TWM453321U - Constant current driving circuit - Google Patents

Abstract

A constant current driving circuit provides a constant current for driving a load element, and includes a rectifier, a transistor, a first resistor, a second resistor, a first capacitor and a second capacitor. The rectifier provides a rectified current to drive the load element. The transistor, the first resistor, the second resistor and the first capacitor form a feedback mechanism, and the second capacitor charges and discharges in response to the feedback mechanism, so as to stabilize a driving current flowing through the load element.

Description

Constant current drive circuit

The present invention relates to a constant current driving circuit, and more particularly to a constant current driving circuit for driving a light emitting diode.

Light Emitting Diode (LED) has the advantages of long life, small size, high shock resistance, low heat generation and low power consumption. Therefore, products with light-emitting diodes as light sources have become more and more popular recently. In the operation of the light-emitting diode, a slight change in the bias voltage causes a large fluctuation in the operating current. Therefore, the light-emitting diode must be driven with a constant current to avoid the phenomenon that the light-emitting diode is burnt; At the same time, the strobe is eliminated to avoid discomfort.

In general, the driving circuit of the conventional light-emitting diode is usually embedded with an AC-DC converter, or it must be matched with a transformer to generate the light-emitting diode by the AC power supply. The constant current of the body. However, the above drive circuits are often too complicated.

Therefore, how to simplify the circuit structure of the driving circuit of the light-emitting diode has been an important issue faced by various manufacturers.

This creation provides a constant current drive circuit that provides a stable drive current to the load element without the need for an embedded AC/DC converter or transformer.

The present invention proposes a constant current driving circuit for driving a load component, and includes a rectifier, a transistor, a first resistor, a second resistor, and a first Capacitor and second capacitor. The rectifier is electrically connected to the first end of the load element. The transistor has a first end, a second end and a control end, and the first end of the transistor is electrically connected to the second end of the load component. The first end of the first resistor is electrically connected to the first end of the transistor, and the second end of the first resistor is electrically connected to the control end of the transistor. The first end of the second resistor is electrically connected to the second end of the transistor, and the second end of the second resistor is electrically connected to the rectifier. The first end of the first capacitor is electrically connected to the control end of the transistor, and the second end of the first capacitor is electrically connected to the second end of the second resistor. The first end of the second capacitor is electrically connected to the first end of the load component, and the second end of the second capacitor is electrically connected to the second end of the second resistor.

In an embodiment of the present invention, the rectifier has a high voltage output terminal and a low voltage output terminal, and the rectifier outputs a rectified current through the high voltage output terminal.

In one embodiment of the present invention, the transistor is an N-type transistor. In addition, the rectifier is electrically connected to the first end of the load component through the high voltage output end, and the rectifier is electrically connected to the second end of the second resistor through the low voltage output end.

In an embodiment of the present invention, the transistor is a P-type transistor. In addition, the rectifier is electrically connected to the second end of the second resistor through the high voltage output end, and the rectifier is electrically connected to the first end of the load component through the low voltage output end.

Based on the above, the constant current driving circuit of the present invention uses a transistor (for example, an N-type transistor or a P-type transistor), a first resistor, a second resistor, and a first capacitor to form a feedback mechanism, and causes a second The capacitor is charged and discharged in response to this feedback mechanism. Thereby, the drive current flowing through the load element can be maintained stable. In addition, this creation will help simplify the current-sense drive circuit. The circuit structure, in turn, reduces the production cost of the constant current drive circuit.

In order to make the above features and advantages of the present invention more comprehensible, the following embodiments are described in detail with reference to the accompanying drawings.

1 is a circuit diagram of a constant current driving circuit in accordance with an embodiment of the present invention. Referring to FIG. 1, a constant current driving circuit is used to drive a load component 101, and includes a rectifier 110, an N-type transistor MN1, a first resistor R11, a second resistor R12, a first capacitor C11, and a second capacitor C12. Further, in the present embodiment, the load element 101 may be, for example, a light-emitting element for emitting a light source, and the load element 101 includes a plurality of light-emitting diodes 11 to 13. The LEDs 11 to 13 are connected in series with each other, and the anode of the LED 11 is electrically connected to the first end of the load element 101. The cathode of the LED 13 is electrically connected to the second end TM12 of the load element 101. .

In detail, the rectifier 110 has a high voltage output terminal EH and a low voltage output terminal EL, and the rectifier 110 is electrically connected to the first end TM11 of the load component 101 through the high voltage output terminal EH. The N-type transistor MN1 has a first end, a second end, and a control end. In addition, the first end of the N-type transistor MN1 is electrically connected to the second end TM12 of the load element 101. The first end of the first resistor R11 is electrically connected to the first end of the N-type transistor MN1, and the second end of the first resistor R11 is electrically connected to the control end of the N-type transistor MN1.

