A Method for Analyzing the Loss of an LED Driver Power Supply with a Boost-Buck Type Auxiliary Circuit

Abstract

The present invention discloses a method for analyzing the losses of an LED driving power supply with a buck-boost type auxiliary circuit, which is implemented by a loss analysis model of the LED driving power supply with a buck-boost type auxiliary circuit constructed by a switching mode analysis module, a MOSFET switching duty ratio determination module, a MOSFET conduction loss determination module, a MOSFET turn-off loss analysis module, a diode loss analysis module, an inductor loss analysis module, and an auxiliary circuit total loss analysis module. By using the characteristics of this type of circuit, the types of losses introduced by the buck-boost type auxiliary circuit and the loss determination method are analyzed, and the factors affecting the losses are analyzed. The present invention is used to determine the optimal parameters of the buck-boost type auxiliary circuit, thereby improving the overall efficiency of the AC-DC LED driving power supply.

Description

Technical Field

[0001] The present invention relates to a method for analyzing the losses of an LED driver power supply, particularly a method for analyzing the losses of an LED driver power supply with a buck-boost auxiliary circuit. Background Art

[0002] In traditional AC-DC LED driver power supplies, large electrolytic capacitors used to absorb double-frequency power ripples affect the lifespan of the LED lighting system. Therefore, an LED driver power supply with a buck-boost auxiliary circuit is proposed to improve the power supply reliability. The addition of the auxiliary circuit will affect the overall efficiency of the machine. However, in the previous loss analysis process, only the impact of the efficiency of the auxiliary circuit part on the overall efficiency was analyzed, and the loss analysis mainly relied on experimental tests, lacking a quantitative analysis and calculation process for losses. For this reason, the present invention analyzes the switching modes of the buck-boost auxiliary circuit in this power supply structure and constructs a loss analysis model to determine the optimal parameters of the circuit and improve the overall efficiency of the AC-DC LED driver power supply. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for analyzing the losses of an LED driver power supply with a buck-boost auxiliary circuit, and solve the problem that the introduction of losses by the auxiliary circuit affects the overall efficiency of the machine.

[0004] The specific steps of a method for analyzing the losses of an LED driver power supply with a buck-boost auxiliary circuit are as follows:

[0005] The first step is to construct a loss analysis system for an LED driver power supply with a buck-boost auxiliary circuit

[0006] The loss analysis system for an LED driver power supply with a buck-boost auxiliary circuit includes: a MOSFET switching mode analysis module, a MOSFET switching duty cycle determination module, a MOSFET conduction loss determination module, a MOSFET turn-off loss analysis module, a diode loss analysis module, an inductor loss analysis module, and an auxiliary circuit total loss analysis module.

[0007] The function of the MOSFET switching mode analysis module is: analyze the three working states included in the buck-boost auxiliary circuit, analyze the current changes in each working mode, and the change trends of the parameters of the energy storage capacitor voltage and the ripple isolation capacitor voltage.

[0008] The function of the MOSFET duty cycle determination module: determine the duty cycle d1 of the MOSFET switch and the duty cycle d2 of the diode according to the input and output current characteristics of the auxiliary circuit.

[0009] The function of the MOSFET conduction loss determination module is: according to the MOSFET being approximately a constant resistance R after conduction dsonDetermine the conduction loss of the MOSFET switch based on its characteristics and the characteristics of the circuit input current variation.

[0010] The function of the MOSFET switching loss analysis module is as follows: Based on the characteristic that the auxiliary circuit operates in the discontinuous current mode, only analyze the MOSFET turn-off loss. According to the turn-off characteristic of the MOSFET device, combine the average value of the energy storage capacitor voltage to determine the MOSFET switching loss.

[0011] The function of the diode loss analysis module is as follows: Determine the diode loss based on the forward conduction voltage characteristic of the diode and the output current characteristic of the auxiliary circuit.

[0012] The function of the inductor loss analysis module is as follows: Based on the DC resistance R of the inductor coil typ and the equivalent resistance R on the line, as well as the output current characteristic, determine the copper loss of the inductor coil.

[0013] The function of the auxiliary circuit total loss analysis module is as follows: Based on the losses included in the buck-boost type auxiliary circuit, determine the average value V of the matching energy storage capacitor voltage cb0 , optimize the overall efficiency of the power supply, and use it as the basis for parameter selection.

