacitor. The two ends of the first capacitor are respectively connected to the two output terminals of the rectifier bridge. When the second capacitor is charging, the input voltage charges the second capacitor. The first capacitor and the second capacitor are connected in series to discharge to the load.

[0018] When the output voltage or output current is less than the corresponding threshold, extend the charging time of the second capacitor and shorten the discharging time of the second capacitor; or increase the charging and discharging frequency of the charge pump circuit; or increase the charging and discharging current of the charge pump circuit.

[0019] When the output voltage or output current exceeds the corresponding threshold, shorten the charging time of the second capacitor and extend the discharging time of the second capacitor; or, reduce the charging and discharging frequency of the charge pump circuit; or, reduce the charging and discharging current of the charge pump circuit.

[0020] The present invention also provides an LED control circuit, including any of the above voltage conversion circuits, wherein the driving circuit in the voltage conversion circuit is a linear driving circuit or a switching circuit.

[0021] Compared with existing technologies, this invention has the following advantages: The AC input is rectified by a rectifier bridge to obtain the input voltage, a charge pump circuit receives the input voltage, and a drive circuit is connected to the output terminal of the charge pump circuit. When the output voltage or output current reaches a corresponding threshold, the charge pump circuit is controlled to adjust the output voltage. This invention greatly improves the utilization efficiency of the input voltage. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a voltage conversion circuit in the prior art.

[0023] Figure 2 This is a schematic diagram of the first voltage conversion circuit of the present invention;

[0024] Figure 3 This is a schematic diagram of the second voltage conversion circuit of the present invention;

[0025] Figure 4 This is a waveform diagram of the voltage conversion circuit of the present invention. Detailed Implementation

[0026] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention.

[0027] To provide the public with a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the invention, but those skilled in the art can fully understand the invention without these details.

[0028] The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in a simplified form and use non-precise proportions, in order to facilitate and clearly illustrate the purpose of the embodiments of the invention.

[0029] like Figure 2The diagram illustrates the schematic of the first voltage conversion circuit of the present invention. The voltage conversion circuit includes a charge pump circuit and a drive circuit U02. The AC input is rectified by a bridge U01 to obtain the input voltage VIN. The charge pump circuit receives the input voltage VIN. The drive circuit U02 and the LED load are connected in series and then in parallel with the output capacitor C3. The two output terminals of the charge pump circuit are connected to the high-potential terminal and the low-potential terminal of the output capacitor C3, respectively. When the output voltage VOUT or the output current IOUT reaches a corresponding threshold, the charge pump circuit is controlled to adjust the output voltage VOUT. The charge pump circuit includes a first capacitor C1, a second capacitor C2, a first switching transistor M1, a second switching transistor M2, a first current source I1 (optional), a second current source I2 (optional), a first diode D1, and a second diode D2. The first current source I1 and the second current source I2 output a first current and a second current, respectively. The first capacitor C1 is connected in parallel across the rectifier bridge. The first current source I1 and the first switch M1 are connected in series to form a first series circuit. The second current source I2 and the second switch M2 are connected in series to form a second series circuit. The first end of the first series circuit is connected to the high-potential end of the first capacitor C1. The first end of the second series circuit is connected to the low-potential end of the first capacitor C1. The second end of the first series circuit is connected to the second end of the second series circuit. The first end of the second capacitor C2 is connected to the common terminal of the first and second series circuits. The second end of the second capacitor C2 is connected to the cathode of the first diode D1 and the anode of the second diode D2. The anode of the first diode D1 is connected to the high-potential end of the first capacitor C1. The cathode of the second diode D2 is connected to the high-potential end of the output capacitor C3.