The first end of the second resistor R12 is electrically connected to the second end of the N-type transistor MN1, and the second end of the second resistor R12 is electrically connected to the low-voltage output terminal EL of the rectifier 110. The first end of the first capacitor C11 is electrically connected to the N-type battery The second end of the first capacitor C11 is electrically connected to the second end of the second resistor R12. The first end of the second capacitor C12 is electrically connected to the first end TM11 of the load component 101, and the second end of the second capacitor C12 is electrically connected to the second end of the second resistor R12.

It should be noted that the embodiment of FIG. 1 implements an N-type transistor MN1 by an N-channel metal oxide semiconductor transistor. Therefore, in the embodiment of FIG. 1, the first end, the second end, and the control end of the N-type transistor MN1 are the drain, the source, and the gate of the N-channel MOS transistor, respectively. In addition, in practical applications, the N-type transistor MN1 in FIG. 1 can also be implemented by an NPN bipolar transistor. In other words, in another embodiment, the first end, the second end, and the control end of the N-type transistor MN1 may also be the collector, the emitter, and the base of the NPN bipolar transistor, respectively.

In the overall operation, the rectifier 110 performs full-wave rectification on an AC power source, and accordingly generates a rectified current I11. Further, the rectifier 110 outputs a rectified current I11 through the high voltage output terminal EH to thereby drive the load element 101. The N-type transistor MN1, the first resistor R11, the second resistor R12 and the first capacitor C11 form a feedback mechanism, and the second capacitor C12 is charged and discharged according to the feedback mechanism, thereby causing the flow through the load element 101. The drive current I12 remains stable.

Specifically, the first resistor R11 is a large resistance resistor, delaying the charging and discharging of the first capacitor C11, so that the control voltage V _CT is maintained at a relatively stable voltage during a certain duty cycle. Furthermore, the reference voltage V _REF is maintained at a relatively stable voltage over a certain duty cycle by the current limiting effect of the N-type transistor MN1. That is, the reference voltage V _REF does not change with the fluctuation of the limit voltage V _LIM , so that the current through the second resistor R12 is maintained stable, and the current of the load element 101 connected in series with the second resistor R12 is stabilized. As such, when the rectified current I11 provided by the rectifier 110 is greater than the driving current I12 through the load element 101, excessive power is charged into the second capacitor C12 along the current direction 122, and the total of the second capacitor C12 is raised. Cross pressure. When the rectified current I11 provided by the rectifier 110 is less than the driving current I12 passing through the load element 101, the insufficient current will flow into the load element 101 from the second capacitor C12 along the current direction 121, and the total cross-voltage of the second capacitor C12 The current is reduced and the current is lowered.

In other words, the second capacitor C12 is selectively charged and discharged through the feedback mechanism formed by the N-type transistor MN1, the first resistor R11, the second resistor R12, and the first capacitor C11. As a result, although the rectified current I11 outputted by the rectifier 110 constantly fluctuates, the driving current I12 flowing through the load element 101 can be maintained stable.

In addition, the constant current driving circuit of FIG. 1 can provide a stable driving current I12 to the load component 101 without embedding an AC/DC converter or a transformer. Therefore, the embodiments exemplified in the present invention will contribute to simplifying the circuit structure of the constant current driving circuit and thereby reducing the production cost of the constant current driving circuit as compared with the conventional driving circuit.

After accumulating a duty cycle, when the total charge provided by the rectifier 110 is less than the total charge dissipated by the load element 101, the charge stored in the second capacitor C12 is reduced, so that the average cross-voltage of the second capacitor C12 is lowered, and the limiting voltage V is coupled. The average voltage of _LIM is reduced. The limiting voltage V _LIM adjusts the voltage of the first terminal of the first capacitor C11 through the first resistor R11. When the average voltage of the limit voltage V _LIM decreases, the control voltage V _CT also decreases correspondingly after several cycles, and the current of the load element 101 is reduced. Vice versa, when the total duty of the rectifier 110 is less than the total charge dissipated by the load element 101 after a duty cycle is accumulated, the current of the load element 101 is also increased after several cycles. Therefore, the line automatically balances the state in which the total charge provided by the rectifier 110 per cycle is equal to the total charge dissipated by the load element 101.

It is worth mentioning that, in practical applications, the resistance value of the first resistor R11 is greater than the resistance value of the second resistor R12, and the capacitance value of the first capacitor C11 is smaller than the capacitance value of the second capacitor C12. Further, if the resistance value of the second resistor R12 is larger, it means that the current to be supplied by the second capacitor C12 is also smaller. Therefore, when the resistance value of the second resistor R12 is larger, the capacitance value of the required second capacitor C12 is also smaller. That is, in practical applications, the resistance value of the second resistor R12 is inversely proportional to the capacitance value of the second capacitor C12.