[0014] In the second step, the MOSFET switching mode analysis module analyzes the circuit operating state

[0015] The MOSFET switching mode analysis module analyzes the circuit state according to the state of the MOSFET switch at different times. Set the MOSFET switch to conduct with a duty cycle d1, and the conduction time is [t1, t2]. The ripple isolation capacitor C a and the energy storage capacitor C b discharge, and the input current of the auxiliary circuit increases. The MOSFET turns off at time t2. In the time period [t2, t3], the output current of the buck-boost type auxiliary circuit charges the ripple isolation capacitor C a , the voltage v of the ripple isolation capacitor ca rises, and the voltage v of the energy storage capacitor cb drops. The current of the inductor L a becomes zero at time t3. In the time period [t3, t4], v ca and v cb drop.

[0016] In the third step, the MOSFET switch duty cycle determination module determines the MOSFET switch duty cycle

[0017] The MOSFET switch duty cycle determination module first sets the duty cycle of the MOSFET switch to d1. In addition, define the duty cycle of the diode as d2. According to the value V of v cb at t equal to 0, the output current I cb0 ​o , and the switching period T sw_a , determine the duty cycles d1 and d2, which are expressed by formulas (1) and (2):

[0018]

[0019]

[0020] In the fourth step, the MOSFET switch conduction loss determination module determines the MOSFET switch conduction loss

[0021] The MOSFET switch conduction loss determination module determines the MOSFET switch conduction loss according to the on-resistance R of the MOSFET switch dson , the output power P of the circuit o , the inductor L a , the switching frequency f sw_a , the output voltage V of the circuit o , the energy storage capacitor C b the maximum value V of the voltage across both ends cbmax and the minimum value V cbmin , determine the MOSFET switch conduction loss, which is expressed by formula (3):

[0022]

[0023] In the fifth step, the MOSFET switch loss analysis module analyzes the loss during the MOSFET switch switching process

[0024] The MOSFET switch loss analysis module first analyzes the circuit characteristics and knows that the buck-boost auxiliary circuit operates in the discontinuous current mode. Therefore, the MOSFET switch can achieve zero-current turn-on and the turn-on loss is zero. In the buck-boost auxiliary circuit, the MOSFET switch tube is hard turned off. During the turn-off process, the turn-off voltage and current waveforms will overlap, generating turn-off loss. According to the turn-off time t of the MOSFET device itself off , the duty cycle d1, the energy storage capacitor C b the voltage v cb the value V at the moment when t is equal to 0 cb0 , determine the MOSFET switch loss, that is, the MOSFET turn-off loss, which is expressed by formula (4):

[0025]

[0026] In the sixth step, the diode loss analysis module analyzes the loss generated by the diode. When the diode in the buck-boost auxiliary circuit conducts, the on-resistance will generate on-loss. According to the forward conduction voltage V of the diode F , and the output current I of the power supply o , determine the diode loss, which is expressed by formula (5):

[0027]

[0028] Step 7: The inductance loss analysis module analyzes the loss introduced by the inductor

[0029] The loss of the inductor in the circuit of the inductance loss analysis module is mainly copper loss. Based on the DC resistance R of the inductor coil typ and the equivalent resistance R on the line, duty cycles d1 and d2, the inductance loss is determined and expressed by formula (6):

[0030]

[0031] Step 8: The total loss analysis module of the auxiliary circuit analyzes the factors affecting the loss of this circuit

[0032] Based on the determined conduction loss of the MOSFET, turn-off loss of the MOSFET, diode loss, and inductance loss, the total loss of the buck-boost type auxiliary circuit is determined by the total loss analysis module of the auxiliary circuit and expressed by formula (7). It is determined that the loss of the buck-boost type auxiliary circuit is related to the average voltage V b of C cb0 . The larger the value of V cb0 , the smaller the loss of the buck-boost type auxiliary circuit and the higher the overall efficiency of the system.

[0033] P loss_total = P loss_on_avg + P loss_close_avg + P loss_diode_avg + P loss_La_avg (7)

[0034] So far, the establishment of the loss analysis model and the analysis of loss influence of the LED drive power supply with a buck-boost type auxiliary circuit are completed.

