CN204497985U - LED drive circuit and switch power controller thereof - Google Patents
LED drive circuit and switch power controller thereof Download PDFInfo
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- CN204497985U CN204497985U CN201520219085.2U CN201520219085U CN204497985U CN 204497985 U CN204497985 U CN 204497985U CN 201520219085 U CN201520219085 U CN 201520219085U CN 204497985 U CN204497985 U CN 204497985U
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Abstract
The utility model provides a kind of LED drive circuit and switch power controller thereof, this controller have power port, port and high input voltage port, comprising: switching device, be connected on high input voltage port and ground port between connecting path on; Peak value turns off comparison circuit, receives supply voltage via power port, and peak value turns off comparison circuit and compares supply voltage with the reference voltage preset to obtain cut-off signals; Drive circuit, produces for controlling the drive singal stating switching device according to zero passage detection signal and cut-off signals, in response to zero passage detection signal, and drive singal control switch break-over of device, in response to cut-off signals, drive singal control switch device turns off; Wherein, ground port for connecting the first end of sampling resistor, the direct or indirect ground connection of the second end of sampling resistor.The utility model can save the current sample port of switch power controller, simplifies switch power controller, reduces chip cost, simplifies the design of Switching Power Supply.
Description
Technical field
The utility model relates to switch power technology, particularly relates to a kind of LED drive circuit and switch power controller thereof.
Background technology
In switch power supply system, the drive singal for on-off switching tube is normally controlled by peak value Current-Limiting Comparator, by comparing voltage on current sample port and internal reference voltage realizes.
Show the LED drive circuit of a kind of buck configuration in prior art with reference to figure 1, Fig. 1, this circuit adopts source pole driving mode.This LED drive circuit comprises resistance R1, electric capacity C2, sustained diode 1, output capacitance C1, inductance L 1, sampling resistor Rcs and switch power controller 100.Switch power controller 100 comprises the first power switch M1, the second power switch M2, zero cross detection circuit 101, logic and driver circuitry 102, comparator 103 and rest-set flip-flop 104.
Fig. 2 is the working timing figure of circuit shown in Fig. 1, is described the course of work of circuit shown in Fig. 1 below in conjunction with Fig. 1 and Fig. 2.First power switch M1 conducting, second power switch M2 also conducting, input current flows through output capacitance C1 and output, inductance L 1, second power switch M2, the first power switch M1, sampling resistor Rcs, the electric current flowed through in inductance L 1 is increased, inductance L 1 stored energy, now, output capacitance C1 is flowed through identical with the electric current flowing through sampling resistor Rcs with the electric current of output.The ON time of the first power switch M1, the second power switch M2 is controlled by the comparator 103 for peak value current limliting, when the electric current flowing through sampling resistor Rcs reaches set point Vr1/Rcs, the output signal upset of comparator 103, produces the drive singal GT of shutoff first power switch M1 and the second power switch M2 after rest-set flip-flop 104, logic and driver circuitry 102.
First power switch M1 and the second power switch M2 close and have no progeny, and the electric current flowing through inductance L 1 is through sustained diode 1 afterflow, and the electric current flowing through inductance L 1 reduces, and inductance L 1 releases energy output capacitance C1 and output.When the electric current flowing through inductance L 1 reduces to zero, zero cross detection circuit 101 detects the current over-zero of inductance L 1, produce zero passage detection signal ZCD and transfer to rest-set flip-flop circuit 104, through logic and drive current 102, produce the drive singal GT for opening the first power switch M1 and the second power switch M2.
First power switch M1, the second power switch M2 repeat switch motion above, and circuit continuous firing, is in critical current mode conducting state all the time, maintain constant output current.Output current is now Vr1/2Rcs.
In LED drive circuit shown in above-mentioned Fig. 1, drive singal for turning off first, second power switch M1, M2 is controlled by the comparator 103 for peak value current limliting, by comparing voltage on current sample port CS and internal reference voltage Vr1 realizes, electric current must be made to be flowed out by current sample port CS for such scheme and the voltage obtained on sampling resistor Rcs just can carry out.
Utility model content
Problem to be solved in the utility model is to provide a kind of LED drive circuit and switch power controller thereof, the current sample port of switch power controller can be saved, simplify switch power controller, reduce chip cost, be also conducive to the design simplifying Switching Power Supply.
For solving the problems of the technologies described above, the utility model provides a kind of switch power controller of LED drive circuit, have power port, port and high input voltage port, comprising:
Switching device, is connected on the connecting path between described high input voltage port and ground port;
Peak value turns off comparison circuit, and the power port via described switch power controller receives supply voltage, and described peak value turns off the more described supply voltage of comparison circuit with the reference voltage preset to obtain cut-off signals;
Drive circuit, the drive singal for controlling described switching device is produced according to zero passage detection signal and described cut-off signals, in response to described zero passage detection signal, described drive singal controls described switch device conductive, in response to described cut-off signals, described drive singal controls described switching device and turns off;
Wherein, described ground port for connecting the first end of sampling resistor, the direct or indirect ground connection of the second end of described sampling resistor.
According to an embodiment of the present utility model, described peak value turns off comparison circuit and comprises:
Potential-divider network, carries out dividing potential drop to produce the first comparative voltage to described supply voltage;
Comparator, its first input end receives described first comparative voltage, and its second input receives described reference voltage, and its output exports described cut-off signals.
