CN109951070A - Voltage conversion circuit, conversion method and LED control circuit using the same - Google Patents

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. An AC input obtains an input voltage through a rectifier bridge, and the charge pump circuit receives the input. voltage, the driving circuit is connected to the 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 voltage conversion circuit of the invention has wide application range and high efficiency.

Description

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

technical field

The present invention relates to the field of power electronics, in particular to a voltage conversion circuit, a conversion method and an LED control circuit using the same.

Background technique

The schematic diagram of the prior art voltage conversion circuit is shown in Figure 1. After the AC voltage is rectified by the rectifier circuit, the input voltage VIN is obtained. The capacitor C1 is used to filter out the large ripple in the input voltage. The positive electrode of the LED receives the input voltage VIN, and the negative electrode is connected to the LED. Drive circuit. Since the minimum value of the input voltage VIN is smaller than the normal operating voltage of the LED, and the maximum value is much larger than the normal operating voltage of the LED, the input voltage application efficiency is low and the application range is narrow.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a voltage conversion circuit, a conversion method and an LED control circuit using the same, which are used to solve the problem of low utilization efficiency of input voltage in the prior art.

In order to achieve the above object, the present invention provides a voltage conversion circuit, including a charge pump circuit and a drive circuit, the AC input obtains an input voltage through a rectifier bridge, the charge pump circuit receives the input voltage, and the drive circuit is connected to the The output terminal of the charge pump circuit is used to control the working state of the charge pump circuit to adjust the output voltage or output current.

Optionally, the charge pump circuit includes a first capacitor and a second capacitor, two ends of the first capacitor are respectively connected to two output ends of the rectifier bridge, and when the second capacitor is charged, the input voltage charges the second capacitor; A capacitor and a 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, prolong 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;

When the output voltage or 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 decreased; or the charging and discharging current of the charge pump circuit is decreased.

Optionally, the second capacitor is charged with the first current and discharged with the second current.

Optionally, the charge pump circuit further includes a first switch tube and a second switch tube;

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 is discharged, the first switch is turned on and the second switch is turned off , the first capacitor and the second capacitor are connected in series.

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

Optionally, the charge pump circuit further includes a first diode and a second diode, the first end of the first switch is connected to the high potential end of the first capacitor, and the first end of the second switch is connected to the low end of the first capacitor. Potential terminal, 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 terminal of the first switch tube and the second switch tube, and the second end of the second capacitor is connected to the first diode The cathode of the tube is connected to 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.

Optionally, the charge pump circuit further 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, and the first end of the second switch tube is connected to the high potential end of the first capacitor. Potential terminal, 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 terminal of the first switch tube and the second switch tube, and the second end of the second capacitor is connected to the first diode The anode of the tube is connected to 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.

Optionally, the charge pump circuit further 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, and the second current source and the second switch tube are connected in series to form a first series circuit. The 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 and the second end of the second series circuit connection, 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, and the anode of the first diode is connected to the anode of the second diode. A capacitor high potential terminal is connected, and the cathode of the second diode is connected to the high potential output terminal of the charge pump circuit.

Optionally, the charge pump circuit further includes a first diode and a second diode, the first capacitor is connected in parallel with both ends of the rectifier bridge, and the first current source and the first switch 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, and the first end of the series circuit is connected to the high potential end of the first capacitor. The second terminal of the 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 series circuit and the second series circuit, and the second terminal of the second capacitor is connected to the anode of the first diode and the second terminal. The cathode of the electrode tube, 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.

The invention also provides a voltage conversion method, the AC input obtains the input voltage through the rectifier bridge, the charge pump circuit receives the input voltage, the drive circuit is connected to the output end of the charge pump circuit, and the working state of the charge pump circuit is controlled to adjust the the output voltage.

Optionally, the charge pump circuit includes a first capacitor and a second capacitor, two ends of the first capacitor are respectively connected to two output ends of the rectifier bridge, and when the second capacitor is charged, the input voltage charges the second capacitor; A capacitor and a 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, prolong 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;

When the output voltage or 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 decreased; or the charging and discharging current of the charge pump circuit is decreased.

The present invention also provides an LED control circuit, comprising any of the above voltage conversion circuits, wherein the driving circuit in the voltage conversion circuit is a linear driving circuit or a switch circuit.

Compared with the prior art, the present invention has the following advantages: the AC input obtains the input voltage through the rectifier bridge, the charge pump circuit receives the input voltage, the drive circuit is connected to the output end of the charge pump circuit, and when the output voltage or output current reaches the corresponding When the threshold is reached, the charge pump circuit is controlled to regulate the output voltage. The present invention greatly improves the utilization efficiency of the input voltage.

