CN201541361U - Peak current control circuit, booster circuit and LED driver - Google Patents

Abstract

The utility model provides a peak current control circuit, a booster circuit and an LED driver, which are adaptable to the field of integrated circuits. The peak current control circuit includes a current source, a first switch, a second switch, an energy storage element and a comparator; one end of the first switch is connected with input voltage through the current source; the other end of the first switch is grounded through the energy storage element and the second switch; the other end of the first switch is also connected to a non-inverting input end of the comparator; an inverting input end of the comparator is grounded through reference voltage; and an output end of the comparator outputs voltage control signals. The peak current control circuit without a sensing resistor can detect peak current flowing through a power tube, reduce loss and simultaneously increase the efficiency of the booster circuit.

Description

A kind of peak current control circuit, booster circuit and led driver

Technical field

The utility model belongs to integrated circuit fields, relates in particular to a kind of peak current control circuit, booster circuit and led driver.

Background technology

The booster circuit that prior art provides as shown in Figure 1, input voltage V _INBe divided into two-way through after the inductance L, the one road flows to the drain D of power tube 1, output voltage V behind the process diode D1 of another road _OUT, the grid G of power tube 1 connects signal driving unit 2; Peak current control circuit 3 comprises: comparator B and detection resistance R _LMT, wherein detect resistance R _LMTBe connected between the source S and ground of power tube 1 in-phase input end of comparator B+the be connected to source S of power tube 1, the inverting input of comparator B-pass through voltage source V _LMTGround connection.

In order to detect the peak current I that flows through power tube 1 _PEAK, need between the source S of power tube 1 and ground, increase by one and detect resistance R _LMTYet, owing to increased the detection resistance R _LMTThe time brought power loss also for whole booster circuit.

The utility model content

The purpose of this utility model is to provide a kind of peak current control circuit, need increase by one detect the peak current that resistance detects the power tube of flowing through and cause the big problem of resistor power loss between the source electrode of power tube and ground thereby be intended to solve existing peak current control circuit.

The utility model is achieved in that a kind of peak current control circuit, comprising:

Current source, first switch, second switch, energy-storage travelling wave tube and comparator;

One end of described first switch is connected with input voltage by described current source, the other end of described first switch is by energy-storage travelling wave tube ground connection, also by described second switch ground connection, the other end of described first switch also is connected to the normal phase input end of described comparator to the other end of described first switch;

The inverting input of described comparator is by reference voltage ground connection; The output output voltage control signal of described comparator.

The purpose of this utility model also is to provide a kind of peak current control circuit, comprising:

Current mirror, current source, first switch, second switch, energy-storage travelling wave tube and comparator;

The input of described current mirror is connected with input voltage, and the output of described current mirror is connected with an end of described first switch, and the control end of described current mirror is by described current source ground connection;

The other end of described first switch is by described energy-storage travelling wave tube ground connection, and also by described second switch ground connection, the other end of described first switch also is connected to the normal phase input end of described comparator to the other end of described first switch;

The inverting input of described comparator is by reference voltage ground connection; The output output voltage control signal of described comparator.

As an embodiment of the present utility model, described current mirror further comprises: first switching tube and second switch pipe;

The source electrode of described first switching tube is connected with the source electrode of described second switch pipe and is connected with described input voltage;

The grid of described first switching tube is connected with the grid of described second switch pipe;

The drain electrode of described first switching tube is by described current source ground connection, and the drain electrode of described first switching tube also is connected with the grid of described first switching tube;

The drain electrode of described second switch pipe is connected to an end of described first switch.

As an embodiment of the present utility model, described energy-storage travelling wave tube is an electric capacity.