According to an embodiment of the present utility model, described potential-divider network comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance, its second end ground connection;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage.
According to an embodiment of the present utility model, described peak value turns off comparison circuit and comprises:
Low pressure difference linear voltage regulator, its input receives described supply voltage, and its output exports the first comparative voltage and the second comparative voltage, and described first comparative voltage and the second comparative voltage have default voltage difference;
Sampling hold circuit, its input receives described second comparative voltage, turns off, samples to described second comparative voltage, in response to described switch device conductive, keep described second comparative voltage in response to described switching device;
Comparator, its first input end receives described first comparative voltage, and its second input connects the output of described sampling hold circuit, and its output exports described cut-off signals.
According to an embodiment of the present utility model, described low pressure difference linear voltage regulator comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance;
Metal-oxide-semiconductor, its drain electrode connects the second end of described second resistance, and its source electrode is via the 3rd grounding through resistance;
Amplifier, its first input end receives described reference voltage, and its second input connects the source electrode of described metal-oxide-semiconductor, and its output connects the grid of described metal-oxide-semiconductor;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage, and the second end of described second resistance and the drain electrode of described metal-oxide-semiconductor export described second comparative voltage.
According to an embodiment of the present utility model, described sampling hold circuit comprises:
Sampling switch, its first end receives described second comparative voltage, and its control end receives described drive singal;
Holding capacitor, its first end connects the second end of described sampling switch, its second end ground connection;
Wherein, the first end of described sampling switch is as the input of described sampling hold circuit, and the first end of described holding capacitor is as the output of described sampling hold circuit.
According to an embodiment of the present utility model, described switch power controller also comprises: zero cross detection circuit, carry out zero passage detection to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal.
According to an embodiment of the present utility model, described switching device comprises:
First power switch, its input connects described high input voltage port, and its control end connects described power port;
Second power switch, its input connects the output of described first power switch, and its control end receives described drive singal, and its output connects described ground port.
According to an embodiment of the present utility model, described switch power controller also comprises: zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the input of described second power switch.
According to an embodiment of the present utility model, described switching device comprises: the first power switch, and its input connects described high input voltage port, and its control end receives described drive singal, and its output connects described ground port.
According to an embodiment of the present utility model, described switch power controller also comprises: zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the control end of described first power switch.
According to an embodiment of the present utility model, described switch power controller also comprises: high voltage startup power supply circuits, and its one end connects described high input voltage port, and its other end connects described power port.
According to an embodiment of the present utility model, described drive circuit comprises:
Rest-set flip-flop, its set input receives described zero passage detection signal, and its RESET input receives described cut-off signals;
Logic and driver circuitry, its input connects the output of described rest-set flip-flop, and its output exports described drive singal.
For solving the problems of the technologies described above, the utility model additionally provides a kind of LED drive circuit, comprising:
Fly-wheel diode, its negative electrode connects input voltage incoming end to receive input voltage;
Output capacitance, its first end connects the negative electrode of described fly-wheel diode, and described output capacitance is used in parallel with load;
Inductance, its first end connects the anode of described fly-wheel diode, and its second end connects the second end of described output capacitance;
Switch power controller, described switch power controller have power port, port and high input voltage port, described switch power controller comprises:
Switching device, is connected on the connecting path between described high input voltage port and ground port;
Peak value turns off comparison circuit, and the power port via described switch power controller receives supply voltage, and described peak value turns off the more described supply voltage of comparison circuit with the reference voltage preset to obtain cut-off signals;
Drive circuit, the drive singal for controlling described switching device is produced according to zero passage detection signal and described cut-off signals, in response to described zero passage detection signal, described drive singal controls described switch device conductive, in response to described cut-off signals, described drive singal controls described switching device and turns off;
Wherein, described power port is via power supply capacity earth, and described ground port is via sampling resistor ground connection, and described high input voltage port connects the anode of described fly-wheel diode.
According to an embodiment of the present utility model, described peak value turns off comparison circuit and comprises:
Potential-divider network, carries out dividing potential drop to produce the first comparative voltage to described supply voltage;
Comparator, its first input end receives described first comparative voltage, and its second input receives described reference voltage, and its output exports described cut-off signals.
According to an embodiment of the present utility model, described potential-divider network comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance, its second end ground connection;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage.
According to an embodiment of the present utility model, described peak value turns off comparison circuit and comprises:
Low pressure difference linear voltage regulator, its input receives described supply voltage, and its output exports the first comparative voltage and the second comparative voltage, and described first comparative voltage and the second comparative voltage have default voltage difference;
Sampling hold circuit, its input receives described second comparative voltage, turns off, samples to described second comparative voltage, in response to described switch device conductive, keep described second comparative voltage in response to described switching device;
Comparator, its first input end receives described first comparative voltage, and its second input connects the output of described sampling hold circuit, and its output exports described cut-off signals.
According to an embodiment of the present utility model, described low pressure difference linear voltage regulator comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance;
Metal-oxide-semiconductor, its drain electrode connects the second end of described second resistance, and its source electrode is via the 3rd grounding through resistance;
Amplifier, its first input end receives described reference voltage, and its second input connects the source electrode of described metal-oxide-semiconductor, and its output connects the grid of described metal-oxide-semiconductor;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage, and the second end of described second resistance and the drain electrode of described metal-oxide-semiconductor export described second comparative voltage.
