InnoSwitch3-AQ INN3977CQ：高效汽车反激式开关电源IC

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"InnoSwitch3-AQ INN3977CQ 是一款专用于汽车应用的反激式开关电源集成电路，集成了750V MOSFET和FluxLink反馈技术，具备高效率、紧凑封装、环保节能及多种保护功能。" InnoSwitch3-AQ INN3977CQ 是Power Integrations公司推出的一款高性能反激式开关电源集成电路，设计适用于汽车电子系统。这款芯片在全负载范围内能实现高达90%的效率，显著提高了电源转换的能效。它将准谐振（Quasi-Resonant, QR）/连续电流模式（Continuous Conduction Mode, CCM）反激控制器、750伏的MOSFET以及次级侧感应技术集成在一个紧凑的封装内，减少了外部组件的需求，从而减小了整体电路板空间。 InnoSwitch3-AQ INN3977CQ 的一大创新是采用了集成的FluxLink技术，这是一种高压隔离的反馈链路，确保了电源的安全性和可靠性。这种技术使得主次侧间的通信无需光耦，增强了系统的稳定性和精度。此外，该芯片支持宽输入电压范围，从30VDC到550VDC，甚至通过StackFET可以扩展至921VDC，适应各种汽车电源环境。该产品已通过AEC-Q100认证，表明其符合汽车电子行业的高质量标准。生产过程中的晶圆厂、组装厂和测试站点均获得了IATF16949认证，确保了制造过程的品质与一致性。InnoSwitch3-AQ INN3977CQ 还包含了EcoSmart™技术，无负载功耗低于15毫瓦，有助于满足全球能源效率法规，同时低热耗散特性降低了系统的冷却需求。在安全保护方面，InnoSwitch3-AQ INN3977CQ 提供了自动重启动的输出过电压保护，并可选配输出欠压保护以及峰值功率传递功能。此外，它具有强化隔离，隔离电压超过4000VAC，确保了电气安全。100%的生产hipot测试进一步增强了产品的安全性。该芯片还符合多项安全和法规标准，如UL1577，确保了在汽车环境中的合规性。 InnoSwitch3-AQ INN3977CQ 是一款集高效、紧凑、安全和智能化于一体的反激式开关电源解决方案，尤其适合于对能效和可靠性的要求极高的汽车电子应用。

Rev. B 04/20

InnoSwitch3-AQ

www.power.com

The most likely event that could require an additional handshake is

when the primary stops switching as the result of a momentary line

brown-out event. When the primary resumes operation, it will default

to a start-up condition and attempt to detect handshake pulses from

the secondary.

If the secondary does not detect that the primary responds to

switching requests for 8 consecutive cycles, or if the secondary

detects that the primary is switching without cycle requests for 4 or

more consecutive cycles, the secondary controller will initiate a

second handshake sequence. This protection mode also prevents an

output overvoltage condition in the event that the primary is reset

while the secondary is still in control.

Wait and Listen

When the primary resumes switching after initial power-up recovery

from an input line voltage fault (UV or OV) or an auto-restart event, it

will assume control and require a successful handshake to relinquish

control to the secondary controller.

As an additional safety measure the primary will pause for an

auto-restart on-time period, t

(~82 ms), before switching. During

this “wait” time, the primary will “listen” for secondary requests. If it

sees two consecutive secondary requests, separated by ~30 ms, the

primary will infer secondary control and begin switching in slave

mode. If no pulses occurs during the t

“wait” period, the primary

will begin switching under primary control until handshake pulses are

received.

Audible Noise Reduction Engine

The InnoSwitch3-AQ features an active audible noise reduction mode

whereby the controller (via a “frequency skipping” mode of operation)

avoids the resonant band (where the mechanical structure of the

power supply is most likely to resonate − increasing noise amplitude)

between 7 kHz and 12 kHz - 143 ms and 83 ms. If a secondary

controller switch request occurs within this time window from the last

conduction cycle, the gate drive to the power MOSFET is inhibited.