[0035] The present invention analyzes the loss of the LED drive power supply with a buck-boost type auxiliary circuit, determines appropriate parameters to reduce the influence of the buck-boost type auxiliary circuit on the overall efficiency of the power supply, helps to improve the overall efficiency of the AC-DC LED power supply, and solves the problem that the LED drive power supply with an auxiliary circuit has a low efficiency and is difficult to be actually applied. Specific embodiments

[0036] The specific steps of a method for analyzing the loss of an LED drive power supply with a buck-boost type auxiliary circuit are as follows:

[0037] Step 1: Construct an LED drive power supply loss analysis system with a buck-boost type auxiliary circuit

[0038] LED driver power loss analysis system with a buck-boost auxiliary circuit, including: MOSFET switching mode analysis module, MOSFET switching duty cycle determination module, MOSFET conduction loss determination module, MOSFET turn-off loss analysis module, diode loss analysis module, inductor loss analysis module, and total loss analysis module of the auxiliary circuit.

[0039] The function of the MOSFET switching mode analysis module is to analyze the three operating states of the buck-boost auxiliary circuit, analyze the current changes in each operating mode, and the changing trends of the energy storage capacitor voltage and the ripple isolation capacitor voltage parameters.

[0040] The function of the MOSFET duty cycle determination module is to determine the duty cycle d1 of the MOSFET switch and the duty cycle d2 of the diode according to the input and output current characteristics of the auxiliary circuit.

[0041] The function of the MOSFET conduction loss determination module is to determine the MOSFET switch conduction loss according to the characteristic that the MOSFET approximates a constant resistance R dson after conduction, and the changing characteristic of the circuit input current.

[0042] The function of the MOSFET switching loss analysis module is to only analyze the MOSFET turn-off loss according to the characteristic that the auxiliary circuit operates in the discontinuous current mode. Determine the MOSFET switching loss according to the turn-off characteristic of the MOSFET device and the average value of the energy storage capacitor voltage.

[0043] The function of the diode loss analysis module is to determine the diode loss according to the forward conduction voltage characteristic of the diode and the output current characteristic of the auxiliary circuit.

[0044] The function of the inductor loss analysis module is to determine the copper loss of the inductor coil according to the DC resistance R typ of the inductor coil and the equivalent resistance R on the line, and the output current characteristic.

[0045] The function of the total loss analysis module of the auxiliary circuit is to determine the average value V cb0 of the matching energy storage capacitor voltage according to the losses included in the buck-boost auxiliary circuit, optimize the overall efficiency of the power supply, and serve as the basis for parameter selection.

[0046] In the second step, the MOSFET switching mode analysis module analyzes the circuit operating state

[0047] The MOSFET switching mode analysis module analyzes the circuit state according to the states of the MOSFET switch at different times. Assume that the MOSFET switch conducts with a duty cycle d1, the conduction time is [t1, t2], the ripple isolation capacitor C a and the energy storage capacitor Cb During discharge, the input current of the auxiliary circuit increases. The MOSFET turns off at time t2. During the time period [t2, t3], the output current of the buck-boost type auxiliary circuit charges the ripple isolation capacitor C a , and the voltage v of the ripple isolation capacitor ca rises, while the voltage v of the energy storage capacitor cb drops. The current of inductor L a becomes zero at time t3. During the time period [t3, t4], v ca and v cb drop.

[0048] In the third step, the MOSFET switch duty cycle determination module determines the MOSFET switch duty cycle

[0049] The MOSFET switch duty cycle determination module first sets the duty cycle of the MOSFET switch to d1. Additionally, the duty cycle of the diode is defined as d2. Based on the value V of v at t equal to 0 cb , the output current I cb0 , and the switching period T o , the duty cycles d1 and d2 are determined, which are expressed by formulas (1) and (2): sw_a

[0050]

[0051]

[0052] In the fourth step, the MOSFET switch conduction loss determination module determines the MOSFET switch conduction loss

[0053] The MOSFET switch conduction loss determination module determines the MOSFET switch conduction loss based on the on-resistance R of the MOSFET switch dson , the output power P of the circuit o , the inductor L a , the switching frequency f sw_a , the output voltage V of the circuit o , the energy storage capacitor C b , the maximum value V and the minimum value V of the voltage across both ends cbmax and cbmin , which is expressed by formula (3):

[0054]

[0055] In the fifth step, the MOSFET switch loss analysis module analyzes the loss during the MOSFET switch switching process