According to an embodiment of the present utility model, described sampling hold circuit comprises:
Sampling switch, its first end receives described second comparative voltage, and its control end receives described drive singal;
Holding capacitor, its first end connects the second end of described sampling switch, its second end ground connection;
Wherein, the first end of described sampling switch is as the input of described sampling hold circuit, and the first end of described holding capacitor is as the output of described sampling hold circuit.
According to an embodiment of the present utility model, described switch power controller also comprises: zero cross detection circuit, carry out zero passage detection to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal.
According to an embodiment of the present utility model, described switching device comprises:
First power switch, its input connects described high input voltage port, and its control end connects described power port;
Second power switch, its input connects the output of described first power switch, and its control end receives described drive singal, and its output connects described ground port.
According to an embodiment of the present utility model, described switch power controller also comprises: zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the input of described second power switch.
According to an embodiment of the present utility model, described switching device comprises: the first power switch, and its input connects described high input voltage port, and its control end receives described drive singal, and its output connects described ground port.
According to an embodiment of the present utility model, described switch power controller also comprises: zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the control end of described first power switch.
According to an embodiment of the present utility model, described LED drives resistance also to comprise: starting resistance, its first end connects described input voltage incoming end, and its second end connects described power port.
According to an embodiment of the present utility model, described switch power controller also comprises: high voltage startup power supply circuits, and its one end connects described high input voltage port, and its other end connects described power port.
According to an embodiment of the present utility model, described drive circuit comprises:
Rest-set flip-flop, its set input receives described zero passage detection signal, and its RESET input receives described cut-off signals;
Logic and driver circuitry, its input connects the output of described rest-set flip-flop, and its output exports described drive singal.
For solving the problems of the technologies described above, the utility model additionally provides another kind of LED drive circuit, comprising:
Fly-wheel diode, its plus earth;
Inductance, its first end connects the negative electrode of described fly-wheel diode;
Output capacitance, its first end connects the second end of described inductance, and its second end connects the anode of described fly-wheel diode and ground connection, and described output capacitance is used in parallel with load;
Switch power controller, described switch power controller have power port, port and high input voltage port, described switch power controller comprises:
Switching device, is connected on the connecting path between described high input voltage port and ground port;
Peak value turns off comparison circuit, and the power port via described switch power controller receives supply voltage, and described peak value turns off the more described supply voltage of comparison circuit with the reference voltage preset to obtain cut-off signals;
Drive circuit, the drive singal for controlling described switching device is produced according to zero passage detection signal and described cut-off signals, in response to described zero passage detection signal, described drive singal controls described switch device conductive, in response to described cut-off signals, described drive singal controls described switching device and turns off;
Wherein, described power port connects the negative electrode of described fly-wheel diode via power supply electric capacity, and described ground port connects the negative electrode of described fly-wheel diode via sampling resistor, and described high input voltage port connects input voltage incoming end to receive input voltage.
According to an embodiment of the present utility model, described peak value turns off comparison circuit and comprises:
Potential-divider network, carries out dividing potential drop to produce the first comparative voltage to described supply voltage;
Comparator, its first input end receives described first comparative voltage, and its second input receives described reference voltage, and its output exports described cut-off signals.
According to an embodiment of the present utility model, described potential-divider network comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance, its second end ground connection;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage.
According to an embodiment of the present utility model, described peak value turns off comparison circuit and comprises:
Low pressure difference linear voltage regulator, its input receives described supply voltage, and its output exports the first comparative voltage and the second comparative voltage, and described first comparative voltage and the second comparative voltage have default voltage difference;
Sampling hold circuit, its input receives described second comparative voltage, turns off, samples to described second comparative voltage, in response to described switch device conductive, keep described second comparative voltage in response to described switching device;
Comparator, its first input end receives described first comparative voltage, and its second input connects the output of described sampling hold circuit, and its output exports described cut-off signals.
According to an embodiment of the present utility model, described low pressure difference linear voltage regulator comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance;
Metal-oxide-semiconductor, its drain electrode connects the second end of described second resistance, and its source electrode is via the 3rd grounding through resistance;
Amplifier, its first input end receives described reference voltage, and its second input connects the source electrode of described metal-oxide-semiconductor, and its output connects the grid of described metal-oxide-semiconductor;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage, and the second end of described second resistance and the drain electrode of described metal-oxide-semiconductor export described second comparative voltage.
According to an embodiment of the present utility model, described sampling hold circuit comprises:
Sampling switch, its first end receives described second comparative voltage, and its control end receives described drive singal;
Holding capacitor, its first end connects the second end of described sampling switch, its second end ground connection;
Wherein, the first end of described sampling switch is as the input of described sampling hold circuit, and the first end of described holding capacitor is as the output of described sampling hold circuit.
According to an embodiment of the present utility model, described switch power controller also comprises: zero cross detection circuit, carry out zero passage detection to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal.
According to an embodiment of the present utility model, described switching device comprises:
First power switch, its input connects described high input voltage port, and its control end connects described power port;
Second power switch, its input connects the output of described first power switch, and its control end receives described drive singal, and its output connects described ground port.
According to an embodiment of the present utility model, described switch power controller also comprises: zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the input of described second power switch.
According to an embodiment of the present utility model, described switching device comprises: the first power switch, and its input connects described high input voltage port, and its control end receives described drive singal, and its output connects described ground port.
According to an embodiment of the present utility model, described switch power controller also comprises: zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the control end of described first power switch.