Description of drawings

1 is a schematic diagram of a prior art voltage conversion circuit;

2 is a schematic diagram of a first voltage conversion circuit of the present invention;

3 is a schematic diagram of a second voltage conversion circuit of the present invention;

Fig. 4 is the working waveform diagram of the voltage conversion circuit of the present invention;

Detailed ways

The preferred embodiments of the present invention will be 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 alternatives, modifications, equivalent methods and arrangements made within the spirit and scope of the present invention.

In order to provide the public with a thorough understanding of the present invention, specific details are set forth in the following preferred embodiments of the present invention, and those skilled in the art can fully understand the present invention without the description of these details.

The invention is described in more detail by way of example in the following paragraphs with reference to the accompanying drawings. It should be noted that, the accompanying drawings are all in a relatively simplified form and in an inaccurate scale, so as to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

As shown in FIG. 2, a schematic diagram of the first voltage conversion circuit of the present invention is shown. The voltage conversion circuit includes a charge pump circuit and a drive circuit U02. The AC input obtains the input voltage VIN through the rectifier bridge U01, and the charge pump circuit receives the input voltage VIN. The drive circuit U02 and the LED load are connected in series with the output capacitor C3, and 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 output current IOUT reaches the corresponding threshold, The charge pump circuit is controlled to regulate 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 The diode D1 and the second diode D2, the first current source I1 and the second current source I2 respectively output the first current and the second current. The first capacitor C1 is connected in parallel at both ends of the rectifier bridge, the first current source I1 and the first switch tube M1 are connected in series to form a first series circuit, the second current source I2 and the second switch tube M2 are connected in series to form a second series circuit, and the second series circuit is formed by the second current source I2 and the second switch tube M2 in series. The first end of a 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, and the second end of the second series circuit is connected to the low potential end of the first capacitor C1. The first end of the capacitor C2 is connected to the common end of the first series circuit and the second series circuit, the second end of the second capacitor C2 is connected to the negative electrode of the first diode D1 and the positive electrode of the second diode D2, and the positive electrode of the first diode D1 and the positive electrode of the second diode D2 are connected. The high potential terminal of the first capacitor C1 is connected, and the cathode of the second diode D2 is connected to the high potential terminal of the output capacitor C3.

As shown in FIG. 3, a schematic diagram of the second voltage conversion circuit of the present invention is shown. The voltage conversion circuit includes a charge pump circuit and a drive circuit U02. The AC input obtains the input voltage VIN through the rectifier bridge U00, and the charge pump circuit receives the input voltage VIN. The drive circuit U02 and the LED load are connected in series with the output capacitor C3, and 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 output current IOUT reaches the corresponding threshold, The charge pump circuit is controlled to regulate 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 The diode D1 and the second diode D2, the first current source I1 and the second current source I2 respectively output the first current and the second current. The first capacitor C1 is connected in parallel at both ends of the rectifier bridge, the first current source I1 and the first switch tube M1 are connected in series to form a first series circuit, the second current source I2 and the second switch tube M2 are connected in series to form a second series circuit, and the second series circuit is formed by the second current source I2 and the second switch tube M2 in series. The first end of a 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 is connected to the second end of the second series circuit, the second The first end of the capacitor C2 is connected to the common end of the first series circuit and the second series circuit, the second end of the second capacitor C2 is connected to the positive electrode of the first diode D1 and the negative electrode of the second diode D2, and the negative electrode of the first diode D1 and the negative electrode of the second diode D2 are connected. The low potential terminal of the first capacitor C1 is connected, and the anode of the second diode D2 is connected to the low potential terminal of the output capacitor C3.

When the first switch M1 is turned off and the second switch M2 is turned on, the input voltage VIN charges the first capacitor C1 and the second capacitor C2, and the voltage on the second capacitor C2 is the input voltage VIN (ignoring the voltage drop of the diode D1). When the first switch M1 is turned on and the second switch M2 is turned off, the first capacitor C1 and the second capacitor C2 are discharged in series, and the output voltage VOUT is equal to the sum of the voltages on the first capacitor C1 and the second capacitor C2. When the output voltage VOUT is greater than the first threshold VREF (or when 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 C2 decrease; when the output voltage VOUT is less than or equal to the first threshold VREF (or when 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.