Secondary Controller

As shown in the block diagram in Figure 4, the IC is powered by a

4.4 V (V

BPS

) regulator which is supplied by either VOUT or FWD. The

SECONDARY BYPASS pin is connected to an external decoupling

capacitor and fed internally from the regulator block.

The FORWARD pin also connects to the negative edge detection

block used for both handshaking and timing.

The mid-point of an external resistor divider network between the

OUTPUT VOLTAGE and SECONDARY GROUND pins is tied to the

FEEDBACK pin to regulate the output voltage. The internal voltage

comparator reference voltage is V

(1.265 V).

The external current sense resistor connected between ISENSE and

SECONDARY GROUND pins is used to regulate the output current in

constant current regulation mode.

Minimum Off-Time

The secondary controller initiates a cycle request using the inductive-

connection to the primary. The maximum frequency of secondary-

cycle requests is limited by a minimum cycle off-time of t

OFF(MIN)

. This

is in order to ensure that there is sufcient reset time after primary

conduction to deliver energy to the load.

Maximum Switching Frequency

The maximum switch-request frequency of the secondary controller

is f

SREQ

Frequency Soft-Start

At start-up the primary controller is limited to a maximum switching

frequency of f

and 75% of the maximum programmed current limit

at the switch-request frequency of 100 kHz.

The secondary controller temporarily inhibits the FEEDBACK short

protection threshold (V

FB(OFF)

) until the end of the soft-start (t

SS(R AMP)

)

time. After hand-shake is completed the secondary controller linearly

ramps up the switching frequency from f

to f

SREQ

over the t

SS(R AMP)

time period.

In the event of a short-circuit or overload at start-up, the device will

move directly into CC (constant-current) mode. The device will go

into auto-restart (AR), if the output voltage does not rise above the

FB(AR)

threshold before the expiration of the soft-start timer (t

SS(R AMP)

)

after handshake has occurred.

The secondary controller enables the FEEDBACK pin-short protection

mode (V

FB(OFF)

) at the end of the t

SS(R AMP)

time period. If the output

short maintains the FEEDBACK pin below the short-circuit threshold,

the secondary will stop requesting pulses triggering an auto-restart

cycle.

If the output voltage reaches regulation within the t

SS(R AMP)

time

period, the frequency ramp is immediately aborted and the secondary

controller is permitted to go full frequency. This will allow the

controller to maintain regulation in the event of a sudden transient

loading soon after regulation is achieved. The frequency ramp will

only be aborted if quasi-resonant-detection programming has already

occurred.

Maximum Secondary Inhibit Period

Secondary requests to initiate primary switching are inhibited to

maintain operation below maximum frequency and ensure minimum

off-time. Besides these constraints, secondary-cycle requests are

also inhibited during the “ON” time cycle of the primary switch (time

between the cycle request and detection of FORWARD pin falling

edge). The maximum time-out in the event that a FORWARD pin

falling edge is not detected after a cycle requested is ~30 ms.

Output Voltage Protection

In the event that the sensed voltage on the FEEDBACK pin is 2%

higher than the regulation threshold, a bleed current of ~2.5 mA

(3 mA max) is applied on the OUTPUT VOLTAGE pin (weak bleed).

This bleed current increases to ~200 mA (strong bleed) in the event

that the FEEDBACK pin voltage is raised beyond ~10% of the internal

FEEDBACK pin reference voltage. The current sink on the OUTPUT

VOLTAGE pin is intended to discharge the output voltage after

momentary overshoot events. The secondary does not relinquish

control to the primary during this mode of operation.

If the voltage on the FEEDBACK pin is sensed to be 20% higher than

the regulation threshold, a command is sent to the primary to either

latch-off or begin an auto-restart sequence (see Secondary Fault

Response in Feature Code Addendum). This integrated V

OUT

OVP can

be used independently from the primary sensed OVP or in conjunction.

FEEDBACK Pin Short Detection

If the sensed FEEDBACK pin voltage is below V

FB(OFF)

at start-up, the

secondary controller will complete the handshake to take control of

the primary complete t

SS(R AMP)

and will stop requesting cycles to initiate

auto-restart (no cycle requests made to primary for longer than t

AR(SK)

second triggers auto-restart).

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