According to an embodiment of the present utility model, described LED drive circuit also comprises: starting resistance, and its first end connects described input voltage incoming end, and its second end connects described power port.
According to an embodiment of the present utility model, described switch power controller also comprises: high voltage startup power supply circuits, and its one end connects described high input voltage port, and its other end connects described power port.
According to an embodiment of the present utility model, described drive circuit comprises:
Rest-set flip-flop, its set input receives described zero passage detection signal, and its RESET input receives described cut-off signals;
Logic and driver circuitry, its input connects the output of described rest-set flip-flop, and its output exports described drive singal.
Compared with prior art, the utility model has the following advantages:
In the switch power controller of the utility model embodiment, utilize peak value to turn off the supply voltage of comparison circuit to power port and detect and compare, thus obtain the cut-off signals for shutdown switch device, with the peak current of control system.According to the switch power controller of the utility model embodiment, sampling resistor is connected to the ground port of switch power controller, namely output current is flow through by the ground port of switch power controller, thus eliminate current sample port of the prior art, simplify switch power controller, save circuit cost (such as chip cost), be also conducive to the design simplifying switch power supply system simultaneously.
Accompanying drawing explanation
Fig. 1 is the circuit diagram of a kind of voltage-dropping type LED drive circuit in prior art;
Fig. 2 is the working signal oscillogram of LED drive circuit shown in Fig. 1;
Fig. 3 is the circuit diagram of the LED drive circuit according to the utility model first embodiment;
Fig. 4 is the circuit diagram turning off comparator according to a kind of peak value of the utility model first embodiment;
Fig. 5 is the circuit diagram turning off comparator according to the another kind of peak value of the utility model first embodiment;
Fig. 6 is the working signal oscillogram of LED drive circuit shown in Fig. 3;
Fig. 7 is the circuit diagram of the LED drive circuit according to the utility model second embodiment;
Fig. 8 is the circuit diagram of the LED drive circuit according to the utility model the 3rd embodiment.
Embodiment
Below in conjunction with specific embodiments and the drawings, the utility model is described in further detail, but should not limit protection range of the present utility model with this.
First embodiment
With reference to figure 3, the LED drive circuit of the first embodiment comprises: sustained diode 1, output capacitance C1, inductance L 1, sampling resistor Rcs, starting resistance R1, power supply electric capacity C2 and switch power controller 300.Switch power controller 300 comprises switching device, zero cross detection circuit 301, peak value shutoff comparison circuit 303 and drive circuit.Wherein, switching device can comprise the first power switch M1 and the second power switch M2, and drive circuit can comprise rest-set flip-flop 304 and logic and driver circuitry 302.
Furthermore, the negative electrode of sustained diode 1 connects input voltage incoming end Vin, to receive input voltage; The first end of output capacitance C1 connects the negative electrode of sustained diode 1, and output capacitance C1 is used in parallel with load; The first end of inductance L 1 connects the anode of sustained diode 1, and the second end of inductance L 1 connects second end of output capacitance C1.
Switch power controller 300 have power port VDD, port GND and high input voltage port DRAIN.As a preferred embodiment, this Switching Power Supply 300 only have power port VDD, port GND and high input voltage port DRAIN, eliminate traditional current sample port.
Power port VDD connects input voltage incoming end Vin via starting resistance R1, and ground port GND is via sampling resistor Rcs ground connection, and high input voltage port DRAIN connects the first end of inductance L 1.The first end of power supply electric capacity C2 connects power port VDD, and the second end connects grounding ports GND.
It should be noted that, this LED drive circuit have two separate " ": systematically and controller ground, systematically as the reference ground of whole LED drive circuit, and controller ground is as reference of switch power controller 300.In the embodiment shown in fig. 1, the first end of sampling resistor Rcs is connected to controller ground, and second end of sampling resistor Rs is connected to systematically.In this article, " ground connection " acquiescence refers to and is connected to systematically.
The input of the first power switch M1 connects high input voltage port DRAIN, and control end connects power port VDD; The input of the second power switch M2 connects the output of the first power switch M1, and control end receives drive singal GT, and output connects grounding ports GND.
The input of zero cross detection circuit 301 connects the output of the first power switch M1 and the input of the second power switch M2.Zero cross detection circuit 301 carries out zero passage detection to the inductive current flowing through inductance L 1, and in response to inductive current zero passage, the output of zero cross detection circuit 301 exports zero passage detection signal ZCD, and this zero passage detection signal ZCD is used for actuating switch device.
Peak value turns off comparison circuit 303 and receives supply voltage via power port VDD, supply voltage and the reference voltage preset is compared, thus obtains cut-off signals OCP, and this cut-off signals OCP is used for shutdown switch device.
The set input S of rest-set flip-flop 304 receives zero passage detection signal ZCD, and the RESET input R receives cut-off signals OCP; The input of logic and driver circuitry 302 connects the output of rest-set flip-flop 304, the output output drive signal GT of logic and driver circuitry 302.Control the second power switch M2 conducting in response to zero passage detection signal ZCD, drive singal GT, thus control whole switch device conductive; In response to cut-off signals OCP, drive singal GT controls the second power switch M2 and turns off, thus controls the shutoff of whole switching device.