Another purpose of the present utility model is to provide a kind of booster circuit, comprises inductance, power tube, diode and signal driving unit; The output of described signal driving unit is connected to the grid of described power tube, and described signal driving unit Enable Pin connects input voltage, the earth terminal ground connection of described signal driving unit; One end of described inductance connects input voltage, and the other end of described inductance is connected to the drain electrode of described power tube, and the other end of described inductance also is connected with the anode of described diode, the negative electrode output voltage of described diode; Described booster circuit also comprises above-mentioned peak current control circuit; The output of described comparator is connected to the control end of described signal driving unit, the source ground of described power tube.

In the utility model embodiment, described booster circuit further comprises:

Filter capacitor; One end of described filter capacitor is connected to the negative electrode of described diode, other end ground connection.

As an embodiment of the present utility model, described booster circuit further comprises:

Load resistance is connected in parallel with described filter capacitor.

Another purpose of the present utility model is to provide a kind of led driver that adopts above-mentioned booster circuit.

The peak current control circuit that the utility model provides does not need to detect the peak current that resistance can detect the power tube of flowing through equally, has reduced loss, has improved the efficient of booster circuit simultaneously.

Description of drawings

Fig. 1 is the peak current control circuit that provides of prior art and the circuit diagram of booster circuit;

Fig. 2 is the peak current control circuit that provides of the utility model first embodiment and the circuit diagram of booster circuit;

Fig. 3 is the peak current control circuit that provides of the utility model second embodiment and the circuit diagram of booster circuit;

Fig. 4 is the circuit diagram of current source in the peak current control circuit that provides of the utility model embodiment.

Embodiment

In order to make the purpose of this utility model, technical scheme and advantage clearer,, the utility model is further elaborated below in conjunction with drawings and Examples.Should be appreciated that specific embodiment described herein only in order to explanation the utility model, and be not used in qualification the utility model.

The peak current control circuit that the utility model embodiment provides does not need to detect the peak current that resistance can detect the power tube of flowing through equally, has reduced loss, has improved the efficient of booster circuit simultaneously.

The peak current control circuit that the utility model embodiment provides is mainly used in the peak current of detection power pipe in the booster circuit, and this booster circuit is mainly used in the led driver; Fig. 2 shows the peak current control circuit 4 that the utility model first embodiment provides and the circuit of booster circuit, for convenience of explanation, only shows the part relevant with the utility model embodiment, and details are as follows.

Peak current control circuit 4 comprises: current source 44, first switch S 1, second switch S2, energy-storage travelling wave tube 41 and comparator 42; One end of first switch S 1 is connected with input voltage VIN by current source 44, the other end of first switch S 1 is by energy-storage travelling wave tube 41 ground connection, the other end of first switch S 1 is also by second switch S2 ground connection, the other end of first switch S 1 also be connected to the normal phase input end of comparator 42+; The inverting input of comparator 42-by reference voltage ground connection; The output output voltage control signal of comparator 42.

In the utility model embodiment, booster circuit comprises inductance L, power tube 1, diode D1 and signal driving unit 2; Wherein the Enable Pin 22 of signal driving unit 2 connects input voltage V _IN, the output 23 of signal driving unit 2 is connected to the grid G of power tube 1, earth terminal 24 ground connection of signal driving unit 2; One end of inductance L connects input voltage V _IN, the other end of inductance L is connected to the drain D of power tube 1, and the other end of inductance L also is connected with the anode of diode D1, the negative electrode output voltage V of diode D1 _OUTBooster circuit also comprises peak current control circuit 4; The input of peak current control circuit 4 connects input voltage V _IN, the output of peak current control circuit 4 is connected to the control end 21 of signal driving unit 2, the source S ground connection of power tube 1.

Fig. 3 shows the circuit of the peak current control circuit 4 that the utility model second embodiment provides, and details are as follows.

Peak current control circuit 4 comprises: current mirror 43, current source 44, first switch S 1, second switch S2, energy-storage travelling wave tube 41 and comparator 42; Wherein, the input of current mirror 43 and input voltage V _INConnect, the output of current mirror 43 is connected with an end of first switch S 1, and the control end of current mirror 43 is by current source 44 ground connection; The other end of first switch S 1 is by energy-storage travelling wave tube 41 ground connection, and the other end of first switch S 1 is also by second switch S2 ground connection, the other end of first switch S 1 also be connected to the normal phase input end of comparator 42+; The inverting input of comparator 42-by reference voltage ground connection; The output output voltage control signal of comparator 42.

