Repairing DAKIN air conditioner - Study about 300VDC boost voltage circuit OPV1 OPV2 and troubleshooting errors in DAIKIN circuit
Hello, welcome back to authelectronic.com ! today we will help you understand how OPV1 OPV2 circuits work in a DAIKIN air conditioner circuit. Also we will help you to troubleshooting some common errors in DAIKIN air conditioners.
We take a DAIKIN GAS410 air conditioner circuit to study today. this is a heating and cooling DAIKIN air conditioner circuit version.
The principle working of DAIKIN air conditioner
220VAC input voltage goes through fuse, then right after the fuse We have a VZ1 varistor to protect the circuit in a case of over input voltage. Using C1 capacitor, L1 coil, C2 capacitor to filter input high frequency noise. Then 220v AC input voltage will be divided in 2 lines. The first 200 VAC voltage line goes through fuse to bridge rectifier DB3 , It creates 300VDC output voltage, then using C2 capacitor to make this 300VDC voltage be flatter. then this 300VDC goes into pulse power supply circuit to generate 5VDC output voltage, 12VDC output voltage, 15VDC output voltage. 5VDC is used for MCU, sensors. 12VDC is used for relays, other ICs, 15VDC is used for IMP (Intelligent module power). If you don't understand clearly pulse power supply circuit, please read the article we put the link below, you will understand more.
Look at the second 220VAC line. We know that 5VDC from pulse power supply circuit is used for MCU. Then MCU makes MRN20 relay close the circuit, and the second 220VAC line can go through RT thermistor, MRN20 relay contact, coil and to BD1 rectifier. We also have another BD2 rectifier, after BD2 and BD1 rectifier it has a 300VDC output voltage, using C94 ,C74, C75 capacitors to make this 300VDC flatter.
this 300vdc output is used for IPM. So to protect IPM , we use OPV1 and OPV2 circuit. But before ipm works, the MCU must check some conditions of sensors, IPM fault pin,opv1,opv2,.etc. If all the conditions are ok, MCU will make MRM10 relay close circuit then all the main power current flow to MRM10 relay contact to BD1 rectifier to IPM.That will be enough power for IPM to work
How do OPV1 and OPV2 circuit work with MCU in DAIKIN air conditioner.
How does OPV1 work with MCU?
At 300 VDC output voltage line, we have a voltage divider circuit using R58 R63 R93 resistors. Output voltage of R95 resistor goes to OSI5 opto. OSI5 opto is connected to C pin of Q10 transistor. The voltage of C75 capacitor (usually 150VDC) is divided by using R64 R69 R94 resistors. The voltage of R94 resistor goes to OIS6 opto, then connect to pin C of Q11 transistor.That is OPV1 circuit.
What is normal condition of OPV1 circuit?
When the OPV1 condition is ok, we measure voltage of Vmcu is 5VDC. if The condition of OPV2 is ok too, the MCU will make MRM10 relay contact close and all the current goes through MRM10 relay to IPM. IPM will start motor of air conditioner.
What is normal condition of OPV2 circuit?
From IPM, using voltage divider circuit. The voltage of R119 resistor goes to MCU. if this voltage is 3.5VDC, that means MCU understands the condition is ok, if the voltage is upper or lower than (3.5 +-alpha)VDC, the MCU understands the condition is not ok, that means the input volatge of IPM is upper or lower than 300VDC. The MCU wont let the contact of MRM10 relay close and current flow cannot enought make IPM work.
The popular errors in DAIKIN circuit that make DAIKIN air conditioner doesn't start motor
Case 1: the 300VDC voltage increasing, volatge of C75 capacitor is not 150VDC
When the 300VDC voltage increases, the voltage of R93 resistor also increases, so that makes OIS5 opto work then Vmcu is 0VDC, MUC understant that there is a error of 300VDC. Also with OIS6 opto is same too. When 300VDC increases, the voltage of C75 capacitor increases too, then volatage of R94 increases too, that makes OIS6 opto work , then Vmcu is 0VDC.
Case 2: Capacitor 150VDC, Mmcu 0VDC
Look at R74 R175 R80 resistors, it is a voltage divider circuit. When 300VDC increases, the voltage of R80 resistor also increases too. So if this R80 voltage makes zenner diode Z09 open, that makes IOS5 opto work, then voltage Vmcu decreases to 0 VDC. MCU can not let IPM start motor.
R176 R176 R81 is the same too, when voltage of C75 capacitor increases, the voltage of R81 resistor also increases, this R81 voltage is high enough to open ZD10 zener diode, then OIS6 opto works, then voltage Vmcu down to 0VDC. MCU understands that 300vdc increasing error.
Case 3: electronic components in circuit are broken
If 300VDC is OK, Voltage C75 capacitor is 150VDC but Voltage Vmcu still be 0VDC, there are some cases can happen.
case1: R80 resistor is broken or value of R80 resistor increasing, that makes voltage R80 increase too, so Z09 zener diode opens, then Q10 transistor opens, OIS5 works, Vmcu down to 0VDC
case 2: R146 resistor is broken, so Vmcu can not be 5VDC , so Vmcu will be always different from 5VDC.
Case 3: IOS 5 OIS 6 optos are broken, so Vmcu is always 0VDC..