Fig. 4 shows a kind of implementation that peak value turns off comparison circuit.This peak value turns off comparison circuit and comprises: potential-divider network 400, carries out dividing potential drop to produce the first comparative voltage VA to supply voltage VDD; Comparator 401, its first input end (such as anode) receives the first comparative voltage VA, and its second input (such as negative terminal) receives reference voltage V ref, and its output exports cut-off signals.
As a nonrestrictive example, potential-divider network 400 comprises: resistance R2, and its first end receives supply voltage VDD; Resistance R3, second end of its first end contact resistance R2, its second end ground connection.Wherein, second end of resistance R2 and the first end of resistance R3 export the first comparative voltage VA.
Furthermore, resistance R2 and resistance R3 carries out dividing potential drop to supply voltage VDD, produces the first comparative voltage VA, VA=VDD*R3/ (R2+R3).When inductive current increases, when supply voltage VDD declines, the first comparative voltage VA is also along with decline, and after reaching reference voltage V ref, the output signal upset of comparator 401, exports cut-off signals to rest-set flip-flop, produce the drive singal GT of shutdown switch device.
Fig. 5 shows the another kind of implementation that peak value turns off comparison circuit.This peak value turns off comparison circuit and comprises: low pressure difference linear voltage regulator (LDO) 500, its input receives supply voltage VDD, its output exports the first comparative voltage VA and the second comparative voltage VB, and the first comparative voltage VA and the second comparative voltage VB has default voltage difference; Sampling hold circuit 503, its input receives the second comparative voltage VB, turns off in response to described switching device, samples to the second comparative voltage VB, in response to switch device conductive, keeps the second comparative voltage VB; Comparator 501, its first input end (such as anode) receives the first comparative voltage VA, and its second input connects the output of sampling hold circuit 503, and its output exports cut-off signals.
As a nonrestrictive example, this low pressure difference linear voltage regulator 500 comprises: resistance R2, and its first end receives supply voltage VDD; Resistance R3, second end of its first end contact resistance R2; Metal-oxide-semiconductor M3, second end of its drain electrode contact resistance R3, its source electrode is via resistance R4 ground connection; Amplifier 502, its first input end (such as anode) receives reference voltage V ref, and its second input (such as negative terminal) connects the source electrode of metal-oxide-semiconductor M3, and its output connects the grid of metal-oxide-semiconductor M3.Wherein, second end of resistance R2 and the first end of resistance R3 export the first comparative voltage VA, and second end of resistance R3 and the drain electrode of metal-oxide-semiconductor M3 export the second comparative voltage VB.
As a nonrestrictive example, this sampling hold circuit 503 comprises: sampling switch K1, and its first end receives the second comparative voltage VB, and its control end receives drive singal GT; Holding capacitor C3, its first end connects second end of sampling switch K1, its second end ground connection.Wherein, the first end of sampling switch K1 is as the input of sampling hold circuit 503, and the first end of holding capacitor C3 is as the output of sampling hold circuit 503.
Implementation shown in Fig. 5 have employed sampling maintenance technology, the impact that the fluctuation can eliminating supply voltage VDD better brings output current.Adopt the circuit structure shown in Fig. 5, the voltage difference V △=VA-VB=Vref*R3/R4 between the first comparative voltage VA and the second comparative voltage VB, if arrange R3=R4, so V △=Vref.Drive singal GT controls sampling switch K1, and sampling switch K1 samples to the second comparative voltage VB when closing, and is remained on holding capacitor C3 by the second comparative voltage VB obtained that samples.Subsequently after switch device conductive, supply voltage VDD increases along with inductive current and declines, first comparative voltage VA is also along with decline, and comparator 501 receives the second comparative voltage VB being through maintenance, its voltage remains unchanged, as VA<VB, namely when supply voltage VDD decrease beyond reference voltage V ref, the output signal upset of comparator 501, outputs to rest-set flip-flop, produces drive singal GT with shutdown switch device.
The work wave of LED drive circuit shown in Fig. 3 is shown with reference to figure 6, Fig. 6.Be described in detail below in conjunction with Fig. 3 and Fig. 6.
System is by starting working after starting resistance R1 electrifying startup.When drive singal GT control switch break-over of device (also i.e. the first power switch M1 and second power switch M2 all conductings), electric current flows through load, inductance L 1, first power switch M1 from input voltage incoming end Vin, after second power switch M2 port GND flow out, and flow through sampling resistor Rcs, along with the increase gradually of inductive current flowing through inductance L 1, now systematically, also namely second end of power supply electric capacity C2 can become negative pressure relative to controller ground, thus drags down the supply voltage of power port VDD gradually; After the voltage of supply voltage decline reaches reference voltage V ref, peak value turns off comparison circuit 303 and exports cut-off signals OCP, is generated the drive singal GT controlling control switch device and turn off by rest-set flip-flop 304, logic and driver circuitry 302.System enters the inductive discharge stage subsequently, when inductive current drops to zero, zero cross detection circuit 301 produces zero passage detection signal ZCD, generates the drive singal GT controlling control switch break-over of device, again make switch device conductive by rest-set flip-flop 304, logic and driver circuitry 302.Thus, the current peak Ip=Vref/Rcs of inductance L 1 is flow through.
Then, repeat shutoff above and turn-on action, circuit just always works in critical conduction mode, the constant output current of keeping system.
Second embodiment
Show the LED drive circuit of the second embodiment with reference to figure 7, Fig. 7, its structure and the first embodiment substantially similar, comprising: sustained diode 1, output capacitance C1, inductance L 1, sampling resistor Rcs, power supply electric capacity C2 and switch power controller 700.Switch power controller 700 comprises switching device, zero cross detection circuit 701, peak value shutoff comparison circuit 703 and drive circuit.
