CN218733345U

CN218733345U - Voltage-stabilizing charging circuit for built-in charger

Info

Publication number: CN218733345U
Application number: CN202222888739.3U
Authority: CN
Inventors: 姚晓武
Original assignee: Zhejiang Yaneng Energy Technology Co ltd
Current assignee: Zhejiang Yaneng Energy Technology Co ltd
Priority date: 2022-11-01
Filing date: 2022-11-01
Publication date: 2023-03-24
Anticipated expiration: 2032-11-01

Abstract

A voltage-stabilizing charging circuit for a built-in charger belongs to the technical field of direct current/direct current conversion. The utility model comprises a half-bridge LLC drive circuit, a half-bridge LLC resonance circuit, a PFC drive circuit and a PFC power circuit; in the half-bridge LLC driving circuit, a BLK pin of a control chip senses the output voltage level of a PFC power circuit; the FB pin senses LLC level control feedback input; the HV pin provides a starting power supply for PFC and LLC levels; the ISNS pin is used for measuring resonance current; the VCR pin is used for voltage induction of the resonant capacitor; the half-bridge LLC resonant circuit comprises two MOS tubes, a transformer and two resonant capacitors; in a control chip of the PFC driving circuit, a VM pin is used for adjusting the duty ratio; the CS pin is used for current detection; the BO pin is used for detecting voltage; the CTR pin is used for adjusting a loop inside the chip; the FB pin is used for detecting the VBUS bus voltage; the DRV pin is used for driving a MOS tube of the PFC power circuit. The utility model discloses a half-bridge mode has ensured output voltage's stability.

Description

Voltage-stabilizing charging circuit for built-in charger

Technical Field

The utility model relates to a direct current/direct current transform technical field especially relates to a steady voltage charging circuit for built-in machine that charges.

Background

Compared with the traditional series-parallel converter, the LLC half-bridge resonant type has obvious improvement and improvement on the characteristics thereof. The LLC half-bridge resonant converter has the advantages of simple topological structure, low heat generation, low switch turn-off loss and the like in the working process, and is very popular in industrial systems. Especially, the advantages of high stability, high efficiency, high conversion efficiency and the like occupy a large market share.

The core of the topology of the LLC half-bridge resonant converter is two inductors + one resonant capacitor. Its main function is to convert ac into dc. Because the LLC uses the soft switch, zero voltage switching-on can be achieved, so that the efficiency is high and the switching-on loss is small. And when the battery has low current, the dummy load is turned on, so that the conversion efficiency is improved. And the LLC driving chip UCC256304 driving chip is adopted, so that the conversion efficiency can be correspondingly improved.

The built-in charger is generally fixed in the vehicle and used as a part of the whole vehicle. Has the characteristics of long service time, complex disassembly and the like. Therefore, in order to ensure long-term stable use of the vehicle and the charger, the charger must have the characteristic of high protection. 48v series vehicle-mounted charger usually hardly accomplishes 600w, and the heat is more for the power is big. And when the battery is charged, the current is very low in the later period of charging. However, the light load (or no load) makes it difficult to stabilize the output voltage due to the limitations of the core element and the switching element at high frequency switching frequencies.

SUMMERY OF THE UTILITY MODEL

The utility model aims at solving the problem that above-mentioned prior art exists, provide a steady voltage charging circuit for built-in machine that charges, it has ensured output voltage's stability through the half-bridge mode.

The utility model aims at realizing through the following technical scheme:

a voltage-stabilizing charging circuit for a built-in charger comprises a half-bridge LLC driving circuit, a half-bridge LLC resonant circuit, a PFC driving circuit and a PFC power circuit;

in the half-bridge LLC driving circuit, a BLK pin of a control chip senses the output voltage level of the PFC power circuit; the FB pin senses LLC level control feedback input and is used for controlling LLC input power level; the HV pin provides a starting power supply for PFC and LLC levels; the ISNS pin is used for carrying out difference with a first-order filter and measuring resonant current; the VCR pin is used for voltage induction of the resonant capacitor;

the half-bridge LLC resonant circuit comprises two bridge arms formed by two MOS tubes, a transformer and two parallel resonant capacitors connected between the bridge arms and the transformer, wherein a resonant inductor and an excitation inductor are integrated in the transformer, and the two resonant capacitors, the resonant inductor and the excitation inductor form a resonant network;

in a control chip of the PFC driving circuit, a VM pin is used for adjusting a duty ratio; the CS pin is used for current detection; the BO pin is used for detecting voltage; the CTR pin is used for adjusting a loop inside the chip; the FB pin is used for detecting the voltage of a VBUS bus and controlling the opening and closing of the chip together with the BO pin; and the DRV pin is used for driving an MOS (metal oxide semiconductor) tube of the PFC power circuit.

As the utility model discloses preferably, half-bridge LLC drive circuit's control chip's BW pin sensing is through the output voltage of bias winding for provide output overvoltage protection.

As the utility model discloses preferably, half-bridge LLC drive circuit's control chip's LL/SS pin is used for controlling the duration of soft start cycle.