[0030] like Figure 3The diagram illustrates the schematic of the second voltage conversion circuit of the present invention. The voltage conversion circuit includes a charge pump circuit and a drive circuit U02. The AC input is rectified by the rectifier bridge U00 to obtain the input voltage VIN. The charge pump circuit receives the input voltage VIN. The drive circuit U02 and the LED load are connected in series and then in parallel with the output capacitor C3. The two output terminals of the charge pump circuit are connected to the high-potential terminal and the low-potential terminal of the output capacitor C3, respectively. When the output voltage VOUT or the output current IOUT reaches a corresponding threshold, the charge pump circuit is controlled to adjust the output voltage VOUT. The charge pump circuit includes a first capacitor C1, a second capacitor C2, a first switch M1, a second switch M2, a first current source I1 (optional), a second current source I2 (optional), a first diode D1, and a second diode D2. The first current source I1 and the second current source I2 output a first current and a second current, respectively. The first capacitor C1 is connected in parallel across the rectifier bridge. The first current source I1 and the first switch M1 are connected in series to form a first series circuit. The second current source I2 and the second switch M2 are connected in series to form a second series circuit. The first end of the first series circuit is connected to the low-potential end of the first capacitor C1. The first end of the second series circuit is connected to the high-potential end of the first capacitor C2. The second end of the first series circuit and the second end of the second series circuit are connected. The first end of the second capacitor C2 is connected to the common terminal of the first and second series circuits. The second end of the second capacitor C2 is connected to the anode of the first diode D1 and the cathode of the second diode D2. The cathode of the first diode D1 is connected to the low-potential end of the first capacitor C1. The anode of the second diode D2 is connected to the low-potential end of the output capacitor C3.

[0031] When the first switch M1 is off and the second switch M2 is on, the input voltage VIN charges the first capacitor C1 and the second capacitor C2. The voltage across the second capacitor C2 is equal to the input voltage VIN (ignoring the voltage drop across diode D1). When the first switch M1 is on and the second switch M2 is off, the first capacitor C1 and the second capacitor C2 discharge in series, and the output voltage VOUT is equal to the sum of the voltages across the first capacitor C1 and the second capacitor C2. When the output voltage VOUT is greater than the first threshold VREF (or the output current is less than the corresponding threshold), the charging time of the second capacitor C2 decreases, the discharging time increases, or the charging and discharging frequency of the second capacitor C2 decreases; or the charging and discharging current of the second capacitor decreases. When the output voltage VOUT is less than or equal to the first threshold VREF (or the output current is greater than or equal to the corresponding threshold), the charging time of the second capacitor C2 increases, the discharging time decreases, or the charging and discharging frequency of the second capacitor C2 increases; or the charging and discharging current of the second capacitor increases.

[0032] like Figure 4 The diagram shown illustrates the working waveforms of the conversion circuit of this invention. Figure 2In this embodiment, taking linear DC as an example, the input voltage VIN is PWM1, which is the pulse width modulation signal for the first switch M1, and PWM2 is the pulse width modulation signal for the second switch M2. When PWM1 is low and PWM2 is high (i.e., the first switch M1 is off and the second switch M2 is on), the second capacitor C2 charges, the first voltage V1 approaches the input voltage VIN, the capacitor C3 discharges, and the output voltage VOUT decreases. When PWM1 is high and PWM2 is low (i.e., the first switch M1 is on and the second switch M2 is off), the first capacitor C1 and the second capacitor C2 discharge in series to the load, the first voltage V1 approaches the sum of the voltages on the first capacitor C1 and the second capacitor C2, i.e., approaches 2VIN, the capacitor C3 charges, and the output voltage VOUT increases to approach 2VIN.

[0033] Although the embodiments are described and illustrated separately above, some common technologies are involved. Those skilled in the art can replace and integrate them between the embodiments. If there is any content not explicitly described in one embodiment, then another embodiment that is described can be referred to.

[0034] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A voltage conversion circuit, characterized in that: It includes a charge pump circuit and a drive circuit. The AC input is passed through a rectifier bridge to obtain an input voltage. The charge pump circuit receives the input voltage. The drive circuit is connected to the output end of the charge pump circuit to control the working state of the charge pump circuit to adjust the output voltage or output current. The charge pump circuit comprises a first capacitor and a second capacitor, the two ends of the first capacitor are respectively connected to the two output ends of the rectifier bridge, when the second capacitor is charged, the input voltage charges the second capacitor; the first capacitor and the second capacitor are connected in series to discharge to the load; When the output voltage or the output current is less than the corresponding threshold, the charging time of the second capacitor is extended and the discharging time of the second capacitor is shortened; Alternatively, the charge and discharge frequency of the charge pump circuit is increased; or the charge and discharge current of the charge pump circuit is increased; When the output voltage or the output current is greater than the corresponding threshold, the charging time of the second capacitor is shortened and the discharging time of the second capacitor is prolonged; or, the charging and discharging frequency of the charge pump circuit is reduced; or, the charging and discharging current of the charge pump circuit is reduced.

2. The voltage conversion circuit according to claim 1, characterized in that: The second capacitor is charged with a first current and discharged with a second current.