Second embodiment and the difference of the first embodiment are only that supply power mode, switching device and zero passage detection mode are different.
Wherein, the power supply of the second embodiment have employed high voltage startup power supply circuits 707, thus eliminates starting resistance.One end of high voltage startup power supply circuits 707 connects high input voltage port DRAIN, and the other end connects power port VDD.
Switching device only comprises the first power switch M1, manages under eliminating the driving power of source drive.The input of this first power switch M1 connects high input voltage port DRAIN, and control end receives drive singal GT, output head grounding.
The input of zero cross detection circuit 701 connects the control end of the first power switch M1, is namely detected by grid and realizes zero passage detection.
Operation principle and first embodiment of the second embodiment are similar, repeat no more here.
3rd embodiment
Show the LED drive circuit of the 3rd embodiment with reference to figure 8, Fig. 8, during this circuit, the equivalent electric circuit change in topology of circuit shown in Fig. 7, have employed floating ground structure.Ground port GND is not connected to controller ground.Compared with the second embodiment shown in Fig. 7, inductance L 1, output end vo ut, output capacitance C1, sustained diode 1 entirety are moved on to second end of sampling resistor Rcs by the 3rd embodiment, and the first end of sampling resistor Rcs are connected to ground port GND.In other words, the voltage of the first end of sampling resistor Rcs is as controller ground.
Operation principle and second embodiment of the 3rd embodiment are similar, repeat no more here
To sum up, according to LED drive circuit and the switch power controller of each embodiment of the utility model, by detecting to the supply voltage of power port the drive singal generated for shutdown switch device, and then the peak current of control system; Sampling resistor is connected to the ground port of switch power controller, and namely output current is flow through by the ground port of switch power controller, eliminates traditional current sample port.In typical applications, this switch power controller only needs high input voltage port DRAIN, power port VDD and ground port GND totally three ports, simplify circuit, when adopting chip to realize, can chip cost be saved, and the design of switch power supply system can be simplified.
The above is only preferred embodiment of the present utility model, not does any pro forma restriction to the utility model.Therefore, every content not departing from technical solutions of the utility model, just according to technical spirit of the present utility model to any simple amendment made for any of the above embodiments, equivalent conversion, all still belong in the protection range of technical solutions of the utility model.
Claims (41)
1. a switch power controller for LED drive circuit, have power port, port and high input voltage port, it is characterized in that, comprising:
Switching device, is connected on the connecting path between described high input voltage port and ground port;
Peak value turns off comparison circuit, and the power port via described switch power controller receives supply voltage, and described peak value turns off the more described supply voltage of comparison circuit with the reference voltage preset to obtain cut-off signals;
Drive circuit, the drive singal for controlling described switching device is produced according to zero passage detection signal and described cut-off signals, in response to described zero passage detection signal, described drive singal controls described switch device conductive, in response to described cut-off signals, described drive singal controls described switching device and turns off;
Wherein, described ground port for connecting the first end of sampling resistor, the direct or indirect ground connection of the second end of described sampling resistor.
2. switch power controller according to claim 1, is characterized in that, described peak value turns off comparison circuit and comprises:
Potential-divider network, carries out dividing potential drop to produce the first comparative voltage to described supply voltage;
Comparator, its first input end receives described first comparative voltage, and its second input receives described reference voltage, and its output exports described cut-off signals.
3. switch power controller according to claim 2, is characterized in that, described potential-divider network comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance, its second end ground connection;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage.
4. switch power controller according to claim 1, is characterized in that, described peak value turns off comparison circuit and comprises:
Low pressure difference linear voltage regulator, its input receives described supply voltage, and its output exports the first comparative voltage and the second comparative voltage, and described first comparative voltage and the second comparative voltage have default voltage difference;
Sampling hold circuit, its input receives described second comparative voltage, turns off, samples to described second comparative voltage, in response to described switch device conductive, keep described second comparative voltage in response to described switching device;
Comparator, its first input end receives described first comparative voltage, and its second input connects the output of described sampling hold circuit, and its output exports described cut-off signals.
5. switch power controller according to claim 4, is characterized in that, described low pressure difference linear voltage regulator comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance;
Metal-oxide-semiconductor, its drain electrode connects the second end of described second resistance, and its source electrode is via the 3rd grounding through resistance;
Amplifier, its first input end receives described reference voltage, and its second input connects the source electrode of described metal-oxide-semiconductor, and its output connects the grid of described metal-oxide-semiconductor;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage, and the second end of described second resistance and the drain electrode of described metal-oxide-semiconductor export described second comparative voltage.
6. switch power controller according to claim 4, is characterized in that, described sampling hold circuit comprises:
Sampling switch, its first end receives described second comparative voltage, and its control end receives described drive singal;
Holding capacitor, its first end connects the second end of described sampling switch, its second end ground connection;
Wherein, the first end of described sampling switch is as the input of described sampling hold circuit, and the first end of described holding capacitor is as the output of described sampling hold circuit.
7. switch power controller according to claim 1, is characterized in that, also comprises:
Zero cross detection circuit, carries out zero passage detection to the inductive current flowing through inductance, and in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal.
