The main features and internal structure principles of intelligent power module IPM

IPM is a hybrid integrated circuit that integrates high-power switching elements and drive circuits, protection circuits, detection circuits, etc. in the same module. This power integrated circuit is particularly suitable for the needs of the inverter's high-frequency development direction. Its product appearance and internal structure are shown in Figure 1-15.

Figure 1-15 Intelligent power module and its internal structure

At present, IPM generally uses IGBT as the basic power switching element to form a dedicated functional module for single-phase or three-phase inverters, and is widely used in small and medium-capacity inverters.

In addition to being widely used in industrial inverters, economical IPM has also begun to be used in some civilian products such as household air-conditioning inverters, refrigerator inverters, and washing machine inverters in recent years.

The main features and internal structure principles of the commonly used intelligent power modules (IPMs) for frequency converters

The intelligent power module integrates the power switch and the drive circuit together, and is also equipped with overvoltage, overcurrent, overheating and other fault detection circuits, and sends the detection signal to the CPU. It has the advantages of small size, multiple functions, low power consumption, and easy use, and is widely used in general inverters.

IPM is a highly integrated intelligent power integrated circuit that integrates the main switch device, freewheeling diode, drive circuit, overcurrent protection circuit, overheat protection circuit, short circuit protection circuit, drive power shortage protection circuit, interface circuit, etc. in the same package.

Main features of IPM

1. Driving circuit

A high-performance drive circuit is set up inside the IPM, which has the function of automatically soft-shutdown the IGBT after a fault occurs. At the same time, due to the compact structure, the distance between the drive circuit and the IGBT is extremely short, the anti-interference ability is strong, and the output impedance is very low. There is no need to add a reverse bias voltage, which simplifies the drive circuit power supply. Only one set of common power supply for the lower bridge arm and three sets of independent "floating" power supplies for the upper bridge arms are required.

2. Undervoltage protection

Each drive circuit has an undervoltage (UV) protection function. No matter what the reason, as long as the drive circuit power supply voltage Ucc is lower than the undervoltage threshold Uuv for more than 10ms, the IPM will shut down and output a fault alarm signal.

3. Overheat protection

There is a temperature sensor on the insulating substrate inside the IPM. When the temperature exceeds the overheating disconnection threshold, the protection circuit inside the IPM will block the gate drive signal and will not accept the control input signal until the overheating disappears, protecting the device from damage and outputting an overheating fault signal. When the temperature drops to the overheating reset threshold, the circuit automatically resumes normal operation.

4. Overcurrent and short circuit protection

The IGBT current sensor in the IPM is of emitter shunt type. The current flowing through the sampling resistor is very small, but it is proportional to the current flowing through the switch device, thus replacing current monitoring components such as high-power resistors, current transformers, and Hall current sensors. If the C-pole current of any IGBT in the IPM is greater than the overcurrent action current for 10μs, the IPM will be soft-shut down and output an overcurrent alarm signal.

5. Braking circuit

The IPM is provided with a braking circuit composed of IGBTs. When the IPM receives a braking signal, the IGBTs in the braking circuit are turned on, the braking resistor connected to the braking terminal BN absorbs electrical energy, and the braking circuit works.

6. Easy to use

IPM adopts ceramic insulation structure and is directly installed on the insulation board. The DC input (P, N), brake unit output (B) and inverter output terminals are directly connected with screws; the input and output control terminals are arranged in a row and can be connected with a universal socket. Therefore, the main terminal and the control terminal terminal can be directly disassembled without soldering iron, which is very convenient.

The basic structure and principles of IPM

1. Basic internal structure and principle of IPM

Figure 1 Basic structural principle diagram of IPM

As shown in Figure 1: UV in the figure is the undervoltage protection unit, OC is the overcurrent protection unit, SC is the short circuit protection unit, and OT is the overheating protection unit. The output signals of these protection units are used as the input signals of the OR gate. As long as one of the four protection units fails, the IPM will output a fault signal. Drive in the figure is the drive amplifier unit. It can be seen from the figure that the drive amplifier unit amplifies and outputs the received control signal to drive the IGBT control pole; at the same time, it can receive the signal of any fault protection circuit. Once the signal of the fault protection circuit is received, it outputs a soft shutdown drive signal to softly shut down the IGBT, so that the IGBT is protected.

2. IPM internal structure principle

Figure 2 Schematic diagram of the internal structure of IPM

As shown in Figure 2, IGBT1~IGBT6 form an inverter bridge, and VDF1~VDF6 are the freewheeling diodes of the six IGBTs. Among them, IGBT1~IGBT3 are upper bridge arm switching devices, and three groups of control circuits are powered by three separate "floating" DC power supplies; IGBT4~IGBT6 are lower bridge arm switching devices, and three groups of control circuits are powered by one group of DC power supplies; IGBT7 is a brake circuit switching device, and VDW is its freewheeling diode, which has gate drive control, fault detection and multiple protection circuits inside. If the internal fault protection circuit detects any of the overcurrent, undervoltage, overheating and short circuit faults, the IPM will automatically shut down softly and send out a fault alarm signal at the same time.

IPM terminal symbols and meanings

UinU: upper bridge arm U phase control signal input terminal;

UccU: ​​Upper bridge arm U phase drive power input terminal, UccU is the "+" terminal, GND U is the "-" terminal;

UinV: upper bridge arm V phase control signal input terminal;

UccV: Upper bridge arm V phase drive power input terminal, UccV is the "+" terminal, GND V is the "-" terminal;

UinW: upper bridge arm W phase control signal input terminal;

UccW: Upper bridge arm W phase drive power input terminal, UccW is the "+" terminal, GND W is the "-" terminal;

Ucc: The lower bridge arm shares the driving power supply (Ucc) input terminal, Ucc is the "+" terminal, and GND is the "-" terminal;

UinDB: brake control signal input terminal;

UinX: lower bridge arm X phase control signal input terminal;

UinY: lower bridge arm Y phase control signal input terminal;

UinZ: lower bridge arm Z phase control signal input terminal;

ALM: Output terminal when the protection circuit is in action;

P, N: The input terminal of the main power supply (Ud) after the frequency converter is rectified and smoothed, P is the "+" terminal, and N is the "-" terminal;

B: Braking output terminal, which can release regenerative electric energy during deceleration;

U, V, W: three-phase output terminals of the inverter.