Home air conditioner power supply solution based on gate drive and operational amplifier

As a high-performance analog and mixed-analog chip supplier, Biyiwei provides one-stop overall solutions. This time, we bring you a home air conditioning power supply solution. As the hot summer is approaching, we remind everyone to cool down and prevent heatstroke.

Air conditioners are also called "heat pumps". As the name suggests, they pump heat. The working principle of air conditioners for cooling and heating is to move heat back and forth using refrigerants as carriers. When cooling, the refrigerant absorbs heat from indoors and moves it to outdoors, lowering the indoor temperature; when heating, the refrigerant absorbs heat from outdoors and moves it to indoors, raising the indoor temperature. In layman's terms, air conditioners are just heat carriers. The compressor, expansion valve, condenser, evaporator, fan, etc. are the core components of air conditioners for transporting heat, and they require a complex and reliable power system to support them.

Figure 1. Application block diagram of indoor unit of household air conditioner

Figure 2. Application block diagram of household air conditioner outdoor unit

The above two figures show the system block diagram of the indoor and outdoor units of a household air conditioner. Among them, the AC-DC conversion, DC-DC conversion, gate drive, and operational amplifier solutions provided by Biyiwei can help build a robust air conditioner power system.

AC-DC Solutions

Scenario 1

Flyback Solution

KP3667X is a series of SSR power switch tubes with integrated 700V high-voltage MOS, including KP36673, KP36674 and KP36675. It has a built-in 700V high-voltage startup JFET, which can save startup resistance, reduce startup delay and standby power consumption; it has a high-precision 132kHz switching frequency oscillator with frequency jitter function to optimize EMI; and it integrates complete protection functions.

KP3637X is a series of SSR power switch tubes with integrated 700V high-voltage MOS and Line OVP/BOP functions, including KP36373 and KP36374. The Line OVP/BOP function allows the power supply to shut down for protection when the input voltage is abnormal, thereby increasing the reliability of the power supply; the Line OVP/BOP function of KP3637X can meet both DC input and AC input configurations.

Scenario 2

Non-isolated solution

KP32652 is a non-isolated power switch tube with fixed 15V output, supporting Buck and Buck-Boost topologies. KP32652 integrates feedback resistors, which can solve the problem of unstable output caused by external feedback resistors in traditional solutions.

Table 1. AC-DC solution selection table

DC-DC Solutions

The air conditioner circuit board space is very compact, and the strong and weak currents are cross-layout, which places special demands on the DC-DC function. KP522302E is a third-generation solution specially designed for white goods applications:

Advantage 1

Excellent EMC performance

Fixed 500kHz operating frequency, taking into account efficiency, EMC and Bom cost.

Specially modulated MOS turn-on slew rate and turn-off slew rate greatly reduce the radiation energy of DC-DC.

The frequency jitter function is added, and the operating frequency changes smoothly from 94%Fsw to 106%Fsw, thereby reducing the peak radiation energy of the electric field and leakage magnetic field at the multiple operating frequency points. White appliance applications are sensitive to cost, so customers generally choose cost-effective I-shaped non-shielded inductors or ordinary chip non-shielded inductors. Due to the limitation of the internal space of the air conditioner, the DC-DC inductor is close to the 220VAC strong power harness, which causes the DC-DC electric field radiation and the inductor leakage magnetic field radiation to be directly coupled to the 220VAC power line, so that the conduction at the multiple operating frequency points of the DC-DC cannot meet the test requirements. The frequency jitter function can effectively solve this problem. The effect can be clearly seen through the oscilloscope FFT analysis, such as the peak energy at the one-time frequency point is reduced by 52%, and the three-time frequency point is reduced by 55%.

Figure 3. FFT test comparison

Advantage 2

Super strong anti-interference ability

Peak current mode control method, strong anti-interference ability, ultra-fast input voltage regulation rate, very easy to pass surge and pulse group tests.