8. switch power controller according to claim 1, is characterized in that, described switching device comprises:
First power switch, its input connects described high input voltage port, and its control end connects described power port;
Second power switch, its input connects the output of described first power switch, and its control end receives described drive singal, and its output connects described ground port.
9. switch power controller according to claim 8, is characterized in that, also comprises:
Zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the input of described second power switch.
10. switch power controller according to claim 1, is characterized in that, described switching device comprises:
First power switch, its input connects described high input voltage port, and its control end receives described drive singal, and its output connects described ground port.
11. switch power controllers according to claim 10, is characterized in that, also comprise:
Zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the control end of described first power switch.
12. switch power controllers according to claim 10, is characterized in that, also comprise: high voltage startup power supply circuits, and its one end connects described high input voltage port, and its other end connects described power port.
13. switch power controllers according to any one of claim 1 to 12, it is characterized in that, described drive circuit comprises:
Rest-set flip-flop, its set input receives described zero passage detection signal, and its RESET input receives described cut-off signals;
Logic and driver circuitry, its input connects the output of described rest-set flip-flop, and its output exports described drive singal.
14. 1 kinds of LED drive circuits, is characterized in that, comprising:
Fly-wheel diode, its negative electrode connects input voltage incoming end to receive input voltage;
Output capacitance, its first end connects the negative electrode of described fly-wheel diode, and described output capacitance is used in parallel with load;
Inductance, its first end connects the anode of described fly-wheel diode, and its second end connects the second end of described output capacitance;
Switch power controller, described switch power controller have power port, port and high input voltage port, described switch power controller comprises:
Switching device, is connected on the connecting path between described high input voltage port and ground port;
Peak value turns off comparison circuit, and the power port via described switch power controller receives supply voltage, and described peak value turns off the more described supply voltage of comparison circuit with the reference voltage preset to obtain cut-off signals;
Drive circuit, the drive singal for controlling described switching device is produced according to zero passage detection signal and described cut-off signals, in response to described zero passage detection signal, described drive singal controls described switch device conductive, in response to described cut-off signals, described drive singal controls described switching device and turns off;
Wherein, described power port is via power supply capacity earth, and described ground port is via sampling resistor ground connection, and described high input voltage port connects the anode of described fly-wheel diode.
15. LED drive circuits according to claim 14, is characterized in that, described peak value turns off comparison circuit and comprises:
Potential-divider network, carries out dividing potential drop to produce the first comparative voltage to described supply voltage;
Comparator, its first input end receives described first comparative voltage, and its second input receives described reference voltage, and its output exports described cut-off signals.
16. LED drive circuits according to claim 15, is characterized in that, described potential-divider network comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance, its second end ground connection;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage.
17. LED drive circuits according to claim 14, is characterized in that, described peak value turns off comparison circuit and comprises:
Low pressure difference linear voltage regulator, its input receives described supply voltage, and its output exports the first comparative voltage and the second comparative voltage, and described first comparative voltage and the second comparative voltage have default voltage difference;
Sampling hold circuit, its input receives described second comparative voltage, turns off, samples to described second comparative voltage, in response to described switch device conductive, keep described second comparative voltage in response to described switching device;
Comparator, its first input end receives described first comparative voltage, and its second input connects the output of described sampling hold circuit, and its output exports described cut-off signals.
18. LED drive circuits according to claim 17, is characterized in that, described low pressure difference linear voltage regulator comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance;
Metal-oxide-semiconductor, its drain electrode connects the second end of described second resistance, and its source electrode is via the 3rd grounding through resistance;
Amplifier, its first input end receives described reference voltage, and its second input connects the source electrode of described metal-oxide-semiconductor, and its output connects the grid of described metal-oxide-semiconductor;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage, and the second end of described second resistance and the drain electrode of described metal-oxide-semiconductor export described second comparative voltage.
19. LED drive circuits according to claim 17, is characterized in that, described sampling hold circuit comprises:
Sampling switch, its first end receives described second comparative voltage, and its control end receives described drive singal;
Holding capacitor, its first end connects the second end of described sampling switch, its second end ground connection;
Wherein, the first end of described sampling switch is as the input of described sampling hold circuit, and the first end of described holding capacitor is as the output of described sampling hold circuit.
20. LED drive circuits according to claim 14, is characterized in that, described switch power controller also comprises:
Zero cross detection circuit, carries out zero passage detection to the inductive current flowing through described inductance, and in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal.
21. LED drive circuits according to claim 14, is characterized in that, described switching device comprises:
First power switch, its input connects described high input voltage port, and its control end connects described power port;
Second power switch, its input connects the output of described first power switch, and its control end receives described drive singal, and its output connects described ground port.
22. LED drive circuits according to claim 21, is characterized in that, described switch power controller also comprises:
Zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the input of described second power switch.
23. LED drive circuits according to claim 14, is characterized in that, described switching device comprises:
First power switch, its input connects described high input voltage port, and its control end receives described drive singal, and its output connects described ground port.
24. LED drive circuits according to claim 23, is characterized in that, described switch power controller also comprises:
Zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the control end of described first power switch.
25. LED drive circuits according to claim 14, is characterized in that, also comprise:
Starting resistance, its first end connects described input voltage incoming end, and its second end connects described power port.
26. LED drive circuits according to claim 14, is characterized in that, described switch power controller also comprises: high voltage startup power supply circuits, and its one end connects described high input voltage port, and its other end connects described power port.