As an embodiment of the present utility model, current mirror 43 further comprises: the first switching tube M1 and second switch pipe M2; Wherein, the source electrode of the first switching tube M1 is connected and is connected with input voltage VIN with the source electrode of second switch pipe M2; The grid of the first switching tube M1 is connected with the grid of second switch pipe M2; The drain electrode of the first switching tube M1 is by current source 44 ground connection, and the drain electrode of the first switching tube M1 also is connected with the grid of the first switching tube M1; The drain electrode of second switch pipe M2 is connected to an end of first switch S 1.

In the utility model embodiment, energy-storage travelling wave tube 41 can be capacitor C.

In the utility model embodiment, booster circuit further comprises: filter capacitor C _OUTFilter capacitor C _OUTAn end be connected to the negative electrode of diode D1, other end ground connection.As an embodiment of the present utility model, booster circuit also comprises: load resistance R _LOAD, with filter capacitor C _OUTBe connected in parallel.

For the utility model further is described, now be elaborated as follows in conjunction with instantiation according to Fig. 1 and Fig. 2:

When adopting booster circuit shown in Figure 1, in one-period, detect resistance R _LMTThe power W of loss _RLMTFor:

$W_{\mathrm{RLMT}}={\∫}_0^T{I}_d^2{R}_{\mathrm{LMT}}\mathrm{dt}$

$={\∫}_0^{T_{\mathrm{ON}}}{\left(\frac{I_{\mathrm{PEAK}}}{T_{\mathrm{ON}}}t\right)}^2{R}_{\mathrm{LMT}}\mathrm{dt}$

$=\frac{I_{\mathrm{PEAK}}^2}{T_{\mathrm{ON}}^2}{R}_{\mathrm{LMT}}\frac{t^3}{3}{|}_0^{T_{\mathrm{ON}}}$ Because: $\frac{I_d}{I_{\mathrm{PEAK}}}=\frac{t}{T_{\mathrm{ON}}}$

$=\frac{I_{\mathrm{PEAK}}^2{R}_{\mathrm{LMT}}{T}_{\mathrm{ON}}}{3}$

In the one-period, the power output W of booster circuit output _OUT=V _OUTI _OUTT, wherein, T is the cycle; Detect resistance R so _LMTThe power W of loss _RLMTWith power output W _OUTRatio be:

$\frac{W_{\mathrm{RLMT}}}{W_{\mathrm{OUT}}}=\frac{I_{\mathrm{PEAK}}^2{R}_{\mathrm{LMT}}{T}_{\mathrm{ON}}}{3V_{\mathrm{OUT}}{I}_{\mathrm{OUT}}T},=\frac{I_{\mathrm{PEAK}}^2{R}_{\mathrm{LMT}}D}{3V_{\mathrm{OUT}}{I}_{\mathrm{OUT}}}---\left[1\right]$

Because the duty ratio of critical non-continuous mode is:

$D=\frac{V_{\mathrm{OUT}}-V_{\mathrm{IN}}}{V_{\mathrm{OUT}}}---\left[2\right]$

And $\mathrm{\η}\frac{I_{\mathrm{PEAK}}}{2}{V}_{\mathrm{IN}}=V_{\mathrm{OUT}}{I}_{\mathrm{OUT}}$ [3], wherein η is the boosting efficiency of booster circuit;

To draw in formula [2] and [3] substitution formula [1]: detect resistance R _LMTThe power W of loss _RLMTWith power output W _OUTRatio be:

$\frac{W_{\mathrm{RLMT}}}{W_{\mathrm{OUT}}}=\frac{4R_{\mathrm{LMT}}{I}_{\mathrm{OUT}}(V_{\mathrm{OUT}}-V_{\mathrm{IN}})}{3{\mathrm{\η}}^2{V}_{\mathrm{IN}}^2}---\left[4\right]$

Suppose in the booster circuit shown in Figure 1 V _OUT=60V, V _IN=3V, I _OUT=20mA, efficient is 0.8, peak value detects voltage V _LMT=0.1V can calculate peak current I by formula [3] _PEAKFor:

$I_{\mathrm{PEAK}}=\frac{2\×60V\×20\mathrm{mA}}{3V\×0.8},=1A$

And the detection resistance R _LMTFor:

$R_{\mathrm{LMT}}=\frac{0.1V}{1A},=0.1\mathrm{\Ω}$

Detect resistance R as can be known by formula [4] _LMTPower loss percentage be:

$\frac{W_{\mathrm{RLMT}}}{W_{\mathrm{OUT}}}=\frac{4\&times;0.1\mathrm{\&Omega;}\&times;20\mathrm{mA}\&times;(60V-3V)}{3\&times;{0.8}^2\&times;3^2{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="H2009201308476E00011.png,H2009201308476E00012.png"\; state="\{\{state\}\}">V</figure-callout>}}^2},=2.6\%$

When as shown in Figure 2 the booster circuit that adopts that the utility model provides, need not to detect resistance R _LMTCan detect the peak current I of the power tube of flowing through equally _PEAK, that is: when first switch S, 1 closure, when second switch S2 disconnects, input voltage V _INCharge to capacitor C; When 1 disconnection of first switch S, when second switch S2 is closed, the capacitor C discharge.Give the charging current I of capacitor C _CHARGEFor:

$I_{\mathrm{CHARGE}}=\frac{V_{\mathrm{IN}}}{R}---\left[5\right]$

Charging current I _CHARGECan realize with Fig. 4.

Current-voltage relation characteristic according to electric capacity has:

$I_{\mathrm{CHARGE}}=C\frac{V_{\mathrm{REF}}}{T_{\mathrm{ON}}}---\left[6\right]$

T wherein _ONFor electric capacity charges to voltage V by zero level _REFTime.

By formula [5] and [6] as can be known, the charging interval T of capacitor C _ONFor:

$T_{\mathrm{ON}}=\frac{{\mathrm{RCV}}_{\mathrm{REF}}}{V_{\mathrm{IN}}}---\left[7\right]$

Charging interval T with above-mentioned capacitor C _ONControl input current arrives ground through inductance L, power tube 1 ON time.

Simultaneously, ON time T _ONCan also be by input voltage V _INThat branch road of drain D that arrives power tube 1 through inductance L is calculated:

$T_{\mathrm{ON}}=\frac{{\mathrm{LI}}_{\mathrm{PEAK}}}{V_{\mathrm{IN}}}---\left[8\right]$

Suppose that wherein each cycle internal inductance electric current charges to I by 0 _PEAK

By formula [7] and [8] peak current I as can be known _PEAKFor:

$I_{\mathrm{PEAK}}=\frac{{\mathrm{RCV}}_{\mathrm{REF}}}{L}---\left[9\right]$

From formula [9] as can be known, peak current I _PEAKOnly with resistance R, capacitor C, inductance L and reference voltage V _REFRelevant, need not to detect resistance R _LMTCan reach the purpose of control peak current equally, the booster circuit that adopts the utility model to provide like this can reduce by detecting resistance R _LMTThe power loss of bringing has improved boosting efficiency.