Preferably, the HB pin of the control chip of the half-bridge LLC driving circuit senses the high-side gate drive floating supply voltage, and a bootstrap capacitor is connected between the HB pin and the HS pin; the HS pin is used for high-side grid electrode driving current backflow; the HO pin senses the high side floating gate drive output; the LO pin is used for the low side gate drive output.

As the utility model discloses it is preferred, PFC drive circuit's control chip's VM pin comes the adjustment duty cycle through parallelly connected resistance and electric capacity.

As the utility model discloses preferably, PFC drive circuit's control chip's CTR pin adjusts the inside loop of chip through parallelly connected resistance and electric capacity.

As the utility model discloses it is preferred, the control chip that half-bridge LLC drive circuit adopted is UCC256304 chip.

Preferably, in the present invention, the control chip used in the PFC driving circuit is an NCP1654 chip.

The utility model has the advantages that: through the effective cooperation of half-bridge LLC circuit and PFC circuit, ensured charging circuit output voltage's stability.

Drawings

Fig. 1 is a schematic diagram of a half-bridge LLC driving circuit according to the present invention;

fig. 2 is a schematic diagram of a driving waveform of the MOS transistor in the LLC operating mode of the present invention;

fig. 3 is a schematic diagram of a topology of a middle half-bridge LLC resonant converter of the present invention;

fig. 4 is a control block diagram of the PFC controller;

fig. 5 is a schematic diagram of a portion of a PFC power circuit;

fig. 6 is a schematic diagram of driving waveforms of the PFC-driven MOS transistor.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

The utility model provides a steady voltage charging circuit for built-in machine that charges, including half-bridge LLC drive circuit, half-bridge LLC resonant circuit, PFC drive circuit, PFC power circuit, mainly can realize output voltage's stability through the half-bridge mode.

Specifically, as shown in fig. 1, a control chip adopted by the half-bridge LLC driving circuit is UCC256304, and a BLK pin of the chip is mainly used for sensing a PFC output voltage level. BW pin this pin is used to sense the output voltage across the bias winding, the sensed voltage being used to provide output overvoltage protection. The FB pin is used to sense the LLC stage control feedback input, and the magnitude of the current from this pin will determine the LLC input power level. The HB pin is used for sensing the high side gate drive floating supply voltage and a bootstrap capacitor needs to be connected between the HB pin and the HS pin. The HO pin is used to sense the high side floating gate drive output. The HS pin is primarily used to sense the high side gate drive current return. The HV pin provides the starting power for the PFC and LLC stages. The ISNS pin is mainly used for carrying out difference with a first-order filter and measuring resonant current. The LL/SS pin peripheral circuitry will primarily determine the duration of the soft start period. The LO pin is used for low side gate drive output. The VCR pin is used for resonant capacitor voltage sensing.

In UCC256304, in order to adapt the LLC controller to a very wide dc input voltage range, while still keeping the proper BLK off, a proper over-voltage trigger value needs to be set. Taking a starting threshold of 120V as an example, the following formula can be used for calculation:

for the same BLK resistor voltage division ratio, the constant voltage turn-off voltage is:

constant voltage greater than or equal to V _OVRise The overvoltage protection is triggered:

this wide dc input range brings many system-level advantages. When the UCC256304 is paired with a PFC stage, the LLC converter can start up and enter a low power consumption standby mode without enabling PFC. In addition, the wide dc input range enables ac/dc systems to be compatible with a wide range of universal ac inputs.

Prior to design, LLC power level component values are first determined. A complete explanation of the source of each equation used. The following equation is based on a commonly used method when analyzing LLC topology:

firstly, LLC gain is calculated, the transformer turn ratio can be determined by using nominal input and output voltages, then LLC gain range M is determined _g(min) And M _g(max) . Hypothetical diodeWait for other losses V _loss And further the pressure is reduced by 0.5V.

The nominal switching frequency (resonant frequency) should be selected before the resonant tank component parameters are determined. In this design, 100kHz was chosen as the resonant frequency. The resonant tank parameters are calculated as follows:

after selecting the preliminary parameters, the closest actual component values available are found, the gain curve is again verified using the selected parameters, and then a time domain simulation is run to verify circuit operation.

The following resonant tank parameters were:

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based on the final resonant tank parameters, the resonant frequency can be calculated:

then it can be concluded that the maximum and minimum switching frequencies are:

this also operates at high frequency when fully loaded. Otherwise, the converter only runs at high frequency when in light load, the current flowing through the half-bridge MOS tube is lower, so that the rise of the on-resistance is not generally a problem, and the voltage drop of the bootstrap circuit can be calculated by the formula:

wherein Q is _g Is the charge of an external power MOS, R _（DS）ON Is the on-resistance (typically 150 ohms) of the bootstrap MOS, T _charge Is the turn-on time of the bootstrap drive plus the dead time Td during the half-bridge switching. D214 is an ultrafast recovery diode for compensating the conduction voltage drop of the internal MOS transistor. LLC drives the waveform diagram of MOS pipe, as shown in figure 2.