27., according to claim 14 to the LED drive circuit according to any one of 26, is characterized in that, described drive circuit comprises:
Rest-set flip-flop, its set input receives described zero passage detection signal, and its RESET input receives described cut-off signals;
Logic and driver circuitry, its input connects the output of described rest-set flip-flop, and its output exports described drive singal.
28. 1 kinds of LED drive circuits, is characterized in that, comprising:
Fly-wheel diode, its plus earth;
Inductance, its first end connects the negative electrode of described fly-wheel diode;
Output capacitance, its first end connects the second end of described inductance, and its second end connects the anode of described fly-wheel diode and ground connection, and described output capacitance is used in parallel with load;
Switch power controller, described switch power controller have power port, port and high input voltage port, described switch power controller comprises:
Switching device, is connected on the connecting path between described high input voltage port and ground port;
Peak value turns off comparison circuit, and the power port via described switch power controller receives supply voltage, and described peak value turns off the more described supply voltage of comparison circuit with the reference voltage preset to obtain cut-off signals;
Drive circuit, the drive singal for controlling described switching device is produced according to zero passage detection signal and described cut-off signals, in response to described zero passage detection signal, described drive singal controls described switch device conductive, in response to described cut-off signals, described drive singal controls described switching device and turns off;
Wherein, described power port connects the negative electrode of described fly-wheel diode via power supply electric capacity, and described ground port connects the negative electrode of described fly-wheel diode via sampling resistor, and described high input voltage port connects input voltage incoming end to receive input voltage.
29. LED drive circuits according to claim 28, is characterized in that, described peak value turns off comparison circuit and comprises:
Potential-divider network, carries out dividing potential drop to produce the first comparative voltage to described supply voltage;
Comparator, its first input end receives described first comparative voltage, and its second input receives described reference voltage, and its output exports described cut-off signals.
30. LED drive circuits according to claim 29, is characterized in that, described potential-divider network comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance, its second end ground connection;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage.
31. LED drive circuits according to claim 28, is characterized in that, described peak value turns off comparison circuit and comprises:
Low pressure difference linear voltage regulator, its input receives described supply voltage, and its output exports the first comparative voltage and the second comparative voltage, and described first comparative voltage and the second comparative voltage have default voltage difference;
Sampling hold circuit, its input receives described second comparative voltage, turns off, samples to described second comparative voltage, in response to described switch device conductive, keep described second comparative voltage in response to described switching device;
Comparator, its first input end receives described first comparative voltage, and its second input connects the output of described sampling hold circuit, and its output exports described cut-off signals.
32. LED drive circuits according to claim 31, is characterized in that, described low pressure difference linear voltage regulator comprises:
First resistance, its first end receives described supply voltage;
Second resistance, its first end connects the second end of described first resistance;
Metal-oxide-semiconductor, its drain electrode connects the second end of described second resistance, and its source electrode is via the 3rd grounding through resistance;
Amplifier, its first input end receives described reference voltage, and its second input connects the source electrode of described metal-oxide-semiconductor, and its output connects the grid of described metal-oxide-semiconductor;
Wherein, the second end of described first resistance and the first end of described second resistance export described first comparative voltage, and the second end of described second resistance and the drain electrode of described metal-oxide-semiconductor export described second comparative voltage.
33. LED drive circuits according to claim 31, is characterized in that, described sampling hold circuit comprises:
Sampling switch, its first end receives described second comparative voltage, and its control end receives described drive singal;
Holding capacitor, its first end connects the second end of described sampling switch, its second end ground connection;
Wherein, the first end of described sampling switch is as the input of described sampling hold circuit, and the first end of described holding capacitor is as the output of described sampling hold circuit.
34. LED drive circuits according to claim 28, is characterized in that, described switch power controller also comprises:
Zero cross detection circuit, carries out zero passage detection to the inductive current flowing through described inductance, and in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal.
35. LED drive circuits according to claim 28, is characterized in that, described switching device comprises:
First power switch, its input connects described high input voltage port, and its control end connects described power port;
Second power switch, its input connects the output of described first power switch, and its control end receives described drive singal, and its output connects described ground port.
36. LED drive circuits according to claim 35, is characterized in that, described switch power controller also comprises:
Zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the input of described second power switch.
37. LED drive circuits according to claim 28, is characterized in that, described switching device comprises:
First power switch, its input connects described high input voltage port, and its control end receives described drive singal, and its output connects described ground port.
38., according to LED drive circuit according to claim 37, is characterized in that, described switch power controller also comprises:
Zero cross detection circuit, zero passage detection is carried out to the inductive current flowing through described inductance, in response to described inductive current zero passage, described zero cross detection circuit exports described zero passage detection signal, and the input of described zero cross detection circuit connects the control end of described first power switch.
39. LED drive circuits according to claim 28, is characterized in that, also comprise:
Starting resistance, its first end connects described input voltage incoming end, and its second end connects described power port.
40. LED drive circuits according to claim 28, is characterized in that, described switch power controller also comprises: high voltage startup power supply circuits, and its one end connects described high input voltage port, and its other end connects described power port.
41. LED drive circuits according to any one of claim 28 to 40, it is characterized in that, described drive circuit comprises:
Rest-set flip-flop, its set input receives described zero passage detection signal, and its RESET input receives described cut-off signals;
Logic and driver circuitry, its input connects the output of described rest-set flip-flop, and its output exports described drive singal.
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