[0056] ​The MOSFET switching loss analysis module first analyzes the circuit characteristics and finds that the buck-boost auxiliary circuit operates in discontinuous current mode, so the MOSFET switch can achieve zero current turn-on and zero turn-on loss. The MOSFET switch tube in the buck-boost auxiliary circuit is hard-off. During the turn-off process, the turn-off voltage and current waveforms will overlap, resulting in turn-off loss. According to the turn-off time t of the MOSFET device itself, off , duty cycle d1, energy storage capacitor C b Voltage v cb The value V at time t equals 0 cb0 , determine the MOSFET switching loss, that is, the MOSFET turn-off loss, expressed by formula (4):

[0057]

[0058] Step 6: The diode loss analysis module analyzes the loss generated by the diode. When the diode in the buck-boost auxiliary circuit in the diode loss analysis module is turned on, the on-resistance will generate conduction loss. According to the diode forward voltage V F , and the power supply output current I o , determine the diode loss, expressed as formula (5):

[0059]

[0060] Step 7: The inductor loss analysis module analyzes the loss introduced by the inductor

[0061] The inductor loss in the circuit of the inductor loss analysis module is mainly copper loss. According to the DC resistance R of the inductor coil typ The equivalent resistance R on the line, the duty cycle d1 and d2, determine the inductor loss, which is expressed by formula (6):

[0062]

[0063] Step 8: Auxiliary circuit total loss analysis module analyzes the factors affecting the circuit loss

[0064] The auxiliary circuit total loss analysis module determines the total loss of the buck-boost auxiliary circuit based on the determined MOSFET conduction loss, MOSFET turn-off loss, diode loss, and inductor loss, which is expressed as formula (7). b The average voltage V cb0 About V cb0 The larger the voltage value, the smaller the loss of the buck-boost auxiliary circuit, and the higher the overall efficiency of the system.

[0065] P loss_total =P loss_on_avg +P loss_close_avg+P loss_diode_avg +P loss_La_avg (7)

[0066] So far, the establishment of the loss analysis model of the LED driving power supply with the buck-boost type auxiliary circuit and the analysis of the loss influence are completed.

Claims

1. A method for analyzing power loss of LED driver with buck-boost auxiliary circuit, characterized in that The specific steps are: The first step is to build an LED driver power loss analysis system with a buck-boost auxiliary circuit. An LED driver power supply loss analysis system with a buck-boost auxiliary circuit includes: a MOSFET switch modal analysis module, a MOSFET switch duty cycle determination module, a MOSFET switch conduction loss determination module, a MOSFET switch turn-off loss analysis module, a diode loss analysis module, an inductor loss analysis module, and an auxiliary circuit total loss analysis module; The second step is to use the MOSFET switch mode analysis module to analyze the circuit working status. The MOSFET switch modal analysis module analyzes the circuit state according to the state of the MOSFET switch at different times; the MOSFET switch is set to be turned on with a duty cycle of d1 and a conduction time of [t1, t2], and the ripple isolation capacitor C a and energy storage capacitor C b The MOSFET is turned off at time t2, and in the period [t2, t3], the output current of the buck-boost auxiliary circuit is fed to the ripple isolation capacitor C a Charging, ripple isolation capacitor voltage v ca Rising, the energy storage capacitor voltage v cb Drop; inductance L a The current becomes zero at time t3; in the period [t3, t4], v ca and v cb decline; The third step is to determine the MOSFET switch duty cycle by the MOSFET switch duty cycle determination module. The MOSFET switch duty cycle determination module first sets the MOSFET switch duty cycle to d1. In addition, the duty cycle of the diode is defined as d2. cb The value V at time t equals 0 cb0 , output current I o , and the switching period T sw_a , determine the duty cycles d1 and d2, expressed by formula (1) and formula (2): Step 4: MOSFET switch conduction loss determination module determines the MOSFET switch conduction loss The MOSFET switch conduction loss determination module is based on the on-resistance R dson , circuit output power P o , inductance L a , switching frequency f sw_a , the circuit output voltage V o , energy storage capacitor C b The maximum voltage across the terminals V cbmax and minimum value V cbmin , determine the conduction loss of the MOSFET switch, expressed by formula (3): Step 5: MOSFET switch turn-off loss analysis module analyzes the loss during MOSFET switch switching. The MOSFET switch turn-off loss analysis module first analyzes the circuit characteristics and finds that the buck-boost auxiliary circuit operates in the discontinuous current mode. Therefore, the MOSFET switch can achieve zero current turn-on and zero turn-on loss. The MOSFET switch tube in the buck-boost auxiliary circuit is hard turned off. During the turn-off process, the turn-off voltage and current waveforms will overlap, resulting in turn-off loss. According to the turn-off time t of the MOSFET device itself, off , duty cycle d1, energy storage capacitor C b Voltage v cb The value V at time t equals 0 cb0 , determine the MOSFET switching loss, that is, the MOSFET turn-off loss, expressed by formula (4): Step 6: The diode loss analysis module analyzes the loss generated by the diode. When the diode in the buck-boost auxiliary circuit in the diode loss analysis module is turned on, the on-resistance will produce conduction loss; according to the diode forward conduction voltage V F , and the power supply output current I o , determine the diode loss, expressed as formula (5): Step 7: The inductor loss analysis module analyzes the loss introduced by the inductor The inductor loss in the circuit of the inductor loss analysis module is mainly copper loss; according to the DC resistance R of the inductor coil typ The equivalent resistance R on the line, the duty cycle d1 and d2, determine the inductor loss, which is expressed by formula (6): Step 8: Auxiliary circuit total loss analysis module analyzes the factors affecting the circuit loss The auxiliary circuit total loss analysis module determines the total loss of the buck-boost auxiliary circuit based on the determined MOSFET conduction loss, MOSFET turn-off loss, diode loss, and inductor loss, which is expressed by formula (7); the loss of the buck-boost auxiliary circuit is determined to be proportional to the C b The average voltage V cb0 About V cb0 The larger the voltage value, the smaller the loss of the buck-boost auxiliary circuit, and the higher the overall efficiency of the system; P loss_total =P loss_on_avg +P loss_close_avg +P loss_diode_avg +P loss_La_avg (7) At this point, the establishment of the LED driver power supply loss analysis model and loss impact analysis containing a buck-boost auxiliary circuit are completed.