Shown in fig. 3 is a half bridge LLC resonant circuit, wherein: MOS tubes Q203 and Q208 form two bridge arms of the half-bridge converter, lr is a resonant inductor, lm is an exciting inductor, the two bridge arms are integrated in the transformer T200, and C220 and C207 are resonant capacitors Cr. Cr, lr and Lm form a resonant network of the half-bridge LLC resonant converter. The specific working principle is as follows:

the first stage is as follows: q203 is conducted, Q208 is cut off, an input power Vin charges a resonant capacitor C219 through a resonant inductor Lr, and the voltage of the capacitor C219 rises; at the same time the C205 capacitor discharges and the C205 capacitor voltage drops.

And a second stage: q203 is off and Q208 is off. Because the resonant inductor current cannot change suddenly, the Lr current is still positive and only gradually decreases, the C219 charging current also gradually decreases, the C219 voltage still increases, and the C205 capacitor is still in a discharge state. At this time, the body diode of the Q208 tube is turned on, and the forward conduction voltage is small, so that a condition for realizing ZVS (zero voltage switching) of the Q208 is provided.

And a third stage: q208 is off and Q208 is on. With the Q208 diode conducting before, the Q208 achieves ZVS (zero voltage switching) after the dead time. At this time, the resonant capacitor C219 is equivalent to a voltage source, and resonates with the resonant inductor Lr by being positive up and negative down. The Lr current gradually increases in opposite phase after decreasing to zero. The C219 capacitance is in the discharged state, so the C208 capacitance is in the charge.

As shown in fig. 4, the PFC driving circuit employs a NCP1654 as a control chip, in which: the VM pin adjusts the duty cycle through resistor R234 and capacitor C215. The resistor R222 is mainly used for current detection, and is connected to the CS pin of the chip for overcurrent determination. The BO pin of the chip detects the voltage and is used for judging whether the inside of the chip is opened or closed. The resistor R236 and the capacitor C214 are connected to the CTR pin of the chip and are used for adjusting the loop inside the chip. The FB pin of the chip is used for detecting the VBUS bus voltage, is used for controlling the on or off of the chip like the BO pin, and the chip is only started to work after the two pins meet the conditions. The DRV pin of the chip is mainly used as a MOS transistor for driving the PFC, and fig. 5 shows a power portion of the PFC, and waveforms of the driving MOS transistor are shown in fig. 6.

Tests show that when the input voltage is 176v and the output voltage is 53.5v with full load, the efficiency value is 92.67%; when the input voltage is 220v and the output voltage is 53.5v with full load, the efficiency value is 93.19%; at an input voltage of 250v and an output voltage of 53.5v at full belt load, the efficiency value is 93.26%.

The above, only the preferred embodiment of the present invention is an implementation manner based on the whole concept of the present invention, and the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A voltage-stabilizing charging circuit for a built-in charger is characterized by comprising a half-bridge LLC driving circuit, a half-bridge LLC resonant circuit, a PFC driving circuit and a PFC power circuit;

in the half-bridge LLC driving circuit, a BLK pin of a control chip senses the output voltage level of the PFC power circuit; the FB pin senses an LLC level control feedback input and is used for controlling an LLC input power level; the HV pin provides a starting power supply for PFC and LLC levels; the ISNS pin is used for carrying out difference with a first-order filter and measuring resonant current; the VCR pin is used for voltage induction of the resonant capacitor;

2. The regulated charging circuit for an internal charger according to claim 1, wherein a BW pin of a control chip of the half-bridge LLC driving circuit senses an output voltage across the bias winding for providing output overvoltage protection.

3. The regulated charging circuit for an internal charger according to claim 1, wherein the LL/SS pin of the control chip of the half-bridge LLC driving circuit is used to control the duration of the soft-start period.

4. The voltage-stabilizing charging circuit for the built-in charger according to claim 1, wherein a HB pin of a control chip of the half-bridge LLC driving circuit senses a high-side gate-driven floating power supply voltage, and a bootstrap capacitor is connected between the HB pin and the HS pin; the HS pin is used for high-side gate drive current backflow; the HO pin senses the high side floating gate drive output; the LO pin is used for the low side gate drive output.

5. The voltage-stabilizing charging circuit for the built-in charger according to claim 1, wherein a VM pin of a control chip of the PFC driving circuit adjusts a duty ratio through a resistor and a capacitor connected in parallel.

6. The voltage-stabilizing charging circuit for the built-in charger according to claim 1, wherein a CTR pin of a control chip of the PFC driving circuit adjusts a loop inside the chip through a resistor and a capacitor connected in parallel.

7. The voltage-stabilizing charging circuit for the built-in charger according to claim 1, wherein a control chip adopted by the half-bridge LLC driving circuit is a UCC256304 chip.

8. The voltage-stabilizing charging circuit for the built-in charger according to claim 1, wherein a control chip adopted by the PFC driving circuit is an NCP1654 chip.