Furthermore, the constant current driving circuit illustrated in FIG. 1 is designed mainly based on an N-type transistor, but it is not intended to limit the present creation, and any one of ordinary skill in the art may not deviate from the creation. Under the spirit and scope, the P-type transistor is used to realize the constant current driving circuit of the present invention.

For example, FIG. 2 is a circuit diagram of a constant current driving circuit according to another embodiment of the present invention. As shown in FIG. 2, the constant current driving circuit is used to drive the load component 201, and includes a rectifier 210, a P-type transistor MP2, a first resistor R21, a second resistor R22, a first capacitor C21, and a second capacitor C22. In addition, the load element 201 includes a plurality of light emitting diodes connected in series with each other The cathodes 21 to 23 are electrically connected to the second end TM22 of the load element 201, and the cathode of the LED 23 is electrically connected to the first end TM21 of the load element 201.

Referring to FIG. 1 and FIG. 2 simultaneously, the constant current driving circuit exemplified in the embodiment of FIG. 2 is equivalent to replacing the N-type transistor MN1 of FIG. 1 with a P-type transistor, and the rectifier of FIG. The high voltage output terminal EH of 110 and the low voltage output terminal EL are mutually adjusted.

In detail, when the constant current driving circuit is implemented mainly by the N-type transistor, as shown in the embodiment of FIG. 1, the rectifier 110 is electrically connected to the first end TM11 of the load element 101 through the high-voltage output terminal EH, and the rectifier 110 is electrically connected to the second end of the second resistor R12 through the low voltage output terminal EL. In addition, since the voltage level of the first terminal TM11 of the load component 101 is greater than the voltage level of the second terminal TM12, the first terminal TM11 of the load component 101 is electrically connected to the anode of the light-emitting diode 11, and the load is loaded. The second end TM12 of the element 101 is electrically connected to the cathode of the light-emitting diode 13.

In addition, when the constant current driving circuit is implemented mainly by the P type transistor, as shown in the embodiment of FIG. 2, the rectifier 210 is electrically connected to the second end of the second resistor R22 through the high voltage output terminal EH, and the rectifier 210 The first end TM21 of the load element 201 is electrically connected through the low voltage output terminal EL. In addition, since the voltage level of the second terminal TM22 of the load component 201 is greater than the voltage level of the first terminal TM21, the second terminal TM22 of the load component 201 is electrically connected to the anode of the LED 21 and the load is applied. The first end TM21 of the element 201 is electrically connected to the cathode of the light-emitting diode 23.

Referring to FIG. 2, similar to the embodiment of FIG. 1, the P-type transistor The first end of the MP2 is electrically connected to the second end TM22 of the load element 201. The first end of the first resistor R21 is electrically connected to the first end of the P-type transistor MP2, and the second end of the first resistor R21 is electrically connected to the control end of the P-type transistor MP2. The first end of the second resistor R22 is electrically connected to the second end of the P-type transistor MP2, and the second end of the second resistor R22 is electrically connected to the rectifier 210. The first end of the first capacitor C21 is electrically connected to the control end of the P-type transistor MP2, and the second end of the first capacitor C21 is electrically connected to the second end of the second resistor R22. The first end of the second capacitor C22 is electrically connected to the first end TM21 of the load component 201, and the second end of the second capacitor C22 is electrically connected to the second end of the second resistor R22.

It should be noted that the embodiment of FIG. 2 implements a P-type transistor MP2 with a P-channel MOS transistor. Therefore, in the embodiment of FIG. 2, the first end, the second end, and the control end of the P-type transistor MP2 are the drain, the source, and the gate of the P-channel MOS transistor, respectively. In addition, in practical applications, the P-type transistor MP2 in FIG. 2 can also be implemented by a PNP bipolar transistor. In other words, in another embodiment, the first end, the second end, and the control end of the P-type transistor MP2 may also be the collector, the emitter, and the base of the PNP bipolar transistor, respectively.

In addition, in the overall operation, the rectifier 210 performs full-wave rectification on an AC power source, and outputs a corresponding rectified current I21 through its high-voltage output terminal EH. Furthermore, the P-type transistor MP2, the first resistor R21, the second resistor R22 and the first capacitor C21 form a feedback mechanism, and the second capacitor C22 is charged and discharged according to the feedback mechanism, thereby causing the load to flow through the load. The drive current I22 of the element 201 remains stable. For example, in a work cycle Internally, when the charge provided by rectifier 210 is less than the charge required by load element 201, as indicated by current direction 221, second capacitor C22 will discharge load element 201. Conversely, during a duty cycle, when the charge provided by the rectifier 210 is greater than the charge required by the load element 201, as indicated by the current direction 222, the second capacitor C22 at this time will be charged. The detailed operation of the constant current drive circuit and the relative relationship of the components as exemplified in the embodiment of Fig. 2 are included in the embodiment of Fig. 1, and therefore will not be described herein.