2. The method for analyzing power loss of an LED driver with a buck-boost auxiliary circuit according to claim 1, characterized in that The function of the MOSFET switch mode analysis module is to analyze the three working states of the buck-boost auxiliary circuit, the current changes under each working mode, and the parameter change trends of the energy storage capacitor voltage and the ripple isolation capacitor voltage.

3. The method for analyzing power loss of an LED driver with a buck-boost auxiliary circuit according to claim 1, characterized in that The function of the MOSFET switch duty cycle determination module is to determine the duty cycle d1 of the MOSFET switch tube and the duty cycle d2 of the diode according to the input and output current characteristics of the auxiliary circuit.

4. The method for analyzing power loss of an LED driver with a buck-boost auxiliary circuit according to claim 1, characterized in that The function of the MOSFET switch conduction loss determination module is to: dson The characteristics of the circuit and the change characteristics of the circuit input current are used to determine the conduction loss of the MOSFET switch tube.

5. The method for analyzing power loss of an LED driver with a buck-boost auxiliary circuit according to claim 1, characterized in that The function of the MOSFET switch turn-off loss analysis module is to analyze only the MOSFET turn-off loss according to the characteristics of the auxiliary circuit operating in the current discontinuous mode, and determine the MOSFET switch loss according to the turn-off characteristics of the MOSFET device and the average value of the energy storage capacitor voltage.

6. The method for analyzing power loss of an LED driver including a buck-boost auxiliary circuit according to claim 1, characterized in that The function of the diode loss analysis module is to determine the diode loss based on the diode forward voltage characteristics and the auxiliary circuit output current characteristics.

7. The method for analyzing power loss of an LED driver with a buck-boost auxiliary circuit according to claim 1, characterized in that The function of the inductor loss analysis module is to determine the copper loss of the inductor coil according to the DC resistance Rtyp of the inductor coil, the equivalent resistance R on the circuit, and the output current characteristics.

8. The method for analyzing power loss of an LED driver including a buck-boost auxiliary circuit according to claim 1, characterized in that The function of the auxiliary circuit total loss analysis module is to determine the matching energy storage capacitor voltage average value V according to the loss contained in the buck-boost auxiliary circuit. cb0 , optimize the overall efficiency of the power supply as the basis for parameter selection.

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