As shown in FIG. 4 , the working waveform diagram of the conversion circuit of the present invention is illustrated. In conjunction with the embodiment of FIG. 2 , the input voltage VIN is taken as an example of linear direct current, PWM1 is the pulse width modulation signal of the first switch M1, and PWM2 is the second switch M2. pulse width modulated signal. When PWM1 is at a low level and PWM2 is at a high level, that is, when the first switch M1 is turned off and the second switch M2 is turned on, the second capacitor C2 is charged, the first voltage V1 is close to the input voltage VIN, the capacitor C3 is discharged, and the output The voltage VOUT decreases; when PWM1 is at a high level and PWM2 is at a low level, that is, when the first switch M1 is turned on and the second switch M2 is turned off, the first capacitor C1 and the second capacitor C2 discharge to the load in series, and the first When a voltage V1 is close to the sum of the voltage on the first capacitor C1 and the voltage on the second capacitor C2, that is, close to 2VIN, the capacitor C3 is charged, and the output voltage VOUT increases to close to 2VIN.

Although the embodiments are described and described separately above, some common technologies are involved, and in the opinion of those of ordinary skill in the art, they can be replaced and integrated between the embodiments. Reference is made to another example described.

The above-mentioned embodiments do not constitute a limitation on the protection scope of the technical solution. Any modifications, equivalent replacements and improvements made within the spirit and principles of the above-mentioned embodiments should be included within the protection scope of this technical solution.

Claims (12)

1. A voltage conversion circuit, characterized in that it comprises a charge pump circuit and a drive circuit, an AC input obtains an input voltage through a rectifier bridge, the charge pump circuit receives the input voltage, and the drive circuit is connected to the charge pump. The output terminal of the circuit controls the working state of the charge pump circuit to adjust the output voltage or output current. 2 . The voltage conversion circuit according to claim 1 , wherein the charge pump circuit comprises a first capacitor and a second capacitor, two ends of the first capacitor are respectively connected to two output ends of the rectifier bridge, and the second capacitor is charged. 3 . When , 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, prolong 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; When the output voltage or 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. 3 . The voltage conversion circuit of claim 2 , wherein the second capacitor is charged with a first current and discharged with a second current. 4 . 4. The voltage conversion circuit according to claim 2 or 3, wherein the charge pump circuit further comprises a first switch tube and a second switch tube; 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 is discharged, the first switch is turned on and the second switch is turned off , the first capacitor and the second capacitor are connected in series. 5. The voltage conversion circuit according to claim 4, wherein the charge pump circuit further comprises a first current source and a second current source, the first current source outputs a first current, and the second current The source outputs the second current. 6 . The voltage conversion circuit according to claim 4 , wherein the charge pump circuit further comprises a first diode and a second diode, and the first end of the first switch tube is connected to the high potential end of the first capacitor. 7 . , 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, and the first end of the second capacitor is connected to the common of the first switch tube and the second switch tube terminal, 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 charge pump circuit high potential output. 7 . The voltage conversion circuit according to claim 4 , wherein the charge pump circuit further comprises a first diode and a second diode, and the first end of the first switch tube is connected to the low potential end of the first capacitor. 8 . , the first end of the second switch is connected to the high-potential end of the first capacitor, the second end of the first switch is connected to the second end of the second switch, and the first end of the second capacitor is connected to the common of the first switch and the second switch terminal, 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 charge pump circuit The low potential output terminal. 8 . The voltage conversion circuit according to claim 5 , wherein the charge pump circuit further comprises a first diode and a second diode, and the first current source and the first switch are connected in series to form a first series connection. 9 . 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, and the first end of the first series circuit is connected to the high potential end of the first capacitor. The second terminal of the 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 series circuit and the second series circuit, and the second terminal of the second capacitor is connected to the cathode of the first diode and the second terminal of the second series circuit. The anode of the 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. 9 . The voltage conversion circuit according to claim 5 , wherein the charge pump circuit further comprises a first diode and a second diode, and the first current source and the first switch transistor are connected in series to form a first series connection. 10 . 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, and the first end of the first series circuit is connected to the low potential end of the first capacitor. The second terminal of the 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 series circuit and the second series circuit, and the second terminal of the second capacitor is connected to the anode of the first diode and the second terminal of the second series circuit. The cathode of the 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. 10. A voltage conversion method, characterized in that: an AC input obtains an input voltage through a rectifier bridge, a charge pump circuit receives the input voltage, a drive circuit is connected to the output end of the charge pump circuit, and controls the working state of the charge pump circuit to regulate the output voltage or output current. 11 . The voltage conversion method according to claim 10 , wherein the charge pump circuit comprises a first capacitor and a second capacitor, two ends of the first capacitor are respectively connected to two output ends of the rectifier bridge, and the second capacitor is charged. 12 . When , 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, prolong 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; When the output voltage or 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. 12. An LED control circuit, characterized in that it comprises any one of the above-mentioned voltage conversion circuits in claims 1-9, wherein the driving circuit in the voltage conversion circuit is a linear driving circuit or a switching circuit.