Since the air conditioner compressor has a large power, the start and stop of the compressor can easily cause high-frequency surge or overshoot voltage signals at the DC-DC input. The good voltage regulation rate of KP522302E ensures precise output voltage control and improves system reliability.

Figure 4. 2A load, 12VIN——>15VIN, SR = 50V/ms

Figure 5. 2A load, 15VIN——>12VIN, SR = 50V/ms

Advantage 3

VIN UVLO Function

The DC-DC in air conditioners is generally used for 12V to 5V conversion, and the minimum operating voltage of DC-DC can generally support about 4.5V. The EN leg of KP522302E has a built-in 500mV reference with hysteresis function. The VIN rising threshold and falling threshold can be set through external voltage divider resistors to avoid system lock, reset or screen flicker caused by slow power-on or power-off.

Figure 6. VIN UVLO threshold setting

Advantage 4

Full compatibility solution

SOT23-6 package, very friendly to single-sided PCB, provides 17V medium voltage, 30V and 36V high voltage full set of compatible solutions.

Advantage 5

High conversion efficiency

With a built-in 72mΩ upper MOS and 35mΩ lower MOS, the peak efficiency of 12V to 5V can reach 94%. In addition, two mode chips, PFM and FPWM, are provided. The PFM version has an efficiency of 90% at 10mA, which can further help air conditioners improve energy efficiency.

Figure 7. KP522302E efficiency curve

(VOUT = 5V, L1 = 8.2µH, DCR = 60mΩ)

Table 2. DC-DC solution selection table

Gate drive scheme

Scenario 1

Gate Driver

KP8563X is a 650V withstand voltage, 200mA/350mA source current/sink current three-phase half-bridge gate driver designed specifically for driving MOSFET and IGBT. The switch node negative voltage can reach more than -7V and the voltage change rate is at least 50V/ns, and the system has strong anti-interference ability. The chip also integrates undervoltage lockout, overcurrent protection with automatic fault clearing function, fault indication and enable function. The undervoltage lockout protection function prevents the power tube from working at too low a voltage. The overcurrent protection threshold can be adjusted by external resistors, and the system peripheral circuit is simple. The open-drain fault output signal can provide an indication signal when an overcurrent or undervoltage shutdown occurs. The integrated enable function can control whether the chip works or not.

KP8530X is a 650V withstand voltage, half-bridge gate driver with integrated bootstrap diode, with 0.3A source current and 0.6A sink current capability, dedicated to driving power MOSFETs or IGBTs. KP8530X has good current output and excellent transient interference resistance, which can ensure the normal operation of the system when the input logic pin is -5V and the switch node VS is -7V. It can support dv/dt changes of at least 50V/ns. It also has complete protection functions, including: when the input is floating or the input pulse width is insufficient, the output remains at a low level. Built-in interlock and dead zone protection functions can prevent the high and low side drivers from turning on at the same time, and the chip has high and low side UVLO protection.

Table 3. Gate Driver Selection Table

Scenario 2

Low-side gate driver

KP85751 is a 25V withstand voltage, 2 channels, 5A current drive capability low-side gate driver chip, up to 5A of sink and sink current capability can speed up the switching speed of power devices, reduce switching losses, and improve system efficiency. At the same time, the chip supports 25V power supply voltage, improves the robustness of the system, and good channel propagation delay and matching provide high reliability design for strict industrial and large home appliance applications.

Table 4. Low-side gate driver selection table

Motor drive solution

Scenario 1

Stepper Motor Driver

KP83130 is a dual H-bridge motor driver chip with 1.5A peak drive current and 0.8A continuous current capability, which can control the motor to enter forward, reverse, brake, coast and low-power sleep modes. The chip integrates undervoltage protection, overtemperature protection, output short circuit protection and other functions.

Table 5. Stepper Motor Driver Selection Table

Summarize

At present, the domestic substitution of air-conditioning IC components has entered the deep water zone. With the company philosophy of "unique innovation and easy to use", Biyiwei provides the air-conditioning market with a one-stop overall solution with high cost performance and high reliability.