In the utility model embodiment, the physical circuit of current source 44 for convenience of explanation, only shows the part relevant with the utility model embodiment as shown in Figure 4, and details are as follows:

Current source 44 comprises operational amplifier 441, NMOS pipe 442 and resistance R 0, R1, R2; Wherein, resistance R 1 and resistance R 2 are connected to input voltage V successively _INAnd between the ground, the normal phase input end of operational amplifier 441+the be connected to end that is connected in series of resistance R 1, R2, the inverting input of operational amplifier 441-by resistance R 0 ground connection, the output of operational amplifier 441 is connected to the grid G of NMOS pipe 442, the source S of NMOS pipe 442 is passed through resistance R 0 ground connection, the electric current I of the drain D of process NMOS pipe 442 _CHARGEFor:

$I_{\mathrm{CHARGE}}=\frac{V_{\mathrm{IN}}}{R},$ R=R0 (R1+R2)/R2 wherein, the substitution following formula can get:

I _CHARGE＝[R2/(R1+R2)R0]V _IN......[10]

In the process of practice, can adopt following formula [10] to obtain electric current I _CHARGE

The peak current control circuit that the utility model embodiment provides does not need to detect the peak current that resistance can detect the power tube of flowing through equally, has reduced loss, has improved the efficient of booster circuit simultaneously.

The above only is preferred embodiment of the present utility model; not in order to restriction the utility model; all any modifications of within spirit of the present utility model and principle, being done, be equal to and replace and improvement etc., all should be included within the protection range of the present utility model.

Claims (8)

1. a peak current control circuit is characterized in that, described peak current control circuit comprises:

Current source, first switch, second switch, energy-storage travelling wave tube and comparator;

One end of described first switch is connected with input voltage by described current source, the other end of described first switch is by energy-storage travelling wave tube ground connection, also by described second switch ground connection, the other end of described first switch also is connected to the normal phase input end of described comparator to the other end of described first switch;

The inverting input of described comparator is by reference voltage ground connection; The output output voltage control signal of described comparator.

2. a peak current control circuit is characterized in that, described peak current control circuit comprises:

Current mirror, current source, first switch, second switch, energy-storage travelling wave tube and comparator;

The input of described current mirror is connected with input voltage, and the output of described current mirror is connected with an end of described first switch, and the control end of described current mirror is by described current source ground connection;

The other end of described first switch is by described energy-storage travelling wave tube ground connection, and also by described second switch ground connection, the other end of described first switch also is connected to the normal phase input end of described comparator to the other end of described first switch;

The inverting input of described comparator is by reference voltage ground connection; The output output voltage control signal of described comparator.

3. peak current control circuit as claimed in claim 2 is characterized in that, described current mirror further comprises: first switching tube and second switch pipe;

The source electrode of described first switching tube is connected with the source electrode of described second switch pipe and is connected with described input voltage;

The grid of described first switching tube is connected with the grid of described second switch pipe;

The drain electrode of described first switching tube is by described current source ground connection, and the drain electrode of described first switching tube also is connected with the grid of described first switching tube;

The drain electrode of described second switch pipe is connected to an end of described first switch.

4. peak current control circuit as claimed in claim 1 or 2 is characterized in that, described energy-storage travelling wave tube is an electric capacity.

5. a booster circuit comprises inductance, power tube, diode and signal driving unit; The output of described signal driving unit is connected to the grid of described power tube, and described signal driving unit Enable Pin connects input voltage, the earth terminal ground connection of described signal driving unit; One end of described inductance connects input voltage, and the other end of described inductance is connected to the drain electrode of described power tube, and the other end of described inductance also is connected with the anode of described diode, the negative electrode output voltage of described diode; It is characterized in that described booster circuit also comprises claim 1 or 2 described peak current control circuits; The output of described comparator is connected to the control end of described signal driving unit, the source ground of described power tube.

6. booster circuit as claimed in claim 5 is characterized in that, described booster circuit further comprises:

Filter capacitor, an end of described filter capacitor is connected to the negative electrode of described diode, other end ground connection.

7. booster circuit as claimed in claim 6 is characterized in that, described booster circuit further comprises:

Load resistance is connected in parallel with described filter capacitor.

8. a led driver is characterized in that, described led driver comprises the described booster circuit of claim 5.

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