In summary, the constant current driving circuit of the present invention uses a transistor (for example, an N-type transistor or a P-type transistor), a first resistor, a second resistor, and a first capacitor to form a feedback mechanism, and causes The second capacitor is charged and discharged in response to this feedback mechanism. Thereby, although the rectified current output by the rectifier constantly changes, the driving current flowing through the load element can be maintained stable. Furthermore, this creation will help simplify the circuit structure of the constant current drive circuit, thereby reducing the production cost of the constant current drive circuit.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any person having ordinary knowledge in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of protection of this creation is subject to the definition of the scope of the patent application attached.

110, 210‧‧‧Rectifier

EH‧‧‧High voltage output

EL‧‧‧ low voltage output

MN1‧‧‧N type transistor

MP2‧‧‧P type transistor

R11, R21‧‧‧ first resistance

R12, R22‧‧‧ second resistor

C11, C21‧‧‧ first capacitor

C12, C22‧‧‧ second capacitor

101, 201‧‧‧ load components

First end of TM11, TM21‧‧‧ load components

The second end of the TM12, TM22‧‧‧ load element

11~13, 21~23‧‧‧Lighting diode

I11, I21‧‧‧ rectified current

I12, I22‧‧‧ drive current

V _REF ‧‧‧reference voltage

V _LIM ‧‧‧Limit voltage

V _CT ‧‧‧ control voltage

121, 122, 221, 222‧‧‧ Current direction

1 is a circuit diagram of a constant current driving circuit in accordance with an embodiment of the present invention.

2 is a circuit diagram of a constant current driving circuit according to another embodiment of the present invention.

110‧‧‧Rectifier

EH‧‧‧High voltage output

EL‧‧‧ low voltage output

MN1‧‧‧N type transistor

R11‧‧‧First resistance

R12‧‧‧second resistance

C11‧‧‧first capacitor

C12‧‧‧second capacitor

101‧‧‧Load components

The first end of the TM11‧‧‧ load element

The second end of the TM12‧‧‧ load element

11~13‧‧‧Lighting diode

I11‧‧‧Rectified current

I12‧‧‧ drive current

V _REF ‧‧‧reference voltage

V _LIM ‧‧‧Limit voltage

V _CT ‧‧‧ control voltage

121, 122‧‧‧ Current direction

Claims (8)

A constant current driving circuit for driving a load component, and comprising: a rectifier electrically connected to the first end of the load component; a transistor having a first end, a second end and a control end, a first end of the transistor is electrically connected to the second end of the load component; a first resistor is electrically connected to the first end of the transistor, and the second end of the first resistor is electrically connected to the a second resistor, the first end of which is electrically connected to the second end of the transistor, the second end of the second resistor is electrically connected to the rectifier; a first capacitor, the first end of the electrical Connected to the control end of the transistor, the second end of the first capacitor is electrically connected to the second end of the second resistor; and a second capacitor is electrically connected to the first end of the load component The second end of the second capacitor is electrically connected to the second end of the second resistor. The constant current driving circuit of claim 1, wherein the load component is a light emitting component. The constant current driving circuit of claim 1, wherein the rectifier has a high voltage output terminal and a low voltage output terminal, and the rectifier outputs a rectified current through the high voltage output terminal. The constant current driving circuit of claim 3, wherein the transistor is an N-type transistor, and the rectifier is electrically connected to the first end of the load component through the high voltage output end, and the rectifier transmits the low voltage The output end is electrically connected to the second end of the second resistor. A constant current driving circuit as described in claim 4, The load component includes: a plurality of light emitting diodes, wherein the light emitting diodes are connected in series with each other, and an anode of the first one of the light emitting diodes is electrically connected to the load component At one end, the cathode of the last one of the light-emitting diodes is electrically connected to the second end of the load element. The constant current driving circuit of claim 3, wherein the transistor is a P-type transistor, and the rectifier is electrically connected to the second end of the second resistor through the high-voltage output terminal, and the rectifier transmits the The low voltage output is electrically connected to the first end of the load component. The constant current driving circuit of claim 6, wherein the load component comprises: a plurality of light emitting diodes, wherein the light emitting diodes are connected in series, and the first of the light emitting diodes The anode of the light-emitting diode is electrically connected to the second end of the load component, and the cathode of the last one of the light-emitting diodes is electrically connected to the first end of the load component. The constant current driving circuit of claim 1, wherein the transistor is composed of a MOS transistor or a double carrier transistor.