3. The voltage conversion circuit according to claim 1 or 2, characterized in that: The charge pump circuit also includes a first switch tube and a second switch tube; When the input voltage charges the second capacitor, the first switch tube is turned off and the second switch tube is turned on; when the second capacitor discharges, the first switch tube is turned on and the second switch tube is turned off, and the first capacitor and the second capacitor are connected in series.

4. The voltage conversion circuit according to claim 3, characterized in that: The charge pump circuit further includes a first current source and a second current source, wherein the first current source outputs a first current and the second current source outputs a second current.

5. The voltage conversion circuit according to claim 3, characterized in that: The charge pump circuit also includes a first diode and a second diode, the first end of the first switch tube is connected to the high potential end of the first capacitor, the first end of the second switch tube is connected to the low potential end of the first capacitor, the second end of the first switch tube is connected to the second end of the second switch tube, the first end of the second capacitor is connected to the common end of the first switch tube and the second switch tube, the second end of the second capacitor is connected to the cathode of the first diode and the anode of the second diode, the anode of the first diode is connected to the high potential end of the first capacitor, and the cathode of the second diode is connected to the high potential output end of the charge pump circuit.

6. The voltage conversion circuit according to claim 3, characterized in that: The charge pump circuit also includes a first diode and a second diode, the first end of the first switch tube is connected to the low potential end of the first capacitor, the first end of the second switch tube is connected to the high potential end of the first capacitor, the second end of the first switch tube is connected to the second end of the second switch tube, the first end of the second capacitor is connected to the common end of the first switch tube and the second switch tube, the second end of the second capacitor is connected to the anode of the first diode and the cathode of the second diode, the cathode of the first diode is connected to the low potential end of the first capacitor, and the anode of the second diode is connected to the low potential output end of the charge pump circuit.

7. The voltage conversion circuit according to claim 4, characterized in that: The charge pump circuit also includes a first diode and a second diode. The first current source and the first switch tube are connected in series to form a first series circuit. The second current source and the second switch tube are connected in series to form a second series circuit. The first end of the first series circuit is connected to the high potential end of the first capacitor, the first end of the second series circuit is connected to the low potential end of the first capacitor, the second end of the first series circuit is connected to the second end of the second series circuit, the first end of the second capacitor is connected to the common end of the first series circuit and the second series circuit, the second end of the second capacitor is connected to the cathode of the first diode and the anode of the second diode, the anode of the first diode is connected to the high potential end of the first capacitor, and the cathode of the second diode is connected to the high potential output end of the charge pump circuit.

8. The voltage conversion circuit according to claim 4, characterized in that: The charge pump circuit also includes a first diode and a second diode. The first current source and the first switch tube are connected in series to form a first series circuit. The second current source and the second switch tube are connected in series to form a second series circuit. The first end of the first series circuit is connected to the low potential end of the first capacitor, the first end of the second series circuit is connected to the high potential end of the first capacitor, the second end of the first series circuit is connected to the second end of the second series circuit, the first end of the second capacitor is connected to the common end of the first series circuit and the second series circuit, the second end of the second capacitor is connected to the anode of the first diode and the cathode of the second diode, the cathode of the first diode is connected to the low potential end of the first capacitor, and the anode of the second diode is connected to the low potential output end of the charge pump circuit.

9. A voltage conversion method, characterized in that: The AC input is passed through a rectifier bridge to obtain an input voltage, a charge pump circuit receives the input voltage, a drive circuit is connected to an output end of the charge pump circuit, and controls the working state of the charge pump circuit to adjust the output voltage or output current; The charge pump circuit comprises a first capacitor and a second capacitor, the two ends of the first capacitor are respectively connected to the two output ends of the rectifier bridge, when the second capacitor is charged, the input voltage charges the second capacitor; the first capacitor and the second capacitor are connected in series to discharge to the load; When the output voltage or the output current is less than the corresponding threshold, the charging time of the second capacitor is extended and the discharging time of the second capacitor is shortened; Alternatively, the charge and discharge frequency of the charge pump circuit is increased; or the charge and discharge current of the charge pump circuit is increased; When the output voltage or the output current is greater than the corresponding threshold, the charging time of the second capacitor is shortened and the discharging time of the second capacitor is prolonged; or, the charging and discharging frequency of the charge pump circuit is reduced; or, the charging and discharging current of the charge pump circuit is reduced.

10. An LED control circuit, characterized in that: It comprises any one of the voltage conversion circuits of claims 1-8 above, wherein the driving circuit in the voltage conversion circuit is a linear driving circuit or a switching circuit.

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